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Accueil du site > Annuaire > Pages personnelles > Publications > Publications J.-R. Petit
par- 8 avril 2011 - ( maj : 8 avril 2011 )
Narcisi, B., Petit, J. R., Langone, A., & Stenni, B. (2016). A new Eemian record of Antarctic tephra layers retrieved from the Talos Dome ice core (Northern Victoria Land). Global And Planetary Change, 137, 69–78.
Abstract: Polar ice sheets are remarkable repositories of tephra layers. The Talos Dome ice core (72 degrees 49'5, 159 degrees 11'E), drilled at the edge of the East Antarctic Plateau, close to Late Quaternary volcanoes, offers considerable potential to extend the current tephra time-stratigraphic framework. A tephrochronological study was undertaken of the ice core sections related to the Last Interglacial and the transition to the subsequent glacial period. Thirteen macroscopically visible layers, interpreted to be related to primary deposition of fallout tephra, have been analysed for quantitative grain size and glass shard geochemistry. The layers, precisely framed within the climate (6180) record for the core, span in age from 111.6 +/- 1.9 to 123.3 +/- 22 ka. Coarse particle size suggests origin from regional sources. Indeed, the vast majority of the samples display an alkaline affinity and trachytic composition that are both typical geochemical features of rifting Antarctic volcanism. Using subtle differences in the geochemical signatures and the comparison with data from previous studies, a few layers are attributed to known coeval Mt. Melbourne eruptions. Another sample subset is consistent with derivation from The Pleiades and Mt. Rittmann volcanoes. One peculiar trachytic glass population appears to be related to activity of the more distant Marie Byrd land volcanoes. The newly detected tephras provide stratigraphic markers that could facilitate future synchronisation and dating of palaeoclimatic records. The Talos Dome tephra inventory also contributes significantly to the reconstruction of the Northern Victoria Land explosive volcanism, for which chronostratigraphic data for the last Interglacial temporal segment are poor. (C) 2015 Elsevier B.V. All rights reserved.
Tison, J. L., de Angelis, M., Littot, G., Wolff, E., Fischer, H., Hansson, M., et al. (2015). Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core. Cryosphere, 9(4), 1633–1648.
Abstract: An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (delta D-delta O-18(ice), delta O-18(atm), total air content, CO2, CH4, N2O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the "basal clean ice facies". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of debris from the ice sheet's substrate. We further discuss how the proposed mechanism is compatible with the other ice properties described. We conclude that the paleoclimatic signal is only marginally affected in terms of global ice properties at the bottom of EPICA Dome C, but that the timescale was considerably distorted by mechanical stretching of MIS20 due to the increasing influence of the subglacial topography, a process that might have started well above the bottom ice. A clear paleoclimatic signal can therefore not be inferred from the deeper part of the EPICA Dome C ice core. Our work suggests that the existence of a flat monotonic ice bedrock interface, extending for several times the ice thickness, would be a crucial factor in choosing a future "oldest ice" drilling location in Antarctica.
Wegner, A., Fischer, H., Delmonte, B., Petit, J. R., Erhardt, T., Ruth, U., et al. (2015). The role of seasonality of mineral dust concentration and size on glacial/interglacial dust changes in the EPICA Dronning Maud Land ice core. Journal Of Geophysical Research-Atmospheres, 120(19).
Abstract: We present a record of particulate dust concentration and size distribution in subannual resolution measured on the European Project for Ice Coring in Antarctica (EPICA) Dronning Maud Land (EDML) ice core drilled in the Atlantic sector of the East Antarctic plateau. The record reaches from present day back to the penultimate glacial until 145,000 years B.P. with subannual resolution from 60,000 years B.P. to the present. Mean dust concentrations are a factor of 46 higher during the glacial (similar to 850-4600 ng/mL) compared to the Holocene (similar to 16-112 ng/mL) with slightly smaller dust particles during the glacial compared to the Holocene and with an absolute minimum in the dust size at 16,000 years B.P. The changes in dust concentration are mainly attributed to changes in source conditions in southern South America. An increase in the modal value of the dust size suggests that at 16,000 years B.P. a major change in atmospheric circulation apparently allowed more direct transport of dust particles to the EDML drill site. We find a clear in-phase relation of the seasonal variation in dust mass concentration and dust size during the glacial (r(conc,size) = 0.8) but no clear phase relationship during the Holocene (0 < r(conc,size)< 0.4). With a simple conceptual 1-D model describing the transport of the dust to the ice sheet using the size as an indicator for transport intensity, we find that the effect of the changes in the seasonality of the source emission strength and the transport intensity on the dust decrease over Transition 1 can significantly contribute to the large decrease of dust concentration from the glacial to the Holocene.
Dumont, M., Brun, E., Picard, G., Michou, M., Libois, Q., Petit, J. R., et al. (2014). Contribution of light-absorbing impurities in snow to Greenland's darkening since 2009. Nature Geoscience, 7(7), 509–512.
Abstract: The surface energy balance and mass balance of the Greenland ice sheet depends on the albedo of snow, which governs the amount of solar energy that is absorbed. The observed decline of Greenland's albedo over the past decade(1-3) has been attributed to an enhanced growth of snow grains as a result of atmosphericwarming(1,2). Satellite observations show that, since 2009, albedo values even in springtime at high elevations have been lower than the 2003-2008 average. Here we show, using a numerical snow model, that the decrease in albedo cannot be attributed solely to grain growth enhancement. Instead, our analysis of remote sensing data indicates that the springtime darkening since 2009 stems from a widespread increase in the amount of light-absorbing impurities in snow, as well as in the atmosphere. We suggest that the transport of dust from snow-free areas in the Arctic that are experiencing earlier melting of seasonal snow cover(4) as the climate warms may be a contributing source of impurities. In our snow model simulations, a decrease in the albedo of fresh snow by 0.01 leads to a surface mass loss of 27 Gt yr(-1), which could induce an acceleration of Greenland's mass loss twice as large as over the past two decades(5). Future trends in light-absorbing impurities should therefore be considered in projections of Greenland mass loss.
Khodzher, T. V., Golobokova, L. P., Osipov, E. Y., Shibaev, Y. A., Lipenkov, V. Y., Osipova, O. P., et al. (2014). Spatial-temporal dynamics of chemical composition of surface snow in East Antarctica along the Progress station-Vostok station transect. Cryosphere, 8(3), 931–939.
Abstract: In January of 2008, during the 53rd Russian Antarctic Expedition, surface snow samples were taken from 13 shallow (0.7 to 1.5m depth) snow pits along the first tractor traverse from Progress to Vostok stations, East Antarctica. Sub-surface snow/firn layers are dated from 2.1 to 18 yr. The total length of the coast to inland traverse is more than 1280 km. Here we analysed spatial variability of concentrations of sulphate ions and elements and their fluxes in the snow deposited within the 2006-2008 time interval. Anions were analysed by high-performance liquid chromatography (HPLC), and the determination of selected metals, including Na, K, Mg, Ca and Al, was carried out by mass spectroscopy with atomization by induced coupled plasma (ICP-MS). Surface snow concentration records were examined for trends versus distance inland, elevation, accumulation rate and slope gradient. Na shows a significant positive correlation with accumulation rate, which decreases as distance from the sea and altitude increase. K, Ca and Mg concentrations do not show any significant relationship either with distance inland or with elevation. Maximal concentrations of these elements with a prominent Al peak are revealed in the middle part of the traverse (500-600 km from the coast). Analysis of element correlations and atmospheric circulation patterns allow us to suggest their terrestrial origin (e. g. aluminosilicates carried as a continental dust) from the Antarctic nunatak areas. Sulphate concentrations show no significant relationship with distance inland, elevation, slope gradient and accumulation rate. Non-sea salt secondary sulphate is the most important contribution to the total sulphate budget along the traverse. Sulphate of volcanic origin attributed to the Pinatubo eruption (1991) was revealed in the snow pit at 1276 km (depth 120-130 cm).
Waked, A., Favez, O., Alleman, L. Y., Piot, C., Petit, J. E., Delaunay, T., et al. (2014). Source apportionment of PM10 in a north-western Europe regional urban background site (Lens, France) using positive matrix factorization and including primary biogenic emissions. Atmospheric Chemistry And Physics, 14(7), 3325–3346.
Abstract: In this work, the source of ambient particulate matter (PM10) collected over a one-year period at an urban background site in Lens (France) was determined and investigated using a positive matrix factorization receptor model (US EPA PMF v3.0). In addition, a potential source contribution function (PSCF) was performed by means of the Hybrid Single-Particle Lagrangian Integrated Trajectory (Hysplit) v4.9 model to assess prevailing geographical origins of the identified sources. A selective iteration process was followed for the qualification of the more robust and meaningful PMF solution. Components measured and used in the PMF included inorganic and organic species: soluble ionic species, trace elements, elemental carbon (EC), sugar alcohols, sugar anhydride, and organic carbon (OC). The mean PM10 concentration measured from March 2011 to March 2012 was about 21 μg m(-3) with typically OM, nitrate and sulfate contributing to most of the mass and accounting respectively for 5.8, 4.5 and 2.3 μg m(-3) on a yearly basis. Accordingly, PMF outputs showed that the main emission sources were (in decreasing order of contribution) secondary inorganic aerosols (28% of the total PM10 mass), aged marine emissions (19 %), with probably predominant contribution of shipping activities, biomass burning (13 %), mineral dust (13 %), primary biogenic emissions (9 %), fresh sea salts (8 %), primary traffic emissions (6 %) and heavy oil combustion (4 %). Significant temporal variations were observed for most of the identified sources. In particular, biomass burning emissions were negligible in summer but responsible for about 25% of total PM10 and 50% of total OC in wintertime. Conversely, primary biogenic emissions were found to be negligible in winter but to represent about 20% of total PM10 and 40% of total OC in summer. The latter result calls for more investigations of primary biogenic aerosols using source apportionment studies, which quite usually disregard this type of source. This study further underlines the major influence of secondary processes during daily threshold exceedances. Finally, apparent discrepancies that could be generally observed between filter-based studies (such as the present one) and aerosol mass spectrometer-based PMF analyses (organic fractions) are also discussed.
Dahl-Jensen, D., Albert, M. R., Aldahan, A., Azuma, N., Balslev-Clausen, D., Baumgartner, M., et al. (2013). Eemian interglacial reconstructed from a Greenland folded ice core. Nature, 493(7433), 489–494.
Abstract: Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.
Delmonte, B., Baroni, C., Andersson, P. S., Narcisi, B., Salvatore, M. C., Petit, J. R., et al. (2013). Modern and Holocene aeolian dust variability from Tabs Dome (Northern Victoria Land) to the interior of the Antarctic ice sheet. Quaternary Science Reviews, 64, 76–89.
Abstract: High-elevation sites from the inner part of the East Antarctic plateau sample windborne dust representative of large portions of the Southern hemisphere, and are sensitive to long-range atmospheric transport conditions to polar areas. On the periphery of the ice sheet, conversely, the aeolian transport of particles from high-elevation ice-free areas can locally represent a relatively important additional input of dust to the atmosphere, and the interplay of atmospheric dynamics, dust transport and deposition is strictly related to the regional atmospheric circulation behaviour both at present-day and in the past. The understanding of the spatial extent where local sources can influence the mineral dust budget on the ice sheet is fundamental for understanding the atmospheric dust cycle in Antarctica and for the interpretation of the dust history in marginal glaciological settings. In this work we investigate the spatial variability of dust flux and provenance during modern (pre-industrial) and Holocene times along a transect connecting Tabs Dome to the internal sites of the Antarctic plateau and we extend the existing documentation of the isotopic (Sr-Nd) fingerprint of dust-sized sediments from Victoria Land source areas. Dust flux, grain size and isotopic composition show a marked variability between Tabs Dome, Mid Point, D4 and Dome C/Vostok, suggesting that local sources play an important role on the periphery of the ice sheet. Microscope observations reveal that background mineral aerosol in the TALDICE core is composed by a mixture of dust, volcanic particles and micrometric-sized fragments of diatoms, these latter representing a small but pervasive component of Antarctic sediments. A set of samples from Victoria Land, mostly consisting of regolith and glacial deposits from high-elevation areas, was collected specially for this work and the isotopic composition of the dust-sized fraction of samples was analyzed. Results reveal a close relationship with the parent lithologies, but direct comparison between source samples and firn/ice core dust is problematical because of the ubiquitous volcanic contribution to the environmental particulate input in the Tabs Dome area. The frequency of events potentially suitable for peripheral dust transport to Tabs Dome appears relatively high for present-day conditions, according to back trajectories calculations, and the related air flow pattern well-defined from a seasonal and spatial perspective. Also, as expected from palaeo-data, these events appear extremely uncommon for internal sites. (C) 2012 Elsevier Ltd. All rights reserved.
Legrand, M., Preunkert, S., Jourdain, B., Guilhermet, J., Fain, X., Alekhina, I., et al. (2013). Water-soluble organic carbon in snow and ice deposited at Alpine, Greenland, and Antarctic sites: a critical review of available data and their atmospheric relevance. Climate Of The Past, 9(5), 2195–2211.
Abstract: While it is now recognized that organic matter dominates the present-day atmospheric aerosol load over continents, its sources remain poorly known. The studies of organic species or organic fractions trapped in ice cores may help to overcome this lack of knowledge. Available data on the dissolved (or total) organic carbon (DOC or TOC) content of snow and ice often appear largely inconsistent, and, until now, no critical review has been conducted to understand the causes of these inconsistencies. To draw a more consistent picture of the organic carbon amount present in solid precipitation that accumulates on cold glaciers, we here review available data and, when needed, complete the data set with analyses of selected samples. The different data sets are then discussed by considering the age (modern versus pre-industrial, Holocene versus Last glacial Maximum) and type (surface snow, firn, or ice) of investigated samples, the deployed method, and the applied contamination control. Finally, the OC (DOC or TOC) levels of Antarctic, Greenland, and Alpine ice cores are compared and discussed with respect to natural (biomass burning, vegetation emissions) and anthropogenic sources (fossil fuel combustion) contributing to atmospheric OC aerosol.
Winkler, R., Landais, A., Risi, C., Baroni, M., Ekaykin, A., Jouzel, J., et al. (2013). Interannual variation of water isotopologues at Vostok indicates a contribution from stratospheric water vapor. Proceedings Of The National Academy Of Sciences Of The United States Of America, 110(44), 17674–17679.
Abstract: Combined measurements of water isotopologues of a snow pit at Vostok over the past 60 y reveal a unique signature that cannot be explained only by climatic features as usually done. Comparisons of the data using a general circulation model and a simpler isotopic distillation model reveal a stratospheric signature in the O-17-excess record at Vostok. Our data and theoretical considerations indicate that mass-independent fractionation imprints the isotopic signature of stratospheric water vapor, which may allow for a distinction between stratospheric and tropospheric influences at remote East Antarctic sites.
Albani, S., Delmonte, B., Maggi, V., Baroni, C., Petit, J. R., Stenni, B., et al. (2012). Interpreting last glacial to Holocene dust changes at Talos Dome (East Antarctica): implications for atmospheric variations from regional to hemispheric scales. Climate Of The Past, 8(2), 741–750.
Abstract: Central East Antarctic ice cores preserve stratigraphic records of mineral dust originating from remote sources in the Southern Hemisphere, and represent useful indicators of climatic variations on glacial-interglacial time scales. The peripheries of the East Antarctic Ice Sheet, where ice-free areas with the potential to emit dust exist, have been less explored from this point of view. Here, we present a new profile of dust deposition flux and grain size distributions from an ice core drilled at Talos Dome (TALDICE, Northern Victoria Land, East Antarctica), where there is a significant input of dust from proximal Antarctic ice-free areas. We analyze dust and stable water isotopes variations from the Last Glacial Maximum to the Late Holocene, and compare them to the EPICA Dome C profiles from central East Antarctica. The smaller glacial-interglacial variations at Talos Dome compared to Dome C and a distinctive decreasing trend during the Holocene characterize the TALDICE dust profile. By deciphering the composite dust signal from both remote and local sources, we show the potential of this combined proxy of source activity and atmospheric transport to give information on both regional and larger spatial scales. In particular, we show how a regional signal, which we relate to the deglaciation history of the Ross Sea embayment, can be superimposed to the broader scale glacial-interglacial variability that characterizes other Antarctic sites.
|Bulat, S. A., Alekhina, I. A., Marie, D., & Petit, J. R. (2012). Life Detection Strategy for Jovian Icy Moons: Lessons from Subglacial Lake Vostok Exploration. Paleontological Journal, 46(9), 1081.
Lanci, L., Delmonte, B., Kent, D. V., Maggi, V., Biscaye, P. E., & Petit, J. R. (2012). Magnetization of polar ice: a measurement of terrestrial dust and extraterrestrial fallout. Quaternary Science Reviews, 33, 20–31.
Abstract: Laboratory-induced remanent magnetization of polar ice constitutes a measurement of the magnetization carried by the ferromagnetic dust particles in the ice. This non-destructive technique provides a novel kind of information on the dust deposited on the surface of polar ice sheets. Measurements made on ice samples from Greenland (North GRIP ice core) and Antarctica (Vostok and EPICA-Dome C ice cores) allowed the recognition of a fraction of magnetic minerals in ice whose concentration and magnetic properties are directly related to that of insoluble dust. The source of this fraction of magnetic minerals thus appears closely related to terrestrial dust transport and deposition and its magnetic properties are informative of the dust provenance areas. The rock-magnetic properties of the dust may reflect distinct, changes of dust source areas from glacial to interglacial periods in agreement with and adding further information to the isotopic (Sr-87/Sr-86 and Nd-143/Nd-144) analyses. A second magnetic fraction consists of particles of nanometric size, which are superparamagnetic at freezer temperature and whose concentration is independent of the mass of aerosol dust found in the ice. The source of these nanometric-sized magnetic particles is ascribed to fallout of "meteoric smoke" and their concentration in ice was found to be compatible with the extraterrestrial fallout inferred from Ir concentrations. The diameter of the smoke particles as inferred from magnetic measurements is in the range of about 7-20 nm. (C) 2011 Elsevier Ltd. All rights reserved.
Narcisi, B., Petit, J. R., Delmonte, B., Scarchilli, C., & Stenni, B. (2012). A 16,000-yr tephra framework for the Antarctic ice sheet: a contribution from the new Tabs Dome core. Quaternary Science Reviews, 49, 52–63.
Abstract: A detailed tephra record for the last 16,000 years of the TALDICE ice core drilled at Tabs Dome (East Antarctica, Pacific/Ross Sea sector) is documented. Traces of 26 different explosive volcanic eruptions, dated by ice core chronology and framed within the climate (delta O-18) record for the core, have been identified. Glass major element composition and grain size data indicate that all prominent tephra layers derive from Antarctic volcanic activity and likely originated in proximal volcanoes of the Melbourne Volcanic Province (Northern Victoria Land). Two other Antarctic horizons may have originated from the more distant volcanoes of Mount Berlin (Marie Byrd Land, West Antarctica) and Mount Erebus (Ross Island, Southern Victoria Land). Moreover, based on glass-shard geochemistry and a 20-year analysis of atmospheric back trajectories suggesting ash transport from South America to the drilling site by the circumpolar westerly circulation, a few faint microtephra horizons are attributed to Andean volcanic activity. Two of these tephras are interpreted to be related to known Holocene explosive eruptions from the volcanoes of Mount Hudson and Mount Burney. Finally, by comparing compositional features in conjunction with age data, three TALDICE tephras have been successfully correlated with volcanic layers in other ice records of the Antarctic ice sheet. Altogether, our results expand the Antarctic tephrostratigraphic framework and add value to the prospects for continental-scale correlations between ice cores and Southern Hemisphere sediment archives. (C) 2012 Elsevier Ltd. All rights reserved.
Parrenin, F., Petit, J. R., Masson-Delmotte, V., Wolff, E., Basile-Doelsch, I., Jouzel, J., et al. (2012). Volcanic synchronisation between the EPICA Dome C and Vostok ice cores (Antarctica) 0-145 kyr BP. Climate Of The Past, 8(3), 1031–1045.
Abstract: This study aims at refining the synchronisation between the EPICA Dome C (EDC) and Vostok ice cores in the time interval 0-145 kyr BP by using the volcanic signatures. 102 common volcanic events were identified by using continuous electrical conductivity (ECM), di-electrical profiling (DEP) and sulfate measurements while trying to minimize the distortion of the glaciological chronologies. This is an update and a continuation of previous works performed over the 0-45 kyr interval that provided 56 tie points to the ice core chronologies (Udisti et al., 2004). This synchronisation will serve to establish Antarctic Ice Core Chronology 2012, the next synchronised Antarctic dating. A change of slope in the EDC-depth/Vostok-depth diagram is probably related to a change of accumulation regime as well as to a change of ice thickness upstream of the Lake Vostok, but we did not invoke any significant temporal change of surface accumulation at EDC relative to Vostok. No significant phase difference is detected between the EDC and Vostok isotopic records, but depth shifts between the Vostok 3G and 5G ice cores prevent from looking at this problem accurately. Three possible candidates for the Toba volcanic super-eruption similar to 73 kyr ago are suggested in the Vostok and EDC volcanic records. Neither the ECM, DEP nor the sulfate fingerprints for these 3 events are significantly larger than many others in the records.
Baroni, M., Bard, E., Petit, J. R., Magand, O., & Bourles, D. (2011). Volcanic and solar activity, and atmospheric circulation influences on cosmogenic (10)Be fallout at Vostok and Concordia (Antarctica) over the last 60 years. Geochimica Et Cosmochimica Acta, 75(22), 7132–7145.
Abstract: The cosmogenic nuclide beryllium-10 ((10)Be), recovered from ice cores, is often used to study solar activity on long time-scales. However, the (10)Be signal is also influenced by factors other than the Sun. To identify and quantify various contributions to the (10)Be signal, two Antarctic snow records from the Vostok and Concordia sites spanning the last 60 years were studied at a sub-annual resolution. Three factors that contribute to the (10)Be signal were identified. First, a significant period of approximately 11 yr that can be associated with the modulation of (10)Be production by solar activity was detected in both records. The solar imprint constitutes 20-35% of the variance within the total signal. The 11-yr (10)Be snow component was attenuated by a factor of similar to 0.5 and was delayed by similar to 1.4 yr compared to the (10)Be production expected within the polar atmosphere. The result could be interpreted as the composite response of a stratospheric (10)Be reservoir with an 11-yr modulation that was attenuated and delayed (with respect to (10)Be polar production) and to a tropospheric (10)Be reservoir with an 11-yr modulation that was not attenuated or delayed. Then, peaks in (10)Be concentrations that were similar to 66% and similar to 35% higher than the average concentration were observed during the stratospheric volcanic eruptions of Agung (in 1963) and Pinatubo (in 1991), respectively. In light of these new results, published (10)Be ice core records could be reinterpreted because spikes in (10)Be concentration appear at the time of several stratospheric events. The data indicate that stratospheric volcanic eruptions can impact (10)Be transport and deposition as a result of the roles played by the sedimentation of sulfate aerosols and the formation and rapid settling of polar stratospheric clouds (PSC). Also, an interannual variability of similar to 4 yr was determined in both (10)Be records, corresponding to similar to 26% of the variance within the signal at Vostok. As with species of marine origin (sodium), this 4-yr variability is interpreted as a tropospheric modulation. The 4-yr variability could be associated with atmospheric circulation associated with the coupled Southern Ocean ocean-atmosphere system. The results presented here, from sites within the high Antarctic plateau, open new possibilities for ice core dating over the last few centuries and for the reconstruction of past solar activity in relation to climate. (C) 2011 Elsevier Ltd. All rights reserved.
|Bilat, S., & Petit, J. - R. (2011). Vostok, Subglacial Lake. In M. Gargaud, R. Amils, J. Cernicharo Quintanilla, H. J. Cleaves II, W. M. Irvine, D. Pinti, et al. (Eds.), Encyclopedia of Astrobiology (pp. 1754–1758). Berlin Heidelberg: Springer-Verlag.
Bulat, S. A., Alekhina, I. A., Marie, D., Martins, J., & Petit, J. R. (2011). Searching for life in extreme environments relevant to Jovian's Europa: Lessons from subglacial ice studies at Lake Vostok (East Antarctica). Advances In Space Research, 48(4), 697–701.
Abstract: The objective was to estimate the genuine microbial content of ice samples from refrozen water (accretion ice) from the subglacial Lake Vostok (Antarctica) buried beneath the 4-km thick East Antarctic ice sheet. The samples were extracted by heavy deep ice drilling from 3659 m below the surface. High pressure, a low carbon and chemical content, isolation, complete darkness and the probable excess of oxygen in water for millions of years characterize this extreme environment. A decontamination protocol was first applied to samples selected for the absence of cracks to remove the outer part contaminated by handling and drilling fluid. Preliminary indications showed the accretion ice samples to be almost gas free with a low impurity content. Flow cytometry showed the very low unevenly distributed biomass while repeated microscopic observations were unsuccessful. We used strategies of Ancient DNA research that include establishing contaminant databases and criteria to validate the amplification results. To date, positive results that passed the artifacts and contaminant databases have been obtained for a pair of bacterial phylotypes only in accretion ice samples featured by some bedrock sediments. The phylotypes included the chemolithoautotrophic thermophile Hydrogenophilus thermoluteolus and one unclassified phylotype. Combined with geochemical and geophysical considerations, our results suggest the presence of a deep biosphere, possibly thriving within some active faults of the bedrock encircling the subglacial lake, where the temperature is as high as 50 degrees C and in situ hydrogen is probably present. Our approach indicates that the search for life in the subglacial Lake Vostok is constrained by a high probability of forward-contamination. Our strategy includes strict decontamination procedures, thorough tracking of contaminants at each step of the analysis and validation of the results along with geophysical and ecological considerations for the lake setting. This may serve to establish a guideline protocol for studying extraterrestrial ice samples. (C) 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.
Chuvochina, M. S., Alekhina, I. A., Normand, P., Petit, J. R., & Bulat, S. A. (2011). Three Events of Saharan Dust Deposition on the Mont Blanc Glacier Associated with Different Snow-Colonizing Bacterial Phylotypes. Microbiology, 80(1), 125–131.
Abstract: A preliminary study has demonstrated that the structure and species composition of microbial communities associated with events of dust deposition from the Sahara Desert to the Mont Blanc glacier varied considerably between samples originating from different time periods. Even for depositions within a single month, the dominant microbial phylotypes and candidates to colonize the snow pack were different. It is therefore highly probable that the structure and species composition of microbial communities will be different between any events of the kind. Apparently, the phenomenon does not correlate with the time the dust stays in the snow cover and consequently with the probable development of microorganisms in situ (three months, one month, and one week). The reasons for the variation may be the differences in conditions in the epicenter of a specific North African dust storm, as well as the history of the dust transport in the atmosphere. The candidates for joining the snow biome of Mont Blanc turned out to be different for three dust events (DEs) and belong to different, mostly minor, phylotypes related to Crossiella cryophilus (Actinobacteria), Devosia limi (alpha-Proteobacteria), Deinococcus claudionis (Deinococcus-Thermus), Anabaena sp. (Cyanobacteria), and Hymenobacter soli (Bacteroidetes). Since all these phylotypes have been previously isolated from soil samples of the Antarctic and Arctic, Arctic snow and ice, and the Alpine belt soils and sedimentary rocks of the glacier bed, they were tentatively ascribed to the group of snow pack colonizers.
Chuvochina, M. S., Marie, D., Chevaillier, S., Petit, J. R., Normand, P., Alekhina, I. A., et al. (2011). Community Variability of Bacteria in Alpine Snow (Mont Blanc) Containing Saharan Dust Deposition and Their Snow Colonisation Potential. Microbes And Environments, 26(3), 237–247.
Abstract: Microorganisms uplifted during dust storms survive long-range transport in the atmosphere and could colonize high-altitude snow. Bacterial communities in alpine snow on a Mont Blanc glacier, associated with four depositions of Saharan dust during the period 2006-2009, were studied using 16S rRNA gene sequencing and flow cytometry. Also, sand from the Tunisian Sahara, Saharan dust collected in Grenoble and Mont Blanc snow containing no Saharan dust (one sample of each) were analyzed. The bacterial community composition varied significantly in snow containing four dust depositions over a 3-year period. Out of 61 phylotypes recovered from dusty snow, only three phylotypes were detected in more than one sample. Overall, 15 phylotypes were recognized as potential snow colonizers. For snow samples, these phylotypes belonged to Actinobacteria, Proteobacteria and Cyanobacteria, while for Saharan sand/dust samples they belonged to Actinobacteria, Bacteroidetes, Deinococcus-Thermus and Proteobacteria. Thus, regardless of the time-scale, Saharan dust events can bring different microbiota with no common species set to alpine glaciers. This seems to be defined more by event peculiarities and aeolian transport conditions than by the bacterial load from the original dust source.
|Petit, J. R. (2011). The Vostok Venture: An Outcome of the Antarctic Treaty.
Preunkert, S., Legrand, M., Stricker, P., Bulat, S., Alekhina, I., Petit, J. R., et al. (2011). Quantification of Dissolved Organic Carbon at Very Low Levels in Natural Ice Samples by a UV-Induced Oxidation Method. Environ. Sci. Technol., 45(2), 673–678.
Abstract: The study of chemical impurities trapped in solid precipitation and accumulated in polar ice sheets and high-elevation, midlatitude cold glaciers over the last several hundreds of years provides a unique way to reconstruct our changing atmosphere from the preindustrial era to the present day. Numerous ice core studies of inorganic species have already evaluated the effects of growing anthropogenic emissions of SO2 or NOx on the chemical composition of the atmosphere in various regions of the world. While it was recently shown that organic species dominate the atmospheric aerosol mass, the contribution of anthropogenic emissions to their budget remains poorly understood. The study of organics in ice is at the infancy stage, and it still is difficult to draw a consistent picture of the organic content of polar ice from sparse available data. A UV oxidation method and IR quantification of CO2 was optimized to obtain measurements of dissolved organic carbon content as low as a few ppbC. Stringent working conditions were defined to prevent contamination during the cleaning of ice. Measurements in various ice cores corresponding to preindustrial times revealed dissolved organic carbon content of less than 10 ppbC in Antarctica and up to 75 ppbC in alpine ice.
Stenni, B., Buiron, D., Frezzotti, M., Albani, S., Barbante, C., Bard, E., et al. (2011). Expression of the bipolar see-saw in Antarctic climate records during the last deglaciation. Nat. Geosci., 4(1), 46–49.
Abstract: Ice-core records of climate from Greenland and Antarctica show asynchronous temperature variations on millennial timescales during the last glacial period(1). The warming during the transition from glacial to interglacial conditions was markedly different between the hemispheres, a pattern attributed to the thermal bipolar see-saw(2). However, a record from the Ross Sea sector of East Antarctica has been suggested to be synchronous with Northern Hemisphere climate change(3). Here we present a temperature record from the Talos Dome ice core, also located in the Ross Sea sector. We compare our record with ice-core analyses from Greenland, based on methane synchronization(4), and find clearly asynchronous temperature changes during the deglaciation. We also find distinct differences in Antarctic records, pointing to differences in the climate evolution of the Indo-Pacific and Atlantic sectors of Antarctica. In the Atlantic sector, we find that the rate of warming slowed between 16,000 and 14,500 years ago, parallel with the deceleration of the rise in atmospheric carbon dioxide concentrations and with a slight cooling over Greenland. In addition, our chronology supports the hypothesis that the cooling of the Antarctic Cold Reversal is synchronous with the Bolling-Allerod warming in the northern hemisphere 14,700 years ago(5).
Delmonte, B., Andersson, P. S., Schoberg, H., Hansson, M., Petit, J. R., Delmas, R., et al. (2010). Geographic provenance of aeolian dust in East Antarctica during Pleistocene glaciations: preliminary results from Talos Dome and comparison with East Antarctic and new Andean ice core data. Quat. Sci. Rev., 29(1-2), 256–264.
Abstract: The strontium and neodymium isotopic signature of aeolian mineral particles archived in polar ice cores provides constraints on the geographic provenance of dust and paleo-atmospheric circulation patterns. Data from different ice cores drilled in the centre of the East Antarctic plateau such as EPICA-Dome C (EDC, 75 degrees 06'S: 123 degrees 21'E) and Vostok (78 degrees 28'S, 106 degrees 48'E) suggested a uniform geographic provenance for dust during Pleistocene glacial ages, likely from southern South America (SSA). In this work the existing dust isotopic data from EDC have been integrated with new data from Marine Isotopic Stage (MIS) 14 (about 536 ka before 1950AD) and in parallel some first results are shown for the new TALDICE ice core which was drilled on the edge of the East Antarctic Plateau (Talos Dome, 72 degrees 48'S, 159 degrees 06'E) on the opposite side with respect to SSA. Interestingly, the isotopic composition of TALDICE glacial dust is remarkably similar to that obtained from glacial dust from sites located in the East Antarctic interior. Overall, the glacial dust isotopic field obtained from six East Antarctic ice cores matches well South American data obtained from target areas. In this respect, it was recently suggested that dust exported long-range from South America originates from Patagonia and from the Puna-Altiplano plateau. To test this hypothesis, we analysed the isotopic composition of dust from an ice core drilled on the Illimani glacier (Bolivia, 16 degrees 37'S, 67 degrees 46'W; 6350 m a.s.l.) in order to obtain information on the isotopic composition of regional mineral aerosol uplifted from the Altiplano area and likely transported over a long distance. Altogether, ice core and source data strongly suggest that the westerly circulation pattern allowed efficient transfer of dust from South America to the East Antarctic plateau under cold Quaternary climates. Isotopic data support the hypothesis of a possible mixing of dust from Patagonia and from the Puna-Altiplano plateau. Interestingly, high glacial dust inputs to Antarctica are characterized by less radiogenic Nd values, an issue suggesting that enhanced dust production in Patagonia was associated with the activation of a secondary source. Still, Patagonia was the most important supplier for dust to central East Antarctica during Quaternary glaciations. (C) 2009 Elsevier Ltd. All rights reserved.
Delmonte, B., Baroni, C., Andersson, P. S., Schoberg, H., Hansson, M., Aciego, S., et al. (2010). Aeolian dust in the Talos Dome ice core (East Antarctica, Pacific/Ross Sea sector): Victoria Land versus remote sources over the last two climate cycles. J. Quat. Sci., 25(8), 1327–1337.
Abstract: A new ice core (TALDICE) drilled at Tabs Dome (East Antarctica, Ross Sea sector) preserves a ca. 250 ka long record of palaeoclimate and atmospheric history. We investigate dust variability and provenance at the site during glacial periods and the Holocene through the Sr-Nd isotopic composition of ice core dust and potential source areas (PSA). We provide new isotopic data on dust sources from Victoria Land such as regoliths, glacial drifts, aeolian sands and beach deposits. Some of these sources are located at high altitude and are known to have been ice free throughout the Pleistocene. The major features of the TALDICE dust record are very similar to those from central East Antarctica. During glacial times, South America was the dominant dust supplier for Tabs Dome as well as for the entire East Antarctic plateau. Conversely, during the Holocene the principal input of mineral dust at Tabs Dome probably derives from proximal sources which are the ice-free areas of northern Victoria Land, located at similar altitude with respect to the drilling site. Atmospheric mobilisation of dust from these neighbouring areas and transport inland to Tabs Dome can be ultimately associated with advection of maritime air masses from the Pacific/Ross Sea region. Copyright (C) 2010 John Wiley & Sons, Ltd.
Keywords: Aeolian dust; Antarctica; ice cores; paleoclimate
Ekaykin, A. A., Lipenkov, V. Y., Petit, J. R., Johnsen, S., Jouzel, J., & Masson-Delmotte, V. (2010). Insights into hydrological regime of Lake Vostok from differential behavior of deuterium and oxygen-18 in accreted ice. J. Geophys. Res.-Oceans, 115, C05003.
Abstract: We use isotopic data (deuterium and oxygen-18) of the recently recovered deepest Vostok ice core section (down to 3650 m depth) to study processes leading to the formation of lake ice and the hydrological regime of subglacial Lake Vostok. The significant variability of the lake ice isotopic content implies fluctuations in physical conditions of ice formation (mainly, volume and/or growth rate of frazil ice crystals) as well as variations of the isotope composition of the freezing water. The latter implies a poor mixing of the source waters (glacier melt and hydrothermal water) with the water of the main lake body. Poor mixing within the lake may have important consequences for the lake's chemical and gas balance and, particularly, for its microbiological content. A poorly mixed lake may provide ecological niches where microbial life can hide from high oxygen concentrations likely typical for the lake. We also show that the isotopic content of the main lake's input (meltwater) significantly differs from that of the output (lake ice), which can be explained by the contribution of an additional (hydrothermal) source. This latter conclusion is supported by the observed noncovariant behavior of deuterium and oxygen-18 isotopes in the lake ice.
Gabrielli, P., Wegner, A., Petit, J. R., Delmonte, B., De Deckker, P., Gaspari, V., et al. (2010). A major glacial-interglacial change in aeolian dust composition inferred from Rare Earth Elements in Antarctic ice. Quat. Sci. Rev., 29(1-2), 265–273.
Abstract: We present the first Rare Earth Elements (REE) concentration record determined in 294 sections of an Antarctic ice core (EPICA Dome C), covering a period from 2.9 to 33.7 kyr BR REE allow a detailed quantitative evaluation of aeolian dust composition because of the large number of variables (i.e. 14 elements). REE concentrations match the particulate dust concentration profile over this period and show a homogeneous crustal-like composition during the last glacial stage (LGS), with only a slight enrichment in medium REE. This signature is consistent with the persistent fallout of a mixture of dust from heterogeneous sources located in different areas or within the same region (e.g. South America). Starting at similar to 15 kyr BP, there was a major change in dust composition, the variable character of which persisted throughout the Holocene. This varying signature may highlight the alternation of single dust contributions from different sources during the Holocene. We observe that the frequent changes in REE composition at the onset of the Holocene (10-13.5 kyr BP) are linked to dust size and in turn to wind strength and/or the path of the atmospheric trajectory. This may indicate that atmospheric circulation dictated the composition of the dust fallout to East Antarctica at that time. Although the dust concentrations remained fairly low, a notable return towards more glacial dust characteristics is recorded between 7.5 and 8.3 kyr BP. This happened concomitantly with a widespread cold event around 8 kyr BP that was 400-600 years long and suggests a moderate reactivation of the dust emission from the same potential source areas of the LGS. Published by Elsevier Ltd.
|Jean-Baptiste, P., Fourre, E., Petit, J. R., Bulat, S., Alekina, I., & Lipenkov, V. (2010). Helium isotope in the accreted ice of subglacial lake Vostok (Antarctica). Geochim. Cosmochim. Acta, 74(12), A461.
Krinner, G., Petit, J. R., & Delmonte, B. (2010). Altitude of atmospheric tracer transport towards Antarctica in present and glacial climate. Quat. Sci. Rev., 29(1-2), 274–284.
Abstract: The preferential altitude of transport of continental tracers towards Antarctica under present and Last Glacial Maximum (21 kyr BP) conditions is analysed using an atmospheric general circulation model with idealized tracers which are emitted at the surface of Australia and South America. It is shown that the difference between the preferential transport altitude of Australian and South American tracers is similar in glacial and interglacial climates. Australian tracers arriving in Antarctica are consistently transported at higher altitudes than tracers emitted in South America. The frequency of low-level transport is stronger at the LGM than at present, reflecting a more vigorous atmospheric circulation at the LGM as a consequence of increased baroclinicity. While the spatial patterns of the total tracer concentrations at the Antarctic surface differ for Australian and South American tracers, with the regions of maximum surface concentration being located to the south-east of the respective tracer sources, the spatial distribution of the part advected via upper atmospheric levels is very similar for the Australian and South American tracers, with a maximum over Queen Maud Land. The simulated changes in transport characteristics cannot explain observed glacial to interglacial variations of dust size spectra which have been interpreted as indicators of the relative intensity of upper and lower level atmospheric dust transport to Antarctica. (C) 2009 Elsevier Ltd. All rights reserved.
Lemieux-Dudon, B., Blayo, E., Petit, J. R., Waelbroeck, C., Svensson, A., Ritz, C., et al. (2010). Consistent dating for Antarctic and Greenland ice cores. Quat. Sci. Rev., 29(1-2), 8–20.
Abstract: We are hereby presenting a new dating method based on inverse techniques, which aims at calculating consistent gas and ice chronologies for several ice cores. The proposed method yields new dating scenarios simultaneously for several cores by making a compromise between the chronological information brought by glaciological modeling (i.e.. ice flow model, firn densification model, accumulation rate model), and by gas and ice stratigraphic constraints. This method enables us to gather widespread chronological information and to use regional or global markers (i.e., methane, volcanic sulfate. Beryllium-10, tephra layers, etc.) to link the core chronologies stratigraphically. Confidence intervals of the new dating scenarios can be calculated thanks to the probabilistic formulation of the new method, which takes into account both modeling and data uncertainties. We apply this method simultaneously to one Greenland (NGRIP) and three Antarctic (EPICA Dome C, EPICA Dronning Maud Land, and Vostok) ices cores, and refine existent chronologies. Our results show that consistent ice and gas chronologies can be derived for depth intervals that are well-constrained by relevant glaciological data. In particular, we propose new and consistent dating of the last deglaciation for Greenland and Antarctic ice and gas records. (C) 2009 Elsevier Ltd. All rights reserved.
Narcisi, B., Petit, J. R., & Chappellaz, J. (2010). A 70 ka record of explosive eruptions from the TALDICE ice core (Talos Dome, East Antarctic plateau). J. Quat. Sci., 25(6), 844–849.
Abstract: The new Antarctic TALDICE ice core (72 degrees 49' S, 159 degrees 11' E, 1620 m depth), containing abundant primary tephras, provides the opportunity to elucidate the late Quaternary volcanic history of the south polar region, as well as to broaden the East Antarctic tephrostratigraphic framework. Here grain size and glass compositional data for representative tephra layers from the last 70 ka core section are used for source identification. Results point to origin of layers from centres of the Melbourne Volcanic Province (McMurdo Volcanic Group), located similar to 250 km from the coring site. Occurrence of tephra layers within the ice core record suggests that explosive activity in the identified source was not constant over the considered period, with a minimum of activity between 20 and 35 ka, and increased activity back to 65 ka. In addition to palaeovolcanic implications, the TALDICE tephra layers offer prospects for firm correlations between diverse widely separated palaeoarchives and for accurate dating of the Antarctic climatic record. Copyright (C) 2010 John Wiley & Sons, Ltd.
Keywords: Eastern Antarctic plateau; major element geochemistry; polar ice cores; tephra layers; volcanic stratigraphy
Narcisi, B., Petit, J. R., & Delmonte, B. (2010). Extended East Antarctic ice-core tephrostratigraphy. Quat. Sci. Rev., 29(1-2), 21–27.
Abstract: Three new tephra layers have been identified and analysed in the deeper sections of the EPICA Dome C (EDC) and Vostok ice record (East Antarctic plateau): one from EDC (358 ka old), originated from an Antarctic volcano, and two from Vostok (406 and 414 ka old, respectively), which are related to Antarctic volcanoes and to southern Andes and/or Antarctic Peninsula centres, respectively. These layers represent the oldest tephra-bearing events so far detected in deep polar ice cores and extend the regional tephrostratigraphic framework back to the fourth climatic cycle. Although differences between the drill sites are observed, new and previously published tephra data from deep ice cores broadly confirm that the clockwise circum-Antarctic atmospheric circulation played a major role in the dispersal of volcanic dust onto the plateau. While the last 220-ka core sections contain about a dozen visible tephra fall layers, the ice representing the time interval from 220 ka back to 800 ka (i.e. the EDC core bottom) is almost devoid of observed tephras. Although it is possible that the reduced frequency is an observational artefact, the observed pattern could alternatively reflect late Quaternary activity fluctuations of sources for tephra in the East Antarctic plateau, particularly South Sandwich Islands, with enhanced explosive activity in the last two glacial cycles with respect to previous periods. (C) 2009 Elsevier Ltd. All rights reserved.
Xu, J. Z., Hou, S. G., Qin, D. H., Kaspari, S., Mayewski, P. A., Petit, J. R., et al. (2010). A 108.83-m ice-core record of atmospheric dust deposition at Mt. Qomolangma (Everest), Central Himalaya. Quat. Res., 73(1), 33–38.
Abstract: The central Himalaya can be regarded as an ideal site for developing a long-term ice core dust record to reflect the environmental signals from regional to semi-hemispheric scales. Here we present a dust record from segments of a 108.83-m ice core recovered from the East Rongbuk (ER) Glacier (27 degrees 59'N, 86 degrees 55'E; 6518 in a.s.l.) on the northeast slope of Mt. Qomolangma (Everest) in the central Himalaya, covering the period AD 600-1960. Due to rapidly layer thinning and coarse sampling, we primarily discuss the changes in the dust record since AD 1500 in this paper. Results show a significant positive relationship between the dust concentration and reconstructed air temperatures during this period, suggesting a likely cold-humid and warm-dry climatic pattern in the dust source regions, namely Central Asia. This is associated with the variability in the strength of the westerlies and its corresponding precipitation. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved.
Keywords: Dust; Ice core; Qomolangma (Everest); Himalaya
|Bulat, S., Alekhin, I., & Petit, J. R. (2009). Life detection strategy for subglacial Lake Vostok, Antarctica: Lessons for Jovian moon Europa. Geochim. Cosmochim. Acta, 73(13), A173.
|Bulat, S. A., Alekhina, I. A., Lipenkov, V. Y., Lukin, V. V., Marie, D., & Petit, J. R. (2009). Cell concentrations of microorganisms in glacial and lake ice of the Vostok ice core, East Antarctica. Microbiology, 78(6), 808–810.
Debret, M., Sebag, D., Crosta, X., Massei, N., Petit, J. R., Chapron, E., et al. (2009). Evidence from wavelet analysis for a mid-Holocene transition in global climate forcing. Quat. Sci. Rev., 28(25-26), 2675–2688.
Abstract: A strong mid-Holocene transition has been identified by wavelet analyses in several sea ice cover records from the circum-Antarctic area, ice core records (Taylor dome, Byrd) and tropical marine records. The results are compared with those previously published in a synthesis of North Atlantic records and with 4 new records from the Norwegian and Icelandic seas and from a coastal site in Ireland. These new records confirm the previous pattern for the North Atlantic area, extend this pattern nearly to the Arctic Circle, and include a continental record. We further tested the possibility of extending this scheme using continental records from South America. The Holocene pattern proposed here confirms the importance of external forcing during the Early Holocene (solar activity: 1000 years cyclicity and 2500 years during the entire Holocene), even if the signal is disturbed by meltwater fluxes. The second part of the Holocene is then marked by the gradual appearance of internal forcing (thermohaline circulation around 1500 years), associated with a stabilisation of the signal. Coupling between ocean and atmosphere seems to play a fundamental role in the observed frequencies which vary accordingly in the Atlantic, circum-Antarctic and Pacific areas. The North Atlantic area seems to be the instigator of thermohaline circulation as shown by its sensitivity to meltwater discharges during the Early Holocene, even though each sector is independent with regards to its frequency content (around 1600 years for Atlantic Area; around 1250 years for Antarctica). The Holocene methane pattern, still under debate [Ruddiman, W.F., 2003a. Orbital insolation, ice volume and greenhouse gases. Quaternary Science Review 22,1597-1629; Ruddiman, W.F., 2003b. The anthropogenic greenhouse era began thousands of years ago. Climatic Change 61, 261-293]. could be explained by a more efficient thermohaline circulation around the mid-Holocene with an anthropogenic effect initiated at similar to 2500 BP as shown by the inter-hemispheric gradient. (C) 2009 Elsevier Ltd. All rights reserved.
Gabrielli, P., Planchon, F., Barbante, C., Boutron, C. F., Petit, J. R., Bulat, S., et al. (2009). Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica. Geochim. Cosmochim. Acta, 73(20), 5959–5974.
Abstract: This paper reports the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial. our ice). REE concentrations ranged between 0.8-56 pg g(-1) for Ce and 0.0035-0.24 pg g(-1) for Lu in glacier ice, and between <0.1-24 pg g(-1) for Ce and < 0.0004-0.02 pg g(-1) for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC(1); characterized by visible aggregates containing a mixture of very. ne terrigenous particles) and in the deeper accreted ice (AC(2); characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC(1) are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC(1) formation. Interestingly, if the LREE enrichment found in AC(1) was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok. Published by Elsevier Ltd.
Gonzalez-Toril, E., Amils, R., Delmas, R. J., Petit, J. R., Komarek, J., & Elster, J. (2009). Bacterial diversity of autotrophic enriched cultures from remote, glacial Antarctic, Alpine and Andean aerosol, snow and soil samples. Biogeosciences, 6(1), 33–44.
Abstract: Four different communities and one culture of autotrophic microbial assemblages were obtained by incubation of samples collected from high elevation snow in the Alps (Mt. Blanc area) and the Andes (Nevado Illimani summit, Bolivia), from Antarctic aerosol (French station Dumont d'Urville) and a maritime Antarctic soil (King George Island, South Shetlands, Uruguay Station Artigas), in a minimal mineral (oligotrophic) media. Molecular analysis of more than 200 16S rRNA gene sequences showed that all cultured cells belong to the Bacteria domain. Phylogenetic comparison with the currently available rDNA database allowed sequences belonging to Proteobacteria (Alpha-, Beta- and Gamma-proteobacteria), Actinobacteria and Bacteroidetes phyla to be identified. The Andes snow culture was the richest in bacterial diversity (eight microorganisms identified) and the marine Antarctic soil the poorest (only one). Snow samples from Col du Midi (Alps) and the Andes shared the highest number of identified microorganisms (Agrobacterium, Limnobacter, Aquiflexus and two uncultured Alphaproteobacteria clones). These two sampling sites also shared four sequences with the Antarctic aerosol sample (Limnobacter, Pseudonocardia and an uncultured Alphaproteobacteria clone). The only microorganism identified in the Antarctica soil (Brevundimonas sp.) was also detected in the Antarctic aerosol. Most of the identified microorganisms had been detected previously in cold environments, marine sediments soils and rocks. Air current dispersal is the best model to explain the presence of very specific microorganisms, like those identified in this work, in environments very distant and very different from each other.
Petit, J. R., & Delmonte, B. (2009). A model for large glacial-interglacial climate-induced changes in dust and sea salt concentrations in deep ice cores (central Antarctica): palaeoclimatic implications and prospects for refining ice core chronologies. Tellus Ser. B-Chem. Phys. Meteorol., 61(5), 768–790.
Abstract: A semi-empirical model has been developed to reproduce glacial-interglacial changes of continental dust and marine sodium concentrations (factor of similar to 50 and similar to 5, respectively) observed in inland Antarctic ice cores. The model uses conceptual pathways of aerosols within the high troposphere; assumes the dry deposition of impurities on the Antarctic surface; uses estimates of aerosol transit times taken independent of climate; assumes a temperature-dependent removal process during aerosol pathways from the mid-latitudes. The model is fitted to the data over the last four climate cycles from Vostok and EPICA Dome C Antarctic sites. As temperature is cooling, the aerosol response suggests different modes of climate couplings between latitudes, which can be continuous or below temperature thresholds for sodium and dust, respectively. The model estimates a southern South America dust source activity two to three times higher for glacial periods than for the Holocene and a glacial temperature over the Southern Ocean 3-5 degrees C cooler. Both estimates appear consistent with independent observations. After removal of temperature effects, dust and sodium residuals for both sites show orbital frequencies in opposite phase at the precession timescale. Such long-term insolation-related modulation of terrestrial and marine aerosol input, could provide a chemical pacemaker useful for refining ice core chronologies.
|Alekhina, I., Marie, D., Petit, J. R., Lukin, V., Zubkov, V., & Bulat, S. (2008). Hydrocarbon rich extreme econiche established in the deepest ice borehole at Vostok, East Antarctica. Int. J. Astrobiol., 7(1), 84.
|Bulat, S., Alekhina, I., Lipenkov, V., Lukin, V., Marie, D., Lavire, C., et al. (2008). Microbial life in extreme subglacial Antarctic lake environments: Lake Vostok. Int. J. Astrobiol., 7(1), 69.
Delmonte, B., Andersson, P. S., Hansson, M., Schoberg, H., Petit, J. R., Basile-Doelsch, I., et al. (2008). Aeolian dust in East Antarctica (EPICA-Dome C and Vostok): Provenance during glacial ages over the last 800 kyr. Geophys. Res. Lett., 35(7), 6 pp.
Abstract: Aeolian mineral dust archived in Antarctic ice cores represents a key proxy for Quaternary climate evolution. The longest and most detailed dust and climate sequences from polar ice are provided today by the Vostok and by the EPICA-Dome C (EDC) ice cores. Here we investigate the geographic provenance of dust windborne to East Antarctica during Early and Middle Pleistocene glacial ages using strontium and neodymium isotopes as tracers. The isotopic signature of Antarctic dust points towards a dominant South American origin during Marine Isotopic Stage (MIS) 8, 10, 12, and back to MIS 16 and 20 as deduced from EDC core. Data provide evidence for a persistent overall westerly circulation pattern allowing efficient transfer of dust from South America to the interior of Antarctica over the last 800 kyr. Some small but significant dissimilarity between old and recent glacial ages suggests a slightly reduced Patagonian contribution during ancient glaciations.
|Engrand, C., Narcisi, B., Petit, J. R., Dobrica, E., Duprat, J., Vaubaillon, J., et al. (2008). More clues about the EPICA-Dome C extraterrestrial events. Meteorit. Planet. Sci., 43(7), A41.
Lambert, F., Delmonte, B., Petit, J. R., Bigler, M., Kaufmann, P. R., Hutterli, M. A., et al. (2008). Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core. Nature, 452(7187), 616–619.
Abstract: Dust can affect the radiative balance of the atmosphere by absorbing or reflecting incoming solar radiation(1); it can also be a source of micronutrients, such as iron, to the ocean(2). It has been suggested that production, transport and deposition of dust is influenced by climatic changes on glacial-interglacial timescales(3-6). Here we present a high- resolution record of aeolian dust from the EPICA Dome C ice core in East Antarctica, which provides an undisturbed climate sequence over the past eight climatic cycles(7,8). We find that there is a significant correlation between dust flux and temperature records during glacial periods that is absent during interglacial periods. Our data suggest that dust flux is increasingly correlated with Antarctic temperature as the climate becomes colder. We interpret this as progressive coupling of the climates of Antarctic and lower latitudes. Limited changes in glacial-interglacial atmospheric transport time(4,9,10) suggest that the sources and lifetime of dust are the main factors controlling the high glacial dust input. We propose that the observed similar to 25-fold increase in glacial dust flux over all eight glacial periods can be attributed to a strengthening of South American dust sources, together with a longer lifetime for atmospheric dust particles in the upper troposphere resulting from a reduced hydrological cycle during the ice ages.
Lanci, L., Delmonte, B., Maggi, V., Petit, J. R., & Kent, D. V. (2008). Ice magnetization in the EPICA-Dome C ice core: Implication for dust sources during glacial and interglacial periods. J. Geophys. Res.-Atmos., 113(D14), 7 pp.
Abstract: Isothermal remanent magnetization and insoluble dust content of ice samples from EPICA-Dome C ice core were measured to characterize the magnetic properties of atmospheric dust. Despite the larger concentration of dust aerosol during glacial stages, the magnetization of the dust fraction was found to be higher during interglacials and exhibits a larger variability. Changes in magnetic mineralogy of aerosol dust in ice from different climatic stages were also characterized using coercivity of remanence. Variations of magnetic properties of dust from glacial to interglacial stages indicate changes in dust provenance, in agreement with previous results based on geochemical analysis. However, the extremely large magnetizations of some interglacial samples also suggest that episodical eolian deposition from highly magnetic deposits occurred during interglacial periods.
Marino, F., Castellano, E., Ceccato, D., De Deckker, P., Delmonte, B., Ghermandi, G., et al. (2008). Defining the geochemical composition of the EPICA Dome C ice core dust during the last glacial-interglacial cycle. Geochem. Geophys. Geosyst., 9, 11 pp.
Abstract: The major element composition of the insoluble, windborne long-range dust archived in the European Project for Ice Coring in Antarctica Dome C ice core has been determined by Particle Induced X-ray Emission analyses. The geochemistry of dust from the last glacial maximum (LGM) and from the Holocene is discussed in terms of past environmental changes, throughout the last climatic cycle. Antarctic dust from glacial and interglacial climate clearly reveals different geochemical compositions. The weathered crustal-like signature of LGM dust is characterized by a low compositional variability, suggesting a dominant source under the glacial regime. The close correspondence between the major element composition of Antarctic glacial dust and the composition of southern South American sediments supports the hypothesis of a dominant role of this area as major dust supplier during cold conditions. Conversely, the major element composition of Holocene dust displays high variability and high Al content on average. This implies that an additional source could also play some role. Comparison with size-selected sediments suggests that a contribution from Australia is likely during warm times, when a reduced glacial erosion decreases the primary dust production and a more intense hydrological cycle and larger vegetation cover inactivates dust mobility in a large part of southern South America, weakening its contribution as a massive dust supplier to Antarctica.
Keywords: ice cores; aeolian dust; major elements; dust sources; paleoclimate; Antarctica
Masson-Delmotte, V., Hou, S., Ekaykin, A., Jouzel, J., Aristarain, A., Bernardo, R. T., et al. (2008). A review of Antarctic surface snow isotopic composition: Observations, atmospheric circulation, and isotopic modeling. J. Clim., 21(13), 3359–3387.
Abstract: A database of surface Antarctic snow isotopic composition is constructed using available measurements, with an estimate of data quality and local variability. Although more than 1000 locations are documented, the spatial coverage remains uneven with a majority of sites located in specific areas of East Antarctica. The database is used to analyze the spatial variations in snow isotopic composition with respect to geographical characteristics ( elevation, distance to the coast) and climatic features ( temperature, accumulation) and with a focus on deuterium excess. The capacity of theoretical isotopic, regional, and general circulation atmospheric models ( including "isotopic" models) to reproduce the observed features and assess the role of moisture advection in spatial deuterium excess fluctuations is analyzed.
Ruth, U., Barbante, C., Bigler, M., Delmonte, B., Fischer, H., Gabrielli, P., et al. (2008). Proxies and measurement techniques for mineral dust in antarctic ice cores. Environ. Sci. Technol., 42(15), 5675–5681.
Abstract: To improve quantitative interpretation of ice core aeolian dust records, a systematic methodological comparison was made. This involved methods for water-insoluble particle counting (Coulter counter and laser-sensing particle detector), soluble ion analysis (ion chromatography and continuous flow analysis), elemental analysis (inductively coupled plasma mass spectroscopy at pH 1 and after full acid digestion), and water insoluble elemental analysis (proton induced X-ray emission). Antarctic ice core samples covering the last deglaciation from the EPICA Dome C (EDC) and the EPICA Dronning Maud Land (EDML) cores were used. All methods correlate very well among each other, but the ratios of glacial age to Holocene concentrations, which are typically a factor similar to 100, differ between the methods by up to a factor of 2 with insoluble particles showing the largest variability. The recovery of ICP-MS measurements depends on the digestion method and is different for different elements and during different climatic periods. EDC and EDML samples have similar dust composition, which suggests a common dust source or a common mixture of sources for the two sites. The analyzed samples further reveal a change of dust composition during the last deglaciation.
Alekhina, I. A., Marie, D., Petit, J. R., Lukin, V. V., Zubkov, V. M., & Bulat, S. A. (2007). Molecular analysis of bacterial diversity in kerosene-based drilling fluid from the deep ice borehole at Vostok, East Antarctica. FEMS Microbiol. Ecol., 59(2), 289–299.
Abstract: Decontamination of ice cores is a critical issue in phylogenetic studies of glacial ice and subglacial lakes. At the Vostok drill site, a total of 3650 m of ice core have now been obtained from the East Antarctic ice sheet. The ice core surface is coated with a hard-to-remove film of impure drilling fluid comprising a mixture of aliphatic and aromatic hydrocarbons and foranes. In the present study we used 16S rRNA gene sequencing to analyze the bacterial content of the Vostok drilling fluid sampled from four depths in the borehole. Six phylotypes were identified in three of four samples studied. The two dominant phylotypes recovered from the deepest (3400 and 3600 m) and comparatively warm (-10 degrees C and -6 degrees C, respectively) borehole horizons were from within the genus Sphingomonas, a well-known degrader of polyaromatic hydrocarbons. The remaining phylotypes encountered in all samples proved to be human- or soil-associated bacteria and were presumed to be drilling fluid contaminants of rare occurrence. The results obtained indicate the persistence of bacteria in extremely cold, hydrocarbon-rich environments. They show the potential for contamination of ice and subglacial water samples during lake exploration, and the need to develop a microbiological database of drilling fluid findings.
Keywords: drilling fluid; Lake Vostok; contamination; Sphingomonas; Antarctica; extremophiles
Debret, M., Bout-Roumazeilles, V., Grousset, F., Desmet, M., McManus, J. F., Massei, N., et al. (2007). The origin of the 1500-year climate cycles in Holocene North-Atlantic records. Clim. Past., 3(4), 569–575.
Abstract: Since the first suggestion of 1500-year cycles in the advance and retreat of glaciers (Denton and Karlen, 1973), many studies have uncovered evidence of repeated climate oscillations of 2500, 1500, and 1000 years. During last glacial period, natural climate cycles of 1500 years appear to be persistent (Bond and Lotti, 1995) and remarkably regular (Mayewski et al., 1997; Rahmstorf, 2003), yet the origin of this pacing during the Holocene remains a mystery (Rahmstorf, 2003), making it one of the outstanding puzzles of climate variability. Solar variability is often considered likely to be responsible for such cyclicities, but the evidence for solar forcing is difficult to evaluate within available data series due to the shortcomings of conventional time-series analyses. However, the wavelets analysis method is appropriate when considering non-stationary variability. Here we show by the use of wavelets analysis that it is possible to distinguish solar forcing of 1000- and 2500- year oscillations from oceanic forcing of 1500-year cycles. Using this method, the relative contribution of solar-related and ocean-related climate influences can be distinguished throughout the 10 000 yr Holocene intervals since the last ice age. These results reveal that the 1500-year climate cycles are linked with the oceanic circulation and not with variations in solar output as previously argued (Bond et al., 2001). In this light, previously studied marine sediment (Bianchi and McCave, 1999; Chapman and Shackleton, 2000; Giraudeau et al., 2000), ice core (O'Brien et al., 1995; Vonmoos et al., 2006) and dust records (Jackson et al., 2005) can be seen to contain the evidence of combined forcing mechanisms, whose relative influences varied during the course of the Holocene. Circum-Atlantic climate records cannot be explained exclusively by solar forcing, but require changes in ocean circulation, as suggested previously (Broecker et al., 2001; McManus et al., 1999).
Narcisi, B., Petit, J. R., & Engrand, C. (2007). First discovery of meteoritic events in deep Antarctic (EPICA-Dome C) ice cores. Geophys. Res. Lett., 34(15), 5 pp.
Abstract: Two distinct dust layers in the EPICA-Dome C ice core (75 degrees 06'S, 123 degrees 21'E, East Antarctic Plateau) have been shown to relate to individual meteoritic events. Particles forming these layers, investigated by electron microprobe, show peculiar textural, mineralogical and geochemical features and closely resemble extraterrestrial debris in deep-sea sediments and polar caps. Preliminary estimates of cosmic debris input at the studied layers, obtained from Coulter Counter measurements, are 4-5 orders of magnitude greater than the yearly micrometeorite flux in East Antarctic snow and ice. The cosmic events are accurately dated through glaciological models at 434 +/- 6 and 481 +/- 6 ka, respectively and are located in the core climatic stratigraphy near the "Mid-Brunhes Event''. This is the first report of well-dated cosmic horizons in deep Antarctic ice cores. It significantly improves the extraterrestrial record of Antarctica and opens new correlation perspectives between long climatic records of the South polar region.
Parrenin, F., Barnola, J. M., Beer, J., Blunier, T., Castellano, E., Chappellaz, J., et al. (2007). The EDC3 chronology for the EPICA dome C ice core. Clim. Past., 3(3), 485–497.
Abstract: The EPICA (European Project for Ice Coring in Antarctica) Dome C drilling in East Antarctica has now been completed to a depth of 3260 m, at only a few meters above bedrock. Here we present the new EDC3 chronology, which is based on the use of 1) a snow accumulation and mechanical flow model, and 2) a set of independent age markers along the core. These are obtained by pattern matching of recorded parameters to either absolutely dated paleoclimatic records, or to insolation variations. We show that this new time scale is in excellent agreement with the Dome Fuji and Vostok ice core time scales back to 100 kyr within 1 kyr. Discrepancies larger than 3 kyr arise during MIS 5.4, 5.5 and 6, which points to anomalies in either snow accumulation or mechanical flow during these time periods. We estimate that EDC3 gives accurate event durations within 20% (2 sigma) back to MIS11 and accurate absolute ages with a maximum uncertainty of 6 kyr back to 800 kyr.
|Xu, J. Z., Hou, S. G., Ren, J. W., & Petit, J. R. (2007). Insoluble dust in a new core from Dome Argus, central East Antarctica. J. Glaciol., 53(180), 154–156.
Barbante, C., Barnola, J. M., Becagli, S., Beer, J., Bigler, M., Boutron, C., et al. (2006). One-to-one coupling of glacial climate variability in Greenland and Antarctica. Nature, 444(7116), 195–198.
Abstract: Precise knowledge of the phase relationship between climate changes in the two hemispheres is a key for understanding the Earth's climate dynamics. For the last glacial period, ice core studies(1,2) have revealed strong coupling of the largest millennial-scale warm events in Antarctica with the longest Dansgaard – Oeschger events in Greenland(3-5) through the Atlantic meridional overturning circulation(6-8). It has been unclear, however, whether the shorter Dansgaard – Oeschger events have counterparts in the shorter and less prominent Antarctic temperature variations, and whether these events are linked by the same mechanism. Here we present a glacial climate record derived from an ice core from Dronning Maud Land, Antarctica, which represents South Atlantic climate at a resolution comparable with the Greenland ice core records. After methane synchronization with an ice core from North Greenland(9), the oxygen isotope record from the Dronning Maud Land ice core shows a one-to-one coupling between all Antarctic warm events and Greenland Dansgaard – Oeschger events by the bipolar seesaw(6). The amplitude of the Antarctic warm events is found to be linearly dependent on the duration of the concurrent stadial in the North, suggesting that they all result from a similar reduction in the meridional overturning circulation.
Fourre, E., Jean-Baptiste, P., Dapoigny, A., Baumier, D., Petit, J. R., & Jouzel, J. (2006). Past and recent tritium levels in Arctic and Antarctic polar caps. Earth Planet. Sci. Lett., 245(1-2), 56–64.
Abstract: Tritium concentration was measured in snow deposited at the GRIP site (central Greenland) and at the Vostok station (east Antarctica) from snow pits covering the period 1980-1990. The objective of the study was to investigate tritium concentrations in polar regions several decades after the bomb peak of the sixties and to put them in the context of available data for environmental tritium in the Arctic and the Antarctic over the last five decades. The tritium content of the samples was measured by mass spectrometry using the helium-3 regrowth method. In Antarctica, the tritium concentrations are in the range 70-110 TU. The comparison of the bomb tritium history at different locations show that tritium levels increase moving inland, where vapour pressure becomes extremely low and therefore more sensitive to the intrusion of stratospheric air masses highly enriched in tritium. Although most tritium fallout occurred in the Northern hemisphere, the tritium levels in central Greenland in the 80's, in the range 10-40 TU, are significantly lower than at Vostok. Unlike Antarctica, no such continental effect is observed in Greenland, due to the higher water vapour content of the air masses, as evidenced by the much higher snow accumulation rate. Whereas tritium fallout in Antarctica appears to occur as a result of direct injections of stratospheric tritium during winter, Arctic fallout are the result of the dominant spring injection of stratospheric air at mid-latitude, in line with the deposition of other stratospheric tracers. (c) 2006 Elsevier B.V. All rights reserved.
Keywords: tritium; ice core; Antarctica; Greenland
Gabrielli, P., Plane, J. M. C., Boutron, C. F., Hong, S. M., Cozzi, G., Cescon, P., et al. (2006). A climatic control on the accretion of meteoric and super-chondritic iridium-platinum to the Antarctic ice cap. Earth Planet. Sci. Lett., 250(3-4), 459–469.
Abstract: Meteoric smoke particles (MSPs) form through the vaporization of meteoroids and the subsequent re-condensation of metallic species in the mesosphere. Recently, iridium and platinum enrichments have been identified in Greenland ice layers and attributed to the fallout of MSPs supplying polar latitudes with cosmic matter during the Holocene. However, the MSP fallout to Antarctica during the Earth's climatic history remains essentially unknown. We have determined iridium and platinum in deep Antarctic ice from Dome C and Vostok dated back to 240 kyrs BP. We find high super-chondritic fluxes during warm periods and low meteoric accretion during glacial times, a pattern that is opposite to any known climatic variation in dust fallout to polar regions. The proposed explanation of this accretion regime is a weaker polar vortex during warm periods, allowing peripheral air masses enriched in volcanic iridium and platinum to penetrate inland to Antarctica. The MSP signal emerges only during cold phases and is four times lower than in the Greenland ice cap where more snow accumulates. This suggests that wet deposition is an important route of cosmic material to the Earth's surface. (c) 2006 Elsevier B.V. All rights reserved.
Keywords: iridium; platinum; meteoric smoke; ice; Antarctica; climate
Gaspari, V., Barbante, C., Cozzi, G., Cescon, P., Boutron, C. F., Gabrielli, P., et al. (2006). Atmospheric iron fluxes over the last deglaciation: Climatic implications. Geophys. Res. Lett., 33(3), 4 pp.
Abstract: A decrease in the micronutrient iron supply to the Southern Ocean is widely believed to be involved in the atmospheric CO2 increase during the last deglaciation. Here we report the first record of atmospheric iron fluxes as determined in 166 samples of the Dome C ice core and covering the last glacial-interglacial transition (22-9 kyr B. P.). It reveals a decrease in fallout flux from 24x10(-2) mg Fe m(-2) yr(-1) during the Last Glacial Maximum to 0.7x10(-2) mg Fe m(-2) yr(-1) at the onset of the Holocene. The acid leachable fraction of iron determined in our samples was the 60% of the total iron mass in glacial samples, about twice the value found for Holocene samples. This emerging difference in iron solubility over different climatic stages provides a new insight for evaluating the iron hypothesis over glacial/interglacial periods.
Lavire, C., Normand, P., Alekhina, I., Bulat, S., Prieur, D., Birrien, J. L., et al. (2006). Presence of Hydrogenophilus thermoluteolus DNA in accretion ice in the subglacial Lake Vostok, Antarctica, assessed using rrs, cbb and hox. Environ. Microbiol., 8(12), 2106–2114.
Abstract: The 3561 m Vostok ice core sample originating from the subglacial Lake Vostok accretion (frozen lake water) ice with sediment inclusions was thoroughly studied by various means to confirm the presence of the thermophile bacterium Hydrogenophilus thermoluteolus reported earlier in the 3607 m accretion ice sample. PCR and molecular-phylogenetic analyses performed in two independent laboratories were made using different 16S rRNA gene (rrs) targeted primers. As a result, rrs-targeted PCR permitted to recover several very closely related clones with a small genetic distance to Hydrogenophilus thermoluteolus (< 1%). In addition, RubisCO (cbbL or rbcL) and NiFe-Hydrogenase (hoxV or hupL) targeted PCR have also allowed to recover sequences highly related to Hydrogenophilus thermoluteolus. All these results point to the presence of thermophilic chemoautotrophic microorganisms in Lake Vostok accretion ice. They presumably originate from deep faults in the bedrock cavity containing the lake in which episodes of seismotectonic activity would release debris along with microbial cells.
Narcisi, B., Petit, J. R., & Tiepolo, M. (2006). A volcanic marker (92 ka) for dating deep east Antarctic ice cores. Quat. Sci. Rev., 25(21-22), 2682–2687.
Abstract: Tephra layers recorded in East Antarctic ice enable reliable linking over long distances and, when correlated with well-dated eruptions in the source area, provide absolute ages for improving the accuracy of model-based ice chronology. We used chronostratigraphic information and grain-specific geochemical data (major elements by electron microprobe and trace elements by LA-ICP-MS) to suggest that a tephra layer from the EPICA-Dome C and Dome Fuji ice cores is the distal counterpart of the Mt. Berlin (Marie Byrd Land province, West Antarctica) pyroclastic unit Ar-40/Ar-39 dated to 92.5 +/- 2.0 and 92.2 +/- 0.9 ka. Such one-to-one correlation, which is proposed here for the first time for the East Antarctic deep climatic archives, provides independent age constraints for glaciological modelling of core timescales. (c) 2006 Elsevier Ltd. All rights reserved.
Castellano, E., Becagli, S., Hansson, M., Hutterli, M., Petit, J. R., Rampino, M. R., et al. (2005). Holocene volcanic history as recorded in the sulfate stratigraphy of the European Project for Ice Coring in Antarctica Dome C (EDC96) ice core. J. Geophys. Res.-Atmos., 110(D6), 12 pp.
Abstract: [1] A detailed history of Holocene volcanism was reconstructed using the sulfate record of the European Project for Ice Coring in Antarctica Dome C (EDC96) ice core. This first complete Holocene volcanic record from an Antarctic core provides a reliable database to compare with long records from Antarctic and Greenland ice cores. A threshold method based on statistical treatment of the lognormal sulfate flux distribution was used to differentiate volcanic sulfate spikes from sulfate background concentrations. Ninety-six eruptions were identified in the EDC96 ice core during the Holocene, with a mean of 7.9 events per millennium. The frequency distribution ( events per millennium) showed that the last 2000 years were a period of enhanced volcanic activity. EDC96 volcanic signatures for the last millennium are in good agreement with those recorded in other Antarctic ice cores. For older periods, comparison is in some cases less reliable, mainly because of dating uncertainties. Sulfate depositional fluxes of individual volcanic events vary greatly among the different cores. A volcanic flux normalization ( volcanic flux/Tambora flux ratio) was used to evaluate the relative intensity of the same event recorded at different sites in the last millennium. Normalized flux variability for the same event showed the highest value in the 1100 – 1500 AD period. This pattern could mirror changes in regional transport linked to climatic variations such as slight warming stages in the Southern Hemisphere ( Southern Hemisphere Medieval Warming – like period?).
Delmonte, B., Petit, J. R., Krinner, G., Maggi, V., Jouzel, J., & Udisti, R. (2005). Ice core evidence for secular variability and 200-year dipolar oscillations in atmospheric circulation over East Antarctica during the Holocene. Clim. Dyn., 24(6), 641–654.
Abstract: Two Holocene ice core records from East Antarctica (Vostok and EPICA-Dome C) were analysed for dust concentration and size distribution at a temporal resolution of 1 sample per similar to 50 years. A series of volcanic markers randomly distributed over the common part of the ice cores (from 9.8 to 3.5 kyear BP) ensures accurate relative dating (+/-33 years). Dust-size records from the two sites display oscillations structured in cycles with sub-millennial and secular scale frequencies that are apparently asynchronous. The power spectra of the composite sum (1) of the two dust-size records display spectral energy mostly for 150- to 500-year periodicities. On the other hand, the 200-year band is common to both records and the 200 year components of the two sites are out-of-phase (100-year lead or lag) over similar to 5.5 kyear, a phenomenon also reflected by a significant ( > 99 % conf. lev.) band in the power spectra of the composite difference (A) of the two size records. During long-range transport, mineral dust originating from the Southern Hemisphere continents is graded to a variable extent depending on the altitude and duration of atmospheric transport. Relatively coarse dust is associated with air mass penetration from the middle-lower troposphere and conversely relatively fine dust with upper troposphere air masses or the influence of subsidence over the Antarctic plateau, a hypothesis already proposed for the changes that occurred during the Last Glacial Maximum to Holocene transition (Delmonte et al. 2004b). Moreover, we assume that the overall fluctuation of air mass advection over Antarctica depends on the meridional pressure gradient with respect to low latitudes, i.e. the Antarctic Oscillation (AAO). We therefore suggest a regional variability in atmospheric circulation over East Antarctica. The 150500 year power spectrum of the composite (1) parameter represents the long term variability of the AAO, imprinted by secular internal oscillations probably related to the southern ocean-climatic system. On the other hand, the A dust composite parameter suggests a persistent atmospheric dipole over East Antarctica delivering coarser (finer) dust particles alternatively to Vostok and Dome C regions with a bi-centennial periodicity. Indeed, a seesaw phenomenon in dust size distribution was already observed at three East Antarctic sites during the last deglaclation (Delmonte et al. 2004b) and was interpreted as a progressive reduction of the eccentricity of the polar vortex with respect to the geographic south pole. Interestingly, the A parameter shows a pronounced 200-year oscillation mode, throwing new light on the unresolved question of a possible relationship between climate and solar activity.
Gabrielli, P., Planchon, F. A. M., Hong, S. M., Lee, K. H., Do Hur, S., Barbante, C., et al. (2005). Trace elements in Vostok Antarctic ice during the last four climatic cycles. Earth Planet. Sci. Lett., 234(1-2), 249–259.
Abstract: Li, V, Cr, Mn, Co, As, Rb, Sr, Ba, Bi and U were determined by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) in various sections of the 3623 m Vostok deep Antarctic ice core dated from 4600 to 410,000 years BP, which corresponds to the last four climatic cycles back to isotopic stage 11.3. Concentrations of all elements were found to be highly variable with low values during interglacial periods and warm interstadials and much higher values during the coldest periods of the last four ice ages. Crustal enrichment factors suggest various sources for the different elements. Rock and soil dust is the dominant source of V, Mn, Rb, Ba and U whatever the period, and of Li, Cr, Co, Sr and As during cold periods. Sea salt aerosol, together with aeolian dust, also contributes significantly to Sr whereas volcanic emissions could provide a significant input for As and Bi especially during warm periods. (c) 2005 Elsevier B.V. All rights reserved.
Keywords: Vostok; trace elements; ice; climate
Hong, S. M., Boutron, C. F., Barbante, C., Do Hur, S., Lee, K., Gabrielli, P., et al. (2005). Glacial-interglacial changes in the occurrence of Pb, Cd, Cu and Zn in Vostok Antarctic ice from 240 000 to 410 000 years BP. J. Environ. Monit., 7(12), 1326–1331.
Abstract: Lead ( Pb), cadmium ( Cd), copper ( Cu) and zinc ( Zn) have been measured by electrothermal atomic absorption spectrometry in various sections of the 3623 m deep ice core drilled at Vostok, in central East Antarctica. The sections were dated from 240 to 410 kyear BP ( Marine Isotopic Stages ( MIS) 7.5 to 11.3), which corresponds to the 3rd and 4th glacial-interglacial cycles before present. Concentrations are found to have varied greatly during this 170 kyear time period, with high concentration values during the coldest climatic stages such as MIS 8.4 and 10.2 and much lower concentration values during warmer periods, such as the interglacials MIS 7.5, 9.3 and 11.3. Rock and soil dust were the dominant sources for Pb, whatever the period, and for Zn and Cu and possibly Cd during cold climatic stages. The contribution from volcanic emissions was important for Cd during all periods and might have been significant for Cu and Zn during warm periods.
Liu, L. B., Kang, J. C., Petit, J. R., Simoes, J. C., & De Angelis, M. (2005). The 4700 aBP volcanic signal detected in Vostok BH8 ice core, Antarctica. Chin. Sci. Bull., 50(22), 2636–2639.
Abstract: The detailed electrical conductivity measurement (ECM), trace chemical compositions and microparticles concentration analysis are performed for BH8 ice core from the depth of 126.0m to 130.0m at Vostok Station. At depth 128.7m, a volcanic signal 4726 a B.P. is detected. The volcanic sulphate flux is 95.8 kg-kru(-2), sulphate peak concentration 1352.8 ng-g(-1), duration time about 10.1 years, comparable with some well-known volcanic events. The results indicate that it seems to be a relatively large scale, long lasting volcanic signal with farther volcanic origin.
Keywords: volcanic eruption; ice core record; Vostok; Antarctica
Narcisi, B., Petit, J. R., Delmonte, B., Basile-Doelsch, I., & Maggi, V. (2005). Characteristics and sources of tephra layers in the EPICA-Dome C ice record (East Antarctica): Implications for past atmospheric circulation and ice core stratigraphic correlations. Earth Planet. Sci. Lett., 239(3-4), 253–265.
Abstract: Thirteen discrete air-fall tephra layers were identified in the last 200,000-yr section of the EPICA-Dome C ice record drilled in the East Antarctic plateau (75 degrees 06'S, 123 degrees 21' E). Quantitative grain size, glass particle morphology, and the grain-discrete major element composition of the glass fraction of these layers were investigated. Through comparison with literature data on the rock composition of Quaternary volcanic centres located within and around Antarctica, five tephra layers were attributed to South Sandwich volcanoes in the South Atlantic Ocean, two to South Shetland volcanoes (northern Antarctic Peninsula), two to Andean volcanoes, and four to Antarctic (Marie Byrd Land and Melbourne) provinces. The abundance of layers originating in the southern part of the Atlantic confirms that westerly atmospheric circulation spiralling towards East Antarctica prevailed over the last 200 ka. Moreover, the record of events from Antarctic centres suggests that atmospheric trajectories from West to East Antarctica can also be significant. A few ash layers are geochemically distinct and appear equivalent to levels from Vostok and Dome Fuji deep ice records, located ca. 600 km and ca. 2000 km, respectively, from Dome C on the Antarctic plateau. These layers provide unambiguous markers for future correlation with other Antarctic ice cores and circumpolar marine climatic records. They also provide reliable constraints to get a common timescale by glaciological modelling, and represent a first step towards absolute ice core dating. (c) 2005 Published by Elsevier B.V.
Keywords: tephra; Antarctic ice cores; EPICA-Dome C ice core; stratigraphic correlation; palaeoatmospheric circulation
|Raynaud, D., Barnola, J. M., Souchez, R., Lorrain, R., Petit, J. R., Duval, P., et al. (2005). Palaeoclimatology – The record for marine isotopic stage 11. Nature, 436(7047), 39–40.
Augustin, L., Barbante, C., Barnes, P. R. F., Barnola, J. M., Bigler, M., Castellano, E., et al. (2004). Eight glacial cycles from an Antarctic ice core. Nature, 429(6992), 623–628.
Abstract: The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago ( Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long – 28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.
De Angelis, M., Petit, J. R., Savarino, J., Souchez, R., & Thiemens, M. H. (2004). Contributions of an ancient evaporitic-type reservoir to subglacial Lake Vostok chemistry. Earth Planet. Sci. Lett., 222(3-4), 751–765.
Abstract: We present here the first comprehensive study of the chemical composition of accretion ice from Lake Vostok. Ion chromatographic analyses were performed on samples obtained along the deeper part of the Vostok ice core. Samples were taken from 3350 down to 3611 in depth, both in glacier ice and subglacial lake ice. The total ionic contents of two accretion ice layers-a few meters thick and centered around 3540 and 3590 in depth-are several times lower than those of glacier ice. Very low concentrations were also observed in the deeper part of accretion ice, below 3609 in depth. Elsewhere, the total ionic content is variable but remains 5 to 50 times higher than in glacier ice. Whatever its total ionic content, the ionic composition of accretion ice is significantly different from what is observed in glacier ice. It is dominated by sodium chloride, homogeneously distributed throughout the ice lattice, as well as calcium and magnesium sulfate, likely located in solid inclusions, or to a lesser extent at grain boundaries. Chemical considerations combined with additional studies of sulfur and oxygen isotopes in sulfate, and iron measurements strongly suggest that glacier water recycling and bedrock hydrolysis do not play a prominent role in providing impurities to accretion ice. It is more likely that NaCl rich water carrying fine sulfate salt particles is sporadically incorporated in the ice accreting in a shallow bay upstream from Vostok. The origin of such salty water, which should also contribute to Lake salinity, is discussed. (C) 2004 Elsevier B.V. All rights reserved.
Keywords: Antarctica; Lake Vostok; accretion ice; ice composition
Delmas, R. J., Beer, J., Synal, H. A., Muscheler, R., Petit, J. R., & Pourchet, M. (2004). Bomb-test Cl-36 measurements in Vostok snow (Antarctica) and the use of Cl-36 as a dating tool for deep ice cores. Tellus Ser. B-Chem. Phys. Meteorol., 56(5), 492–498.
Abstract: A large pulse of atmospheric Cl-36 generated by a limited number of nuclear tests peaked in the late 1950s to early 1960s. The corresponding enhanced Cl-36 deposition is seen in various glaciological archives in the Northern Hemisphere. The profile of the bomb spike recorded in firn layers at Vostok Station, central East Antarctica. has been measured by employing accelerator mass spectrometry (AMS). The records obtained front two well-dated data sets collected in snow pits in 1997 and 1998 show a broad Cl-36 peak, beginning as early as the 1940s and reaching its maximum in the 1960s. The signal is followed by a long-lasting tail up to the surface. This pattern is totally unexpected. We show that the results, unlike the Greenland data, can be explained by a mobility of HCl in the Antarctic firn. This experiment demonstrates the instability of gaseous Cl- deposits. a phenomenon which has important implications for the use of natural cosmogenic Cl-36 radionuclides as a reliable dating tool for deep ice cores from low-accumulation areas. However, during glacial times, under favourable atmospheric chemistry conditions this dating method may still be applicable. Snow metamorphism and ventilation are assumed to be the two main physical processes responsible for the observed patterns.
Delmonte, B., Basile-Doelsch, I., Petit, J. R., Maggi, V., Revel-Rolland, M., Michard, A., et al. (2004). Comparing the Epica and Vostok dust records during the last 220,000 years: stratigraphical correlation and provenance in glacial periods. Earth-Sci. Rev., 66(1-2), 63–87.
Abstract: A new aeolian dust record from the first 2200 m of the EPICA-Dome C ice core (75degrees06' S, 123degrees21' E) covering about 220,000 years of climatic history is compared to the Vostok (78degrees28' S, 106degrees48' E) ice core [Nature 399 (1999) 429]. The two dust profiles are very similar and several common dust events allow to establish stratigraphical links. The late Quaternary period is characterized at both sites, and likely overall East Antarctic plateau, by high dust input during glacial periods. In the EPICA-Dome C ice core, the dust flux rises by a factor of similar to25, similar to20 and similar to12 in glacial stages 2, 4 and 6 with respect to interglacial periods (Holocene and stage 5.5). The magnitude and pattern of changes are comparable in the Vostok, ice core. In this study, the geographical origin of ice core dust (ICD) in cold periods has been investigated at both sites through Sr-87/Sr-86 versus Nd-143/Nd-144 isotopic tracers, following the previous studies of Grousset et al. [Earth Planet. Sci. Lett. 111 (1992) 175] and Basile et al. [Earth Planet. Sci. Lett. 146 (1997) 573]. The new data and the existing ones allow to define the isotopic fields for dust at the two Antarctic sites that are almost identical and restricted into the 0.708<Sr-17/Sr-16<0.711 and -5<ε(Nd)(0)<+5 ranges. This suggests a common geographical provenance for dust at Vostok and Dome C and for all the glacial periods of the late Pleistocene. To decipher the ICD provenance, more than 50 samples of loess and aeolian deposits, sands and fluvioglacial sediments from the Potential Source Areas (PSAs) of the Southern Hemisphere have been collected. However, the methodology has been refined with respect to former studies. First, the isotopic fractionation that can occur in function of grain size has been taken into account, and the PSA's signature has been defined in the <5 μm size range, within which fine-grained dust reaching Antarctica is found. Moreover, a possible contribution from carbonates on the samples from PSAs has also been also considered. South Africa and Australia can be excluded as dominant sources, but a partial overlap arises among southern South America, New Zealand and the Antarctic Dry Valleys isotopic fields, these latter two documented for the first time. A possible contribution from all these three sources cannot be excluded, but complementary arguments suggest the dominant contribution to East Antarctic dust in glacial times deriving from the southern South American region of Patagonia and the Pampas. This study shows a first-order uniformity in the dust flux and geographical provenance to the East Antarctica plateau during glacial periods. (C) 2003 Elsevier B.V. All rights reserved.
Keywords: dust; ice cores; Antarctica; Sr-Nd; Paleoclimate
Delmonte, B., Petit, J. R., Andersen, K. K., Basile-Doelseh, I., Maggi, V., & Lipenkov, V. Y. (2004). Dust size evidence for opposite regional atmospheric circulation changes over east Antarctica during the last climatic transition. Clim. Dyn., 23(3-4), 427–438.
Abstract: Three east Antarctic ice cores (Dome B, EPICA-Dome C and Komsomolskaia) give evidence for a uniform dust input to the polar plateau during the last glacial maximum (LGM)/Holocene transition (20 to 10 kyr BP) and the Sr-87/Sr-86 versus Nd-143/Nd-144 isotopic signature of the mineral particles highlights a common provenance from southern South America at that time. However, the size distribution of dust from the three ice cores highlights important differences within the east Antarctic during the LGM and shows clearly opposite regional trends during the climatic transition. Between Dome B and Dome C the timing of these changes is also different. A geographical diversity also arises from the different phasing of the short-term (multi-secular scale) dust size oscillations that are superposed at all sites on the main trends of glacial to interglacial changes. We hypothesize the dust grading is controlled by size fractionation inresponse to its atmospheric pathway, either in terms of horizontal trajectory or in altitude of transport. Such mechanism is supported also by the dust size changes observed during a volcanic event recorded in Vostok ice. Ice core dust size data suggest preferential upper air subsidence over the EDG-KMS region and easier penetration of relatively lower air masses to the DB area during the LGM. At the end of the last glacial period and during the climatic transition the region of relatively higher subsidence progressively moved southward. The scenario proposed, supported also by the LGM/Holocene regional changes of snow accumulation, likely operates even at sub-millennial time scale.
Delmonte, B., Petit, J. R., Basile-Doelsch, I., Lipenkov, V., & Maggi, V. (2004). First Characterization and Dating of East Antarctic Bedrock Inclusions from Subglacial Lake Vostok Accreted Ice. Environ. Chem., 1(2), 90–94.
Abstract: The Vostok (East Antarctica, 78 degrees S, 106 degrees E) ice core preserves, below the meteoric ice keeping the climatic memory of the last 420 000 years, ice formed by freezing of subglacial Lake Vostok water. This latter contains some bedrock fragments representing unique samples for the geological investigation of the East Antarctic Plateau, covered by similar to 2-4 km of ice. The first geochemical (Sr-87/Sr-86 versus Nd-143/Nd-144) and mineralogical characterization of these inclusions as well as the dating of one of them (Nd model age on whole-rock sample) has given evidence for a Mid-Proterozoic age of the basement lying below the ice sheet, consistent with recent geophysical data. The geochemical characteristics of bedrock inclusions within the accreted ice zone are markedly different from those of the mineral dust of aeolian origin archived in the uppermost part of the Vostok ice core and originating from deflation of the Southern Hemisphere continents, and easily discriminates between the two contributions.
Keywords: dusts; geochemistry (inorganic); minerals; palaeogeochemistry
Ekaykin, A. A., Lipenkov, V. Y., Kuzmina, I. N., Petit, J. R., Masson-Delmotte, V., & Johnsen, S. J. (2004). The changes in isotope composition and accumulation of snow at Vostok station, East Antarctica, over the past 200 years (Vol. 39). Int Glaciological Soc.
Abstract: High-resolution records of isotope composition (8113) and accumulation of snow have been obtained from 10-12 m deep snow pits dug in the vicinity of Vostok station during the 1979/80 and 1999/2000 Antarctic field seasons. We employ meteorological, balloon-sounding and snow-stake data to interpret the isotope record in terms of past temperature changes. Our reconstruction suggests that snow accumulation rate and the near-surface air temperature at Vostok have varied during the past 200 years between 15 and 30 kg m(-2) a(-1), and between -56 and -55 degrees C, respectively, with a slight general tendency to increase from the past to the present. Both parameters reveal a 50 year periodicity that correlates with the Pacific Decadal Oscillation index, implying a climatic teleconnection between central Antarctica and the tropical Pacific.
Hong, S. M., Boutron, C. F., Gabrielli, P., Barbante, C., Ferrari, C. P., Petit, J. R., et al. (2004). Past natural changes in Cu, Zn and Cd in Vostok Antarctic ice dated back to the penultimate interglacial period. Geophys. Res. Lett., 31(20), 4 pp.
Abstract: Improved ice core decontamination procedures have allowed us to obtain the first reliable data on Cu, Zn and Cd in ancient Antarctic ice drilled in a fluid filled hole at Vostok Station, dated back to the beginning of the next to last ice age similar to 240,000 years ago. Cu, Zn and Cd concentrations and fallout fluxes display very large natural variations by up to a factor of 35, with high values obtained during the coldest climatic stages and much lower values during warm climatic stages. Crustal dust was an important source of Cu and Zn during the coldest climatic stages, and volcanic emissions were probably an important source of Cd both during warm and cold periods.
Marino, F., Maggi, V., Delmonte, B., Ghermandi, G., & Petit, J. R. (2004). Elemental composition (Si, Fe, Ti) of atmospheric dust over the last 220 kyr from the EPICA ice core (Dome C, Antarctica) (Vol. 39). Int Glaciological Soc.
Abstract: In this work, we present the records of insoluble silicon (Si), iron (Fe) and titanium (Ti) from continental mineral particles (dust) archived in the first 2200 m of the EPICA Dome C (EDC) ice core. More than 200 samples covering the last 220 kyr, back to marine isotopic stage 7.4, were analyzed using the particle-induced X-ray emission (PIXE) technique, applied here for the first time to the investigation of the mineral content of an Antarctic ice core. The measurements were made exclusively on the insoluble fraction, obtained from filtration of the melted ice samples. The mineral fraction of the particle mass determined from the PIXE measurements is highly correlated to the total dust mass determined by particle counting using a Coulter (c) Counter. The principal variations during the different climatic periods are very coherent between the PIXE analysis results and the total dust mass determined by counting. Both sets of results show increasing concentration values during glacial stages 2, 4 and 6 and very low particle content during interglacials (Holocene and stage 5e). The large increase in atmospheric dustiness during cold stages is assumed to be caused by several factors, among which are the enhanced vigour of atmospheric transport. However, the PIXE results from this work highlight some slight differences in Si, Fe and Ti concentrations with respect to the total dust mass during the different climatic periods. As a hypothesis, such variations could reflect either different atmospheric processes affecting particles during transport, or changes that occurred in the dust source regions.
Salamatin, A. N., Tsyganova, E. A., Lipenkov, V. Y., & Petit, J. R. (2004). Vostok (Antarctica) ice-core time-scale from datings of different origins (Vol. 39). Int Glaciological Soc.
Abstract: Three different approaches to ice-core age dating are employed to develop a depth-age relationship at Vostok, Antarctica: (1) correlating the ice-core isotope record to the geophysical metronome (Milankovich surface temperature cycles) inferred from the borehole temperature profile, (2) importing a known chronology from another (Devils Hole, Nevada, USA) paleoclimatic signal, and (3) direct ice-sheet flow modeling. Inverse Monte Carlo sampling is used to constrain the accumulation-rate reconstruction and ice-flow simulations in order to find the best-fit glaciological time-scale matched with the two other chronologies. The general uncertainty of the different age estimates varies from 2 to 6 kyr on average and reaches 6-15 kyr at maximum. Whatever the causes of this discrepancy might be, they are thought to be of different origins, and the age errors are assumed statistically independent. Thus, the average time-scale for the Vostok ice core down to 3350m depth is deduced consistent with all three dating procedures within the standard deviation limits of +/- 3.6kyr, and its accuracy is estimated as 2.2 kyr on average. The constrained ice-sheet flow model allows, at least theoretically, extrapolation of the ice age-depth curve further to the boundary with the accreted lake ice where (at 3530 m depth) the glacier-ice age may reach similar to 2000 kyr.
Souchez, R., Petit, J. R., Jouzel, J., de Angelis, M., & Tison, J. L. (2004). Reassessing Lake Vostok's behaviour from existing and new ice core data. Earth Planet. Sci. Lett., 217(1-2), 163–170.
Abstract: Interpretation of new ice core data and reappraisal of existing data, both from the basal part of the Vostok ice core, give strong support to a kind of thermolialine circulation in Lake Vostok. Although the salinity of the lake is considered as weak (less than 1parts per thousand), the prominent influence of salinity at high pressure and low temperature on water density makes such a circulation possible. As a consequence, subglacial melting along the northern shores of the lake is balanced, further south, by frazil ice production in the upper water column, its accretion and consolidation at the ice-water interface followed by accreted ice export out of the system together with the southeasterly glacier flow. The dynamics of the system is documented by a stable water isotope budget estimate, by inferences concerning accreted ice formation and by an investigation of ice properties at the transition between meteoric ice and accreted ice. This complex behaviour is the controlling factor on water, biota and sediment fluxes in the lake environment. (C) 2003 Elsevier B.V. All rights reserved.
Keywords: ice composition; stable isotopes; Lake Vostok; Antarctica
Udisti, R., Becagli, S., Castellano, E., Delmonte, B., Jouzel, J., Petit, J. R., et al. (2004). Stratigraphic correlations between the European Project for Ice Coring in Antarctica (EPICA) Dome C and Vostok ice cores showing the relative variations of snow accumulation over the past 45 kyr. J. Geophys. Res.-Atmos., 109(D8), 10 pp.
Abstract: [1] High-resolution chemistry analysis and electrical measurements performed on two ice core records (European Project for Ice Coring in Antarctica (EPICA) Dome C and Vostok) spanning the last 45 kyr allow stratigraphic correlations by matching volcanic events. Several common events were identified along the two ice cores on the basis of acidity and sulphate spikes in snow layers. Timescales were matched through comparison with isotope (deltaD) profiles and using the Antarctic cold reversal (ACR) minimum, a Be-10 peak, and a dust spike as temporal checkpoints. Ratios of relative snow accumulation at the two sites during the Holocene, in the glacial-interglacial transition and in the last part of the glacial period, were reconstructed by finding the best fit between Dome C and Vostok depths recording the same events. After accounting for thinning of the layers as they are buried within the glacier, the Dome C-Vostok accumulation ratio, expected to be roughly constant from the conventional accumulation-temperature-isotope approach, is 1.12 for the glacial period but increases to as much as 1.44 for a large part of the Holocene. Glaciological effects, mainly related to the geographic origin of the Vostok ice along the Ridge B-Vostok axis, can account for only a minor fraction of this change. Instead, we argue that accumulation variability between the cores stems from differential changes in atmospheric circulation during these respective climatic periods at the two sites. Regional changes in atmospheric circulation are proposed with a negative anomaly in Dome C, a positive accumulation anomaly in Vostok, or a combination of both during glacial climate. Our approach may help to improve ice core dating by: (1) revealing anomalies in accumulation-rate estimation based on the classical thermodynamic method and (2) supporting the necessity to take into account contributions due to changes in atmospheric circulation processes.
Keywords: Antarctic ice core comparison; accumulation rate changes; glacial-Holocene atmospheric circulation changes
Delmonte, B., Basile-Doelsch, I., Petit, J. R., Michard, A., Revel-Rolland, M., Maggi, V., et al. (2003). Refining the isotopic (Sr-Nd) signature of potential source areas for glacial dust in East Antarctica. J. Phys. IV, 107, 365–368.
Abstract: The geographical origin of the mineral dust transported to the East Antarctic Plateau from the Southern Hemisphere (SH) continents has been investigated by means of the isotopic (Sr-Nd) signature of samples from Potential Source Areas (PSAs). Dust reaching Antarctica is fine-grained (<5 um), and therefore the new isotopic fields have been defined in the equivalent size range. The so obtained dataset evidences a partial overlap among the signatures of the Ice Core dust and South America, New Zealand and the Antarctic Dry Valleys, while South Africa appear distinctly different; further data are needed for the Australian continent. Despite the geochemical similarity with the Dry Valleys and New Zealand, Southern South America still appears to be the most probable source for dust in Antarctica in glacial times.
Hong, S., Park, J. K., Boutron, C. F., Ferrari, C. P., Petit, J. R., & Lipenkov, V. Y. (2003). Changes in the natural lead, cadmium, zinc, and copper concentrations in the Vostok Antarctic ice over the last two glacial-interglacial cycles (240,000 years). J. Phys. IV, 107, 629–632.
Abstract: We present new ice core records showing the temporal variation in the natural Pb, Cd, Zn, and Cu concentrations in the Vostok Antarctic ice over the past 240,000 years. Our data show that concentrations of these heavy metals have varied remarkably over the last two glacial-interglacial cycles. The concentrations ranged from 0.9 to 21.3, 0.04 to 0.62, 3.12 to 126, and 2.27 to 37.4 pg/g for Ph, Cd, Zn, and Cu, respectively. These profiles provide a better understanding of climate-related variation in the occurrence of these heavy metals in ancient Antarctic ice. The concentrations were much higher during cold glacial periods than during interglacials, and peaked at the coldest glacial stages. The contribution of rock and soil dust is estimated to be close to the measured concentrations of Pb, Zn, and Cu, but not Cd, in the ice during cold glacial periods.
Hong, S. M., Kim, Y., Boutron, C. F., Ferrari, C. P., Petit, J. R., Barbante, C., et al. (2003). Climate-related variations in lead concentrations and sources in Vostok Antarctic ice from 65,000 to 240,000 years BP. Geophys. Res. Lett., 30(22), 5 pp.
Abstract: [1] Pb has been measured in various sections of the 3,623-m Vostok deep Antarctic ice core dated from 65,000 to 240,000 years BP, i.e. back to the beginning of the penultimate ice age and the preceding interglacial (isotopic stage 7.5). Pb concentrations were highly variable during this time interval, with low values down to similar to0.5 pg/g during warm climatic stages and much higher values up to similar to20 pg/g during cold climatic stages, especially isotopic stages 4.2 and 6.2 to 6.6. Rock and soil dust accounts for virtually 100% of Pb measured in the ice during cold climatic stages, while the contribution from volcanoes might be significant during warm stages.
Knusel, S., Ginot, P., Schotterer, U., Schwikowski, M., Gaggeler, H. W., Francou, B., et al. (2003). Dating of two nearby ice cores from the Illimani, Bolivia. J. Geophys. Res.-Atmos., 108(D6), 11 pp.
Abstract: [1] In order to establish a chronology of two nearby ice cores from a glacier at Illimani ( 6438 m), Bolivia, a broad dating approach is presented here, which in particular makes use of the fast, simple, and nearly nondestructive electrical conductivity method (ECM) that provides a highly resolved record. Thus, ECM is suited for counting annual layers in the ice, especially for ice cores extracted from high-mountain glaciers with a fast layer thinning. Furthermore, ECM can be used for detecting volcanic signals. Annual signals in the ECM record of the Illimani ice core were identified using the 1964 A. D. tritium reference horizon and were counted along 125 m or 90% of the core, representing the time period from 1200 +/- 240 A. D. ( estimated accumulated error) to 1999 A. D. The resulting age-depth relationship was supported by counting annual peaks in the microparticle record as well as by nuclear dating using the decay of Pb-210. The identification of volcanic signals originating from eruptions such as Pinatubo (1991 A.D.), El Chichon (1982 A.D.), Agung (1963 A.D.), Krakatoa (1883 A.D.), Tambora (1815 A.D.), and the Unknown 1258 A.D. significantly reduced the uncertainty of annual layer counting (ALC) to +/- 2 years in the vicinity of these events.
|Petit, J. - R., Blot, M., & Bulat, S. (2003). Lac Vostok : A la découverte d'un environnement sous-glaciaire et de son contenu biologique (J. P. Parisot, Ed.). in Environnement de la Terre Primitive. Presses Universitaires de Bordeaux.
Planchon, F. A. M., Barbante, C., Boutron, C. F., Bulat, S., Cescon, P., Cozzi, G., et al. (2003). Trace elements in accreted ice from the Vostok sub-glacial lake, Antarctica: Initial results. J. Phys. IV, 107, 1067–1070.
Abstract: We present in this study initial results on trace elements concentrations changes in the deepest part of the Vostok ice core. From 3310 m depth to the bottom of the ice core (3623 m), ice encountered is made of disturbed glacial ice by glacier dynamics and accreted ice from the sub-glacial lake Vostok. Since trace elements are involved in various biogeochemical processes, studying these elements in the accreted ice of the Vostok lake can lead to a better understanding of lake chemistry and life development in such extreme environment. Because concentrations to be measured in Antarctic ice are exceedingly low, such investigations on trace elements require strict control of contamination problems and the use of ultraclean protocols. Initial results obtained for Zn concentrations changes show high variability (< 0.5 to 32 pg/g), with the lowest concentrations found in the accreted ice of the Vostok lake (< 0.5 pg/g). According to crustal enrichment factors close to unity, Zn seems to be mainly associated with crustal material.
Ramirez, E., Hoffmann, G., Taupin, J. D., Francou, B., Ribstein, P., Caillon, N., et al. (2003). A new Andean deep ice core from Nevado Illimani (6350 m), Bolivia. Earth Planet. Sci. Lett., 212(3-4), 337–350.
Abstract: A new ice core record from the Nevado Illimani (16degreesS), Bolivia, covers approximately the last 18 000 years BP. A comparison with two published ice records, from Sajama (18degreesS), Bolivia [Thompson et al., Science 282 (1998) 1858-1864] and Huascaran (9degreesS), Peru [Thompson et al., Science 269 (1996) 46-50], documents a regionally coherent transition from glacial to modern climate conditions in South America north of 20degreesS. The strong resemblance between the Illimani and Huascaran water isotope records and their differences from the Sajama record, in particular during the period from 9000 years BP to 14 000 years BP, suggest that local water recycling or local circulation changes played a major role for Sajama. We interpret the common Illimani/Huascaran water isotope history in terms of a common change from wetter/cooler conditions during glacial times to drier/warmer conditions in the Early Holocene. (C) 2003 Elsevier Science B.V. All rights reserved.
Keywords: glaciology; ice cores; tropical climate during the last glacial; water isotopes in the Andes
Souchez, R., Jean-Baptiste, P., Petit, J. R., Lipenkov, V. Y., & Jouzel, J. (2003). What is the deepest part of the Vostok ice core telling us? Earth-Sci. Rev., 60(1-2), 131–146.
Abstract: This review paper is mainly concerned with a geochemical investigation of the deepest part of the Vostok ice core between 3310 m, the depth at which the palaeoenvironmental record present in the ice above is lost, and the bottom of the core about 130 m above subglacial Lake Vostok. Two sections constitute this part of the core. The upper section (3310-3539 m depth) still consists of ice of meteoric origin but subjected to widespread complex deformation. This deformation is analysed in light of a deltaD-deuterium excess diagram and information on microparticles, crystal sizes and chemical elements distributions in that part of the core. Such ice deformation occurred when the ice was still grounded upstream from Vostok station in a region with subfreezing temperatures. The lower section from 3539 m to the bottom of the core at 3623 m depth is lake ice formed by freezing of subglacial Lake Vostok waters. This is indicated by the isotopic properties (deltaD, delta(18)O and deuterium excess), by electrical conductivity measurements (ECM), crystallography and gas content of the ice. These ice core data together with data on ionic chemistry favour an origin of the lake ice by frazil ice generation in a supercooled (below pressure melting point) water plume existing in the lake followed by accretion and consolidation by subsequent freezing of the host water. The helium profile of this deepest part of the Vostok core is quite unusual and surprising. It has important implications for the interactions between the ice sheet and the lake. Two constrasting scenarios can be satisfactorily constructed so that the lake residence time is not well constrained. (C) 2002 Elsevier Science B.V All rights reserved.
Keywords: Vostok ice core; helium; deuterium
|Delmonte, B., Basile-Doelsch, I., Michard, A., Petit, J. R., Maggi, V., Gemmiti, B., et al. (2002). Sr-Nd signature of potential source areas for dust in East Antarctica: Preliminary results. Geochim. Cosmochim. Acta, 66(15a), A175.
Delmonte, B., Petit, J. R., & Maggi, V. (2002). Glacial to Holocene implications of the new 27000-year dust record from the EPICA Dome C (East Antarctica) ice core. Clim. Dyn., 18(8), 647–660.
Abstract: Insoluble dust concentrations and volume-size distributions have been measured for the new 581 m deep Dome C-EPICA ice core (Antarctica). Over the 27000 years spanned by the record, microparticle measurements from 169 levels, to date, confirm evidence of the drastic decrease in bulk concentration from the Last Glacial Maximum (LGM) to the Holocene (interglacial) by a factor of more than 50 in absolute value and of about 26 ill flux. Unique new features revealed by the EPICA profile include a higher dust concentration during the Antarctic Cold Reversal phase (ACR) by a factor of 2 with respect to the Holocene average. This event is followed by a well-marked minimum that appears to be concomitant with the methane peak that marks the end of the Younger Dryas in the Northern Hemisphere. Particle volume-size distributions show a mode close to 2 mum in diameter, with a slight increase from the LGM to the Holocene; the LGNI/Holocene concentration ratio appears to be dependent on particle size and for diameters from 2 to 5 mum it changes from 50 to 6. Glacial samples are characterised by well-sorted particles and very uniform distributions, while the interglacial samples display a high degree of variability and dispersion. This suggests that different modes of transport prevailed during the two climatic periods with easier penetration of air masses into Antarctica in the Holocene than during Glacial times. Assuming tat southern South America remained the main dust source for East Antarctica over the time period studied, the higher dust content recorded during the ACR which preceded the Younger Dryas period, represents evidence of a change in South America environmental conditions at this time. A wet period and likely mild climate in South America is suggested at circa 11.5-11.7 kyr BP corresponding to the end of the Younger Dryas. The Holocene part of the profile also shows a slight general decrease in concentration, but with increasingly large particles that may reflect gradual changes at the source.
Delmonte, B., Petit, J. R., & Maggi, V. (2002). LGM-Holocene changes and Holocene millennial-scale oscillations of dust particles in the EPICA Dome C ice core, East Antarctica (Vol. 35). Int Glaciological Soc.
Abstract: Measurements of the concentration and size distribution of dust particles found in the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core, East Antarctica, provide records covering the last 27 000 years. The total concentration decreased drastically by a factor of 55 from the Last Glacial Maximum (LGM) (800 ppb) to the Holocene (15 ppb), with a well-marked absolute minimum around 11500-11600 years ago. This latter almost corresponds to the end of the Younger Dryas in Greenland, which was marked by a methane peak related to the expansion of tropical wetlands. Assuming that the source region for Antarctic dust is the southern part of South America, the Antarctic dust minimum suggests a larger geographical extent for this wet period. The volume (mass) similar tosize distribution of the particles displays a mode which is close to 2 mum in diameter, shifting from 1.9 mum in the glacial period to 2.07 mum in the Holocene. As opposed to previous results from old Dome C, EPICA suggests a greater proportion of large particles in Holocene samples than in LGM samples. In addition, for the period 13000-2000 BP, structured millennial-scale oscillations of he dust mode appear. These are especially well marked before 5000 years ago, with higher frequencies also present. The difference between LGM and Holocene particle distributions may be related to changes in the pattern of dust transport to East Antarctica. At Dome C the greater proportion of coarse particles observed during the Holocene suggests greater direct meridional transport. During the LGM, atmospheric circulation was likely more zonal, causing a greater amount of large dust particles to be removed from the atmosphere before reaching Antarctica. Changes in atmospheric circulation could also be the cause of the millennial-scale dust-mode oscillations during the Holocene.
Ekaykin, A. A., Lipenkov, V. Y., Barkov, N. I., Petit, J. R., & Masson-Delmotte, V. (2002). Spatial and temporal variability in isotope composition of recent snow in the vicinity of Vostok station, Antarctica: implications for ice-core record interpretation (Vol. 35). Int Glaciological Soc.
Abstract: Continuous, detailed isotope (deltaD and delta(18)O) profiles were obtained from eight snow pits dug in the vicinity of Vostok station, Antarctica, during the period 1984-2000. In addition, snow samples taken along the 1 km long accumulation-stake profile were measured to determine spatial variability in isotope composition of recent snow. The stacked deltaD time series spanning the last 55 years shows only weak correlation with the mean annual air temperature recorded at Vostok station. Significant oscillations of both snow accumulation and snow isotope composition with the periods 2.5, 5, 20 and, possibly, similar to10(2) years observed at single points are interpreted in terms of drift of snow-accumulation waves of various scales on the surface of the ice sheet.
Simoes, J. C., Petit, J. R., Souchez, R., Lipenkov, V. Y., De Angelis, M., Liu, L. B., et al. (2002). Evidence of glacial flour in the deepest 89 m of the Vostok ice core (Vol. 35). Int Glaciological Soc.
Abstract: The 3623 in long Vostok ice core is divided into two main parts: (1) from the surface to a depth of 3310 in, the ice layers are undisturbed and may be used to reconstruct the climatic record over the past 420 kyr; (2) from 3538 in to the bottom, the core is made up of accreted ice formed by freezing of the lake. In between, the glacier ice is disturbed by ice dynamics, as shown, for example, by inclined volcanic-ash layers. Microparticle concentrations and distributions as well as ionic and isotopic content were used to subdivide this third section. The identification of layers with bedrock material provides clues as to the entrainment processes at sub-freezing temperatures. Dust concentration and size distribution as well as ionic content arc comparable with values found in ice of glacial and interglacial periods. Below 34,50 in depth, however, the mode of the volume size distribution clearly shifts from 2.1 mum to 3.4 mum in diameter. Particles as large as 30 mum In diameter are observed and cannot have an aeolian origin. From microscopic observations, we suggest that they originate from the bedrock and represent glacial flour entrained in a shear layer up to 89 in from the glacier sole. This process most likely occurred when the ice sheet was grounded before flowing over the lake.
Souchez, R., Petit, J. R., Jouzel, J., Simoes, J., de Angelis, M., Barkov, N., et al. (2002). Highly deformed basal ice in the Vostok core, Antarctica. Geophys. Res. Lett., 29(7), 4 pp.
Abstract: [1] Our paper documents the build-up of a highly deformed basal ice layer in the basal part of the Vostok ice core. This is done mainly on the basis of an isotopic composition investigation of the ice. Complex deformation in the lower 228 m of the ice sheet has resulted in folding and intermixing of ice at a submetric scale and, for the upper part of this basal sequence, in interbedding of ice layers from distinct origins at a larger scale. This complex deformation occurred at a temperature largely below the pressure-melting point. The basal ice layer has built upwards and size-selective incorporation of bed material into the ice has taken place. The documentation of this complex basal deformation has implications for the maximum age of ice that will be useful in paleoclimate studies and for ice sheet dynamics.
Weiss, J., Vidot, J., Gay, M., Arnaud, L., Duval, P., & Petit, J. R. (2002). Dome Concordia ice microstructure: impurities effect on grain growth (Vol. 35). Int Glaciological Soc.
Abstract: We present a detailed analysis of the microstructure in the shallow part (100-580 m) of the European Project for Ice Coring in Antarctica (EPICA) ice core at Dome Concordia. In the Holocene ice, the average grain-size increases with depth. This is the normal grain-growth process driven by a reduction of the total grain-boundary energy Deeper, associated with the Holocene-Last Glacial Maximum (LGM) climatic transition, a sharp decrease of the average grain-size is observed. To explain modifications to the microstructure with climatic change, we discuss the role of soluble and insoluble (microparticles) impurities in the grain-growth process of Antarctic ice, coupled with an analysis of the pinning of grain boundaries by microparticles. Our data indicate that high soluble impurity content does not necessarily imply a slowing-down of grain-growth kinetics, whereas the pinning of grain boundaries by dust particles located along the boundaries does explain modifications to the microstructure (small grain-sizes; change in grain-size distributions, etc.) observed in volcanic ash layers or dusty LGM ice. Moreover, classical mean-Field models of grain-boundary pinning are in good quantitative agreement with the evolution of grain-size along the EPICA ice core. This suggests a major role for dust in the modification of shallow polar ice microstructure.
Basile, I., Petit, J. R., Touron, S., Grousset, F. E., & Barkov, N. (2001). Volcanic layers in Antarctic (Vostok) ice cores: Source identification and atmospheric implications. J. Geophys. Res.-Atmos., 106(D23), 31915–31931.
Abstract: Fifteen visible volcanic ash layers (tephra) from Vostok ice cores have been analyzed for major elements, trace elements, and Sr and Nd isotope composition. Comparison of their geochemical signatures to lava composition from the inventory of Antarctic and subantarctic volcanoes, which have been active over the last 0.5 million years, indicates that nine layers originate from activity of the South Sandwich volcanic arc, three from southern South America, one from the Antarctic Peninsula (Bransfield Strait), and one from West Antarctica (Marie Byrd Land province). The large size of the tephra (up to 50 mum) requires rapid atmospheric transfer from the volcanic centers to East Antarctica. Rapid tropospheric transport from the southwestern Atlantic, penetrating East Antarctica, therefore predominates during the period studied, whether in glacial or interglacial climatic mode. In spite of the low frequency of occurrence of visible tephra layers in Vostok core (one event every 20 kyr), the overall atmospheric pathway of these ash events appears consistent with the almost continuous advection of continental dust from South America.
Jean-Baptiste, P., Petit, J. R., Lipenkov, V. Y., Raynaud, D., & Barkov, N. I. (2001). Constraints on hydrothermal processes and water exchange in Lake Vostok from helium isotopes. Nature, 411(6836), 460–462.
Abstract: Lake Vostok, the largest subglacial lake in Antarctica, is covered by the East Antarctic ice sheet, which varies in thickness between 3,750 and 4,100 m (ref. 1). At a depth of 3,539 m in the drill hole at Vostok station, sharp changes in stable isotopes and the gas content of the ice delineate the boundary between glacier ice and ice accreted through re-freezing of lake water(2). Unlike most gases, helium can be incorporated into the crystal structure of ice during freezing(3), making helium isotopes in the accreted ice a valuable source of information on lake environment. Here we present helium isotope measurements from the deep section of the Vostok ice core that encompasses the boundary between the glacier ice and accreted ice, showing that the accreted ice is enriched by a helium source with a radiogenic isotope signature typical of an old continental province. This result rules out any significant hydrothermal energy input into the lake from high-enthalpy mantle processes, which would be expected to produce a much higher He-3/(4) He ratio. Based on the average helium flux for continental areas, the helium budget of the lake leads to a renewal time of the lake of the order of 5,000 years.
Jouzel, J., Masson, V., Cattani, O., Falourd, S., Stievenard, M., Stenni, B., et al. (2001). A new 27 ky high resolution East Antarctic climate record. Geophys. Res. Lett., 28(16), 3199–3202.
Abstract: The ice core recently drilled at the Dome Concordia site on the East Antarctic plateau provides a new high resolution isotope record covering part of the last glacial, the last transition and the Holocene. The two step shape of the deglaciation is remarkably similar for all the ice cores now available on the East Antarctic plateau. The first warming trend ends about 14000 years ago and is followed by the well marked Antarctic Cold Reversal (ACR) with a secondary peak common to all records. During the deglaciation, there are more similarities between the near coastal site of Taylor Dome and inland East Antarctica than between Taylor Dome and central Greenland. However, the results for EPICA do appear to confirm the Taylor Dome timescale after about 14 ka, showing cooling into the ACR roughly in phase between Greenland and Antarctica. While the overall deglacial pattern is asynchronous, this suggests that the now classical picture of a temperature seesaw between Antarctica and Greenland may be too simplistic.
Montagnat, M., Duval, P., Bastie, P., Hamelin, B., Brissaud, O., de Angelis, M. T., et al. (2001). High crystalline quality of large single crystals of subglacial ice above Lake Vostok (Antarctica) revealed by hard X-ray diffraction. Comptes Rendus Acad. Sci. Ser II-A, 333(8), 419–425.
Abstract: X-ray diffraction experiments were carried out on large ice crystals from accreted ice above Lake Vostok, a subglacial lake lying beneath the East Antarctic ice sheet. Results indicate a surprisingly very low lattice distortion. This crystalline quality does not seem to be affected by impurities. Abnormal grain growth should occur and could explain both the large grain size and the low lattice distortion. Accreted ice is therefore supposed to be non-plastically deforming. These results should be taken into account for further studies of the permeability of accreted ice to drilling fluid present in the borehole. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
Keywords: X-ray diffraction; ice monocrystals; Lake Vostok, Antarctica; abnormal grain growth
Schwander, J., Jouzel, J., Hammer, C. U., Petit, J. R., Udisti, R., & Wolff, E. (2001). A tentative chronology for the EPICA Dome Concordia ice core. Geophys. Res. Lett., 28(22), 4243–4246.
Abstract: A tentative age scale (EDC1) for the last 45 kyr is established for the new 788-m EPICA Dome C ice core using a simple ice flow model. The age of volcanic eruptions, the end of the Younger Dryas event, and the estimated depth and age of elevated Be-10, about 41 kyr ago were used to calibrate the model parameters. The uncertainty of EDC1 is estimated to +/- 10 yr for 0 to 700 yr BP, up to +/- 200 yr back to 10 kyr BP, and up to +/- 2 kyr back to 41 kyr BP. The age of the air in the bubbles is calculated with a firn densification model. In the Holocene the air is about 2000 yr younger than the ice and about 5500 yr during the last glacial maximum.
Siegert, M. J., Ellis-Evans, J. C., Tranter, M., Mayer, C., Petit, J. R., Salamatin, A., et al. (2001). Physical, chemical and biological processes in Lake Vostok and other Antarctic subglacial lakes. Nature, 414(6864), 603–609.
Abstract: Over 70 lakes have now been identified beneath the Antarctic ice sheet. Although water from none of the lakes has been sampled directly, analysis of lake ice frozen (accreted) to the underside of the ice sheet above Lake Vostok, the largest of these lakes, has allowed inferences to be made on lake water chemistry and has revealed small quantities of microbes. These findings suggest that Lake Vostok is an extreme, yet viable, environment for life. All subglacial lakes are subject to high pressure (similar to 350 atmospheres), low temperatures (about -3 degreesC) and permanent darkness. Any microbes present must therefore use chemical sources to power biological processes. Importantly, dissolved oxygen is available at least at the lake surface, from equilibration with air hydrates released from melting basal glacier ice. Microbes found in Lake Vostok's accreted ice are relatively modern, but the probability of ancient lake-floor sediments leads to a possibility of a very old biota at the base of subglacial lakes.
Vimeux, F., Masson, V., Delaygue, G., Jouzel, J., Petit, J. R., & Stievenard, M. (2001). A 420,000 year deuterium excess record from East Antarctica: Information on past changes in the origin of precipitation at Vostok. J. Geophys. Res.-Atmos., 106(D23), 31863–31873.
Abstract: Here we present and analyze the complete Vostok ice cores deuterium excess record which spans the last four climatic cycles, back to similar to420,000 years B.P. To extract paleoclimate information from this record, we use isotopic modeling showing that changes in deuterium excess (d = deltaD-8delta(18)O) of Vostok precipitation reflect changes in the average temperature of oceanic moisture sources. Over the last 250,000 years the deuterium excess is strongly anticorrelated with changes in Earth's obliquity. This reflects changes in the relative contribution of low and high latitudes to the Vostok precipitation, resulting from changes in the latitudinal annual mean insolation gradient governed by the obliquity. However, this modulation by obliquity is not observed prior to 250,000 years B.P. We attribute this difference to the ice flow, the deeper ice under Vostok station having accumulated in a location upstream Vostok, receiving precipitation from different oceanic origins. Despite this difference between the earlier and the later portions of the record, the deuterium excess changes during all the glacial inceptions are similar in amplitude and timing relative to the deuterium decrease. The glacial inceptions are characterized by high deuterium excess, indicating the significant role of the tropics in supplying moisture to the already cold poles.
Vimeux, F., Masson, V., Jouzel, J., Petit, J. R., Steig, E. J., Stievenard, M., et al. (2001). Holocene hydrological cycle changes in the Southern Hemisphere documented in East Antarctic deuterium excess records. Clim. Dyn., 17(7), 503–513.
Abstract: Four Holocene-long East Antarctic deuterium excess records are used to study past changes of the hydrological cycle in the Southern Hemisphere. We combine simple and complex isotopic models to quantify the relationships between Antarctic deuterium excess fluctuations and the sea surface temperature (SST) integrated over the moisture source areas for Antarctic snow. The common deuterium excess increasing trend during the first half of the Holocene is therefore interpreted in terms of a warming of the average ocean moisture source regions over this time. Available Southern Hemisphere SST records exhibit opposite trends at low latitudes (warming) and at high latitudes (cooling) during the Holocene. The agreement between the Antarctic deuterium excess and low-latitude SST trends supports the idea that the tropics dominate in providing moisture for Antarctic precipitation. The opposite trends in SSTs at low and high latitudes can potentially be explained by the decreasing obliquity during the Holocene inducing opposite trends in the local mean annual insolation between low and high latitudes. It also implies an increased latitudinal insolation gradient that in turn can maintain a stronger atmospheric circulation transporting more tropical moisture to Antarctica. This mechanism is supported by results from a mid-Holocene climate simulation performed using a coupled ocean-atmosphere model.
Masson, V., Vimeux, F., Jouzel, J., Morgan, V., Delmotte, M., Ciais, P., et al. (2000). Holocene climate variability in Antarctica based on 11 ice-core isotopic records. Quat. Res., 54(3), 348–358.
Abstract: A comparison is made of the Holocene records obtained from water isotope measurements along 11 ice cores from coastal and central sites in east Antarctica (Vostok, Dome B, Plateau Remote, Komsomolskaia, Dome C, Taylor Dome, Dominion Range, D47, KM105, and Law Dome) and west Antarctica (Byrd), with temporal resolution from 20 to 50 yr. The longterm trends possibly reflect local ice sheet elevation fluctuations superimposed on common climatic fluctuations. All the records confirm the widespread Antarctic early Holocene optimum between 11,500 and 9000 yr; in the Ross Sea sector, a secondary optimum is identified between 7000 and 5000 yr, whereas all eastern Antarctic sites show a late optimum between 6000 and 3000 yr, Superimposed on the long time trend, all the records exhibit 9 aperiodic millennial-scale oscillations. Climatic optima show a reduced pacing between warm events (typically 800 yr), whereas cooler periods are associated with less-frequent warm events (pacing > 1200 yr). (C) 2000 University of Washington.
Pepin, L., Barnola, J. M., Petit, J. R., & Raynaud, D. (2000). Time evolutions of the greenhouse effect gases concentration and the climate from the Vostok core. Houille Blanche-Rev. Int., (3-4), 64–67.
Abstract: Polar ice and air bubbles trapped in it, attest climate history and the atmospheric composition of the Earth. The Vostok drill at the Russian station of Vostok on the Antarctic Plateau provides a more 400 000-year long record of these conditions. Through this time, climate in Antarctica oscillated between 4 glacials, for which surface temperatures were about 10 degreesC below modern ones, and 5 interglacial periods as the modern one. It is shown that greenhouse gases (CO2 and CH4) concentrations are higher during warm periods than cold ones. Scrutinising glacial to interglacial transitions shows that southern Hemisphere processes lead northern ones. Furthermore, sea level rise appears to lag variations of other variables. Finally, these records give evidence that CO2 and CH4 levels measured at present time, have never been reached during the late 420 000 years.
Souchez, R., Petit, J. R., Tison, J. L., Jouzel, J., & Verbeke, V. (2000). Ice formation in subglacial Lake Vostok, Central Antarctica. Earth Planet. Sci. Lett., 181(4), 529–538.
Abstract: The investigation of chemical and isotopic properties in the lake ice from the Vostok ice core gives clues to the mechanisms involved in ice formation within the lake. A small lake water salinity can be reasonably deduced from the chemical data. Possible implications for the water circulation of Lake Vostok are developed. The characteristics of the isotopic composition of the lake ice indicate that ice formation in Lake Vostok occurred by frazil ice crystal generation due to supercooling as a consequence of rising waters and a possible contrast in water salinity. Subsequent consolidation of the developed loose ice crystals results in the accretion of ice to the ceiling of the lake. (C) 2000 Elsevier Science B.V. All rights reserved.
Keywords: stable isotopes; glacial geology; ice; Vostok Station; Antarctica
|Jouzel, J., Petit, J. - R., Souchez, R., Barkov, N. I., Lipenkov, V. Y., Raynaud, D., et al. (1999). More than 200 maters of lake Vostok, Antarctica. Science, 286(5447), 2138–2141.
|Petit, J. - R., Jouzel, J., Raynaud, D., Barkov, N. I., Barnola, J. - M., Basile, I., et al. (1999). Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature, 399(6735), 429–436.
|Vimeux, F., Masson, V., Jouzel, J., Stievenard, M., & Petit, J. - R. (1999). Glacial-interglacial changes in ocean surface conditions in the Southern Hemisphere. Nature, 398(6725), 410–413.
Wolff, E., Basile, I., Petit, J. R., & Schwander, J. (1999). Comparison of Holocene electrical records from Dome C and Vostok, Antarctica (Vol. 29).
Abstract: As part of the European Project for Ice Goring in Antarctica, a new deep ice core is being drilled at Dome C. Two electrical methods have been used on the core drilled so far: a new design of electrical conductivity method (ECM) instrument, and a traditional dielectric profiler. The two profiles are very similar in both peaks and background, consistent with acidity being the dominant influence on both in this part of the record. The Dome C records have been compared to ECM records from Vostok, and a tentative match has been made between them. This suggests a long-term average ratio of accumulation rate of 1.36 between this Dome C core and Vostok, and that the Dome C core analyzed so far (to 358 m) probably includes the very end of the Glacial-Holocene transition.
|Jouzel, J., Petit, J. - R., & Stievenard, M. (1998). Evolution of Severnaya Zemlya Glaciation in Holocene. In The Second International Conference on Climate and Water (Vol. 3, pp. 1205–1216). Espoo, Finlande: Risto Lemmela and Nea Hetenius.
Maggi, V., Orombelli, G., Stenni, B., Flora, O., Udisti, R., Becagli, S., et al. (1998). 70 years of northern Victoria Land (Antarctica) accumulation rate (Vol. 27).
Abstract: Measurements of oxygen isotope ratio (delta(18)O), major anions and cations, insoluble dust and tritium were performed every 4-6 cm along the Hercules Neve (northern Victoria Land, Antarctica) 22 m firn core. Concentration/depth profiles for H2O2, methane sulphonic acid and non-sea-salt sulphate (nssSO(4)(2-)) were used to obtain a dating for the core by a multiparametric method involving a normalisation procedure and a linear combination of original profiles. This dating was compared With the delta(18)O and dust records to obtain a reliable identification of successive annual snow layers. The time-scale obtained from the seasonally varying signals was confirmed by an absolute date obtained from the 1965 thermonuclear atmospheric bomb test tritium peak. Around 70 years (1926-94) of annual accumulation rate data were obtained from the core. delta(18)O variations recorded along the core may be ascribed to seasonal variations of this parameter related to temperature variations.
|Maggi, W., & Petit, J. - R. (1998). Atmospheric dust concentration record from the Hercules Névé firn core, northern Victoria Land, Antarctica. Annals of Glaciology, 27, 355–359.
Salamatin, A. N., Lipenkov, V. Y., Barkov, N. I., Jouzel, J., Petit, J. R., & Raynaud, D. (1998). Ice core age dating and paleothermometer calibration based on isotope and temperature profiles from deep boreholes at Vostok Station (East Antarctica). Journal Of Geophysical Research-Atmospheres, 103(D8), 8963–8977.
Abstract: An interpretation of the deuterium profile measured along the Vostok (East Antarctica) ice core down to 2755 m has been attempted on the basis of the borehole temperature analysis. An inverse problem is solved to infer a local "geophysical metronome," the orbital signal in the surface temperature oscillations expressed as a sum of harmonics of Milankovich periods. By correlating the smoothed isotopic temperature record to the metronome, a chronostratigraphy of the Vostok ice core is derived with an accuracy of +/-3.0-4.5 kyr. The developed timescale predicts an age of 241 kyr at a depth of 2760 m, The ratio delta D/delta T-i between deuterium content and cloud temperature fluctuations (at the top of the inversion layer) is examined by fitting simulated and measured borehole temperature profiles. The conventional estimate of the deuterium-temperature slope corresponding to the present-day spatial ratio (9 per mil/degrees C) is confirmed in general. However, the mismatch between modeled and measured borehole temperatures decreases noticeably if we allow surface temperature, responsible for the thermal state of the ice sheet, to undergo more intensive precession oscillations than those of the inversion temperature traced by isotope record. With this assumption, we obtain the long-term temporal deuterium-temperature slope to be 5.8-6.5 per mil/degrees C which implies that the glacial-interglacial temperature increase over central Antarctica was about 15 degrees C in the surface temperature and 10 degrees C in the inversion temperature. Past variations of the accumulation rate and the corresponding changes in the ice-sheet surface elevation are simultaneously simulated.
|Salamatin, A. N., Vostretsov, R. N., Petit, J. - R., Lipenkov, V. Y., & Barkov, N. I. (1998). Geophysical and paleoclimatic supplement of a constituent temperature profile from a deep borehole on the Vostok station (Antarctica). Material for Glaciological Research, (85), 233–240.
Basile, I., Grousset, F. E., Revel, M., Petit, J. R., Biscaye, P. E., & Barkov, N. I. (1997). Patagonian origin of glacial dust deposited in East Antarctica (Vostok and Dome C) during glacial stages 2, 4 and 6. Earth And Planetary Science Letters, 146(3-4), 573–589.
Abstract: The source area of continental dust deposited at both Vostok and Dome C sites (East Antarctica) during the glacial stages (stage 2: similar to 18 ka (Last Glacial Maximum), stage 4: similar to 60 ka and stage 6: similar to 160 ka) of the last two climatic cycles has remained constant. The isotopic composition (Sr-87/Sr-86 and Nd-143/Nd-114) of the ice-core dust has been compared with the isotopic composition of the potential source areas: Antarctica, New Zealand, Southern Africa, Australia and South America. This comparison reveals the southern South American provenance of the dust for all three glacial periods, as has already been shown for the LGM [1], We show that the Patagonian loess and the marine shelf sediments from the Argentine continental shelf, which was variably emerged during glacial periods, display different isotopic compositions and that the composition of the Patagonian loess best matches the signature of the ice-core dust, The identification of the Patagonian region as the source of the windblown dust deposited over East Antarctica during all the latest glacial periods permits a better understanding of paleo-atmospheric circulations of the last climatic cycles and a better constraint on the parametrization of dust sources for paleoatmospheric general circulation models.
|Petit, J. R., Basile, I., Leruyuet, A., Raynaud, D., Lorius, C., Jouzel, J., et al. (1997). Four climate cycles in Vostok ice core. Nature, 387(6631), 359–360.
Jouzel, J., Waelbroeck, C., Malaize, B., Bender, M., Petit, J. R., Stievenard, M., et al. (1996). Climatic interpretation of the recently extended Vostok ice records. Climate Dynamics, 12(8), 513–521.
Abstract: A new ice core drilled at the Russian station of Vostok in Antarctica reached 2755 m depth in September 1993, At this depth, the glaciological time scale provides an age of 260 ky BP (+/-25). We refine this estimate using records of dust and deuterium in the ice and of delta(18)O of O-2 in the entrapped air. delta(18)O of O-2 is highly correlated with insolation over the last two climatic cycles if one assumes that the EGT chronology overestimates the increase of age with depth by 12% for ages older than 112 ky BP. This modified age-depth scale gives an age of 244 ky BP at 2755 m depth and agrees well with the age-depth scale of Walbroeck et al. (in press) derived by orbital tuning of the Vostok delta D record. We discuss the temperature interpretation of this latter record accounting for the influence of the origin of the ice and using information derived from deuterium-excess data. We conclude that the warmest period of stage 7 was likely as warm as today in Antarctica. A remarkable feature of the Vostok record is the high level of similarity of proxy temperature records for the last two climatic cycles (stages 6 and 7 versus stages 1-5). This similarity has no equivalent in other paleorecords.
|Abysov, S. S., de Angelis, M., Barkov, N. I., Barnola, J. - M., Bender, M., Chappellaz, J., et al. (1995). International effort helps decipher mysteries of paleoclimate from Antarctic ice cores. Eos, 76(17), 169 et 179.
Ciais, P., White, J., Jouzel, J., & Petit, J. (1995). The Origin Of Present-Day Antarctic Precipitation From Surface Snow Deuterium Excess Data. Journal Of Geophysical Research-Atmospheres, 100(D9), 18917–18927.
Abstract: The deuterium excess (d) is defined as a linear combination of the D/H and O-18/O-16 ratios in natural waters. We present an interpretation of deuterium excess data in surface Antarctic snow, using an isotopic model to derive information on the origin of present-day Antarctic precipitation. The data come from near the coast (D47, Adelie Land) and from inland (south pole, 1000 km from the sea). The one-dimensional isotopic model belongs to the Rayleigh family but fully accounts for mixed cloud processes between 0 degrees C and -30 degrees C. Modeling d in polar snowfalls meets the problem of a large sensitivity tp the saturation conditions prevailing at snow formation. Therefore we decided to tune the saturation in the model in order to yield realistic mean d values, but we use the seasonal phase of d versus delta, which is less sensitive to the saturation conditions, as an independent validation of the model predictions. Both inland and near the coast, our model can simulate the observed phase between d and delta in snow with moisture of subtropical origin (40 degrees-20 degrees S). Although we do not treat specifically storm precipitation near the coast, this study indicates that the observed phase between d and delta brings up a new validation of isotopic models. It supports a distant vapor source for large-scale precipitation delivered to the Antarctic continent.
Jouzel, J., Vaikmae, R., Petit, J., Martin, M., Duclos, Y., Stievenard, M., et al. (1995). The 2-Step Shape And Timing Of The Last Deglaciation In Antarctica. Climate Dynamics, 11(3), 151–161.
Abstract: The two-step character of the last deglaciation is well recognized in Western Europe, in Greenland and in the North Atlantic. For example, in Greenland, a gradual temperature decrease started at the Bolling (B) around 14.5 ky BP, spanned through the Allerod (A) and was followed by the cold Younger Dryas (YD) event which terminated abruptly around 11.5 ky BP. Recent results suggest that this BA/YD sequence may have extended throughout all the Northern Hemisphere but the evidence of a late transition cooling is still poor for the Southern Hemisphere. Here we present a detailed isotopic record analyzed in a new ice core drilled at Dome B in East Antarctica that fully demonstrates the existence of an Antarctic cold reversal (ACR), These results suggest that the two-step shape of the last deglaciation has a worldwide character but they also point to noticeable interhemispheric differences, Thus, the coldest part of the ACR, which shows a temperature drop about three times weaker than that recorded during the YD in Greenland, may have preceded the YD. Antarctica did not experienced abrupt changes and the two warming periods started there before they started in Greenland. The links between Southern and Northern Hemisphere climates throughout this period are discussed in the light of additional information derived from the Antarctic dust record.
Rin, J., Qin, D., Petit, J., Jouzel, J., Wang, W., Liu, C., et al. (1995). Glaciological Studies On Nelson Island, South-Shetland Islands, Antarctica. Journal Of Glaciology, 41(138), 408–412.
Abstract: The ice cap on Nelson Island in the South Shetland Islands, West Antarctica, was studied between 1985 and 1989. The ice cap has an average thickness of 120 m, it is temperate, exists under the sub-Antarctic maritime climate and almost completely covers the island. Owing to intense percolation of meltwater land, to some extent, liquid precipitation, the snow-firn layer is in the soaked facies with a firn-ice transition at a depth of 25-26 m at the summit. A force-balance model suggests that the ice is almost linearly viscous but has a high viscosity. The model further suggests that basal sliding makes a larger contribution to the ice movement than does ice deformation. From 1970 to 1988, the average accumulation rate was 120 kg m(-2) a(-1) at the centre, and between 1985 and 1989 the equilibrium-line elevation averaged 110 m a.s.l. Analysis of chemical impurities in the surface snow suggests that the precipitation source is mainly local marine air masses find that human activity has already exerted a detectable influence on the local environment.
Bareille, G., Grousset, F., Labracherie, M., Labeyrie, L., & Petit, J. (1994). Origin Of Detrital Fluxes In The Southeast Indian-Ocean During The Last Climatic Cycles. Paleoceanography, 9(6), 799–819.
Abstract: Because of a close relationship between detrital flux variations and magnetic susceptibility (MS) flux (MS cm(-3) of bulk sediment multiplied by the linear sedimentation rate) variations in the southeast Indian basin of the southern ocean, MS flux profiles have been used to examine the spatial and temporal detrital flux changes in this basin during the last climatic cycle. Results indicate a general increase in detrital material input during the coldest periods, suggesting a widespread phenomenon, at least on the basin scale. Mineralogical data, geochemical data, and Sr-87/Sr-86 isotopic ratios have been used to determine the origin and transport mechanisms responsible for increased detrital flux during glacial periods. Mineralogical and geochemical data show that these glacial ''highs'' are due to increases in both Kerguelen-Crozet volcanic and Antarctic detrital inputs. The Sr-87/Sr-86 isotopic composition of the >45-mu m fraction indicates that the Kerguelen-Crozet province contributes to at least 50% of the coarse particule input to the west. This contribution decreases eastward to reach less than 10%. These tracers clearly indicate that the Crozet-Kerguelen province was a major source region of detrital in the western part of the basin during glacial times. In contrast, material of Antarctic origin is well represented in the whole basin (fine and coarse fractions). Because of the minor amount of coarse particles in the sediments, volcanic particles from Kerguelen and crustal particles from Antarctica have most probably been transported by the Antarctic bottom water current and/or the Circumpolar deepwater current during glacial periods as is the case today. Nevertheless, the presence of coarse particles even in low amount suggests also a transport by ice rafting (sea-ice and icebergs), originated from both Kerguelen and Antarctic sources. However, the relative importance of both hydrographic and ice-rafting modes of transport cannot be identified accurately with our data. During low sea level stands (glacial maximum periods), increasing instability and erosion of the continental platform and shallow plateaus could have resulted in a more efficient transfer of crustal and volcano-detrital material to the Southeast Indian basin. At the same time, extension of the grounded ice shelves over the continental margins and increase in the erosion rate of the Antarctic ice sheet could have induced a greater input of ice rafted detritus (IRD) to southern ocean basins. Enhancement of the circumpolar deepwater current strength might have also carried a more important flux of detrital material from Kerguelen. However, an increase in the bottom water flow is not necessarily required.
|Ciais, P., Jouzel, J., Petit, J. - R., & White, J. W. C. (1994). Holocene temperature variations inferred from six Antarctic ice cores. Annals of Glaciology, 20, 427–436.
Dahe, Q., Petit, J., Jouzel, J., & Stievenard, M. (1994). Distribution Of Stable Isotopes In Surface Snow Along The Route Of The 1990 International Trans-Antarctica Expedition. Journal Of Glaciology, 40(134), 107–118.
Abstract: This paper presents the distribution of average deltaD and deltaO-18 values for the top 1 m of surface snow for a large area of Antarctica. The samples were collected on the 1990 International Trans-Antarctica Expedition which crossed the continent from the northern tip of the Antarctic Peninsula to Mirny Station. The empirical relationships between the isotopes, temperature and elevation are computed. The slopes of deltaD with respect to the surface temperature for the segments west (Patriot Hills-Vostok) and east of Vostok (Komsomolskaya-Mirny) are not significantly different to that observed between Dumont d'Urville and Dome C (Lorius and Merlivat, 1977) which are often used to interpret deep ice-core isotopic profiles. There is, however, a noticeable shift between the two regression lines with, for a given temperature higher isotopic values west of Vostok. The deuterium excess values (d = deltaD – 8 x deltaO-18) increase sharply at 3000 m a.s.l. on the plateau, confirming the results of Petit and others (1991).
Delmas, R., & Petit, J. (1994). Present Antarctic Aerosol Composition – A Memory Of Ice-Age Atmospheric Dust. Geophysical Research Letters, 21(10), 879–882.
Abstract: The data obtained from the chemical analysis (Na, Al, and Ca concentrations) of deep Antarctic ice cores has been reexamined. The correlations found between the concentrations of these elements suggest that the Patagonian continental shelf was the dominant aerosol source during the last ice age, the dust being an intimate mixture of marine clay and carbonates. In addition, it is proposed that sea salt deposited on the continental shelf sediments during drop in sea level was emitted and transported jointly with this dust. The present Antarctic aerosol composition is very similar to the one deduced from ice core studies for glacial climatic conditions. It is concluded that present Antarctic aerosol originates mainly from ice age aeolian deposits in South American cold deserts.
|Jouzel, J., Lorius, C., Petit, J. - R., Ritz, C., Stievenard, M., Yiou, P., et al. (1994). The climatic record from Antarctic ice now extends back to 220 ky BP. NATO ASI Series, 122, 213–237.
Jull, A., Lal, D., Donahue, D., Mayewski, P., Lorius, C., Raynaud, D., et al. (1994). Measurements Of Cosmic-Ray-Produced C-14 In Firn And Ice From Antarctica. Nuclear Instruments & Methods In Physics Research Section B-Beam Interactions With Materials And Atoms, 92(1-4), 326–330.
Abstract: We have studied the levels of C-14 in firn and ice from two regions accumulating ice in Antarctica, Dome C, and Newall Glacier. The observed concentrations indicate variable amounts of in-situ C-14 from cosmic-ray spallation of oxygen. C-14 appears to be produced as both CO and CO2 in variable amounts, but our results suggest rapid conversion of (CO)-C-14 to (CO2)-C-14. Much of the in-situ C-14 is retained which results in a significant modification of the C-14/C-12 in ice derived from trapping of air at and below the firn-ice transition zone. This means that direct dating of accumulating ice cannot be used without correction for the in-situ C-14. In Newall ice, we see some evidence for an enhancement in in-situ C-14 at or near the time of the Maunder Minimum. Results for Dome C firn and ice indicate higher levels of in-situ C-14 in older ice. This is due either to a reduced accumulation rate in the past, or possible variations in cosmogenic C-14 production. The levels of in-situ C-14 in firn and ice, and its impact on C-14 dates on trapped CO2 in ice are discussed.
|Tchistiakov, V. K., Kracilev, A., Lipenkov, V. Y., Balestrieri, J. - P., Rado, C., & Petit, J. - R. (1994). Behavior of a deep hole drilled in ice at Vostok Station. Memories of the National Institute of Polar Research, Spec. Issue(49), 247–255.
Jouzel, J., Barkov, N., Barnola, J., Bender, M., Chappellaz, J., Genthon, C., et al. (1993). Extending The Vostok Ice-Core Record Of Paleoclimate To The Penultimate Glacial Period. Nature, 364(6436), 407–412.
Abstract: The ice-core record of local temperature, dust accumulation and air composition at Vostok station, Antarctica, now extends back to the penultimate glacial period (approximately 140-200 kyr ago) and the end of the preceding interglacial. This yields a new glaciological timescale for the whole record, which is consistent with ocean records. Temperatures at Vostok appear to have been more uniformly cold in the penultimate glacial period than in the most recent one. Concentrations of CO2 and CH4 Correlate well with temperature throughout the record.
Qin, D., Ren, J., Wang, W., Petit, J., Jouzel, J., & Stieverard, M. (1993). Distribution Of Delta-D In 25-Cm Surface Snow Along Trans-Antarctic Route .2. The 1990 International Trans-Antarctic Expedition Glaciological Research. Science In China Series B-Chemistry, 36(3), 375–384.
Abstract: On the way of the ''1990 International Trans-Antarctic Expedition'', the first author of this paper, the Chinese member of the expedition, collected 104 snow samples in 25-cm surface snow along a 5986-km route on Antarctic ice sheet from west to east. The geographical distribution of deltaD across the Antarctica by the longest route is obtained from stable isotope analysis for the first time. After discussing regional differences of physical geographic conditions, maritime-continental influence, altitudes and latitudes at sampling sites, the distribution of deltaD is considered to have a close relation to latitudes, but the topographic effect is prominent in some particular regions. The mean annual temperature at sampling site and its relationship with deltaD in surface snow covering Antarctica from west to east are discussed also. The deltaD-temperature gradient from the south end of Antarctic Peninsula to Vostok obtained in this paper is very close to that in Terre Adelie Land obtained by predecessors. The snow-drift may make an important. contribution to the relatively high deltaD-temperature gradient from Vostok to Mirnyy.
Tison, J., Petit, J., Barnola, J., & Mahaney, W. (1993). Debris Entrainment At The Ice-Bedrock Interface In Sub-Freezing Temperature Conditions (Terre-Adelie, Antarctica). Journal Of Glaciology, 39(132), 303–315.
Abstract: The debris-rich ice from the bottom 6 m of the 82 m deep CAROLINE (Coastal Antarctic Record of Last Interglacial Natural Environment) ice core reaching bedrock, and from five 2 m long surface cores at Moraine Prudhomme in Terre Adelie (Antarctica) is described and compared to debris-laden ice from the core-drilling site D10. Isotopic, total-gas content, CO2 concentration and SEM investigations of embedded particles, together with ice textures and fabrics, rule out ''pressure-melting'' regelation around bed obstacles or ''freezing-on'' as possible mechanisms for the debris entrainment at the ice-bedrock interface. It is suggested that the debris entrapment by purely mechanical means (e.g. shearing) is an efficient process in forming basal ice layers (BIL) at sub-freezing temperatures. This process might be dominant at the margin of the Antarctic ice sheet where no ice shelf exists and where a ramp terminus or a buttressing coastal relief induces compressive flow.
Ciais, P., Petit, J. R., Jouzel, J., Lorius, C., Barkov, N. I., Lipenkov, V., et al. (1992). Evidence for an early Holocene climatic optimum in the Antarctic deep ice-core record. Climate Dynamics, 6(3-4), 169–177.
Abstract: In the interpretation of the Antarctic deep ice-core data, little attention has been given to the Holocene part of the records. As far as translation of the stable isotope content in terms of temperature is concerned, this can be understood because expected temperature changes may be obscured by isotopic noise of various origins and because no (14)C dating has yet been available for this type of sequence. In this article, we focus on the Dome C and Vostok cores and on a new 850-m long ice core drilled out at Komsomolska'ia by the Soviet Antarctic Expeditions. These three sites are located in East Antarctica, on the Antarctic plateau, in a region essentially undisturbed by ice-flow conditions, so that their detailed intercomparison may allow us to identify the climatically significant isotopic signal. Our results compare well with the proximal records of Southern Hemisphere high latitudes and support the existence of a warmer "climatic optimum" between 10 and 6 kay BP. Maximum temperatures are reached just at the end of the last deglaciation, which confirms previous observations at high latitudes, in contrast with later dates for the Atlantic and hypsithermal optima in Europe and North America.
Delmas, R., Kirchner, S., Palais, J., & Petit, J. (1992). 1000 Years Of Explosive Volcanism Recorded At The South-Pole. Tellus Series B-Chemical And Physical Meteorology, 44(4), 335–350.
Abstract: Cataclysmic volcanic eruptions generally disturb the global atmosphere markedly for around 2 years. During that time, long-life volcanic products (mainly H2SO4), stored in the stratosphere gradually return to the troposphere. Antarctic snow may be subsequently contaminated and acid signals recorded. The recovery of these signals along Antarctic ice cores provides a history of past volcanic events, most often of global, but sometimes of just regional, significance. Several physical and chemical techniques have been used to analyse a 1000-year ice core drilled near Amundsen-Scott Base. Acid and ultrafine ash deposits of volcanic origin have been carefully investigated. 23 major volcanic eruptions have been detected, dated and tentatively identified. The results have been compared with similar Antarctic and Greenland records. The amount of volcanic sulfate deposited in Antarctic snow, calculated and averaged over the last millennium, is, however, minor (13% of the total sulfate) in comparison with that of the marine biogenic source. The 19th century was the period of the millennium most seriously disturbed by global explosive volcanic activity. The chlorine cycle, as recorded in Antarctic ice, seems to be little affected even by such a large event as Tambora, 1815.
Gaudichet, A., Deangelis, M., Joussaume, S., Petit, J., Korotkevitch, Y., & Petrov, V. (1992). Comments On The Origin Of Dust In East Antarctica For Present And Ice-Age Conditions. Journal Of Atmospheric Chemistry, 14(1-4), 129–142.
Abstract: We have studied the distribution of 327 clay mineral particles retrieved from four Antarctic ice samples corresponding to present and Last Glacial Maximum (LGM) climate conditions. Illite, chlorite, smectite and kaolinite were identified in all samples. Focusing on kaolinite, because of its use as a possible tracer of low latitude soils, we find a significantly smaller amount for LGM samples while the dust concentration in snow during the LGM was about 30 times higher than for present climate conditions. This can be interpreted as change in the contribution of the Australian source with climate. A second approach was based on the modeling of the desert dust cycle using an Atmospheric General Circulation Model (AGCM) under both present-day and ice age conditions. Unlike mineralogical results, the model suggests the prevalence of the Australian dust source in the deposits over East Antarctica under both present-day and LGM climate conditions. However the model fails to reproduce the strong increase in dust deposits during the LGM. This discrepancy could be partly due to the lack of a higher latitude dust source in the model. The stronger dust input recorded in ice cores for the LGM could be related to an additional active high latitude source (possibly close to South America) overlapping the atmospheric background coming from low latitude areas.
Grousset, F., Biscaye, P., Revel, M., Petit, J., Pye, K., Joussaume, S., et al. (1992). Antarctic (Dome C) Ice-Core Dust At 18 Ky Bp – Isotopic Constraints On Origins. Earth And Planetary Science Letters, 111(1), 175–182.
Abstract: We have determined the source area from which dusts from the Last Glacial Maximum (LGM) section of the Dome C ice core were derived, by comparing their strontium and neodymium isotopic ratios with those of samples from potential source areas. The Sr-87/Sr-86 and Nd-143/Nd-144 isotope ratios of the dusts deposited almost-equal-to 18 k.y. B.P. at the East Antarctic Dome C site were compared with potential Antarctic, Australian, southern African and South American sources. The isotope ratios clearly define the Patagonian provenance of the dust, with the other potential source areas being, at most, minor contributors. Contributions by volcanic ash and tephra to the dust sample were also determined to be minimal, based on the patterns of rare earth elements. Knowing the source of the dusts places constraints on the aeolian trajectory by which it was transported to Antarctica, and this serves as a test of the simulation of southern hemispheric circulation by atmospheric global circulation models during the LGM.
|Jouzel, J., Petit, J. - R., Barkov, N. I., Barnola, J. - M., Chappellaz, J., Ciais, P., et al. (1992). The last deglaciation in Antarctica : further evidence of a "younger Dryas" type climatic event.
|Raisbeck, G., Yiou, F., Jouzel, J., Petit, J. - R., Barkov, N. I., & Bard, E. (1992). 10Be deposition at Vostok, Antarctica during the last 50,000 years and its relationship to possible cismogenic production variations during this period. (pp. 127–139). Nato Asi Series, 12. Springer Verlag.
|Jouzel, J., Petit, J. - R., Chappellaz, J., & Barnola, J. - M. (1991). The deglaciation in Antarctica ; evidence of a younger dryas type climatic event. Glaciers-Ocean-Atmosphere interaction. Iahs, 208, 1269–1283.
|Kotlyakov, V. M., Nikolayev, V. I., Korotkevich, Y. N., Petrov, V. N., Barkov, N. I., Lipenkov, V. Y., et al. (1991). Global changes over the last climatic cycle from Antarctic ice core records. Iahs, 208, 15–2.
Petit, J., White, J., Young, N., Jouzel, J., & Korotkevich, Y. (1991). Deuterium Excess In Recent Antarctic Snow. Journal Of Geophysical Research-Atmospheres, 96(D3), 5113–5122.
Abstract: Deuterium excess (d = delta-D – 8 * delta-O-18) values in surface snow are presented for central and east Antarctica. The samples are primarily from Soviet, French, and Australian traverses. The d values exhibit a large change going from coastal sites to high-altitude sites on the ice sheet. The d values are relatively constant at 3 to 6% from the coast to an altitude of 2500 m, and at higher elevations d increases steadily to values of 16 to 18 parts-per-thousand at Vostok and Plateau Station. The data is modeled as d versus delta-D using the kinetic Rayleigh model for isotopes in precipitation developed by Jouzel and Merlivat. The model accounts for kinetic fractionation during evaporation into undersaturated air over the ocean and during snow formation in < -10-degrees-C clouds where vapor is supersaturated with respect to snow. The overall pattern of d versus delta-D can be fit well with a supersaturation function which increases linearly with decreasing temperature and which predicts reasonable values of the supersaturation. Vapor originating from 20-degrees to 60-degrees-S was tested with different supersaturation functions. The data could only be fit with moisture originating from 30-degrees to 40-degrees-S, indicating that these latitudes are the main source of vapor for snow falling in Antarctica. The conclusion of a mid-latitude vapor source for polar snow agrees with the analysis of d and delta-O-18 seasonal cycles in Greenland snow performed by Johnsen and coworkers. The model was also tested with moisture simultaneously originating from all latitudes from 30-degrees-S to the Antarctic coast. The addition of up to 20% of moisture evaporated from latitudes south of 50-degrees, and 5% from latitudes south of 60-degrees, is compatible with low d values occasionally observed in snow near the coast. The conclusion of a "local moisture" effect for coastal and near coastal (< 2000 m elevation) snowfall supports a similar conclusion by Saigne and Legrand from their analysis of methanesulphonic acid in Antarctic snow. Finally, the effects of changes in the sea surface temperature and changes in oceanic humidity on the d values observed in Antarctic snow are greatly modified during the precipitation process. Hence the interpretation of d values in ice cores should be done in the context of a precipitation model.
|Jouzel, J., Petit, J. - R., & Raynaud, D. (1990). Paleoclimatic information from ice cores. Transactions of the Royal Society of Edinburg : Earth Sciences, 81, 349–355.
|Petit, J., Mounier, L., Jouzel, J., Korotkevich, Y., Kotlyakov, V., & Lorius, C. (1990). Palaeoclimatological And Chronological Implications Of The Vostok Core Dust Record. Nature, 343(6253), 56–58.
|Raisbeck, G., Yiou, P., Jouzel, J., & Petit, J. - R. (1990). 10Be and d2H in polar ice cores as a probe of the solar variability's influence of climate. Philosophical Transactions of the Royal Society of London, A330, 463–470.
|Yao, T., Petit, J., & Lorius, C. (1990). The Microparticle Concentration Measurement And Its Climatic Implications In An Ice Core From Coast Area, Antarctica. Science In China Series B-Chemistry, 33(9), 1102–1109.
|Yao, T. D., Petit, J. - R., Jouzel, J., Lorius, C., & Duval, P. (1990). Climatic record from an ice margin area in East Antarctica. Annals of Glaciology, 14, 323–327.
|Jouzel, J., Barkov, N. I., Barnola, J. - M., Genthon, C., Korotkevich, Y. S., Kotlyakov, V. M., et al. (1989). Global change over the last climatic cycle from the Vostok ice core record (Antarctica). Quaternary International, 2, 15–24.
|Jouzel, J., Raisbeck, G., Benoist, J., Yiou, F., Lorius, C., Raynaud, D., et al. (1989). A Comparison Of Deep Antarctic Ice Cores And Their Implications For Climate Between 65,000 And 15,000 Years Ago. Quaternary Research, 31(2), 135–150.
|Lorius, C., Barnola, J. - M., Petit, J. - R., Raynaud, D., Ritz, C., Barkov, N. I., et al. (1989). Long-term climatic and environmental records from Antarctic ice. International Union of Geodesy and Geophysics and American Geophysical Union, , 11–16.
|Burckle, L. H., Gayley, R. I., Ram, M., & Petit, J. - R. (1988). Diatoms in Antarctic ice cores : some implications for the glacial history of Antarctica. Geology, 16, 326–329.
|Gaudichet, A., Deangelis, M., Lefevre, R., Petit, J., Korotkevitch, Y., & Petrov, V. (1988). Mineralogy Of Insoluble Particles In The Vostok Antarctic Ice Core Over The Last Climatic Cycle (150-Kyr). Geophysical Research Letters, 15(13), 1471–1474.
|Jouzel, J., Lorius, C., Petit, J. - R., Genthon, C., Barkov, N. I., & Korotkevich, Y. N. (1988). Climatic interpretation of a continuous deuterium profile obtained from the Vostok ice core, Antarctica (160.000 years). Annals of Glaciology, 10, 206–207.
|Petit, J., Duval, P., & Lorius, C. (1988). Long-Term Climate Changes From Crystal-Growth – Reply. Nature, 332(6165), 593.
|Petit, J. - R., Gaudichet, A., de Angelis, M., Mounier, L., & Lefevre, R. (1988). Continentally derived microparticles in central antarctic ice core samples. Antarctic Climate Research, 3, 6–9.
|Ram, M., Gayley, R. I., & Petit, J. - R. (1988). Insoluble particles in Antarctic ice : background aerosol size distribution and diatom concentration. Journal of Geophysical Research, 93(D7), 8378–8382.
|Jouzel, J., Lorius, C., Petit, J. - R., Genthon, C., Barkov, N. I., Kotlyakov, V. M., et al. (1987). Vostok ice core : a continuous isotope temperature record over the last climatic cycle (160,000 years). Nature, 329(6138), 403–408.
|Legrand, M., Petit, J., & Korotkevich, Y. (1987). Dc Conductivity Of Antarctic Ice In Relation To Its Chemistry. Journal De Physique, 48(C-1), 605–611.
|Petit, J., Duval, P., & Lorius, C. (1987). Long-Term Climatic Changes Indicated By Crystal-Growth In Polar Ice. Nature, 326(6108), 62–64.
|Petit, J., Duval, P., & Lorius, C. (1987). Temperature-Dependence Of The Crystal-Growth Rate In Polar Glaciers. Journal De Physique, 48(C-1), 661–662.
|Gaudichet, A., Petit, J. - R., Lefevre, R., & Lorius, C. (1986). An investigation by analytical transmission electron microscopy of individual insoluble microparticles from Antarctic (Dome C) ice core samples. Tellus B, 38, 250–261.
|De Angelis, M., Legrand, M., & Petit, J. R. (1984). Soluble and insoluble impurities along the 950 m deep Vostok ice core (Antarctica) Climatic implications. Journal of Atmospheric Chemistry, 1, 215–239.
|Joussaume, S., Petit, J. - R., Rasool, I., & Sadourny, R. (1984). Simulation of dust cycles in an atmospheric general circulation model. Annals of Glaciology, 5, 204–207.
|Lorius, C., Raynaud, D., Petit, J., Jouzel, J., & Merlivat, L. (1984). Late-Glacial Maximum-Holocene Atmospheric And Ice-Thickness Changes From Antarctic Ice-Core Studies. Annals Of Glaciology, 5, 88–94.
|Young, N. W., Raynaud, D., de Angelis, M., Petit, J. - R., & Lorius, C. (1984). Past changes of Antarctic ice sheet in Terre Adelie as deduced from ice core data and ice modelling. Annals of Glaciology, 5, 239.
|Jouzel, J., Merlivat, L., Petit, J., & Lorius, C. (1983). Climatic Information Over The Last Century Deduced From A Detailed Isotopic Record In The South-Pole Snow. Journal Of Geophysical Research-Oceans And Atmospheres, 88(Nc4), 2693–2703.
|Petit, J. - R., Ezat, U., Barkov, N. I., & Petrov, V. N. (1983). Identification of quartz microparticles in 20,000 BP Antarctic ice samples : a signature of the last glacial environment. Scanning Electron Microscopy, Iv, 1627–1633.
|Royer, A., Deangelis, M., & Petit, J. (1983). A 30000 Year Record Of Physical And Optical-Properties Of Microparticles From An East Antarctic Ice Core And Implications For Paleoclimate Reconstruction Models. Climatic Change, 5(4), 381–412.
|Briat, M., Jouzel, J., Lorius, C., Merlivat, L., Petit, J. - R., & Raynaud, D. (1982). Ice age atmospheric CO2 , aerosols and relative humidity as deduced from ice core studies : data for climate modelling. Eos, 63(51).
|Briat, M., Royer, A., Petit, J. - R., & Lorius, C. (1982). Late glacial eolian continental dust in the Dome C ice core : additional evidence from individual microparticle analysis. Annals of Glaciology, 3, 27–31.
|Petit, J. - R. (1982). Etude des aérosols insoblubles déposés dans la neige a,tarctique ; contribution à la datation des dépôts glaciaires et la reconstitution du paléoenvironnement atmosphériqueThèse d'Etat de l'Université Scientifique et Médicale de Grenoble. Ph.D. thesis, , .
|Petit, J. - R., Jouzel, J., Pourchet, M., & Merlivat, L. (1982). A detailed study of snow accumulation and stable isotope content in Dome C (Antarctica). Journal of Geophysical Research, 87(C6), 4301–4308.
|Petit, J., Briat, M., & Royer, A. (1981). Ice-Age Aerosol Content From East Antarctic Ice Core Samples And Past Wind Strength. Nature, 293(5831), 391–394.
|Thompson, L. G., Mosley-Thompson, E., & Petit, J. - R. (1981). Glaciological interpretation from the French 905 m ice core, Dome C, Antarctica. Iahs, 131, 227–234.
|Lambert, G., Petit, J. - R., Pourchet, M., Sanak, J., & Lorius, C. (1979). Variation récente de la neige sur la calotte Antarctique. Pub CNES, , 387–389.
|Thompson, L. G., Mosley-Thompson, E., & Petit, J. - R. (1979). Glaciological interpretation of microparticle concentration from the French 905 m Dome C Antarctic core. Iahs, (131), 227–234.
|Petit, J., & Duval, P. (1976). Thermoluminescence Of Ice – Effects Of Plastic-Deformation. Solid State Communications, 19(5), 475–477.
|Vallon, M., Petit, J. - R., & Fabre, B. (1976). Study of an ice core to the bedrock in the accumulation zone an alpine glacier. Journal of Glaciology, 17(75), 11–28.
|Petit, J. - R. (1972). Bilans annuels, transformation du névé en glace, teneur en eau de la glace profonde (Vallée Blanche supérieure, Massif du Mont-Blanc)Thèse de 3e cycle de l'Université Scientifique et Médicale de Grenoble. Ph.D. thesis, , .
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