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= = Tropical glaciers = =
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Tropical glaciers are located between the Tropic of Cancer and the Tropic of Capricorn , in the region that lies 23 ° 26 ′ 22 ″ north or south of the equator . Strictly , a tropical glacier is located within the astronomical tropics ; the area where the annual temperature variation is less than the daily variation , and is within the oscillation area of the Intertropical Convergence Zone .
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Tropical glaciers are the most uncommon of all glaciers for a variety of reasons . Firstly , the regions are the warmest part of the planet . Secondly , the seasonal change is minimal with temperatures warm year round , resulting in a lack of a colder winter season in which snow and ice can accumulate . Thirdly , few taller mountains exist in these regions upon which enough cold air exists for the establishment of glaciers . Overall , tropical glaciers are smaller than those found elsewhere and are the most likely glaciers to show rapid response to changing climate patterns . A small temperature increase of only a few degrees can have almost immediate and adverse effect on tropical glaciers .
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Near the Equator , ice is still found in East Africa , the Andes of South America and New Guinea . The retreat of equatorial glaciers has been documented via maps and photographs covering the period from the late 1800s to nearly the present . 99 @.@ 64 % of tropical glaciers are in Andean mountains of South America , 0 @.@ 25 % on the African glaciers of Rwenzori , Mount Kenya and Kilimanjaro , and 0 @.@ 11 % in the Irian Jaya region in New Guinea .
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= = = Africa = = =
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Almost the entirety of Africa is located within tropical and subtropical climate zones . Its glaciers are found only in two isolated ranges and the Ruwenzori Range . Kilimanjaro , at 5 @,@ 895 m ( 19 @,@ 341 ft ) , is the highest peak on the continent . Since 1912 the glacier cover on the summit of Kilimanjaro has apparently retreated 75 % , and the volume of glacial ice is now 80 % less than it was a century ago due to both retreat and thinning . In the 14 @-@ year period from 1984 to 1998 , one section of the glacier atop the mountain receded 300 m ( 980 ft ) . A 2002 study determined that if current conditions continue , the glaciers atop Kilimanjaro will disappear sometime between 2015 and 2020 . A March 2005 report indicated that there is almost no remaining glacial ice on the mountain , and it is the first time in 11 @,@ 000 years that barren ground has been exposed on portions of the summit . Researchers reported Kilimanjaro 's glacier retreat was due to a combination of increased sublimation and decreased snow fall .
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The Furtwängler Glacier is located near the summit of Kilimanjaro . Between 1976 and 2000 , the area of Furtwängler Glacier was cut almost in half , from 113 @,@ 000 m2 ( 1 @,@ 220 @,@ 000 sq ft ) to 60 @,@ 000 m2 ( 650 @,@ 000 sq ft ) . During fieldwork conducted early in 2006 , scientists discovered a large hole near the center of the glacier . This hole , extending through the 6 m ( 20 ft ) remaining thickness of the glacier to the underlying rock , was expected to grow and split the glacier in two by 2007 .
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To the north of Kilimanjaro lies Mount Kenya , which at 5 @,@ 199 m ( 17 @,@ 057 ft ) is the second tallest mountain on the continent . Mount Kenya has a number of small glaciers that have lost at least 45 % of their mass since the middle of the 20th century . According to research compiled by the U.S. Geological Survey ( USGS ) , there were eighteen glaciers atop Mount Kenya in 1900 , and by 1986 only eleven remained . The total area covered by glaciers was 1 @.@ 6 km2 ( 0 @.@ 62 sq mi ) in 1900 , however by the year 2000 only about 25 % , or 0 @.@ 4 km2 ( 0 @.@ 15 sq mi ) remained . To the west of Mounts Kilimanjaro and Kenya , the Ruwenzori Range rises to 5 @,@ 109 m ( 16 @,@ 762 ft ) . Photographic evidence indicates a marked reduction in glacially covered areas over the past century . In the 35 @-@ year period between 1955 and 1990 , glaciers on the Rwenzori Mountains receded about 40 % . It is expected that due to their proximity to the heavy moisture of the Congo region , the glaciers in the Ruwenzori Range may recede at a slower rate than those on Kilimanjaro or in Kenya .
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= = = South America = = =
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A study by glaciologists of two small glaciers in South America reveals another retreat . More than 80 % of all glacial ice in the northern Andes is concentrated on the highest peaks in small plains of approximately 1 km2 ( 0 @.@ 39 sq mi ) in size . A 1992 to 1998 observation of the Chacaltaya Glacier in Bolivia and <unk> Glacier in Ecuador indicate that between 0 @.@ 6 m ( 2 @.@ 0 ft ) and 1 @.@ 9 m ( 6 @.@ 2 ft ) of ice was lost per year on each glacier . Figures for Chacaltaya show a loss of 67 % of its volume and 40 % of its thickness over the same period . Chacaltaya Glacier has lost 90 % of its mass since 1940 and is expected to disappear altogether sometime between 2010 and 2015 . <unk> is also reported to have lost 40 % of its surface area between 1979 and 2007 . Research also indicates that since the mid @-@ 1980s , the rate of retreat for both of these glaciers has been increasing . In Colombia , the glaciers atop Nevado del Ruiz have lost more than half their area in the last 40 years . Further south in Peru , the Andes are at a higher altitude overall , and there are approximately 722 glaciers covering an area of 723 km2 ( 279 sq mi ) .
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Research in the region has been less extensive but indicates an overall recline of 7 % between 1977 and 1983 . The Quelccaya Ice Cap is the largest tropical icecap in the world , and all of the outlet glaciers from the icecap are retreating . In the case of <unk> <unk> Glacier , which is one of <unk> ' outlet glaciers , the rate of retreat had reached 155 m ( 509 ft ) per year during the three @-@ year period of 1995 to 1998 . The melting ice has formed a large lake at the front of the glacier since 1983 , and bare ground has been exposed for the first time in thousands of years .
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= = = Oceania = = =
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Jan Carstensz 's 1623 report of glaciers covering the equatorial mountains of New Guinea was originally met with ridicule , but in the early 20th century at least five subranges of the <unk> Mountains ( meaning " Snowy Mountains " ) were indeed still found to be covered with large ice caps . Due to the location of the island within the tropical zone , there is little to no seasonal variation in temperature . The tropical location has a predictably steady level of rain and snowfall , as well as cloud cover year round , and there has been no noticeable change in the amount of moisture which has fallen during the 20th century .
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In 1913 , 4 @,@ 550 m ( 14 @,@ 930 ft ) high Prins Hendrik peaks ( now Puncak Yamin ) was named and reported to have " eternal " snow , but this observation was never repeated . The ice cap of 4 @,@ 720 m ( 15 @,@ 490 ft ) Wilhelmina Peaks , which reached below 4 @,@ 400 m ( 14 @,@ 400 ft ) in 1909 , vanished between 1939 and 1963 . The Mandala / Juliana ice cap disappeared in the <unk> and the Idenburg glacier on <unk> <unk> dried up in 2003 . This leaves only the remnants of the once continuous icecap on New Guinea 's highest mountain , Mount Carstensz with the 4 @,@ 884 m ( 16 @,@ 024 ft ) high Puncak Jaya summit , which is estimated to have had an area of 20 km2 ( 7 @.@ 7 sq mi ) in 1850 .
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For this mountain there is photographic evidence of massive glacial retreat since the region was first extensively explored by airplane in 1936 in preparation for the peak 's first ascent ( see e.g. [ 1 ] ) . Between then and 2010 , the mountain lost 80 percent of its ice — two @-@ thirds of which since another scientific expedition in the 1970s . That research between 1973 and 1976 showed glacier retreat for the <unk> Glacier of 200 m ( 660 ft ) while the Carstensz Glacier lost 50 m ( 160 ft ) . The Northwall Firn , the largest remnant of the icecap that once was atop Puncak Jaya , has itself split into two separate glaciers after 1942 . <unk> satellite imagery of the New Guinean glaciers indicated that by 2002 only 2 @.@ 1 km2 ( 0 @.@ 81 sq mi ) glacial area remained , that in the two years from 2000 to 2002 , the East Northwall Firn had lost 4 @.@ 5 % , the West Northwall Firn 19 @.@ 4 % and the Carstensz 6 @.@ 8 % of their glacial mass , and that sometime between 1994 and 2000 , the <unk> Glacier had disappeared altogether . An expedition to the remaining glaciers on Puncak Jaya in 2010 discovered that the ice on the glaciers there is about 32 metres ( 105 ft ) thick and thinning at a rate of 7 metres ( 23 ft ) annually . At that rate , the remaining glaciers are expected to last only to the year 2015 .
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= = Polar regions = =
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Despite their proximity and importance to human populations , the mountain and valley glaciers of tropical and mid @-@ latitude glaciers amount to only a small fraction of glacial ice on the Earth . About 99 percent of all freshwater ice is in the great ice sheets of polar and subpolar Antarctica and Greenland . These continuous continental @-@ scale ice sheets , 3 km ( 1 @.@ 9 mi ) or more in thickness , cap much of the polar and subpolar land masses . Like rivers flowing from an enormous lake , numerous outlet glaciers transport ice from the margins of the ice sheet to the ocean .
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= = = Iceland = = =
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The northern Atlantic island nation of Iceland is home to Vatnajökull , which is the largest ice cap in Europe . The <unk> glacier is one of Vatnajökull 's outlet glaciers , and receded by as much as 2 km ( 1 @.@ 2 mi ) between 1973 and 2004 . In the early 20th century , <unk> extended to within 250 m ( 820 ft ) of the ocean , but by 2004 its terminus had retreated 3 km ( 1 @.@ 9 mi ) further inland . This glacier retreat exposed a rapidly expanding lagoon , <unk> , which is filled with icebergs calved from its front . <unk> is 110 m ( 360 ft ) deep and nearly doubled its size between 1994 and 2004 . Mass @-@ balance measurements of Iceland 's glaciers show alternating positive and negative mass balance of glaciers during the period 1987 – 95 , but the mass balance has been predominantly negative since . On <unk> ice cap , mass balance has been negative each year from 1995 – 2005 .
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Most of the Icelandic glaciers retreated rapidly during the warm decades from 1930 to 1960 , slowing down as the climate cooled during the following decade , and started to advance after 1970 . The rate of advance peaked in the 1980s , after which it slowed down until about 1990 . As a consequence of rapid warming of the climate that has taken place since the mid @-@ 1980s , most glaciers in Iceland began to retreat after 1990 , and by 2000 all monitored non @-@ surge type glaciers in Iceland were retreating . An average of 45 non @-@ surging termini were monitored each year by the Icelandic <unk> Society from 2000 – 2005 .
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= = = Canada = = =
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The Canadian Arctic islands contain the largest area and volume of land ice on Earth outside of the Greenland and Antarctic Ice Sheets and is home to a number of substantial ice caps , including Penny and Barnes ice caps on Baffin Island , Bylot Ice Cap on Bylot Island , and Devon Ice Cap on Devon Island . Glaciers in the Canadian Arctic were near equilibrium between 1960 and 2000 , losing 23 Gt of ice per year between 1995 and 2000 . Since this time , Canadian Arctic glaciers have experienced a sharp increase in mass loss in response to warmer summer temperature , losing 92 Gt per year between 2007 and 2009 .
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Other studies show that between 1960 and 1999 , the Devon Ice Cap lost 67 km3 ( 16 cu mi ) of ice , mainly through thinning . All major outlet glaciers along the eastern Devon Ice Cap margin have retreated from 1 km ( 0 @.@ 62 mi ) to 3 km ( 1 @.@ 9 mi ) since 1960 . On the Hazen Plateau of Ellesmere Island , the Simmon Ice Cap has lost 47 % of its area since 1959 . If the current climatic conditions continue , the remaining glacial ice on the Hazen Plateau will be gone around 2050 . On August 13 , 2005 , the <unk> Ice Shelf broke free from the north coast of Ellesmere Island . The 66 km2 ( 25 sq mi ) ice shelf drifted into the Arctic Ocean . This followed the splitting of the Ward Hunt Ice Shelf in 2002 . The Ward Hunt has lost 90 % of its area in the last century .
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= = = Northern Europe = = =
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Arctic islands north of Norway , Finland and Russia have all shown evidence of glacier retreat . In the Svalbard archipelago , the island of Spitsbergen has numerous glaciers . Research indicates that <unk> ( Hans Glacier ) on Spitsbergen retreated 1 @.@ 4 km ( 0 @.@ 87 mi ) from 1936 to 1982 and another 400 m ( 1 @,@ 300 ft ) during the 16 @-@ year period from 1982 to 1998 . <unk> , a glacier in the King 's Bay area of Spitsbergen , has retreated approximately 2 km ( 1 @.@ 2 mi ) in the past 80 years . Since 1960 the average retreat of <unk> has been about 35 m ( 115 ft ) a year , and this average was enhanced due to an accelerated rate of retreat since 1995 . Similarly , <unk> <unk> retreated 200 m ( 660 ft ) between 1977 and 1995 . In the Novaya Zemlya archipelago north of Russia , research indicates that in 1952 there was 208 km ( 129 mi ) of glacier ice along the coast . By 1993 this had been reduced by 8 % to 198 km ( 123 mi ) of glacier coastline .
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= = = Greenland = = =
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In Greenland , glacier retreat has been observed in outlet glaciers , resulting in an increase of the ice flow rate and destabilization of the mass balance of the ice sheet that is their source . The net loss in volume and hence sea level contribution of the Greenland Ice Sheet ( GIS ) has doubled in recent years from 90 km3 ( 22 cu mi ) to 220 km3 ( 53 cu mi ) per year . Researchers also noted that the acceleration was widespread affecting almost all glaciers south of 70 N by 2005 . The period since 2000 has brought retreat to several very large glaciers that had long been stable . Three glaciers that have been researched — Helheim Glacier , Kangerdlugssuaq Glacier , and <unk> <unk> — jointly drain more than 16 % of the Greenland Ice Sheet . In the case of Helheim Glacier , researchers used satellite images to determine the movement and retreat of the glacier . Satellite images and aerial photographs from the 1950s and 1970s show that the front of the glacier had remained in the same place for decades . In 2001 the glacier began retreating rapidly , and by 2005 the glacier had retreated a total of 7 @.@ 2 km ( 4 @.@ 5 mi ) , accelerating from 20 m ( 66 ft ) per day to 35 m ( 115 ft ) per day during that period .
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<unk> <unk> in west Greenland , a major outlet glacier of the Greenland Ice Sheet , has been the fastest moving glacier in the world over the past half century . It had been moving continuously at speeds of over 24 m ( 79 ft ) per day with a stable terminus since at least 1950 . In 2002 the 12 km ( 7 @.@ 5 mi ) long floating terminus of the glacier entered a phase of rapid retreat , with the ice front breaking up and the floating terminus disintegrating and accelerating to a retreat rate of over 30 m ( 98 ft ) per day . On a shorter timescale , portions of the main trunk of Kangerdlugssuaq Glacier that were flowing at 15 m ( 49 ft ) per day from 1988 to 2001 were measured to be flowing at 40 m ( 130 ft ) per day in the summer of 2005 . Not only has Kangerdlugssuaq retreated , it has also thinned by more than 100 m ( 330 ft ) .
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The rapid thinning , acceleration and retreat of Helheim , <unk> and Kangerdlugssuaq glaciers in Greenland , all in close association with one another , suggests a common triggering mechanism , such as enhanced surface melting due to regional climate warming or a change in forces at the glacier front . The enhanced melting leading to lubrication of the glacier base has been observed to cause a small seasonal velocity increase and the release of meltwater lakes has also led to only small short term accelerations . The significant accelerations noted on the three largest glaciers began at the calving front and propagated inland and are not seasonal in nature . Thus , the primary source of outlet glacier acceleration widely observed on small and large calving glaciers in Greenland is driven by changes in dynamic forces at the glacier front , not enhanced meltwater lubrication . This was termed the <unk> Effect by Terence Hughes at the University of Maine in 1986 . Indeed , a study published in 2015 on glacial underwater topography at 3 sites found cavities , due to warm subglacial water intrusion , which has been identified as a possible dominant force for ablation ( surface erosion ) . Thus , suggests ocean temperature controls ice sheet surface runoff at specific sites . These findings also show that models underestimate the sensitivity of Greenland glaciers to ocean warming and resulting ice sheet runoff . Hence , without better modelling , new observations suggest that past projections of sea level rise attribution from the Greenland Ice Sheet require upward revision .
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= = = Antarctica = = =
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Antarctica is <unk> cold and arid . Most of the world 's freshwater ice is contained within its sheets . Its most dramatic example of glacier retreat is the loss of large sections of the Larsen Ice Shelf on the Antarctic Peninsula . The recent collapse of Wordie Ice Shelf , Prince Gustav Ice Shelf , Mueller Ice Shelf , Jones Ice Shelf , Larsen @-@ A and Larsen @-@ B Ice Shelf on the Antarctic Peninsula has raised awareness of how dynamic ice shelf systems are .
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The Antarctic sheet is the largest known single mass of ice . It covers almost 14 million km2 and some 30 million km3 of ice . Around 90 % of the fresh water on the planet 's surface is held in this area and if melted would raise sea levels by 58 metres . The continent @-@ wide average surface temperature trend of Antarctica is positive and significant at > 0 @.@ 05 ° C / decade since 1957 .
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The Antarctic sheet is divided by the Transantarctic Mountains into two unequal sections known as the East Antarctic ice sheet ( EAIS ) and the smaller West Antarctic Ice Sheet ( WAIS ) . The EAIS rests on a major land mass but the bed of the WAIS is , in places , more than 2 @,@ 500 metres below sea level . It would be seabed if the ice sheet were not there . The WAIS is classified as a marine @-@ based ice sheet , meaning that its bed lies below sea level and its edges flow into floating ice shelves . The WAIS is bounded by the Ross Ice Shelf , the <unk> Ice Shelf , and outlet glaciers that drain into the Amundsen Sea .
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Ice shelves are not stable when surface melting occurs , and the collapse of Larsen Ice Shelf has been caused by warmer melt season temperatures that have led to surface melting and the formation of shallow ponds of water on the ice shelf . The Larsen Ice Shelf lost 2 @,@ 500 km2 ( 970 sq mi ) of its area from 1995 to 2001 . In a 35 @-@ day period beginning on January 31 , 2002 , about 3 @,@ 250 km2 ( 1 @,@ 250 sq mi ) of shelf area disintegrated . The ice shelf is now 40 % the size of its previous minimum stable extent . In 2015 a study concluded that the remaining Larsen B ice @-@ shelf will disintegrate by the end of the decade , based on observations of faster flow and rapid thinning of glaciers in the area . Jones Ice Shelf had an area of 35 km2 ( 14 sq mi ) in the 1970s but by 2008 it had disappeared . Wordie Ice Shelf has gone from an area of 1 @,@ 500 km2 ( 580 sq mi ) in 1950 to 1 @,@ 400 km2 ( 540 sq mi ) in 2000 . Prince Gustav Ice Shelf has gone from an area of 1 @,@ 600 km2 ( 620 sq mi ) to 1 @,@ 100 km2 ( 420 sq mi ) in 2008 . After their loss the reduced buttressing of feeder glaciers has allowed the expected speed @-@ up of inland ice masses after shelf ice break @-@ up . The Ross Ice Shelf is the largest ice shelf of Antarctica ( an area of roughly 487 @,@ 000 square kilometres ( 188 @,@ 000 sq mi ) and about 800 kilometres ( 500 mi ) across : about the size of France ) . Wilkins Ice Shelf is another ice shelf that has suffered substantial retreat . The ice shelf had an area of 16 @,@ 000 km2 ( 6 @,@ 200 sq mi ) in 1998 when 1 @,@ 000 km2 ( 390 sq mi ) was lost that year . In 2007 and 2008 significant rifting developed and led to the loss of another 1 @,@ 400 km2 ( 540 sq mi ) of area and some of the calving occurred in the Austral winter . The calving seemed to have resulted from preconditioning such as thinning , possibly due to basal melt , as surface melt was not as evident , leading to a reduction in the strength of the pinning point connections . The thinner ice then experienced spreading rifts and breakup . This period culminated in the collapse of an ice bridge connecting the main ice shelf to Charcot Island leading to the loss of an additional 700 km2 ( 270 sq mi ) between February and June 2009 .
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Dakshin Gangotri Glacier , a small outlet glacier of the Antarctic ice sheet , receded at an average rate of 0 @.@ 7 m ( 2 @.@ 3 ft ) per year from 1983 to 2002 . On the Antarctic Peninsula , which is the only section of Antarctica that extends well north of the Antarctic Circle , there are hundreds of retreating glaciers . In one study of 244 glaciers on the peninsula , 212 have retreated an average of 600 m ( 2 @,@ 000 ft ) from where they were when first measured in 1953 . Pine Island Glacier , an Antarctic outflow glacier that flows into the Amundsen Sea . A study from 1998 concluded that the glacier thinned 3 @.@ 5 m ( 11 ft ) ± 0 @.@ 9 m ( 3 @.@ 0 ft ) per year and retreated a total of 5 km ( 3 @.@ 1 mi ) in 3 @.@ 8 years . The terminus of the Pine Island Glacier is a floating ice shelf , and the point at which it starts to float retreated 1 @.@ 2 km ( 0 @.@ 75 mi ) per year from 1992 to 1996 . This glacier drains a substantial portion of the West Antarctic Ice Sheet .
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A study published in 2014 found , rapid grounding line retreat in the years 1992 @-@ 2011 . Based on a study from 2005 , the greatest retreat was seen in Sjogren Glacier , which is now 13 km ( 8 @.@ 1 mi ) further inland than where it was in 1953 . There are 32 glaciers that were measured to have advanced ; however , these glaciers showed only a modest advance averaging 300 m ( 980 ft ) per glacier , which is significantly smaller than the massive retreat observed . Thwaites Glacier , which has also shown evidence of thinning , has been referred to as the weak underbelly of the West Antarctic Ice Sheet . A study published in 2014 found rapid grounding line retreat in the years 1992 @-@ 2011 . Totten Glacier , is a large glacier draining a major portion of the East Antarctic Ice Sheet . A study in 2008 concluded that Totten Glacier is currently losing mass . A study published in 2015 concluded that Totten Glacier , has the largest contribution of ice thinning rate on the East Antarctic continent , and that the thinning is driven by enhanced basal melting , because of ocean processes , and affected by <unk> activity . Additionally , warm Circumpolar Deep Water , has been observed during summer and winter months at the nearby continental shelf below 400 to 500 meters of cool Antarctic Surface Water .
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= = Effects of glacier retreat = =
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The continued retreat of glaciers will have a number of different quantitative effects . In areas that are heavily dependent on water runoff from glaciers that melt during the warmer summer months , a continuation of the current retreat will eventually deplete the glacial ice and substantially reduce or eliminate runoff . A reduction in runoff will affect the ability to irrigate crops and will reduce summer stream flows necessary to keep dams and reservoirs replenished . This situation is particularly acute for irrigation in South America , where numerous artificial lakes are filled almost exclusively by glacial melt . Central Asian countries have also been historically dependent on the seasonal glacier melt water for irrigation and drinking supplies . In Norway , the Alps , and the Pacific Northwest of North America , glacier runoff is important for hydropower .
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Some of this retreat has resulted in efforts to slow down the loss of glaciers in the Alps . To retard melting of the glaciers used by certain Austrian ski resorts , portions of the <unk> and <unk> Glaciers were partially covered with plastic . In Switzerland plastic sheeting is also used to reduce the melt of glacial ice used as ski slopes . While covering glaciers with plastic sheeting may prove advantageous to ski resorts on a small scale , this practice is not expected to be economically practical on a much larger scale .
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Many species of freshwater and saltwater plants and animals are dependent on glacier @-@ fed waters to ensure the cold water habitat to which they have adapted . Some species of freshwater fish need cold water to survive and to reproduce , and this is especially true with salmon and cutthroat trout . Reduced glacial runoff can lead to insufficient stream flow to allow these species to thrive . Alterations to the ocean currents , due to increased freshwater inputs from glacier melt , and the potential alterations to thermohaline circulation of the World Ocean , may affect existing fisheries upon which humans depend as well .
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One major concern is the increased risk of Glacial Lake Outburst Floods ( GLOF ) , which have in the past had great effect on lives and property . Glacier meltwater left behind by the retreating glacier is often held back by moraines that can be unstable and have been known to collapse if breached or displaced by earthquakes , landslides or avalanches . If the terminal moraine is not strong enough to hold the rising water behind it , it can burst , leading to a massive localized flood . The likelihood of such events is rising due to the creation and expansion of glacial lakes resulting from glacier retreat . Past floods have been deadly and have resulted in enormous property damage . Towns and villages in steep , narrow valleys that are downstream from glacial lakes are at the greatest risk . In 1892 a GLOF released some 200 @,@ 000 m3 ( 260 @,@ 000 cu yd ) of water from the lake of the Glacier de Tête Rousse , resulting in the deaths of 200 people in the French town of Saint @-@ Gervais @-@ les @-@ Bains . GLOFs have been known to occur in every region of the world where glaciers are located . Continued glacier retreat is expected to create and expand glacial lakes , increasing the danger of future GLOFs .
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The potential for major sea level rise depends mostly on a significant melting of the polar ice caps of Greenland and Antarctica , as this is where the vast majority of glacial ice is located . If all the ice on the polar ice caps were to melt away , the oceans of the world would rise an estimated 70 m ( 230 ft ) . Although previously it was thought that the polar ice caps were not contributing heavily to sea level rise ( IPCC 2007 ) , recent studies have confirmed that both Antarctica and Greenland are contributing 0 @.@ 5 millimetres ( 0 @.@ 020 in ) a year each to global sea level rise . The fact that the IPCC estimates did not include rapid ice sheet decay into their sea level predictions makes it difficult to ascertain a plausible estimate for sea level rise but recent studies find that the minimum sea level rise will be around 0 @.@ 8 metres ( 2 @.@ 6 ft ) by 2100 .
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= Livermorium =
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Livermorium is a synthetic superheavy element with symbol Lv and atomic number 116 . It is an extremely radioactive element that has only been created in the laboratory and has not been observed in nature . The element is named after the Lawrence Livermore National Laboratory in the United States , which collaborated with the Joint Institute for Nuclear Research in Dubna , Russia to discover livermorium in 2000 . The name of the laboratory honors the city of Livermore , California where it is located , which in turn was named after the rancher and landowner Robert Livermore . The name was adopted by IUPAC on May 30 , 2012 . Four isotopes of livermorium are known , with mass numbers between 290 and 293 inclusive ; the longest @-@ lived among them is livermorium @-@ 293 with a half @-@ life of about 60 milliseconds .
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In the periodic table , it is a p @-@ block transactinide element . It is a member of the 7th period and is placed in group 16 as the heaviest chalcogen , although it has not been confirmed to behave as the heavier homologue to the chalcogen polonium . Livermorium is calculated to have some similar properties to its lighter homologues ( oxygen , sulfur , selenium , tellurium , and polonium ) , although it should also show several major differences from them .
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= = History = =
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= = = Unsuccessful synthesis attempts = = =
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In late 1998 , Polish physicist Robert <unk> published calculations on the fusion of atomic nuclei towards the synthesis of superheavy atoms , including ununoctium and livermorium . His calculations suggested that it might be possible to make these two elements by fusing lead with krypton under carefully controlled conditions .
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In 1999 , researchers at Lawrence Berkeley National Laboratory made use of these predictions and announced the discovery of livermorium and ununoctium , in a paper published in Physical Review Letters , and very soon after the results were reported in Science . The researchers reported to have performed the reaction
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86
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<unk> + 208
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82Pb → 293
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118Uuo + n → 289
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116Lv + α
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The following year , they published a retraction after researchers at other laboratories were unable to duplicate the results and the Berkeley lab itself was unable to duplicate them as well . In June 2002 , the director of the lab announced that the original claim of the discovery of these two elements had been based on data fabricated by principal author Victor Ninov .
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= = = Discovery = = =
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Livermorium was first synthesized on July 19 , 2000 , when scientists at Dubna ( JINR ) bombarded a curium @-@ 248 target with accelerated calcium @-@ 48 ions . A single atom was detected , decaying by alpha emission with decay energy 10 @.@ 54 MeV to an isotope of flerovium . The results were published in December 2000 .
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248
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96Cm + 48
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20Ca → 296
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116Lv * → 293
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116Lv + 3 1
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0n → 289
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114Fl + α
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The daughter flerovium isotope had properties matching those of a flerovium isotope first synthesized in June 1999 , which was originally assigned to 288Fl , implying an assignment of the parent livermorium isotope to <unk> . Later work in December 2002 indicated that the synthesized flerovium isotope was actually 289Fl , and hence the assignment of the synthesized livermorium atom was correspondingly altered to 293Lv .
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= = = Road to confirmation = = =
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Two further atoms were reported by the institute during their second experiment during April – May 2001 . In the same experiment they also detected a decay chain which corresponded to the first observed decay of flerovium in December 1998 , which had been assigned to 289Fl . No flerovium isotope with the same properties as the one found in December 1998 has ever been observed again , even in repeats of the same reaction . Later it was found that 289Fl have different decay properties and that the first observed flerovium atom may have been its nuclear isomer 289mFl . The observation of 289mFl in this series of experiments may indicate the formation of a parent isomer of livermorium , namely <unk> , or a rare and previously unobserved decay branch of the already @-@ discovered state 293Lv to 289mFl . Neither possibility is certain , and research is required to positively assign this activity .
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The team repeated the experiment in April – May 2005 and detected 8 atoms of livermorium . The measured decay data confirmed the assignment of the first @-@ discovered isotope as 293Lv . In this run , the team also observed the isotope <unk> for the first time . In further experiments from 2004 to 2006 , the team replaced the curium @-@ 248 target with the lighter curium isotope curium @-@ 245 . Here evidence was found for the two isotopes 290Lv and 291Lv .
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