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= = Plot = =
Fox Mulder ( David Duchovny ) dreams of a red light that leads him to the corpse of a young girl buried in a park in Manassas , Virginia . When he awakens , he heads to the park and finds the girl 's skeleton . The girl was determined to have been murdered by John Lee Roche ( Tom Noonan ) , a serial killer who murdered thirteen girls throughout the 1980s ; his modus operandi was cutting a heart out of the clothes of each victim . Mulder had captured Roche by deducing that he committed the murders while traveling as a vacuum cleaner salesman . Roche 's hearts were never found , although he confessed to all of the murders .
Dana Scully 's ( Gillian Anderson ) autopsy of the skeleton finds that the victim died in 1975 , suggesting that Roche 's killing spree started much earlier than the FBI had previously thought . The agents search Roche 's old car , where they discover sixteen cut @-@ out hearts . Mulder and Scully subsequently visit Roche in prison , hoping to learn the identities of the remaining two victims . Roche , however , tries to play mind games with Mulder . That night Mulder dreams of the night of Samantha 's abduction , seemingly showing that his sister was abducted by Roche rather than aliens .
The next day , Mulder asks Roche where he was the night Samantha was abducted . Roche claims he was on Martha 's Vineyard and had sold a vacuum cleaner to Mulder 's father . Mulder later finds the vacuum in his mother 's house . After convincing Walter Skinner to grant them further access to Roche , the agents question the killer and are told the location of one of his remaining victims . He also claims exactly what happened the night of Samantha 's abduction . An autopsy of the body reveals it does not belong to Samantha . Roche tells Mulder the final body is Samantha 's , but says that he will only reveal where it is if Mulder takes him to the scene of her abduction . Mulder secretly releases Roche from prison and brings him to Martha 's Vineyard .
Upon arriving at his family 's old summer house , Roche explains exactly what happened the night of Samantha 's abduction . However , Mulder tells him that the house was bought by his father after Samantha 's abduction , convincing him that Roche is not telling the truth . Mulder plans to bring Roche back to prison , but — following another dream about Samantha — awakens to find Roche gone , with his badge , gun , and phone stolen .
Using Mulder 's credentials , Roche kidnaps a girl in Swampscott , Massachusetts whom he met on his flight with Mulder to Boston . Scully and Skinner arrive the next day and the agents head to the site of Roche 's old apartment in Revere . They find him with the girl in an abandoned bus nearby . Roche holds the gun on the girl and tells Mulder that he 'll never know for sure whether the last victim is Samantha or not if he kills him . Mulder is then forced to shoot Roche , as he starts to pull on the trigger of the stolen gun . In his office Mulder stares at the final cloth heart and puts it away , unsure of whether it belonged to Samantha or not .
= = Production = =
" Paper Hearts " was written specifically with Tom Noonan in mind for the role of Roche , and was amongst the first television work the actor had done . Writer Vince Gilligan came up with the concept for the episode when thinking about the series ' longest running storyline , the abduction of Samantha Mulder . Gilligan came up with a story questioning whether Samantha had not been abducted by aliens , but was rather murdered by a child killer instead . He decided to help convince Fox Mulder of this through a series of prophetic dreams . The laser lights in Mulder 's dreams were influenced by Gilligan 's experience with laser holograms while he was a film student . The laser was supposed to be the color blue , but was changed to red in production to reduce costs . Wanting to include some kind of fetish for the killer , Gilligan settled on having Roche cut heart shaped fragments from his victim 's clothing , thinking that having him mutilate his victims ' bodies would be going too far .
Guest actor Tom Noonan , who played the killer John Lee Roche , recalled filming the scene in which his character is introduced , playing basketball in prison . Noonan , a capable basketball player , was asked to " downplay " how well he could play ; although he regretted not being able to play against David Duchovny , who had played basketball for Princeton University . Episode writer Vince Gilligan and director Rob Bowman assert that Duchovny 's successful basketball shot in this scene was filmed in just one take , without special effects . While the episode was the eighth produced in the season , it was the tenth aired , having been delayed to free up production resources for the two part episodes " Tunguska " and " Terma " . The episode 's climactic scene was filmed in a " bus graveyard " in Surrey , British Columbia , a location which had been scouted months previously with the intention of eventually including it in an episode of the series ; although filming at the location did not even last a full day despite the long wait to use it .
= = Broadcast and reception = =
" Paper Hearts " premiered on the Fox network on December 15 , 1996 , and was first broadcast in the United Kingdom on BBC Two on November 12 , 1997 . The episode 's initial broadcast was viewed by approximately 16 @.@ 59 million people , which represented 16 % of the viewing audience during that time .
Both Gillian Anderson and David Duchovny consider this among the best episodes of the fourth season . Composer Mark Snow was nominated for an Emmy Award for the music he produced for this episode . He said of the episode 's music , " It was a different kind of texture for the show . Light , magic , nothing terribly threatening " . Snow received many requests for a recording of the music used at the end of the episode .
Website IGN named " Paper Hearts " their sixth favorite " standalone " episode of the show , calling it " creepy and unsettling " , and claiming Noonan 's character was " one of the most disturbing villains to make an appearance in the series " . Noonan 's acting has also been praised by Vince Gilligan , who says the " understated " manner in which Roche is portrayed " sends chills down [ his ] spine every time " . The A.V. Club 's Todd VanDerWerff reviewed the episode positively , rating it an A. He felt that Noonan 's performance was " terrific " , noting that the actor " makes Roche into one of the series ' great human monsters " ; and believed that the episode 's premise was important to developing the character of Mulder further . The website later named the episode the sixth best example of a television dream sequence , noting that it " suggest [ s ] how this methodical man [ Mulder ] might puzzle over cold cases in his subconscious " . The article also complimented the entry 's metaphor that laser pointers were Mulder 's mind that pointed " out bits of evidence his conscious brain missed all those many years ago . " Starpulse named it the second best episode of the series .
= Retreat of glaciers since 1850 =
The retreat of glaciers since 1850 affects the availability of fresh water for irrigation and domestic use , mountain recreation , animals and plants that depend on glacier @-@ melt , and , in the longer term , the level of the oceans . Studied by glaciologists , the temporal coincidence of glacier retreat with the measured increase of atmospheric greenhouse gasses is often cited as an evidentiary underpinning of global warming . Mid @-@ latitude mountain ranges such as the Himalayas , Alps , Rocky Mountains , Cascade Range , and the southern Andes , as well as isolated tropical summits such as Mount Kilimanjaro in Africa , are showing some of the largest proportionate glacial losses .
Glacier mass balance is the key determinant of the health of a glacier . If the amount of frozen precipitation in the accumulation zone exceeds the quantity of glacial ice lost due to melting or in the ablation zone a glacier will advance ; if the accumulation is less than the ablation , the glacier will retreat . Glaciers in retreat will have negative mass balances , and if they do not find an equilibrium between accumulation and ablation , will eventually disappear .
The Little Ice Age was a period from about 1550 to 1850 when the world experienced relatively cooler temperatures compared to the present . Subsequently , until about 1940 , glaciers around the world retreated as the climate warmed substantially . Glacial retreat slowed and even reversed temporarily , in many cases , between 1950 and 1980 as global temperatures cooled slightly . Since 1980 , a significant global warming has led to glacier retreat becoming increasingly rapid and ubiquitous , so much so that some glaciers have disappeared altogether , and the existences of many of the remaining glaciers are threatened . In locations such as the Andes of South America and Himalayas in Asia , the demise of glaciers in these regions has the potential to affect water supplies in those areas .
The retreat of mountain glaciers , notably in western North America , Asia , the Alps and tropical and subtropical regions of South America , Africa and Indonesia , provide evidence for the rise in global temperatures since the late 19th century . The acceleration of the rate of retreat since 1995 of key outlet glaciers of the Greenland and West Antarctic ice sheets may foreshadow a rise in sea level , which would affect coastal regions .
= = Glacier mass balance = =
The mass balance , or difference between accumulation and ablation ( melting and sublimation ) , of a glacier is crucial to its survival . Climate change may cause variations in both temperature and snowfall , resulting in changes in mass balance . A glacier with a sustained negative balance loses equilibrium and retreats . A sustained positive balance is also out of equilibrium and will advance to reestablish equilibrium . Currently , nearly all glaciers have a negative mass balance and are retreating .
Glacier retreat results in the loss of the low @-@ elevation region of the glacier . Since higher elevations are cooler , the disappearance of the lowest portion decreases overall ablation , thereby increasing mass balance and potentially reestablishing equilibrium . If the mass balance of a significant portion of the accumulation zone of the glacier is negative , it is in disequilibrium with the climate and will melt away without a colder climate and or an increase in frozen precipitation .
Methods for measuring retreat include staking terminus location , global positioning mapping , aerial mapping and laser altimetry . The key symptom of disequilibrium is thinning along the entire length of the glacier . This indicates a diminishment of the accumulation zone . The result is marginal recession of the accumulation zone margin , not just of the terminus . In effect , the glacier no longer has a consistent accumulation zone and without an accumulation zone cannot survive . For example , Easton Glacier in Washington state , U.S. will likely shrink to half its size but at a slowing rate of reduction and stabilize at that size despite the warmer temperature over a few decades . However , the Grinnell Glacier in Montana , U.S. will shrink at an increasing rate until it disappears . The difference is that the upper section of Easton Glacier remains healthy and snow @-@ covered , while even the upper section of the Grinnell Glacier is bare , is melting and has thinned . Small glaciers with minimal altitude range are most likely to fall into disequilibrium with the climate .
= = Middle latitude glaciers = =
Middle latitude glaciers are located either between the Tropic of Cancer and the Arctic Circle , or between the Tropic of Capricorn and the Antarctic Circle . Both areas support glacier ice from mountain glaciers , valley glaciers and even smaller icecaps , which are usually located in higher mountainous regions . All are located in mountain ranges , notably the Himalayas ; the Alps ; the Pyrenees ; Rocky Mountains and Pacific Coast Ranges of North America ; the Patagonian Andes in South America ; and mountain ranges in New Zealand . Glaciers in these latitudes are more widespread and tend to be greater in mass the closer they are to the polar regions . They are the most widely studied over the past 150 years . As with examples located in the tropical zone , virtually all the glaciers in the mid @-@ latitudes are in a state of negative mass balance and are retreating .
= = = Eastern hemisphere = = =
= = = = Europe = = = =
In France all six of the major glaciers in that country are in retreat . On Mont Blanc , the highest peak in the Alps , the Argentière Glacier has receded 1 @,@ 150 m ( 3 @,@ 770 ft ) since 1870 . Other Mont Blanc glaciers have also been in retreat , including the Mer de Glace , which is the largest glacier in France at 12 km ( 7 @.@ 5 mi ) in length but retreated 500 m ( 1 @,@ 600 ft ) between 1994 and 2008 . The glacier has retreated 2 @,@ 300 m ( 7 @,@ 500 ft ) since the end of the Little Ice Age . The Bossons Glacier once extended from the summit of Mont Blanc at 4 @,@ 807 m ( 15 @,@ 771 ft ) to an elevation of 1 @,@ 050 m ( 3 @,@ 440 ft ) in 1900 . By 2008 Bossons Glacier had retreated to a point that was 1 @,@ 400 m ( 4 @,@ 600 ft ) above sea level .
Other researchers have found that glaciers across the Alps appear to be retreating at a faster rate than a few decades ago . In a paper published in 2009 by the University of Zurich , the Swiss glacier survey of 89 glaciers found 76 retreating , 5 stationary and 8 advancing from where they had been in 1973 . The <unk> Glacier had the greatest recorded retreat , losing 350 m ( 1 @,@ 150 ft ) of its length between the years 2003 and 2005 . The Grosser Aletsch Glacier is the largest glacier in Switzerland and has been studied since the late 19th century . Aletsch Glacier retreated 2 @.@ 8 km ( 1 @.@ 7 mi ) from 1880 to 2009 . This rate of retreat has also increased since 1980 , with 30 % , or 800 m ( 2 @,@ 600 ft ) , of the total retreat occurring in the last 20 % of the time period .
The <unk> Glacier in Switzerland has had one of the longest periods of scientific study with yearly measurements of the glacier 's length commencing in 1878 . The overall retreat from 1878 to 1998 has been 2 km ( 1 @.@ 2 mi ) with a mean annual retreat rate of approximately 17 m ( 56 ft ) per year . This long @-@ term average was markedly surpassed in recent years with the glacier receding 30 m ( 98 ft ) per year during the period between 1999 – 2005 . Similarly , of the glaciers in the Italian Alps , only about a third were in retreat in 1980 , while by 1999 , 89 % of these glaciers were retreating . In 2005 , the Italian Glacier Commission found that 123 glaciers in Lombardy were retreating . A random study of the <unk> Glacier in the Italian Alps indicated that the rate of retreat from 2002 to 2006 was much higher than in the preceding 35 years . To study glaciers located in the alpine regions of Lombardy , researchers compared a series of aerial and ground images taken from the 1950s through the early 21st century and deduced that between the years 1954 @-@ 2003 the mostly smaller glaciers found there lost more than half of their area . Repeat photography of glaciers in the Alps indicates that there as been significant retreat since studies commenced .
Though the glaciers of the Alps have received more attention from glaciologists than in other areas of Europe , research indicates that glaciers in northern Europe are also retreating . Since the end of World War II , <unk> in Sweden has undergone the longest continuous mass balance study in the world conducted from the <unk> research station . In the <unk> Mountains of northern Sweden , a study of 16 glaciers between 1990 and 2001 found that 14 glaciers were retreating , one was advancing and one was stable . In Norway , glacier studies have been performed since the early 19th century , with systematic surveys undertaken regularly since the 1990s . Inland glaciers have had a generally negative mass balance , whereby during the 1990s , maritime glaciers showed a positive mass balance and advanced . The maritime advances have been attributed to heavy snowfall in the period 1989 @-@ 1995 . However , reduced snowfall since has caused most Norwegian glaciers to retreat significantly . A survey of 31 Norwegian glaciers in 2010 indicated that 27 were in retreat , one had no change and three advanced . Similarly , in 2013 , of 33 Norwegian glaciers surveyed , 26 were retreating , four showed no change and three advanced .
<unk> Glacier in Norway , an outlet glacier of the <unk> ice cap , had several advances in the 20th century , though it retreated 200 m ( 660 ft ) between 1999 and 2014 . <unk> glacier retreated 56 m ( 184 ft ) between the years 2000 and 2014 , while the <unk> glacier , which has retreated 2 km ( 1 @.@ 2 mi ) since the end of the Little Ice Age , retreated 200 m ( 660 ft ) between 1997 @-@ 2007 . The Briksdalsbreen glacier retreated 230 m ( 750 ft ) between 1996 and 2004 with 130 m ( 430 ft ) of that in the last year of that study ; the greatest annual retreat recorded on that glacier since studies began there in 1900 . This figure was exceeded in 2006 with five glaciers retreating over 100 m ( 330 ft ) from the fall of 2005 to the fall of 2006 . Four outlets from the <unk> ice cap , the largest body of ice in continental Europe , <unk> , <unk> , Briksdalsbreen and <unk> had a frontal retreat of more than 100 m ( 330 ft ) . Overall , from 1999 to 2005 , Briksdalsbreen retreated 336 metres ( 1 @,@ 102 ft ) . <unk> , an outlet glacier of the Folgefonna ice cap , had a retreat of almost 100 m ( 330 ft ) .
In the Spanish Pyrenees , recent studies have shown important losses in extent and volume of the glaciers of the <unk> massif during the period 1981 – 2005 . These include a reduction in area of 35 @.@ 7 % , from 2 @.@ 41 km2 ( 600 acres ) to 0 @.@ 627 km2 ( 155 acres ) , a loss in total ice volume of 0 @.@ <unk> km3 ( 0 @.@ 0033 cu mi ) and an increase in the mean altitude of the glacial termini of 43 @.@ 5 m ( 143 ft ) . For the Pyrenees as a whole 50 – 60 % of the glaciated area has been lost since 1991 . The <unk> , <unk> and La <unk> glaciers have disappeared in this period . Monte Perdido Glacier has shrunk from 90 hectares to 40 hectares .
As initial cause for glacier retreat in the alps since 1850 , a decrease of the glaciers albedo , caused by industrial black carbon can be identified . According to a report , this may have accelerated the retreat of glaciers in Europe which otherwise may have continued to expand until approximately the year 1910 .
= = = = Siberia and the Russian Far East = = = =
Siberia is typically classified as a polar region , owing to the dryness of the winter climate and has glaciers only in the high Altai Mountains , Verkhoyansk Range , <unk> Range and <unk> @-@ <unk> Range , plus possibly a few very small glaciers in the ranges near Lake Baikal , which have never been monitored and may have completely disappeared since 1989 . Between the years 1952 and 2006 , the glaciers found in the <unk> Basin region shrank by 7 @.@ 2 percent . This shrinkage has been primarily in the ablation zone of the glaciers , with recession of several hundred meters being observed for some glaciers . The Altai region has also experienced an overall temperature increase of 1 @.@ 2 degrees Celsius in the last 120 years according to a report from 2006 , with most of that increase occurring since the late 20th century .
In the more maritime and generally wetter Russian Far East , Kamchatka , exposed during winter to moisture from the Aleutian Low , has much more extensive glaciation totaling around 906 km2 ( 350 sq mi ) with 448 known glaciers as of 2010 . Despite generally heavy winter snowfall and cool summer temperatures , the high summer rainfall of the more southerly Kuril Islands and Sakhalin in historic times melt rates have been too high for a positive mass balance even on the highest peaks . In the <unk> Peninsula small alpine glaciers are numerous , but the extent of glaciation , though larger than further west , is much smaller than in Kamchatka , totalling around 300 square kilometres ( 120 sq mi ) .
Details on the retreat of Siberian and Russian Far East glaciers less adequate than in most other glaciated areas of the world . There are several reasons for this , the principal one being that since the collapse of Communism there has been a large reduction in the number of monitoring stations . Another factor is that in the Verkhoyansk and <unk> Ranges it was thought glaciers were absent before they were discovered during the 1940s , whilst in ultra @-@ remote Kamchatka and Chukotka , although the existence of glaciers was known earlier , monitoring of their size dates back no earlier than the end of World War II . Nonetheless , available records do indicate a general retreat of all glaciers in the Altai Mountains with the exception of volcanic glaciers in Kamchatka . Sakha ’ s glaciers , totaling seventy square kilometers , have shrunk by around 28 percent since 1945 reaching several percent annually in some places , whilst in the Altai and <unk> mountains and non @-@ volcanic areas of Kamchatka , the shrinkage is considerably larger .
= = = = Asia = = = =
The Himalayas and other mountain chains of central Asia support large glaciated regions . An estimated 15 @,@ 000 glaciers can be found in the greater Himalayas , with double that number in the Hindu Kush and Karakoram and Tien Shan ranges , and comprise the largest glaciated region outside the poles . These glaciers provide critical water supplies to arid countries such as Mongolia , western China , Pakistan , Afghanistan and India . As with glaciers worldwide , those of the greater Himalayan region are experiencing a decline in mass , and researchers claim that between the early 1970s and early 2000s , there had been a 9 percent reduction in ice mass . Change in temperature has led to melting and the formation and expansion of glacial lakes which could cause an increase in the number of glacial lake outburst floods ( GLOFs ) . If the present trends persist the ice mass will gradually be reduced , and will affect the availability of water resources , though water loss is not expected to cause problems for many decades .
In the Wakhan Corridor of Afghanistan 28 of 30 glaciers examined retreated significantly between 1976 – 2003 , with an average retreat of 11 m ( 36 ft ) per year . One of these glaciers , the <unk> Glacier , retreated 460 m ( 1 @,@ 510 ft ) during this period , not quite 10 % of its 5 @.@ 2 km ( 3 @.@ 2 mi ) length . In examining 612 glaciers in China between 1950 and 1970 , 53 % of the glaciers studied were retreating . After 1990 , 95 % of these glaciers were measured to be retreating , indicating that retreat of these glaciers was becoming more widespread . Glaciers in the Mount Everest region of the Himalayas are all in a state of retreat . The <unk> Glacier , draining the north side of Mount Everest into Tibet , has been retreating 20 m ( 66 ft ) per year . In the Khumbu region of Nepal along the front of the main Himalaya of 15 glaciers examined from 1976 – 2007 all retreated significantly and the average retreat was 28 m ( 92 ft ) per year . The most famous of these , the Khumbu Glacier , retreated at a rate of 18 m ( 59 ft ) per year from 1976 – 2007 . In India , the Gangotri Glacier retreated 1 @,@ 147 m ( 3 @,@ 763 ft ) between the years 1936 and 1996 with 850 m ( 2 @,@ 790 ft ) of that retreat occurring in the last 25 years of the 20th century . However , the glacier is still over 30 km ( 19 mi ) long . In Sikkim , 26 glaciers examined between the years 1976 and 2005 were retreating at an average rate of 13 @.@ 02 m ( 42 @.@ 7 ft ) per year . Overall , glaciers in the Greater Himalayan region that have been studied are retreating an average of between 18 and 20 m ( 59 and 66 ft ) annually . The only region in the Greater Himalaya that has seen glacial advances is in the Karakoram Range and only in the highest elevation glaciers , but this has been attributed possibly increased precipitation as well as to the correlating glacial surges , where the glacier tongue advances due to pressure build up from snow and ice accumulation further up the glacier . Between the years 1997 and 2001 , 68 km ( 42 mi ) long Biafo Glacier thickened 10 to 25 m ( 33 to 82 ft ) mid @-@ glacier , however it did not advance .
With the retreat of glaciers in the Himalayas , a number of glacial lakes have been created . A growing concern is the potential for GLOFs researchers estimate 21 glacial lakes in Nepal and 24 in Bhutan pose hazards to human populations should their terminal moraines fail . One glacial lake identified as potentially hazardous is Bhutan 's <unk> Tsho , which measured 1 @.@ 6 km ( 0 @.@ 99 mi ) long , 0 @.@ 96 km ( 0 @.@ 60 mi ) wide and 80 m ( 260 ft ) deep in 1986 . By 1995 the lake had swollen to a length of 1 @.@ 94 km ( 1 @.@ 21 mi ) , 1 @.@ 13 km ( 0 @.@ 70 mi ) in width and a depth of 107 m ( 351 ft ) . In 1994 a GLOF from <unk> Tsho , a glacial lake adjacent to <unk> Tsho , killed 23 people downstream .
Glaciers in the Ak @-@ <unk> Range in Kyrgyzstan experienced a slight loss between 1943 and 1977 and an accelerated loss of 20 % of their remaining mass between 1977 and 2001 . In the Tien Shan mountains , which Kyrgyzstan shares with China and Kazakhstan , studies in the northern areas of that mountain range show that the glaciers that help supply water to this arid region , lost nearly 2 km3 ( 0 @.@ 48 cu mi ) of ice per year between 1955 and 2000 . The University of Oxford study also reported that an average of 1 @.@ 28 % of the volume of these glaciers had been lost per year between 1974 and 1990 .
The Pamirs mountain range located primarily in Tajikistan , has approximately eight thousand glaciers , many of which are in a general state of retreat . During the 20th century , the glaciers of Tajikistan lost 20 km3 ( 4 @.@ 8 cu mi ) of ice . The 70 km ( 43 mi ) long <unk> Glacier , which is the largest in Tajikistan and the largest non @-@ polar glacier on Earth , retreated 1 km ( 0 @.@ 62 mi ) between the years 1933 and 2006 , and lost 44 km2 ( 17 sq mi ) of its surface area due to shrinkage between the years 1966 and 2000 . Tajikistan and neighboring countries of the Pamir Range are highly dependent upon glacial runoff to ensure river flow during droughts and the dry seasons experienced every year . The continued demise of glacier ice will result in a short @-@ term increase , followed by a long @-@ term decrease in glacial melt water flowing into rivers and streams .
= = = = Oceania = = = =
In New Zealand , mountain glaciers have been in general retreat since 1890 , with an acceleration since 1920 . Most have measurably thinned and reduced in size , and the snow accumulation zones have risen in elevation as the 20th century progressed . Between 1971 – 75 Ivory Glacier receded 30 m ( 98 ft ) from the glacial terminus , and about 26 % of its surface area was lost . Since 1980 numerous small glacial lakes formed behind the new terminal moraines of several of these glaciers . Glaciers such as Classen , Godley and Douglas now all have new glacial lakes below their terminal locations due to the glacial retreat over the past 20 years . Satellite imagery indicates that these lakes are continuing to expand . There has been significant and ongoing ice volume losses on the largest New Zealand glaciers , including the Tasman , Ivory , Classen , Mueller , Maud , Hooker , Grey , Godley , Ramsay , Murchison , <unk> , Volta and Douglas Glaciers . The retreat of these glaciers has been marked by expanding proglacial lakes and terminus region thinning . The loss in Southern Alps total ice volume from 1976 – 2014 is 34 percent of the total .
Several glaciers , notably the much @-@ visited Fox and Franz Josef Glaciers on New Zealand 's West Coast , have periodically advanced , especially during the 1990s , but the scale of these advances is small when compared to 20th @-@ century retreat . Both are more than 2 @.@ 5 km ( 1 @.@ 6 mi ) shorter than a century ago . These large , rapidly flowing glaciers situated on steep slopes have been very reactive to small mass @-@ balance changes . A few years of conditions favorable to glacier advance , such as more westerly winds and a resulting increase in snowfall , are rapidly echoed in a corresponding advance , followed by equally rapid retreat when those favorable conditions end . The glaciers that have been advancing in a few locations in New Zealand have been doing so due to transient local weather conditions , which have brought more precipitation and cloudier , cooler summers since 2002 .
= = = Western hemisphere = = =
North American glaciers are primarily located along the spine of the Rocky Mountains in the United States and Canada , and the Pacific Coast Ranges extending from northern California to Alaska . While Greenland is geologically associated with North America , it is also a part of the Arctic region . Apart from the few tidewater glaciers such as Taku Glacier , in the advance stage of their tidewater glacier cycle prevalent along the coast of Alaska , virtually all of those in North America are in a state of retreat . This rate has increased rapidly since around 1980 , and overall each decade since has seen greater rates of retreat than the preceding one . There are also small remnant glaciers scattered throughout the Sierra Nevada mountains of California and Nevada .
= = = = Cascade Range = = = =
The Cascade Range of western North America extends from southern British Columbia in Canada to northern California . Excepting Alaska , about half of the glacial area in the U.S. is contained within the over 700 glaciers of the North Cascades , a portion of those located between the Canadian border and I @-@ 90 in central Washington . These contain much water as is found in all the lakes and reservoirs in the rest of the state , and provide much of the stream and river flow in the dry summer months , approximating some 870 @,@ 000 m3 ( 1 @,@ 140 @,@ 000 cu yd ) .
As recently as 1975 many North Cascade glaciers were advancing due to cooler weather and increased precipitation that occurred from 1944 to 1976 . By 1987 the North Cascade glaciers were retreating and the pace had increased each decade since the mid @-@ 1970s . Between 1984 and 2005 the North Cascade glaciers lost an average of more than 12 @.@ 5 metres ( 41 ft ) in thickness and 20 – 40 percent of their volume .
Glaciologists researching the North Cascades found that all 47 monitored glaciers are receding while four glaciers — Spider Glacier , Lewis Glacier , Milk Lake Glacier and David Glacier — have disappeared completely since 1985 . The White Chuck Glacier ( near Glacier Peak ) is a particularly dramatic example . The glacier area shrank from 3 @.@ 1 km2 ( 1 @.@ 2 sq mi ) in 1958 to 0 @.@ 9 km2 ( 0 @.@ 35 sq mi ) by 2002 . Between 1850 and 1950 , the Boulder Glacier on the southeast flank of Mount Baker retreated 8 @,@ 700 feet ( 2 @,@ 700 m ) . William Long of the United States Forest Service observed the glacier beginning to advance due to cooler / wetter weather in 1953 . This was followed by a 743 metres ( 2 @,@ 438 ft ) advance by 1979 . The glacier again retreated 450 m ( 1 @,@ 480 ft ) from 1987 to 2005 , leaving barren terrain behind . This retreat has occurred during a period of reduced winter snowfall and higher summer temperatures . In this region of the Cascades , winter snowpack has declined 25 % since 1946 , and summer temperatures have risen 0 @.@ 7 ° C ( 1 @.@ 2 ° F ) during the same period . The reduced snowpack has occurred despite a small increase in winter precipitation — thus , it reflects warmer winter temperatures leading to rainfall and melting on glaciers even during the winter . As of 2005 , 67 % of the North Cascade glaciers observed are in disequilibrium and will not survive the continuation of the present climate . These glaciers will eventually disappear unless temperatures fall and frozen precipitation increases . The remaining glaciers are expected to stabilize , unless the climate continues to warm , but will be much reduced in size .
= = = = U.S. Rocky Mountains = = = =
On the sheltered slopes of the highest peaks of Glacier National Park in Montana , the eponymous glaciers are diminishing rapidly . The area of each glacier has been mapped for decades by the National Park Service and the U.S. Geological Survey . Comparing photographs from the mid @-@ 19th century with contemporary images provides ample evidence that they have retreated notably since 1850 . Repeat photography since clearly show that glaciers such as Grinnell Glacier are all retreating . The larger glaciers are now approximately a third of their former size when first studied in 1850 , and numerous smaller glaciers have disappeared completely . Only 27 % of the 99 km2 ( 38 sq mi ) area of Glacier National Park covered by glaciers in 1850 remained covered by 1993 . Researchers believe that by the year 2030 , the vast majority of glacial ice in Glacier National Park will be gone unless current climate patterns reverse their course . Grinnell Glacier is just one of many glaciers in Glacier National Park that have been well documented by photographs for many decades . The photographs below clearly demonstrate the retreat of this glacier since 1938 .
The semiarid climate of Wyoming still manages to support about a dozen small glaciers within Grand Teton National Park , which all show evidence of retreat over the past 50 years . <unk> Glacier is located slightly southwest of Grand Teton is one of the more easily reached glaciers in the park and it is expected to disappear by 2025 . Research between 1950 and 1999 demonstrated that the glaciers in Bridger @-@ Teton National Forest and Shoshone National Forest in the Wind River Range shrank by over a third of their size during that period . Photographs indicate that the glaciers today are only half the size as when first photographed in the late 1890s . Research also indicates that the glacial retreat was proportionately greater in the 1990s than in any other decade over the last 100 years . Gannett Glacier on the northeast slope of Gannett Peak is the largest single glacier in the Rocky Mountains south of Canada . It has reportedly lost over 50 % of its volume since 1920 , with almost half of that loss occurring since 1980 . Glaciologists believe the remaining glaciers in Wyoming will disappear by the middle of the 21st century if the current climate patterns continue .
= = = = Canadian Rockies and Coast and Columbia Mountains = = = =
In the Canadian Rockies , glaciers are generally larger and more widespread than to the south in the Rocky Mountains . One of the more accessible in the Canadian Rockies is the Athabasca Glacier , which is an outlet glacier of the 325 km2 ( 125 sq mi ) Columbia Icefield . The Athabasca Glacier has retreated 1 @,@ 500 m ( 4 @,@ 900 ft ) since the late 19th century . Its rate of retreat has increased since 1980 , following a period of slow retreat from 1950 to 1980 . The Peyto Glacier in Alberta covers an area of about 12 km2 ( 4 @.@ 6 sq mi ) , and retreated rapidly during the first half of the 20th century , stabilized by 1966 , and resumed shrinking in 1976 .
The Illecillewaet Glacier in British Columbia 's Glacier National Park ( Canada ) , part of the Selkirk Mountains ( west of the Rockies ) has retreated 2 km ( 1 @.@ 2 mi ) since first photographed in 1887 .
In Garibaldi Provincial Park in Southwestern British Columbia over 505 km2 ( 195 sq mi ) , or 26 % , of the park , was covered by glacier ice at the beginning of the 18th century . Ice cover decreased to 297 km2 ( 115 sq mi ) by 1987 – 1988 and to 245 km2 ( 95 sq mi ) by 2005 , 50 % of the 1850 area . The 50 km2 ( 19 sq mi ) loss in the last 20 years coincides with negative mass balance in the region . During this period all nine glaciers examined have retreated significantly .
= = = = Alaska = = = =
There are thousands of glaciers in Alaska but only few have been named . The Columbia Glacier near Valdez in Prince William Sound has retreated 15 km ( 9 @.@ 3 mi ) in the last 25 years . Its calved icebergs partially caused the Exxon Valdez oil spill , when the tanker changed course to avoid the ice tips . The Valdez Glacier is in the same area , and though it does not calve , has also retreated significantly . " A 2005 aerial survey of Alaskan coastal glaciers identified more than a dozen glaciers , many former tidewater and calving glaciers , including Grand Plateau , Alsek , Bear , and Excelsior Glaciers that are rapidly retreating . Of 2 @,@ 000 glaciers observed , 99 % are retreating . " Icy Bay in Alaska is fed by three large glaciers — Guyot , <unk> , and Tyndall Glaciers — all of which have experienced a loss in length and thickness and , consequently , a loss in area . Tyndall Glacier became separated from the retreating Guyot Glacier in the 1960s and has retreated 24 km ( 15 mi ) since , averaging more than 500 m ( 1 @,@ 600 ft ) per year .
The Juneau Icefield Research Program has monitored outlet glaciers of the Juneau Icefield since 1946 . On the west side of the ice field , the terminus of the Mendenhall Glacier , which flows into suburban Juneau , Alaska , has retreated 580 m ( 1 @,@ 900 ft ) . Of the nineteen glaciers of the Juneau Icefield , eighteen are retreating , and one , the Taku Glacier , is advancing . Eleven of the glaciers have retreated more than 1 km ( 0 @.@ 62 mi ) since 1948 — Antler Glacier , 5 @.@ 4 km ( 3 @.@ 4 mi ) ; Gilkey Glacier , 3 @.@ 5 km ( 2 @.@ 2 mi ) ; Norris Glacier , 1 @.@ 1 km ( 0 @.@ 68 mi ) and Lemon Creek Glacier , 1 @.@ 5 km ( 0 @.@ 93 mi ) . Taku Glacier has been advancing since at least 1890 , when naturalist John Muir observed a large iceberg calving front . By 1948 the adjacent fjord had filled in , and the glacier no longer calved and was able to continue its advance . By 2005 the glacier was only 1 @.@ 5 km ( 0 @.@ 93 mi ) from reaching Taku Point and blocking Taku Inlet . The advance of Taku Glacier averaged 17 m ( 56 ft ) per year between 1988 and 2005 . The mass balance was very positive for the 1946 – 88 period fueling the advance ; however , since 1988 the mass balance has been slightly negative , which should in the future slow the advance of this mighty glacier .
Long @-@ term mass balance records from Lemon Creek Glacier in Alaska show slightly declining mass balance with time . The mean annual balance for this glacier was − 0 @.@ 23 m ( 0 @.@ 75 ft ) each year during the period of 1957 to 1976 . Mean annual balance has been increasingly negatively averaging − 1 @.@ 04 m ( 3 @.@ 4 ft ) per year from 1990 to 2005 . Repeat glacier altimetry , or altitude measuring , for 67 Alaska glaciers find rates of thinning have increased by more than a factor of two when comparing the periods from 1950 to 1995 ( 0 @.@ 7 m ( 2 @.@ 3 ft ) per year ) and 1995 to 2001 ( 1 @.@ 8 m ( 5 @.@ 9 ft ) per year ) . This is a systemic trend with loss in mass equating to loss in thickness , which leads to increasing retreat — the glaciers are not only retreating , but they are also becoming much thinner . In Denali National Park , all glaciers monitored are retreating , with an average retreat of 20 m ( 66 ft ) per year . The terminus of the <unk> Glacier has been retreating 26 m ( 85 ft ) per year and the Muldrow Glacier has thinned 20 m ( 66 ft ) since 1979 . Well documented in Alaska are surging glaciers that have been known to rapidly advance , even as much as 100 m ( 330 ft ) per day . Variegated , Black Rapids , Muldrow , Susitna and <unk> are examples of surging glaciers in Alaska that have made rapid advances in the past . These glaciers are all retreating overall , punctuated by short periods of advance .
= = = = Andes and Tierra del Fuego = = = =
A large region of population surrounding the central and southern Andes of Argentina and Chile reside in arid areas that are dependent on water supplies from melting glaciers . The water from the glaciers also supplies rivers that have in some cases been dammed for hydroelectric power . Some researchers believe that by 2030 , many of the large ice caps on the highest Andes will be gone if current climate trends continue . In Patagonia on the southern tip of the continent , the large ice caps have retreated a 1 km ( 0 @.@ 62 mi ) since the early 1990s and 10 km ( 6 @.@ 2 mi ) since the late 19th century . It has also been observed that Patagonian glaciers are receding at a faster rate than in any other world region . The Northern Patagonian Ice Field lost 93 km2 ( 36 sq mi ) of glacier area during the years between 1945 and 1975 , and 174 km2 ( 67 sq mi ) from 1975 to 1996 , which indicates that the rate of retreat is increasing . This represents a loss of 8 % of the ice field , with all glaciers experiencing significant retreat . The Southern Patagonian Ice Field has exhibited a general trend of retreat on 42 glaciers , while four glaciers were in equilibrium and two advanced during the years between 1944 and 1986 . The largest retreat was on O 'Higgins Glacier , which during the period 1896 – 1995 retreated 14 @.@ 6 km ( 9 @.@ 1 mi ) . The Perito Moreno Glacier is 30 km ( 19 mi ) long and is a major outflow glacier of the Patagonian ice sheet , as well as the most visited glacier in Patagonia . Perito Moreno Glacier is in equilibrium , but has undergone frequent oscillations in the period 1947 – 96 , with a net gain of 4 @.@ 1 km ( 2 @.@ 5 mi ) . This glacier has advanced since 1947 , and has been essentially stable since 1992 . Perito Moreno Glacier is one of three glaciers in Patagonia known to have advanced , compared to several hundred others in retreat . The two major glaciers of the Southern Patagonia Icefield to the north of Moreno , Upsala and <unk> Glacier have retreated 4 @.@ 6 km ( 2 @.@ 9 mi ) in 21 years and 1 km ( 0 @.@ 62 mi ) in 13 years respectively . In the Aconcagua River Basin , glacier retreat has resulted in a 20 % loss in glacier area , declining from 151 km2 ( 58 sq mi ) to 121 km2 ( 47 sq mi ) . The Marinelli Glacier in Tierra del Fuego has been in retreat since at least 1960 through 2008 .