Retreat of glaciers since 1850
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The retreat of glaciers since 1850, worldwide and rapid, 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 gases is often cited as an evidentiary underpinning of anthropogenic 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 loss.
The Little Ice Age was a period from about 1550 to 1850 when the world experienced relatively cool temperatures compared to the present. Subsequently, until about 1940 glaciers around the world retreated as the climate warmed. Glacial retreat slowed and even reversed, in many cases, between 1950 and 1980 as a slight global cooling occurred. However, since 1980 a significant global warming has led to glacier retreat becoming increasingly rapid and ubiquitous, so much so that many glaciers have disappeared and the existence of a great number of the remaining glaciers of the world is threatened. In locations such as the Andes of South America and Himalayas in Asia, the demise of glaciers in these regions will have potential impact on water supplies. The retreat of mountain glaciers, notably in western North America, Asia, the Alps, Indonesia and Africa, and tropical and subtropical regions of South America, has been used to provide qualitative evidence for the rise in global temperatures since the late 19th century.
Glacier mass balance
Crucial to the survival of a glacier is its mass balance, the difference between accumulation and ablation (melting and sublimation). Climate change may cause variations in both temperature and snowfall, causing changes in mass balance. A glacier with a sustained negative balance is out of equilibrium and will retreat. A glacier with sustained positive balance is also out of equilibrium, and will advance to reestablish equilibrium. Currently, there are a few advancing glaciers, although their modest growth rates suggest that they are not far from equilibrium.
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 of the glacier reduces overall ablation, thereby increasing mass balance and potentially reestablishing equilibrium. However, 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.
The key symptom of a glacier in disequilibrium is thinning along the entire length of the glacier.
Methods for measuring glacier retreat include staking terminus location, global positioning mapping, aerial mapping, and laser altimetry.
Tropical glaciers
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. Tropical glaciers are the most uncommon of all glaciers for a variety of reasons. Firstly, the tropics 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 can be found in these regions upon which enough cold air exists for the establishment of glaciers. All of the glaciers located in the tropics are on isolated high mountain peaks. 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 impact on tropical glaciers.
With almost the entire continent of Africa located in the tropical and subtropical climate zones, glaciers are restricted to two isolated peaks and the Ruwenzori Range. Mount Kilimanjaro, at 5,895 m (19,340 feet), 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 (984 ft).
To the north of Mount Kilimanjaro lies Mount Kenya, which at 5,199 m (17,057 feet) is the second tallest mountain on the African 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 miles²) in 1900; however. by the year 2000 only about 25%, or 0.4 km² (0.15 miles²), remained.
A study by glaciologists of two small glaciers in South America reveals another alarming retreat. More than 80% of all glacial ice in the northern Andes is concentrated on the highest peaks in small glaciers of approximately one km² (0.38 mile²) in size. A 1992 to 1998 observation of the Chacaltaya Glacier in Bolivia and Antizana Glacier in Ecuador indicated that between 0.6 m (1.9 ft) and 1.4 m (4.6 ft) of ice was lost per year on each glacier. Figures for Chacaltaya Glacier 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. Research also indicates that since the mid-1980s, the rate of retreat for both of these glaciers has been increasing.
![Puncak Jaya glaciers 1972. Left to right: Northwall Firn, Meren Glacier, and Carstensz Glacier. USGS. [Also mid 2005 image] and [animation.]](http://encycl.opentopia.com/enimages/thumb/4805/4804597/250px-Puncak_Jaya_icecap_1972.jpg "Puncak Jaya glaciers 1972. Left to right: Northwall Firn, Meren Glacier, and Carstensz Glacier. USGS. [Also mid 2005 image] and [animation.]")
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 miles²). Research in this region of the Andes is less extensive but indicates an overall glacial retreat of 7% between 1977 and 1983.
On the large island of New Guinea, there is photographic evidence of massive glacial retreat since the region was first extensively explored by airplane in the early 1930s. 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. The 7 km² (2.7 mile²) glacial cap on Puncak Jaya is the largest on the island, and has retreated from one larger mass into several smaller glacial bodies since 1936. Of these smaller glaciers, research between 1973 and 1976 showed glacier retreat for the Meren Glacier of 200 m (656 ft) and 50 m (164 ft) for the Carstenez Glacier. The Northwall Firn, another large remnant of the icecap that once was atop Puncak Jaya, has itself split into several separate glaciers since 1936. Research presented in 2004 of IKONOS satellite imagery of the New Guinean glaciers provided a dramatic update. The imagery indicated 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. Researchers also discovered that, sometime between 1994 and 2000, the Meren Glacier disappeared altogether.
Mid-latitude glaciers
Mid-latitude glaciers are located either between the Tropic of Cancer and the Arctic Circle, or between the Tropic of Capricorn and the Antarctic Circle. These two regions support glacier ice from mountain glaciers, valley glaciers and even smaller icecaps, which are usually located in higher mountainous regions. All of these glaciers are located in mountain ranges, notably the Himalayas; the Alps; Rocky Mountains and Pacific Coast Ranges of North America; the Patagonian Andes in South America; and mountain ranges in the island nation of New Zealand. Glaciers in these latitudes are more widespread and tend to be more massive the closer they are located to the polar regions. These glaciers are the most widely studied over the past 150 years. As is true with the glaciers 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
The World Glacier Monitoring Service reports on changes in the terminus, or lower-elevation end, of glaciers from around the world every five years.
Other researchers have found that glaciers across the Alps appear to be retreating at a faster rate than a few decades ago. In 2005, of the 91 glaciers observed, 84 were retreating and none were advancing. The Trift Glacier had retreated over 500 m (1,600 ft) just in the three years of 2003 to 2005, which is 10% of its total length. The Grosser Aletsch Glacier, the largest glacier in Switzerland, has retreated 2,600 m (8,500 ft) since 1880. 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.
Though the glaciers of the Alps have received more attention from glaciologists than in other areas of Europe, research indicates that throughout most of Europe, glaciers are rapidly retreating. In the Kebnekaise 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.
The Himalayas and other mountain chains of central Asia support large regions that are glaciated. These glaciers provide critical water supplies to arid countries such as Mongolia, western China, Pakistan and Afghanistan. As is true with other glaciers worldwide, the glaciers of Asia are experiencing a rapid decline in mass. The loss of these glaciers would have a tremendous impact on the ecosystem of the region.
A WWF report concluded that 67% of all Himalayan glaciers are retreating. 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 Ak-shirak 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.
To the south of the Tien Shan, the Pamirs mountain range located primarily in Tajikistan has many thousands of glaciers, all of which are in a general state of retreat. During the 20th century, the glaciers of Tajikistan lost 20 km³ (4.8 mile³) of ice. The 70 km (43 mile) long Fedchenko Glacier, which is the largest in Tajikistan and the largest non-polar glacier on Earth, lost 1.4% of its length, or 1 km (0.6 mile), 2 km³ (0.5 mile³) of its mass, and the glaciated area was reduced by 11 km² (4.2 mile²) during the 20th century. Similarly, the neighboring Skogatch Glacier lost 8% of its total mass between 1969 and 1986. The country of 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.
![These glaciers in New Zealand have continued to retreat rapidly in recent years. Notice the larger terminal lakes, the retreat of the white ice (ice free of moraine cover), and the higher moraine walls due to ice thinning. [Photo.]](http://en.wikipedia.org/wiki/Image:170.12806E_43.67770S.gif "These glaciers in New Zealand have continued to retreat rapidly in recent years. Notice the larger terminal lakes, the retreat of the white ice (ice free of moraine cover), and the higher moraine walls due to ice thinning. [Photo.]")
In New Zealand the mountain glaciers have been in general retreat since 1890, with an acceleration of this retreat since 1920. Most of the glaciers have thinned measurably and have reduced in size, and the snow accumulation zones have risen in elevation as the 20th century progressed. During the period 1971–75, Ivory Glacier receded 30 m (98 ft) at the glacial terminus, and about 26% of the surface area of the glacier was lost over the same period. Since 1980 numerous small glacial lakes were created 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.
Several glaciers, notably the much visited Fox and Franz Josef Glaciers in New Zealand, have periodically advanced, especially during the 1990s, but the scale of these advances is small when compared to 20th-century retreat. 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 increased snowfall and cooler temperatures, are rapidly echoed in a corresponding advance, followed by equally rapid retreat when those favorable conditions end.
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. Aside from the few tidewater glaciers such as Taku Glacier, that are in the advance stage of their tidewater glacier cycle prevalent along the coast of Alaska, virtually all the glaciers of North America are in a state of retreat. The observed retreat rate has increased rapidly since approximately 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.
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 in the more than 700 glaciers of the North Cascades, a portion of the range between the Canadian border and I-90 in central Washington. These glaciers store as much water as that contained 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 yd³).
As recently as 1975, many North Cascade glaciers were advancing due to cooler weather and increased precipitation that occurred from 1944 to 1976. However, by 1987 all the North Cascade glaciers were retreating, and the pace of the glacier retreat has increased each decade since the mid-1970s. Between 1984 and 2005, the North Cascade glaciers lost an average of more than 12.5 m in thickness and between 20% and 40% of their volume.
Glaciologists researching the North Cascades glaciers have found that all 47 monitored glaciers are receding and that four glaciers—Spider Glacier, Lewis Glacier (pictured), 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 shrank from 3.1 km² (1.19 miles²) in 1958 to 0.9 km² (0.34 miles²) in 2002. Similarly, the Boulder Glacier on the southeast flank of Mount Baker retreated 450 m (1,476 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.
On the sheltered slopes of the highest peaks of Glacier National Park in Montana, its eponymous glaciers are diminishing rapidly. The area of each glacier has been mapped by the National Park Service and the U.S. Geological Survey for decades. Comparing photographs taken in the mid-19th century with contemporary images provides ample evidence that the glaciers in the park have retreated notably since 1850. 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 miles²) area of Glacier National Park covered by glaciers in 1850 remained covered by 1993.
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. Schoolroom Glacier, located on the northwest flank of Grand Teton, one of the more easily reached glaciers in the park, is expected to disappear by 2025.
![The Athabasca Glacier in the Columbia Icefield of the Canadian Rockies, has retreated 1,500 m in the last century. Also [recent animation].](http://encycl.opentopia.com/enimages/thumb/4805/4804597/250px-Athabasca_Glacier_BenWBell.jpg "The Athabasca Glacier in the Columbia Icefield of the Canadian Rockies, has retreated 1,500 m in the last century. Also [recent animation].")
In the Canadian Rockies, the glaciers are generally larger and more widespread than they are to the south in Montana. One of the more accessible glaciers in the Canadian Rockies is the Athabasca Glacier, which is an outlet glacier of the 325 km² (125 miles²) Columbia Icefield. The Athabasca Glacier has retreated 1500 m (4,921 ft) since the late 19th century. The rate of retreat for this glacier 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 (4.63 miles²), and retreated rapidly during the first half of the 20th century, stabilized by 1966, and resumed shrinking in 1976.
There are thousands of glaciers in Alaska, though only a relative few of them have been named. The Columbia Glacier near Valdez in Prince William Sound has retreated 15 km (9.3 miles) in the last 25 years. Icebergs calved off this glacier were a partial cause of the Exxon Valdez oil spill, as the oil tanker had changed course to avoid the icebergs. The Valdez Glacier is in the same area, and though it does not calve, it 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."
The Juneau Icefield Research Program has monitored the 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 (1,902 ft). Numerous other glaciers in the immediate vicinity are also mostly in a state of general retreat. Herbert, Eagle, Norris, East Twin and West Twin glaciers have all retreated from 570 m (1,879 ft) to 1,740 m (1.08 miles) since 1946. Of the glaciers in this region, only the Taku Glacier has advanced. 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 miles) from reaching Taku Point and blocking Taku Inlet. The advance of Taku Glacier averaged 17 m (55 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.
A large region of population surrounding the central and southern Andes of Argentina and Chile reside in arid areas that are dependant 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 full kilometer (0.6 miles) since the early 1990s and 10 km (6.2 miles) since the late 1800s. It has also been observed that Patagonian glaciers are receding at a faster rate than in any other region in the world.
Polar regions
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% 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 (1.8 miles) 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.
The northern Atlantic island nation of Iceland is home to the Vatnajökull, which is the largest ice cap in Europe. The Breiðamerkurjökull Glacier is one of the Vatnajökull outlet glaciers, and had receded by as much as 2 km (1.2 miles) between 1973 and 2004. In the early 20th century, Breiðamerkurjökull extended to within 250 m (820 ft) of the ocean, but by 2004 Breiðamerkurjökull's terminus had retreated three kilometers (1.86 miles) further inland. This glacier retreat exposed a rapidly expanding lagoon that is filled with icebergs calved from its front. The lagoon is 110 m (360 ft) deep and nearly doubled its size between 1994 and 2004. All but one of the Vatnajökull outlet glaciers, roughly 40 named glaciers in all, were receding as of 2000.
The Canadian Arctic islands have a number of substantial ice caps, including Penny and Barnes Ice Cap on Baffin Island, Bylot Ice Cap on Bylot Island, and Devon Ice Cap on Devon Island. All of these ice caps have been thinning and receding slowly. The Barnes and Penny ice caps on Baffin Island have been thinning at over 1 m (3.1 ft) per year in the lower elevations from 1995 to 2000. Overall, between 1995 and 2000, ice caps in the Canadian Arctic lost 25 km³ (6 miles³) of ice per year.
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 Hansbreen Glacier on Spitsbergen retreated 1.4 km (0.87 miles) from 1936 to 1982 and another 400 m (1,312 ft) during the 16-year period from 1982 to 1998.
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 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 Jakobshavn Isbræs—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 miles), accelerating from 21.33 m (70 ft) per day to 33.5 m (110 ft) per day during that period.
Jakobshavn Isbræ in west Greenland, a major outlet glacier of the Greenland Ice Sheet, is the fastest moving glacier in the world over the past half century. It had been moving continuously at speeds of over 24 m (78 ft) per day with a stable terminus since at least 1950. In 2002, the 12 km (7.5 mile) 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 (131 ft) per day in the summer of 2005. Not only has Kangerdlugssuaq retreated, it has also thinned by more than 100 m (328 ft).
The rapid thinning, acceleration and retreat of Helheim, Jakobshavns 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. The current flow speeds at the terminus are too fast to be caused solely by internal deformation of the ice, implying that an increase in basal sliding forced by additional meltwater production is the probable cause of the velocity increases. This was termed the Jakobshavns Effect by Terence Hughes at the University of Maine in 1986.
The Climate of Antarctica is one of intense cold and great aridity. Most of the world's freshwater ice is contained in the great ice sheets that cover the continent of Antarctica. The most dramatic example of glacier retreat on the continent is the loss of large sections of the Larsen Ice Shelf on the Antarctic Peninsula. 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 (965 miles²) of its area from 1995 to 2001. In a 35-day period beginning on 31 January 2002, about 3,250 km² (1,254 miles²) of shelf area disintegrated. The ice sheet is now 40% the size of its previous minimum stable extent.
Pine Island Glacier, an Antarctic outflow glacier that flows into the Amundsen Sea, thinned 3.5 ± 0.9 m (11.5 ± 3 ft) per year and retreated a total of 5 km (3.1 miles) in 3.8 years. The terminus of the Pine Island Glacier is a floating ice shelf, and the point at which it is afloat is retreating 1.2 km (0.74 miles) per year. This glacier drains a substantial portion of the West Antarctic Ice Sheet and has been referred to as the weak underbelly of this ice sheet.
Impacts of glacier retreat
The continued retreat of glaciers will have a number of different quantitative impacts. 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.
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 Stubai and Pitztal Glaciers were covered with plastic. In Switzerland plastic sheeting is also used to reduce the melt of glacial ice used as ski slopes.
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 worlds oceans, may impact existing fisheries upon which humans depend as well.
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. The British Antarctic Survey has determined from climate modeling that for at least the next 50 years, snowfall on the continent of Antarctica should continue to exceed glacial losses from global warming. The amount of glacial loss on the continent of Antarctica is not increasing significantly, and it is not known if the continent will experience a warming or a cooling trend, although the Antarctic Peninsula has warmed in recent years, causing glacier retreat in that region.
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