Recent Global Glacier Retreat OverviewIn historic times, glaciers grew during the Little Ice Age, a cool period from about 1550 to 1850. Subsequently, until about 1940, glaciers around the world retreated as climate warmed. Glacier recession declined and reversed, in many cases, from 1950 to 1980 as a slight global cooling occurred. Since 1980, glacier retreat has become increasingly rapid and ubiquitous, so much so that it has threatened the existence of many of the glaciers of the world. This process has increased markedly since 1995, leading to such bizarre steps as covering sections of Austrian alpine glaciers with plastic to retard melting. 
The recession of mountain glaciers, has been used to provide qualitative support to the rise in global temperatures since the late 19th century [2]. Many glaciers are being lost to melting further raising concerns about future local water resources in these glacierized areas. Glaciers are the perfect summer water supply in alpine regions providing the highest runoff during warm dry periods when other water sources are at a minimum. The smaller the glacier area to melt, the less the runoff, the greater the change in alpine streamflow and the higher the stress on man and aquatic users of this resource. The Lewis Glacier, North Cascades pictured at right after melting away in 1990, reducing streamflow in its watershed by 40% in August.
Glaciers respond to climate in an attempt to achieve equilibrium. A glacier
advances due to a climate cooling/snowfall increase that causes positive
mass balance. This advance increases the glaciers area at low
elevation where ablation is highest, returning the glacier to equilibrium. A climate warming/snowfall decrease leads to negative mass
balances and glacier retreat. To reestablish equilibrium a retreating
glacier must lose
For a detailed review of glacier retreat also see Glacier Retreat at Wikipedia North AmericaCascade RangeThe
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 in 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 the lakes and reservoirs in the rest of the state
and provide much of the stream and river This recession is widespread. All 47 monitored glaciers are
receding and four have disappeared completely. The White Chuck
Glacier (near
Glacier Peak) is a particularly dramatic example. It shrank
from 3.1 km2 in 1958 to 0.9 km2 in 2002.
The Boulder Glacier on the southeast flank of
Mount Baker retreated 450 m from 1987 to 2005 leaving
unvegetated terrain behind. This retreat has occurred during a
period of less winter snowfall and higher summer temperatures.
Winter snowpack has declined 25% since 1946 and summer
temperatures have risen 1.2 degrees Fahrenheit (0.7 °C) during
the same period. Four glaciers have been observed to disappear
since 1985; Spider Glacier, Lewis Glacier, Milk Lake Glacier and
David Rocky MountainsIn the
Canadian Rockies, the
Athabasca Glacier, one of the outlet glaciers of the 325 km²
Columbia Icefield, has retreated 1500 m since the late 19th
century. This retreat has become more rapid after 1980,
following a period of slow retreat from 1950-1980. The Peyto
Glacier, covering an area of about 12 km², retreated rapidly
during the first half of the 20th century, stabilized by 1966
and resumed shrinking in 1976.
[13] Illecillewaet Glacier in
British Columbia's
Glacier National Park (Canada) has retreated 2000 m since
first photographed in 1887 below.
On the sheltered slopes of the highest peaks of Glacier National Park, 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. [14] Every glacier has retreated notably in the last 140 years. The larger glaciers are now approximately a third of their size when first studied in 1850, and numerous smaller glaciers have disappeared completely. Only 27 % of the 99 km² area of Glacier National Park covered by glaciers in 1850 remained by 1993. Average glacier area in the accumulation zone for September 1993 was 35%, 65% is needed for equilibrium, indicating negative mass balances for most glaciers and continued shrinkage. An increase of approximately 1 degree Celsius (2 °F) in average summer temperatures is reflected in reduced glacier sizes. A computer model indicates that present rates of increasing warming will eliminate all glaciers in Glacier National Park by 2030. Even with no additional warming over that which has already occurred, the glaciers are likely to be gone by 2100. The semiarid climate of Wyoming still manages to support about a dozen small glaciers within Grand Teton National Park which all show evidence of recession over the past 50 years. One of the more easily reached of the glaciers in the Park known as "Schoolroom Glacier" is expected to be gone in 25 years. [15] 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 over that period. Photographs indicate that the glaciers today are only half the size as when first photographed in the late 1890's. Research also indicates that the glacial retreat was proportionately greater in the 1990s than in any other decade of the last 100 years. [16] 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 25 % of its volume since 1980 and 50 % since 1920. Glaciologists think the remaining glaciers in Wyoming will disappear by the middle of the 21st Century, if the current trends continue. AlaskaValdez Glacier has thinned 300 feet over the last century and the unvegetated brown areas near the glacial margins have been exposed due to the glacier thinning and retreating over the last 2 decades of the 20th centuryAlaska is home to thousands of glaciers, most still unnamed.
One of the more famous glaciers is
Columbia Glacierr, near
Valdez. It was a course change to avoid icebergs from this
glacier that ultimately resulted in the 1989
Exxon Valdez oil spill. Columbia Glacier, which terminates
in a grounded calving margin in
Prince William Sound in central coastal Alaska, has
retreated 15 km in the last 25 years. The Valdez Glacier
pictured is in the same area, does not calve but has retreated The Juneau Icefield Research Program has monitored the outlet glaciers of the Juneau Icefield since 1946. On the west side of the icefield from 1946-2005 the terminus of the Mendenhall Glacier, which flows into suburban Juneau has retreated 580 m, Herbert Glacier five miles north has retreated 910 m, Eagle Glacier another five miles north has retreated 1090 m. On the south side of the icefield Norris Glacier retreated 1740 m the East Twin Glacier 720 m and the West win Glacier 570 m. Only the Taku Glacier has advanced. This glacier was advancing in 1890 when viewed by John Muir and had a large calving front. By 1963 the glacier had advanced 3.7 miles. In 1948 the fjord had filled in and the glacier no longer calved. It was just like finishing payment on a home mortgage, the glacier no longer lost icebergs and was able to continue its advance of a further 0.5 miles. In 2005 the glacier is only 0.93 miles from reaching Taku Point and blocking Taku Inlet, and is advancing at a rate of 17 m/year. The mass balance was very positive for the 1946-1988 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. [17] Glacier retreat is driven by negative mass balance. Long term mass balance records from Lemon Creek Glacier show declining mass balance with time [18]. The mean annual balance for this glacier was –0.23 m/yr 1957-1976. Mean annual balance has been increasingly negative since 1977, averaging -0.78 m/yr. The record is particularly negative since 1990, -1.04 m/yr, indicating even more rapid glacier retreat. Repeat glacier altimetry 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/yr) and 1995 to 2001 (-1.8 m/yr). [19] This is a systemic trend with loss in mass equaling loss in thickness, which leads to increasing retreat. Beginning in the 1990's, using a laser measuring device mounted on the underside of an airplane, researchers compared glacier altitude differences with ground survey maps created in the 1950's. 85% of the glaciers flown over stretching from Alaska to Washington state had a reduction in altitude, and therefore, a thinning of the glacial mass. Further flights since then indicate that this thinning is accelerating and is now double what it was in the 40 years before the mid 1990's. [20] In Denali National Park the terminus of the Toklat Glacier is retreating 24 m/year and the Cantwell Glacier 10 m/year. There are many surging glacier in the Park and in Alaska whose terminus responses are part due to climate and part due to surging behavior. Europe: Alps The
World Glacier Monitoring Service reports on changes in the
terminus position of glaciers from around the world every 5
years.
[4], 103 of 110 glaciers examined are retreating.
Similarily, in
Austria 95 of 99 glaciers were retreating, in
Italy
all 69 observed glaciers were in retreat and in
France all 6 were retreating. French glaciers experienced a
sharp retreat in the years 1942-53 followed by advances up to
1980, then further retreat from 1982. As an example the
Argentière Glacier and
Blanc Glacier have receded by 1150 and 1400 meters
respectively since 1870. The largest glacier
Chamonix remember the In the Kebnekaise Mountains of Northern Sweden of sixteen glaciers examined from 1990-2001, 14 are retreating, one is advancing and one is stable [7] During the 20th century glaciers in Norway retreated as did glaciers in other parts of the world at the end of the Little Ice Age. Most Norwegian glaciers did have brief periods of advance around 1910, 1925 and in the 1990's. In the 1990s 11 of 25 Norwegian glaciers observed advanced due to several winters in a row with precipitation above normal. Since 2000, Norwegian glaciers have decreased significantly. This resulted from several consecutive years of little winter precipitation, and record-warm summers in 2002 and 2003. By 2005 Only 1 of the 25 glaciers was advancing, two were stationary and 22 were retreating. Engabreen has retreated 179 meters since 1999, while Brenndalsbreen and Rembesdalsskåka have retreated 116 and 206 meters since 2000. At Briksdalsbreen the glacier retreated 96 m in 2004, this is the largest annual retreat recorded since monitoring started in 1900. Since 1999, the glacier has retreated 176 meters. [8] IcelandThe Breidamerkurjökull, one of the glaciers that is an outlet of the Vatnajökull, the largest ice cap in Europe, has receded by as much as 2 km since 1973. A hundred years ago Breidamerkurjokull, extended to within 250 m of the ocean, Today, Breidamerkurjokull's terminus is three kilometers from the ocean. The glacier retreat has exposed a rapidly expanding lagoon, which is filled with icebergs calved from its front. The lagoon is 350 feet deep and has nearly doubled its size during the past decade. All but one of the Vatnajokull outlet glaciers, roughly 40 named glaciers in all, are receding as of 2000. [9] GreenlandDespite their proximity and importance to human populations, the mountain and valley glaciers of temperate latitudes amount to a small fraction of glacial ice on the earth. About 99% is in the great ice sheets of polar and subpolar Antarctica and Greenland. These continuous continental-scale ice sheets, 3 kilometers or more in thickness, cap 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. Glacier recession has been observed in these outlet glaciers. This can increase the ice flow rate and destabilize the mass balance of the ice sheet that is their source. In Greenland the last five years has brought retreat to several very large glaciers that had long been stable. Three glaciers that have been researched, Helheim, Jakobshavns and Kangerdlugssuaq Glaciers, 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 has remained in the same place for decades. But in 2001 it began retreating rapidly, retreating four and a half miles (7.2 km) between 2001 and 2005. It has also accelerated from 20 m/day to 32 m/day. [21] Jakobshavns Isbrae in west Greenland, a major outlet glacier of the Greenland Ice Sheet, is generally considered the fastest moving glacier in the world. It had been moving continuously at speeds of over 24 m/day with a stable terminus since at least 1950. In 2002, the 12 km long floating terminus entered a phase of rapid retreat. The ice front started to break up and the floating terminus disintegrated. The glacier accelerated to over 30 m/day.[22] The rapid thinning, acceleration and retreat of these three large glaciers 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. [Geophysical Research Letters, Volume 13, Issue 1, p. 46-48] AfricaWith almost the entire continent of Africa located in the temperate zone, the few places that glaciers do exist are restricted to two isolated peaks and the Ruwenzori Range. What has been popularized as the "snows of Kilimanjaro" on Mount Kilimanjaro, which at 19,340 feet (5,895 m) is the highest peak on the continent, may be a thing of the past in less than 30 years. Since 1912, the glacier cover on the summit of Kilimanjaro has apparently retreated 75 % and just from the period of 1984 to 1998, one section of glacier receded 300 meters vertically. A report from March 2005 indicated that there is almost no remaining glacial ice on the mountain and it is the first time much of the surface of the summit has been observable in 11,000 years. [23] Observers believe that there will be no more glacial ice on the summit of Kilimanjaro by the years 2015 to 2025. Mount Kenya which at 17,057 feet (5,199 m) is the second tallest mountain on the continent and has up to a dozen small glaciers has shown a loss of area at least 45 % since the middle part of the 20th century. The Ruwenzori Range which rise to 16,761 ft (5,109 m), are to the west of the isolated peaks of Kilimanjaro and Kenya. These mountains are oftentimes cloud capped, making satellite imagery difficult and the political dynamics of the surrounding region have made access complicated at best over the past few decades. However, photographic evidence demostrates a marked reduction in glacially covered regions over the past century. It is expected that due to their closer distance to the heavy moisture of the Congo region, the glaciers in the Ruwenzori Range may recede at a slower rate than either Kilimanjaro or Kenya. HimalayasNasa image shows the formation of numerous glacial lakes at the termini of receding glaciers in Bhutan Himalaya.A WWF report, An Overview of Glaciers, Glacier Retreat and
Subsequent Impacts in Nepal, India and China (2005),
[24] concluded that 67% of Himalyan glaciers are retreating
rapidly. In examining 612 glaciers in China, 50% were found to
be retreating in 1970 and 95% after 1990. Some of the more
famous glaciers in the area indicate the trend.
Khumbu Glacier, the main route up Mount Everest]], has
retreated 5 km since 1953.
Rongbuk Glacier, draining the north side of Mount Everest
into Tibet, has been retreating 20 m/yr.
Gangotri Glacier in India has been retreating 30 m/yr in the
early 2000s. Oceania The vast moraine wall is evidence of the retreat of the Mueller glacier, which is covered in rubble. In the distance a further lake and moraine wall show where the glacier has retreatedIn New Zealand the mountain glaciers have been in a general recession since 1890, with an acceleration of this recession after 1920. Most of the glaciers have been reduced in size and the accumulation zone had a corresponding rise to higher elevations as the 20th century progressed. During the period of 1971 to 1975, Ivory Glacier was reduced 30 m at the glacial terminus and the loss of ice during the period was 13.9 x 106 m3. 26 % of the surface area of the glacier was lost over the same period. Since 1980, numerous small glacial lakes were created behind the terminal moraines of several glaciers and the glacier thickness has been reduced. Glaciers such as Classen, Godley and Douglas now all have proglacial lakes below their new terminal locations due to the glacial retreat over the past 20 years. Satellite imagery indicates that these lakes are expanding in area as well. Several glaciers, notably the much visited Foxx and Franz Josef Glaciers, have periodically advanced (especially during the 1990s) but the scale of these advances is small compared to 20th century retreat. These rapid flowing large glaciers with steep trunks have been very reactive to small mass-balance changes. A few years of favorable conditions are rapidly echoed in a corresponding advance, followed equally rapidly by renewed retreat when those favorable conditions end. [25] USGS Puncak Jaya glaciers 1936 and 1972. Left to right: Northwall Firn, Meren Glacier, and Carstensz Glacier. USGS  On the large island of
New Guineaa, there is photographic evidence of massive
glacier recession since the region was first extensively
photographed 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
level of moisture which has fallen during the 20th century.
Therefore, the glacial retreat evidenced can only be attributed
to a general warming trend. The 7 km AndesFurther south in Peruu, the Andes are much taller overall and there are 722 glaciers covering an area of 723.4 km². Research in this region of the Andes is less conclusive but indicate that between 1977 and 1983, a glacial recession of 7 % occurred. [29][30]] A large region of population surrounding the central Andes of
Argentina and
Chile
reside in arid areas that are dependant on water supplies from
melting glaciers. The water from the glaciers also supply rivers
that have in some cases been dammed for
hydroelectric power. Some researchers think that by 2030,
many of the large ice caps on the highest Andes will be gone, if
current trends continue. In
Patagonia on the southern tip of the continent, the large
ice caps have been shown to have retreated a full kilometer
since the early 1990s and 10 km since the late 1800s. It has
also been claimed that Patagonia glaciers are receding at a
faster rate than any other region in the world.
[31]
Antarctica The collapsing Larsen B Ice Shelf is similar in area to the U.S. state of Rhode Island. The most dramatic glacier recession is the loss of
large sections of the
Larsen Ice Shelf on the Antarctic Peninsula. The
collapse has been due to warmer melt season temperatures
leading to surface melting and the formation of shallow
ponds of water on the ice shelf. The
Larsen Ice Shelf lost 2,500 square kilometers from
1995 to 2001. Then, a total of about 3,250 km2
of shelf area disintegrated in a 35-day period beginning
on
31 January 2002. The ice sheet is now 40 percent the
size of its previous minimum stable extent.
[32] An examination of 244 marine glacier fronts on the
Antarctic Peninsula and associated islands over the past 61 years
indicates that 87% have retreated. A clear boundary between
mean advance and retreat has migrated progressively southward.[34] Pine Island Glacier, which flows into the Amundsen Sea thinned 3.5 ± 0.9 meters per year and retreated five kilometers in 3.8 years. The end of the glacier is a floating ice shelf. The location where the glacier becomes afloat is retreating 1.2 km/year. This glacier drains a substantial portion of the West Antarctic Ice Sheet and has been called the weak underbelly of this ice sheet. [[33]. Dakshin Gangotri Glacier is a small outlet glacier of the continental ice sheet. It receded at a rate of 7 m/decade from 1983 to 2002. |
enough of its highest ablating sections, usually at the
lowest elevations, so that accumulation in the accumulation zone once again
balances ablation, reestablishing equilibrium.. If a glacier cannot retreat to a point where equilibrium
is established, it is in disequilibrium with the climate system. A glacier
that is in disequilibrium with present climate will melt away with a
continuation of this climate. The chart at left indicates that
global mass balance ( Data from World Glacier Monitoring Service 
flow in the dry summer
months, some 870,000 m³. As recently as 1975, many
North Cascade glaciers were advancing due to cooler/wet
weather during the 1944-1976 period. However, by 1987, all North
Cascade glaciers were retreating. However, since 1976 these
glaciers have receded rapidly. Between 1984 and 2005, they have
lost an average more than 9.5 m in thickness and 20 to 40% of
their volume.
Glacier. Currently most North Cascade glaciers are in
disequilibrium, meaning they cannot retreat to a point of new
equilibrium and can only melt away with the present climate.
throughout the century. Calving glaciers can retreat faster via
calving icebergs, than glaciers that do end in a calving front.
Bossons Glacier coming almost as far
as the road. It has lost 1200 meters in length. This shrinking
is not without risks. Glacial lakes have formed at the foot of
the Mer de Glace. The lakes are held behind
moraine dams. If the natural dams that hold this meltwater
back break, it could cause widespread flooding in the valley
below. In 1892 the lake of the Glacier de Tête Rousse burst
emptying some 200,000 m33 of water and killing 200
people in Saint Gervais. Ski areas in Austria have covered areas
of the
Stubai and Pitztal Glacier with plastic wrap to retard
melting of the glaciers that their ski areas utilize. Since
1980, 20% of the area of Swiss glaciers has been lost. The
Grosser Aletsch Glacier is the largest glacier in Switzerland
and has retreated 2600 m since 1880. The rate of retreat has
increased after 1980, with 800 m or 30% of the total retreat
occuring in the last 25 years
.