Glacier retreat since 1850

Since the middle of the 19th century, a significant decline in glaciers has been observed almost worldwide . This process is called glacier retreat or glacier melt . What is meant by this is a long-term loss of mass of the glaciers and not the snowmelt in the mountains and high altitudes every year in spring, nor basically the melting in the depletion area , which in glaciers that are in equilibrium with the climate is to the same extent as the mass gain in the nutrient area occurs. An important parameter for evaluating the glacial recession is that of glaciologists collected mass balance . The behavior of the glacier is described by the glacier dynamics . Glacier retreat is particularly related to man-made global warming .

The mass balance of glaciers worldwide has been clearly negative since at least 1960, as the diagram shows.

The map compares the mass balance of 173 glaciers distributed around the world and measured at least five times between 1970 and 2004: 83% of all glaciers shrank in this period, the average rate of retreat of all glaciers was 31 cm per year.

introduction

The majority of all glaciers have lost some of their mass and area in the past decades. With a few exceptions, all regions are affected, from the tropics to the mid-latitudes to the polar ice caps . The Alpine glaciers, for example, have shrunk by around a third of their area over the past 150 years, their volume declined by almost half between 1901 and 2011. This can be seen directly in paintings, drawings or old photographs. The latter show impressively the different glacier areas from then compared to today. A decline in ice can also be observed in the polar regions , where larger ice shelves have increasingly broken off in recent years . Growing glaciers were mainly observed in Norway, New Zealand, Iceland and eastern Antarctica towards the end of the 20th century. This trend, which existed for a short time in the 1980s and 1990s and was based on locally changed precipitation patterns, has either reversed or at least flattened significantly since around the year 2000, at least in the first two regions. According to the Alpine Association, the Kalser Bärenkopf -Kees and the Kleinelend -Kees, two smaller glaciers, grew slightly in Austria in 2012/2013 .

The glaciers follow the observed climate and temperature fluctuations worldwide. While the global temperature increase in the first half of the 20th century is attributed to a mixture of different natural and anthropogenic factors (fluctuations in solar variability , low volcanic activity and the first significant increase in greenhouse gases ), the accelerating temperature increase since 1970 is generally evident increasing anthropogenic greenhouse effect . The rise in temperature leads to the retreat of glacier ice - just one of many consequences of global warming . An indirect effect of anthropogenic climate change is a change in the distribution of precipitation, which can also influence the mass balance of glaciers.

The consequences of the phenomenon harbor considerable risks for a proportion of the present and future world population that is currently difficult to estimate. First of all, there is an increased risk of flooding in the affected areas due to rising river levels and more frequent eruptions from glacial lakes . This results in a worsening water shortage in certain regions. The increasing runoff of the glacier water also leads to a global rise in sea ​​level and thus also threatens people who do not live directly in the area of ​​influence of glaciers.

causes

The decisive factor for the continued existence of a glacier is its mass balance , the difference between accumulation (such as snowfall, deposition of snowdrifts and avalanches , condensation of atmospheric water vapor and freezing of rainwater) and ablation (melt, sublimation and avalanche breakup). Each glacier consists of a nutrient and a consumption area. In the nutrient area (accumulation area), at least part of the snow is retained even during the summer and is then transformed into glacier ice. In the depletion area (ablation area), on the other hand, ablation predominates over replenishment from snow. These two areas are separated by the equilibrium line . Along this line, ablation in summer corresponds to accumulation in winter.

In the event of climate change, both air temperatures and precipitation in the form of snow can change and thus shift the mass balance. These indicators are currently providing information about the causes of glacier retreat:

• In most regions of the world, temperatures rise mainly as a result of human greenhouse gas emissions . According to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) published in 2007 , the global average air temperature near the ground rose by 0.74 ° C (± 0.18 ° C) between 1906 and 2005. The heating is with increasing proximity to the poles (see polar amplification ) and with increasing altitude in the mountains (one speaks of the elevation dependent warming , dt. Height-dependent heating ) more pronounced.
• In contrast to air temperature, there are no clear trends for precipitation. Canada, Northern Europe, the West Indies and Eastern Australia in particular received more precipitation during the 20th century. Declines of up to 50% were particularly measured in West and East Africa and in West Latin America. It is therefore necessary to examine separately for each of the regions concerned which factors are responsible for the retreat of the glaciers and, if applicable, dominant.

Deposited cryoconite stains the bed of melt watercourses in the Greenland ice dark. Cryoconite can also be seen as gray contamination on the ice surface. Above in the picture: a light, 5 to 10 meter wide meltwater stream from a glacial lake. Photo taken from a helicopter on July 21, 2012 by Marco Tedesco, who attributes the increasing darkening of the ice to climate change.

• Cryoconite is a dark, biogenic surface dust on snow and ice that is transported over long distances by winds in the atmosphere and is commonly seen on glaciers around the world. Because of its dark color, cryoconite significantly reduces the surface reflection of sunlight and thus accelerates or initiates the melting of the glaciers. Although cryoconite consists of mineral particles (soot, carbon and nitrogen) and organic matter, the organic fraction is more important in terms of the effect on melting because it is often biologically active and makes up the bulk of cryoconite. This organic material consists partly of photosynthetically active microorganisms such as cyanobacteria or tardigrade , as has been demonstrated on the Rotmoosferner . At least in the Alps, when cryoconite occurs, the also dark-colored glacier flea is observed, which feeds on the biological material that has been introduced, so that a growing, dark-colored flora and fauna develops in the glacier that lives in the meltwater and multiplies.

A glacier reacts with growth to a cooling or an intensification of the snowfall, which causes a positive mass balance. As a result, the glacier area in the Zehr area, where the ablation is highest, increases. Thus the glacier gains a new equilibrium. There are currently a few glaciers growing. The slow growth rate, however, suggests that they are not far from equilibrium. The glacier reacts to global warming such as global warming or a decrease in snowfall, which lead to a negative mass balance, with a decline. As a result, the glacier loses parts of its mostly deeper ablation area, so that accumulation and ablation are balanced out again. However, if a glacier cannot retreat to a new point of equilibrium, it is in perpetual imbalance and, if this climate persists, will melt completely.

The number of glacier advances increased from 1100, and has been falling unusually rapidly since the beginning of industrialization

In the course of climate history, for various reasons, there have repeatedly been natural climate changes with advances and retreats of glaciers. Towards the end of the Middle Ages, the number of glacier advances began to increase. At the end of the so-called Little Ice Age around 1850, the global average temperature had risen slightly, which may explain part of the global glacier retreat in the following decades. From 1940, average temperatures remained relatively stable or decreased slightly, to which most glaciers responded with relative stagnation or growth. The glacier retreat that started again in the late 1970s as a result of the rapidly rising air temperatures in most regions and has accelerated in recent years is mainly attributed to anthropogenic influences and cannot be regarded as part of natural climate change.

The initial trigger for the retreat of glaciers from 1850 onwards, at least in the Alps, can be assumed to be a lowering of the albedo of the glaciers due to soot particles released in the course of industrialization . If only the climatic factors were considered, the glaciers would have grown until around 1910. The current rapid decline, observable in all mountain regions of the world, at a time when the change in the Earth's orbit parameters tends to favor glacier advances, is very unusual for the Holocene and a clear sign of the current man-made climate changes.

Glaciers as climate indicators

Global annual mean temperatures since 1880 near the earth's surface, relative to the mean value for the years 1951 to 1980. The graph is based on measurements of the near-surface air temperature by weather stations and the sea surface temperature by ships and satellites. There are clearly two phases of increase between 1910 and 1940 and after 1980. Source: NASA GISS .

The expansion and contraction tendencies of glaciers, which are practically never in a state of rest, play an important role in climate research . The glaciers exist in a back and forth between retreat and advance. As more precipitation falls or temperatures drop, they usually advance further. They shrink as the amount of precipitation decreases and temperatures rise. The alpine glaciers have been shrinking since around 1850, even if smaller glaciers in this region in particular had advanced a little further around 1920 and around 1980.

As a rule, smaller glaciers are “more sensitive to the climate” and can therefore be used as indicators for short-term events. Likewise, glaciers in maritime regions are more suitable as climate indicators for shorter-term events than glaciers in continental regions. This is because, in continental regions with low humidity, a considerable part of the glacier ice experiences ablation through evaporation, but this in turn dissipates the heat of evaporation. This heat is then missing to melt the glacier ice.

Within a climatic region, however, glaciers do not only react differently to changes due to different ice masses. The size of the surface, the nature of the subsoil, the slope and valley shape of valley glaciers, wind and windward / lee effects as well as the behavior of glacial meltwater, to name just the most important factors, also have a major influence. Nevertheless, larger glaciers in particular can be described as relatively sluggish overall, which is why they are influenced less by individual weather conditions than by climate changes over longer periods of time. Therefore, taken as a whole, they are a useful indicator of long-term temperature development. For example, the glaciologist Johannes Oerlemans reconstructed the global mean temperature over the last 400 years by evaluating changes in length of 169 glaciers spread around the world. Accordingly, moderate warming began in the mid-19th century. In the first half of the 20th century he was able to determine a warming of around 0.5 ° C.

Temperature reconstructions obtained from the ice cores EPICA and Vostok

Another peculiarity of glaciers that is important for climate research is their old age. In this way, ice cores can be extracted from them that go back several millennia and can provide information about the development of a glacier and the history of the climate . The example of Kilimanjaro given below shows that its glaciers have existed continuously for over 11,700 years and are now threatened with disappearing. Ice cores from the Antarctic and Greenland ice sheets allow a glimpse into the past even further. This allows the climate and the composition of the atmosphere to be reconstructed over several hundred thousand years.

The finds of peat and tree trunks released by the retreating glaciers, for example on the Austrian Pasterze , also show that the extent of some glaciers in earlier times (6,000–9,000 years ago) was significantly smaller than it is today. As a result, higher temperatures are assumed in times of receding glaciers. A prominent example is " Ötzi ", who died about 5300 years ago on a then ice-free yoke near Vent / Ötztal Alps and was then enclosed by a snow and ice cover, where he appeared under the ice as a result of the glacier retreat in 1991. Christian Schlüchter and Ueli Jörin from the Institute of Geology at the University of Bern went in their publication Alps without glaciers? from 2004 assumes that the little ice age from the 17th to the middle of the 19th century resulted in the largest alpine glacier expansion in the last 10,000 years and that the glaciers were a little over 50% of this period smaller than today. They came to the conclusion that the influence of solar activity on glacier development has so far been underestimated.

Global inventory of the process

The following, more detailed inventory of global glacier retreat is divided into three parts: middle latitudes, tropical zones and polar regions . This is based not only on the common geographic differentiation patterns, but also on the fact that there are special requirements for ice formation and glacier melt in these three zones. There are also specific differences for future living conditions with regard to the expected consequences of a continued melting process.

Medium latitude glacier

Medium latitude glaciers are located between either the tropic or the tropic and one of the arctic circles . In these 4,785 km wide regions, there are mountain glaciers, valley glaciers and, on higher mountains, also smaller ice caps. All of these glaciers are located in mountain ranges , u. a. the Himalayas , the Alps , the Pyrenees , the Rocky Mountains , the Patagonian Andes in South America or New Zealand . The closer the glaciers of these latitudes are to the polar regions, the more extensive and massive they are. Medium-latitude glaciers are the most thoroughly studied in the last 150 years. Like the tropical glaciers, practically all glaciers of medium latitude recede and show a negative mass balance.

Alps

In the 1970s there were around 5,150 glaciers in the Alps, covering an area of ​​2,903 km² (of which 1,342 km² in Switzerland , 602 km² in Italy , 542 km² in Austria and 417 km² in France ). A study of the development of these glaciers since 1850 comes to the result that by 1970 already 35% of the originally existing glacier area had disappeared and that this shrinkage had increased to almost 50% by 2000. This means that by the turn of the millennium, half of the area formerly covered by glaciers had already been exposed by the retreat of the ice. Between 2000 and 2015 another 1.8% of the glacier area was lost each year.

The World Glacier Monitoring Service (WGMS) reports every five years on changes in the endpoint of glaciers around the world. According to the report for the period 1995–2000, 103 of 110 examined glaciers in Switzerland , 95 of 99 glaciers in Austria , all 69 glaciers in Italy and all 6 glaciers in France declined in this five-year period .

The glaciers in the Alps are retreating faster today than they were a few decades ago : Between 2002 and 2005 , the Trift glacier lost 500 m or 10% of its previous length. The Great Aletsch Glacier , which is the longest glacier in the Alps with a length of 22.9 km, has retreated by almost 2,800 m since 1870. The last advance phase between 1588 and 1653 is recorded in relatively detail. His retreat speed has also increased. 965 m has melted since 1980. In 2006 alone it lost almost 115 m in length (in 2007 it was about 32 m). Around 2000 the Aletsch Glacier was roughly the same size as during the climatic optimum of the Roman period (200 BC to 50 AD) and was 1000 meters longer than it was around 3300 years ago during the Bronze Age optimum . Since the turn of the millennium, the surface has melted by more than eight meters per year in the lower layers, according to an analysis of satellite data from 2001–2014 at the University of Erlangen-Nuremberg .

Findings of wood and peat from glacier moraines in the Alps suggest that some glaciers sometimes retreated significantly further during the Holocene than is currently the case. Other glaciers have been shown to have been no smaller than they are today for at least 5000 years.

In the summer of 2006, the consequences of the retreat of the glaciers in the Alps became particularly evident through rockfalls on the Swiss Eiger : More than 500,000  m³ of rocks fell on the Lower Grindelwald Glacier on July 13th . In total, up to 2 million m³ of rock weighing five million tons are considered to be at risk of falling. The cause of the break-offs is, among other things, the retreat of glaciers that supported overhanging mountain parts, and the melting of constantly frozen areas ( permafrost ), in which the fissured rock was held together by the ice like an adhesive .

Scenarios for the 21st century indicate that if the average air temperature in summer (April to September) increased by 3 ° C by 2100, the glaciers in the Alps could have lost around 80% of the area still available between 1971 and 1990. That would only correspond to a tenth of the extent of 1850. A warming of 5 ° C could make practically any alpine glacier disappear.

France

The French Alpine glaciers fell sharply from 1942 to 1953, then expanded again a little until 1980, and since 1982 they have been shrinking again. For example, since 1870 the Argentière Glacier and the Mont Blanc Glacier have retreated by 1,150 m and 1,400 m respectively. The largest glacier in France, the Mer de Glace , which is now 11 km long and 400 m thick, has lost 8.3% of its length (≈1 km) in the last 130 years. In addition, it has become 27% (≈ 150 m) thinner in the central part since 1907. The Bossons Glacier in Chamonix has retreated 1,200 m since the beginning of the century.

Italy

Similar to the glaciers of the Swiss Alps, in 1980 about a third of the glaciers in the Italian Alps (in 1989 about 500 km² were glaciated), in 1999 it was 89%. From 2004 to 2005 all the glaciers in the Italian Alps retreated. By 2011 the glaciated area had shrunk to 370 km².

Austria

The glaciologist Gernot Patzelt reported on 100 glaciers observed by the Austrian Alpine Association that their decline is currently uncovering land that had been continuously glaciated for at least 1300 years. At the same time, however, he emphasized that finds of peat and tree trunks showed that these areas were previously partially covered by larch forests and that the current glacier status is historically "not exceptional".

Switzerland

Large Aletsch Glacier : left 1979, center 1991, right 2002

A study from 2005, which examined 91 Swiss glaciers , found that 84 glaciers had retreated compared to 2004 and the remaining seven showed no change, none of the examined glaciers expanded. According to the Swiss glacier measurement network, 86 of 89 glaciers evaluated in the 2006/07 measurement period lost further in length: two did not change their tongue position, and one measured a slight advance.

The Swiss glacier inventory published in November 2014 describes a 28% decline in Swiss glaciers between 1973 and 2010, which corresponds to a loss of 22.5 km³ of firn and ice. While 1,735 km² were still glaciated around 1850 and 1,307 km² in 1973, there were still 1,420 individual glaciers at the end of 2010, which took up an area of ​​only 944 km².

In the hot summer of 2015 , the glaciers in Switzerland lost many times their mass compared to previous years. According to the glaciologist Matthias Huss (Head of the Swiss Glacier Measurement Network), the total glacier area in Switzerland had halved by 2017, with a decrease from 1735 km² to 890, and 750 of 2,150 (1973) glaciers had melted. Above all, locations below 3,000 meters will soon be free of ice, and the Pizol, with a loss of two thirds of its ice since 2006, is one of the first victims of global warming . During the drought and heat of 2018 , the glacier disintegrated and will be the first to be removed from the federal government's measurement list. A memorial ceremony is planned for September 22, 2019. The Morteratsch Glacier is also disappearing: between the beginning of the annual length measurements in 1878, it lost around 2 km of its length until 1995. On average, the glacier retreated by around 17 m per year, and in the recent past the average rate of melting has increased: between 1999 and 2005 it was 30 m per year.

Pyrenees and southern Europe

The Oussoue Glacier in 1911 and 2011

Some of the southernmost glaciers in Europe are located in the Pyrenees, on the border between France and Spain. Compared to other regions, the glaciated area is very small there. Due to their southern location, mostly at a low altitude, and their small area, the Pyrenees glaciers are particularly vulnerable to climate change. Most of the Pyrenees glaciers advanced by the middle of the 19th century, and have been retreating since then, at a drastic rate since around 1980.

Between 1850 and 2016, the Pyrenees glaciers lost almost 90% of their area: they fell from a total of 20.6 km² to just 2.4 km². Their number fell from 52 to 19. Of the remaining glaciers, four had an area of ​​more than 0.1 km² in 2016: the Aneto glacier (0.51 km²), the Monte Perdido glacier (0.38 km²), the Oussoue glacier on Vignemale (0.37 km²) and the Maladeta glacier (0.29 km²). Most glaciers are in critical condition.

Outside the Alps and Pyrenees, there is another relic in the Apennines (Italy), the Calderone Glacier , which has lost more than 90% of its volume since 1794, and several micro-glaciers in the Balkans (in Montenegro , Albania , Bulgaria ). As the warming progresses, the European glaciers south of the 44th parallel, including those in the Marine Alps and the Slovenian Limestone Alps , will disappear.

Northern Europe

Jostedalsbreen water released in summer 2004

The glaciers are not only disappearing in the Alps, but also in other areas of Europe. The northern Skanden in northern Sweden reach a height of up to 2,111 m ( Kebnekaise ). Between 1990 and 2001, 14 of the 16 glaciers examined in a study receded, one of the remaining two grew and one remained stable. Also in Norway , where there are 1,627 glaciers covering an area of ​​approx. 2,609 km², glacier retreat, interrupted by a few periods of growth around 1920, 1925 and in the 1990s, can be observed. In the 1990s, 11 out of 25 observed Norwegian glaciers grew because the winter rainfall was above average for several years in a row.

Since 2000, the glaciers have been receding significantly due to several years of low winter precipitation and several hot summers (2002 and 2003). Overall, there was a sharp decline after the 1990s. Until 2005, only one of the 25 observed glaciers grew, two remained unchanged and the remaining 22 retreated. In 2006, the mass balance of the Norwegian glaciers was very negative: of 26 glaciers examined, 24 disappeared, one showed no changes in length and one grew. For example, the Norwegian Engabreen Glacier has shortened by 185 m since 1999. The Brenndalsbreen and the Rembesdalsskåka have shortened by 276 and 250 m respectively since 2000. In 2004 alone, the Briksdalsbreen lost 96 m - the greatest annual loss in length of this glacier since measurements began in 1900. From 1995 to 2005 the glacier front receded by 176 m.

Asia

The Himalayas and other mountain ranges in Central Asia comprise large regions that are glaciated; In the Himalayas alone, around 6,500 glaciers cover an area of ​​33,000 km². These glaciers play a key role in supplying water to arid countries such as Mongolia , the western part of China , Pakistan and Afghanistan . According to one estimate, 800,000 people are at least partially dependent on meltwater from the glaciers. Like other glaciers around the world, Asian glaciers are rapidly disappearing. The loss of these glaciers would have a huge impact on the ecosystem and the people in this region.

Himalayas

This NASA image shows the formation of numerous glacial lakes at the terminus of the retreating glaciers in Bhutan in the Himalayas

Most of the glaciers in the Himalayas have been melting since the mid-19th century, with the exception of the Karakoram and parts of the northwestern Himalayas. The mass loss has likely accelerated over the past few decades. Some areas in the Himalayas are warming five times as fast as the global average. The reasons for this are, in addition to the increase in greenhouse gas concentrations, also large amounts of soot and other particles that arise when burning fossil raw materials and biomass. These particles absorb solar radiation, which heats the air. This layer of heated air rises and accelerates the retreat of the glaciers in the mountains. A comparison of digital elevation models from 1975–2000 and 2000–2016 shows that ice loss has doubled in all regions examined. This indicates that it is not soot immissions, but climate changes in the Himalayas that are the dominant drivers of glacier melt.

In China, 53% of 612 glaciers examined melted between 1950 and 1970. After 1995, 95% were already in decline. This is an indication that glacier retreat is increasing in this region. The glacier retreat in Central Asia in the second half of the last century also showed interruptions. From the Inner Himalayas, for example, glacier tongue stagnation or small tongue protrusions are known for the period from approx. 1970 to 1980. The glaciers of China's Xinjiang area have melted by 20% since 1964. Almost half of China's glaciated area is in this area.

Without exception, all glaciers in the region around Mount Everest in the Himalayas are in decline. The Khumbu Glacier , near Mount Everest, has retreated about 3 miles since 1953. On the north side is the Rongbuk Glacier , which is losing 20 m in length every year. The approximately 30 km long Gangotri Glacier in India , which is considered to be the source of the Ganges , melted 27 m annually between 1971 and 2004. In the 69 years from 1935 to 2004, it lost an average of 22 m in length per year. Overall, it has become two kilometers shorter in the last 200 years. As the glaciers in the Himalayas melted, new glacial lakes have formed. There is a risk that these erupt ( glacier run ) and cause flooding .

Rest of Central Asia

In the northern part of the Tian Shan , the highest peak of which is 7,439 m high and which extends to the national territories of China, Kazakhstan , Kyrgyzstan and Tajikistan , the glaciers that contribute to the water supply of this arid area have almost two every year between 1955 and 2000 Cubic kilometers (km³) of ice lost. Between 1974 and 1990 the glaciers also lost an average of 1.28% of their volume each year. Glaciers in the Ak-Shirak Mountains of central Tian Shan in Kyrgyzstan lost a small part of their mass between 1943 and 1977. Between 1977 and 2001 they lost another 20% of their mass.

South of the Tian Shan Mountains is the Pamir , another high mountain range with a height of up to 7,719 m. In the Pamirs, which is mainly located in Tajikistan, there are thousands of glaciers that together cover an area of ​​about 1200 km². They are all in decline. During the 20th century the glaciers in Tajikistan lost 20 km³ of ice. The 70 km long Fedtchenko Glacier , the largest glacier in Tajikistan and also the longest non-polar glacier in the world, has already lost 1.4% of its length (0.98 km) and 2 km³ of ice during the 20th century. The neighboring Skogatch Glacier is also melting: between 1969 and 1986 it lost 8% of its total ice mass. Tajikistan and the other countries bordering the Pamirs depend on the meltwater of the glaciers, as it maintains the water level in the rivers during periods of drought and dry seasons. Due to the glacier retreat, more river water will be available in the short term, but less in the long term.

North asia

Overall, there is a decline in the glaciated area in all regions of North Asia , ranging from 10.6% in Kamchatka to 69% in the Koryak Mountains by 2018 . Also in the Orulgan chain in Verkhoyansk Mountain and barguzin range was lost than half of the glacier surface more. In the glacier areas of the Altai , Suntar-Chajata Mountains and Tscherski Mountains , which are significant in terms of area, the decline is around a quarter. There are a few exceptions in Kamchatka, where volcanic rock material partially covers glaciers and offers special insulation.

In glaciated mountains there has been a significant increase in summer temperatures; in the 1990s they began to exceed the maximum values ​​of the previous century. In the western and central part of Siberia the trends are lower than in the east. Since the first half of the 2010s, there have also been some high-pressure blocking and heat waves . In some regions, there is also a decrease in the amount of precipitation in winter; here there is a double negative effect on the glaciers: lower accumulation in winter and increased melting rates in summer. But even in the Altai and the eastern Sajan Mountains , where precipitation increased, the loss of ice in summer could not be compensated for.

As the glaciers melt, there is an increased risk of glacier run in some areas.

Middle East

In the Middle East there are a large number of glaciers in the Caucasus, plus a low double-digit number each in Iran and Turkey. The glaciers of the Greater Caucasus are predominantly small kar glaciers . There are also extensive ice fields around the highest peaks, such as Elbrus and Kazbek . The area covered by glaciers in the Caucasus fell by 11.5% between 1960 and 1986. Between 1986 and 2014 the loss accelerated, a further 19.5% of the glacier area was lost. The number of glaciers decreased from 2,349 to 2020, although the dissolution of larger glaciers had created numerous smaller ones.

In Iran , glaciers are important water reservoirs in some regions during dry seasons. In 2009 there were still around 30 small glaciers in five regions. Little is known about the development of most of the glaciers there. In the Takhte-Soleiman region in the western part of the Elburs Mountains , significant ice losses were found. In Turkey , satellite measurements, accompanied by rising minimum temperatures in summer, show more than a halving of the glaciated area, from 25 km² in the 1970s to 10.85 km² in the years 2012–2013. Five glaciers completely disappeared. Only two left, at Ararat and Uludoruk , had an area of ​​more than 3.0 km².

These glaciers in New Zealand have retreated sharply in recent years

New Zealand

The New Zealand glaciers, which covered an area of ​​1,162 km² in 2010, can be found on the South Island along the New Zealand Alps, with the exception of small glaciers on Ruapehu . Mountain glaciers have generally been in decline since 1890, which has accelerated since 1920. Between 1978 and 2014, New Zealand's glaciers lost a total of 19.3 km³ of ice volume (corresponding to 36%). The total ice volume in 2014 was about 34.3 km³. In an extreme heat wave in 2017/2018, another 3.8 km³ of ice, almost 10%, was lost. Most glaciers have become measurably thinner, have shortened, and the glaciers' nutrient area has shifted to higher altitudes in the course of the 20th century. Since the 1980s, countless small glacial lakes have formed behind the terminal moraines of many glaciers. Satellite images show that these lakes are expanding. According to an attribution study , without human-induced global warming , the extreme event in 2018 and one in 2011 would very likely not have occurred .

Some glaciers, notably the Fox and Franz Josef Glaciers , expanded periodically, especially in the 1990s. But in the overall balance of the 20th and 21st centuries, this growth is small. Both glaciers have been retreating strongly since 2009 and were over 3 km shorter by 2015 than at the beginning of the last century. These large, fast-flowing glaciers that sit on steep slopes are highly responsive to small changes. For a few years with favorable conditions, such as increased snowfall or lower temperatures, these glaciers react immediately with rapid growth. But when these favorable conditions end, they decline just as quickly. The cause of the growth of some glaciers has been linked to cooler sea temperatures in the Tasman Sea , possibly due to the increased occurrence of El Niño . This caused cooler summers in the region and more precipitation in the form of snow.

North America

The Lewis Glacier, North Cascades National Park , after melting in 1990

Glaciers in North America are mainly located in the Rocky Mountains in the United States and Canada . In addition, glaciers can be found in various mountain ranges on the Pacific coast between northern California and Alaska and a few small glaciers are scattered in the Sierra Nevada in California and Nevada (Greenland belongs geologically to North America, but is also included in the Arctic due to its location ). A total of about 276,000 km² is glaciated in North America. With the exception of a few glaciers, such as the Taku Glacier , which flow into the sea, virtually all glaciers in North America recede. The rate of melting has increased dramatically since the early 1980s, and glaciers have been disappearing faster than in the previous decade.

On the west coast of North America, the cascade chain runs from Vancouver (Canada) to northern California. Apart from Alaska, the more than 700 glaciers of the Northern Cascades (between the Canadian border and Interstate 90 in central Washington ) make up about half the glaciated area of ​​the United States. These glaciers contain as much water as all the lakes and reservoirs in Washington State combined. In addition, they supply many rivers and streams in the dry summer months with water in an amount of around 870,000 m³.

The Boulder Glacier retreated 450 m between 1987 and 2005

The Easton Glacier (located in the North Cascades) lost 255 m in length between 1990 and 2005

Until 1975, many glaciers continued to grow in the North Cascades due to cooler weather and increased precipitation between 1944 and 1976. However, all glaciers in the North Cascades have been disappearing since 1987, and the rate of decline has increased every decade since the mid-1970s . Between 1984 and 2005, glaciers lost an average of more than 12.5 meters in thickness and between 20 and 40% of their volume.

Since 1985, all 47 observed glaciers in the Northern Cascades have receded. The Spider Glacier , the Lewis Glacier (see picture), the Milk Lake Glacier and the David Glacier have even completely disappeared. The White Chuck Glacier also melted particularly heavily: its area decreased from 3.1 km² in 1958 to 0.9 km² in 2002. Similar to the Boulder Glacier on the southeast flank of Mount Baker : it was shortened by 450 m from 1978 to 2005. This decline occurred in a period with reduced winter snowfall and higher summer temperatures. The winter snow cover in the cascades has decreased by 25% since 1946 and temperatures have increased by 0.7 ° C over the same period. The snow cover has decreased, although the winter precipitation has increased slightly. Due to the higher temperatures, however, this precipitation falls more often than rain and thus the glaciers even melt in the winters. In 2005, 67% of the glaciers in the Northern Cascades were out of balance and will not survive the persistence of current conditions. These glaciers may even disappear if temperatures drop and snowfall picks up again. The remaining glaciers are expected to stabilize if the warm climate continues. However, their area will then have decreased significantly.

The glaciers of Glacier National Park in Montana are also dwindling rapidly. The extent of each glacier has been mapped for decades by the National Park Service and the US Geological Survey. By comparing photographs from the mid-19th century with current images, there is ample evidence that the national park's glaciers have receded significantly since 1850. The larger glaciers today take up about a third of the area that they occupied in 1850 when they were first examined. A large number of smaller glaciers have even completely melted. In 1993 the glaciers of the national park only took up an area of ​​almost 27 km². In 1850 it was still about 99 km². Most of the glacier ice in Glacier National Park will probably have disappeared by 2030, even if the current global warming has stopped and temperatures decrease again. The Grinnell Glacier pictured below is just one of many that have been thoroughly documented with photographs over several decades. The photographs clearly demonstrate the retreat of the glacier since 1938.

and display information about the image

The decline of the Grinnell Glacier in 1938, 1981, 1998, 2005, 2009 and 2013

Further south in the Grand Teton National Park in Wyoming there are around a dozen small glaciers despite the semi-arid climate. They all went back over the past 50 years. The Schoolroom Glacier, which lies just southwest of Grand Teton (4,197 m), the highest mountain in Grand Teton National Park, is expected to have melted by 2025. Research shows that the glaciers of the Bridger-Teton National Forest and the Shoshone National Forest of the Wind River Mountain Range (Wyoming) lost about a third of their size between 1950 and 1999. And photographs even show that the glaciers have lost about half their size since the late 1890s. The speed at which glaciers are retreating has also increased: in the 1990s, glaciers retreated faster than in any previous decade in the past 100 years. The Gannett Glacier on the northeastern slope of Gannett Peak, Wyoming's highest mountain (4,207 m), is the largest glacier in the Rocky Mountains south of Canada. Since 1929 it has lost over 50% of its volume. Half of the loss has occurred since 1980. The remaining Wyoming glaciers are likely to have melted by the middle of the century.

The Athabasca Glacier has retreated 1500 m in the last century

The glaciers of the Canadian Rockies are generally larger and more common than the glaciers of the Rockies in the United States. The Athabasca Glacier, which is quite easily accessible, is based on the 325 km² Columbia ice field . The glacier has lost 1,500 m in length since the late 19th century. Between 1950 and 1980 the glacier retreated only slowly, and since 1980 the rate of decline has increased. The Peyto Glacier in Alberta , which retreated quickly in the first half of the 20th century, now covers an area of ​​12 km². It stabilized until 1966 and has been falling since 1976. The Illecillewaet Glacier in Glacier National Park in British Columbia has retreated about 2 km since it was first photographed in 1887.

In the Yukon , a territory in the extreme northwest of Canada, strong glacier retreat can be observed. The 1,402 glaciers in Yukon covered an area of ​​11,622 km² at the end of the 1950s; in 2006-2008 it was 9,081 km². In these 50 years, the glacier area decreased by over 20%. Of the 1,402 glaciers, 1,388 receded or disappeared completely, ten remained roughly unchanged in length and four grew during this period.

Map of Glacier Bay . The red lines show the glacial extent with time given since 1760 during the glacier retreat after the Little Ice Age .

There are thousands of glaciers in Alaska, but relatively few of them are named. One of them is the Columbia Glacier near Valdez . The glacier has lost 15 km in length in the last 25 years. Icebergs calve from the glacier into Prince William Sound Bay. These icebergs were a contributing cause for the Exxon Valdez - environmental disaster . While trying to avoid an iceberg, the Exxon Valdez ran aground on Bligh Reef and 40,000 tons of crude oil leaked. Another, the Tyndall Glacier, has retreated by 15 miles since the 1960s, an average of more than 500 meters per year.

The McCarty Glacier of the Harding Icefield in 1909 and 2004. In 2004 the glacier can no longer be seen in the picture

North of Juneau , the capital of the state of Alaska, is the 3,900 km² Juneau Ice Cap . The outlet glaciers of the ice cap have been observed since 1946 as part of the Juneau Icefield Research Program. Of the ice cap's 18 glaciers, 17 are receding and one, Taku Glacier, is growing. 11 of the glaciers have receded by more than 1 km since 1948, including Antler Glacier (5.6 km), Gilkey Glacier (3.5 km), Norris Glacier (1.1 km), and Lemon- Creek Glacier (1.5 km). The Taku Glacier has been growing since 1890: between 1890 and 1948 it grew by about 5.3 km and since 1948 by about 2 km.

On the Kenai Peninsula in southern Alaska, the approximately 1,800 km² Harding Icefield is home to more than 38 glaciers. Most of the glaciers in this ice field have lost length since 1973. One of them is the McCarty Glacier . This withdrew between 1909 and 2004 by about 20 km. The glacier reached its maximum extent around 1850; about 0.5 km longer than 1909. Most of the retreat observed occurred before 1964, and in the 1970s the glacier actually expanded somewhat due to cooler climates. Between 1986 and 2002 it lost about 306 m in length. The Skilak Glacier also fell sharply: between 1973 and 2002 this glacier, which flows into a lake, retreated by around 3.8 km. In total, the ice field lost 78 km² of glaciated area between 1986 and 2002.

With the help of remote sensing technologies (laser height measurement), major thickness losses of glaciers were measured in Alaska between the mid-1950s and mid-1990s: The 67 examined glaciers lost an average of 0.52 meters in thickness per year during the measurement period. Extrapolated to all of Alaska's glaciers, there were volume losses of 52 ± 15 km³ of ice per year. 28 glaciers continued to be observed between the mid-1990s and 2001. They lost an average of 1.8 m in thickness per year. So the melting of the glaciers has accelerated. Again extrapolated to all glaciers in Alaska, this means a volume loss of 96 ± 35 km³ per year.

In 2019, acoustic observations found that the LeConte Glacier in southeastern Alaska was melting significantly faster than scientific theory predicts.

Patagonia

The San Rafael Glacier in 1990 and 2000

In Patagonia , a region of over 900,000 km² in South America, which extends over the southern Andes of Chile and Argentina , glaciers are melting at an incomparably fast worldwide. Scientists believe that if current conditions persist, some of the Andean ice caps will be gone by 2030. The Northern Patagonian Ice Field, for example, part of the Patagonian ice cap, lost approximately 93 km² of glaciated area between 1945 and 1975. Between 1975 and 1996 it lost another 174 km², which indicates an accelerating rate of melting. The San Rafael Glacier , one of the glaciers in this ice cap, has retreated by around 10 km since the end of the 19th century. In contrast, it has remained relatively stable for the last 3000–5000 years. The glaciers of the Southern Patagonian Ice Field are almost all receding: 42 glaciers faded, four remained constant and two grew between 1944 and 1986. The O'Higgins Glacier retreated most strongly between 1975 and 1996 with 14.6 km. The 30 km long Perito Moreno Glacier is one of the few glaciers that has grown. Between 1947 and 1996 it was extended by a total of 4.1 km. It is currently in a state of equilibrium, so there is no change in length.

Tropical glaciers

The tropics and the equator

Tropical glaciers are located between the northern and southern tropics . The two tropics run 2,600 km north and south of the equator . The tropical glaciers are very unusual glaciers for several reasons. On the one hand, the tropics are the warmest area on earth. In addition, the seasonal temperature fluctuations are small, with temperatures in the tropics being high all year round. As a result, there is a lack of a cold season when snow and ice could accumulate. Finally, there are few high mountains in this region that are cold enough for glaciers to form. All glaciers in the tropics are on isolated mountain peaks. In general, tropical glaciers are smaller than others and therefore react more sensitively and faster to climate changes . Even a small increase in temperature therefore has a direct effect on tropical glaciers.

Northern and Central Andes

Share of the glacier area in the tropical Andes
country				proportion of
Bolivia			21.42%
Peru			71.41%
Ecuador			3.61%
Colombia			3.49%
Venezuela			0.07%

Most of the tropical glaciers are located in South America ; measured by area, it is more than 99%. Of this, the largest areas are in the outer tropics, in Peru a good 70%, in Bolivia 20%, the rest in the inner tropics is spread across Ecuador, Colombia and Venezuela. More than 80% of the glacier ice in the northern Andes is distributed in small glaciers, each about one square kilometer in area, on the highest mountain peaks. Inertropical glaciers are more susceptible to temperature fluctuations, glaciers in the outer tropics react relatively strongly to fluctuations in precipitation. Overall, glaciologists have noted a significant glacier retreat, the glaciated area decreased from 2750 km² in the 1970s to 1920 km² as of 2013.

Inner tropics

In Venezuela, the glaciers have been lost, as here at Pico Bolivar , with the exception of a relic of 0.1 km² at Pico Humboldt

In Venezuela , of the 200 km² glacier area (in the 17th century), 0.1 km² of the Humboldt Glacier (2018) is left. It is expected that it will melt soon, and Venezuela will then be the first Andean country without glacier ice. In Colombia , 62% of the glacier area has been lost since the middle of the 20th century. In 2016 it was still 42 km², which was divided into four mountain ranges on predominantly smaller glaciers with an area of ​​less than 1 km² each: 7.2 km² in the isolated Caribbean coastal mountains of the Sierra Nevada de Santa Marta , 15.5 km² in the Sierra Nevada del Cocuy in the north-east of the country , 11.5 km² in the Los Nevados National Park and 8.0 km² on the Nevado del Huila volcano , for which there is a significant risk of lahars in the event of an eruption . Only the highest ones could still be present in the second half of this century. In Ecuador , the glacier area sank from 92 km² in 2017 to 43.5 km² in 2017, the height of the equilibrium line rose to 5120 m. The Antizana Glacier in Ecuador lost 0.6–1.4 m of ice annually between 1992 and 1998, and the rate of retreat has increased since the mid-1980s.

Outer tropics

Between 1986 and 2014 the area of ​​the Bolivian glaciers decreased by more than 40% or 228 km². According to forecasts, around 10% of the area of ​​1986 will remain by 2100. At the same time, the risk of flooding through ice reservoirs increases . The Chacaltaya Glacier in Bolivia, for example, lost 0.6–1.4 m of ice annually between 1992 and 1998. In the same period it lost 67% of its volume and 40% of its thickness, its mass has decreased by a total of 90% since 1940. In 2005 it no longer even took up an area of ​​0.01 km², in 1940 it was 0.22 km². In 2009 the glacier had completely melted.

Further south, in Peru , the Andes reach greater heights (especially in the Cordillera Blanca ) and are home to around 70% of tropical glaciers. The area of ​​Peruvian glaciers was first estimated in 1988 on the basis of data from 1970 at 2,600 km². The largest ice areas were in the Cordillera Blanca (around 1970: 723 km²) and the Cordillera de Vilcanota (around 1970: 539 km²), in other Cordilleras less than 200 km² were each glaciated. The glaciers play an important role in the water supply of the largely desert-like coastal regions. Glacier runs threaten settlements and people, especially on the Río Santa , below the Cordillera Blanca, where catastrophic glacial lake eruptions have repeatedly occurred. According to researchers from the University of Erlangen-Nürnberg , a total of 29% of the glacier area was lost between 2000 and 2016, leaving around 1,300 km² spread over around 1,800 glaciers.

In the Cordillera de Vilcanota, the slightly less than 44 sq km (as of 2018) is great Quelccaya - ice cap that by 2010 most extensive tropical ice cap. Because of its particularly high melting rate, it has lost significantly more area than the meanwhile largest, the - also melting - glacier area on the Coropuna (44.1 km²) in the Peruvian Cordillera Volcánica . Several glaciers emanate from the Quelccaya Ice Cap and they are all disappearing. The largest, the Qori Kalis Glacier, receded 155 m per year between 1995 and 1998. Between 2000 and 2002 it decreased by around 200 m per year. The melting ice has formed a large glacial lake since 1983. The entire ice cap lost almost 30% of its area between 1980 and 2010. Samples of non-fossilized plants revealed when the ice cap retreated suggest that the ice cap was last smaller than it is today more than 5200 years ago. Even if current conditions persist, the ice cap will be completely melted in about 50 years, according to US paleoclimatologist Lonnie G. Thompson.

Africa

The Furtwängler glacier on Kilimanjaro

Almost all of Africa is in the tropics and subtropics , so its glaciers are limited to two remote mountain peaks and the Ruwenzori Mountains . In total, the glaciers in Africa cover an area of ​​10.7 km². At 5,895 m, Kilimanjaro is the highest mountain in Africa. Between 1912 and 2006, the volume of glacier ice on Kilimanjaro decreased by around 82%. From 1984 to 1998 part of the glacier retreated by approx. 300 m. If this high rate of melting is maintained, the glaciers on Kilimanjaro will have disappeared between 2015 and 2020. In March 2005, a report found that there was hardly any glacier ice left on the mountain and that for the first time in 11,000 years parts of the barren mountain peak had become ice-free. A considerable decrease in the amount of precipitation on Kilimanjaro since 1880 is said to be the main reason for the retreat of the glacier. However, this explanation alone is unsatisfactory. Historical records show that there was an exceptional amount of precipitation around 1880, but before 1860 there was an amount that was normal in the 20th century. The glacier has also existed continuously for at least 11,700 years and has since weathered some particularly severe droughts, as shown by its ice cores.

The Furtwängler Glacier is located near the Kilimanjaro summit . Between 1976 and 2000 its area decreased from 113,000 m² to 60,000 m². In early 2006, scientists found a large hole near the center of the glacier. This hole, which extends through the 6 m thick glacier down to the bedrock, will presumably grow further and divide the glacier into two parts in 2007.

Mount Kenya lies north of Kilimanjaro . At 5,199 m, this is the second highest mountain in Africa. On the mountain there are some small glaciers that have passed through six growth phases in the last 6000 years (the last two in the years 650–850 and 1350–1550). Glaciers have lost at least 45% of their mass since the middle of the 20th century. According to studies by the US Geological Survey (USGS), there were 18 glaciers on Mount Kenya in 1900. In 1986 there were 11 left. The total area covered by glaciers has decreased from approx. 1.6 km² in 1899 to 0.4 km² (1993).

To the west of Kilimanjaro and Mount Kenya, the Ruwenzori Mountains rise up to 5,109 m. Photographs show a significant decline in the areas covered with ice in the last century. Around 1900 there was still a glacier area of ​​6.5 km² on the mountain. By 1987 this had melted to about 2 km² and in 2003 to about 0.96 km². In future, however, the glaciers of the Ruwenzori Mountains could recede more slowly than the glaciers of Kilimanjaro and Mount Kenya due to the high humidity of the Congo region. Nevertheless, a complete melting of the glaciers is expected within the next two decades.

New Guinea

Ice cap on Puncak Jaya 1936

Glacier on Puncak Jaya 1972. From left to right: the Northwall Firn, the Meren Glacier and the Carstensz Glacier; USGS. Mid 2005 and animation

There is also photographic evidence of massive glacial retreat since the island was first explored by plane in the 1930s on the second largest island in the world, New Guinea , located north of Australia , at 771,900 km² . Due to the island's location in the tropics, temperatures hardly fluctuate during the year. The amount of rain and snow is also stable, as is the cloud cover. There was no noticeable change in rainfall during the 20th century . Nevertheless, the 7 km² largest glacier cover on Puncak Jaya , the highest mountain on the island at 4,884 m, has shrunk: the ice cover, which closed in 1936, has been divided into several smaller glaciers. The Meren and Carstens glaciers retreated from these glaciers by 200 m and 50 m respectively between 1973 and 1976. The Northwall Firm, another large remnant of the ice cap on Puncak Jaya, has also split into several glaciers since 1936. The extent of glacier retreat in New Guinea was made clear in 2004 by images from the IKONOS satellite . Between 2000 and 2002 the East Northwall Firm lost 4.5%, the West Northwall Firm 19.4% and the Carstensz Glacier 6.8% of their mass. The Meren Glacier even completely disappeared sometime between 1994 and 2000. On the summit of Puncak Trikora , the second highest mountain in New Guinea at 4,750 m, there was also a small ice sheet that disappeared completely between 1939 and 1962.

Polar regions

The location of the polar regions

Despite their importance for humans, the mountain and valley glaciers of medium latitude and the tropics contain only a small proportion of the glacier ice on earth. About 99% of all freshwater ice is in the large polar and sub-polar ice sheets of Antarctica and Greenland . These continental ice sheets, which are 3 km or more thick, cover much of the polar and sub-polar land masses. Like rivers from a huge lake, numerous glaciers flow from the edge of the ice sheets into the ocean, transporting huge amounts of ice.

The observation and measurement of ice sheets has improved significantly in recent years. In 1992 it was still believed that the annual mass balance of the Antarctic, for example, was in a range of −600 gigatons (Gt) to +500 Gt. Today the estimates are much more precise. The ice sheets of Greenland and Antarctica are currently losing around 125 Gt of mass each year. The loss of Greenland contributes 100 Gt and that of West Antarctica 50 Gt. East Antarctica is gaining about 25 Gt in mass. The improved observations can therefore capture the current situation quite precisely. Nowadays science is particularly troubled by the dynamics in ice sheets and glaciers that are not understood. These make it very difficult to reliably model changes in the future.

Antarctic

The Larsen B ice shelf breaks. The picture shows the US state of Rhode Island with its area of ​​4,005 km² for comparison.

In the Antarctic , the mean temperature has increased by an estimated 0.2 ° C since the 19th century. The first complete gravity analysis over the entire Antarctic ice sheet showed that in the observation period between April 2002 and August 2005 the average annual loss of ice mass was 152 (± 80) km³. There is considerable variability in precipitation, but no clear trend. If the entire continent is considered, there has been no permanent and significant change in snowfall at least since the 1950s. Between 1985 and 1994 the amount of precipitation increased, particularly in the interior of the Antarctic, while it had decreased in some areas in the coastal areas. This trend was then practically exactly reversed, so that between 1995 and 2004, apart from three exposed regions, less snow fell almost everywhere, in places up to 25%.

The loss of ice in the Antarctic became particularly dramatic when large parts of the Larsen Ice Shelf dissolved . If you look closely, the Larsen Ice Shelf consists of three individual shelves that cover different areas on the coast. These are called Larsen A, Larsen B and Larsen C (from north to south). Larsen A is the smallest and Larsen C is the largest of the shelves. Larsen A disbanded in January 1995, Larsen C is apparently stable at the moment. The dissolution of the Larsen B Shelf was determined between January 31 and March 7, 2002, when it finally broke off with an ice sheet of 3,250 square kilometers. Up until then, Larsen B was stable for over 10,000 years throughout the Holocene . In contrast, the Larsen A Shelf had only existed for 4000 years.

The Pine Island Glacier in western Antarctica, which flows into the Amundsen Sea , thinned 3.5 ± 0.9 m per year from 1992 to 1996 and has retreated about 5 km over the same period. The loss in volume of the glacier has quadrupled in the last ten years: from −2.6 ± 0.3 km³ per year (1995) to −10.1 ± 0.3 km³ per year in 2006. The neighboring Thwaites Glacier, too loses mass and length. A decline can also be observed on the Dakshin-Gangotri Glacier: Between 1983 and 2002 it retreated an average of 0.7 m per year. On the Antarctic Peninsula , the only part of Antarctica that protrudes beyond the Arctic Circle, there are hundreds of receding glaciers. A study examined 244 glaciers on the peninsula. 212 or 87% of the glaciers receded, averaging a total of 600 m from 1953 to 2003. The Sjogren Glacier has retreated the most with about 13 km since 1953. 32 of the examined glaciers grew. The average growth was 300 m per glacier, which is significantly less than the massive decline observed.

Iceland

The 8,100 km² Vatnajökull Ice Cap is located in Iceland . Breiðamerkurjökull glacier, one of the glaciers in the Vatnajökull ice cap, shortened by 2 km between 1973 and 2004. At the beginning of the 20th century the glacier extended up to 250 m into the ocean. By 2004, the end of the glacier had retreated three kilometers inland. This is a fast-growing has lagoon formed in which icebergs , are the break off from the glacier ( "calve"). The lagoon is about 110 m deep and almost doubled its size between 1994 and 2004. Since 2000, all but one of the 40 glaciers in the Vatnajökull Ice Cap have gone back. In Iceland, of the 34 glaciers examined, the majority receded between 1995 and 2000 (28), four were stable and two were growing. On August 18, 2019, Iceland officially said goodbye to Okjökull .

Canadian Arctic Archipelago

There are a number of sizeable ice caps in the Canadian Arctic archipelago . These include the Penny and Barneseis caps on Baffin Island ( the fifth largest island in the world with 507,451 km² ), the Bylotei Cap on Bylot Island (11,067 km²) and the Devonian Cap on Devon Island (55,247 km²). These ice caps are thinning and slowly retreating. Between 1995 and 2000, the Penny and Barneseis caps thinned each year by more than 1 m at lower altitudes (below 1,600 m). Overall, the ice caps of the Canadian Arctic lost 25 km³ of ice annually between 1995 and 2000. Between 1960 and 1999 the Devonian Ice Cap lost 67 ± 12 km³ of ice, mainly through dilution. The main glaciers that extend from the edge of the eastern Devonian Cap have retreated 1–3 km since 1960. The Simmon Ice Cap on the Hazen Highlands on Ellesmere Island has lost 47% of its area since 1959. If the current conditions persist, the remaining glacial ice on the Hazen Highlands will have disappeared by 2050.

Spitsbergen

North of Norway, the island is Spitsbergen of Svalbard - archipelago between the North Atlantic and the Arctic Ocean , which is covered by many glaciers. The Hansbreen Glacier on Spitzbergen z. B. withdrew 1.4 km between 1936 and 1982. It lost another 400 m in length between 1982 and 1998. The Blomstrandbreen has also been shortened: in the past 80 years, the length of the glacier has decreased by around 2 km. Since 1960 it has retreated an average of 35 m per year, with the speed increasing since 1995. The Midre Lovenbreen Glacier lost 200 m in length between 1997 and 1995.

Greenland

Satellite image of Jakobshavn Isbræ . The lines mark the progressive retreat of the calving front of the west Greenland glacier from 1850 to 2006. The aerial photo is from 2001, so that the calving front is on the corresponding timeline.

Both the air temperatures close to the ground in Greenland and the sea ​​temperatures around the largest island in the world, which is home to 97% of the Arctic land ice, are rising rapidly. Between the beginning of the 1990s and the 2010s, the summer air temperatures that are particularly important for the mass balance on the surface of the Greenland ice sheet increased by around 2 ° C. Most of Greenland's glaciers end in the sea. Overall, the rise in sea temperatures leads to a faster melting of the submarine glacier ice and can in phases trigger significantly higher ice losses through calving . Between 2003 and 2012, Greenland lost around 274 ± 24 Gt of ice annually. Both processes - loss of mass on the surface of the ice sheet and loss of ice in the sea - contributed to about the same extent.

In a comparison of measurements from 2002 to 2004, glacier retreat has doubled between 2004 and 2006, i.e. in just two years. According to various measurements, the mass loss in Greenland is between 239 ± 23 km³ and 440 km³ per year. It has increased sixfold since the 1980s. This loss became particularly evident in 2005 when a new island called Uunartoq Qeqertoq ( Warming Island ) was discovered on the east coast of Greenland . After a large amount of mainland ice melted, it was found that Uunartoq Qeqertoq was not a peninsula connected to the mainland, as previously believed.

A surprising dynamic can be seen on individual glaciers in Greenland . Two of the largest glaciers on the island, the Kangerlussuaq and the Helheim , which together contributed 35% to the mass loss of East Greenland in recent years, have been studied in more detail by a team led by glaciologist Ian Howat. It turned out that the melting rate of the two glaciers had doubled between 2004 and 2005. By 2006, the mass loss had dropped back to the value of 2004. Such behavior was previously unknown for glaciers, and it illustrates the uncertainty at what speed the Greenland ice sheet will continue to thaw over the next few decades.

consequences

Among the consequences of global glacier retreat, those two core problems are described in more detail which intervene most sensitively in the natural ecosystem and which are likely to have a decisive influence on the living conditions of a still unpredictable proportion of the world's population in the future: the rise in sea levels and water shortages. Effects of other kinds, such as those on glacier tourism, are of secondary importance.

Further information can be found in the articles

• Consequences of global warming in Germany ,
• Consequences of global warming in Europe ,
• Consequences of global warming in the Arctic and
• Consequences of global warming in Antarctica .

Rise of the sea level

→ Main article : Sea level rise since 1850

Between 1993 and 2003 the sea level rose by 3.1 mm per year, with an error limit of ± 0.7 mm. In its fourth assessment report published in 2007, the intergovernmental committee on climate change ( IPCC) estimates that the Greenland ice sheet contributed 0.21 (± 0.07) mm and the Antarctic with 0.21 (± 0.35) mm to the sea level rise observed so far. Melting glaciers have a significant share of 0.77 (± 0.22) mm. According to various IPCC scenarios, sea level rises between 0.19 m and 0.58 m are possible by 2100, a value that is explicitly based on the difficult-to-model ice sheets of Greenland and Antarctica without the possibly increasing contribution.

Between 1993 and 2014, the sea level rose 3.2 mm per year. This is 50% more than the average for the 20th century.

A complete melting of the Greenland ice sheet, considered unlikely in the course of the 21st century, would raise sea levels by around 7.3 m. The 25.4 million km³ of ice in the whole of Antarctica could lead to an increase of approx. 57 m in the event of a melting; According to climate models, however, the ice mass of the Antarctic will increase rather than decrease in the course of the 21st century and thus reduce the rise in sea level. With a volume of 80,000 km³, the almost 160,000 glaciers worldwide contain about as much water as the 70 ice caps (100,000 km³) and could thus raise the sea level by 24 cm (ice caps: 27 cm).

Even without the ice sheets disappearing, the consequences for the people affected are dramatic. Countries most at risk from sea level rise include Bangladesh , Egypt , Pakistan , Indonesia and Thailand , all of which currently have large and relatively poor populations. So live z. For example, in Egypt around 16% of the population (approx. 12 million people) in an area that would be flooded if the sea level rises by 50 cm, and in Bangladesh over ten million people live no higher than 1 m above sea level. If the sea level rises by 1 m, not only they, but a total of 70 million people in Bangladesh would have to be resettled if there was no investment in coastal protection by the end of the century. In addition, the loss of land and the increase in the salt content in the soil would cut the rice harvest in half, with serious consequences for food security.

Without countermeasures, a rise in sea level of 1 m would permanently flood 150,000 km² of land area worldwide, 62,000 km² of which are coastal wetlands. 180 million people would be affected, and $ 1.1 trillion in damage to destroyed property based on today's figures. Below an increase of 35 cm, this can be managed with appropriate coastal protection measures, as can the already recorded increase of 30 cm since 1860, provided that the countries concerned invest the necessary amount in their infrastructure. According to calculations, effective coastal protection will cost less than 0.1% of GDP in more than 180 of the 192 countries affected worldwide by 2085 , assuming strong economic growth and only moderate population growth in the underlying scenarios.

Runoff of meltwater

In some regions the meltwater of the glaciers is temporarily the main source of drinking water during the year , which is why a local disappearance of glaciers can have serious consequences for the population, agriculture and water-intensive industries. This will particularly affect Asian cities in the Himalayan catchment area and South American settlements.

As the glacier retreats, the amount of water carried by the rivers increases for a short time. The additional amount of water released from the Himalayan glaciers, for example, has led to an increase in agricultural productivity in northern India. In the longer term - the northern hemisphere glaciers are expected to lose an average of 60% in volume by 2050 - the decline in the amount of water available is likely to have serious consequences (e.g. for agriculture). As a further consequence, there may be an increasing risk of flooding on the banks of the rivers. In the Himalayas, for example, the masses of snow accumulate on the glaciers increasingly in summer during the monsoons . If the glaciers retreat, the precipitation in higher and higher altitudes of the Himalayas will briefly flow off as rainwater or to melt snow , instead of remaining on site for longer periods of time as ice.

The Ecuadorian capital Quito, for example, gets some of its drinking water from a rapidly shrinking glacier on the Antizana volcano . La Paz in Bolivia , like many smaller settlements, is dependent on the glacier water. Much of the agricultural water supply in the dry season is ensured by meltwater. Another consequence is the lack of water in the rivers that power the continent's numerous hydroelectric plants . The speed of change has already prompted the World Bank to consider adaptation measures for South America.

In Asia, water scarcity is not an unknown phenomenon. As worldwide, a considerable increase in water consumption is also expected on the Asian continent. In the future, this increasing demand will meet with less and less available water from the glaciers of the Himalayas. In India, the agriculture of the entire northern part depends on the fate of the mountain glaciers. India and Nepal's hydropower plants are also threatened, Chinese wetlands could disappear and the groundwater level will drop.

Eruptions from glacial lakes

When the glaciers melt, rocks and debris break off incessantly in areas with high relief energy such as the Himalayas or the Alps. This rubble collects as a moraine at the end of the glacier and forms a natural wall. The wall prevents the meltwater from flowing away, so that behind it a continuously larger and deeper glacial lake is created. If the water pressure becomes too high, the wall can suddenly break, releasing large amounts of water and causing catastrophic flooding ( glacier run ). The phenomenon of glacial lake eruptions is not new, but glacier retreat increases the likelihood of their occurrence in many mountain regions. In Nepal, Bhutan and Tibet, the number of glacial lake eruptions has already increased from 0.38 per year in the 1950s to 0.54 / year in the 1990s.

According to topographic maps, aerial photographs and satellite images, there are 2323 glacial lakes in Nepal. In Bhutan a total of 2674 were counted in 2002. Of these, 24 (in Nepal 20) were classified as potentially dangerous for humans, including the Raphstreng Tsho. In 1986 it was measured 1.6 km long, 0.96 km wide and 80 m deep. By 1995 the glacial lake grew to a length of 1.94 km, a width of 1.13 km and a depth of 107 m. A nearby glacial lake is the Luggye Tsho; when it broke through in 1994, 23 people lost their lives. In Nepal, the Dig Thso broke through on August 4, 1985 and caused a tidal wave up to 15 m high that claimed five lives, destroyed 14 bridges, a small hydroelectric power station and many residential buildings. Between 1985 and 1995 another 15 larger glacial lakes broke through their walls in Nepal.

Countermeasures

Part of the Tiefenbachferner in the Ötztal Alps covered with foil

The extent and significance of the increased glacier retreat in connection with the observable and in some cases still to be expected drastic consequences make clear the need to counteract it with measures of resource conservation, increasing water efficiency and especially with effective climate protection . Possibilities for better use of the available water can be found in methods of sustainable agriculture, while climate protection must focus on saving greenhouse gases, as they were first stipulated in international law in the Kyoto Protocol .

At the local level, possibilities have recently been tried out in Switzerland to give glacier ski tourism a perspective by covering large areas of the glacier between May and September with a special fleece to protect against solar radiation and heat supply. Based on the limited purposes, the first attempts on the Gurschen Glacier have been successful. For the phenomenon of global glacier retreat, however, such an approach is also irrelevant from the point of view of the glaciologist Andreas Bauder, who is involved in the activities on the Gurschen Glacier.

literature

• Intergovernmental Panel on Climate Change: Fourth Assessment Report - Working Group I, Chapter 4: Observations: Changes in Snow, Ice and Frozen Ground. 2007, pp. 356–360, ipcc.ch (PDF; 4.9 MB)
• Peter Knight: Glacier Science and Environmental Change. Blackwell Publishing, 2006, ISBN 978-1-4051-0018-2 (English).
• Wolfgang Zängl, Sylvia Hamberger: Glaciers in the greenhouse. A photographic journey through time to the Alpine Ice Age. Tecklenborg-Verlag, 2004, ISBN 3-934427-41-3 .

Movie

• Chasing ice

See also

• Melting of the polar ice caps

Web links

Commons : Glacier Shrinkage  - Collection of images, videos and audio files

• Website of the World Glacier Monitoring Service (English)
• Gletscherarchiv.de - Documentation of changes in alpine glaciers
• Eidgenössische Technische Hochschule (ETH) Zurich: Laboratory of Hydraulics, Hydrology and Glaciology - Research , collection of studies on the retreat of glaciers and glacier physics (English)
• Article at Telepolis : When the glaciers dance - As a result of global warming, the glacier quakes in Greenland increase in summer and fewer glaciers, more floods and droughts
• Articles in English at RealClimate.org: Worldwide glacier retreat , Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century , Tropical Glacier Retreat and Glacier Mass Balance: equilibrium or disequilibrium response?
• Reports from non-governmental organizations: Greenpeace Germany (2006): Alarm for the glaciers (PDF, 2.0 MB) (PDF) WWF: Going, Going, Gone. Climate Change & Global Glacier Decline (PDF, 0.3 MB) (PDF)
• Glaciers online: Dwindling glaciers
• Interactive glacier comparisons from the Swiss Alps
• Alpendämmerung - Europe without glaciers Reportage & Documentation - ARD

Individual evidence

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119. ↑ Byrd Polar Research Center: Peru - Quelccaya (1974-1983). The Ohio State University, February 10, 2006, online
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This article was added to the list of excellent articles on July 26, 2007 in this version .