Glaciers Shrinking

Translated from Danish to English with Google Translate

Glaciers shrinking 

16. September 2010, at. 13:22

Observations from this year's field season in Greenland show that the record hot summer has meant a very large glacier melting, where glacier fronts now retiring at an unprecedented pace.

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By Sebastian H. Mernild, Niels Batch Knudsen, Bjarne Holm Jakobsen and Bent Hasholt

The year 2010 finds the previous heat records from both 2003 and 2007 in East Greenland.

Temperature Observations show that the temperature average for the summer June, July and August ranged from 0.5 to 1.5 ° C above average over the past five decades.

Specifically, for Tasiilaq Ammassalik island, the mean summer temperature for 2010 7.8 ° C, which is 2.0 ° C above average for the period 1960-2010 of 5.8 ° C (see figure).

The average summer temperature (average for the month of June, July and August) measured in Tasiilaq Ammassalik Island, East Greenland. A rising mean summer temperature The same is true at other meteorological stations in eastern Greenland, such as in Ittoqqortoormiit (Scoresbysund), Denmark Port and Station Nord.Data Source: DMI. Click for large table.

This is the hottest summer measured in East Greenland, since systematic temperature measurements began.

The high temperatures in East Greenland is consistent with the global situation, where the first six months of 2010 according to the American space agency NASA were the warmest half in temperature measurements story.

The high summer temperatures in 2010, which is an extension of an average increase in annual mean temperatures over the past five decades at 0.8 ° C, leaving its mark on the landscape.

Summer temperatures are critical to the melting of ice and snow and the runoff of freshwater to the ocean.

In 'normal' year (ie year with summer temperatures around the mean 5.8 ° C and a winter snenedbør at 1100-1400 mm) is large drifts in the landscape well into August. In 2010, virtually all of the snow already melted away in late June / early July as a consequence of the warm early summer.

Glaciers are melting back

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From photographs taken in 1933 in connection with Knud Rasmussen's 7 Thule Expedition can gletscherrandens shape and position of approximately 75 years ago determined.

In the summer of 2010 is Mittivakkat-glacier's edge approximately 1.3 km further up the valley. Glacier front is the last of some 75 years on average molten 17-18 meters a year.

Measurements in late summer 2010 shows that the glacier front this year is melted about 35 meters back. Evidence suggests that several glaciers in the area in recent years retiring at an unprecedented pace.

A pace in 2010 is about twice the average return smelting that has happened over the nearly 75 years, where sightings and photo documentation has been made.

Measurements and modeling show that the melting back in 2010, clearly exceeding all previous 75 years.

Furthermore, Mittivakkat glacier in 63 out of the past 75 years had a clear negative mass balance, which means that summer melting of snow and ice from the glacier's surface exceeds the amount of snow that accumulates on the glacier through the preceding winter period.

In peripheral zone was the melting of glacier surface in 2010 at between 4.5 to 5.2 meters, whereas in previous years has been observed an average meltdown in the marginal zone of between 2-3 meters. Again in 2010 a doubling of the previous year's melting.

Glacier Collapse

STEP 1 An example of the various stages of 'glacier collapse' by Mittivakkat glacier in East Greenland. Glacier surface in the periphery has collapsed because of rekordafsmeltningen in the summer of 2010, both at the glacier's surface and inside the glacier, where increased amounts of meltwater erodes it. Drain Ring canals extended, which in places leads to the glacier is unable to carry its own weight. (Photo: Sebastian H. Mernild)

The hot summer has further led to the first time in about 40 years, where the glacier has been observed annually, seen what is called 'glacier collapse. "

This means that the glacier surface in the periphery not only melts back but coincide over larger areas.

There is no doubt that several glaciers in the area is heavily influenced by the high temperatures and the warmer atmosphere directly affect overfladeafsmeltningen but also by indirect heat effect due to their greatly increased volumes of meltwater creates melting inside the glacier.

Step 2 (Photo: Sebastian H. Mernild)

In contact with the relatively warmer and strongly flowing melt, there is a extension of drainage canals. In parts of the glacier's boundary area is undermining so fast that the glacier edge fails to melt back before any collapse.

Runoff

Melting of the glacier surface at a nunatak near the glacier equilibrium line where the glacier margins were marked on the rocks through the period 1994 to 2010. (Photo: Sebastian H. Mernild)

The steep glacier melting in 2010 has resulted in increased runoff of freshwater to the ocean.

It is expected that the runoff in 2010 is around 25-35 percent greater compared with the average for the past 15 years, from which there is reliable data.

The exact figures will only be available after the main melt season stops toward the end of September.

The trends observed in runoff from East Greenland, also seems to assert itself in West Greenland, for example. at Kangerlussuaq, where in recent years has been carried out similar measurements.

Summer 2010, with the high temperatures in Greenland sit clear traces of an extraordinary large glacier melting and a freshwater to the oceans, which will give added impetus to the accelerating global sea level rise.

The article produced in collaboration with the Current Science.

Reference and Links

Download the article as a pdf file in the Current Science.  Sebastian H. Mernild, climate and polar research (PhD) is employed by the Climate, Ice Sheet, Ocean and Sea Ice Modeling Group, Department of Computational Physics and Methods, Los Alamos National Laboratory, New Mexico, USA. Tel.: +1 (505) 665-2838 Skype phone: +45 36 99 27 03 email: mernild@lanl.gov  Batch Niels Knudsen is Associate Professor at the Department of Geology, University of Aarhus E-mail: ntk@geo.au.dk  Bjarne H. Jakobsen, associate professor at the Institute of Geography and Geology, University of Copenhagen. email: bhj@geo.ku.dk  Bent Hasholt is Associate Professor at the Department of Geography and Geology, University of Copenhagen. email: bh@geo.ku.dk Also read on Videnskab.dk:  Calving glaciers trigger earthquakes  Mathematician predicts Rhone glacier death  Greenland's glaciers are melting rapidly in the sea  Greenland whales sing new songs every year  Greenland caribou brands global warming

Read more about this subject  Mernild, SH, et al The 2006th Snow distribution and melt modeling for Mittivakkat Glacier, Ammassalik Island, SE Greenland, Journal of Hydrometeorolgy 7: 808-824.  Mernild, SH and GE Liston the 2010th The Influence of air temperature inversion on snow melt and glacier surface mass-balance simulation, SW Ammassalik Island, SE Greenland. Journal of Applied Meteorology and Climate, vol 49 (1): 47-67.  Mernild, SH Others The 2008th Climatic forhold ved Mittivakkat Glacier catchment (1994-2006), Ammassalik Island, SE Greenland, och i en 109 år term perspective (1898-2006). Danish Journal of Geography, 108 (1): 51-72.  Knudsen, NT and B. Hasholt the 2008th Mass balance observation that Mittivakkat Glacier, Ammasalik Island, Southeast Greenland 1995-2006, Danish Journal of Geography, 108 (1): 111-120.