Greenland glacier: Mittivakkat Gletscher

Going just slightly nearer to us, today's post will be about one of Greenland's glaciers: Mittivakkat Gletscher (MG). It's a well-observed and studied Greenland glacier on the South-east part of Greenland. Like most of the observed glaciers, this glacier is retreating as well. The most significant part of the study of this study is that it is indicative of glacier changes in the broader region. Most of the glaciers that we study like that in the Antarctic Peninsular cannot be used to represent the entire region due to local variability in climate and environment. Thus, the study of MG is especially important due to it's regional representation. In this paper (look at the end of the post for the title), they study the reasons for the retreat and also the surface mass balance of the glacier). 

First of all, summer temperatures in Greenlands's coastal areas have 'increased by an estimated 1.7 degree Celsius on average' (Camiso, 2006). More recently,surface melt extent and glacier area loss hit a record high in 2010 due to a relatively dry winter (less snow cover in winter = more exposure of glacier ice in summer) and an exceptionally warm summer. Of course, as in most cases, Greenland's warm temperature anomalies vary locally. The west of Greenland is experiencing a much higher melt rate as observed since 1990 than the rest of Greenland. Overall, the Greenland Ice Sheet is losing mass at more than 200 Gt per year for the pas several years (Allison et al., 2009). 

A. Cumulative net mass balance. Gray zone indicating 15% error and accumulation area ratio for MG from 1995 to 2010. B. Observed winter precipitation and mean summer air temperature from Tasiilaq and Nunatak. 

The surface mass balance of the glacier is measure by taking measurements of the trends in ice/snow extent and ice volume to calculate the equilibrium line altitude (ELA), which is a spatially average elevation of the equilibrium line where a set of points on the glacier surface is marked where the net mass balance is zero. In the figure above, A shows that for 13 years out of 15 years, the glacier mass balance has been negative. This is important in its measurement since the glacier mass loss is not just simply losing volume through melting or sublimation. Loss of mass leads to instability where the degree varies with the location of the loss of mass. B shows that with increasing temperatures, winter precipitation decreases as well. 

The coloured lines show the progression of the Mittivakkat Gletscher retreat in certain years from 1900 to 2010.

The above figure shows that the Mittivakkat Gletscher has been in retreat since 1900 (maximum glacier extension during the Little Ice Age). In all, it has retreated by about 1600m since 1900 and 1300m since 1931. Recent average retreat rates are about 6m per year. From 2009 to 2010, it lost about 2% (2.16m average surface mass loss) of the total glacier volume, significantly above the range of the 15-year average loss of about 0.87m. 

This graph shows the correlation of the Tasiilaq MAAT anomaly and the other stations' anomalies. Most of the correlations are above 0.5 suggesting that we can safely use observations for once glacier to represent all the others.

As mentioned above, studies have found that the mean annual air temperature (MAAT) anomalies found at MG are significantly corelated to that at Tasiilaq (r2 = 0.61 - 0.91) and at the Summit (r2 = 0.42) (The figure above shows the high correlation of the stations in Southeast Greenland with each other) This makes the study of the MG even more important and also conclusive since it also proves that higher temperatures are causing the instability of the ice sheet (the glacier will likely lose at least 70% of its current area and 80% of its volume even without further climate changes (Mernild et al., 2011)). 

In conclusion, the general trend for MG since 1995 is that summer temperatures are higher and winter precipitation has been decreasing (recovery rate of glacier mass is slower) leading to a more negative glacier mass balance as melting increases. These factors have led to the retreat of MG. With high correlations of the MG with other local glaciers, this observation is representative of the region. Thus we should also expect to see the same thing throughout Greenland. This bodes ill for the world since this study shows that even without further climate change, we are unable to stop the melting of Greenland's glaciers. 

What then shall we do? It seems hopeless to prevent glaciers from melting so should we go on business as usual? Or pump in even more money to try to save the world from warming (if it is even possible)? The Durban climate change talks shows us that the world leaders are trying to do the latter. If so, the promises of the governments to lower carbon emissions and help climate change vulnerable countries must be kept. But if it is at the expense of the country's economic growth, what then should governments do? 

References:
Mernild, S.H. et al. (2011) 'Increasing mass loss from Greenland's Mittivakkat Gletscher', The Cryosphere, 5, 341-348.

Comiso, J. (2006) 'Arctic warming signals from satellite observations', Weather, 61, 70-76.