February 3, 2012
Severnaya Zemlya is a Russian Island group at the transition from the Kara Sea to the Laptev Sea. This island group is 50 % ice covered, with 18,000 square kilometers of glacier cover. Severnaya Zemlya has been the focus of a detailed remote sensing based study of glacier change by Sharov et al (2010) They observed a mean change in Severnaya glacier thickness of -7.8 m since the 1980’s. The annual rate of ice loss is 4.8 km³/a, a strongly negative net balance. They found that most ice caps have steepened since 1980, Albanov and Dezhnev have both gotten thicker in the center while retreating at the margin. Imagery from this region is scant. The glacier in this region have both small snow accumulation and small melting. Overall most of the ice caps are composed of superimposed ice, that is snow that melted and then refroze before exiting the ice cap. Several ice cores have been drilled through the ice sheets identifying the rate of accumulation through time Klementyev et al (1991) and Kotlyakov et al (2004) the last 8000 years on Vavilov Ice Cap.
First on the Dezhnev Ice Cap thickening of up to 13 m was noted at the top of the ice cap by Sharov et al (2010). In this post we examine a 2000 (top) and a 2010 (middle) Landsat image that shows all of the Dezhnev Ice Cap with the Albanov Ice Cap being half obscured by clouds in the 2000 image. In the Landsat comparison pay particular attention to the region just beneath Points A-C. At Point A we see an expansion of the small proglacial lake. At Point B and C we see exposure of new bare ground as areas of thin ice near the periphery of the ice cap have been lost. In 2010 there is no snow remaining on Dezhnev, however, this by itself does not indicate there was no accumulation that year, as superimposed formation cannot be distinguished from areas of bare ice that experienced ablation in the image. For Albanov Ice Cap there is a modest retreat from the locations noted with arrows that are linear-low spots often sometimes filled with meltwater. In the bottom image a closeup of Dezhneve, an arrow indicates a low spot in the midst of the ice cap that will be prone to melt out. In this image a melt pond has developed there.