February 20, 2012

Penny Ice Cap southwestern margin retreat

Posted by Mauri Pelto

Examination of 1991 and 2009 Landsat imagery highlights the retreat of the Penny Ice Cap at its southwestern margin. The glaciers and lakes in this region are unnamed. The Penny Ice Cap is one of two large ice caps on Baffin Island and is the southernmost of the two, with an area of more than 5600 square kilometers. On the east side the glacier exit the ice cap through spectacular mountains. The westside spreads across rolling upland terrain. In this post we examine the margin at the southwest corner, where the ice cap ends in a series of upland lakes. Changes in the margin are identifed from Landsat images from 1991-top, 2003-middle and 2009-bottom. The snowline in this region is near 900 meters in the 1991 and 2003 images. In the 2009 image the snowline is at least 1100 meters leaving the southwest corner of the Penny Ice Cap with a minimal accumulation zone. Zdanowizc et al (2012) note that in recent years the ice cap has experienced heightened melt and that little retained snowpack survives the summer, that most of the retained accumulation is refrozen meltwater (superimposed ice). In each image key locations are indicated: the nunataks are marked with violet arrows as is the margin downstream of the nunataks, key islands and peninsulas are noted with green arrows that are at the 1991 margin, the orange arrow indicates a region just east of a key marker lake. Landsat imagery from 2003 and 2009 indicates the same locations. It is evident that new islands, lakes and peninsulas are developing. The retreat and formation of new lakes at the orange and violet marginal arrow are apparent the appearance of new islands in the lakes at the green arrows is also evident. One of the largest marginal changes is downstream of the nunataks. In 1991 the margin here had no notable indent from the rest of the margin and the glacier surface was not notably debris covered. In 2009 the margin has developed a new lake as an indent has formed and the glacier surface has more evident debris. This debris is too thin to insulate the ice underneath and instead will reduce the albedo and enhance melting. The nunatak is also expanding particularly toward the margin. Overlaying the 1991 and 2009 images in Google earth provides comparison of the margin of 1991 to the Google Earth imagery and 2009 imagery. The retreat along this section of the ice cap is 300-400 meters during this 18 year period. The driving force has been an increase in temperature and this has caused mass losses on ice caps throughout the Canadian Arctic (Gardner, et al. 2011) and (Sharp et al, 2011). The mass losses of the Penny Ice Cap are also affecting the eastern margin around Coronation Glacier.