March 1, 2012

Snowshoe Peak Glacier Retreat, Yukon

Posted by Mauri Pelto

There was the Yukon Gold Rush and then there are a number of surging glaciers in the Yukon. These two have drawn our attention. In Kluane National Park, besides the large surging outlet glaciers draining the St. Elias Mountains (Donjek, Lowell, Kaskawulsh etc.) there are numerous smaller alpine glaciers in ranges just east of the St. Elias. In a recent ice core study in the Eclipse Icefield it was found that the Gold Rush led to higher fire activity (Yalcin et al., 2004). This post examines several of these glaciers that have not been the focus of any detailed study, in the are of Airdrop Lake and Snowshoe Peak. Each of the glaciers is 1.5 to 2.0 kilometers long, beginning near 2100 meters the summit area of Snow Peak and terminating between 1800 and 1900 m. This is relatively small elevation change for alpine glaciers. In the 2003 Google Earth Imagery the lack of snowcover is evident. The blue line is the terminus position from the map of 1970’s and the brown line a 1998 satellite image. There are a few outrops of rock in the midst of the glacier that formerly terminated at Airdrop Lake. Comparison of a 1987 (top), 2003 (middle) and a 2010 (bottom) Landsat image indicate that the two key outcrops that were in the midst of the glacier in 1990 are at the terminus in 2010. Two others have expanded and with terminus retreat are markedly closer to the margin of the glacier in just seven years from 2003-2010. The lower section of each glacier is quite thin and uncrevassed. The lack of snowcover during many recent years indicate a mass balance loss and glacier thinning that is driving the retreat. It does not appear the glacier that flows toward Airdrop Lake can survive, with thinning high on the glacier and limited retained snowcover. There are some patches of stagnant ice near the terminus of the Airdrop Lake Glacier, this glacier has retreated 250-450 meters from the map to 2003, 20-30% of the glacier length and is still retreating quickly as the 2010 imagery indicates. The Snowshoe Peak glaciers have retreated 150 m to 300 meters which is 10-20% of the glacier length. The retreat of the small glaciers here parallels that of the larger glaciers nearby such as Melbern Glacier.