April 12, 2012

Cook Ice Cap Northern Outlet (Aggasiz Glacier) Retreat, new lake born Kerguelen Island

Posted by Mauri Pelto

Kerguelen Island sits alone at the edge of the furious fifties in the southern Indian Ocean. The island features numerous glaciers, the largest being the Cook Ice Cap at 400 square kilometers. A comparison of aerial images from 1963 and 2001 by Berthier et al (2009) indicated the ice cap had lost 21 % of its area in the 38 year period. Le Bris et al (2008) in a related part of the aforementioned study noted that the retreat accelerated after 1970 and again after 2003, with thinning of 5 meters/year on Ampere Glacier and retreat of 75 m/year on Explorer Glacier on the east side of the ice cap. In this post we focus on the largest outlet glacier flowing north from the ice cap, Agassiz Glacier. A comparison of Google Earth (top), 2001 (middle) and 2011 (bottom) Landsat images indicate a significant retreat and formation of a new lake that is not evident in maps or Google Earth imagery. The red arrows point to the glacier tongue and in the 2011 image the black arrow indicates the new lake. Agassiz Glacier has lost its field hockey stick shaped hook and has retreated 2 km in just 10 years, the rate of 200 m/year is quite high even by Cook Ice Cap standards. The glacier is calving into the lake which can accelerate retreat. The terminus does not appear to be at a stable point, with a wide calving front in comparatively deep water. The retreat of this glacier fits the retreat of other glaciers on islands in the Southern Ocean, Arago Glacier, Stephenson Glacier, Neumayer and Ross Hindle