On the east side of the Cook Ice Cap on Kerguelen Island a series of outlet glaciers have retreated expanding and forming a new group of lakes, red arrow. This area is just south of Lac du Chamonix which has existed. Here we examine the changes from 2001-2014 along using Landsat imagery. This is a retreat examined by Berthier et al (2009), and exemplified by the retreat of Ampere Glacier and Aggasiz Glacier from the same ice cap.
In 2001 at the red arrow is the north tributary of a glacier ending in the northernmost lake at the pink arrow. In the second lake is an island, marked with point A, this glacier has a secondary terminus ending at the yellow arrow. The southernmost glacier examined at the green arrow has retreated from one lake and does not end in a lake. By 2011 the northern tributary is starting to separate losing its connection with the Cook Ice cap, red arrow and retreating from the pink arrow. The distance from the island for the middle glacier has increased. A lake is forming at the yellow arrow. For the third glacier a lake has formed at the green arrow. The 2013 Landsat image still has snowcover obscuring the glacier boundaries. In January 2014, it is evident that at the red arrow the northern tributary has lost all connection with the Cook Ice Cap. The main terminus has retreated 700 m, expanding the lake it terminates in. With the loss of the northern tributary the retreat will continue. The distance from the island at Point A to the terminus of the middle glacier has increased 900 m indicating the retreat since 2001. The glacier is nearly at the western end of the lake it terminates in. At the yellow arrow the new lake is now 900 m long indicating a retreat of slightly less than this. The green arrow marks the 2013 terminus in each image of the southern of the three glaciers. This glacier has retreated 800-900 m leading to the continued expansion of a new lake. In just a decade we see the formation of two new lakes and the expansion of two others at the terminus of the three eastern outlet glaciers of Cook Ice Cap.
Kerguelen Island sits alone isolated 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. Here we focus on the Arago Glacier and an adjacent glacier to the south on an icecap on the Raillier du Bay Peninsula Ice Cap using satellite imagery from 2001-2011. Arago Glacier descends east from the ice cap currently ending in a proglacial lake.
Kerguelen Island Map
Rallier du Baty Peninsula Google Earth image
Berthier et al (2009)note that this glacier had retreated 3 km from 1964-2001. In 1964 the glacier filled the lake basin, yellow line in first figure below. They had a single profile across the glacier shortly above the terminus that indicated 80 km of thinning from 1964-2000 and 30 m from 2000-2005. The profile is the blue dotted line from their paper in the first figure below. In 2001 Arago Glacier terminated at the tip of a peninsula, yellow arrow. The Arago Glacier is joined just above the terminus by a tributary from the north, which has a substantial width in 2001 at the pink arrow. The glacier to its south ended at the northern end of a lake, red arrow. By 2006 Arago Glacier has retreated from the peninsula. Cloud cover obscures the glacier to the south. By 2011 Arago Glacier has retreated from the peninsula, 300-400 m since 2001, expanding the proglacial lake. The glacier tributary at the pink arrow width has declined substantially. This is indicative of a thinning glacier as well. The contribution of this tributary to the main terminus is quite limited by 2011. The glacier to the south at the red arrow has also retreated 300-400 m, leading to lake expansion there. This island is notoriously cloud covered, and I have not located an image with a clear view of the region since 2011, when I do the post will be updated. The retreat of Arago Glacier follows the pattern of retreat of the glaciers of other glaciers on the island including Ampere Glacier and the northern outlet of the Cook Island Ice Cap
Figure 8 from Berthier et al (2009)
Landsat image in 2001
Landsat image from 2006
Landsat image from 2011
Landsat image from 2014
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. In this paper they focused particular attention on the Ampere Glacier, pink arrow in first image, draining the southeast side of the ice cap, that had retreated 2800 meters from 1963 to 2006. Berthier et al (2009) had a second focus on the Lapparent Nunatak due north of the main terminus and close to the east terminus, referred to hear as the Lapparent Outlet. A nunatak is a ridge or mountain surrounded by a glacier, really an island in a sea of ice. The nunatak expanded from 1963-2001, in the second image below from Berthier et al (2009), but it was still surrounded by ice. . In this post we examine changes at the terminus and at several points upglacier in 2001 and 2011 Landsat imagery that indicate widespread thinning and deglaciation. In each image the letters are in the same location as are the colored arrows. The green arrow indicates the 2001 terminus of the outlet and the burgundy arrow the 2011 terminus, indicating a 2 km retreat in a single decade for the southern calving terminus and for the northern terminus above point D 2200 meters of retreat. In 2001 the region around letter D is a filled by the northern arm encircling the Lapparent Nunatak, by 2011 D is in a deglaciated valley. B marks the southern end of the 2011 terminus. F in 2011 marks a location where the Lapparent Outlet spills over a ridge into another valley, by 2011 the overflow has narrowed from 1100 meters to just 500 meters in ten years. The result is less ice flow into the secondary basin, including down a bedrock step to point E. Point E in 2001 is in the midst of the lower reach of the glacier. By 2011 there is no ice near point E as the glacier no longer descends to this lower step. Point A in a nunatak 4 km inland from the Ampere and Lapperent Outlet terminus, this nuntak has expanded from a long axis of 1100 meters to 1500 meters. Berthier et al (2009) had noted thinning around the Lapprent Nunatak of 150 to 250 m. This continued thinning since 2001 is leading to further expansion of the nunatak at A and to reduced ice spillover at point F. This island and glacier is experiencing the same climatic warming that is causing retreat of other glaciers in this circum-Antarctic latitude belt, Stephenson Glacier on Heard Island, Neumayer Glacieror Ross Hindle Glacier on South Georgia and on the north side of Cook Ice Cap, Kerguelen Ice Cap.