February 5, 2016
Ampere-Lapparent Glacier Retreat, Kerguelen Island
Posted by Mauri Pelto
Comparison of Ampere Glacier (A) and Lapparent Glacier (L) southern outlet glaciers of the Cook Ice Cap in 2001 and 2013 Landsat images; red arrow indicates 2001 terminus locations, yellow arrows 2013 terminus locations and purple arrow upstream thinning.
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. Ampere Glacier is the most prominent outlet glacier of the Cook Ice Cap. Berthier et al (2009) noted a retreat from 1963 and 2006 of 2800 meters of the main glacier termini in Ampere Lake (As). The lake did not exist in 1963. A second focus of their work was on the Lapparent Nunatak due north of the main terminus and close to the Ampere Glaciers east terminus (Ae). The nunatak expanded from 1963-2001, in the middle image below from Berthier et al (2009), but it was still surrounded by ice. This is dominated by cloudy weather, with not a single good Landsat image of the glacier since 2013, the January 2016 indicates the snowline, purple dots is similar to 2001.
Map of Kerguelen Island
The main terminus has retreated 800 meters from 2001-2013. Here the terminus has pulled back from the tip of the peninsula on the west side of the terminus and is currently at a narrow point. The eastern terminus has retreated to its junction with the main Ampere Glacier a distance of 1400 m. Berthier et al (2009) had noted thinning around the Lapperent Nunatak of 150 to 250 m, purple arrows indicate this location of thinning. Above the current main terminus the valley widens again to the junction with the location of the eastern terminus. It seems likely the main glacier will retreat north until there is a single terminus north of the southern end of Lapparent Nunatak. Lapparent Glacier was formerly joined with the Ampere Glacier’s eastern outlet. The comparison of Landsat imagery from 2001 and 2013 indicate widespread thinning and deglaciation of this glacier. In 2001 Lapparent Glacier merges with the east terminus of Ampere Glacier at the red arrows with a medial moraine evident. By 2013 the eastern arm has narrowed from 1100 m to 500 meters and retreated 2100 m in 12 years. The result is less ice flow over a bedrock step just above the terminus. This continued thinning since 2001 will lead to further retreat of the glacier. There is no calving and the rate of retreat will decline. A 2009 Landsat image 2009 and 2013 Google Earth image indicate icebergs stranded in the lake by Lapparent Glacier and the eastern outlet indicating glacier lake drainage lowering the level.
2009 Landsat image icebergs evident in lake in the upper right.
2013 Google Earth, icebergs at blue arrow. Highly turbid water in proglacial lakes indicates a recent high flow event.
2016 Landsat image