February 8, 2015

Weddel Glacier Thinning-Retreat, South Georgia Island

Posted by Mauri Pelto

Weddel Glacier is on the southeast coast of South Georgia Island.  It terminates in Beaufoy Cove just north of Gold Harbor.The change in glacier terminus position has been documented by Alison Cook at British Antarctic Survey in a BAS retreat map.  In 1958 it reached within 400 m of the coast at the outlet of Beaufoy Cove. Gordon et al., (2008) observed that larger tidewater and sea-calving valley and outlet glaciers generally remained in relatively advanced positions until the 1980s. For Weddel Glacier the retreat was rapid from 1960 to 1974 and was slow from 1992-2003.  Here we examine Landsat imagery from 1989 to 2015 to visualize and update this change.
bertrab ge
Google Earth Image

weddell-bertrab map
BAS map of glacier terminus position

In 1989 the glacier terminates near the tip of a peninsula, red arrow in each image. The calving front extends southeast, orange dots. At the yellow arrow the glacier fills a small side valley adjacent to the main glacier. At the purple arrow is a small extension of the main icefall flowing down the bedrock step.
In 2002 there is only minor retreat at the red and yellow arrow, but thinning has led to the small extension of the main icefall being almost cutoff by bedrock. By 2015 the glacier has retreated 200-300 meters from the 1989 position and the main terminus is narrower. At the yellow arrow the side valley no longer has ice. At the purple arrow this is just bedrock now, there is no glacier extension flowing down the bedrock step. A close up the icefall in a 2009 Google Earth image indicates both the extensive crevassing but also the lack of glacier ice at the purple arrow, where an extension of the icefall formerly flowed. A Google Earth closeup of the terminus indicates that only a small section is still in contact with Beaufoy Cove in 2009, with land exposed at the orange arrows. This glacier is almost not tidewater and has terminated in shallow water since 1989, which helps explain a slower rate of retreat. The glacier has thinned more rapidly than it has retreated in the last 25 years. The retreat rate is less than nearby Bertrab Glacier, Konig Glacier and Neumayer Glacier on the same coast of South Georgia.

weddel glacier 1989

Landsat Image 1989

weddell glacier 2002

Landsat image 2002

weddel glacier 2015
Landsat image 2015

weddel icefall
Google Earth icefall image
weddel terminus
Google Earth 2009 image