February 4, 2015
Bertrab Glacier is on the east coast of South Georgia Island. 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 the coast in Gold Harbor. 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 Bertrab Glacier the retreat was minimal from 1958 to 1989. Since 1989 a whole new embayment has opened. Here we examine Landsat imagery from 1989 to 2015 to visualize and update this change.
BAS Glacier Front map 1958-2007.
Google Earth image
In 1989 the southern arm of the glacier extends to the shoreline of the barrier beach system in Gold harbor, Red arrow. The northern arm extends around to the edge of a very green region, suggesting well developed vegetation, hence no real retreat for sometime. By 2002 a lake has formed at the northern arm terminus and it has retreated 400 m. The southern arm has retreated across a new embayment ending near the yellow arrow, though the exact position is obscured by cloud. In 2011 the southern terminus has retreated up a slope from the edge of the embayment, yellow arrow. In 2015 there are no longer two arms to the glacier. The glacier terminates near the edge of the new embayment. The retreat is 700 m on the northern arm and 1000 m for the southern end since 1989. The glacier no longer reaches the water limiting calving. The glacier also ends on moderate slope. This should lead to a reduced retreat in the near future. The 2015 picture is from Jan.15, so there is still two months left in the melt season. The retreat is similar to that of Ross Hindle Glacier , Konig Glacier and Neumayer Glacier on the same coast of South Georgia, and faster than for neighboring Weddel Glacier. Like on Stephenson Glacier, Heard Island the new embayment does offer new potential habitat for penguins and seals.
2002 Landsat image
2011 Landsat image
2015 landsat image