February 9, 2018

Risting Glacier, South Georgia Retreat Expands Drygalski Fjord

Posted by Mauri Pelto

Risting Glacier right and Jenkins Glacier left in Landsat images from 2002, 2015 and 2016.  Red arrow is the 2002 terminus lcoation and yellow arrow at 2016 terminus location.  Dryglaski fjord extends southeast from the glaciers. 

Risting Glacier terminates in Drygalski Fjord on the southeast coast of South Georgia.  Risting and Jenkins Glacier were joined until the 1980’s.  Cook et al (2010) note the glacier had a relatively uniform retreat rate from 1955-1999 of 40 to 50 meters/year, with retreat increasing after 2000. (BAS map).   Gordon et al., (2008) observed that South Georgia’s larger tidewater and sea-calving valley and outlet glaciers generally remained in relatively advanced positions until the 1980’s, Risting Glacier was ahead of this timing in its retreat.

From 2002-2016 Risting Glacier retreated 1100 m, a rate of ~80 m/year twice the 1955-1999 rate. Jenkins Glacier retreated 500 m from 2002-2016 a rate of ~40 m/year.  In the Google Earth image below the slope of Jenkins Glacier suggests the glacier is near the head of the fjord. On Risting Glacier the steepest slope is 2 km behind the calving front, suggestive that the head of fjord is at that point. This location is exceedingly cloudy, making identification of the snowline difficult. The retreat hear is much less than Ross and Hindle Glacier just to the north.  The separation of Jenkins and Risting Glacier is like the separation of Konig and Neumayer Glacier  or Ross and Hindle Glacier.

From the British Antarctic Survey South Geogia GIS online viewer indicating terminus front positions.  Red arrows indicate 2002 positions and 2017 terminus is at yellow arrows.

Front of Jenkins glacier left and Risting Glacier above left, note extensive crevassing of Risting Glacier in particular.