Antarctica on sequential Landsat and ERS SAR images:  King George VI Ice Shelf.
 

Baerbel K. Lucchitta and Christine E. Rosanova          United States Geological
 
Survey, 2255 N. Gemini Dr., Flagstaff, AZ, 86001 
blucchitta@flagmail.wr.usgs.gov; crosanov@flagmail.wr.usgs.gov.


Abstract

The breaking up of  ice shelves on the Antarctic Peninsula has raised 
concerns owing to its linkage to a warming trend  (Vaughan and Doake, 1996, 
Nature, 379, 328-331).  These authors showed that the current -5°C isotherm 
may represent the limit of ice-shelf viability.  The George VI Ice Shelf, 
between Alexander Island and the southern regions of the Antarctic 
Peninsula, lies near this isotherm.   We examined the ice-shelf front for 
recent changes on older Landsat and more recent ERS images.   The 1974 
ice-shelf front (Landsat image) extended from just north of Niznik Island 
all the way across the George VI Sound.  This observation is contrary to the 
portrayal of the front on maps.  The shelf behind this front was complexly 
divided into large shelf segments separated by rifts;  it also included the 
fractured tongue of an unnamed glacier.   Along Alexander Island, the front 
of 1992 and 1995 (ERS images) was near the southern margin of a polynya that 
was already established in 1979.  This position is 30 km back from the 1974 
front.  Along the eastern side of the shelf, the front retreated more than 
20 km from 1974 to 1992, and another 6 km from 1992 to 1995.  The latter 
retreat site retains many small icebergs in situ.  Furthermore, for a 
distance of 8 km along the ice-shelf margin, crevasses  opened to as much as 
1 km wide.  The observations are consistent with Vaughan and Doake's (1996) 
criteria for rapid ice-sheet disintegration and may indicate that the loss 
of ice shelves due to the warming trend is spreading south.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry