November 10, 2011

Retreat of Prospect Glacier, Antarctic Peninsula

Posted by Mauri Pelto

Prospect Glacier flows into the Sea on the E=West Coast of Antarctica. The glacier used to drain into the Wordie Ice Shelf which was formerly located at 69o on the west coast of the Antarctic Peninsula. In a joint study released by the USGS and British Antarctic Survey (BAS) the history of the Wordie Ice Shelf is reviewed. Below is the view in a Landsat 1979 image of the ice shelf. . The ice shelf advanced from 1947 to 1966. The ice shelf advanced on the northern end and retreated on the southern end from 1966 to 1974. The retreat at the southern end where Prospect Glacier fed the ice sheet was 1-2 km. By 1989 an additional 2 km of retreat had occurred. From 1989 to 1997 a general advance of the ice shelf occurred. From 1999 to 2001 retreat of 3-10 km occurred which marked the end of the ice shelf. The retreat is summarized in a figure from the USGS(2011). . The demise of the Wordie Ice Shelf was first documented by D.Vaughan and C.Doake (1991) of the BAS. The USGS long term project of mapping the changes with Landsat has been led by R. Williams, C.Swithinbank and J.Ferrrigno Examination of recent Landsat imagery indicate continued retreat of Prospect Glacier like its neighbor Fleming Glacier since ice shelf loss. A comparison of the ice front in the Prospect Glacier area is indicated in Landsat imagery from 1989 (top), 2002 (middle) and 2009 (bottom). Mount Balfour is at the northern edge of the Prospect Glacier, and may well become an island. The retreat is more pronounced on the southern side of the glacier note the locations A-E are the same prominent mountain features in the 2002 and 2009 images. The terminus is retreating eastward along Mount Balfour, from 1989-2002 but not significantly from 2002-2009. . A closeup view of the 2009 terminus indicates considerable rifting near the ice front, that represent icebergs that will soon calve off leading to further retreat. Surface melt in this area is quite limited, and the loss of the ice shelf through thinning and then rifting and breakup must have been triggered in part by increased basal melt. With the loss of the ice shelf, there is less back force slowing glacier motion at the ice front. The acceleration is leading to further thinning and continued extensive rifting. Rifts are indicated by red arrows and are likely due to basal crevasses expanding towards the surface.