<--George VI Ice Shelf
Steve Roberts and David Sugden (Edinburgh) have been working with Mike Bentley and James Smith (Durham) and Dominic Hodgson (British Antarctic Survey) to study the Holocene fluctuations of George VI Ice Shelf on the Antarctic Peninsula. In the 1970s Chalmers Clapperton and I found barnacle shells in the moraines around the edge of the ice shelf and they were dated to the early Holocene. We speculated that the ice shelf had disappeared in order to allow the barnacles to live and that they were subsequently overriden by ice and incorporated in the moraine. But we could not rule out the possibility that the shells could live happily beneath the ice shelf. In the present project we homed in on ice-covered lakes impounded by the ice shelf as it flows across George VI Sound and abuts onto the eastern shore of Alexander Island. When, as at present, the lakes exist, a layer of fresh water overlies sea water and there is a mixed fauna and flora, the remains of which accumulate in the bottom sediments. When the ice shelf is absent, then the lakes become marine embayments with only marine organisms accumulating on the bottom.
We cored through the lake ice and found that there were marine sediments, representing an ice-free sound 9,500-8,000 cal. years ago. Moreover, the forams indicated that relatively warm deep water occupied the sound at the time. The inplication is that George VI Ice Shelf had disappeared in the Early Holocene at a time when relatively warm ocean waters bathed the western shores of the Antarctic Peninsula.
George VI Ice Shelf - ablation lake and moutonee lake impounded on Alexander Island by ice shelf-->
Collapse of Ice Shelves in the Antarctic Peninsula area is a hot topic just now because it is such a clear sign of the effects of global warming during the Twentieth Century. It is argued that ice shelves such as Larsen B on the eastern flank of the peninsula, which collapsed recently, have not been so limited in extent for hundreds of thousands of years. In such a case their collapse today is worrying. It seems that a different explanation is needed for George VI Ice Shelf. Ice extent is still more extensive than in the Early Holocene, but of course we don�t know whether conditions are such that the ice shelf has begun to collapse. Also, it may be that it is more sensitive to sea rather than air temperatures and that its response may lag by decades to hundreds of years.
The evidence for the absence of the ice shelf in the early Holocene is in: