ENVIRONMENTAL HISTORY OF SOUTH GEORGIA, SUB-ANTARCTIC SINCE THE LAST GLACIAL MAXIMUM

We report here the preliminary findings of an integrated study on the environmental history of the island of South Georgia. Fieldwork was carried-out in December 2002 – February 2003. The island lies just south of the Antarctic Polar Frontal Zone (or Antarctic Convergence), a key climatic boundary between southernmost South America and the Antarctic. As such, the island provides a key site for studying the relative phasing of environmental change in Antarctica and the rest of the world. Recent work (Rosqvist et al., 1999) has suggested that LGM ice sheet extent in South Georgia may have been restricted to the inner fjords and that substantial deglaciation may have occurred as early as 18,000 calendar years ago. This is a substantially more restricted glaciation than the continental shelf edge extent suggested by earlier workers. Moreover, the relative early timing of deglaciation suggests that the island was responding to ‘early’ warming in Antarctica, rather than the later warming shown by deglaciation and vegetation response in southern South America.

We are using a combined geomorphological-limnological-modelling approach to test these hypotheses and to understand post-glacial environmental change on the island since the Last Glacial Maximum. There are three linked foci of our work. First, we have carried-out geomorphological mapping of glacial and marine limits at several sites and will date (C-14 and cosmogenic isotopes) these to test the restricted glaciation hypothesis. Second, we have cored several lakes to determine basal dates for deglaciation, as well as Late-glacial to Holocene climate change. The third focus is concerned with understanding the controls on glacier behaviour on South Georgia. For this we are determining detailed historical glacier chronologies and comparing to meteorological records, as well as carrying-out computer modelling of the response of South Georgia glaciers to climate change. The modelling effort will also be tied to the palaeo-glacier chronologies to aid inference of past climate change during the glacial-interglacial transition.

Rosqvist, G. , Rietti-Shati, M. and Shemesh, A. 1999. Late glacial to middle Holocene climatic record of lacustrine silica oxygen isotopes from a Southern Ocean island, Geology, 27(11), 967-970.