RADIOMETRIC DATING OF LAKE-SEDIMENTS FROM SIGNY ISLAND (MARITIME ANTARCTIC) - EVIDENCE OF RECENT CLIMATIC-CHANGE

Sediment cores from three lakes (Moss, Sombre and Heywood) in the mari time Antarctic (Signy Island, South Orkney Islands) have been successf ully dated radiometrically by Pb-210 and Cs-137. Th,,,, inventories of both fallout radionuclides are an order of magnitude higher than that which can be supported by the direct atmospheric flux at this latitud e. The elevated values may be explained by fallout onto the catchment during the winter being delivered directly to the lakes during the ann ual thaw. Two of the lakes (Sombre and Heywood) show marked increases in sediment accumulation after c. 1950. This appears to be associated with a documented rise in temperature in the South Orkney Islands, whi ch has caused extensive deglaciation at Signy Island.