RECENT ATMOSPHERIC WARMING AND RETREAT OF ICE SHELVES ON THE ANTARCTIC PENINSULA

IN 1978 Mercer(1) discussed the probable effects of climate warming on the Antarctic Ice Sheet, predicting that one sign of a warming trend in this region would be the retreat of ice shelves on the Antarctic Pe ninsula. Analyses of 50-year meteorological records have since reveale d atmospheric warming on the Antarctic Peninsula(2,3), and a number of ice shelves have retreated(4-8). Here we present time-series of obser vations of the areal extent of nine ice shelves on the Antarctic Penin sula, showing that five northerly ones have retreated dramatically in the past fifty years, while those further south show no clear trend. C omparison with air-temperature data shows that the pattern and magnitu de of ice-shelf retreat is consistent with the existence of an abrupt thermal limit on ice-shelf viability, the isotherm associated with thi s limit having been driven south by the atmospheric warming. Ice shelv es therefore appear to be sensitive indicators of climate change.