Abstract

This paper models the extent of the Patagonian iceshect during the Last Glacial Maximum (LGM) and its subsequent deglaciation. It constrains a new coupled icesheet/climate numerical model with empirical evidence and simulates the icesheet at the LGM and at stages of deglaciation. Under LGM conditions an icesheet with a modelled volume slightly in excess of 500,000 km(3) builds up along the Andes. There is a marked contrast between the maritime and continental flanks of the modelled icesheet, with positive mass balance exceeding 2 in in the west and declining tenfold to the east. Modelled ice velocities commonly reach 400 in yr(-1) in the western fjords. The model is most sensitive to variations in temperature and good agreement between modelled ice extent and empirical evidence was achieved by applying a temperature decrease of 6degreesC relative to present day temperatures with constant wind fields over the model domain. Assuming a stepped start to deglaciation, modelled ice volumes declined sharply, contributing 1.2 m to global sea level, 80% of it within 2000 years. The empirical record suggests that such a stepped warming occurred around 17,500-17,150 cal yr ago. (C) 2001 Published by Elsevier Science Ltd.