Characteristics and Mechanism of Glacier Variations in Patagonia, Andes, Revealed by Satellite-data Analyzes.

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We collected a number of remote sensing data which cover the Southern Patagonia Icefield (SPI : 350 km long and 50 km wide) in the southern Andes. The data include Landsat MSS (1976), TM (1986), Spot (1987,1991), and aerial photographs taken in 1945, the late 1960s and 1970s. Analyzing the data, variations since 1945 of eight major outlet glaciers in the SPI were elucidated. During the last 41 years, most glaciers showed a general recession, namely 2.2km at Jorge Montt, 13.4 km at O'Higgins and 2.6 km at Upsala glaciers. On the other hand, Bruggen Glacier advanced 5.3 or 8.4 km in the same period. Thus, it was found that, in Patagonia, some glaciers have behaved in different manners and with different magnitudes of variations.Also as a study of Geographical Information System, various features of glaciers were digitized, and inventories of 48 glaciers in the SPI were completed.With a mass-balance model which includes the calving rate, simulations of glacier variations were made for Upsala and Moreno glaciers. The result shows that a 100 m rise in the equilibrium-line altitude due to climatic change would result in a 200-350 m rise in the frontal altitude at Upsala Glacier corresponding to a retreat of 5-8 km, while it would cause only a 70-100 m rise at Moreno Glacier. Also numerical experiments using a degree-day method were made for Soler Glacier. As a result, a 20% decrease in snow-fall would result in only a 50m rise in the frontal altitude, while a 1^OC increase would result in a 100 m rise in the equilibrium-line altitude. Further experiments with a dynamical model are planned to carry out.