THE USE OF SATELLITE AND AIRBORNE IMAGERY TO INVENTORY OUTLET GLACIERS OF THE SOUTHERN PATAGONIA ICEFIELD, SOUTH-AMERICA

A Landsat TM mosaic of the Southern Patagonia Icefield (SPI), South Am erica, was utilized as an image base map to inventory its outlet glaci ers. The SPI is South America's largest ice mass with an area of appro ximately 13,000 km(2). The icefield does not have complete topographic map coverage. With the aid of stereoscopic interpretation of aerial p hotographs and digital enhancement of the Landsat TM image, glacier di vides were located and glacier drainage basins were delineated, giving a total of 48 outlet glaciers. Employing a supervised classification using Landsat TM bands 1, 4, and 5, glacier drainage basins were furth er divided into accumulation and ablation areas, thereby determining t he position of the transient snow line (TSL). After comparing with exi sting data, it was found that the TSL could be taken, for practical pu rposes, as the equilibrium line (EL). The position of the TSL was then compared with topographic maps, where available, to determine the equ ilibrium line altitude (ELA). Altogether, 11 parameters relating prima rily to glacier morphology were inventoried. Pio XI Glacier (1265 km(2 )) is found to be the largest outlet glacier in South America, and may also be its longest. The average accumulation area ratio of 0.75 is l arger them those of the Northern Patagonia Icefield and European glaci ers. All but two outlet glaciers calve into fords or proglacial lakes.