The use of satellite and airborne imagery to inventory outlet glaciers of the Southern Patagonia Icefield, South America

Abstract

A Landsat TM mosaic of the Southern Patagonia Icefield (SPI), South America, was utilized as an image base map to inventory its outlet glaciers. The spI is South America's largest ice mass with an area of approximately 13,000 km2. The icefield does not have complete topographic map coverage. With the aid of stereoscopic interpretation of aerial photographs and digital enhancement of the Landsat TM image, glacier divides 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 further divided into accumulation and ablation areas, thereby determining the position of the transient snow line (TSL). After comparing with existing data, it was found that the TSL could be taken, for practical purposes, as the equilibrium line (EL). The position of the TSL was then compared with topographic maps, where available, to determine the equilibrium line altitude (ELA). Altogether, 11 parameters relating primarily to glacier morphology were inventoried. Pio XI Glacier (1265 kmz) is found to be the largest outlet glacier in South America, aid may also be its longest. The average accumulation area ratio of 0.75 is larger than those of the Northern Patagonia Icefield and European glaciers. All but two outlet glaciers calve into fjords or proglacial lakes.