Abstract

A revised glacier inventory comprising glacier changes between 1986 and 2000 have been compiled for the Southern Patagonia Icefield (SPI) based on Landsat TM and Landsat ETMþ imagery acquired on January 14, 1986 and October 27, 2000, respectively. Elevation data from the Shuttle Radar Topography Mission (SRTM) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) were used to interpret ice divides. The 1986 ice area of the 48 major SPI glaciers is 11,022412 km2, which represents 85% of the total SPI area of 13,003282 km2. Our results agree in general with Aniya et al. (1996), although there are large differences in the basin limits for a few glaciers. Area loss of 489377 km2 is obtained for the period 1986–2000 for the whole SPI, of which 68% corresponds to the 48 major glaciers (333106 km2). Major (>5 km2 ) area loss is detected in 20 glaciers (26887 km2), which accounts for 80% of the total area loss of the major glaciers between 1986 and 2000. Smaller (<5 km2) but significant area losses have occurred within 17 other glaciers, all of which have retreated more than 100 m. While our new results confirm the general retreat of the SPI reported earlier (Aniya et al. 1997; Rignot et al. 2003), we show that 9 glaciers within the latitudes of 49480–50250S had relatively stable frontal positions between 1986 and 2000, 8 of which were previously retreating over the period 1944/1986. Independent evaluation of ice thickness changes within the SPI (Rignot et al. 2003) show that significant thinning exists for only 2 of the 9 glaciers with stable fronts (excluding Moreno Glacier which we regard as stable). The stable frontal positions of the 13 glaciers might be due to the recent increase of precipitation in the central–south sector of the SPI. Although enhanced precipitation has not yet been detected by observations, it is to be expected based on the intensification of the westerly circulation, as has already been observed in the Southern Hemisphere since the mid-1960s (Marshall, 2003).