Ice-elevation changes of Glaciar Chico, southern Patagonia, using ASTER DEMs, aerial photographs and GPS data

Hielo Patagonico Sur (HPS; southern Patagonia icefield) is the largest temperate ice mass at mid-latitudes in the Southern Hemisphere. With few exceptions, the glaciers in this region have been retreating during the last 50 years. Based on field data, vertical aerial photographs and satellite images, ice-elevation changes since 1975 on Glaciar Chico, one of the main tongues of HPS, are presented. A maximum ice thinning of 5.4 +/- 0.55 m a(-1) was observed at the glacier front between 1975 and 1997. Global positioning system (GPS) data were used in the accumulation area of the glacier to infer a thinning rate of 1.9 +/- 0.14 m a(-1) between 1998 and 2001. This thinning rate is three times higher than the snow accumulation rate estimated for that part of the glacier. A mean net glacier mass balance of -0.29 +/- 0.097 km(3) w.e. a(-1) was estimated between 1975 and 2001. Climate data suggest an increase in temperature and a reduction in precipitation during most of the 20th century in the vicinity of HPS. Although these climate changes are the primary explanation for the observed ice-elevation changes of the glacier, ice-dynamics effects are also believed to play an important role.