Abstract

Ice elevation changes since 1975 and ice areal changes since 1945 of glaciers in the southeastern part of the Southern Patagonia Icefield (SPI) are presented. Comparison of digital elevation models, GPS, and optical survey data revealed high thinning rates for all the ablation areas of the glaciers, with average values between 1.4 and 3.4 m a-1 and maximum ice thinning of 7.6 m a-1. Ice elevation changes for the glacier accumulation areas were smaller than the estimated errors, and no significant trends could be detected. All the glaciers are retreating and shrinking considerably, with a total areal loss of 62.2 km2, which represents 8% of the total ice area of 1945. This trend is in agreement with other similar measurements carried out during recent decades for several glaciers of the SPI. The high thinning rates for the ablation areas of the SPI have been primarily interpreted as a result of the increase in temperature observed in the region, however, this warming trend is not large enough to account for all the ice thinning, indicating that dynamic factors could be important, especially in glaciers which have been thinning dramatically, allowing frontal calving fronts to reach nearly floating conditions. More measurements are needed to test and validate dynamic hypotheses related to glacier behavior in Patagonia. © 2004 Regents of the University of Colorado.