Spatial and temporal variations of glacier extent across the Southern Patagonian Icefield since the 1970s

Abstract. A combination of Landsat and ASTER satellite scenes, from the 1970s to late-2000s, were used to quantify changes in the extent of glaciers in 130 basins across the Southern Patagonian Icefield (SPI). There was extensive net overall loss, with a reduction in ice area of ∼ 420 km² (∼ 3% of the SPI) between 1984/86 and 2008/10. For glaciers which retreated, the mean annual loss rate was 0.19 km² yr⁻¹ between 1976/79 and 1984/86, 0.16 km² yr⁻¹ between 1984/86 and 2000/02, and 0.16 km² yr⁻¹ between 2000/02 and 2008/10. Since the 1980s, glaciers located in the northwest quadrant of the SPI experienced the highest mean annual loss rates, at 0.22 km² yr⁻¹, while those in the southwest experienced the lowest mean annual loss rates, at 0.06 km² yr⁻¹. NCEP/NCAR climate reanalysis indicates that mean monthly surface air temperatures have increased by an average of +0.12 °C decade⁻¹ (p = 0.0002) since 1950, particularly during the winter season, resulting in a~change from mean negative to mean positive monthly winter temperatures and the earlier onset of spring. Increased winter temperatures have likely caused a switch in precipitation type from snow to rain and an associated reduction in glacier mass balance, even though there has been no significant trend in total annual precipitation over this period.