EARSeL eProceedings 5 th , Remote Sensing of Snow and Glaciers / 2008 1 Firnline detection of the Northern Patagonia Icefield using ERS-1/2 data -An example from San Rafael Glacier- Gonzalo Barcaza 1 and Masamu Aniya 1 1. University of Tsukuba, Graduate School of Life and Environmental Sciences, Ibaraki 305- 8572, Japan; E-mail, gbarcaza@uc.cl: E-mail, aniya@geoenv.tsukuba.ac.jp ABSTRACT The Northern Patagonia Icefield (NPI) is the second largest temperate ice-body in the Southern Hemisphere. Based upon three ERS-1/2 images acquired in March (late summer), July (winter) and October (spring) of 1997, we analyzed seasonal changes in the firn line altitude (FLA) and the accumulation area of San Rafael Glacier. We compared the difference between the FLA and both the equilibrium line altitude (ELA) and the transient snowline (TSL) derived from Landsat data. The FLA is identified at an altitude of ~940 m in 1997, which was ~50 m higher than the ELA. A strong difference in the backscattering coefficients between bare-ice and firn was observed in winter season, indicating glacier surface conditions similar to late-summer. Multitemporal data revealed the seasonal progression of glacier facies and the possible discrimination between bare-ice, firn and two types of wet snow. INTRODUCTION Located in southern Chile, the Northern Patagonia Icefield (NPI) is with 4200 km 2 (i), the second largest temperate ice-body in the Southern Hemisphere (Fig. 1). Despite its importance as a climate change indicator, studies on glacier response to global warming are hampered by the absence of ground-based mass balance, meteorological data near glaciers and persistent cloud cover. Glacier variations indicate a general retreat in the NPI over the past 60 years from 1944/45 to 2004/05 (ii); however, very little is known about its gentle accumulation area. San Rafael Glacier (ca.760 km 2 ) is one of the largest outlet glaciers of Patagonia draining around 18% of the NPI. Because glacier surface conditions (bare-ice or snow-cover) changes in response to meteorological progression such as melting and freezing processes, we used a time series of the European Remote-sensing Satellite -1 and -2 (ERS-1/2), to analyze seasonal changes in both the firn line altitude (FLA) and the accumulation area of San Rafael Glacier during 1997. EARSel/2008