Detection of Glacier Surface Conditions and Recent Glacier Variations in Patagonia Using ALOS Data
Masamu Aniya(1), Gonzalo Barcaza(2) and Courage Camusoko(3)
(1) University of Tsukuba, 1537-12 Oi, Tsukuba, Ibaraki 300-1243, Japan
(2) Dirección General de Aguas, Morandé 59 Piso 8, Santiago, Chile
(3) University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
The Patagonia Icefield (PI) is, with 17,200 km2, the largest temperate ice-body in the Southern Hemisphere. It stretches between 46°30’ and 51°30’S along 73°30’W, comprising the Northern Patagonia Icefield (NPI, 4,200 km2) and Southern Patagonia Icefield (SPI, 13,000 km2). Despite its scientific importance because of its location and size, the absence of both meteorological and ground-based mass balance data hampers studies on glacier response to global warming.
Using ALOS PALSAR data acquired in the austral winter of 2007, we analyzed glacier surface conditions of the accumulation area of the NPI (San Rafael and San Quintin glaciers) and the SPI (Jorge Montt and O’Higgins glaciers) by measuring backscatter coefficient along altitudes and detecting four types of the glacier surface (bare-ice, firn and two types of melting facies). We found a strong difference between bare-ice and multi-year firn at the top end of the ablation area, which corresponds to the firn line (FL). Because the current knowledge of the accumulation area of the PI is very limited, the dynamics of satellite-derived boundaries of glacier facies can be used as a baseline for analyzing the effect of global warming, i.e., altitudinal shifts of the melting boundaries and changes in their radar glacier zones.
In addition, we created a partial mosaic of the SPI using PRISM and AVNIR-2 data acquired in 2006/07. It was compared with the Landsat TM data (1986) to elucidate variations of 31 outlet glaciers from 1986 to 2006/07. Together with the previous study, we found out that the most glaciers have retreated continuously with different rates since 1945. This is interpreted as a response to global warming, coupled with local factors such as topography and glacier dynamics.