Detecting Surface Melt on the Southern Patagonian Icefield using AMSR-E
Abstract
The Southern Patagonian Icefield (SPI) straddles the Andes Mountains between Argentina and Chile, and covers 13,000 km2 in one of the stormiest regions in the world. Passive microwave observations from the Advanced Microwave Scanning Radiometer for Earth Observing Systems (AMSR-E) make it possible to monitor the timing of melting and refreezing on the remote and inaccessible SPI. AMSR-E captures both frozen and wet snow surface features because the presence of liquid water dramatically changes the emissivity of snow. Seasonality has been successfully characterized on glaciers in the northern hemisphere by retrieving surface melt, freeze, and transition duration via the Special Sensor Microwave Imager and AMSR-E. Contrasting mass balance controls on glaciers on the eastern and western sides of the SPI motivates this exploration into the spatial variability of melt condition timing. Temporal melt-refreeze patterns are extracted using brightness temperatures (Tb) and diurnal amplitude variations (DAV). Short-term synoptic variability is superimposed on a distinct annual cycle. The most dramatic melt-refreeze intervals occur in the austral fall. Full resolution (12.5 km) AMSR-E makes it possible to distinguish melt regimes throughout the icefield. Here we use histograms of Tb at 19 and 37 GHz and time series data to characterize melt signatures and contrast them with other large icefields. Histograms of Tb exhibit a normal distribution for low elevation pixels (0-1000m) and show that the surface is often above the melt thresholds, resembling low maritime icefields in Alaska. Similar to high elevation Alaskan icefields, medium to high elevation pixels (above 1000m) have a bimodal distribution with significant periods of high DAV due to daytime melt and nighttime refreeze. On transects from west to east over the SPI, diurnal fluctuation signatures are higher in all seasons except austral winter. Detailed investigation of spatiotemporal patterns in surficial melt contributes key observations in support of mass balance calculations for the whole icefield.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.C31A0454M
- Keywords:
-
- 0740 Snowmelt;
- 0758 Remote sensing