HR: 15:10h
AN: C33A-07    [Abstracts]
TI: Interpretation of ICESat-Derived Elevation Change on the Malaspina-Seward Glacier
AU: * Sauber, J
EM: jeanne@steller.gsfc.nasa.gov
AF: Planetary Geodynamics Laboratory, Code 698, Greenbelt, MD 20771 United States
AU: Ramage, J
EM: ramage@lehigh.edu
AF: Lehigh University, 31 Williams Drive, Earth and Environmental Sciences, Bethlehem, PA 18015 United States
AU: Kopczynski, S
EM: seka@lehigh.edu
AF: Lehigh University, 31 Williams Drive, Earth and Environmental Sciences, Bethlehem, PA 18015 United States
AU: Muskett, R
EM: muskett@iarc.uaf.edu
AF: University of Alaska Fairbanks, Internat. Arctic Res. Center, Fairbanks, AK 99775 United States
AB: In this study, we report and interpret ICESat-derived short-term variability in surface elevation in the snow accumulation region of the Seward-Malaspina Glacier, one of the largest glacier systems in southern Alaska. The Seward-Malaspina complex consists of an extensive icefield, the upper Seward Glacier, and a narrower lower outlet glacier (lower Seward) through which ice drains to the enormous piedmont of the Malaspina Glacier. Although the upper Seward is just 80 km north of the Gulf of Alaska it has an environment more continental than maritime because of shielding afforded by high mountains to the south [Sharp, 1951]. The Malaspina Glacier by contrast lies completely within the moist maritime environment of the southern Alaska coast. In an earlier study of the Malaspina Glacier, we reported elevation differences between ICESat Laser 1-3 observations (February 2003 - November 2004) and a Shuttle Radar Topography Mission (SRTM)-derived DEM from February 2000 [Sauber et al., 2005]. Elevation decreases of up to 20-25 m over a 3-4 year time period were observed across the folded loop moraine on the southern portion of the piedmont lobe of the Malaspina Glacier. For the western portion of the Upper Seward we will estimate elevation change over a comparable time period by using an X-band InSAR-derived DEM from Intermap Tech. (Sept. 2000) and ICESat-derived elevations. Early field measurements (1945-1949) from the Upper Seward Glacier indicated an average annual net surplus of 75 cm water equivalent in the Upper Seward basin [Sharp, 1951]. However, even over this short time period, Sharp [1951] found large interannual variability in net accumulation of 41-168 cm. To further constrain and understand surface changes, we examined ICESat-derived elevations from a variable set of repeated ICESat upper Seward profiles made between Feb. 2003 and May 2005. Additionally we compared the elevation change profiles to snowmelt timing and ablation season length derived from the Special Sensor Microwave Imager (SSM/I) 37 GHz brightness temperatures for 2000-2004 using the approach of Ramage and Isacks (2003). We found the largest elevation increase between Oct 2003 and late Feb./March 2004 (3-4 m over a flat region of the upper Seward at 1740 m), little discernible elevation change occurred between March and May 2004, and about 2 m of elevation decrease occurred at 1750 m between May and Oct. 2004. The elevation increase of 3-4 m at 1740 m in the upper Seward occurred after refreezing started in August 2003 and before the snowmelt onset in mid to late April 2004. Ramage and Isacks, J. Glaciol., 2003. Sauber et al., Geophys. Res. Lett., in press, 2005. Sharp, Geol. Soc. Am.,1951.
DE: 0720 Glaciers
DE: 0762 Mass balance (1218, 1223)
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 1827 Glaciology (0736, 0776, 1863)
DE: 1863 Snow and ice (0736, 0738, 0776, 1827)
SC: Cryosphere [C]
MN: Fall Meeting 2005