Hubbard Glacier and the Potential Damming of Russell Fiord from Analysis of Small-Aircraft Laser Altimeter Data and NASA SRTM-USGS-Canada DEMs

Small-aircraft Global Positioning System located laser altimeter profile data acquired in Aug. 2003 with a NASA - German Aerospace Center Shuttle Radar Topography Mission (SRTM) X-Band interferometic synthetic radar digital elevation model (DEM) acquired in Feb. 2000 are combined with U.S. Geological Survey and Natural Resource Canada photogrammetric DEMs whose data derive from 1961 and 1976 to estimate elevation changes on Hubbard Glacier and the noted tributary glaciers Valerie and Cathedral. Systematic errors in the earlier DEMs are estimated using fixed terrain. Winter snow depth from Sept. 1999 to 22 Feb. 2000 is estimated and used to adjustment the SRTM DEM elevations. The SRTM DEM elevations are adjusted to a mean sea level reference frame using GEOID99-Alaska (National Geodetic Survey geoid model). Observed surface elevation changes are spatially non-uniform. Valerie and Cathedral show markedly different water equivalent thickening and thinning characteristics apparently due to glacier dynamics. Preliminary results indicate the main flow band of Hubbard shows a draw-down in the upper ablation area of about 1.7 ± 1 m/yr, whereas in the lower accumulation area there is a build-up of about 2.0 ± 1 m/yr in the 1999 to 2003 time period. The middle accumulation area shows a net thickening of about 1.0 ± 1 m/yr, in the 1976 to 2003 time period. The upper accumulation area shows small net thinning of about 0.1 ± 1 m/yr in the same time period. Along the main flow band of Hubbard Glacier a mean thickening of about 0.8 ± 1 m/yr in the 1961/76 to 2003 time period is observed. These changes have occurred in spite of the brief June 2002 damming of Russell Fiord.