Measuring the mass balance and contribution to sea level rise of North American glaciers using remote sensing techniques

Volume and surface elevation changes were calculated for six icefields throughout Alaska and British Columbia by differencing Digital Elevation Models (DEMs) that represent glacial elevations from different time periods. For the Harding Icefield on the Kenai Peninsula in southcentral Alaska, United States Geological Survey (USGS) DEMs from the 1950s were differenced with Shuttle Radar Topographic Mission (SRTM) DEMs from 2000 (effective 1999 elevations). Results indicated that the icefield had a volume loss of -72.1 +/-15.0 km3, which equates to 0.0033 +/- 0.0006 mm y-1 of sea level rise contribution. Along with these results, Light Detecting and Ranging (Lidar) elevation data of 13 Harding Icefield glaciers from the mid-1990s provided a third elevation data set for comparison with the USGS and SRTM DEMs. The results from these surface elevation change calculations indicated that surface elevation change rates increased by 1.5 times from the mid-1990s to 1999 (-0.72 +/- 0.13 m y-1) as compared to the 1950s to the mid-1900s (-0.47 +/- 0.01 m y-1).; In southwest British Columbia, five icefields were studied: Monarch, Ha-Iltzuk, Mt. Waddington area, Homathko, and Lillooet. Terrain Resource Information Management (TRIM) DEMs from the mid-1980s were differenced from the SRTM DEMs to calculate the volume and surface elevation change of the five icefields. Results from these calculations indicate that between the mid-1980s and 1999 the total volume change of the five icefields was a loss of -47.72 +/- 14.62 km3, which equates to a potential sea level rise contribution of 0.0077 +/-0.0021 mm y-1.; A DEM of a third time period was produced by kriging elevation points derived from 1970s topographic maps, and used to calculate volume and surface elevation changes of Ha-Iltzuk Icefield for the time period of 1970 to the mid-1980s. The results of this analysis indicate that Ha-Iltzuk Icefield had a volume loss of -5.87 +/- 2.89 km3 and a surface elevation change rate of -0.58 +/- 0.30 m y-1. This also indicates that the surface elevation change rate of Ha-Iltzuk Icefield has increased by 3.5 times when compared to the surface elevation change rate between the mid-1980s and 1999 (-2.03 +/- 0.47 m-1). If the increase in thinning rates experienced by the Harding and Ha-Iltzuk Icefields continues, these and other similarly sized icefields at the same latitudes in North America are likely to be completely melted within the next 500 years.