Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise

[1] The digital elevation model (DEM) from the 2000 Shuttle Radar Topography Mission (SRTM) was differenced from a composite DEM based on air photos dating from 1948 to 1987 to determine glacier volume changes in southeast Alaska and adjoining Canada. SRTM accuracy was assessed at ±5 m through comparison with airborne laser altimetry and control locations measured with GPS. Glacier surface elevations lowered over 95% of the 14,580 km glacier-covered area analyzed, with some glaciers thinning as much as 640 m. A combination of factors have contributed to this wastage, including calving retreats of tidewater and lacustrine glaciers and climate change. Many glaciers in this region are particularly sensitive to climate change, as they have large areas at low elevations. However, several tidewater glaciers that had historically undergone calving retreats are now expanding and appear to be in the advancing stage of the tidewater glacier cycle. The net average rate of ice loss is estimated at 16.7 ± 4.4 km/yr, equivalent to a global sea level rise contribution of 0.04 ± 0.01 mm/yr.