21st-century increase in glacier mass loss in the Wrangell Mountains, Alaska, USA, from airborne laser altimetry and satellite stereo-imagery

摘要

Alaskan glaciers are among the largest regional contributors to sea-level rise in the latter half of the 20th century. Earlier studies have documented extensive and accelerated ice wastage in most regions of Alaska. Here we study five decades of mass loss on high-elevation, land-terminating glaciers of the Wrangell Mountains (∼4900 km2) in central Alaska based on airborne center-line laser altimetry data from 2000 and 2007, a digital elevation model (DEM) from ASTER and SPOT5, and US Geological Survey topographic maps from 1957. The regional mass-balance estimates derived from center-line laser altimetry profiles using two regional extrapolation techniques agree well with that from DEM differencing. Repeat altimetry measurements reveal accelerated mass loss over the Wrangell Mountains, with the regional mass-balance rate evolving from -0.07±0.19 m w.e.a-1 during 1957-2000 to -0.24±0.16 m w.e.a-1 during 2000-07. Nabesna, the largest glacier in this region (∼1056 km2), lost mass four times faster during 2000-07 than during 1957-2000. Although accelerated, the mass change over this region is slower than in other glacierized regions of Alaska, particularly those with tidewater glaciers. Together, our laser altimetry and satellite DEM analyses demonstrate increased wastage of these glaciers during the last 50 years.