Data and Code for "Comprehensive Radar Mapping of Malaspina Glacier (Sít' Tlein), Alaska—The World's Largest Piedmont Glacier—Reveals Potential for Instability"

Malaspina Glacier, located on the coast of southern Alaska, is the  world's largest piedmont glacier. A narrow ice-cored foreland zone  undergoing rapid thermokarst erosion separates the glacier from the  relatively warm waters of the Gulf of Alaska. Glacier-wide thinning  rates for Malaspina are greater than 1 m/yr, and previous geophysical  investigations indicated that bed elevation exceeds 300 m below sea  level in some places. These observations together give rise to the  question of glacial stability. To address this question, glacier  evolution models are dependent upon detailed observations of Malaspina's  subglacial topography. Here, we map 2,000 line-km of the glacier's bed  using airborne radar sounding data collected by NASA's Operation  IceBridge. When compared to gridded radar measurements, we find that  glaciological models overestimate Malaspina's volume by more than 30%.  While we report a mean bed elevation 100 m greater than previous models,  we find that Malaspina inhabits a broad basin largely grounded below  sea level. Several subglacial channels dissect the glacier's bed: the  most prominent of these channels extends at least 35 km up-glacier from  the terminus toward the throat of Seward Glacier. Provided continued  foreland erosion, an ice-ocean connection may promote rapid retreat  along these overdeepened subglacial channels, with a global sea-level  rise potential of 1.4 mm.

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