Alaskan Glacier Depths from a Decade of Airborne Radar Sounding

Brandon Scott Tober, Michael Steven Christoffersen, John W Holt, Martin Truffer, Christopher F Larsen

NASA’s Operation IceBridge employed airborne radar sounders in Alaska and adjacent northwestern Canada between 2012-2021 to measure the thickness of the region’s glaciers. Here we present the first comprehensive analysis of these data, providing over 5,500 linear-km of ice thickness and bed elevation measurements – constituting the greatest ice thickness inventory for this region to date. Aside from glaciers of the Saint Elias Mountains, radar bed returns are limited to expansive accumulation areas and glacier termini, distant from sources of off-nadir surface topography. Gridded measurements across Bering Glacier reveal a subglacial trough extending over 50 km from the glacier's terminus up to the Bagley Ice Valley, likely a subglacial expression of the Bering Fault. We find that many of the glacier termini successfully sounded by Operation IceBridge have overdeepened beds, which may offer insight into the potential extent of proglacial lakes and associated natural hazards given continued thinning and retreat. While the long-wavelength sounders employed by Operation IceBridge have proven capable of sounding through nearly 1500 m of temperate ice, radar surface returns from the flanks of the region’s mountain glaciers remain the greatest challenge to identifying glacier bed returns and retrieving ice thickness measurements. Simulating these returns in the survey planning may significantly improve the mapping success of future airborne radar campaigns.