Using GIS and Remote Sensing to Map the Bedrock Morphology of Bering Glacier, Alaska

Abstract:

Subglacial environments are amongst the least known places on Earth. We have combined five different types of geophysical investigations in order to better understand the complex morphology of the >250 km long bed of Bering Glacier. The transect includes the bed segment underlying the present glacier and the segment previously under the glacier’s seaward extension when it reached its maximum limit during the Pleistocene. This transect represents Bering Glacier’s bed from the distal edge of the continental shelf, to its up-glacier point of origin east of the U.S.-Canadian border.

The datasets used were: 1) marine air-gun and sparker seismic profiles used to define the bedrock morphology of Bering Trough, Bering Glacier’s Pleistocene fiord cut into the Gulf of Alaska; 2) binary-explosive seismic refraction profiles used to confirm that fiord depth bedrock underlies the Bering Foreland coastal plain; 3) high-resolution mini-sparker seismic reflection profiles collected from Vitus Lake, Bering Glacier’s ice marginal lake that confirm complex bed morphology buried under up to 100 m of recent glacial-marine sediment; 4) ice penetrating radar soundings used to measure the ice thickness and depth to bedrock at more than 30 Bering Glacier piedmont lobe locations; and 5) airborne monopulse radar profiles used for mapping nearly 190 km of glacier’s current bed.

Combining the results of these five geophysical investigations permits us to produce numerous cross-sections and maps that show the complexities of Bering Glacier’s bedrock morphology. At its offshore end on the outer continental shelf, the bed is a trough as deep as 500 m below sea level. At its origin, east of the U.S.-Canadian Border the bed elevation is ~1,600 m above sea level.