On the glaciology of Edgeøya and Barentsøya, Svalbard
AbstractThe ice masses on Edgeøya and Barentsøya are the least well known in Svalbard. The islands are 42-47% ice covered with the largest ice cap, Edgeøyjøkulen, 1365 km2 in area. The tidewater ice cliffs of eastern Edgeøya are over 80 km long and produce small tabular icebergs. Several of the ice-cap outlet glaciers on Edgeøya and Barentsøya are known to surge, and different drainage basins within the ice caps behave as dynamically separate units. Terminus advances during surging have punctuated more general retreat from Little Ice Age moraines, probably linked to Twentieth Ceutury climate warming and mass balance change. Airborne radio-echo sounding at 60 MHz along 340 km of flight track over the ice masses of Edgeøya and Barentsøya has provided ice thickness and elevation data. Ice is grounded below sea level to about 20 km inland from the tidewater terminus of Stonebreen. Ice thickens from <100 m close to the margins, to about 250 m in the interior of Edgeøyjøkulen. The maximum ice thickness measured on Barentsjøkulen was 270 m. Landsat MSS images of the two islands, calibrated to in-band reflectance values, allow synoptic examination of snowline position in late July/early August. Snow and bare glacier ice were identified, and images were digitally stretched and enhanced. The snowline was at about 300 m on the east side of Edgeøyjøkulen, and 50-100 m higher to the west. Snowlines were at approximately 450 m on Digerfonna and Storskalven. On Barentsjøkulen the snowline was 350 m above sea level on the eastern flank and over 400 m on the west. This asymmetry suggests greater precipitation on the east side of the ice caps. Enhanced Landsat imagery was also used to identify suspended sediments in the waters offshore of the islands. Where this turbid meltwater emerges from tidewater glacier termini, it is likely to be derived from the subglacial drainage system. This suggests that at least parts of the beds of the ice masses on Edgeøya and Barentsøya are at the pressure melting point, and that a basal hydrological system is present.
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