Bering Glacier ablation measurements

Bering Glacier is rapidly retreating and thinning since it surged in 1993–1995. From 2002 to 2007 we have mapped the terminus position and measured the surface ablation from the terminus region up-glacier to the snowline in the Bagley Ice Field. Since the last surge the terminus has retreated, primarily by calving, ~0.4–0.5 km/a, and the terminus position is at the 1992 pre-surge position. The glacier surface in the terminus region is presently downwasting by melting at ~8–10 m/a and 3.5–6.0 m/a at the approximate altitude of the equilibrium line, 1200 m. The average daily melt for Bering Glacier is ~4–5 cm/d at mid-glacier, and this melt rate appears to be steady, regardless of insulation and/or precipitation. The melt from the Bering Lobe of the glacier system generates between 8 and 15 km3of fresh water yearly, which flows directly into the Gulf of Alaska via the Seal River, potentially affecting its circulation and ecosystem. Elevation measurements from 1957 compared with our measurements made in 2004, combined with bed topography from ice penetrating radar, show that the Bering Lobe has lost ~13% of its total mass.