Multi-model photogrammetric analysis of the 1990s surge of Sortebræ, East Greenland

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Abstract
Sortebræ is a surge-type tidewater glacier complex draining southeastward from the Geikie Plateau, East Greenland. Sortebræ’s main flow unit surged around 1950 and again between 1992 and 1995. The 1990s surge affected the lower 50 km of Sortebræ over an area of approximately 335 km2. Over a period of 5 km. Surge velocities in the order of kilometres per annum are about 100-fold the quiescent velocities. Multi-model photogrammetric analysis shows a thinning of the reservoir zone of up to 219 m and thickening of the receiving zone of up to 74 m. The surge transported approximately 18.6 km3 of ice down-glacier. The total calving volume as a result of the surge amounted to 11.7 km3, equivalent to a calving flux of 3.9–7.3 km3 a−1. The surge characteristics and environmental setting suggest that the surge mechanism involves a switch in the subglacial drainage. This surge of Sortebræ is more similar to the fast, short Alaskan-type surges than to the sluggish, long Svalbard-type surges.