KongElViS: Basal conditions at beginning of Kongsvegen surge revealed using seismic source ElViS

Surge-type glaciers alternate between long periods of slow ice flow, in which ice mass builds up in the accumulation area, followed by a short phase with significantly higher ice speeds in which the mass stored in the accumulation area is transported rapidly downglacier. During the surge phase, glacier speed can increase by up to 2-3 orders of magnitude, compared to the quiescent phase. Ice mass is transported to lower elevations, where warmer conditions lead to increased melt, or in case of tidewater glaciers, to additional loss of mass into the ocean trough increased calving. Basal conditions and the basal thermal regime are considered to play a crucial role in glacier surges, with the sediments underlying the glacier and the basal water pressure variations exerting strong controls on ice flow. Kongsvegen is a well-studied surge-type glacier in the Kongsfjord area of northwest Svalbard. Here we will use active source seismics to investigate the basal properties and the sediment layer below Kongsvegen at the beginning of a surge, to bridge the gap between topographic large-scale information and localized borehole measurements. Seismic waves created at the glacier surface propagate downward to the bottom of the glacier, and are reflected at the interface between the glacier ice and bed. Part of the seismic energy propagates further into the bed where it is reflected at deeper interfaces, yielding information on the sediment structure and thickness below the ice.