PhD defence, Morten Langer – Niels Bohr Institute - University of Copenhagen

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PhD defence, Morten Langer

Surface melt, dynamics and seismicity at Helheim Glacier, East Greenland


Author: Morten langer
Principal supervisor: Dorthe Dahl-Jensen
External supervisor: Tine B. Larsen (GEUS)

Abstract
As the ice loss from the Greenland ice sheet continues to accelerate, it is becoming crucial to understand the interactions between the climate and the flow-dynamics of the large, fast-flowing outlet glaciers draining the ice sheet. Central in this are studies of the hydraulic conditions beneath the glaciers. This, along with calving of icebergs is believed to play an important role in controlling the flow speed. This PhD thesis investigates the association between surface-generated melt water and flow speed of a large East Greenland outlet glacier. Using meteorological data from the glacier surface, melt-water production from the surface can be estimated. The melt is then compared to GPS observations of flow speed made at the same time. It is demonstrated that the melt-water input has a statistically significant effect on the flow speed. It is also shown that this effect is stronger close to the calving front than farther up on the glacier. Additionally, the effect of melt-water on the flow increases as the season progresses, indicating that the conditions under the glacier change over the summer. Calving of icebergs from the glacier is also investigated using seismic methods. It is clear that ice-loss events occur much more frequently during the summer months, with a maximum reached in September, implying a climatic control on calving.