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Complex basal conditions and their influence on ice flow at the onset of the Northeast Greenland Ice Stream
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  • Steven Franke,
  • Daniela Jansen,
  • Sebastian Beyer,
  • Tobias Binder,
  • John Paden,
  • Olaf Eisen,
  • Niklas Neckel
Steven Franke
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany

Corresponding Author:[email protected]

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Daniela Jansen
Alfred Wegener Institute, Alfred Wegener Institute, Alfred Wegener Institute
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Sebastian Beyer
MARUM - Center for Marine Environmental Sciences, MARUM - Center for Marine Environmental Sciences, MARUM - Center for Marine Environmental Sciences
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Tobias Binder
Alfred Wegener Institute, Alfred Wegener Institute, Alfred Wegener Institute
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John Paden
Center for Remote Sensing of Ice Sheets (CReSIS), Center for Remote Sensing of Ice Sheets (CReSIS), Center for Remote Sensing of Ice Sheets (CReSIS)
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Olaf Eisen
Alfred Wegener Institute, Alfred Wegener Institute, Alfred Wegener Institute
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Niklas Neckel
Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
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Abstract

The ice stream geometry and large ice surface velocities at the onset region of the Northeast Greenland Ice Stream (NEGIS) are not yet well reproduced by ice sheet models. The quantification of basal sliding and a parametrisation of basal conditions remains a major gap. In this study, we assess the basal conditions of the onset region of the NEGIS in a systematic analysis of airborne ultra-wideband radar data. We evaluate basal roughness and basal return echoes in the context of the current ice stream geometry and ice surface velocity. We observe a change from a smooth to a rougher bed where the ice stream widens, and a distinct roughness anisotropy, indicating a preferred orientation of subglacial structures. In the upstream region, the excess ice mass flux through the shear margins is evacuated by ice flow acceleration and along-flow stretching of the ice. At the downstream part, the generally rougher bed topography correlates with a decrease in flow acceleration and lateral variations in ice surface velocity. Together with basal water routing pathways, this hints to two different zones in this part of the NEGIS: the upstream region collecting water, with a reduced basal traction and downstream, where the ice stream is slowing down and is widening on a rougher bed, with a distribution of basal water towards the shear margins. Our findings support the hypothesis that the NEGIS is strongly interconnected to the subglacial water system in its onset region, but also to the subglacial substrate and morphology.
Mar 2021Published in Journal of Geophysical Research: Earth Surface volume 126 issue 3. 10.1029/2020JF005689