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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. They are a significant source of uncertainty in present ice sheet projections towards their future contribution to sea-level rise. 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 this region, we also find an apparent increase of the bed return power towards the centre of the ice stream, potentially indicating increased water content at the base. At the downstream part, we observe an increased bed return power throughout the entire width of the ice stream and outside its margins. Together with basal water routing pathways, this hints to two different zones in this part of NEGIS: the upstream region collecting water, reducing basal traction, and in the further downstream part the distribution of basal water underneath and beyond the shear margins. Our findings support the hypothesis that the NEGIS is strongly controlled by the subglacial water system in its onset region.
Mar 2021Published in Journal of Geophysical Research: Earth Surface volume 126 issue 3. 10.1029/2020JF005689