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The Cryosphere An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/tc-2020-124
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2020-124
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 20 May 2020

Submitted as: research article | 20 May 2020

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This preprint is currently under review for the journal TC.

Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard

Andreas Alexander1,2, Jaroslav Obu1, Thomas V. Schuler1, Andreas Kääb1, and Hanne H. Christiansen2 Andreas Alexander et al.
  • 1Department of Geosciences, University of Oslo, 0316 Oslo, Norway
  • 2Department of Arctic Geology, The University Centre in Svalbard, 9171 Longyearbyen, Norway

Abstract. Cold glacier beds, i.e. where the ice is frozen to its base, are widespread in polar regions. Common theories state that stable permafrost should exist under glacier beds on shorter time scales, varying from years to decades. Presently, only a few direct measurements of both subglacial permafrost and the processes influencing its thermal regime exist. Here, we present subglacial permafrost and active layer measurements obtained from within the basal drainage systems of two cold-based glaciers on Svalbard during the summer melt season. Temperature observations were obtained from subglacial sediment that was accessed through the drainage systems of the two glaciers in the winters before. The temperature records cover the periods from spring to autumn in 2016 and 2019, at the glaciers Larsbreen and Tellbreen in central Svalbard, respectively. The ground temperature below Larsbreen indicates colder ground conditions, whereas the temperatures of the Tellbreen drainage system show considerably warmer conditions, close to the freezing point. We suggest the latter is due to the presence of liquid water all year round inside the Tellbreen drainage system. Both drainage systems investigated show an increase in subglacial sediment temperatures after the disappearance of snow bridges and the subsequent connection to surface meltwater supply at the start of the summer melt season. Temperature records show influence of sudden summer water supply events, when heavy melt and rain left their signatures on the thermal regime and the erosion of the glacier bed. Observed vertical erosion can reach up to 0.9 m per day at the base of basal drainage channels during summer. We also show that the thermal regime under the subglacial drainage systems is not stable during summer, but experiences several freeze-thaw cycles driven by weather events. Our results show the direct importance of heavy melt events and rain on the thermal regime of subglacial permafrost and the erosion of the glacier bed in the vicinity of subglacial drainage channels. Increased precipitation and surface melt, as expected for future climate, will therefore likely lead to increased degradation of subglacial permafrost, as well as higher subglacial erosion around the preferential hydrological paths. This in turn might have significant impacts on proglacial and fjord ecosystems due to increased sediment and nutrient input.

Andreas Alexander et al.

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Short summary
In this study we present subglacial air, ice and sediment temperatures from within the basal drainage systems of two cold-based glaciers on Svalbard during late spring and the summer melt season. We put the data into context to air temperature and rainfall at the glacier surface and show the importance of surface events on the subglacial thermal regime and erosion around basal drainage channels. Observed vertical erosion rates reach thereby up to 0.9 m per day.
In this study we present subglacial air, ice and sediment temperatures from within the basal...
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