Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard
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 timescales, varying from years to decades. Presently, only a few direct measurements of both subglacial permafrost an...
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ftcopernicus:oai:publications.copernicus.org:tc85378 2023-05-15T16:22:12+02:00 Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard Alexander, Andreas Obu, Jaroslav Schuler, Thomas V. Kääb, Andreas Christiansen, Hanne H. 2020-11-26 application/pdf https://doi.org/10.5194/tc-14-4217-2020 https://tc.copernicus.org/articles/14/4217/2020/ eng eng doi:10.5194/tc-14-4217-2020 https://tc.copernicus.org/articles/14/4217/2020/ eISSN: 1994-0424 Text 2020 ftcopernicus https://doi.org/10.5194/tc-14-4217-2020 2020-11-30T17:22:13Z 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 timescales, 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 previous winters. The temperature records cover the periods from spring to autumn in 2016 and 2019 at the glaciers Larsbreen and Tellbreen in central Svalbard. 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 d −1 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 of available sediment around the preferential hydrological paths. This in turn might have significant impacts on proglacial and fjord ecosystems due to increased sediment and nutrient input. Text glacier Ice permafrost Svalbard Copernicus Publications: E-Journals Larsbreen ENVELOPE(15.567,15.567,78.183,78.183) Svalbard Tellbreen ENVELOPE(16.217,16.217,78.250,78.250) The Cryosphere 14 11 4217 4231 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
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 timescales, 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 previous winters. The temperature records cover the periods from spring to autumn in 2016 and 2019 at the glaciers Larsbreen and Tellbreen in central Svalbard. 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 d −1 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 of available sediment around the preferential hydrological paths. This in turn might have significant impacts on proglacial and fjord ecosystems due to increased sediment and nutrient input. |
format |
Text |
author |
Alexander, Andreas Obu, Jaroslav Schuler, Thomas V. Kääb, Andreas Christiansen, Hanne H. |
spellingShingle |
Alexander, Andreas Obu, Jaroslav Schuler, Thomas V. Kääb, Andreas Christiansen, Hanne H. Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard |
author_facet |
Alexander, Andreas Obu, Jaroslav Schuler, Thomas V. Kääb, Andreas Christiansen, Hanne H. |
author_sort |
Alexander, Andreas |
title |
Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard |
title_short |
Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard |
title_full |
Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard |
title_fullStr |
Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard |
title_full_unstemmed |
Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard |
title_sort |
subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in svalbard |
publishDate |
2020 |
url |
https://doi.org/10.5194/tc-14-4217-2020 https://tc.copernicus.org/articles/14/4217/2020/ |
long_lat |
ENVELOPE(15.567,15.567,78.183,78.183) ENVELOPE(16.217,16.217,78.250,78.250) |
geographic |
Larsbreen Svalbard Tellbreen |
geographic_facet |
Larsbreen Svalbard Tellbreen |
genre |
glacier Ice permafrost Svalbard |
genre_facet |
glacier Ice permafrost Svalbard |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-14-4217-2020 https://tc.copernicus.org/articles/14/4217/2020/ |
op_doi |
https://doi.org/10.5194/tc-14-4217-2020 |
container_title |
The Cryosphere |
container_volume |
14 |
container_issue |
11 |
container_start_page |
4217 |
op_container_end_page |
4231 |
_version_ |
1766010175812009984 |