Non-linear retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry
Rapid acceleration and retreat of Greenland's marine-terminating glaciers during the last two decades have initiated questions on the trigger and processes governing observed changes. Destabilization of these glaciers coincides with atmosphere and ocean warming, which broadly has been used to e...
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ftunivbergen:oai:bora.uib.no:1956/17509 2023-05-15T16:21:31+02:00 Non-linear retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry Steiger, Nadine Nisancioglu, Kerim H. Åkesson, Henning Fleurian, Basile de Nick, Faezeh M. 2017-09 application/pdf https://hdl.handle.net/1956/17509 https://doi.org/10.5194/tc-2017-151 eng eng Copernicus Publications on behalf of the European Geosciences Union Deglaciation of the Norwegian fjords urn:issn:1994-0424 urn:issn:1994-0416 https://hdl.handle.net/1956/17509 https://doi.org/10.5194/tc-2017-151 This work is distributed under the Creative Commons Attribution 4.0 License. https://creativecommons.org/licenses/by/4.0/ Copyright Author(s) 2017. The Cryosphere VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 Journal article 2017 ftunivbergen https://doi.org/10.5194/tc-2017-151 2023-03-14T17:39:49Z Rapid acceleration and retreat of Greenland's marine-terminating glaciers during the last two decades have initiated questions on the trigger and processes governing observed changes. Destabilization of these glaciers coincides with atmosphere and ocean warming, which broadly has been used to explain the rapid changes. To assess the relative role of external forcing versus fjord geometry, we investigate the retreat of Jakobshavn Isbræ in West Greenland, where margin positions exist since the Little Ice Age maximum in 1850. We use a one-dimensional ice flow model and isolate geometric effects on the retreat using a linear increase in external forcing. We find that the observed retreat of 43 km from 1850 until 2014 can only be simulated when multiple forcing parameters – such as hydrofracturing, submarine melt and frontal buttressing by sea ice – are changed simultaneously. Surface mass balance, in contrast, has a negligible effect. While changing external forcing initiates retreat, fjord geometry controls the retreat pattern. Basal and lateral topography govern shifts from temporary stabilization to rapid retreat, resulting in a highly non-linear glacier response. For example, we simulate a disintegration of a 15 km long floating tongue within one model year, which dislodges the grounding line onto the next pinning point. The retreat pattern loses complexity and becomes linear when we artificially straighten the glacier walls and bed, confirming the topographic controls. For real complex fjord systems such as Jakobshavn Isbræ, geometric pinning points predetermine grounding line stabilization and may therefore be used as a proxy for moraine build-up. Also, we find that after decades of stability and with constant external forcing, grounding lines may retreat rapidly without any trigger. This means that past changes may precondition marine-terminating glaciers to reach tipping-points, and that retreat can occur without additional climate warming. Present-day changes and future projections can therefore not be ... Article in Journal/Newspaper glacier Greenland Jakobshavn Jakobshavn isbræ Sea ice The Cryosphere University of Bergen: Bergen Open Research Archive (BORA-UiB) Greenland Jakobshavn Isbræ ENVELOPE(-49.917,-49.917,69.167,69.167) |
institution |
Open Polar |
collection |
University of Bergen: Bergen Open Research Archive (BORA-UiB) |
op_collection_id |
ftunivbergen |
language |
English |
topic |
VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 |
spellingShingle |
VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 Steiger, Nadine Nisancioglu, Kerim H. Åkesson, Henning Fleurian, Basile de Nick, Faezeh M. Non-linear retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry |
topic_facet |
VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 |
description |
Rapid acceleration and retreat of Greenland's marine-terminating glaciers during the last two decades have initiated questions on the trigger and processes governing observed changes. Destabilization of these glaciers coincides with atmosphere and ocean warming, which broadly has been used to explain the rapid changes. To assess the relative role of external forcing versus fjord geometry, we investigate the retreat of Jakobshavn Isbræ in West Greenland, where margin positions exist since the Little Ice Age maximum in 1850. We use a one-dimensional ice flow model and isolate geometric effects on the retreat using a linear increase in external forcing. We find that the observed retreat of 43 km from 1850 until 2014 can only be simulated when multiple forcing parameters – such as hydrofracturing, submarine melt and frontal buttressing by sea ice – are changed simultaneously. Surface mass balance, in contrast, has a negligible effect. While changing external forcing initiates retreat, fjord geometry controls the retreat pattern. Basal and lateral topography govern shifts from temporary stabilization to rapid retreat, resulting in a highly non-linear glacier response. For example, we simulate a disintegration of a 15 km long floating tongue within one model year, which dislodges the grounding line onto the next pinning point. The retreat pattern loses complexity and becomes linear when we artificially straighten the glacier walls and bed, confirming the topographic controls. For real complex fjord systems such as Jakobshavn Isbræ, geometric pinning points predetermine grounding line stabilization and may therefore be used as a proxy for moraine build-up. Also, we find that after decades of stability and with constant external forcing, grounding lines may retreat rapidly without any trigger. This means that past changes may precondition marine-terminating glaciers to reach tipping-points, and that retreat can occur without additional climate warming. Present-day changes and future projections can therefore not be ... |
format |
Article in Journal/Newspaper |
author |
Steiger, Nadine Nisancioglu, Kerim H. Åkesson, Henning Fleurian, Basile de Nick, Faezeh M. |
author_facet |
Steiger, Nadine Nisancioglu, Kerim H. Åkesson, Henning Fleurian, Basile de Nick, Faezeh M. |
author_sort |
Steiger, Nadine |
title |
Non-linear retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry |
title_short |
Non-linear retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry |
title_full |
Non-linear retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry |
title_fullStr |
Non-linear retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry |
title_full_unstemmed |
Non-linear retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry |
title_sort |
non-linear retreat of jakobshavn isbræ since the little ice age controlled by geometry |
publisher |
Copernicus Publications on behalf of the European Geosciences Union |
publishDate |
2017 |
url |
https://hdl.handle.net/1956/17509 https://doi.org/10.5194/tc-2017-151 |
long_lat |
ENVELOPE(-49.917,-49.917,69.167,69.167) |
geographic |
Greenland Jakobshavn Isbræ |
geographic_facet |
Greenland Jakobshavn Isbræ |
genre |
glacier Greenland Jakobshavn Jakobshavn isbræ Sea ice The Cryosphere |
genre_facet |
glacier Greenland Jakobshavn Jakobshavn isbræ Sea ice The Cryosphere |
op_source |
The Cryosphere |
op_relation |
Deglaciation of the Norwegian fjords urn:issn:1994-0424 urn:issn:1994-0416 https://hdl.handle.net/1956/17509 https://doi.org/10.5194/tc-2017-151 |
op_rights |
This work is distributed under the Creative Commons Attribution 4.0 License. https://creativecommons.org/licenses/by/4.0/ Copyright Author(s) 2017. |
op_doi |
https://doi.org/10.5194/tc-2017-151 |
_version_ |
1766009516174868480 |