Simulated retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry

Rapid retreat of Greenland's marine-terminating glaciers coincides with regional warming trends, which have broadly been used to explain these rapid changes. However, outlet glaciers within similar climate regimes experience widely contrasting retreat patterns, suggesting that the local fjord g...

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Bibliographic Details
Published in:The Cryosphere
Main Authors: N. Steiger, K. H. Nisancioglu, H. Åkesson, B. de Fleurian, F. M. Nick
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2018
Subjects:
geo
Online Access:https://doi.org/10.5194/tc-12-2249-2018
https://www.the-cryosphere.net/12/2249/2018/tc-12-2249-2018.pdf
https://doaj.org/article/3c9275f16bd243419250f50ad74bb63f
Description
Summary:Rapid retreat of Greenland's marine-terminating glaciers coincides with regional warming trends, which have broadly been used to explain these rapid changes. However, outlet glaciers within similar climate regimes experience widely contrasting retreat patterns, suggesting that the local fjord geometry could be an important additional factor. To assess the relative role of climate and fjord geometry, we use the retreat history of Jakobshavn Isbræ, West Greenland, since the Little Ice Age (LIA) maximum in 1850 as a baseline for the parameterization of a depth- and width-integrated ice flow model. The impact of fjord geometry is isolated by using a linearly increasing climate forcing since the LIA and testing a range of simplified geometries.We find that the total length of retreat is determined by external factors – such as hydrofracturing, submarine melt and buttressing by sea ice – whereas the retreat pattern is governed by the fjord geometry. Narrow and shallow areas provide pinning points and cause delayed but rapid retreat without additional climate warming, after decades of grounding line stability. We suggest that these geometric pinning points may be used to locate potential sites for moraine formation and to predict the long-term response of the glacier. As a consequence, to assess the impact of climate on the retreat history of a glacier, each system has to be analyzed with knowledge of its historic retreat and the local fjord geometry.