Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 11, 281-302, 2017
http://www.the-cryosphere.net/11/281/2017/
doi:10.5194/tc-11-281-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
27 Jan 2017
Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change
Henning Åkesson1,2, Kerim H. Nisancioglu1,3, Rianne H. Giesen4, and Mathieu Morlighem2 1Department of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, Allégaten 70, 5007 Bergen, Norway
2University of California, Irvine, Department of Earth System Science, 3218 Croul Hall, Irvine, CA, 92697-3100, USA
3Centre for Earth Evolution and Dynamics, University of Oslo, Po. Box 1028 Blindern, 0315 Oslo, Norway
4Institute for Marine and Atmospheric research, Utrecht University, P.O. Box 80005, 3508 TA Utrecht, the Netherlands
Abstract. Understanding of long-term dynamics of glaciers and ice caps is vital to assess their recent and future changes, yet few long-term reconstructions using ice flow models exist. Here we present simulations of the maritime Hardangerjøkulen ice cap in Norway from the mid-Holocene through the Little Ice Age (LIA) to the present day, using a numerical ice flow model combined with glacier and climate reconstructions.

In our simulation, under a linear climate forcing, we find that Hardangerjøkulen grows from ice-free conditions in the mid-Holocene to its maximum extent during the LIA in a nonlinear, spatially asynchronous fashion. During its fastest stage of growth (2300–1300 BP), the ice cap triples its volume in less than 1000 years. The modeled ice cap extent and outlet glacier length changes from the LIA until today agree well with available observations.

Volume and area for Hardangerjøkulen and several of its outlet glaciers vary out-of-phase for several centuries during the Holocene. This volume–area disequilibrium varies in time and from one outlet glacier to the next, illustrating that linear relations between ice extent, volume and glacier proxy records, as generally used in paleoclimatic reconstructions, have only limited validity.

We also show that the present-day ice cap is highly sensitive to surface mass balance changes and that the effect of the ice cap hypsometry on the mass balance–altitude feedback is essential to this sensitivity. A mass balance shift by +0.5 m w.e. relative to the mass balance from the last decades almost doubles ice volume, while a decrease of 0.2 m w.e. or more induces a strong mass balance–altitude feedback and makes Hardangerjøkulen disappear entirely. Furthermore, once disappeared, an additional +0.1 m w.e. relative to the present mass balance is needed to regrow the ice cap to its present-day extent. We expect that other ice caps with comparable geometry in, for example, Norway, Iceland, Patagonia and peripheral Greenland may behave similarly, making them particularly vulnerable to climate change.


Citation: Åkesson, H., Nisancioglu, K. H., Giesen, R. H., and Morlighem, M.: Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change, The Cryosphere, 11, 281-302, doi:10.5194/tc-11-281-2017, 2017.
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We present simulations of the history of Hardangerjøkulen ice cap in southern Norway using a dynamical ice sheet model. From mid-Holocene ice-free conditions 4000 years ago, Hardangerjøkulen grows nonlinearly in response to a linear climate forcing, reaching maximum extent during the Little Ice Age (~ 1750 AD). The ice cap exhibits spatially asymmetric growth and retreat and is highly sensitive to climate change. Our results call for reassessment of glacier reconstructions from proxy records.
We present simulations of the history of Hardangerjøkulen ice cap in southern Norway using a...
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