The Cryosphere Discuss., 7, 2761-2800, 2013
© Author(s) 2013. This work is distributed
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This discussion paper has been under review for the journal The Cryosphere (TC). Please refer to the corresponding final paper in TC.
Feedbacks and mechanisms affecting the global sensitivity of glaciers to climate change
B. Marzeion1, A. H. Jarosch2, and J. M. Gregory3
1Center of Climate and Cryopshere, Institute of Meteorology and Geophysics, University of Innsbruck, Austria
2Icelandic Meteorological Office, Reykjavík, Iceland
3NCAS-Climate, University of Reading, Reading, and Met Office Hadley Centre, Exeter, UK

Abstract. Mass loss by glaciers has been an important contributor to sea level rise in the past and is projected to contribute a substantial fraction of total sea level rise during the 21st century. Here, we use a model of the world's glaciers in order to quantify equilibrium sensitivities of global glacier mass to climate change, and to investigate the role of changes in glacier hypsometry for long term mass changes. We find that 21st century glacier mass loss to a~large degree is governed by the glaciers responding to 20th century climate change. This limits the influence of 21st century climate change on glacier mass loss, and explains why there are relatively small differences in glacier mass loss under greatly different scenarios of climate change. Because of the geographic distribution of glaciers, both temperature and precipitation anomalies experienced by glaciers are vastly stronger than on global average. The projected increase in precipitation partly compensates for the mass loss caused by warming, but this compensation is negligible at higher temperature anomalies since an increasing fraction of precipitation at the glacier sites it liquid. Loss of low-lying glacier area, and more importantly, eventual complete disappearance of glaciers, strongly limit the projected sea level contribution from glaciers in coming centuries. The adjustment of glacier hypsometry to changes in the forcing reduces the sensitivity of global glacier mass to changes in global mean temperature by a factor of two to three. This result is a second reason for the relatively weak dependence of glacier mass loss on future climate scenario, and helps explain why glacier mass loss in the first half of the 20th century was of the same order of magnitude as in the second half of the 20th century, even though the rate of warming was considerably smaller.

Citation: Marzeion, B., Jarosch, A. H., and Gregory, J. M.: Feedbacks and mechanisms affecting the global sensitivity of glaciers to climate change, The Cryosphere Discuss., 7, 2761-2800, doi:10.5194/tcd-7-2761-2013, 2013.
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