The Cryosphere Discuss., 4, 737-766, 2010
www.the-cryosphere-discuss.net/4/737/2010/
doi:10.5194/tcd-4-737-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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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.
The influence of changes in glacier extent and surface elevation on modeled mass balance
F. Paul
Department of Geography, University of Zurich, Zurich, Switzerland

Abstract. Glaciers are widely recognized as unique demonstration objects for climate change impacts, mostly due to the strong change of glacier length in response to small climatic changes. However, glacier mass balance as the direct response to the annual atmospheric conditions can be better interpreted in meteorological terms. When the climatic signal is deduced from long-term mass balance data, changes in glacier geometry (i.e. surface extent and elevation) must be considered as such adjustments form an essential part of the glacier reaction to new climatic conditions. In this study, a set of modeling experiments is performed to assess the influence of changes in glacier geometry on mass balance for constant climatic conditions. The calculations are based on a simplified distributed energy/mass balance model in combination with information on glacier extent and surface elevation for the years 1850 and 1973/1985 for a larger sample of glaciers in the Swiss Alps. The results reveal that about 50–70% of the glacier reaction to climate change (here a one degree increase in temperature) is "hidden" in the geometric adjustment, while only 30–50% can be measured as the long-term mean mass balance. Thereby, changes in glacier extent alone have an even stronger effect, but they are partly compensated for by a lowered surface elevation which gives on average a slightly more negative balance despite an increase of topographic shading. In view of several additional reinforcement feedbacks that are observed in periods of strong glacier decline, it seems that the climatic interpretation of mass balance data is also rather complex.

Citation: Paul, F.: The influence of changes in glacier extent and surface elevation on modeled mass balance, The Cryosphere Discuss., 4, 737-766, doi:10.5194/tcd-4-737-2010, 2010.
 
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