Distributed energy balance modeling of South Cascade Glacier, Washington and assessment of model uncertainty

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Read Full Article (file size: 1233174 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, F02019, doi:10.1029/2007JF000850, 2008 Distributed energy balance modeling of South Cascade Glacier, Washington and assessment of model uncertainty Faron S. Anslow Department of Geosciences, Oregon State University, Corvallis, Oregon, USA Steven Hostetler United States Geological Survey, Department of Geosciences, Oregon State University, Corvallis, Oregon, USA William R. Bidlake United States, Geological Survey, Washington Water Science Center, Tacoma, Washington, USA Peter U. Clark Department of Geosciences, Oregon State University, Corvallis, Oregon, USA Abstract We have developed a physically based, distributed surface energy balance model to simulate glacier mass balance under meteorological and climatological forcing. Here we apply the model to estimate summer ablation on South Cascade Glacier, Washington, for the 2004 and 2005 mass balance seasons. To arrive at optimal mass balance simulations, we investigate and quantify model uncertainty associated with selecting from a range of physical parameter values that are not commonly measured in glaciological mass balance field studies. We optimize the performance of the model by varying values for atmospheric transmissivity, the albedo of surrounding topography, precipitation-elevation lapse rate, surface roughness for turbulent exchange of momentum, and snow albedo aging coefficient. Of these the snow aging parameter and precipitation lapse rates have the greatest influence on the modeled ablation. We examined model sensitivity to varying parameters by performing an additional 10³ realizations with parameters randomly chosen over a ±5% range centered about the optimum values. The best fit suite of model parameters yielded a net balance of −1.69 ± 0.38 m water equivalent (WE) for the 2004 water year and −2.10 ± 0.30 m WE up to 11 September 2005. The 2004 result is within 3% of the measured value. These simulations account for 91% and 93% of the variance in measured ablation for the respective years. Received 18 June 2007; accepted 20 February 2008; published 31 May 2008. Keywords: glaciology; modeling; climate. Index Terms: 0764 Cryosphere: Energy balance; 0798 Cryosphere: Modeling; 0762 Cryosphere: Mass balance (1218, 1223); 1873 Hydrology: Uncertainty assessment (3275). Read Full Article (file size: 1233174 bytes) Cited by Citation: Anslow, F. S., S. Hostetler, W. R. Bidlake, and P. U. Clark (2008), Distributed energy balance modeling of South Cascade Glacier, Washington and assessment of model uncertainty, J. Geophys. Res., 113, F02019, doi:10.1029/2007JF000850. Copyright 2008 by the American Geophysical Union.

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