HR: 0800h
AN: C41A-0060    [Abstracts]
TI: Modeling Future Sea Level Rise From the Melt of Glaciers: Assessment of Uncertainties
AU: * Radic, V
EM: valentina.radic@gi.alaska.edu
AF: Geophysical Institute, University of Alaska, Koyukuk Drive, P.O. Box 757320, Fairbanks, AK 99775-7320, United States
AU: Hock, R
EM: regine.hock@gi.alaska.edu
AF: Geophysical Institute, University of Alaska, Koyukuk Drive, P.O. Box 757320, Fairbanks, AK 99775-7320, United States
AU: Hock, R
EM: regine.hock@gi.alaska.edu
AF: Department of Earth Sciences, Uppsala University, Villavagen 16, Uppsala, 752 36, Sweden
AU: Oerlemans, J
EM: j.oerlemans@phys.uu.nl
AF: Institute for Marine and Atmospheric Research Utrecht, University of Utrecht, Princetonplein 5, Utrecht, 3584, Netherlands
AB: Melting and disintegrating mountain glaciers have been identified as the second largest contributor to rising sea level after thermal expansion of the oceans (e.g., IPCC, 2007; Meier et al., 2007), and Meier et al. (2007) show that melting mountain glaciers are likely to remain the dominant glaciological contributor to rising sea level through the end of the 21st century. Current work will be presented assessing the sources of uncertainty in model-derived estimates of the probable future contributions from glacier wastage to rising sea level. To evaluate uncertainties associated with the choice of glacier mass balance model, we apply three temperature-index and two energy mass balance models to Storglaciären, a small well-measured valley glacier in northern Sweden. The five mass balance models are individually calibrated using ERA-40 reanalysis data from past years. These models are then forced during future years using statistically downscaled regional climate model outputs in order to simulate the future mass balances of Storglaciaren. The cumulative mass balance for the time period 2002 to 2100 AD in response to predicted temperature changes is found to vary between -81 and -92 m for four models but is estimated at -121 m for the fully distributed energy balance model. This demonstrates the sensitivity of the results to the choice of mass balance model. To investigate the sensitivity of projected future changes in the volume of Storglaciaren to the choice of climate model, we used temperature and precipitation outputs from different global climate models (GCMs) to force a temperature-index glacier mass balance model. The results show that the volume-change projections vary by 40% of the initial glacier volume for six different GCMs. The projections showed volume losses by 2100 AD of 50% to 90% of the initial volume of Storglaciaren. Since these volume projections are computed using a volume-area scaling approach, we further investigate the scaling approach relative to the projections obtained using an ice flow model. For this analysis we calibrate a one-dimensional ice- flow model for 6 glaciers with available surface and bed topography maps and sufficiently long records of length fluctuations and mass balance observations. The calibrated model is then forced with a hypothetical mass balance perturbation to produce 100-year volume evolutions. The same mass balance perturbations are used in the scaling approach to derive volume evolutions which are then compared to the modeled simulations of volume change. These comparisons show that the volume-area and volume-length scaling methods underestimate the volume loss by up to 50% and 15%, respectively, relative to the loss predicted by the ice-flow model. These results show that projections of future changes in glacier volume are highly sensitive to the method used to simulate the effects of changes in glacier geometry during the projections.
DE: 0720 Glaciers
DE: 0798 Modeling
SC: Cryosphere [C]
MN: 2007 Fall Meeting