HR: 1340h
AN: C23A-1155    [Abstracts]
TI: A Greenland Ice Sheet Surface Mass Balance Model Designed for Coupling With a GCM.
AU: * Bougamont, M
EM: m.bougamont@bristol.ac.uk
AF: University of Bristol, School of Geographical Sciences, University Road, Bristol, BS8 1SS United Kingdom
AU: Bamber, J
C23A-1155 AF: University of Bristol, School of Geographical Sciences, University Road, Bristol, BS8 1SS United Kingdom
AU: Greuell, W
C23A-1155 AF: Institute for Marine and Atmospheric Research Utrecht (IMAU), Princetonplein 5, Utrecht, 3584 Netherlands
AU: Gladstone, R
C23A-1155 AF: University of Bristol, School of Geographical Sciences, University Road, Bristol, BS8 1SS United Kingdom
AB: In future climate warming scenarios, the Greenland Ice Sheet (GrIS) may halve in volume within as little as 500 years. Although uncertainties remain in estimates of the response of the ice sheet, the freshwater flux into the North Atlantic could increase by 0.1 Sv from the present-day value of ~0.018 Sv. The increase of fresh water input as well as the ongoing reduction of sea ice extent may perturb the thermohaline circulation in the North Atlantic, and consequently the global climate. As part of the UK NERC, RAPID Climate Change programme, we are investigating the role of the cryosphere in modulating the thermohaline circulation in the North Atlantic, and examining the feedbacks between land and sea ice and the rest of the climate system. To achieve this, a suite of numerical models have been coupled, including an atmosphere-ocean GCM (based on the UK Hadley Centre model: HadCM3), and a surface mass balance and thermo-mechanical model for the GrIS. Here, we present the surface mass balance model and the results of validating it against in-situ observations. In addition to computing the energy balance at the surface, the model, modified from previous work by Greuell and Konzelmann (1994), includes subsurface and snow metamorphism processes within the upper ~30m of firn. It was tested using data from two automatic weather stations located along the K-transect (in the southwest Greenland ablation zone), and the model output was compared with four years of mass balance observations. In addition, the model was forced with 10 years ERA-40 climatology, and run on a 20km grid with present-day surface topography. The ability of the model to capture the inter-annual and spatial variability of the mass balance was assessed for the whole ice sheet using the results of these simulations. The ability of the model to adequately reproduce the pattern of albedo and melt extent (compared with satellite-derived estimates) is presented along with the mass balance comparisons at two automatic weather station (AWS) sites along the K-transect. In addition, the model sensitivity to errors in AWS input measurements and to uncertainties in tuneable parameters is assessed. Preliminary results suggest that the model is most sensitive to uncertainties in incoming longwave radiation and relative humidity.
DE: 0726 Ice sheets
DE: 0762 Mass balance (1218, 1223)
DE: 0764 Energy balance
DE: 0798 Modeling
DE: 1605 Abrupt/rapid climate change (4901, 8408)
SC: Cryosphere [C]
MN: Fall Meeting 2005