|Sensitivity of the Lambert-Amery glacial system to geothermal heat flux|
|investigators:||M. Pittard and others|
|journal:||Annals of Glaciology|
The temperature of an ice sheet is an important control on the deformation of ice, but it also controls basal melt. The geothermal flux (GHF) is a significant thermal boundary condition, and there is large uncertainty in its magnitude and local variation. On the other hand, a balance of heat conduction and advection—the latter dominates in the large—determines the 3D temperature field within the ice. Thus a thermomechanically-important input—it is a velocity boundary condition—is the rate of surface accumulation. The 3D conduction/advection balance determines sliding because the base is weak where it is well-lubricated; this is dominated by basal melt in a cold ice sheet like the Antarctic.
All of this is modeled by PISM—not perfectly but it is all there. However, understanding the sensitivity of this thermomechanical system to it inputs, in a particular glacier, is not easy. This paper studies the Lambert-Amery ice stream/shelf system in East Antarctica by using observed surface velocities and ice thicknesses as the major constraints. The authors conclude that the ice flow is most sensitive to spatial variation in GHF near the ice divides and under the edges of the ice streams. Their control simulation has temperate ice up to 150 m thick, an average basal melt of 1.3 mm per year, and maximum basal melting of about 0.5 m per year.
The core team at UAF continues to support PISM users. The new email for help is firstname.lastname@example.org; it replaces email@example.com. As before, email to this address will be distributed to all the UAF developers, and so it will get the most prompt response year-round.
The 4000 square km ice field in Southeast Alaska is well-known and accessible since its outlets are in the suburbs of the Alaska state capital, Juneau. But climate data for the area are sparse.
Those model runs that agreed well with observations for 1971 to 2010 generated volume and area losses of more than half by 2099. While co-author Regine Hock (UAF) is quoted as saying “The massive icefield that feeds Alaska’s Mendenhall Glacier may be gone by 2200 if warming trend predictions hold true,”, the authors emphasize that spatially-distributed mass balance measurements and improved climate projections that resolve the local temperature and precipitation patterns are essential to solidifying these predictions.
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PISM is jointly developed at the University of Alaska, Fairbanks (UAF) and the Potsdam Institute for Climate Impact Research (PIK). For more about the team see the UAF Developers and PIK Developers pages.
UAF developers, who are in the Glaciers Group at the GI, are supported by NASA's Modeling, Analysis, and Prediction and Cryospheric Sciences Programs (grants NAG5-11371, NNX09AJ38C, NNX13AM16G, NNX16AQ40G, NNX17AG65G) and by NSF grants PLR-1603799 and PLR-1644277.