Modelling historical and recent mass loss of McCall Glacier, Alaska, USA C. Delcourt1, F. Pattyn1, and M. Nolan2 1Laboratoire de Glaciologie, Département des Sciences de la Terre et de l'Environnement, Université Libre de Bruxelles, CP 160/03, Avenue F.D. Roosevelt 50, 1050 Brussels, Belgium 2Institute of Northern Engineering, 455 Duckering Bldg, University of Alaska Fairbanks, AK, USA
Abstract. Volume loss of valley glaciers is now considered to be a significant
contribution to sea level rise. Understanding and identifying the processes
involved in accelerated mass loss are necessary to determine their impact on
the global system. Here we present results from a series of model experiments
with a higher-order thermomechanically coupled flowline model
(Pattyn, 2002). Boundary conditions to the model are parameterizations of
surface mass balance, geothermal heating, observed surface and 10 m ice depth
temperatures. The time-dependent experiments aim at simulating the glacier
retreat from its LIA expansion to present according to different scenarios
and model parameters. Model output was validated against measurements of ice
velocity, ice surface elevation and terminus position at different stages.
Results demonstrate that a key factor in determining the glacier retreat
history is the importance of internal accumulation (>50%) in the total
mass balance. The persistence of a basal temperate zone characteristic for
this polythermal glacier depends largely on its contribution. Accelerated
glacier retreat since the early nineties seems directly related to the
increase in ELA and the sudden reduction in AAR due to the fact that a large
lower elevation cirque – previously an important accumulation area – became
part of the ablation zone.
Citation: Delcourt, C., Pattyn, F., and Nolan, M.: Modelling historical and recent mass loss of McCall Glacier, Alaska, USA, The Cryosphere, 2, 23-31, doi:10.5194/tc-2-23-2008, 2008.