The Cryosphere www.the-cryosphere.net 1994-0416 1994-0424 3 2 2009 10.5194/tc-3-217-2009 http://www.the-cryosphere.net/3/217/2009/ http://www.the-cryosphere.net/3/217/2009/tc-3-217-2009.html http://www.the-cryosphere.net/3/217/2009/tc-3-217-2009.pdf 217 229 2009-11-19 Diagnostic and prognostic simulations with a full Stokes model accounting for superimposed ice of Midtre Lovénbreen, Svalbard T. Zwinger thomas.zwinger@csc.fi J. C. Moore CSC – IT Center for Science Ltd., Espoo, Finland Arctic Centre, University of Lapland, Rovaniemi, Finland Thule Institute, University of Oulu, Oulu, Finland College of Global Change and Earth System Science, Beijing Normal University, China We present steady state (diagnostic) and transient (prognostic) simulations of Midtre Lovénbreen, Svalbard performed with the thermo-mechanically coupled full-Stokes code Elmer. This glacier has an extensive data set of geophysical measurements available spanning several decades, that allow for constraints on model descriptions. Consistent with this data set, we included a simple model accounting for the formation of superimposed ice. Diagnostic results indicated that a dynamic adaptation of the free surface is necessary, to prevent non-physically high velocities in a region of under determined bedrock depths. Observations from ground penetrating radar of the basal thermal state agree very well with model predictions, while the dip angles of isochrones in radar data also match reasonably well with modelled isochrones, despite the numerical deficiencies of estimating ages with a steady state model. <br><br> Prognostic runs for 53 years, using a constant accumulation/ablation pattern starting from the steady state solution obtained from the configuration of the 1977 DEM show that: 1 the unrealistic velocities in the under determined parts of the DEM quickly damp out; 2 the free surface evolution matches well measured elevation changes; 3 the retreat of the glacier under this scenario continues with the glacier tongue in a projection to 2030 being situated ≈500 m behind the position in 1977. Barrand, N E., Murray, T., James, T D., Barr, S L., and Mills, J P.: Optimising photogrammetric glacier DEMs for volume change assessment using laser-scanning derived ground control points, J. 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Glaciol., 48(163), 545–551, 2002. Wadham, J., Kohler, J., Hubbard, A., Nuttall, A.-M., and Rippin, D.: Superimposed ice regime of a high arctic glacier inferred using GPR, flow modelling, and ice-cores, J. Geophys. Res., 111, F01007, doi:10.1029/2004JF000144, 2006. Wright, A P., Wadham, J L., Siegert, M J., Luckman, A., and Kohler, J.: Modelling the Impact of Superimposed Ice on the Mass Balance of an Arctic Glacier under Scenarios of Future Climate Change, Ann. Glaciol., 42, 277–283, 2005. Wright, A P., Wadham, J L., Siegert, M J., Luckman, A., Kohler, J., and Nuttall, A M.: Modeling the refreezing of meltwater as superimposed ice on a high Arctic glacier: A comparison of approaches, J. Geophys. Res., 112, F04016, doi:10.1029/2007JF000818, 2007. Zwinger, T., Greve, R., Gagliardini, O., Shiraiwa, T., and Lyly, M.: A full Stokes-flow thermo-mechanical model for firn and ice applied to the Gorshkov crater glacier, Kamchatka, Ann. Glaciol., 45, 29–37, 2007.