Diagnostic and prognostic simulations with a full Stokes model accounting for superimposed ice of Midtre Lovénbreen, Svalbard

Abstract. We present steady state (diagnostic) and transient (prognostic) simulations of Midtre Lovenbreen, 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. 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.

[1]  W. G. Rees,et al.  Mass balance and dynamics of a valley glacier measured by high-resolution LiDAR , 2007, Polar Record.

[2]  L. Franca,et al.  Stabilized finite element methods. II: The incompressible Navier-Stokes equations , 1992 .

[3]  W. Paterson.  Hydraulics of Glaciers , 1994 .

[4]  J. Hagen,et al.  On the Net Mass Balance of the Glaciers and Ice Caps in Svalbard, Norwegian Arctic , 2003 .

[5]  R. Armstrong,et al.  The Physics of Glaciers , 1981 .

[6]  P. Råback,et al.  Correction to “Finite‐element modeling of subglacial cavities and related friction law” , 2007 .

[7]  H. Blatter.  Velocity and stress fields in grounded glaciers: a simple algorithm for including deviatoric stress gradients , 1995 .

[8]  Svein-Erik Hamran,et al.  The thermal regime of sub-polar glaciers mapped by multi-frequency radio-echo sounding , 1996 .

[9]  Anne-Marie Nuttall,et al.  Modeling the refreezing of meltwater as superimposed ice on a high Arctic glacier: A comparison of approaches , 2007 .

[10]  J. Moore,et al.  Changes in geometry and subglacial drainage of Midre Lovénbreen, Svalbard, determined from digital elevation models , 2003 .

[11]  Jacek Jania,et al.  High-resolution hydrothermal structure of Hansbreen, Spitsbergen, mapped by ground-penetrating radar , 1999 .

[12]  L. Franca,et al.  Stabilized Finite Element Methods , 1993 .

[13]  Uwe Nixdorf,et al.  Identifying isochrones in GPR profiles from DEP-based forward modeling , 2003, Annals of Glaciology.

[14]  Veijo A. Pohjola,et al.  Spatial and temporal variability of snow accumulation using ground-penetrating radar and ice cores on a Svalbard glacier , 2002 .

[15]  Alun Hubbard,et al.  Superimposed ice regime of a high Arctic glacier inferred using ground-penetrating radar, flow modeling, and ice cores , 2006 .

[16]  T. Shiraiwa,et al.  A full Stokes-flow thermo-mechanical model for firn and ice applied to the Gorshkov crater glacier, Kamchatka , 2007, Annals of Glaciology.

[17]  N. Barrand,et al.  Acceleration in thinning rate on western Svalbard glaciers , 2007 .

[18]  Anne-Marie Nuttall,et al.  Multiphase formation of superimposed ice during a mass-balance year at a maritime high-Arctic glacier , 2002, Journal of Glaciology.

[19]  Endre Süli,et al.  DISCONTINUOUS GALERKIN METHODS FOR FIRST-ORDER HYPERBOLIC PROBLEMS , 2004 .

[20]  Alun Hubbard,et al.  Evidence for subglacial ponding across Taylor Glacier, Dry Valleys, Antarctica , 2004, Annals of Glaciology.

[21]  N. Barrand,et al.  Optimizing photogrammetric DEMs for glacier volume change assessment using laser-scanning derived ground-control points , 2009, Journal of Glaciology.

[22]  J. Moore,et al.  Inferences from stable water isotopes on the Holocene evolution of Scharffenbergbotnen blue-ice area, East Antarctica , 2007 .

[23]  T. Zwinger,et al.  Marine ice sheet dynamics: Hysteresis and neutral equilibrium , 2009 .

[24]  Bernard Lefauconnier,et al.  Glacier balance trends in the Kongsfjorden area, western Spitsbergen, Svalbard, in relation to the climate , 1999 .

[25]  A. Luckman,et al.  Modelling the impact of superimposed ice on the mass balance of an Arctic glacier under scenarios of future climate change , 2005, Annals of Glaciology.