A full Stokes-flow thermo-mechanical model for firn and ice applied to the Gorshkov crater glacier, Kamchatka

T. ZWINGER, R. GREVE, O. GAGLIARDINI, T. SHIRAIWA and M. LYLY


Abstract

The Gorshkov crater glacier at Ushkovsky volcano, Kamchatka, is characterised by a large aspect ratio and special thermodynamic conditions at the bedrock caused by a locally enhanced and spatially strongly varying geothermal heat flux. Furthermore, large parts of this glacier consist of firn rather than pure ice, which alters the rheological properties (viscosity, compressibility) of the glacier. We present a newly developed, thermo-mechanically coupled, three-dimensional flow model based on the finite-element (FE) package Elmer, and apply it to the Gorshkov crater glacier. By assuming steady-state conditions, the present-day velocity field, temperature field, basal melting rate and age distribution are simulated. We find that flow velocities are generally small (10's of centimeters per year). Horizontal and vertical velocities are of comparable magnitude, which shows that the shallow-ice approximation is not applicable. Owing to the spatially variable volcanic heat flux, the thermal regime at the ice base is cold in the deeper parts of the glacier and temperate in the shallower parts. The measured temperature profile and age horizons at the K2 borehole are reproduced quite well, and remaining discrepancies may be attributed to transient (non-steady-state) conditions. Firn compressibility is identified as a crucial element for the modelling approach.


Annals of Glaciology 45, 29-37 (2007).

 
Last modified: 2008-09-05