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Abstract
AbstractThe Gorshkov crater glacier at Ushkovsky volcano, Kamchatka, is characterized by a large aspect ratio and special thermodynamic conditions at the bedrock caused by a locally enhanced and spatially varying geothermal heat flux. Furthermore, large parts of this glacier consist of firn rather than pure ice, which alters the rheological properties (such as viscosity and compressibility) of the glacier. We present a newly developed, thermo-mechanically coupled, three-dimensional flow model based on the finite-element (FE) modeling software 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 (tens 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 modeling approach.
Highlights
IntroductionGlaciers which develop in volcano craters are unique systems because of their particular morphologies (large aspect ratio) and thermodynamic conditions (large geothermal heat flux)
We present a newly developed, thermo-mechanically coupled, three-dimensional flow model based on the finite-element (FE) modeling software Elmer, and apply it to the Gorshkov crater glacier
Glaciers which develop in volcano craters are unique systems because of their particular morphologies and thermodynamic conditions
Summary
Glaciers which develop in volcano craters are unique systems because of their particular morphologies (large aspect ratio) and thermodynamic conditions (large geothermal heat flux). The glacier is situated in the summit caldera of Ushkovsky volcano and fills the concave bed of Gorshkov crater to a maximum depth of 240 m. The glacier surface is gently inclined towards the northern crater rim, where the ice flows out of the crater and down the slope of the volcano. The geothermal heat flux at the crater rim is estimated to be as large as 10 W m–2 based on direct measurements (Murav’yev and Salamatin, 1989), whereas the temperature profile of the K2 borehole close to the deepest point of the glacier indicates a far smaller heat flux of only 0.12 W m–2 at this position (Shiraiwa and others, 2001)
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