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A large-scale numerical model for computing isochrone geometry


Hindmarsh, Richard C A; Leysinger Vieli, Gwendolyn; Parrenin, Frédéric (2009). A large-scale numerical model for computing isochrone geometry. Annals of Glaciology, 50(51):130-140.

Abstract

A finite-difference model for the calculation of radar layer geometries in large ice masses is presented. Balance velocities are used as coefficients in the age equation and in the heat equation. Solution of the heat equation allows prediction of sliding areas and computation of basal melt rates. Vertical distributions of velocity are parameterized using shape functions. These can be set uniformly, or allowed to vary in space according to the distribution of sliding. The vertical coordinate can either be uniformly distributed within the thickness of the ice, or be uniformly distributed within the flux. The finite-difference scheme results in a large set of linear equations. These are solved using a nested factorization preconditioned conjugate gradient scheme. The convergence properties of some other iteration solution schemes are studied. The output is computations of age and temperature assuming steady state, in large ice masses at high resolution. Age calculations are used to generate isochrones which show the best fit to observed layers. Comparisons with analytical solutions are made, and the influence of the order of the finite-difference approximation and the choice of vertical coordinate on solution accuracy is considered.

Abstract

A finite-difference model for the calculation of radar layer geometries in large ice masses is presented. Balance velocities are used as coefficients in the age equation and in the heat equation. Solution of the heat equation allows prediction of sliding areas and computation of basal melt rates. Vertical distributions of velocity are parameterized using shape functions. These can be set uniformly, or allowed to vary in space according to the distribution of sliding. The vertical coordinate can either be uniformly distributed within the thickness of the ice, or be uniformly distributed within the flux. The finite-difference scheme results in a large set of linear equations. These are solved using a nested factorization preconditioned conjugate gradient scheme. The convergence properties of some other iteration solution schemes are studied. The output is computations of age and temperature assuming steady state, in large ice masses at high resolution. Age calculations are used to generate isochrones which show the best fit to observed layers. Comparisons with analytical solutions are made, and the influence of the order of the finite-difference approximation and the choice of vertical coordinate on solution accuracy is considered.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Date:2009
Deposited On:15 Sep 2017 13:38
Last Modified:18 Feb 2018 01:07
Publisher:International Glaciological Society
ISSN:0260-3055
OA Status:Gold
Free access at:Official URL. An embargo period may apply.
Publisher DOI:https://doi.org/10.3189/172756409789097450
Related URLs:http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.430.901&rep=rep1&type=pdf

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