Ice-divide flow at Hans Tausen Iskappe, North Greenland, from surface movement data

Abstract

Surface strain rates around the southeastern dome of Hans Tausen Iskappe in Peary Land, North Greenland (82.5°N, 27.5°W), are determined from global positioning system surveys of a strain net. Average longitudinal surface strain rate increases towards the dome, from (1.4 ± 0.2) x 10-4 a-1 at 5-10 ice thicknesses from the divide to (2.4 ± 1.0) x 10-4 a-1 within 1 ice thickness from the divide. Analysis of the data shows that the ice cap is presently building up within the strain net with an average rate of (∂H/∂t) = +0.04 ± 0.02 m a-1. Assuming a uniform thickening, the shape factor of the horizontal velocity (the ratio between the vertically averaged horizontal velocity and the horizontal surface velocity) decreases towards the dome, from 0.9 at a distance of 10 ice thicknesses from the dome to 0.5 at the dome based on application of the continuity equation. Our results indicate that a region with anomalous flow is formed around the dome, supporting recent indications reported by Vaughan and others (1999). It is not possible from our data to constrain parameters of the flow law, because there is no independent estimate of the significant present thickening of the central part of the ice cap and its pattern around the dome.