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

Abstract

ABSTRACT. Surface strain rates around the southeastern dome of Hans Tausen Iskappe in Peary Land, North Greenland (82.5³ N, 27.5³ W), are determined from global positioning system surveys of a strain net. Average longitudinal surface strain rate increases towards the dome, from (1.4 AE 0.2)610^4 a^1 at 5^10 ice thicknesses from the divide to (2.4 AE1.0)610^4 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@H=@ti +0.04 AE 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 byVaughan 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.

Sensitivity, stability and future evolution of the world's northernmost ice cap, Hans Tausen Iskappe (Greenland)

“…8a). These values are in agreement with the surface velocities derived from the mass balance stakes on Hare glacier (Thomsen et al, 1996) and a strain network setup around the central dome (Hvidberg et al, 2001). The InSAR velocities are consistent with the 1947-1978 average surface velocities deduced from aerial photography (Higgins, 1990), although direct comparisons are not always straightforward as the exact location of the aerial measurement is often not clearly stated (see Joughin et al, 2010, for an elaborate discussion).…”

“…Huybrechts, 1996, for a more detailed account). Surface temperature is calculated from the mean annual temperature (TMA) and a warming component related to the superimposed ice formation.…”

“…From 1994 to 1995 a strain network was set up around the central dome, which is sometimes referred to as "the southeastern dome" (Reeh, 1995;Gundestrup et al, 2001;Hvidberg et al, 2001;Jonsson, 2001). A mass balance measurement programme was established between the north dome (1320 m a.s.l.)…”

“…Johnsen et al, 2007), which combined with glacial geological investigations (Landvik et al, 2001) provide constraints on the palaeo-ice-cap evolution. Additionally englacial temperatures (Reeh, 1995;Thomsen et al, 1996) and surface velocities (Reeh, 1995;Hvidberg et al, 2001) were measured and were used for model tuning and validation in this study.…”

Performance and applicability of a 2.5-D ice-flow model in the vicinity of a dome

“…the walls of the tube are vertical), which may depend on the surface geometry. Furthermore, the error in the computation of R is only discussed by Hvidberg et al (1997b), who estimated the error in the calculation of R to be 15 %, and Hvidberg et al (2001) by about 50 %. The method used to measure R is not detailed either, and we doubt that its influence is negligible.…”