1Arctic Centre, University of Lapland, Rovaniemi, Finland
2VAW, Eidgenossische Technische Hochschule Zürich, ETHZ, Switzerland
3Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
4CSC – IT Center for Science Ltd., Espoo, Finland
5Gamma Remote Sensing and Consulting AG, Gümligen, Switzerland
6Danish Meteorological Institute, Copenhagen, Denmark
7Department of Earth Sciences, Uppsala University, Uppsala, Sweden
8College of Global Change and Earth System Science & State Key Laboratory of Remote Sensing Science, Beijing Normal University, Beijing, China
Received: 08 Nov 2013 – Discussion started: 09 Dec 2013
Abstract. The outlet glacier of Basin 3 (B3) of Austfonna ice cap, Svalbard, is one of the fastest outlet glaciers in Svalbard, and shows dramatic changes since 1995. In addition to previously observed seasonal summer speed-up associated with the melt season, the winter speed of B3 has accelerated approximately fivefold since 1995. We use the Elmer/Ice full-Stokes model for ice dynamics to infer spatial distributions of basal drag for the winter seasons of 1995, 2008 and 2011. This "inverse" method is based on minimising discrepancy between modelled and observed surface velocities, using satellite remotely sensed velocity fields. We generate steady-state temperature distributions for 1995 and 2011. Frictional heating caused by basal sliding contributes significantly to basal temperatures of the B3 outlet glacier, with heat advection (a longer-timescale process than frictional heating) also being important in the steady state.
Revised: 15 Jun 2014 – Accepted: 17 Jun 2014 – Published: 04 Aug 2014
We present a sensitivity experiment consisting of transient simulations under present-day forcing to demonstrate that using a temporally fixed basal drag field obtained through inversion can lead to thickness change errors of the order of 2 m year−1. Hence it is essential to incorporate the evolution of basal processes in future projections of the evolution of B3. Informed by a combination of our inverse method results and previous studies, we hypothesise a system of processes and feedbacks involving till deformation and basal hydrology to explain both the seasonal accelerations (short residence time pooling of meltwater at the ice–till interface) and the ongoing interannual speed-up (gradual penetration of water into the till, reducing till strength).
Gladstone, R., Schäfer, M., Zwinger, T., Gong, Y., Strozzi, T., Mottram, R., Boberg, F., and Moore, J. C.: Importance of basal processes in simulations of a surging Svalbard outlet glacier, The Cryosphere, 8, 1393-1405, doi:10.5194/tc-8-1393-2014, 2014.