Ice caps are drained by fast-flowing glaciers which can reach move by up to several km per year, but which take up only a very small percentage of the ice cap’s perimeter. Most of these glaciers flow at a relatively uniform speed that only changes gradually, but some exhibit rather more unruly behaviour. Known as “surge-type” glaciers, these glaciers flow very slowly for long periods of time, building up mass, before undergoing the eponymous surge and reaching speeds up to dozens of metres per day for a short while.
Surging glaciers are among the greatest mysteries in glaciology. Very little is known about what causes a glacier to be surge-type, and what causes the beginning and end of a surge. Thorben Dunse of the University of Oslo and his colleagues try to fit a numerical model to the Austfonna ice cap in Svalbard, where several surge-type glaciers are located, in order to identify the parameters that govern oscillatory flow of these glaciers. Here, it is thought that surging occurs due to the glaciers sliding over their bed when the ice at the bottom of the glacier reaches the melting point and water lubricates the ice-bed interface. They find that a relatively sudden transition between “no-sliding” and sliding conditions is required for surging to be a feasible option for glaciers.
Dunse and his team also found that even very small changes in some parameters produced a large change in the ice cap’s size, so it is crucial to understand and monitor these surging glaciers so that their contribution to global sea-level rise can be adequately quantified.
Ice2sea Work Package WP3.4
Dunse, T., R. Greve, T. V. Schule, and J. O. Hagen (2011), Permanent fast flow versus cyclic surge behaviour: numerical simulations of the Austfonna ice cap, Svalbard, Journal of Glaciology, 57(202), 247-259.