ARCUS | Arctic Research Consortium of the United States

6th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Matthew J. Roberts
Authors   Matthew J. Roberts, A.J. Russell, F.S. Tweed, and Ó. Knudsen
Category   Physical Science
Title   Rapid sediment entrainment and englacial deposition during jökulhlaups
Affiliation   Department of Geography, Staffordshire University, Staffordshire, UK

Abstract

Englacial water flow is a commonly invoked hypothesis to account for the presence of water-worked sediment at high elevations within glaciers (e.g. Kirkbride and Spedding, 1996; Naslund and Hassinen, 1996; Glasser and others, 1999). However, subscribers to this hypothesis lack evidence for sediment entrainment by englacial water flow. Here we present direct field evidence for supraglacial outbursts and rapid englacial fluvial sediment deposition during two recent Icelandic jökulhlaups. Both of these jökulhlaups generated basal water pressures in excess of ice overburden, which fractured overlying ice, allowing sediment to be fluvially emplaced at high elevations within each glacier. Although these jökulhlaups were hydrologically extreme, similar short-term rates of increase in basal hydraulic pressure may be generated during lower-magnitude hydrological events. The recent Icelandic jökulhlaups therefore provide us with a direct insight into rapid sediment entrainment and englacial deposition, a process that could be applied to other high-water-pressure events.