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   Controls on the development of supraglacial floodwater outlets during jökulhlaups
Affiliation   Department of Geography, Staffordshire University, Staffordshire, UK

Abstract

Recent field observations have revealed that jökulhlaups with a near-instantaneous rise to peak discharge can generate temporary hydraulic pressures capable of forcing floodwater through the surface of glaciers. This paper identifies and explains the controls on the development of supraglacial jökulhlaup outlets. Field evidence is presented from two recent Icelandic jökulhlaups, which produced multiple supraglacial outbursts. Subglacial hydraulic pressure increase is identified as the principal control on supraglacial outlet development during jokulhlaups. A near-instantaneous rise to peak subglacial water pressure can produce supraglacial outbursts by hydrofracturing. Pressure increases below the hydrofracturing threshold, but above ice overburden pressure, can back-feed pre-existing drainage, resulting in outbursts from moulins and crevasses. Hydrofracture outbursts can route water to areas of the glacier not normally inundated by floods, and can control the spatial distribution of ice block release.