Glacier margin fluctuations, Skaftafellsjökull, Iceland: implications for sandur evolution

Abstract

This paper relates recent proglacial fluvial channel change at Skaftafellsjökull, southeast Iceland, to glacier margin fluctuations. Observations of the western portion of the proglacial braided sandur were made annually between 1996 and 2000. Between 1996 and 1998, during a period of glacier advance, the proximal proglacial outwash surface at the western end of the glacier margin was characterized by a complex braided channel pattern active over the entire sandur surface. Retreat of the glacier margin since 1998 led to rapid incision, so that by 1999 abandonment of the proximal terrace surface and reorganization of the proglacial fluvial system into a single, entrenched channel had occurred. Further retreat and incision occurred during 1999–2000. These observations demonstrate that glacier retreat at Skaftafellsjökull is accompanied by short‐lived rapid incision events and terrace formation, separated by long intervals of relatively minor change rather than progressive incision over long time periods. The margin of Skaftafellsjökull is thought to be particularly sensitive to retreat, as the glacier occupies an overdeepening behind the snout and results in lowering of the river's point of exit from the glacier, necessitating adjustment of the river's long profile.