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

Abstract

Marren, P. M. 2002 (March): Glacier margin uctuations , Skaftafellsj ökull, Iceland: implications for sandur evolution. Boreas, Vol. 31, This paper relates recent proglacia l uvial channel change at Skaftafellsj ökull, southeas t Iceland, to glacier margin uctuations. Observation s of the western portion of the proglacia l braided sandur were made annually between 1996 and 2000. Between 1996 and 1998, during a period of glacier advance , the proximal proglacia l outwash surface at the western end of the glacier margin was characterize d 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 abandonmen t of the proximal terrace surface and reorganizatio n of the proglacia l uvial system into a single, entrenche d channel had occurred . Further retreat and incision occurred during 1999-2000. These observation s demonstrat e that glacier retreat at Skaftafellsj ökull is accompanie d by short-lived rapid incision events and terrace formation, separated by long intervals of relatively minor change rather than progressiv e incision over long time periods. The margin of Skaftafellsj ökull is thought to be particularl y sensitive to retreat, as the glacier occupies an overdeepenin g behind the snout and results in lowering of the river's point of exit from the glacier, necessitatin g adjustment of the river's long pro le.

Sedimentology of a sandur formed by multiple jökulhlaups, Kverkfjöll, Iceland

“…A combination of advanced glacier margin positions, favourable to sandur aggradation (Maizels, 1979;Marren 2002b) and high sediment loads during volcanically generated floods appears to have led to significant fan aggradation during the Little Ice Age. These floods may correspond to downstream floods in the Jökulsá á Fjöllum observed during the period 1684-1730 (Thórarinsson, 1950;Ísaksson, 1985), although this suggestion cannot be verified.…”

Skaftafellsjökull, Iceland: glacial geomorphology recording glacier recession since the Little Ice Age

“…At the time of the Thompson and Jones (1986) study the glacier was undergoing a readvance and its 1984 position was the same as that of 1969. More recent snout recession (1996)(1997)(1998)(1999)(2000) has been documented by Marren (2002) and related to proglacial outwash channel changes. He identifies a significant moraine dating to the 1995-1998 readvance, inside of which the snout has thinned and constructed annual recessional push moraines on a foreland that is becoming increasingly flooded by proglacial/supraglacial lakes.…”

“…Maizels, 1993;Marren, 2002Marren, , 2005Price, 1969). Firstly, proglacial outwash accumulated to form sandur fans beyond the Little Ice Age maximum moraines, where meltwater flow was unimpeded by local morainic topography and coalesced with the more extensive jökulhlaup-fed sandur of neighbouring Skeiðarárjökull.…”

A 14,500-year record of landscape change from Okpilak Lake, northeastern Brooks Range, northern Alaska

“…River aggradation could take place in response to a number of environmental and landscape changes. For example, during alpine glacial advances, aggradation can occur as the sediment stored within and beneath glaciers is delivered to fluvial systems (Clague 2000;Marren 2002;Wilkie and Clague 2009). On the other hand, retreating glaciers expose large areas of erodible sediment that when contributed to rivers can cause alluviation and changes in channel planform (Gottesfeld and Johnson -Gottesfeld 1990;Brooks 1994;Clague et al 2003).…”