Evolution of a Sandur : sixty years of change, Skeiºarársandur, Iceland

Abstract

Glaciers are a major component of the global climate system, adjusting to changes in climate over a range of timescales. Knowledge of the dynamics of contemporary glaciated landscapes will allow accurate reconstruction of glacier margin fluctuations within the landform and sedimentary record as well as predictions of the response of ice-marginal landscapes to future glacier margin fluctuations. Existing models of ice-marginal, proglacial landscape evolution focus primarily on landforms generated in response to single, relatively short-lived, highmagnitude large-scale events such as glacier surges or glacier outburst floods (jökulhlaups). Observations of these events have frequently been restricted to short time windows (days to several years) or inferred from stratigraphic sections and are therefore subject to misinterpretation. Relatively little research has been undertaken on the development of icemarginal and proglacial landscapes over decadal time-scales (101-102 years). This study examines the controls on the evolution of the ice-marginal landscape of Skeiðarárjökull over a decadal timescale. Skeiðarárjökull is a temperate, surge-type, piedmont outlet glacier located in south-east Iceland. Skeiðarárjökull, and its outwash plain Skeiðarársandur, have been subject to numerous surges and jökulhlaups and post-depositional modification due to the melt out of buried glacier ice, providing a valuable modern process-form analogue for landscape evolution at Pleistocene ice sheet margins. Digital Elevation Models (DEMs) were extracted from the aerial photographs taken at intervals over the past six decades to quantify the rate of landscape change over decadal time periods. This data, when combined with observations from aerial photographs of numerous suites of large-scale sub- and englacial features exposed by the glacier's recession permits models of the long-term response of proglacial regions to surges, jökulhlaups and glacier margin recession to be tested. This study developed a holistic model to describe the interdependence of glacier margin fluctuations, jökulhlaups and post-depositional modification and their impact on sandur evolution.