Glacier surging as a control on the development of proglacial, fluvial landforms and deposits, Skeiðarársandur, Iceland

Glacier-hydrological processes are one of the main factors controlling proglacial fluvial systems. It has been proposed that where jökulhlaups occur they play a dominant role in the evolution of proglacial outwash plains. However, extraordinary meltwater and sediment discharge associated with glacier surging can also play a crucial role in the proglacial system. The interplay of surge-related and jökulhlaup floods has been investigated at Skeiðarárjökull, a jökulhlaup type-site where surging is also known to occur, allowing the geomorphological and sedimentological effects of these events to be differentiated. Skeiðarársandur contains a spectacular assemblage of landforms and deposits associated with the 1991 surge of Skeiðarárjökull. The impact of the 1991 surge was felt mainly on the western half of the glacier where the ice advanced up to 1 km between September and November. The surge limit is marked by a push-moraine complex up to 5 m in height and 10 m in breadth. Proglacial fluvial sediments were deposited as a series of outwash fans adjacent to the glacier, up to 400 m in diameter, as the glacier advanced during the surge. Glaciotectonic structures associated with ice pushing inter-finger with undisturbed proglacial fluvial fan sediments, constraining timing of deposition of proglacial fans to the period during and immediately following the glacier surge. The study of landforms and sedimentary successions associated with the 1991 surge provides an excellent modern analogue for larger-scale push moraines and proglacial fans on Skeiðarársandur, which are related to similar processes. Surge-related outflows operating over timescales of months–years, together with jökulhlaup flows play a major role in the creation of distinctive proglacial fluvial landforms and deposits. Examination of the sedimentary and landform records of areas presently subject to surging will allow the development of models which can be used to differentiate glacier surging from rapid glacier response to abrupt climate change.