The glacial landsystem of Hoffellsjokull, SE Iceland: contrasting geomorphological signatures of active temperate glacier recession driven by ice lobe and bed morphology

Abstract

A 1:14 500 scale glacial geomorphology and surficial geology map of the foreland of Hoffellsjökull, southeast Iceland is used to assess the glacial landsystem signature of the contrasting glacier-climate interactions of two separate flow lobes within one outlet glacier. This constitutes a valuable modern analogue for employing glacial geomorphological signatures as palaeoclimate indicators in ancient deglaciated terrains. The landsystem signatures of the glacier’s two flow lobes, Svínafellsjökull and Hoffellsjökull, are distinctly different. Svínafellsjökull displays inset and seasonally climatically-tuned push moraine sequences and subglacially streamlined surfaces typical of active temperate glaciers on sloping piedmont forelands. Hoffellsjökull displays the landform-sediment assemblages typical of outwash-head/depositional overdeepening scenarios, upon which closely-spaced composite push moraines reflect a long term quasi-stationary snout at and near the Little Ice Age maximum prior to 2000. Moraine spacing on the Svínafellsjökull foreland reflects an overall trend of annual recession punctuated by quasi-stability and/or readvance in the mid-1950s-1960 and 1975–2000 as recorded by two arcuate zones of closely-spaced and partially overprinted sawtooth and hairpin moraines. The pattern of moraine distribution here also reflects spatio-temporal changes in moraine-forming processes as dictated by changes in a combination of proglacial drainage characteristics and structural glaciology or crevasse architecture. The subglacial footprint of the Svínafellsjökull foreland contains features worthy of future research attention, including an arcuate zone of overridden moraines potentially indicative of a regional Holocene ice advance, prominent flutings and debris stripes potentially indicative of groove-ploughing and point-source bedrock plucking respectively, and relatively large drumlins.