The glacial landsystem of Hoffellsjökull, 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.

Sub‐annual moraine formation at an active temperate Icelandic glacier

“…Chandler et al ., ; Evans et al ., ). Indeed, recent retreat into subglacial overdeepenings, coupled with the development of full‐depth crevassing and marginal pecten, has been recognized as a control on sawtooth and hairpin‐shaped moraine formation at several Icelandic active temperate outlets, representing a temporal switch in the active temperate landsystem signature (Evans et al ., , , , ). Previously identified sub‐annual moraines at Skálafellsjökull are also associated with a reverse slope and impeded drainage (Chandler et al ., ).…”

“…Annual moraines are particularly prevalent in Iceland, and long sequences of (presumed) annual moraines are ubiquitous on the low-lying forelands of the maritime outlets of Öraefajökull and Vatnajökull, southeast Iceland (e.g. Thórarinsson, 1967;Price, 1970;Sharp, 1984;Boulton, 1986;Evans and Twigg, 2002;Evans and Hiemstra, 2005;Chandler et al, 2016aChandler et al, , 2016bChandler et al, , 2016Evans et al, 2016aEvans et al, , 2017Evans et al, , 2019a. With their distinctive, intricate 'sawtooth' or crenulated planforms, these annual moraine sequences are spectacular phenomena and a characteristic signature of the active temperate glacial landsystem (cf.…”

Sub-annual moraine formation at an active temperate Icelandic glacier

“…Chandler et al, 2016a;Evans et al, 2016a). Indeed, recent retreat into subglacial overdeepenings, coupled with the development of full-depth crevassing and marginal pecten, has been recognized as a control on sawtooth and hairpin-shaped moraine formation at several Icelandic active temperate outlets, representing a temporal switch in the active temperate landsystem signature (Evans et al, , 2017(Evans et al, , 2018c(Evans et al, , 2019a. Previously identified subannual moraines at Skálafellsjökull are also associated with a reverse slope and impeded drainage (Chandler et al, 2016a).…”

“…Annual moraines are particularly prevalent in Iceland, and long sequences of (presumed) annual moraines are ubiquitous on the low-lying forelands of the maritime outlets of Öraefajökull and Vatnajökull, southeast Iceland (e.g. Thórarinsson, 1967;Price, 1970;Sharp, 1984;Boulton, 1986;Evans and Twigg, 2002;Evans and Hiemstra, 2005;Chandler et al, 2016aChandler et al, , 2016bChandler et al, , 2016Evans et al, 2016aEvans et al, , 2017Evans et al, , 2019a. With their distinctive, intricate 'sawtooth' or crenulated planforms, these annual moraine sequences are spectacular phenomena and a characteristic signature of the active temperate glacial landsystem (cf.…”

Glacial and periglacial geomorphology of central Troms and Finnmark county, Arctic Norway

“…Figure 2). In some areas there are clusters of 'saw-tooth' frontal moraine ridges, exhibiting 'teeth' pointing down valley and notches pointing up valley (Burki et al, 2009;Evans et al, 2017bEvans et al, , 2019Matthews et al, 1979). Within some recently deglaciated terrain there are series of densely spaced moraines that lie generally <15 m apart, likely reflecting annual or possibly sub-annual deposition at highly active glacier margins (Boulton, 1986;Chandler et al, 2016Chandler et al, , 2020Evans, 2001;Evans & Twigg, 2002;Lukas, 2012;Reinardy et al, 2013;Sharp, 1984).…”