Glacier retreat and landform production on an overdeepened glacier foreland: the debris‐charged glacial landsystem at Kvíárjökull, Iceland

Abstract

Glacier recession and landform development in a debris-charged glacial landsystem characterized by an overdeepening is quantified using digital photogrammetry, digital elevation model (DEM) construction and mapping of the Icelandic glacier Kvíárjökull for the period 1945–2003. Melting of ice-cores is recorded by surface lowering rates of 0·8 m yr–1 (1945–1964), 0·3 m yr–1 (1964–1980), 0·015 m yr–1 (1980–1998) and 0·044 m yr–1 (1998–2003). The distribution/preservation of pushed and stacked ice-cored moraine complexes are determined by the location of the long-term glacial drainage network in combination with retreat from the overdeepening, into which glacifluvial sediment is being directed and where debris-rich ice masses are being reworked and replaced by esker networks produced in englacial meltwater pathways that bypassed the overdeepening and connected to outwash fans prograding over the snout. Recent accelerated retreat of Kvíárjökull, potentially due to increased mass balance sensitivity, has made the snout highly unstable, especially now that the overdeepening is being uncovered and the snout flooded by an expanding pro-glacial, and partially supraglacial, lake. This case study indicates that thick sequences of debris-charged basal ice/controlled moraine have a very low preservation potential but ice-cored moraine complexes can develop into hummocky moraine belts in de-glaciated terrains because they are related to the process of incremental stagnation, which at Kvíárjökull has involved periodic switches from transport-dominant to ablation-dominant conditions. Glacier recession is therefore recorded temporally and spatially by two suites of landforms relating to two phases of landform production which are likely typical for glaciers occupying overdeepenings: an early phase of active, temperate recession recorded by push moraines and lateral moraines and unconfined pro-glacial meltwater drainage; and a later phase of incremental stagnation and pitted outwash head development initiated by the increasing topographic constraints of the latero-frontal moraine arc and the increasing importance of the overdeepening as a depo-centre. Copyright © 2012 John Wiley & Sons, Ltd

Quantification of the ice-cored moraines' short-term dynamics in the high-Arctic glaciers Ebbabreen and Ragnarbreen, Petuniabukta, Svalbard

“…Schomacker and Kjaer (2008) reported 0.9 m a -1 of mean annual surface lowering for the ice-cored moraines of Holmströmbreen in the period . Values of a similar magnitude were also presented for several Icelandic glaciers: 0.015-0.80 m a -1 for ice-cored moraines of Kvíárjökull (Bennett and Evans, 2012), 0.10-0.18 m a -1 for Brúarjökull (Schomacker and Kjaer, 2007), and 0.3-1.4 m a -1 for Kötlujökull (Krüger and Kjaer, 2000).…”

Snæfellsjökull volcano-centred ice cap landsystem, West Iceland

“…Together with the most recent push moraines (see Section 3.2), this moraine belt possibly marks the position of the mid to late 1990s readvance margin, a feature identified at a range of locations around Iceland (e.g. Bennett & Evans, 2012;Bradwell et al, 2006;Evans et al, 2009Evans et al, , 2015bEvans & Hiemstra, 2005).…”

“…Localized exposures through the push ridges reveal deformed stratified sediments indicative of recent glacier readvance into proglacial outwash, potentially driven by the mid to late 1990s positive mass balance trends recognized throughout Iceland (e.g. Bennett & Evans, 2012;Bradwell, Dugmore, & Sugden, 2006;Evans & Hiemstra, 2005;Evans, Shand, & Petrie, 2009, 2015b.…”

Fláajökull (north lobe), Iceland: active temperate piedmont lobe glacial landsystem

“…Bennett & Evans, 2012;Bradwell, Dugmore, & Sugden, 2006;Evans, Shand, & Petrie, 2009). This was significant in terms of the Fláajökull foreland geomorphology, in that it resulted in the construction of a composite push moraine (Evans, 2003(Evans, , 2005Evans & Hiemstra, 2005) typical of stationary temperate glacier snouts (Evans, 2013;Krüger, 1993).…”