Search

Proglacial groundwater-fed features, such as seeps, substantially impact proglacial geomorphology, hydrology, and ecology. However, there is a paucity of research on the impacts of climate change and glacier retreat on the extent of these important features. This paper aims to investigate the impact of glacier retreat on proglacial groundwater levels and on the extent of groundwater-fed seeps. Research has taken place in western Skeiðarársandur, the large proglacial outwash plain of Skeiðarárjökull, a retreating temperate glacier in southeast Iceland. Changes in the extent of proglacial groundwater seeps were mapped using historical aerial photographs from 1986, 1997, and 2012. Proglacial groundwater levels were monitored in shallow boreholes between 2000 and 2012. The western margin of Skeiðarárjökull has retreated approximately 1 km beyond its position in 1986. However, this retreat was punctuated by short periods of readvance. The geomorphology and groundwater systems at the site were substantially impacted by the November 1996 jökulhlaup, whose deposits altered approximately 18% of the area of groundwater seeps. The surface areas of groundwater seeps and lakes in the study area have declined by ~97% between 1986 and 2012. Most of the decline took place after 1997, when the mean annual rate of retreat increased three-fold. Groundwater levels also declined substantially between 2000 and 2012, although this trend varies spatially. The paper provides a conceptual model of the controls on proglacial shallow groundwater systems. Direct impacts of glacier retreat are suggested as the main cause for the declines in proglacial groundwater levels and in the extent of groundwater seeps. These declines are expected to adversely impact sandur ecology. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]