Proglacial icings as indicators of glacier thermal regime: ice thickness changes and icing occurrence in Svalbard

Abstract

Proglacial icings (also known as naled or aufeis) are frequently observed in the forefields of polar glaciers. Their formation has been ascribed to the refreezing of upwelling groundwater that has originated from subglacial melt, and thus the presence of icings has been used as evidence of polythermal glacier regime. We provide an updated analysis of icing occurrence in Svalbard and test the utility of icings as an indicator of thermal regime by comparing icing presence with: (1) mean glacier thickness, as a proxy for present thermal regime; and (2) evidence of past surge activity, which is an indicator of past thermal regime. A total of 279 icings were identified from TopoSvalbard imagery covering the period 2008-2012, of which 143 corresponded to icings identified by Bukowska-Jania and Szafraniec (2005) from aerial photographs from 1990. Only 46% of icings observed in 2008-2012 were found to occur at glaciers with thicknesses consistent with a polythermal regime, meaning a large proportion were associated with glaciers predicted to be of a cold or transitional thermal regime. As a result, icing presence alone may be an unsuitable indicator of glacier regime. We further found that, of the 279 glaciers with icings, 63% of cold-based glaciers and 64% of transitional glaciers were associated with evidence of surge activity. We therefore suggest Proglacial icings as indicators of glacier thermal regime that proglacial icing formation in Svalbard may reflect historical (rather than present) thermal regime, and that icings possibly originate from groundwater effusion from subglacial taliks that persist for decades following glacier thinning and associated regime change.

Drainage system and thermal structure of a High Arctic polythermal glacier: Waldemarbreen, western Svalbard

“…Generally, the glaciers of the Kaffiøyra region are thought to be polythermal with mainly cold ice, a thin temperate surface layer during the summer, which is strongly influenced by seasonal changes in temperature and potentially a temperate ice layer near the glacier bed (Sobota, 2009; Sobota and others, 2016a). The potentially polythermal structure with the temperate basal ice layer of Waldemarbreen was thought to be evidenced by the presence of icings in the forefield of the glacier (Sobota, 2009, 2016), although the presence of icings cannot be considered a reliable proof of polythermal glacier regime because they have also been found at entirely cold-based glaciers (Hodgkins and others, 2004; Bælum and Benn, 2011; Temminghoff and others, 2018; Mallinson and others, 2019).…”

UAV and GPR Data Integration in Glacier Geometry Reconstruction: A Case Study from Irenebreen, Svalbard

“…Thus, it should be considered that icings in front of glaciers in the Kaffiøyra region may be missing during summers, thus their existence or absence cannot be always used as a proof for the polythermal glacier regime. As already pointed out by several studies [68,69,82], the existence of icings is not always a proof for polythermal glacier ice as well.…”

Shallow and deep groundwater moderate methane dynamics in a high Arctic glacial catchment

“…However, large icings, which are stratified layers of ice formed by the freezing of continuous outflows of groundwater during winter (Carey, 1973), are commonly observed in proglacial plains of the high Arctic. These icings provide evidence for year-round groundwater systems that are active in both polythermal and cold-based catchments (Moorman and Michel, 2000;Hodgkins et al, 2004;Bukowska-Jania and Szafraniec, 2005;Pollard, 2005;Baelum and Benn, 2011;Mallinson et al, 2019;Chesnokova et al, 2020b;Kleber et al, 2023). Hydrological observations suggest that taliks formed beneath glaciers can extend beyond the glacial margin, providing a conduit for the groundwater flow (Moorman, 2003).…”