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 a previous study of 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 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.

KEYWORDS:

• Icing
• aufeis
• naled
• glacier thermal regime
• proglacial
• Svalbard

Acknowledgements

We thank two anonymous reviewers for their constructive comments that helped to improve our manuscript and Andrew J. Hodson for discussion during the initial planning of this work.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Laura Mallinson was born in 1996. Laura completed her BSc Geography degree at the University of Sheffield in 2018. She graduated with first class honours and was awarded the Alice Garnett Prize by the Department of Geography for the quality of her undergraduate dissertation.

Darrel A. Swift was born in 1976. Darrel completed a dual-honours degree in Geography and Educational Studies at Keele University in 1997 and subsequently completed a PhD on the provenance of suspended sediment in subglacial drainage systems at the University of Glasgow in 2002. He was awarded a BP Personal Research Fellowship in 2003 by the Royal Society of Edinburgh, during which he remained affiliated to the University of Glasgow, and in 2006, he joined the Department of Geography at the University of Sheffield, where he is now Senior Lecturer in Geoscience. Darrel's research covers many aspects of glaciology and glacial geomorphology, including subglacial hydrology, glacial erosion and sediment transport, and long-term glacial landscape evolution.

Andrew Sole was born in 1982. He received an MA in Physical Geography from the University of Edinburgh in 2005 and a PhD in glaciology (entitled ‘Investigating Greenland Outlet Glaciers') from the University of Bristol in 2010. From 2009 to 2012, Andrew worked on ‘The role of atmospheric forcing on the dynamic stability of Greenland's outlet glaciers’ as a Postdoctoral Research Assistant at the Universities of Aberdeen and Edinburgh. Andrew joined the University of Sheffield as a Faculty Research Fellow in 2012, and in 2017 became a Lecturer in Physical Geography. Andrew's research is focused on furthering our understanding of the mass balance and dynamic stability of glaciers and ice sheets (particularly the Greenland Ice Sheet, and recently the Antarctic Ice Sheet) in a changing climate through the use of satellite and airborne remote sensing, fieldwork and numerical modelling.

ORCID

Darrel A. Swift http://orcid.org/0000-0001-5320-5104

Andrew Sole http://orcid.org/0000-0001-5290-8967