Dark zone of the Greenland Ice Sheet controlled by distributed biologically-active impurities

Ryan, J. C., Hubbard, A., Stibal, M., Irvine-Fynn, T. D., Cook, J., Smith, L. C., Cameron, K. and Box, J. (2018) Dark zone of the Greenland Ice Sheet controlled by distributed biologically-active impurities. Nature Communications, 9, 1065. (doi: 10.1038/s41467-018-03353-2) (PMID:29540720) (PMCID:PMC5852041)

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Abstract

Albedo—a primary control on surface melt—varies considerably across the Greenland Ice Sheet yet the specific surface types that comprise its dark zone remain unquantified. Here we use UAV imagery to attribute seven distinct surface types to observed albedo along a 25 km transect dissecting the western, ablating sector of the ice sheet. Our results demonstrate that distributed surface impurities—an admixture of dust, black carbon and pigmented algae—explain 73% of the observed spatial variability in albedo and are responsible for the dark zone itself. Crevassing and supraglacial water also drive albedo reduction but due to their limited extent, explain just 12 and 15% of the observed variability respectively. Cryoconite, concentrated in large holes or fluvial deposits, is the darkest surface type but accounts for <1% of the area and has minimal impact. We propose that the ongoing emergence and dispersal of distributed impurities, amplified by enhanced ablation and biological activity, will drive future expansion of Greenland's dark zone.

Item Type:Articles
Additional Information:J.C.R. was funded by an Aberystwyth University Doctoral Career Development Scholarship (DCDS) and is currently funded by the NASA Cryosphere Program grant NNX14AH93G. The field camp, logistics and J.B. were supported by the Dark Snow Project (http://www.darksnow.org/). We also gratefully acknowledge the UK Natural Environment Research Grants NE/H024204/1 and NE/G005796/1, the Aberystwyth University Research Fund and the Danish Villum Young Investigator Programme grant VKR 023121 awarded to M.S. A.H. acknowledges support from the Centre for Arctic Gas Hydrate, Environment and Climate, funded by the Research Council of Norway through its Centres of Excellence (grant 223259). J.C. acknowledges a Rolex Award for Enterprise and L.C.S. acknowledges the NASA Cryosphere Program grant NNX14AH93G. The automatic weather stations used to validate the MODIS albedo data were funded and installed by the Greenland Analogue Project (GAP) and maintained by the Geological Survey of Denmark and Greenland (GEUS).
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Cameron, Dr Karen
Authors: Ryan, J. C., Hubbard, A., Stibal, M., Irvine-Fynn, T. D., Cook, J., Smith, L. C., Cameron, K., and Box, J.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Nature Communications
Publisher:Nature Publishing Group
ISSN:2041-1723
ISSN (Online):2041-1723
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in Nature Communications 9: 1065
Publisher Policy:Reproduced under a Creative Commons License

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