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Greenland Ice Sheet exports labile organic carbon to the Arctic oceans

Lawson, Emily C.; Wadham, Jemma L.; Tranter, Martyn; Stibal, Marek; Lis, Greg P.; Butler, Catriona E.H.; Laybourn-Parry, Johanna; Nienow, Peter; Chandler, David; Dewsbury, Paul

Authors

Emily C. Lawson emily.lawson@nottingham.ac.uk

Jemma L. Wadham j.l.wadham@bris.ac.uk

Martyn Tranter m.tranter@bristol.ac.uk

Marek Stibal msti@geus.dk

Greg P. Lis geoglisu@gmail.com

Catriona E.H. Butler catriona.butler@gmail.com

Johanna Laybourn-Parry jo.laybourn-parry@bristol.ac.uk

Peter Nienow peter.nienow@ed.ac.uk

David Chandler davemchandler@gmail.com

Paul Dewsbury paul.dewsbury@thermofisher.com



Abstract

Runoff from small glacier systems contains dissolved organic carbon (DOC) rich in protein-like, low molecular weight (LMW) compounds, designating glaciers as an important source of bioavailable carbon for downstream heterotrophic activity. Fluxes of DOC and particulate organic carbon (POC) exported from large Greenland catchments, however, remain unquantified, despite the Greenland Ice Sheet (GrIS) being the largest source of global glacial runoff (ca. 400 km3 yr−1). We report high and episodic fluxes of POC and DOC from a large (> 600 km2) GrIS catchment during contrasting melt seasons. POC dominates organic carbon (OC) export (70–89% on average), is sourced from the ice sheet bed, and contains a significant bioreactive component (9% carbohydrates). A major source of the “bioavailable” (free carbohydrate) LMW–DOC fraction is microbial activity on the ice sheet surface, with some further addition of LMW–DOC to meltwaters by biogeochemical processes at the ice sheet bed. The bioavailability of the exported DOC (26–53%) to downstream marine microorganisms is similar to that reported from other glacial watersheds. Annual fluxes of DOC and free carbohydrates during two melt seasons were similar, despite the approximately two-fold difference in runoff fluxes, suggesting production-limited DOC sources. POC fluxes were also insensitive to an increase in seasonal runoff volumes, indicating a supply limitation in suspended sediment in runoff. Scaled to the GrIS, the combined DOC (0.13–0.17 TgC yr−1 (±13 %)) and POC fluxes (mean = 0.36–1.52 TgC yr−1 (±14 %)) are of a similar order of magnitude to a large Arctic river system, and hence may represent an important OC source to the near-coastal North Atlantic, Greenland and Labrador seas.

Citation

Lawson, E. C., Wadham, J. L., Tranter, M., Stibal, M., Lis, G. P., Butler, C. E., …Dewsbury, P. (2014). Greenland Ice Sheet exports labile organic carbon to the Arctic oceans. Biogeosciences, 11(14), doi:10.5194/bg-11-4015-2014

Journal Article Type Article
Publication Date Jul 31, 2014
Deposit Date Oct 17, 2014
Publicly Available Date Oct 17, 2014
Journal Biogeosciences
Print ISSN 1726-4170
Electronic ISSN 1726-4170
Publisher European Geosciences Union
Peer Reviewed Peer Reviewed
Volume 11
Issue 14
DOI https://doi.org/10.5194/bg-11-4015-2014
Keywords Glacier, carbon, bioavailable, microbes, Greenland Ice Sheet
Public URL http://eprints.nottingham.ac.uk/id/eprint/27608
Publisher URL http://www.biogeosciences.net/11/4015/2014/bg-11-4015-2014.html
Related Public URLs http://www.biogeoscienc...14/bg-11-4015-2014.html
http://www.nottingham.a...phy/people/emily.lawson
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0





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