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Greenland ice mass loss during the Younger Dryas driven by Atlantic Meridional Overturning Circulation feedbacks

Greenland ice mass loss during the Younger Dryas driven by Atlantic Meridional Overturning Circulation feedbacks Thumbnail


Abstract

Understanding feedbacks between the Greenland Ice Sheet (GrIS) and the Atlantic Meridional Overturning Circulation (AMOC) is crucial for reducing uncertainties over future sea level and ocean circulation change. Reconstructing past GrIS dynamics can extend the observational record and elucidate mechanisms that operate on multi-decadal timescales. We report a highly-constrained last glacial vertical profile of cosmogenic isotope exposure ages from Sermilik Fjord, a marine-terminating ice stream in the southeast sector of the GrIS. Our reconstruction reveals substantial ice-mass loss throughout the Younger Dryas (12.9-11.7 ka), a period of marked atmospheric and sea-surface cooling. Earth-system modelling reveals that southern GrIS marginal melt was likely driven by strengthening of the Irminger Current at depth due to a weakening of the AMOC during the Younger Dryas. This change in North Atlantic circulation appears to have drawn warm subsurface waters to southeast Greenland despite markedly cooler sea surface temperatures, enhancing thermal erosion at the grounding lines of palaeo ice-streams, supporting interpretation of regional marine-sediment cores. Given current rates of GrIS meltwater input into the North Atlantic and the vulnerability of major ice streams to water temperature changes at the grounding line, this mechanism has important implications for future AMOC changes and northern hemisphere heat transport.

Acceptance Date Jun 27, 2018
Publication Date Aug 9, 2018
Publicly Available Date Mar 28, 2024
Journal Scientific Reports
Print ISSN 2045-2322
Publisher Nature Publishing Group
Pages 11307 - ?
DOI https://doi.org/10.1038/s41598-018-29226-8
Publisher URL http://doi.org/10.1038/s41598-018-29226-8

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