Overturning in the subpolar North Atlantic: a review

The Overturning in the Subpolar North Atlantic Program (OSNAP) was initiated in the spring of 2010 through a collaborative effort involving the USA, the UK, Germany, the Netherlands and Canada. A key feature of OSNAP is a trans-basin observing system deployed in the summer of 2014 for the continuous...

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Bibliographic Details
Published in:Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Main Author: Lozier, M. Susan
Other Authors: National Science Foundation Physical Oceanography Program
Format: Article in Journal/Newspaper
Language:English
Published: The Royal Society 2023
Subjects:
Online Access:http://dx.doi.org/10.1098/rsta.2022.0191
https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.2022.0191
https://royalsocietypublishing.org/doi/full-xml/10.1098/rsta.2022.0191
Description
Summary:The Overturning in the Subpolar North Atlantic Program (OSNAP) was initiated in the spring of 2010 through a collaborative effort involving the USA, the UK, Germany, the Netherlands and Canada. A key feature of OSNAP is a trans-basin observing system deployed in the summer of 2014 for the continuous measure of volume, heat and freshwater fluxes in the subpolar North Atlantic. This review focuses on advancements made possible by the collective OSNAP observations. Chief among those advancements is the quantification of the dominant role of the eastern subpolar North Atlantic in the production of dense waters that reside in the lower limb of the overturning: the Irminger and Iceland basins contributed approximately three times as much dense water compared with the Labrador Sea over the observational period. Other advancements include elucidation of the relationship between convective activity in the basin interior and boundary current anomalies; the spread of overflow waters in the subpolar region; the seasonality of the meridional volume, heat and freshwater fluxes; and the challenges involved in designing a simpler, less costly observing system. Collectively, OSNAP measurements are laying a framework on which to assess the overturning circulation's vulnerability to continued warming and freshening as climate change continues apace. This article is part of a discussion meeting issue ‘Atlantic overturning: new observations and challenges’.