Rapid export of waters formed by convection near the Irminger Sea's western boundary

Le Bras, I. A.‐A.; Straneo, F.; Holte, J.; Jong, M. F.; Holliday, N. P. ORCID: https://orcid.org/0000-0002-9733-8002. 2020 Rapid export of waters formed by convection near the Irminger Sea's western boundary. Geophysical Research Letters, 47 (3), e2019GL085989. 10.1029/2019GL085989

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Abstract/Summary

The standard view of the overturning circulation emphasizes the role of convection, yet for waters to contribute to overturning, they must not only be transformed to higher densities but also exported equatorward. From novel mooring observations in the Irminger Sea (2014–2016), we describe two water masses that are formed by convection and show that they have different rates of export in the western boundary current. Upper Irminger Sea Intermediate Water appears to form near the boundary current and is exported rapidly within 3 months of its formation. Deep Irminger Sea Intermediate Water forms in the basin interior and is exported on longer time scales. The subduction of these waters into the boundary current is consistent with an eddy transport mechanism. Our results suggest that light intermediate waters can contribute to overturning as much as waters formed by deeper convection and that the export time scales of both project onto overturning variability. Plain Language Summary The deep ocean can regulate the Earth's climate by storing carbon and heat. At high latitudes, waters are cooled by the atmosphere and sink, but they can only be successfully stored in the deep ocean if they are exported toward the equator. In this study, we analyze new mooring observations in the Irminger Sea to investigate the cooling and export of high‐latitude waters. In addition to the well‐documented waters that are cooled in the center of the Irminger Sea, we find that saltier waters are cooled near the western boundary current. Both of these water types make it into boundary current and are exported. Our observations are consistent with the dynamics of swirling eddy motions. The eddy transport process is more effective for the waters cooled near the boundary current, implying that cooling near boundary currents may be more important for the climate than has been appreciated to date.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1029/2019GL085989
ISSN:	0094-8276
Date made live:	06 Feb 2020 09:10 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/526717

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