Isopycnal eddy stirring dominates thermohaline mixing in the upper subpolar North Atlantic

Fernández Castro, Bieito; Fernández Román, Daniel; Ferron, Bruno; Fontela, Marcos; Lherminier, Pascale; Naveira Garabato, Alberto; Pérez, Fiz F.; Spingys, Carl; Polzin, Kurt; Velo, Antón. 2024 Isopycnal eddy stirring dominates thermohaline mixing in the upper subpolar North Atlantic. Journal of Geophysical Research: Oceans, 129 (9). 10.1029/2023JC020817

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Text © 2024. The Author(s).This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. JGR Oceans - 2024 - Fernández Castro - Isopycnal Eddy Stirring Dominates Thermohaline Mixing in the Upper Subpolar North.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (4MB) | Preview

Abstract/Summary

The Atlantic Meridional Overturning Circulation entails vigorous thermohaline transformations in the subpolar North Atlantic Ocean (SPNA). There, warm and saline waters originating in the (sub)tropics are converted into cooler and fresher waters by a combination of surface fluxes and sub-surface mixing. Using microstructure measurements and a small-scale variance conservation framework, we quantify the diapycnal and isopycnal contributions –by microscale turbulence and mesoscale eddies, respectively– to thermohaline mixing within the eastern SPNA. Isopycnal stirring is found to account for the majority of thermal (65%) and haline (84%) variance dissipation in the upper 400 m of the eastern SPNA. A simple dimensional analysis suggests that isopycnal stirring could account for (5–10) Sv of diahaline volume flux, suggesting an important role of such stirring in regional water-mass transformations. Our mixing measurements are thus consistent with recent indirect estimates in highlighting the importance of isopycnal stirring for North Atlantic overturning.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1029/2023JC020817
ISSN:	2169-9275
Additional Keywords:	subpolar North Atlantic, microstructure turbulence, diapycnal mixing, isopycnal stirring, thermohaline transformations, meridional overturning circulation
Date made live:	01 Oct 2024 13:05 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538126

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