Isopycnal Eddy Stirring Dominates Thermohaline Mixing in the Upper Subpolar North Atlantic
Abstract 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.
Authors
- Alberto C. Naveira Garabato (ORCID: https://orcid.org/0000-0001-6071-605X)
- Bruno Ferron (ORCID: https://orcid.org/0000-0002-2107-0900)
- A. Velo (ORCID: https://orcid.org/0000-0002-7598-5700)
- Daniel Fernández Román (ORCID: https://orcid.org/0000-0002-3001-1849)
- Marcos Fontela (ORCID: https://orcid.org/0000-0002-7486-0922)
- Pascale Lherminier (ORCID: https://orcid.org/0000-0001-9007-2160)
- Carl Spingys (ORCID: https://orcid.org/0000-0001-6220-3047)
- Fı́z F. Pérez (ORCID: https://orcid.org/0000-0003-4836-8974)
- Bieito Fernández Castro (ORCID: https://orcid.org/0000-0001-7797-854X)
- Kurt L. Polzin (ORCID: https://orcid.org/0000-0002-9991-1941)
Institutions
- Centre National de la Recherche Scientifique (FR)
- Ifremer (FR)
- Université de Bretagne Occidentale (FR)
- National Oceanography Centre (GB)
- Instituto de Investigacións Mariñas (ES)
- Laboratory for Ocean Physics and Satellite Remote Sensing (FR)
- Institut Universitaire Européen de la Mer (FR)
- Institut de Recherche pour le Développement (FR)
- University of Southampton (GB)
- Universidade de Vigo (ES)
- Woods Hole Oceanographic Institution (US)
Publication Details
- Journal
- Journal of Geophysical Research Oceans
- Published
- 2024-09-01
- DOI
- https://doi.org/10.1029/2023jc020817
- Citations
- 3
- Primary Topic
- Oceanographic and Atmospheric Processes
- Type
- article
- Field-Weighted Citation Impact
- 1.44
Funders
- Sight Research UK
- Ministerio de Ciencia e Innovación
- HORIZON EUROPE Framework Programme
- Natural Environment Research Council
- Agencia Estatal de Investigación