Articles | Volume 18, issue 5
Ocean Sci., 18, 1507–1533, 2022
https://doi.org/10.5194/os-18-1507-2022
Ocean Sci., 18, 1507–1533, 2022
https://doi.org/10.5194/os-18-1507-2022
Research article
 | Highlight paper
21 Oct 2022
Research article  | Highlight paper | 21 Oct 2022

Exceptional freshening and cooling in the eastern subpolar North Atlantic caused by reduced Labrador Sea surface heat loss

Alan D. Fox et al.

Data sets

Trajectories used in "Exceptional freshening and cooling in the eastern subpolar North Atlantic caused by reduced Labrador Sea surface heat loss." Alan D. Fox, Willi Rath, and  Christina Schmidt https://hdl.handle.net/20.500.12085/830c72af-b5ca-44ac-8357-3173392f402b

Atlantic meridional overturning circulation observed by the RAPID-MOCHA-WBTS (RAPID-Meridional Overturning Circulation and Heatflux Array-Western Boundary Time Series) array at 26N from 2004 to 2020 (v2020.1) E. Frajka-Williams, B. I. Moat, D. Smeed, D. Rayner, W. E. Johns, M. O. Baringer, D. L., and J. Collins https://doi.org/10.5285/cc1e34b3-3385-662b-e053-6c86abc03444

Model code and software

Code used in Fox et al 2022. "Exceptional freshening and cooling in the eastern subpolar North Atlantic caused by reduced Labrador Sea surface heat loss" Alan D. Fox, Willi Rath, and Christina Schmidt https://doi.org/10.5281/zenodo.6393656

NEMO ocean engine Madec Gurvan, Romain Bourdallé-Badie, Pierre-Antoine Bouttier, Clément Bricaud, Diego Bruciaferri, Daley Calvert, Jérôme Chanut, Emanuela Clementi, Andrew Coward, Damiano Delrosso, Christian Ethé, Simona Flavoni, Tim Graham, James Harle, Doroteaciro Iovino, Dan Lea, Claire Lévy, Tomas Lovato, Nicolas Martin, Sébastien Masson, Silvia Mocavero, Julien Paul, Clément Rousset, Dave Storkey, Andrea Storto and Martin Vancoppenolle https://doi.org/10.5281/zenodo.3248739

OceanParcels/parcels: Parcels v2.2.2 Erik van Sebille, Philippe Delandmeter, Michael Lange, Christian Kehl, Roel Brouwer, Daan Reijnders, Reint, Willi Rath, pdnooteboom, Joe Scutt Phillips, Simnator101, Angus Gibson, Joel Kronborg, Paul Petersik, Thomas-95, David Wichmann, pierrick-giffard, Julius Busecke, Miriam Sterl, Raymond Edwards, SLYpma, Wouter Mol, Doug Klink, hart-davis, Luc Vandenbulcke, Jelle Treep, Shaun Walbridge, Alex Novaes de Santana, and David A. Hamand Guido Vettoretti https://doi.org/10.5281/zenodo.4501321

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Executive editor
In this paper, a new hypothesis is put forward to explain the remarkable freshening of the Subpolar North Atlantic that peaked in 2016. The hypothesis emphasizes the increased surface circulation in the Labrador Sea region, following a reduction in heat loss to the atmosphere during the period 2000-2013. This new hypothesis, supported by the analysis of a very high resolution ocean model, contrasts with other studies that concluded to an overwhelming role of the reduced Atlantic Meridional Overturning Circulation in the freshening. In the present study, the AMOC decline is shown to account for not more than 27% of the freshening. Overall, this paper points out that surface properties of the Subpolar North Atlantic Ocean, which are important for European climate, cannot be understood in terms of AMOC variability only, but rather depend on the horizontal circulation at the ocean surface and on regional air-sea exchanges.
Short summary
Observations of the eastern subpolar North Atlantic in the 2010s show exceptional freshening and cooling of the upper ocean, peaking in 2016 with the lowest salinities recorded for 120 years. Using results from a high-resolution ocean model, supported by observations, we propose that the leading cause is reduced surface cooling over the preceding decade in the Labrador Sea, leading to increased outflow of less dense water and so to freshening and cooling of the eastern subpolar North Atlantic.