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Signature of ocean warming at the mixed layer base

Signature of ocean warming at the mixed layer base
Signature of ocean warming at the mixed layer base
The warming climate influences the ocean by changing its wind‐driven dynamics and by inputting extra heat. This study analyzes the warming where temperature anomalies penetrate the ocean interior, that is, by focusing on the winter mixed layer base. This allows to distinguish regions where ocean circulation contributes to warm anomalies from locations where density‐compensated temperature anomalies locally enter the ocean along isopycnals. Multidecadal (1980–2018) local temperature trends from a hydrographic data set are examined at the winter mixed layer base and partitioned into components relating to isopycnal movement (heave) and change along isopycnals (spice). Subtropical gyres and western boundary currents show warming larger than the global average that mostly projects onto heave. This is the result of the strengthening of the circulation in the Southern Hemisphere subtropical gyres and is related to both wind‐driven changes and Southern Ocean warming. Subtropical regions of surface salinity maxima are influenced by warm anomalies along isopycnals.
0094-8276
Clément, Louis
bd1aafc4-3240-46e3-88d4-141f2b9cc1cc
Mcdonagh, Elaine L.
47e26eeb-b774-4068-af07-31847e42b977
Marzocchi, Alice
b755e4a1-8c30-4cfc-bcdf-848414c53311
Nurser, A. J. George
2493ef9a-21e9-4d8b-9c32-08677e7e145a
Clément, Louis
bd1aafc4-3240-46e3-88d4-141f2b9cc1cc
Mcdonagh, Elaine L.
47e26eeb-b774-4068-af07-31847e42b977
Marzocchi, Alice
b755e4a1-8c30-4cfc-bcdf-848414c53311
Nurser, A. J. George
2493ef9a-21e9-4d8b-9c32-08677e7e145a

Clément, Louis, Mcdonagh, Elaine L., Marzocchi, Alice and Nurser, A. J. George (2020) Signature of ocean warming at the mixed layer base. Geophysical Research Letters, 47 (1), [e2019GL086269]. (doi:10.1029/2019GL086269).

Record type: Article

Abstract

The warming climate influences the ocean by changing its wind‐driven dynamics and by inputting extra heat. This study analyzes the warming where temperature anomalies penetrate the ocean interior, that is, by focusing on the winter mixed layer base. This allows to distinguish regions where ocean circulation contributes to warm anomalies from locations where density‐compensated temperature anomalies locally enter the ocean along isopycnals. Multidecadal (1980–2018) local temperature trends from a hydrographic data set are examined at the winter mixed layer base and partitioned into components relating to isopycnal movement (heave) and change along isopycnals (spice). Subtropical gyres and western boundary currents show warming larger than the global average that mostly projects onto heave. This is the result of the strengthening of the circulation in the Southern Hemisphere subtropical gyres and is related to both wind‐driven changes and Southern Ocean warming. Subtropical regions of surface salinity maxima are influenced by warm anomalies along isopycnals.

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Cl-ment_et_al-2020-Geophysical_Research_Letters - Accepted Manuscript
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Accepted/In Press date: 3 January 2020
Published date: 16 January 2020
Additional Information: Funding Information: L.?C. thanks Trevor McDougall for stimulating discussions on the spice and heave decomposition. This study benefited from discussions with Brian King, Harry Bryden, Yvonne Firing, and Rachel Killick. The manuscript was significantly improved by the comments of three anonymous reviewers. The present work was funded by the NERC project (NE/P019293/1) Transient tracer-based Investigation of Circulation and Thermal Ocean Change (TICTOC). The EN4 data set version EN.4.2.1 is provided by the Met Office Hadley Centre (https://www.metoffice.gov.uk/hadobs/en4/download.html). The Simple Ocean Data Assimilation SODA v3.7.2 is provided by the University of Maryland and Texas A&M University and can be accessed online (http://dsrs.atmos.umd.edu/DATA/soda3.7.2/REGRIDED/ocean). The NOAA-NODC database can be accessed at the website (https://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT). Publisher Copyright: © 2020. American Geophysical Union. All Rights Reserved.

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Local EPrints ID: 438062
URI: http://eprints.soton.ac.uk/id/eprint/438062
ISSN: 0094-8276
PURE UUID: 039707e9-2bc1-4263-b933-234b9f180532

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Date deposited: 27 Feb 2020 17:30
Last modified: 01 Sep 2022 17:07

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Contributors

Author: Louis Clément
Author: Elaine L. Mcdonagh
Author: Alice Marzocchi
Author: A. J. George Nurser

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