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Major variations in subtropical North Atlantic heat transport at short (5 day) timescales and their causes

Major variations in subtropical North Atlantic heat transport at short (5 day) timescales and their causes
Major variations in subtropical North Atlantic heat transport at short (5 day) timescales and their causes
Variability in the North Atlantic ocean heat transport at 26.5°N on short (5 day) timescales is identified and contrasted with different behaviour at monthly intervals using a combination of RAPID/MOCHA/WBTS measurements and the NEMO-LIM2 1/12° ocean circulation/sea ice model. Wind forcing plays the leading role in establishing the heat transport variability through the Ekman transport response of the ocean and the associated driving atmospheric conditions vary significantly with timescale. We find that at 5 day timescales the largest changes in the heat transport across 26.5°N coincide with north-westerly airflows originating over the American land mass that drive strong southward anomalies in the Ekman flow. During these events the northward heat transport reduces by 0.5–1.4 PW. In contrast, the Ekman transport response at longer monthly timescales is smaller in magnitude (up to 0.5 PW) and consistent with expected variations in the leading mode of North Atlantic atmospheric variability, the North Atlantic Oscillation. The north-westerly airflow mechanism can have a prolonged influence beyond the central 5 day timescale and on occasion can reduce the accumulated winter ocean heat transport into the North Atlantic by ?40%.
Atlantic Ocean heat transport, Atlantic subtropical gyre, model-data comparison, RAPID mooring array, Ekman Transport
0148-0227
3237-3249
Moat, B.I.
497dbb18-a98f-466b-b459-aa2c872ad2dc
Josey, S.A.
2252ab7f-5cd2-49fd-a951-aece44553d93
Sinha, B.
544b5a07-3d74-464b-9470-a68c69bd722e
Blaker, A.T.
94efe8b2-c744-4e90-87d7-db19ffa41200
Smeed, D.A.
79eece5a-c870-47f9-bba0-0a4ef0369490
Mccarthy, G.
99241bcb-5667-469d-b7ae-4d308d516bd6
Johns, W.E
2789505f-bc6d-4fb4-8a55-1a6d6a9242d2
Hirschi, J.-M.
c8a45006-a6e3-4319-b5f5-648e8ef98906
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Rayner, D.
60eaf35c-c54e-447b-8551-efc08637d122
Duchez, A.
d73f2e60-bc41-4fb5-9686-6e12048a6f2d
Coward, A.C.
53b78140-2e65-476a-b287-e8384a65224b
Moat, B.I.
497dbb18-a98f-466b-b459-aa2c872ad2dc
Josey, S.A.
2252ab7f-5cd2-49fd-a951-aece44553d93
Sinha, B.
544b5a07-3d74-464b-9470-a68c69bd722e
Blaker, A.T.
94efe8b2-c744-4e90-87d7-db19ffa41200
Smeed, D.A.
79eece5a-c870-47f9-bba0-0a4ef0369490
Mccarthy, G.
99241bcb-5667-469d-b7ae-4d308d516bd6
Johns, W.E
2789505f-bc6d-4fb4-8a55-1a6d6a9242d2
Hirschi, J.-M.
c8a45006-a6e3-4319-b5f5-648e8ef98906
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Rayner, D.
60eaf35c-c54e-447b-8551-efc08637d122
Duchez, A.
d73f2e60-bc41-4fb5-9686-6e12048a6f2d
Coward, A.C.
53b78140-2e65-476a-b287-e8384a65224b

Moat, B.I., Josey, S.A., Sinha, B., Blaker, A.T., Smeed, D.A., Mccarthy, G., Johns, W.E, Hirschi, J.-M., Frajka-Williams, E., Rayner, D., Duchez, A. and Coward, A.C. (2016) Major variations in subtropical North Atlantic heat transport at short (5 day) timescales and their causes. Journal of Geophysical Research, 121 (5), 3237-3249. (doi:10.1002/2016JC011660).

Record type: Article

Abstract

Variability in the North Atlantic ocean heat transport at 26.5°N on short (5 day) timescales is identified and contrasted with different behaviour at monthly intervals using a combination of RAPID/MOCHA/WBTS measurements and the NEMO-LIM2 1/12° ocean circulation/sea ice model. Wind forcing plays the leading role in establishing the heat transport variability through the Ekman transport response of the ocean and the associated driving atmospheric conditions vary significantly with timescale. We find that at 5 day timescales the largest changes in the heat transport across 26.5°N coincide with north-westerly airflows originating over the American land mass that drive strong southward anomalies in the Ekman flow. During these events the northward heat transport reduces by 0.5–1.4 PW. In contrast, the Ekman transport response at longer monthly timescales is smaller in magnitude (up to 0.5 PW) and consistent with expected variations in the leading mode of North Atlantic atmospheric variability, the North Atlantic Oscillation. The north-westerly airflow mechanism can have a prolonged influence beyond the central 5 day timescale and on occasion can reduce the accumulated winter ocean heat transport into the North Atlantic by ?40%.

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More information

Accepted/In Press date: 5 April 2016
e-pub ahead of print date: 20 May 2016
Keywords: Atlantic Ocean heat transport, Atlantic subtropical gyre, model-data comparison, RAPID mooring array, Ekman Transport
Organisations: Marine Systems Modelling, Physical Oceanography, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 391329
URI: http://eprints.soton.ac.uk/id/eprint/391329
ISSN: 0148-0227
PURE UUID: 2e12dad0-a6cb-4b7b-b851-ea8c24ff8465
ORCID for E. Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838

Catalogue record

Date deposited: 07 Apr 2016 16:08
Last modified: 07 Oct 2020 01:57

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