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AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport?

AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport?
AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport?
Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic meridional overturning circulation (AMOC). For example, in numerical “water-hosing” experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reverse on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. We discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.
Atlantic meridional overturning circulation, Optimal surface buoyancy fluxes, Ocean dynamics, Adjoint sensitivity analysis
0930-7575
1497-1513
Sevellec, Florian
01569d6c-65b0-4270-af2a-35b0a77c9140
Fedorov, Alexey V.
c4234650-4a09-4d65-b6fc-cebd592a788f
Sevellec, Florian
01569d6c-65b0-4270-af2a-35b0a77c9140
Fedorov, Alexey V.
c4234650-4a09-4d65-b6fc-cebd592a788f

Sevellec, Florian and Fedorov, Alexey V. (2016) AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport? Climate Dynamics, 47 (5-6), 1497-1513. (doi:10.1007/s00382-015-2915-4).

Record type: Article

Abstract

Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic meridional overturning circulation (AMOC). For example, in numerical “water-hosing” experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reverse on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. We discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.

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Accepted/In Press date: 13 November 2015
Published date: 4 January 2016
Keywords: Atlantic meridional overturning circulation, Optimal surface buoyancy fluxes, Ocean dynamics, Adjoint sensitivity analysis
Organisations: Physical Oceanography

Identifiers

Local EPrints ID: 401951
URI: http://eprints.soton.ac.uk/id/eprint/401951
ISSN: 0930-7575
PURE UUID: 43fc0f00-2efa-49b1-8b84-575e86389ab1

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Date deposited: 24 Oct 2016 12:54
Last modified: 15 Mar 2024 03:01

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Author: Alexey V. Fedorov

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