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The major role of air‐sea heat fluxes in driving interannual variations of Gulf Stream transport

The major role of air‐sea heat fluxes in driving interannual variations of Gulf Stream transport
The major role of air‐sea heat fluxes in driving interannual variations of Gulf Stream transport
The Gulf Stream (GS) is central to the global redistribution of heat due to the transport of large volumes of warm water from the tropics to high latitudes and the extreme ocean heat loss to the atmosphere. This study assesses the extent to which winter surface heat fluxes and wind stress curl can drive interannual variations of the full‐depth GS transport. Intensification of the GS has been observed (e.g., April 1977) immediately after a winter of frequent cold air outbreaks that led to a deepening of the mixed layer and subsequent steepening of meridional temperature gradients to the south of the GS. This forcing process is further investigated here using the ORCA12 hindcast (1978–2010) from the global, eddy‐resolving, ocean‐only Nucleus for European Modeling of the Ocean model in order to understand GS forcing mechanisms. Lagrangian analysis is also undertaken to examine the impact on the southern recirculation gyre. Results show that surface heat fluxes and wind stress curl can act in concert to effect year‐to‐year changes of up to 38% of the spring GS transport at 70°W. However, anomalous heat losses (∼200 Wm‐2) over the western Subtropical Gyre are found to be the dominant cause of peaks in GS transport via two mechanisms: (1) a strengthening of cross‐stream density gradients on the northern flank of the GS from an intense cooling (up to 4°C) in the Slope Water and (2) a westward intensification of the southern recirculation, which can also limit the formation of deeper mixed layers to the south of the GS near 70°W.
2169-9275
Jacobs, Z. L.
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Grist, J. P.
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Marsh, R.
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Sinha, B.
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Josey, S. A.
2252ab7f-5cd2-49fd-a951-aece44553d93
Jacobs, Z. L.
3b55fc85-c85e-442e-949c-8a71850a66e8
Grist, J. P.
ffea99af-f811-436f-9bac-5b02ba6dc00f
Marsh, R.
b22ef653-0671-46d5-bf81-21c0d6657974
Sinha, B.
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Josey, S. A.
2252ab7f-5cd2-49fd-a951-aece44553d93

Jacobs, Z. L., Grist, J. P., Marsh, R., Sinha, B. and Josey, S. A. (2020) The major role of air‐sea heat fluxes in driving interannual variations of Gulf Stream transport. Journal of Geophysical Research: Oceans, 125 (11), [e2019JC016004]. (doi:10.1029/2019JC016004).

Record type: Article

Abstract

The Gulf Stream (GS) is central to the global redistribution of heat due to the transport of large volumes of warm water from the tropics to high latitudes and the extreme ocean heat loss to the atmosphere. This study assesses the extent to which winter surface heat fluxes and wind stress curl can drive interannual variations of the full‐depth GS transport. Intensification of the GS has been observed (e.g., April 1977) immediately after a winter of frequent cold air outbreaks that led to a deepening of the mixed layer and subsequent steepening of meridional temperature gradients to the south of the GS. This forcing process is further investigated here using the ORCA12 hindcast (1978–2010) from the global, eddy‐resolving, ocean‐only Nucleus for European Modeling of the Ocean model in order to understand GS forcing mechanisms. Lagrangian analysis is also undertaken to examine the impact on the southern recirculation gyre. Results show that surface heat fluxes and wind stress curl can act in concert to effect year‐to‐year changes of up to 38% of the spring GS transport at 70°W. However, anomalous heat losses (∼200 Wm‐2) over the western Subtropical Gyre are found to be the dominant cause of peaks in GS transport via two mechanisms: (1) a strengthening of cross‐stream density gradients on the northern flank of the GS from an intense cooling (up to 4°C) in the Slope Water and (2) a westward intensification of the southern recirculation, which can also limit the formation of deeper mixed layers to the south of the GS near 70°W.

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2019JC016004 - Version of Record
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Accepted/In Press date: 5 October 2020
e-pub ahead of print date: 4 November 2020
Published date: November 2020

Identifiers

Local EPrints ID: 446343
URI: http://eprints.soton.ac.uk/id/eprint/446343
ISSN: 2169-9275
PURE UUID: e76da54a-e950-45c7-ab14-e7e1bc984cf6

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Date deposited: 05 Feb 2021 17:30
Last modified: 25 Nov 2021 18:43

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Contributors

Author: Z. L. Jacobs
Author: J. P. Grist
Author: R. Marsh
Author: B. Sinha
Author: S. A. Josey

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