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The observed North Atlantic Meridional Overturning Circulation, its Meridional Coherence and Ocean Bottom Pressure

The observed North Atlantic Meridional Overturning Circulation, its Meridional Coherence and Ocean Bottom Pressure
The observed North Atlantic Meridional Overturning Circulation, its Meridional Coherence and Ocean Bottom Pressure
Analyses of meridional transport time series from the Rapid Climate Change–Meridional Overturning Circulation (RAPID MOC) array at 26°N and from Argo float and altimetry data at 41°N reveal that, at semiannual and longer time scales, the contribution from the western boundary dominates the variability of the North Atlantic meridional overturning circulation (MOC), defined as the transport in the upper 1000 m of the ocean. Because the variability of the western boundary contribution is associated with a geostrophic overturning, it is reflected in independent estimates of transports from gradient of ocean bottom pressure (OBP) relative to and below 1000 m on the continental slope of the western boundary at three nominal latitudes (26°, 39°, and 42.5°N). Time series of western meridional transports relative to and below 1000 m derived from the OBP gradient, or equivalently derived from the transport shear profile, exhibit approximately the same phase relationship between 26° and 39°–42.5°N as the western contribution to the geostrophic MOC time series do: the western geostrophic MOC at 41°N precedes the MOC at 26°N by approximately a quarter of an annual cycle, resulting in a zero correlation at this time scale. This study therefore demonstrates how OBP gradients on basin boundaries can be used to monitor the MOC and its meridional coherence.
0022-3670
517-537
Elipot, Shane
c298217e-deac-444a-bf05-ef02bc6dd923
Frajka-Williams, Eleanor
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Hughes, Chris
f7d4e979-a7f9-4b39-9423-b53da62b6f24
Willis, Joshua
488a9b3e-e1b4-4dd8-bac7-d24ca4e78a8c
Elipot, Shane
c298217e-deac-444a-bf05-ef02bc6dd923
Frajka-Williams, Eleanor
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Hughes, Chris
f7d4e979-a7f9-4b39-9423-b53da62b6f24
Willis, Joshua
488a9b3e-e1b4-4dd8-bac7-d24ca4e78a8c

Elipot, Shane, Frajka-Williams, Eleanor, Hughes, Chris and Willis, Joshua (2014) The observed North Atlantic Meridional Overturning Circulation, its Meridional Coherence and Ocean Bottom Pressure. Journal of Physical Oceanography, 44 (2), 517-537. (doi:10.1175/JPO-D-13-026.1).

Record type: Article

Abstract

Analyses of meridional transport time series from the Rapid Climate Change–Meridional Overturning Circulation (RAPID MOC) array at 26°N and from Argo float and altimetry data at 41°N reveal that, at semiannual and longer time scales, the contribution from the western boundary dominates the variability of the North Atlantic meridional overturning circulation (MOC), defined as the transport in the upper 1000 m of the ocean. Because the variability of the western boundary contribution is associated with a geostrophic overturning, it is reflected in independent estimates of transports from gradient of ocean bottom pressure (OBP) relative to and below 1000 m on the continental slope of the western boundary at three nominal latitudes (26°, 39°, and 42.5°N). Time series of western meridional transports relative to and below 1000 m derived from the OBP gradient, or equivalently derived from the transport shear profile, exhibit approximately the same phase relationship between 26° and 39°–42.5°N as the western contribution to the geostrophic MOC time series do: the western geostrophic MOC at 41°N precedes the MOC at 26°N by approximately a quarter of an annual cycle, resulting in a zero correlation at this time scale. This study therefore demonstrates how OBP gradients on basin boundaries can be used to monitor the MOC and its meridional coherence.

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Submitted date: September 2013
e-pub ahead of print date: November 2013
Published date: February 2014
Organisations: Physical Oceanography

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Local EPrints ID: 357093
URI: http://eprints.soton.ac.uk/id/eprint/357093
ISSN: 0022-3670
PURE UUID: 1a266a48-79f6-4dbc-9b2d-9612564122e6
ORCID for Eleanor Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838

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Date deposited: 19 Sep 2013 15:06
Last modified: 15 Mar 2024 03:35

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Contributors

Author: Shane Elipot
Author: Eleanor Frajka-Williams ORCID iD
Author: Chris Hughes
Author: Joshua Willis

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