The University of Southampton
University of Southampton Institutional Repository

Meridional overturning circulation: stability and ocean feedbacks in a box model

Meridional overturning circulation: stability and ocean feedbacks in a box model
Meridional overturning circulation: stability and ocean feedbacks in a box model
A box model of the inter-hemispheric Atlantic meridional overturning circulation is developed, including a variable pycnocline depth for the tropical and subtropical regions. The circulation is forced by winds over a periodic channel in the south and by freshwater forcing at the surface. The model is aimed at investigating the ocean feedbacks related to perturbations in freshwater forcing from the atmosphere, and to changes in freshwater transport in the ocean. These feedbacks are closely connected with the stability properties of the meridional overturning circulation, in particular in response to freshwater perturbations. A separate box is used for representing the region north of the Antarctic circumpolar current in the Atlantic sector. The density difference between this region and the north of the basin is then used for scaling the downwelling in the north. These choices are essential for reproducing the sensitivity of the meridional overturning circulation observed in general circulation models, and therefore suggest that the southernmost part of the Atlantic Ocean north of the Drake Passage is of fundamental importance for the stability of the meridional overturning circulation. With this configuration, the magnitude of the freshwater transport by the southern subtropical gyre strongly affects the response of the meridional overturning circulation to external forcing. The role of the freshwater transport by the overturning circulation (M ov ) as a stability indicator is discussed. It is investigated under which conditions its sign at the latitude of the southern tip of Africa can provide information on the existence of a second, permanently shut down, state of the overturning circulation in the box model. M ov will be an adequate indicator of the existence of multiple equilibria only if salt-advection feedback dominates over other processes in determining the response of the circulation to freshwater anomalies. M ov is a perfect indicator if feedbacks other than salt-advection are negligible.
atlantic, meridional overturning circulation, stability, freshwater, salt-advection feedback, southern subtropical gyre
0930-7575
Cimatoribus, Andrea A.
1e20d92c-fae8-49f6-9561-b0bbae3a645a
Drijfhout, Sybren S.
a5c76079-179b-490c-93fe-fc0391aacf13
Dijkstra, Henk A.
9178b06d-9de5-4f02-b9ff-204b20620291
Cimatoribus, Andrea A.
1e20d92c-fae8-49f6-9561-b0bbae3a645a
Drijfhout, Sybren S.
a5c76079-179b-490c-93fe-fc0391aacf13
Dijkstra, Henk A.
9178b06d-9de5-4f02-b9ff-204b20620291

Cimatoribus, Andrea A., Drijfhout, Sybren S. and Dijkstra, Henk A. (2012) Meridional overturning circulation: stability and ocean feedbacks in a box model. Climate Dynamics. (doi:10.1007/s00382-012-1576-9).

Record type: Article

Abstract

A box model of the inter-hemispheric Atlantic meridional overturning circulation is developed, including a variable pycnocline depth for the tropical and subtropical regions. The circulation is forced by winds over a periodic channel in the south and by freshwater forcing at the surface. The model is aimed at investigating the ocean feedbacks related to perturbations in freshwater forcing from the atmosphere, and to changes in freshwater transport in the ocean. These feedbacks are closely connected with the stability properties of the meridional overturning circulation, in particular in response to freshwater perturbations. A separate box is used for representing the region north of the Antarctic circumpolar current in the Atlantic sector. The density difference between this region and the north of the basin is then used for scaling the downwelling in the north. These choices are essential for reproducing the sensitivity of the meridional overturning circulation observed in general circulation models, and therefore suggest that the southernmost part of the Atlantic Ocean north of the Drake Passage is of fundamental importance for the stability of the meridional overturning circulation. With this configuration, the magnitude of the freshwater transport by the southern subtropical gyre strongly affects the response of the meridional overturning circulation to external forcing. The role of the freshwater transport by the overturning circulation (M ov ) as a stability indicator is discussed. It is investigated under which conditions its sign at the latitude of the southern tip of Africa can provide information on the existence of a second, permanently shut down, state of the overturning circulation in the box model. M ov will be an adequate indicator of the existence of multiple equilibria only if salt-advection feedback dominates over other processes in determining the response of the circulation to freshwater anomalies. M ov is a perfect indicator if feedbacks other than salt-advection are negligible.

Full text not available from this repository.

More information

Published date: November 2012
Keywords: atlantic, meridional overturning circulation, stability, freshwater, salt-advection feedback, southern subtropical gyre
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 348334
URI: https://eprints.soton.ac.uk/id/eprint/348334
ISSN: 0930-7575
PURE UUID: 64dc115a-b1fa-42ca-ad99-396bad0d2ed2

Catalogue record

Date deposited: 12 Feb 2013 12:01
Last modified: 16 Jul 2019 21:43

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×