The University of Southampton
University of Southampton Institutional Repository

The influence of diapycnal mixing on quasi-steady overturning circulation states in the Indian Ocean

Record type: Article

A regional general circulation model (GCM) of the Indian Ocean is used to investigate the influence of
prescribed diapycnal diffusivity (Kd) on quasi-steady states of the meridional overturning circulation
(MOC). The model has open boundaries at 35°S and 123°E where velocity, temperature, and salinity are
prescribed at each time step. The results suggest that quasi-steady overturning states in the Indian Ocean
are reached on centennial time scales. The size and structure of the MOC are controlled by the distribution
of Kd and the southern boundary conditions. The distribution of Kd required to support an overturning
circulation in the model interior of a magnitude equal to that prescribed at the southern boundary is
estimated using a 1D advection–diffusion balance in isopycnal layers. Implementing this approach, 70%–
90% of the prescribed deep inflow can be supported in quasi-steady state. Thus one is able to address the
systematic discrepancy between past estimates of the deep MOC based on hydrographic sections and those
based on GCM results. However, the Kd values required to support a substantial MOC in the model are
much larger than current observation-based estimates, particularly for the upper 3000 m. The two estimates
of the flow field near 32°S used to force the southern boundary imply a highly nonuniform distribution of
Kd, as do recent estimates of Kd based on hydrographic observations. This work highlights the need to
improve and implement realistic estimates of (nonuniform) Kd in ocean and coupled ocean–atmosphere
GCMs when investigating quasi-equilibrium model states.

Full text not available from this repository.


Palmer, M.D., Naveira Garabato, A.C., Stark, J.D., Hirschi, J. and Marotzke, J. (2007) The influence of diapycnal mixing on quasi-steady overturning circulation states in the Indian Ocean Journal of Physical Oceanography, 37, (9), pp. 2290-2304. (doi:10.1175/JPO3117.1).

More information

Published date: September 2007


Local EPrints ID: 37583
ISSN: 0022-3670
PURE UUID: dcdaae9d-6f11-4c5b-b85f-2c1ef32e9a83

Catalogue record

Date deposited: 24 May 2006
Last modified: 17 Jul 2017 15:42

Export record



Author: M.D. Palmer
Author: J.D. Stark
Author: J. Hirschi
Author: J. Marotzke

University divisions

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 supports OAI 2.0 with a base URL of

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.