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The location of diapycnal mixing and the meridional overturning circulation

The location of diapycnal mixing and the meridional overturning circulation
The location of diapycnal mixing and the meridional overturning circulation
The large-scale consequences of diapycnal mixing location are explored using an idealized threedimensional model of buoyancy-forced flow in a single hemisphere. Diapycnal mixing is most effective in supporting a strong meridional overturning circulation (MOC) if mixing occurs in regions of strong stratification, that is, in the low-latitude thermocline where diffusion causes strong vertical buoyancy fluxes. Where stratification is weak, such as at high latitudes, diapycnal mixing plays little role in determining MOC strength, consistent with weak diffusive buoyancy fluxes at these latitudes. Boundary mixing is more efficient than interior mixing at driving the MOC; with interior mixing the planetary vorticity constraint inhibits the communication of interior water mass properties and the eastern boundary. Mixing below the thermocline affects the abyssal stratification and upwelling profile, but does not contribute significantly to the MOC through the thermocline or the ocean’s meridional heat transport. The abyssal heat budget is dominated by the downward mass transport of buoyant water versus the spread of denser water tied to the properties of deep convection, with mixing of minor importance. These results are in contrast to the widespread expectation that the observed enhanced abyssal mixing can maintain the MOC; rather, they suggest that enhanced boundary mixing in the thermocline needs to be identified in observations.
0022-3670
3578-3595
Scott, Jeffery R.
0a5b123f-280a-443e-b026-7a010bbe33b5
Marotzke, Jochem
b4b295a3-5568-4f63-94b6-6fa92ab27cf3
Scott, Jeffery R.
0a5b123f-280a-443e-b026-7a010bbe33b5
Marotzke, Jochem
b4b295a3-5568-4f63-94b6-6fa92ab27cf3

Scott, Jeffery R. and Marotzke, Jochem (2002) The location of diapycnal mixing and the meridional overturning circulation. Journal of Physical Oceanography, 32 (12), 3578-3595.

Record type: Article

Abstract

The large-scale consequences of diapycnal mixing location are explored using an idealized threedimensional model of buoyancy-forced flow in a single hemisphere. Diapycnal mixing is most effective in supporting a strong meridional overturning circulation (MOC) if mixing occurs in regions of strong stratification, that is, in the low-latitude thermocline where diffusion causes strong vertical buoyancy fluxes. Where stratification is weak, such as at high latitudes, diapycnal mixing plays little role in determining MOC strength, consistent with weak diffusive buoyancy fluxes at these latitudes. Boundary mixing is more efficient than interior mixing at driving the MOC; with interior mixing the planetary vorticity constraint inhibits the communication of interior water mass properties and the eastern boundary. Mixing below the thermocline affects the abyssal stratification and upwelling profile, but does not contribute significantly to the MOC through the thermocline or the ocean’s meridional heat transport. The abyssal heat budget is dominated by the downward mass transport of buoyant water versus the spread of denser water tied to the properties of deep convection, with mixing of minor importance. These results are in contrast to the widespread expectation that the observed enhanced abyssal mixing can maintain the MOC; rather, they suggest that enhanced boundary mixing in the thermocline needs to be identified in observations.

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More information

Published date: 2002
Additional Information: Submitted version (2001)

Identifiers

Local EPrints ID: 253
URI: http://eprints.soton.ac.uk/id/eprint/253
ISSN: 0022-3670
PURE UUID: e695d238-b65b-4d6d-8135-e20e0b1f3cec

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Date deposited: 10 Dec 2003
Last modified: 19 Nov 2021 16:58

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Contributors

Author: Jeffery R. Scott
Author: Jochem Marotzke

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