Thompson, Andrew F. and Stewart, Andrew L. and Bischoff, Tobias (2016) A Multibasin Residual-Mean Model for the Global Overturning Circulation. Journal of Physical Oceanography, 46 (9). pp. 2583-2604. ISSN 0022-3670. http://resolver.caltech.edu/CaltechAUTHORS:20161020-102632202
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The ocean’s overturning circulation is inherently three-dimensional, yet modern quantitative estimates of the overturning typically represent the subsurface circulation as a two-dimensional, two-cell streamfunction that varies with latitude and depth only. This approach suppresses information about zonal mass and tracer transport. In this article, the authors extend earlier, zonally averaged overturning theory to explore the dynamics of a “figure-eight” circulation that cycles through multiple basins. A three-dimensional residual-mean model of the overturning circulation is derived and then simplified to a multibasin isopycnal box model to explore how stratification and diabatic water mass transformations in each basin depend on the basin widths and on deep and bottom-water formation in both hemispheres. The idealization to multiple, two-dimensional basins permits zonal mass transport along isopycnals in a Southern Ocean–like channel, while retaining the dynamical framework of residual-mean theory. The model qualitatively reproduces the deeper isopycnal surfaces in the Pacific Basin relative to the Atlantic. This supports a transfer of Antarctic Bottom Water from the Atlantic sector to the Pacific sector via the Southern Ocean, which subsequently upwells in the northern Pacific Basin. A solution for the full isopycnal structure in the Southern Ocean reproduces observed stratification differences between Atlantic and Pacific Basins and provides a scaling for the diffusive boundary layer in which the zonal mass transport occurs. These results are consistent with observational indications that North Atlantic Deep Water is preferentially transformed into Antarctic Bottom Water, which undermines the importance of an adiabatic, upper overturning cell in the modern ocean.
|Additional Information:||© 2016 American Meteorological Society. Manuscript received 23 October 2015, in final form 27 May 2016. We acknowledge helpful discussions with Jess Adkins, Paola Cessi, Raffaele Ferrari, Malte Jansen, C. Spencer Jones, John Marshall, Louis-Phillipe Nadeau, and Lynne Talley. AFT gratefully acknowledges support from NSF Grant OCE-1235488. ALS acknowledges support from NSF Grant OCE-1538702.|
|Subject Keywords:||Geographic location/entity; Atlantic Ocean; Pacific Ocean; Southern Ocean; Circulation/ Dynamics; Abyssal circulation; Ocean circulation; Ocean dynamics|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||20 Oct 2016 21:52|
|Last Modified:||20 Oct 2016 21:52|
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