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Abyssal Circulation Driven By Near-Boundary Mixing: Water Mass Transformations and Interior Stratification

Drake, Henri F. and Ferrari, Raffaele and Callies, Jörn (2020) Abyssal Circulation Driven By Near-Boundary Mixing: Water Mass Transformations and Interior Stratification. Journal of Physical Oceanography, 50 (8). pp. 2203-2226. ISSN 0022-3670. https://resolver.caltech.edu/CaltechAUTHORS:20200716-085229115

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Abstract

The emerging view of the abyssal circulation is that it is associated with bottom-enhanced mixing, which results in downwelling in the stratified ocean interior and upwelling in a bottom boundary layer along the insulating and sloping seafloor. In the limit of slowly varying vertical stratification and topography, however, boundary layer theory predicts that these upslope and downslope flows largely compensate, such that net water mass transformations along the slope are vanishingly small. Using a planetary geostrophic circulation model that resolves both the boundary layer dynamics and the large-scale overturning in an idealized basin with bottom-enhanced mixing along a midocean ridge, we show that vertical variations in stratification become sufficiently large at equilibrium to reduce the degree of compensation along the midocean ridge flanks. The resulting large net transformations are similar to estimates for the abyssal ocean and span the vertical extent of the ridge. These results suggest that boundary flows generated by mixing play a crucial role in setting the global ocean stratification and overturning circulation, requiring a revision of abyssal ocean theories.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1175/JPO-D-19-0313.1DOIArticle
ORCID:
AuthorORCID
Ferrari, Raffaele0000-0003-1895-4294
Callies, Jörn0000-0002-6815-1230
Additional Information:© 2020 American Meteorological Society. Manuscript received 14 December 2019, in final form 2 June 2020. We thank Ali Mashayek, Laura Cimoli, Xiaozhou Ruan, Bryan Kaiser, and Ryan Holmes for insightful discussions about abyssal mixing layers. We are grateful for two reviewers whose feedback improved the manuscript. We acknowledge funding support from National Science Foundation Awards 6932401 and 6936732.
Funders:
Funding AgencyGrant Number
NSF6932401
NSF6936732
Subject Keywords:Abyssal circulation, Bottom currents, Boundary currents, Mixing, Bottom currents/bottom water, Boundary layer
Issue or Number:8
Record Number:CaltechAUTHORS:20200716-085229115
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200716-085229115
Official Citation:Drake, H. F., R. Ferrari, and J. Callies, 2020: Abyssal Circulation Driven by Near-Boundary Mixing: Water Mass Transformations and Interior Stratification. J. Phys. Oceanogr., 50, 2203–2226, https://doi.org/10.1175/JPO-D-19-0313.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104397
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:16 Jul 2020 16:06
Last Modified:28 Jul 2020 19:52

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