Size Matters: Another Reason Why the Atlantic Is Saltier than the Pacific

TitleSize Matters: Another Reason Why the Atlantic Is Saltier than the Pacific
Publication TypeJournal Article
Year of Publication2017
AuthorsJones C.S, Cessi P
JournalJournal of Physical Oceanography
Volume47
Pagination2843-2859
Date Published2017/11
Type of ArticleArticle
ISBN Number0022-3670
Accession NumberWOS:000417674100012
Keywordsdeep; global ocean circulation; Meridional overturning circulation; model; north-atlantic; precipitation; thermohaline circulation; transport
Abstract

The surface salinity in the North Atlantic controls the position of the sinking branch of the meridional overturning circulation (MOC); the North Atlantic has higher salinity, so deep-water formation occurs there rather than in the North Pacific. Here, it is shown that in a 3D primitive equation model of two basins of different widths connected by a reentrant channel, there is a preference for sinking in the narrow basin even under zonally uniform surface forcing. This preference is linked to the details of the velocity and salinity fields in the "sinking'' basin. The southward western boundary current associated with the wind-driven subpolar gyre has higher velocity in the wide basin than in the narrow basin. It overwhelms the northward western boundary current associated with the MOC for wide-basin sinking, so freshwater is brought from the far north of the domain southward and forms a pool on the western boundary in the wide basin. The fresh pool suppresses local convection and spreads eastward, leading to low salinities in the north of the wide basin for wide-basin sinking. This pool of freshwater is much less prominent in the narrow basin for narrow-basin sinking, where the northward MOC western boundary current overcomes the southward western boundary current associated with the wind-driven subpolar gyre, bringing salty water from lower latitudes northward and enabling deep-water mass formation.

DOI10.1175/jpo-d-17-0075.1
Student Publication: 
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