A direct determination of the World Ocean barotropic circulation

Type Article
Date 2016-01
Language English
Author(s) De Verdiere Alain Colin1, Ollitrault Michel2
Affiliation(s) 1 : Univ Bretagne Occidentale, Lab Phys Oceans, Brest, France.
2 : IFREMER, Ctr Brest, Lab Phys Oceans, Plouzane, France.
Source Journal Of Physical Oceanography (0022-3670) (Amer Meteorological Soc), 2016-01 , Vol. 46 , N. 1 , P. 255-273
DOI 10.1175/JPO-D-15-0046.1
WOS© Times Cited 22
Abstract The time-mean Argo float displacements and the World Ocean Atlas 2009 temperature–salinity climatology are used to obtain the total, top to bottom, mass transports. Outside of an equatorial band, the total transports are the sum of the vertical integrals of geostrophic- and wind-driven Ekman currents. However, these transports are generally divergent, and to obtain a mass conserving circulation, a Poisson equation is solved for the streamfunction with Dirichlet boundary conditions at solid boundaries. The value of the streamfunction on islands is also part of the unknowns. This study presents and discusses an energetic circulation in three basins: the North Atlantic, the North Pacific, and the Southern Ocean. This global method leads to new estimations of the time-mean western Eulerian boundary current transports maxima of 97 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) at 60°W for the Gulf Stream, 84 Sv at 157°E for the Kuroshio, 80 Sv for the Agulhas Current between 32° and 36°S, and finally 175 Sv for the Antarctic Circumpolar Current at Drake Passage. Although the large-scale structure and boundary of the interior gyres is well predicted by the Sverdrup relation, the transports derived from the wind stress curl are lower than the observed transports in the interior by roughly a factor of 2, suggesting an important contribution of the bottom torques. With additional Argo displacement data, the errors caused by the presence of remaining transient terms at the 1000-db reference level will continue to decrease, allowing this method to produce increasingly accurate results in the future.
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