Open AccessFrom the western boundary currents to the Pacific Equatorial Undercurrent: Modeled pathways and water mass evolutions
Author(s) -
Grenier Mélanie,
Cravatte Sophie,
Blanke Bruno,
Menkes Christophe,
KochLarrouy Ariane,
Durand Fabien,
Melet Angélique,
Jeandel Catherine
Publication year - 2011
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jc007477
Subject(s) - oceanography , boundary current , water mass , equator , geology , current (fluid) , lagrangian , southern hemisphere , antarctic intermediate water , climatology , latitude , ocean current , thermohaline circulation , north atlantic deep water , physics , geodesy , mathematical physics
The hydrological and geochemical properties of the waters constituting the Pacific Equatorial Undercurrent (EUC) determine the properties of the equatorial cold tongue. Understanding and quantifying the various EUC origins is therefore of prime importance. For this purpose, a high‐resolution (1/4°) interannual oceanic simulation was analyzed from the western tropical Pacific boundaries to 140°W, using a Lagrangian framework. Waters from the Low‐Latitude Western Boundary Currents (LLWBCs) transiting from Vitiaz Strait (the main contributor), from Solomon Strait, and via the Mindanao Current were identified as the principal sources to the EUC. Waters conveyed by the interior ocean off equator are negligible till 180°E. The LLWBCs' waters represent 87% of the EUC transport at 156°E out of which the New Guinea Coastal Undercurrent (NGCU) is as large as 47%. The EUC meridional distribution suggests that the waters originating from Solomon Strait and Mindanao Current mostly remain in the hemisphere from which they originate. Contrastingly, Vitiaz Strait waters are found in both hemispheres. The vertical EUC distribution shows that the lower layer of the EUC is mainly composed of Vitiaz Strait waters. Finally, the source transport distributions were characterized, at their origin and within the EUC, as a function of density. These distributions showed that waters flowing through Vitiaz Strait at densities higher than those of the EUC (down to σ θ = 27.2 kg m −3 ) undergo a diapycnal mixing and lighten during their journey to join the EUC. This lightening supports the suggestion that the NGCU is a major source for the EUC geochemical enrichment.