Pathways into the Pacific Equatorial Undercurrent: A Trajectory Analysis

Paul J. Goodman Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York

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Wilco Hazeleger Royal Netherlands Meteorological Institute, De Bilt, Netherlands

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Pedro de Vries Royal Netherlands Meteorological Institute, De Bilt, Netherlands

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Mark Cane Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York

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Abstract

A time-dependent trajectory algorithm is used to determine the sources of the Pacific Ocean Equatorial Undercurrent (EUC) in a global climate model with ¼° (eddy permitting) resolution and forced with realistic winds. The primary sources and pathways are identified, and the transformation of properties in temperature/salinity space is explored. An estimate for the quantity of recirculation, a notoriously difficult property to estimate from observational data, is given. Over two-thirds of the water in the Pacific EUC at 140°W originates south of the equator; 70% of the EUC is ventilated outside of the Tropics (poleward of 13°S or 10°N): three-quarters of these extratropical trajectories travel through the western boundary currents between their subduction and incorporation into the EUC, and one-fifth of the extratropical trajectories enter and leave the tropical band at least once before entering the EUC.

* Lamont-Doherty Earth Observatory Contribution Number 6803

Corresponding author address: Paul J. Goodman, IMCS/Rutgers University, 71 Dudley Rd., New Brunswick, NJ 08901. Email: paulg@imcs.rutgers.edu

Abstract

A time-dependent trajectory algorithm is used to determine the sources of the Pacific Ocean Equatorial Undercurrent (EUC) in a global climate model with ¼° (eddy permitting) resolution and forced with realistic winds. The primary sources and pathways are identified, and the transformation of properties in temperature/salinity space is explored. An estimate for the quantity of recirculation, a notoriously difficult property to estimate from observational data, is given. Over two-thirds of the water in the Pacific EUC at 140°W originates south of the equator; 70% of the EUC is ventilated outside of the Tropics (poleward of 13°S or 10°N): three-quarters of these extratropical trajectories travel through the western boundary currents between their subduction and incorporation into the EUC, and one-fifth of the extratropical trajectories enter and leave the tropical band at least once before entering the EUC.

* Lamont-Doherty Earth Observatory Contribution Number 6803

Corresponding author address: Paul J. Goodman, IMCS/Rutgers University, 71 Dudley Rd., New Brunswick, NJ 08901. Email: paulg@imcs.rutgers.edu

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