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Published in

American Meteorological Society, Journal of Physical Oceanography, 7(24), p. 1666-1679, 1994

DOI: 10.1175/1520-0485(1994)024<1666:dooteb>2.0.co;2

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Direct Observations of the Ekman Balance at 10°N in the Pacific

Journal article published in 1994 by Susan Wijffels ORCID, Eric Firing, Harry Bryden
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

The wind-driven transport and velocity structure are estimated from direct current measurements and geostrophic shears along a transpacific section at 10°N. The total velocity field is dominated by the North Equatorial Current and its eddies, while the shear features near-inertial oscillations and a wind-driven current spiral. The section-averaged cross-track ageostrophic shear can be approximated as a slab layer 30-40 m thick with a velocity of 0.05 m s-1 overlying a sheared layer in which the velocity goes to zero below 80 m. The resulting zonally integrated ageostrophic mass transport is 62 (±10) × 109 kg s-1 northward, similar to the estimate of 52 (±10) × 109 kg s-1 predicted by the Ekman balance using winds measured from the ship. Climatological winds yield similar transports. The zonally averaged velocity relative to the top of the thermocline forms a clockwise spiral, decaying with depth. As has been found at higher latitudes, this mean wind-driven spiral results from the diurnal cycling of the mixed layer depth. -Authors