Exploratory observations of abyssal currents in the South Atlantic near Vema Channel

Author： Schmitz William J. Hogg Nelson G.

Publisher： Sears Foundation for Marine Research

ISSN： 1543-9542

Source： Journal of Marine Research, Vol.41, Iss.3, 1983-08, pp. : 487-510

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Abstract

Vema Channel (nominal location 30S, 40W) is a major passage for the flow of Antarctic Bottom Water on its way northward from the Argentine Basin to the Brazil Basin. New data based on approximately year-long current meter deployments at abyssal depths yield mean or time-averaged kinetic energies as strong as 240 cm²s⁻², and eddy kinetic energies from 8 to 40 cm²s⁻². We observe a persistent northward flow of AABW with maximum speed near 40 cm s⁻¹, as is found at abyssal depths in the vicinity of the GulfStream. The highest value of mean kinetic energy in Vema Channel (240 cm² s⁻²) is much larger than that (∼20 cm² s⁻²) found in the flow of Antarctic Bottom Water near the Ceara Rise, and comparable to values of 220 cm² s⁻² for the southward flow of North Atlantic Deep Water on the Blake-Bahama Outer Ridge. Existing observations of mean kinetic energy at locations near the GulfStream System do not exceed 100 cm² s⁻² in the abyssal depth range.Eddy kinetic energies of 8 cm⁻² s⁻² are comparable to estimates (at similar depths) from areas at roughly equivalent latitudes, like MODE (Mid-Ocean Dynamics Experiment, nominal location 28N, 70W). However, abyssal kinetic energies as large as 40 cm² s⁻² are normally found only near strong current regimes, in contrast to values of roughly 1 cm² s⁻² in the ocean interior. Values of 18 to 64 cm² s⁻² have been observed near the southward flow of North Atlantic Deep Water on and adjacent to the Blake-Bahama Outer Ridge near 30N, and up to 20 cm² s⁻² in the flow of Antarctic Bottom Water over the Ceara Rise. The strongest abyssal eddy field yet observed, ∼100 to 150 cm² s⁻², occurs near the GulfStream.