Variations in the equatorial countercurrent in the central Pacific

Abstract

Cruise 15 of the M.V. Hugh M. Smith consisted of four consecutive lines of oceanographic stations along 140°W longitude between 8°N and 7°S latitude. Geostrophic calculations show that during a five‐week period the maximum eastward velocity component in the Countercurrent progressively increased from 63 to 120 cm/sec and the volume of flow increased from 18.3 to 22.6 X 106 m3/sec.In spite of these short‐term variations, the Equatorial Countercurrent in the central Pacific is remarkably predictable in latitude and general physical characteristics.

The structure of the Pacific equatorial countercurrent

“…Op decrease in velocity in the thermocline and the tendency for the maximum velocity to occur near the middle of the mixed layer (Figs. 2 and 3) [Sverdrup, 1932;Jerlov, 1956;Austin, Stroup, and Rinkel, 1956; and others]. From a comparison of individual sections it would appear that the short-period changes in the surface currents as measured by the GEK are also approximately geostrophic (Fig.…”

Transports of the Pacific Equatorial Countercurrent

“…Montgomery and Stroup [1962] quote transports between 9 and 48 million m3/sec, and they state that it still remains unknown how the flow varies with season and longitude. Austin et al [1956] have shown that transports may vary considerably within a few weeks. '…”