Detection of a deep boundary current in the Western South Pacific

Abstract

FROM the distribution of salinity, temperature, oxygen and radio-carbon observed in the deep oceans (deeper than 2,000 m) of the world, it seems that all the deep water in both the North and South Pacific comes from other oceans, entering the Pacific from the south. The Tasman Sea is closed to the north at depths greater than 3,000 m, so that any deep current reaching into the North Pacific must lie east of New Zealand. The simple linear geostrophic theory of the abyssal circulation proposed by Stommel and Arons1,2 requires that the source water, "after passing south of New Zealand, flows northward into the Pacific Ocean as a narrow western boundary current along the Tonga-Kermadec Trench". It seems surprising that the source water should move in such a narrow current when it has the full width of the South Pacific within which it might flow, but the dynamics demands weak, southward geostrophic flow over most of the width of the South Pacific, and permits northward flow only in a higher-order boundary current. We are not at all certain that such simple dynamics do prevail, and the data have so far been insufficient to reveal the existence or non-existence of this current. © 1968 Nature Publishing Group.