Barium at Geosecs III in the southwest Pacific

Abstract

A detailed, highly precise barium profile has been measured at Geosecs III, off Tonga, in the southwest Pacific. There is a smooth increase from the surface values of 4.7 μg/kg to a deep maximum of 18.4 μg/kg at 2.974 km. Below this maximum there is an abrupt decrease to 14.3 μg/kg in the deep Western Boundary Current. Comparison with published data shows recent Pacific and Antarctic barium profiles to be consistent within 2%. Model calculations do not require any in situ injection of barium (or of silicate or alkalinity) in the water column; the form of the profile can be explained by vertical diffusion and advection between horizontally advecting water masses. From the θ- S curve it appears that a minor core of higher salinity water, possibly derived from Ross Sea bottom water, or the North Atlantic deep water core in the Circumpolar Current, is present immediately above the deep Boundary Current.