On the barium data from the Atlantic GEOSECS expedition

Abstract

Barium profiles at the Atlantic stations of the Geochemical Ocean Sections (GEOSECS) Program are remarkably similar to those for silicate and alkalinity. In nutrient depleted surface waters barium ranges between 36 and 44 nm kg −1: the Arctic overflows have values between 44 and 49 nm kg −1 and the Antarctic Bottom Water 100 to 106 nm kg −1. Both barium and silica behave non-conservatively in basins with restricted circulation—the Greenland and Norwegian seas and the Angola Basin—with anomalies of up to 1, 2 and 7 nm Ba kg −1, respectively. There is extensive in situ production of silica and barium in the bottom waters of the Weddell Sea Basin, the silica anomaly ranging up to 35 μm kg −1 and that for barium to 15 nm kg −1. Barium behaves uniquely only in the upper waters. At tropical and temperate latitudes there is commonly a minimum of several nannomoles per kilogram in the uppermost thermocline, often associated with the high salinity core of the Sub-Tropical Underwater. In the Circumpolar Current the depletion in surface silica is associated with only a minor reduction in barium. The values at <5 μm Si kg −1 are about 30 nm kg −1 higher than those at lower latitudes. The important question of the removal mechanism is not resolved from the profile data.