Radium-226 and Ra-Ba relationships in Antarctic and Pacific waters

Abstract

Three 226Ra concentration profiles have been measured from the Antarctic south of New Zealand. These profiles show that the Ra concentration in the deep- and bottom-water region is fairly uniform at about 9.2 × 10 −14g/kg. However, south of the Antarctic Convergence, a slightly lower Ra concentration associated with higher salinity is found near the bottom where the Ross Sea Bottom Water spreads. In the Antarctic surface water, a gradual increase of radium concentration is observed from north to south across the Convergence. These features are closely correlated with the hydrographic data. The Ra concentration in the deep water increases from the North Atlantic through the Antarctic to the Pacific by a factor of three. In the Pacific, it increases from the southwest to the northeast. The trend of increase is similar to the abyssal water temperature, and shows that Ra, like heat, is injected continually into the deep water column as the water circulates. Ra and Ba are not linearly correlated over the entire ocean. The Ra/Ba ratio is not constant, and tends to increase from the surface water to the bottom water due to different input mechanisms for these two elements in the ocean.