抄録
New data on 228Ra and 226Ra concentrations in the northern North Pacific are presented. Due to upwelling in the northern latitudes, 226Ra concentration is twice as much as that of the mid Pacific. The trend in the variation of surface 226Ra and dissolved SiO2 concentrations appears to be the same in the Pacific and the Atlantic oceans. A map of 228Ra/226Ra activity ratio in the surface water of the Pacific Ocean was constructed based on our data and those in the literature. The high 228Ra/226Ra activity ratio follows the prevailing surface currents such as the Kuroshio and the California Currents with low values at the center of the subarctic and the mid North Pacific gyres. The map is useful to identify the fluvial, coastal and shelf influences in the surface open ocean.
