The vertical activity concentration distributions of the radium isotopes, 226 Ra and 228 Ra, which are useful as radiotracers, were obtained for the first time in the western Subarctic Pacific Gyre (WSAG). It was possible to detect short-lived 228 Ra present from the surface to 400 m depth by analyzing large seawater samples. Low 228 Ra and high 226 Ra activity concentrations in the surface layer in the WSAG were strongly infl...