To understand complicated current systems, we examined the ²²⁸Ra activities and ²²⁸Ra/²²⁶Ra activity ratios in 290 surface waters in the southwestern Sea of Japan from 2015 to 2020. The ²²⁸Ra/²²⁶Ra ratios exhibited large seasonal variation, showing higher ratios in July–September (1.5–2.5) than in other months. The fractions of the Kuroshio Current from the Pacific Ocean (f_K), based on the ²²⁸Ra activities and salinity, in the western part of the study area were lowest in July after the steep decrease in the f_K from May to July (0.95–0.6). This is due to the water mixing ratio of the East China Sea continental shelf side waters to the Kuroshio Current, reflecting the seasonal change and local water circulations.

为了理解复杂当前系统中，我们研究了^228个太阳神活动和²²⁸太阳神/ ²²⁶在290个地面水太阳神活性比在日本从2015年至2020年的西南海的²²⁸太阳神/ ²²⁶太阳神比率表现出大的季节变化，表现出更高的比例7月至9月（1.5-2.5）比其他月份大。基于²²⁸ Ra的活度和盐度，来自研究区西部的太平洋黑潮潮流（f _K）的分数在f _K急剧下降之后的7月最低。从5月到7月（0.95-0.6）。这是由于东海大陆架侧水与黑潮之间的水混合比，反映了季节变化和局部水循环。