Abstract. We analysed the spatiotemporal variations in the ¹³⁷Cs activity concentrations in global ocean surface seawater from 1956 to 2021 using the HAMGlobal2021: Historical Artificial radioactivity database in Marine environment, Global integrated version 2021. The global ocean was divided into 37 boxes. The 0.5-yr average value of ¹³⁷Cs in each box, except in the northern North Atlantic Ocean and its marginal sea, decreased exponentially in 1970–2010, immediately before the Fukushima Nuclear Power Plant (F1NPS) accident. The ¹³⁷Cs inventory in the surface mixed layer in 1970 was estimated to be 187 ± 26 PBq. In 1975 and 1980, the ¹³⁷Cs inventory increased to 201 ± 28 and 210 ± 12 PBq, respectively, due to direct discharge from the Sellafield and La Hague nuclear fuel reprocessing plants. In 2011, the ¹³⁷Cs inventory in the global ocean mixed layer increased to 48.1±12.1 PBq compared to that before the F1NPS accident, in which the contribution from the accident was estimated to be approximately 15.5 ± 3.9 PBq. The distribution and variation in ¹³⁷Cs in global surface seawater reflect basin-scale or global-scale transport. Mass balance analysis indicates that ¹³⁷Cs deposited by the global fallout in the western North Pacific Ocean moves to the eastern North Pacific Ocean. Subsequently, ¹³⁷Cs is transported southwards, followed by westwards transport in the subtropical and equatorial Pacific Ocean and inflow into the Indian Ocean via the Indonesian Archipelago. The longer apparent half residence times in the Indonesian Archipelago (36.7 years from 1973 to 1997), South Atlantic Ocean (37.0 years from 1973 to 2004), and Central Atlantic Ocean (43.5 years from 1993 to 2016) also support the interpretation of the global-scale transport of ¹³⁷Cs from the western North Pacific Ocean to the Indian and Atlantic Oceans. In the northern North Atlantic Ocean and its marginal sea, ¹³⁷Cs discharged from nuclear reprocessing plants is transported to the North Sea, Barents Sea and coast of Norway, and Arctic Ocean on a decadal scale. The dataset is available at http://dx.doi.org/10.34355/CRiED.U.Tsukuba.00085 (Aoyama, 2021), http://dx.doi.org/10.34355/Ki-net.KANAZAWA-U.00149 (Inomata and Aoyama, 2022a), http://dx.doi.org/10.34355/Ki-net.KANAZAWA-U.00150 (Inomata and Aoyama, 2022b), http://dx.doi.org/10.34355/Ki-net.KANAZAWA-U.00151 (Inomata and Aoyama, 2022c).

中文翻译：

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使用沉积在全球海洋中的 137C 作为化学示踪剂评估 1956 年至 2021 年表层海水的输送

摘要。^{我们使用 HAMGlobal2021：海洋环境中的历史人工放射性数据库，全球综合版 2021，分析了 1956 年至 2021 年全球海洋表层海水中137} Cs 活度浓度的时空变化。全球海洋分为 37 个方框。除北大西洋北部及其边缘海外，每个箱子中¹³⁷ Cs的 0.5 年平均值在 1970-2010 年福岛核电站 (F1NPS) 事故前夕呈指数下降。1970 年地表混合层中的¹³⁷ Cs 存量估计为 187 ± 26 PBq。1975 年和 1980 年，¹³⁷由于 Sellafield 和 La Hague 核燃料后处理厂的直接排放，Cs 库存分别增加到 201 ± 28 和 210 ± 12 PBq。2011年全球海洋混合层¹³⁷ Cs存量较F1NPS事故前增加至48.1±12.1 PBq，其中事故贡献估计约为15.5±3.9 PBq。¹³⁷ Cs在全球表层海水中的分布和变化反映了流域尺度或全球尺度的输运。质量平衡分析表明，全球沉降物沉积在北太平洋西部的¹³⁷ Cs 向北太平洋东部移动。随后，¹³⁷Cs向南输送，随后在亚热带和赤道太平洋向西输送，经印度尼西亚群岛流入印度洋。印度尼西亚群岛（1973 年至 1997 年 36.7 年）、南大西洋（1973 年至 2004 年 37.0 年）和大西洋中部（1993 年至 2016 年 43.5 年）的表观半停留时间较长，也支持对全球¹³⁷ Cs 从北太平洋西部到印度洋和大西洋的规模传输。在北大西洋北部及其边缘海，¹³⁷从核后处理厂排放的 Cs 在年代际尺度上被输送到北海、巴伦支海和挪威海岸，以及北冰洋。数据集可在 http://dx.doi.org/10.34355/CRiED.U.Tsukuba.00085（Aoyama，2021 年）、http://dx.doi.org/10.34355/Ki-net.KANAZAWA-U 获取。 00149（Inomata 和 Aoyama，2022a），http://dx.doi.org/10.34355/Ki-net.KANAZAWA-U.00150（Inomata 和 Aoyama，2022b），http://dx.doi.org/10.34355/ Ki-net.KANAZAWA-U.00151（Inomata 和 Aoyama，2022c）。