Following the Trail of Fukushima Tracers: Transport Pathways, Spreading and Mixing in the North Pacific

该项目的目标是利用2011年一次性释放的放射性同位素所提供的信息，特别是来自日本北部福岛第一核电站的铯(137Cs，~30年半衰期和134Cs，~2年半衰期)和锶(90锶，29年半衰期)，以更好地了解北太平洋水的路径、混合和输送。个人资料调查将分析2013年CLIVAR 30°N纬向断面的表层和剖面样本；并获取和分析2015年经向CLIVAR线西经150°处的上层水柱铯(Cs)和锶(Sr)剖面。这些观测，连同过去两年半收集的海洋铯和碘数据，将与卫星、漂浮物和浮游物观测、海洋模型分析和大气模拟结果相结合，以阐明自同位素释放以来4年期间将发生的水平扩散和垂直混合的细节。知识价值：铯和锶的观测和分析，特别是在与其他观测特性和数值模式相结合时，将提供一个独特的窗口，从这个窗口观察北太平洋内水团的形成和变化的时间尺度。这项调查旨在更好地了解在北太平洋释放和沉积的福岛放射性同位素的命运--它们被引入后2到4年的距离和深度。尽管海洋中的这种放射性水平并不被认为是危险的，但它在哪里以及到底有多少的问题仍然是生活在北太平洋海岸和在其水域捕鱼的人特别感兴趣的话题。与此同时，有人问这种独特的示踪剂能对海洋平流和扩散过程说些什么。PI打算利用观测结果来改进他们自己的模型模拟，并验证预测美国西海岸水域放射性同位素污染的不同社区建模工作。关于福岛同位素混合和扩散的可变性得出的结论将与那些试图了解物理过程对生物生产、营养循环和二氧化碳吸收的作用有关，因为这套真正独特的十年尺度示踪剂将揭示盆地规模的上层海洋混合和平流过程的速率和模式。广泛的影响：通过多示踪分析最大限度地提高拟议样本的科学效益，以及与其他研究福岛衍生同位素的实验室建立更紧密的联系，并支持年轻研究人员的教育，P.Masque的巴塞罗那大学实验室的一名研究生将被邀请在世界卫生组织工作两个学期，以测量北太平洋水文样本中的90Sr活度。在该项目的第一个暑假期间，将邀请一名世界卫生组织暑期学生(三年级本科生)参加该项目的观测部分，通过分析水文学、漂浮剖面或测高。为了进一步加强与日本同事的国际合作，并协助开发降低检测极限的新方法，青山先生将应邀从东京访问世界卫生组织同位素实验室。此外，还将创建一个公共网站，将结果张贴在网站上。该小组的所有成员都打算通过以下方案继续开展不同层面的外联活动：利用科学博览会项目的巡航观察对当地初中生和高中生进行辅导、课堂访问和公共宣传演讲、访谈和讲座。

The goal of this project is to use the information provided by the one-time, 2011 release of radio isotopes, and in particular, cesium (137Cs, ~30-year half-life and 134Cs, ~2-year half-life) and strontium (90Sr, 29-year half-life) from the Dai-ichi Fukushima nuclear power plants in northern Japan to better understand the pathways, mixing and transport of water in the North Pacific Ocean. The PIs will analyze surface & profile samples from the 2013 zonal CLIVAR 30°N transect for strontium; and obtain and analyze upper water column cesium (Cs) and strontium (Sr) profiles along the 2015 meridional CLIVAR line at 150°W. These observations, along with ocean cesium and iodine data collected over the last two and a half years, will be combined with satellite, drifter and float observations, an ocean model analysis and atmospheric modeling results to illuminate the details of the horizontal spread and vertical mixing that will have taken place over the 4 year period since the release of the isotopes. Intellectual Merit: The Cs and Sr observations and analysis, particularly when combined with other observed properties and numerical models, will provide a unique window from which to view water mass formation and the temporal scale of transformation within the North Pacific. This investigation seeks to better understand the fate of Fukushima radioisotopes released and deposited in the North Pacific -- how far and how deeply they range 2 to 4 years after being introduced. Although levels of this radioactivity in the ocean are not considered dangerous, the questions of where it is, and exactly how much there is, remain topics of particular interest to those who live on North Pacific shores and fish in its waters. At the same time it is asked what this unique tracer can say about ocean advection and diffusion processes. The PIs intend to use the results from the observations to improve their own model simulation and to validate disparate community modeling efforts forecasting radioisotope contamination of waters off the US west coast. Conclusions drawn concerning the variability in the mixing and spreading of Fukushima isotopes will be relevant to those seeking to understand the role of physical processes on biological production, nutrient cycling and CO2 uptake as this truly unique set of decadal-scale tracers will reveal the rates and patterns of basin-scale upper-ocean mixing and advective processes.Broader Impacts: To maximize the scientific benefit of the proposed samples through multi-tracer analysis, as well as to develop stronger ties with other labs working with Fukushima derived isotopes, and support the education of a young researcher, a graduate student from P. Masque's University of Barcelona lab will be invited to spend two semesters at WHOI to measure 90Sr activities in the North Pacific hydrographic samples. During the 1st summer of the project, a WHOI summer student fellow (3rd year undergraduate) will be invited to participate in the observational component of the project through analyses of hydrography, float profiles or altimetry. To further international collaboration with Japanese colleagues and assist in the development of new methods for reducing detection limits M. Aoyama will be invited to visit the WHOI isotope lab from Tokyo. In addition, a public website will be created on which results will be posted. All members of the group intend to engage in outreach at various levels through their continued work with the following programs: mentoring of local middle and high school students using cruise observations for science fair projects, classroom visits and public outreach presentations, interviews and talks.