Simonsen Magne, Saetra Øyvind, Isachsen Pål Erik, Lind Ole Christian, Skjerdal Hilde Kristin, Salbu Brit, Heldal Hilde Elise, Gwynn Justin P
Norwegian Meteorological Institute, P.O. Box 43, Blindern, NO-0313 Oslo, Norway; Centre of Environmental Radioactivity CoE, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, N-1432 Ås, Norway.
Norwegian Meteorological Institute, P.O. Box 43, Blindern, NO-0313 Oslo, Norway.
J Environ Radioact. 2017 Oct;177:100-112. doi: 10.1016/j.jenvrad.2017.06.002. Epub 2017 Jun 20.
In the present work, numerical models are used to study the fate of the Tc discharges from Sellafield with a specific focus on the role of mesoscale eddy and tidal advection on the transport and dispersion of this radionuclide. Transport estimates are made with an ocean model that resolves a large part of the ocean mesoscale eddy field and also includes tides. Equivalent estimates are also computed with another model in which these processes are either absent or parametrized. Comparison with field observations shows that the coarse-resolution model can reproduce the general features of the observed time-space Tc distribution if the diffusivity in its eddy parametrization scheme is suitably chosen. However, the eddy-permitting simulations capture regional details better and show an overall higher prediction skill, with the model predictions agreeing with the observations within a factor of two to four. The importance of tidal advection is investigated by comparing transport in the eddy-permitting model when this is run either with tides included or with tides filtered out. The results point to systematic Lagrangian tidal drift in the Irish Sea and the North Sea that eventually impacts the Tc activity concentration levels also far downstream.
在本研究中，使用数值模型来研究塞拉菲尔德排放的锝的归宿，特别关注中尺度涡旋和潮汐平流在这种放射性核素的输运和扩散中所起的作用。利用一个解析了大部分海洋中尺度涡旋场并包含潮汐的海洋模型进行输运估算。还使用另一个模型计算了等效估算值，在该模型中这些过程要么不存在，要么进行了参数化处理。与实地观测结果的比较表明，如果粗分辨率模型涡旋参数化方案中的扩散率选择得当，它可以再现观测到的锝时空分布的一般特征。然而，允许涡旋的模拟能更好地捕捉区域细节，并且总体预测技能更高，模型预测结果与观测值在二到四倍的范围内相符。通过比较允许涡旋模型在包含潮汐或滤除潮汐情况下的输运情况，研究了潮汐平流的重要性。结果表明，爱尔兰海和北海存在系统性的拉格朗日潮汐漂移，最终也会影响到下游很远地区的锝活度浓度水平。
