A Modeling Study of the Vertical Structure of Arctic Ocean Tidal Currents: Baroclinic Tides and Critical Latitude Effects

为利用三维原始方程数值模型对北极潮流垂直结构成因进行过程研究提供了资金。斜压潮汐的产生是由于正压潮流与陡峭地形的相互作用，在潮汐成分的临界纬度（潮汐和科里奥利频率相等）附近厚边界层的发展，以及这两个过程的相互作用将被研究。提出这一建议的原因是，世界海洋内部由潮汐引起的混合现象的重要性已得到证实，而且观测显示，类似的过程也发生在北极，特别是在北极和北大西洋之间发生热和淡水交换的海峡和通道。也有证据表明，潮汐是海冰变形的一个重要因素，包括平均开放水域（铅）比例的增加以及随后的海洋热损失和冰的增长速度。所提出的工作将研究斜压性如何提高相对于从正压模式中使用深度平均潮汐流获得的值的平均铅分数。这项工作的长期目标是：(i)阐明潮汐对北极环流、水文结构和海冰特征的真正贡献；（ii）设计在一般环流模式（GCMs）中参数化这种贡献的技术，因为在可预见的未来，明确包括潮汐效应（横向约1公里，垂直几米和短时间步长）所需的分辨率仍然无法达到。

Funds are provided for a process study of the causes of the vertical structure of tidal currents in the Arctic using a 3-D primitive equation numerical model. The generation of baroclinic tides as barotropic tidal currents interact with steep topography, the development of thick boundary layers near a tidal constituent's critical latitude (where the tidal and Coriolis frequencies are equal), and the interaction of these two processes will be studied. The proposal is motivated by the demonstrated importance of tide-induced mixing in the World Ocean's interior, and by observations showing that similar processes occur in the Arctic,particularly in the straits and passages where heat and fresh water exchanges between the Arctic and North Atlantic occur. There is, also, evidence that tides are an important contributor to sea ice deformation including an increase in mean open water (lead) fraction and subsequent ocean heat loss and ice growth rates. The proposed work will investigate how baroclinicity enhances the mean leadfraction relative to the value obtained using depth-averaged tidal currents from barotropic models. The long-term goals of this work are to: (i) elucidate the tide's true contribution to the general circulation, hydrographic structure, and sea-ice characteristics of the Arctic; and (ii) devise techniques to parameterize this contribution in general circulation models (GCMs) where the resolution required for explicit inclusion of tidal effects (~1 km laterally, a few m in the vertical, and short time steps) will remain out of reach for the foreseeable future.