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

提供资金用于利用三维原始方程数值模式对北极潮流垂直结构的成因进行过程研究。作为正压潮流的斜压潮汐的产生与陡峭的地形相互作用，在潮汐分量的临界纬度(潮汐频率和科里奥利频率相等)附近形成厚边界层，这两个过程的相互作用将被研究。这项提议的动机是，世界海洋内陆潮汐诱导混合的重要性已被证明，而且有观察表明，北极也发生了类似的过程，特别是在北极和北大西洋之间发生热量和淡水交换的海峡和航道。还有证据表明，潮汐是海冰变形的一个重要因素，包括平均开阔水域(铅)分数的增加以及随后的海洋热损失和冰的增长率。这项拟议的工作将研究斜压性如何提高平均铅分数相对于从正压模型中获得的深度平均潮流的值。这项工作的长期目标是：(1)阐明潮汐对北极大气环流、水文结构和海冰特征的真正贡献；(2)设计技术，在大气环流模式(GCM)中将这一贡献参数化，在该模式中，显式包括潮汐效应(横向约1公里，垂直约几米，时间步长短)所需的分辨率在可预见的未来仍是遥不可及的。

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.