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

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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.