Prognostic Modeling Studies of the Keweenaw Current in Lake Superior. Part II: Simulation

Jianrong Zhu State Key Laboratory for Estuarine and Coastal Research, East China Normal University, Shanghai, China

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Changsheng Chen Department of Marine Sciences, University of Georgia, Athens, Georgia

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Elise Ralph Great Lakes Observatory, University of Minnesota, Duluth, Minnesota

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Sarah A. Green Department of Chemistry, Michigan Technological University, Houghton, Michigan

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Judith Wells Budd Department of Geological Engineering and Sciences, Michigan Technological University, Houghton, Michigan

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Frank Y. Zhang Department of Biology, Kean University, Union, New Jersey

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Abstract

The Keweenaw Current, observed along the coast of the Keweenaw Peninsula in Lake Superior during July 1973, was simulated using a 3D, nonorthogonal coordinate transformation, primitive equation coastal ocean model. The model domain covered the entire lake with a high resolution of 250–600 m in the cross-shelf direction and 4–6 km in the alongshelf direction along the peninsula. The model was initialized using the monthly averaged temperature field observed in June 1973 and was run prognostically with synoptic wind forcing plus monthly averaged heat flux. Good agreement was found between model-predicted and observed currents at buoy stations near Eagle Harbor. Comparison of the model results with and without inclusion of heat flux suggested that combined wind and heat fluxes played a key role in the intensification of the Keweenaw Current during summer months. The model-predicted relatively strong near-inertial oscillations occurred episodically under conditions of a clockwise-rotating wind. These oscillations intensified at the surface, were weak near the coast, and increased significantly offshore.

Corresponding author address: Dr. Changsheng Chen, Department of Marine Sciences, University of Georgia, Athens, GA 30602.

Email: chen@whale.marsci.uga.edu

Abstract

The Keweenaw Current, observed along the coast of the Keweenaw Peninsula in Lake Superior during July 1973, was simulated using a 3D, nonorthogonal coordinate transformation, primitive equation coastal ocean model. The model domain covered the entire lake with a high resolution of 250–600 m in the cross-shelf direction and 4–6 km in the alongshelf direction along the peninsula. The model was initialized using the monthly averaged temperature field observed in June 1973 and was run prognostically with synoptic wind forcing plus monthly averaged heat flux. Good agreement was found between model-predicted and observed currents at buoy stations near Eagle Harbor. Comparison of the model results with and without inclusion of heat flux suggested that combined wind and heat fluxes played a key role in the intensification of the Keweenaw Current during summer months. The model-predicted relatively strong near-inertial oscillations occurred episodically under conditions of a clockwise-rotating wind. These oscillations intensified at the surface, were weak near the coast, and increased significantly offshore.

Corresponding author address: Dr. Changsheng Chen, Department of Marine Sciences, University of Georgia, Athens, GA 30602.

Email: chen@whale.marsci.uga.edu

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