An interdisciplinary comprehensive survey was conducted in middle and late June 2003 with the Multi- arameter Environmental Monitoring System YSI 6600 and water sample analysis in the sea off the Changjiang River mouth. The Changjiang diluted water (CDW) extended offshore with a bimodal structure during the observation, one extending toward the southeast, the other toward the northeast. The main axis of the CDW extended toward the northeast. A severe red tide with wide spatial extent and brown water color happened. Chlorophyll-a (Chl-a) distribution near the Changjiang River mouth also presented a bimodal structure, and its position and shape were roughly consistent with the extension of the CDW. Water sample analysis indicated that the serious eutrophication produced by the huge amount of nutrient load via the Changjiang River was the main cause of red tide bloom. The dominant algal specie at the most measurement stations was skeletonema costatum. There existed three centers of higher Chl-a concentration, locating at (122.45˚E, 31.5˚N), (122.4˚E, 30.8˚N) and (123.25˚E, 30.0˚N), respectively. The red tide at (122.45˚E, 31.5˚N) was located in the major modal of CDW and higher turbid seawater, its dominant algal specie was prorocentrum dentatum with density 2.23×106ind/L. The red tide at (122.4˚E, 30.8˚N) was located in the second modal of CDW and lower turbid seawater, its dominant algal specie was skeletonema costatum with density 1.0×107ind/L. The dominant algal specie at (123.25˚E, 30.0˚N) was Heterocapsa circularisquama horiguchi with density 2.0×106ind/L, which was found for the first time forming red tide in the sea off the Changjiang River mouth.

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 250-600m in the cross-shelf direction and 4-6km 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.

The formation and evolution of the Keweenaw Current in Lake Superior were examined using a nonorthogonalcoordinate primitive equation numerical model. The model was initialized by the monthly averaged temperature field observed in June and September 1973 and run prognostically under different forcing conditions with and without winds. As a Rossby adjustment problem, the model predicted the formation of a well-defined coastal current jet within an inertial period of 16.4h after the current field adjusted to the initial temperature field. The magnitude and direction of this current jet varied with the cross-shelf temperature gradient and wind velocity. It tended to intensify during northeastward (downwelling favorable) winds, and to lessen, or even reverse, during southwestward to northwestward (upwelling favorable) or southeastward (downwelling favorable) winds. In a case with strong stratification and without external atmospheric forcings, a well-defined clockwise warm-core eddy formed near the northeastern coast of the Keweenaw Peninsula as a result of baroclinic instability. A warmcore eddy was detected recently from satellite surface temperature images, the shape and location of which were very similar to those of the model-predicted eddy. The energy budget analysis suggested that the eddy kinetic energy grew exponentially over a timescale of 7 days. Growth was due to a rapid energy transfer from available eddy potential energy. The subsequent decline of the eddy kinetic energy was the result of turbulent diffusion, transfer from the eddy kinetic energy to mean kinetic energy, and outward net energy flux.

A non-orthogonal coordinate primitive equation model has been developed for the study of the Keweenaw Current in Lake Superior. This model provides a more accurate fitting of the coastline A comparison with a curvilinear orthogonal model shows that the non-orthogonal transformation model provided a better simulation of the current jet in the near-shore region. Accurate fitting of both bathymetry and irregular coastlines plays an essential role in capturing the magnitude of the Keweenaw Current and cross-shelf structure of the thermal bar near the coast. The formation of the Keweenaw Current and thermal front was directly driven by a westerly or southwesterly wind and seasonal development of stratification over steep bottom topography. Under a condition with accurate fitting of steep bathymetry, failure to resolve the irregular geometry of the coastline can result in an underestimation of the magnitude of the Keweenaw Current by about 20cm/s.