Analyzing the effects of wind and stratification on surface currents in a large lake

Surface currents in large lakes are important for water quality and ecosystem processes since they drive nutrient transport. In this study, the individual effects of wind and stratification on surface currents are analyzed in a large lake, Lake Ontario. A state-of-the-art numerical model is applied to explore effects of a common wind scenario (6 m/s eastward) and stratification on surface currents, and their interactions with tributary plumes. For a non-stratified lake, eastward wind accelerates the surface velocities by maximum 23.5 cm/s in nearshore areas, while its effects on current direction are not obvious in the nearshore areas. In mid-lake regions, wind could change the current directions by about 100 degrees counter-clockwise. This eastward wind accelerates the propagation of the Niagara River plume, but decreases its width and bulge area at the river mouth. Lake stratification increases surface velocities in offshore regions and decreases velocities in nearshore regions. The changes of surface current direction by stratification are within 68 degrees in most areas. Tributary plumes are strongly affected by surface currents and the unusual westward Niagara River plume observations could be explained by currents caused by unusual westward wind conditions. Predicting changes in surface currents caused by wind and stratification is important for understanding nutrient dynamics and shedding light on ecological problems such as algal bloom occurrences.