Modeling summer circulation and thermal structure of Lake Erie

A three-dimensional primitive equation numerical model was applied to Lake Erie on a 2 km grid to study its summer circulation and thermal structure. Model results were compared to long-term observations of currents and temperature made in 2005 at several locations, mostly in its central basin. In the shallow and mostly unstratified western basin circulation is driven by Detroit River inflow (modified to some extent by wind) and is from west to east. In the central basin (which is of intermediate depth and has a relatively flat bottom), the modeled circulation is anticyclonic (clockwise), driven by anticyclonic vorticity in the surface wind, and the thermocline is bowl-shaped, in line with observations. In the deep part of the eastern basin, the thermocline is dome-shaped and circulation is cyclonic (counter-clockwise), due to density gradients (a configuration typical for other large deep lakes), while shallower areas are occupied by anticyclonic circulation driven by anticyclonic wind vorticity. In the central basin, modeled temperature and circulation patterns are quite sensitive to the specification of the wind field. Anticyclonic wind vorticity leads to thinning of the hypolimnion in the central basin and earlier destratification in the fall.