On the cyclonic mean circulation of large lakes.
In large lakes, during the heating season, the combination of surface wind drift and solar heating results in the horizontal transport of some of the absorbed heat into the coastal zone. Large-scale vertical movements associated with alternating upwellings and downwellings distribute the heat over a deeper water mass than at mid-lake. As a result, the mean shape of isotherm surfaces is "domed" and, correspondingly, the lake surface is slightly raised near shore and depressed over the center thermocline dome. The mean circulation in geostrophic equilibrium with this surface elevation field is a cyclonic gyre. In Lake Ontario, the amplitude of the mean surface velocity associated with this gyre is of the order of 3 cm sec(-1).
Csanady
G T
GT
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543.