Do tides and seiches occur on lakes?

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Do tides and seiches occur on lakes?
graph of dramatic Lake Erie seiche in 2003


Tides are changes in water level caused by the gravitational pull on water by the moon and, to a lesser extent, the sun. Tides are of interest mainly in oceans and their coastal estuaries, which are part of one big body of water that is free to move about the earth.
Tides in the Great Lakes are caused by the same gravitational forces; however, the highest tide in the Great Lakes is less than two inches.

These tidal changes are minor in comparison to changes in lake levels caused by the wind and pressure changes. In fact, such variations are so much larger than the tidal forces that the Great Lakes, and smaller lakes, are considered to be non-tidal.

Changes in lake water levels are due primarily to meteorological effects. One example of a weather-driven change in the lake level occurs when strong steady winds blow over the water for at least several hours. The wind pushes the water onto the shoreline it is blowing towards, causing the water to pile up. Once the winds weaken, or change direction, the driving force of the wind relaxes and the water flows back away from the shoreline. This wave of water is called a seiche. The water levels can sway back and forth much like water sloshing in a bathtub, causing lake levels along the shorelines to oscillate from high to low levels until it reaches its equilibrium level.

Steven A. Ackerman and Jonathan Martin are professors in the Department of Atmospheric and Oceanic Sciences at UW-Madison, are guests on the Larry Meiller‘s WHA-AM radio show the last Monday of each month at 11:45 a.m.