This animation shows a standing wave (black) depicted as a sum of two propagating waves traveling in opposite directions (blue and red). (Animation: National Ocean Service/NOAA)

Seiche

[say’sh]

Definition:
An oscillating standing wave in a body of water that’s enclosed or partially enclosed, such as a lake, reservoir, swimming pool, bay, harbour or sea.

Origin:
Swiss French
Meaning to sway back and forth
The term was first used by Swiss hydrologist François-Alphonse Forel in 1890

Example:
The simplest example, albeit on a very small scale, of a seiche is the sloshing back and forth of water in a bathtub. On a much larger scale, this same effect can be created on big bodies of water by strong wind and rapid atmospheric pressure change that essentially pushes the water from one side of the body to the other. Lake Erie is particularly well known for seiches. In 2008, a particularly noteworthy seiche on Erie created 3.66- to 4.27-metre high waves along the lake’s south shore.