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Overview of physical processes in large lakes: Internal waves : Kelvin Waves

The Kelvin wave is a long gravity wave formed in response to a large wind event [1, 5, 6]. This type of wave is formed when the Earth's Coriolis force from offshore is balanced against a topographic boundary such as a coastline, or a waveguide such as the equator [1]. An important feature of the Kelvin wave is that it is non-dispersive (i.e. the phase speed of the wave crests is equal to the group speed of the wave energy for all frequencies). In other words, a Kevin wave retains its shape as it moves in the alongshore direction over time. The Coriolis force causes the lake’s surface layer to move to the right of the wind (in the northern hemisphere) and initiates a wave induced thermocline propagating around the lake in the form of a Kelvin wave.

Kelvin waves propagate along the shore of the lake [7], bounded only on one side by the shoreline and defined by the Rossby Radius of deformation and because the gravity they exponentially decay with distance from the shore [1,9]. Consequently, the largest amplitudes are found at the shore [5]. The progression of the wave along a lake shore induces currents parallel to the direction of the wave propagation [9].

Experiments in Lake Ontario have shown that a Kelvin wave traveling a full cycle, along the lake has a period of the order of 14 days. Therefore, the progress of the Kelvin wave is often interrupted by a new storm or wind event and capturing and studying these waves is rather difficult.