DISSIPATION IN INTERNAL TIDES AND SOLITARY WAVES

Solitons have been observed and studied on the Scotian Shelf using the vertical microstructure profiler EPSONDE. During one tidal cycle a pa cket of solitary waves has been sampled four times as it propagated on to the shelf to examine its evolution and decay. Enhanced turbulence a nd mixing were observed to occur in the strongest shear region of the wave packet as expected. About 20% of the energy lost as the solitary wave packet decayed can be attributed to turbulent dissipation. The ef fects of nonlinearity, dissipation, and dispersion are explored in ter ms of the Korteweg-de Vries-Burgers (KdVB) equation. The dispersive ti mescale is always much shorter than the dissipative timescale, and bot h decrease as the soliton moves onshelf. The mean dissipation timescal e, of 12 h compared to the dispersion timescale of less than 1 h, sugg ests that the waves are consistent with the KdVB description. Calculat ed vertical diffusivities are in the range of 10(-5)-10(-4) m(2) s(-1) .