Current meter, CTD and tide gauge data collected in a sill fjord in northern British Columbia are considered. Annual changes in stratification are such that the natural internal period of oscillation of the fjord matches that of the semidiurnal tide in both the spring and fall of the year. Evidence of a semidiurnal internal resonance is sought by calculating the ratio of energy and the relative phase of vertical current shear and the barotropic tide. It is possible to show a strong response in the fall coincides with a phase shift of 180° which is the signature of a resonance. Calculations prove the resonant mode to be the first harmonic in both the vertical and horizontal. Results based on springtime data also show a resonant response although it is less clear due to the effects of strong river runoff.
Keeley, J. R.. 1984. "Observations of an internal resonance in a fjord." Journal of Marine Research 42, (4). https://elischolar.library.yale.edu/journal_of_marine_research/1749