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Tides in the Kauai Channel and their Interactions with Mesoscale Currents


C. Chavanne1, P. Flament1, M. Merrifield1, D. Luther1 and Klaus-Werner GURGEL2
1 Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI 96822, USA.
2 Institute of Oceanography, University of Hamburg, Bundesstrasse 53, D-20146 Hamburg, Germany.


The Kauai Channel between Oahu and Kauai, Hawaii, is a site of strong internal tides generation, and was chosen as the study site of the Hawaii Ocean Mixing Experiment (HOME). Ocean currents observations from HF-radars confirm the surfacing of M2 internal tidal beams 50 km south of the ridge, as predicted from numerical modelling. While the observed and modelled tidal currents amplitudes are of the same order during Fall 2002, the observed amplitudes are significantly reduced during Spring 2003. Mesoscale currents variability is weak during Fall 2002, with occasional anti-cyclonic eddies spun-up from the southwest corner of Oahu and drifting westward. It is much stronger during Spring 2003, with oscillations of northwestward/southeastward currents, with an amplitude of 50-60 cm/s, a period of 20-25 days, and a wavelength of ~150 km, propagating across the channel with a northeastward phase speed of ~8 cm/s. It is proposed that the stratification variations and strong current shears associated with these oscillations are responsible for the M2 internal tide energy modulation.

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