A model study of internal tides in coastal frontal zone


Internal tides near a midlatitude shelf-slope front are studied using an idealized numerical model, with emphases on their structure, energetics and mixing effects. It is found that the properties of internal tides are highly dependent on frontal configuration and tidal frequency. At a winter front, energetic internal tides are generated and arrested in the frontal zone; the cross-shelf flow tends to be surface (bottom) intensified by a large internal circulation cell at the diurnal (semidiurnal) frequency. At a summer front, diurnal internal tide is still trapped, but semidiurnal internal tide propagates out of the frontal zone in the offshore direction while arrested at the inshore boundary. The presence of the shelf-slope front enhances the generation of internal tides, and it also causes an amplification of the semidiurnal internal tide by trapping its energy in the frontal zone. This amplification is most prominent at the offshore boundary of the winter front and the inshore boundary of the summer front, where strong tidal refraction takes place. Internal tides can cause significant mixing and dispersion in the frontal zone, with the semidiurnal internal tide being most effective toward the frontal boundaries, and the diurnal internal tide more effective near the site of generation.

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