A model study of internal tides
in coastal frontal zone
Abstract
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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