Miller, A. J., P. F. G. Lermusiaux and P.-M. Poulain, 1996:
A topographic-Rossby mode resonance
over the Iceland-Faeroe Ridge.
Journal of Physical Oceanography, 26,
2735-2747.
Abstract.
An array of current-meter moorings along 12W on the southern side
of the Iceland-Faeroe Ridge reveals a narrowband
barotropic oscillation with period 1.8 days in spectra of velocity.
The signal is coherent over at least 55km scales and propagates phase with
shallow water on the right (towards the northwest).
Velocity ellipses tend to be elongated (crossing contours of f/H)
and rotate anticyclonically.
Solutions of the rigid-lid barotropic shallow-water equations
predict the occurrence of a topographic-Rossby normal mode
on the south side of the ridge
with spatial scales exceeding 250km and
with intrinsic period near 1.84 days.
This fundamental mode of the south side of the ridge
has predicted spatial structure,
phase propagation and velocity ellipses that are consistent
with the observed oscillation.
The frictional amplitude efolding decay time for this normal mode is
estimated from the observations to be 13 days.
The observed ocean currents
are significantly coherent with zonal wind stress fluctuations
(but not with wind-stress curl)
in the relevant period band which indicates the oscillation is
wind-forced.
This appears to be the first clear evidence of a
stochastically forced
resonant barotropic topographic-Rossby normal mode in the ocean.
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