egbert@coas.oregonstate.edu
A large
fraction of the variance in many oceanographic variables
is due to tides. As a
result, for many practical applications in the marine
environment (e.g., shipping, modeling of pollution
dispersal) accurate maps of tidal currents or elevations
are often indispensable. Knowledge of tides is of value
in many scientific studies as well. Here the tides are
often seen as a nuisance that must be removed from the
data prior to studies of longer period oceanographic
variations. For a fixed observation site, such as a
semi-permanent mooring, tides can be removed by
filtering of time series. With
data taken from moving platforms (e.g., ships,
Lagrangian drifters, satellites) spatial and temporal
variations are aliased, rendering a simple filtering
scheme untenable, and again requiring accurate maps of
tidal fields. Tides are of course not just a source of
noise. For example, studies of ocean microstructure have
shown a correlation of turbulent dissipation rates with
tidal cycles and there is increasing evidence that tides
may provide a significant source of energy for mixing
the deep ocean. For
studies
of
this
sort
a detailed knowledge of the tidal fields is again
desirable.
