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.
