The nature of the oceanic response to pressure loading is explored usi
ng a constant-density, shallow-water numerical model driven by atmosph
eric pressure fields from the European Centre for Medium Range Weather
Forecasts. The model has realistic bottom topography and coastlines a
nd is run for 1 year (1986) on a global domain. Meridional gradients i
n mean sea-level are generally large (10-20 cm over 20-30-degrees), pa
rticularly in high southern latitudes. Sea-level variability is strong
in mid- and high latitudes (typical standard deviations of 10-15 cm),
but weakens towards the equator. Results indicate a significant contr
ibution of pressure-driven fluctuations to the observed large-scale se
a-level variability in mid- and high latitudes, away from western boun
dary regions. Pressure-induced velocity signals are, in contrast, gene
rally small compared with other types of variability. The validity of
the inverted barometer approximation is found to be strongly dependent
on frequency and geographical location. Globally, the approximation i
s not reliable for periods shorter than approximately 2 days, but fail
ure at longer periods occurs over extensive regions (e.g. the tropical
Atlantic and Pacific, and the Southern Ocean). Nonisostatic contribut
ions to the sea-level variability are substantial in many areas, inclu
ding the tropics, the high-latitude North Atlantic, the Gulf of Mexico
, and several other boundary regions. The dynamical signals are partly
associated with the excitation of several high-frequency normal modes
. Some of these features have a spatial structure and period very simi
lar to normal modes calculated by Platzman and collaborators. Their pr
esence in the model indicates that atmospheric pressure forcing is a p
ossible mechanism for normal mode excitation.