Kessler and Gourdeau, 2006b Abstract
The annual cycle of circulation of the southwest subtropical Pacific, analyzed in an ocean GCM
Kessler, W.S. and L. Gourdeau, 2007
Journal of Physical Oceanography, 37(6), 1610-1627
Abstract
An ocean GCM, interpreted in light of linear models and sparse observations, is used to diagnose
the dynamics of the annual cycle of circulation in the western boundary current system of the
southwest Pacific. The simple structure of annual wind stress curl over the South Pacific
produces a large region of uniformly-phased, stationary thermocline depth anomalies such that
the western subtropical gyre spins up and down during the year, directing flow anomalies
alternately towards and away from the boundary at its northern end, near 10°S. The response of
the western boundary currents is to redistribute these anomalies northward towards the equator
and southwards to the subtropical gyre; a redistribution that is determined principally by offshore
thermocline depth anomalies due to linear Rossby processes, not to boundary dynamics. When
the subtropical gyre and South Equatorial Current (SEC) are strong (in the second half of the
year), the result is both increased equatorward transport of the New Guinea Coastal Current, and
poleward transport anomalies along the entire Australian coast. Because of this opposite phasing
of boundary current anomalies across 10°S, annual migration of the bifurcation point of the total
SEC, near 18°S in the mean, has no significance regarding variability of transport from
subtropics to equator.
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