The near-surface pressure field over Georges Bank: 1995-1998
K. H. Brink, R. Limeburner and R. C. Beardsley
Throughout the 1995-1999 GLOBEC/Georges Bank program, surface
drifter measurements were made at a nominal drogue depth of 10m.
These data used to compute total accelerations and the Coreolis
force following the drifter. In addition, surface winds were used (along
with an estimate of mixed layer depth) to estimate a surface shear stress
gradient. The net result is an estimate of the 10m pressure field over
the Bank. These estimates are then used as input for an objective
analysis yielding the pressure itself (adjusted to an absolute sea surface
height with the Boston sea level).
The momentum balance is geostrophic at lowest order, so the
pressure field is largely as might be expected from drifter tracks: summer
mean pressure contours close around the top of the Bank (consistent with
recirculation), but winter mean pressure contours do not. In addition,
there is a cross-bank pressure gradient near the shelf break all around
the Bank except at the western side, where Georges Bank adjoins the Middle
Atlantic Bight shelf. A movie is shown to illustrate the daily evolution
of the detided pressure field and how it responds to the surface wind
stress.