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.