Currents and Sediment Movement on Georges Bank

The area on the southern flank of Georges Bank, part of which has recently been leased for petroleum exploration (Lease Sale 42), can be conceptually divided into three regions characterized by water depth, strength of the semidiurnal tidal currents, hydrography, and sediment movement. In water depths shallower than approximately 60 m the semidiurnal tidal currents are strong (surface currents greater than 50 cm/s), the mean circulation is clockwise at speeds generally less than 5 cm/s, and the water column is vertically well mixed throughout the year. The sea floor is shaped into a series of sand waves and ridges; the surface sediments are fine to coarse sands and are constantly reworked by the tidal currents.