The mean summer and fall circulation of Western Bank on the Scotian Shelf

The mean climatological circulation on the central Scotian Shelf was invest igated during the summer (August-September) and late fall (November-Decembe r) by applying a diagnostic model coupled with a variational approach. Hist orical Conductivity-Temperature-Depth (CTD) profiles, current meter observa tions and atmospheric climatological data were applied to the model. The re constructed fields of temperature, salinity and velocity are dynamically ba lanced and provide estimates of the circulation features on Western Bank fo r the summer and fall. The availability of new direct current measurements on and around Western Bank enabled us to define the barotropic velocity fie ld and to produce realistic circulation patterns. The primary difference between the summer and fall circulation is the inten sification of the surface flow field in the fall. The transport of the Nova Scotia current increases from 0.4 Sv in summer to 0.9 Sv in the fall. At t he same time, some qualitative differences were found over Western Bank and in Emerald Basin. Applying the variational assimilation procedure at high resolution (6 km) produced narrow currents (roughly 20-40 km across) in agr eement with the structure of the local topography and current meter observa tions.