THE ADJOINT METHOD OF DATA ASSIMILATION USED OPERATIONALLY FOR SHELF CIRCULATION

A real-time shelf circulation model with data assimilation has been su ccessfully used, possibly for the first time, on the outer Nova Scotia n Shelf, The adjoint method was used to infer the time histories of fl ows across the four open boundaries of a 60 km x 60 km shallow-water e quation model of Western Bank, The aim was to hindcast and nowcast cur rents over the bank so that a patch of water (initially 15 km in diame ter) could be resampled over a 3-week period as part of a study of the early life history of Atlantic cod, Observations available in near re al time for assimilation were from 14 drifting buoys, 2 telemetering m oored current meters, the ship's acoustic Doppler current profiler and the local wind, For the postcruise hindcasts presented here, data fro m two bottom pressure gauges and two more current meters are also avai lable, The experiment was successful, and the patch was sampled over a 19-day period that included two intense storms, In this paper we (1) document the model and how the data are assimilated, (2) present and d iscuss the observations, (3) demonstrate that the interpolative skill of the model exceeds that of simpler schemes that use just the current velocity data, and (4) provide examples of how particle tracking with the model enables asynoptically acquired data to be displayed as syno ptic maps, greatly facilitating both underway cruise planning and post cruise data analysis, An interesting feature of the circulation on the bank was a nearly stationary eddy atop the bank crest, Larvae within the eddy were retained on the bank in a favorable environment until th e onset of the storms, The variable integrity of the eddy may contribu te to fluctuations of year-class success.