Physical and biological modeling in the Gulf Stream region:: I. Data assimilation methodology

Physical and biological data are assimilated into a time-evolving, mesoscale-resolution three-dimensional (3-D) ocean model using optimal interpolation. Simulations are conducted in the Gulf Stream region during the BIOSYNOP/Anatomy of a Meander Experiment in September–October of 1988. Physical data assimilation only or biological data assimilation only resulted in misalignment of the physical and biological fronts, causing spurious cross-frontal fluxes of biological quantities. Assimilation of both physical and compatible biological fields was necessary for adequate equilibration of the simulated fields. The resulting combined 4-D fields substantially extend the value of the observations alone. A technique is presented for deriving the necessary, dynamically consistent 3-D physical and biological field estimates from data for initialization and assimilation into time-evolving model simulations.