American Society of Civil Engineers

Circulation and Drift Pathways in the Northwest Atlantic Ocean

by Jinyu Sheng, (Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 4J1. E-mail:
Section: Circulation, Mixing, and Transport, pp. 364-383, (doi:

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Document type: Conference Proceeding Paper
Part of: Estuarine and Coastal Modeling
Abstract: A three dimensional ocean circulation model is used to study the seasonal circulation and major pathways of passive tracers in the northwest Atlantic Ocean. The model is forced by monthly mean temperature and salinity, monthly mean COADS wind stress and heat flux, and flows through the model open boundaries. The model uses the flux-limiter advection scheme proposed by Thuburn and flux conserving advection scheme proposed by Dietrich to reduce the spurious overshoots and undershoots produced by the second-order centered scheme. To improve the performance of the northwest Atlantic Ocean model in simulating circulation and passive tracers, the semi-prognostic method suggested by Sheng et al. (2001) is used in this study. The novel aspect of this method is that the model currents are adjusted toward climatology, while the model temperature and salinity equations are fully prognostic. The adjustment is accomplished by replacing the conventional density term in the hydrostatic equation by a linear combination of model-computed and climatological density. For direct comparisons, the pure-diagnostic and pure-prognostic methods are also used in this study. In diagnostic calculations ocean currents and tracer equations are calculated with temperature and salinity specified at all model grid points at each time step. In prognostic calculations, by contrast, the temperature and salinity equations are integrated forward along with the momentum and tracer equations. The northwest Atlantic Ocean model is integrated for five years with two sets of passive tracers seeded in the Labrador Sea. Multi-year model results reveal that the semi-prognostic method performs significantly better than the pure-diagnostic and pure-prognostic methods in simulating circulation and major pathways of passive tracers in the study region.

ASCE Subject Headings:
Three-dimensional models
Water circulation