The effects of a prescribed salinity field on a 10-level primitive equation ocean circulation model

Abstract

A prescribed salinity field is inserted into a 10-level primitive equation ocean circulation model. The model has been developed and is being improved in order to study large-scale thermal anomalies observed in the Central North Pacific Ocean by the North Pacific Experiment (NOR-PAX) The salinity field, based on observations along 160 W longitude, is independent of longitude and time, and is smoothed in the north-south direction to remove small scale variations. A new equation of state which is a function of temperature, salinity and depth is used to determine density in the calculation of pressure from the hydrostatic equation. The parameterization of vertical mixing is changed to account for the stabilizing effect of salinity and the supercooling of the surface layers at high latitudes during winter. The addition of salinity induced changes in the currents at high latitudes when compared to the model without salinity. A Rossby wave was excited in the middle latitudes which produced transient changes. The convective adjustment process enabled significantly colder water to overlie warmer water in the regions where salinity increases with depth. Supercooled surface temperatures, encountered during winter at high latitudes, are handled through convective mixing, but further investigation into the dynamics of sub-grid scale vertical convection at near freezing temperatures is recommended.