CONVECTIVE BUILDING OF A PYCNOCLINE - A 2-DIMENSIONAL NONHYDROSTATIC NUMERICAL-MODEL

The convective building of a pycnocline is examined using a two-dimens ional nonhydrostatic numerical model forced by a balanced salinity dip ole (source and sink). Although the forcing fields re steady, the mode l develops oscillations that renew the model's analog of ''deep waters '' only intermittently. The oscillation cycle consists of a freshwater layer that advects along the surface, capping off the water column un der the sense source and preventing sinking; after a time, continuing densification forms a plume that breaks through the salinity barrier a nd convects beneath the dense source, ventilating the deep water. Incr easing the viscosity reduces but does not eliminate this cycle. When t he hydrostatic assumption is added, the model evolves systematically d ifferent salinity distributions than the nonhydrostatic assumption is added, the model evolves systematically different salinity distributio ns than the nonhydrostatic model due to the isolation of aprt of the t ank by a persistent convective column. The deep flow is also different in this case because of differences between the entrainment/detrainme nt profile of a hydrostatic plume and one modeled explicity. The model evolves a characteristically skewed distribution of densities that is similar to the distribution of temperature in the World Ocean. Rotati on increases the range of this distribution due to the inhibition of m eridional flow.