Water Quality

Case Study

Influence of Density Changes on Portland Bight Circulation

Freshwater discharge along the southeast coast of Jamaica can be sourced from riverine outflow, underground seeps or run-off flow. Generally, the volume of the fresh water discharges causes changes of the current flow structure due to the water density difference. This results in a density current. The density current, due to density differences can exist between two fluids because of a difference in temperature, salinity or concentration of suspended sediment. This drives current flow along the coast by the effect of the Coriolis force deflecting the down-slope movement of the current to the right in the northern hemisphere (to the left in the southern hemisphere). Here is an example of the effect of the density current, where the particle tracks developed in the section of Hydrodynamics Model based on the result of the current flow, salinity and temperature distributions. The particles are carried toward the south along the coast from the density differences set up by the Salt River freshwater outflow. These models are useful for predicting the transport of contaminants such as effluent discharge, oil spills and invasives that may affect shoreline industries and communities.