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 affect changes of the current flow structure due to the water density difference, and that causes density current. The density current which has the density difference can exist between two fluids because of a difference in temperature, salinity or concentration of suspended sediment is driven current flow along the coast by the effect of the Coriolis force deflected the downslope 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, shown as a particle track developed from the Hydrodynamics Model based on the results of the current flow, as well as salinity and temperature distributions. Particles are carried toward the south along the coast from Salt River due to density-driven currents. This gives useful information on where buoyant matter is likely to end up, such as debris and contaminants. The river also introduces changes in the water quality and this eventually makes its way near to populated regions, as shown in the bottom animation in this section.


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