SEMINAR

Offshore Spreading of a Buoyant Coastal Discharge

Center of Higher Learning
Stennis Space Center

ABSTRACT

Freshwater discharge from rivers and estuaries produces plumes and coastal currents locally. What is the fate of these coastal currents far downstream and over long time scales? The mechanism and processes related to the slow alongshelf evolution of a surface-advected plume in the presence of an ambient flowfield are studied with the help of a three-dimensional primitive equation numerical model.

As the buoyant water enters the coastal ocean, it turns anticyclonically and moves downstream in the direction of Kelvin wave propagation. Close to the source, the plume is surface-advected (Yankovsky and Chapman, 1997). The offshore buoyancy flux in the bottom boundary layer pushes the front seaward detaching it from the coast and moving it offshore. Eventually, the cross-shelf buoyancy flux vanishes shoreward of the front and the front reaches an equilibrium depth at a particular alongshelf location. At this point, the quasi-stationary buoyancy balance is between horizontal and vertical diffusion and cross-shelf buoyancy flux. The density front has switched from a surface-advected plume to an intermediate or bottom-advected type at this location. Horizontal diffusion contributes to effective horizontal mixing and helps spread freshwater offshore.

WHEN(day): Friday, November 10th, 2000

WHEN(time): 2:00pm

EVERYBODY IS INVITED