The PLUME Model: A 3D Numerical Model of the Southern Benguela

The PLUME Model: a 3D Numerical Model of the Southern Benguela

The PLUME model aims to simulate the dynamics of the environment
within the southern Benguela, with a particular emphasis on meso-scale
physical processes affecting small pelagic fish spawning and
recruitment.

In the Southern Benguela, spawning takes place on the Western Agulhas
Bank, along the edge of the Agulhas Current. Eggs and larvae are
transported/ migrate from the upwelling front, to the west coast by a
jet. Offshore advection and losses by currents, filaments and eddies
are important, as is retention in the nursery ground located withing
the West Coast upwelling.

To model the southern Benguela an efficient and robust numerical code,
that is able to resolve the mesoscale characteristic patterns that
develop over the coastal domain (eddies, jets, filaments), is needed.
The model domain had to include the main pelagic fish spawning and
nursery grounds, must be large enough to allow features such as
upwelling filaments and eddies to fully develop. ROMS - Regional Ocean
Modeling System developed by Rutgers University and University of
California, Los Angeles was used as a basis for the model.

Temperature and salinity fields were extracted from a seasonal
climatology derived from the results of the AGAPE (Biastoch & Kraub,
1999)basin scale ocean model (z-co-ordinate, 1/3 degree resolution).
Surface fluxes were derived from the COADs monthly climatology with
0.5 degree resolution (Da Silva et al, 1994).

The model reproduces the main oceanographic features of the Southern
Benguela, including the West Coast upwelling, the Cape Columbine
plume, the Agulhas Current, Agulhas rings, meso-scale eddies and
filaments are reproduced. The solution is stabilized after 2 years
and then the model reaches a cyclic quasi-stationary solution but with
significant inter-annual variability despite the climatological
forcing.

Information taken from presentation given by Dr. C. Roy at
ENVIFISH-VIBES meeting, October 2000