Great South Bay Project

The Great South Bay Project

Modeled Wind Forced Responses

To model the effects of wind forcing on Great South Bay we first note that there are two aspects of the problem that can be somewhat separated. The first is the effect of local wind forcing independent of what is happening over the continental shelf. In this regard, the along Bay wind component is the most important. The second aspect is how the Bay responds to the coastal set-up or set-down over the shelf. This latter aspect is similar in many respects to tidal forcing although it is often associated with longer time scales resulting in less attenuation. To address the wind-forced issue we have divided up problem into the local problem addressing only the locally forced response using spatially uniform winds. Later we will combine coastal ocean elevation response to large scale events with the local forcing. For the moment we will look at the along-Bay wind forced responses under constant winds and then examine the response to an actual Nor-easter which includes time varying wind stress amplitude and direction.

Constant Along-Bay Winds

To examine the response to along-Bay winds, the model was hot-started from the end of the initial runs of 200,000 internal step (~155 hrs) and run for another 50,000 steps (~39 hrs) under constant stresses from 7.5 m/sec (~15 kts) winds toward either 255^o T or 75^oT. While this wind speed is well below storm magnitudes, it is typical of summertime sea breezes and moderate low pressure systems that affect the area. The plots shown below are M₂ tidal means computed from the last 12.4 hrs of the runs. The sealevel and currents qucikly settle into an equilibrium condition but the salinities are clearly undergoing change as the flushing of the Bay continues, characterized by inflow through the upwind inlet(s) and outflow through the downwind inlet(s).

Westward Wind Forcing:
Current Conditions under 7.5 m/s Westward (255^o T) Winds

Tidal-Mean Currents

Tidal-Mean Streamlines

Tidal-Mean Elevation

Tidal-Mean Salinity

Old Inlet Breach Scenario under 7.5 m/s Westward (255^o T) Winds

Tidal-Mean Currents

Tidal-Mean Streamlines

Tidal-Mean Elevation

Tidal-Mean Salinity

Atlantique Breach Scenario under 7.5 m/s Westward (255^o T) Winds

Tidal-Mean Currents

Tidal-Mean Streamlines

Tidal-Mean Elevation

Tidal-Mean Salinity

Eastward Wind Forcing:
Current Conditions under 7.5 m/s Eastward (75^o T) Winds

Tidal-Mean Currents

Tidal-Mean Streamlines

Tidal-Mean Elevation

Tidal-Mean Salinity