Marine Ecosystem Dynamics Modeling Laboratory

Water Exchange Process

The particle tracking experiments were conducted to examine the physical process controlling the water exchange between MHB and NB. Three cases are described here: 1) only tidal forcing, 2) tidal forcing plus river discharges, and 3) tidal forcing and river discharge plus variable winds.
The water exchange between MHB and NB is mainly controlled by variable winds. This can be clearly seen in particle tracking experiment results under different physical environments shown in Fig. 1. In the case with the only tidal forcing, particles, which are released in the TR, oscillate over the length scale of a tidal excursion around the mouth of the river, with increasing downriver and upward movements each cycle. After 30 days, particles are still in the surrounding area of the river. When the river discharge is added, particles move southward with an oscillating track. After 30 days, particles arrive in the southern part of MHB. This result is consistent with the subtidal circulation pattern shown in buoyancy-driven flow due to river discharges. Adding wind forcing increases the spatial variability of particle trajectories. Two particles released at proximal locations followed significantly different trajectories after 10 days. One particle moves westward and entered the northern coastal region and the other moved rapidly southward and entered NB after 10 days. This variability is even more obvious n the case when large numbers of particles are released: supporting our argument that the wind is a dominant forcing that controls the variability of the water exchange between NB and MHB.

To see the movements of the large number of particles in three cases described here, please click the picture below.

Posted on January 16, 2014