Two passive tracers have been released in the system. One of them has a constant source at the river's mouth and will be usefull in order to study the fate of the river plume and its transfer to the Mediterranean. The other has been released in unitary concentration in the northern part of the Gulf of Cadiz so that we can estimate the part of those waters that flows through the Straits of Gibraltar. Both tracers have null production-destruction terms, so that they are completely independant of their chemical environment. Both also have null migration velocities. They are affected only by the advection and diffusion processes and follow the water masses in which they are included.
Figure 5.17 shows the dispersion of tracer 1, launched at the river mouth. We can see that it is advected towards the Straits, following the Spanish coast. After 21 days, only negligible fractions (under )of the initial unitary concentration have reached the entrance of the Straits and it would be necessary to resume the simulation in order to get long term results.
Figure 5.17: Tracer 1 dispersion in the nested model
Tracer 2, whose quantity in the system is far more important at the start of the simulation, is mainly advected eastwards in the surface layers as shown at figure 5.19. After only 21 days, non-negligible concentrations (more than ) can be found in the Mediterranean Sea, following Atlantic waters around the Western Alboran Gyre.
In the deep layers, this tracer is advected westwards, following Mediterranean water in its density current along the continental slope. The fate of tracer 2 is illustrated at figures 5.18 to 5.20.
Figure 5.18: Tracer 2 shallow dispersion in the coarse model
Figure 5.19: Tracer 2 shallow dispersion in the nested model
Figure 5.20: Tracer 2 deep dispersion in the nested model