Upwelling is an oceanographic phenomenon consisting of vertical movements of bodies of water from oceanic depths towards the surface. Strong winds that cross marine surfaces push warm superficial waters, moving them away from the coast. These warm waters are then substituted by cold and nutrient rich waters from the depth.
In the Costa Rican Thermal Dome, the upwelling system is caused by the circulation of the Northeastern Equatorial Counter Current, the Costa Rican current and the Northwestern Equatorial Current in combination with strong Trade Winds (the Papagayo Jet Stream) that cross over the Lake of Nicaragua and the northern plains of Costa Rica.
Figure 2. Oceanographic dynamics of an upwelling system
The effects of upwelling
In oceanic areas where waters rich in nutrients like nitrate and phosphate reach levels where sunlight can penetrate, the phytoplankton concentration increases exponentially, thus generating a great concentration of fish, marine mammals and other organisms.