Controls and variability of Yucatan Shelf coastal upwelling

The coastal ecosystems influenced by upwelling are some of the most important ecologically and socio-economically in the world. The upwelling within these regions fertilises the coastal zone and generates phytoplankton blooms which support the marine trophic chain. The Region of Cabo Catoche, off the Yucatan Penininsula in the boundary of the Gulf of Mexico and the Caribbean Sea exhibits seasonal upwelling in both spring and summer (Merino, 1992, 1997; Mateos-Jasso, 2009; Reyes-Mendoza et al, 2015).

In contrast with the major global upwelling regions located at the ocean margin (due to wind-forced Ekman dynamics) this is not the primary mechanism that generates upwelling in the coasts of Yucatan (Reyes-Mendoza et al., 2015). The principal mechanism in this region is the interaction between the currents and the topography although the detailed processes themselves are not yet well understood. One candidate mechanism is pumping due to bottom Ekman dynamics, similar but opposite to the Ekman draining in NW European Shelf Edge (Souza et al. 2001,); the flow near the bottom rotates to the left of the main current which due to the orientation of the coast drives water up the shelf slope (Merino 1992). Numerical simulations have suggested that it may be driven from interactions of the variable bathymetry and the variability of the Yucatan Current. Other candidates are geostrophic adjustment between the core of the Yucatan Current and Cabo Catoche lifting the pycnocline in the coast of Cabo Catoche (Furnas and Smayd, 1987), or frictional interaction between the Yucatan Current and the Cuba counter-current (Garcia, 1990). At present there is no clear understanding of which is the dominant process nor quantification of how each mechanism contributes to coastal upwelling. This research will provide that knowledge.