The southern Caribbean upwelling system: Sea surface temperature, wind forcing and chlorophyll concentration patterns

Sixteen years of sea surface temperature (SST, 1994-2009) were used to characterize the southern Caribbean upwelling system. This system extends from 61-75.5°W and 10-12.5°N, with 21 upwelling foci clustered in seven groups differentiated by their SST cycles. Two of those groups had the strongest coastal upwelling: the 'eastern area' (63-65°W) and the 'western area' (70-73°W). The literature reports that the eastern and western upwelling areas hold 78% and 18% of the small pelagic biomass within the upwelling system, respectively. We looked into variations of the upwelling dynamics in those areas using seasonal cycles of satellite SST, chlorophyll-a (Chl) and sea-wind, as well as climatological hydrographic data from the World Ocean Atlas. Comparing their annual averages, the eastern area featured the lowest SST (25.24 °C) and the highest Chl (1.65 mg m−3); it has moderate wind intensity (6.12 m s−1) and shallower 22 °C isotherm (85 m). The western area had stronger winds (8.23 m s−1) but deeper 22 °C isotherm (115 m), slightly higher SST (25.53 °C) and moderate Chl (1.15 mg m−3). The upwelling in the eastern area was more prolonged than in the western area (SST <26 °C during 8.5 and 6.9 months, respectively). According to the 'optimal environmental window' theory, small clupeoid recruitment is a dome-shaped function of the upwelling intensity, turbulence and SST, with an optimum wind speed around 5-6 m s−1. The eastern upwelling area wind speed is close to this optimum value. The western upwelling area shows much higher wind speed that causes high level of turbulence and strong offshore transport that could hinder small pelagics recruitment in that area.