Variability and extension of the Southern Caribbean Upwelling System: characteristics and structures

Abstract:

The Southern Caribbean Upwelling System (SCUS, 75-62ºW and 10.5-16ºN) is a tropical coastal upwelling whose contribution to the surface water masses, ecology and economy of the Caribbean is not completely known. Analyzes based on upwelling indices calculated from the wind (UIw), have shown the SCUS variability associated with regional changes in wind intensity, the coastline orientation and zonal differences in the thermal stratification of the water column. Due to the low latitude and high stratification in the SCUS, UIw do not allow a correct estimation of the volume of upwelled water in the system and its offshore advection to other areas of the Caribbean. This work analyzes the variability and extent of the SCUS, using satellite and modeled information of winds, sea surface temperature and chlorophyll. The SCUS variability is studied using upwelling indices that integrate wind and temperature data (UIwt), while its extension is estimated from the position of upwelling fronts. The results shown that the UIw overestimates the upwelling intensity mainly in the western sector (75-70ºW) of the SCUS. The seasonal and intra-seasonal variability of the SCUS observed through UIwt is not always coupled to atmospheric forcing, which suggests an upwelling modulation by internal waves of the Caribbean Sea. The interannual variability show frequencies associated with ENSO fluctuations that alter the intensity and the extension of the system in the long term. The extent of the SCUS (determined by the position of the temperature front) was greater in the western (280.7 ± 161.2 km) than in the eastern region (259.3 ± 134.8 km) of the system, reaching many offshore ecosystems of the insular Caribbean. However, the extension of the high biological productivity area (determined by the position of the chlorophyll front) was ~60% less than that of the upwelled waters (temperature front) in both regions, therefore, the contribution of upwelling nutrients for ocean ecosystems could be less than for coastal ecosystems. Despite this, the extension and intensity of upwelling in the SCUS may be the main mechanism to maintain biological productivity in the Caribbean.