Recent changes and trends of the upwelling intensity in the Canary Current Large Marine Ecosystem

Abstract

We provide a summary of current knowledge for the recent trends of the coastal upwelling intensity in the region from 8°N to 43°N, computed from both wind and sea surface temperature (SST) remotely sensed, from 1982 to 2011. In particular, the impact of changes possibly linked to global warming is estimated in the form of spatial linear trends. Statistical analysis of trends and seasonal changes of the upwelling activity are carried out in order to verify the hypothesis of Bakun (1990), which anticipates an intensification of the upwelling favorable winds and therefore a cooling of coastal waters. Our study brings new insights on the spatial patterns of the changes. The results indicate distinct and questionable trends of the two categories of upwelling indices, in a region associated with a strong SST warming, especially in the southern part of the system. While the central and southern parts of the system display an increase of upwelling-favorable winds, no significant upwelling trend is found in the same sub-regions from SST-based upwelling indices. It is stated that changes in the internal structure of the upper ocean, as a result of global warming, may be responsible of such differences: a significant warming of the surface upwelled waters possibly combined with a thickening of the surface mixed layer.