Recent Trends in SST, Chl‐a, Productivity and Wind Stress in Upwelling and Open Ocean Areas in the Upper Eastern North Atlantic Subtropical Gyre

The global upper ocean has been warming during the last decades accompanied with a chlorophyll‐a (Chl‐a) and productivity decrease. Whereas subtropical gyres show similar trends, Eastern Boundary Upwelling Systems are thought to increase in productivity due to increased trade winds. This study analyzes recent trends in sea surface temperature (SST), Chl‐a, net primary production (NPP) and meridional wind stress in the Eastern North Atlantic subtropical gyre (NASE) in order to examine if the global trends can be detected in open ocean and upwelling areas and how the ocean biota responds. Satellite data of such variables of the last 15–40 years were analyzed to calculate mean trends in upwelling areas in the Canary upwelling system and open ocean areas around the Azores, Madeira and the Canary Islands. Our results show significant warming in the area with a maximum of 2.7°C per century for the Azores. Moreover, a general decreasing trend for Chl‐a and NPP seems to be more evident in the permanent upwelling areas, which will be responsible for a loss of 0.13% of the global NPP per century. Our results also highlight a significant expansion of the oceanic desert area of 10% with an increase in unproductive days of up to 84 days in the last 20 years. The competitive relationship of stratification and wind stress in the Canary upwelling system might be a more plausible explanation for the decrease in Chl‐a and NPP in upwelling areas linked to the increase in upwelling favorable wind stress and the surface warming. Plain Language Summary The increase in global sea surface temperature (SST) is accompanied with a decrease in chlorophyll‐a (Chl‐a) and primary productivity. Microscopic algae called phytoplankton and their pigment Chl‐a are responsible both for the production of organic material made available for larger animals as food source and the production of oxygen. Different oceanic areas such as the open ocean or coastal so‐called upwelling areas in the Eastern North Atlantic Subtropical show characteristic production regimes linked to ocean temperature or wind stress. The main goal of this study was to analyze trends based on satellite data of SST, Chl‐a, productivity and wind stress in different oceanic areas in order to identify the biological response to the physical forcing. Our study shows that the highly productive upwelling area along Northwest Africa and Western Iberia is warming at a slower pace than open ocean areas around Madeira, the Canary Islan