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.

中文翻译：

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北大西洋上东部亚热带环流上升流和开阔海域的 SST、Chl-a、生产力和风应力的最新趋势

在过去的几十年中，全球上层海洋一直在变暖，伴随着叶绿素a ( Chl- a ) 和生产力的下降。虽然亚热带环流显示出类似的趋势，但东部边界上升流系统被认为由于信风增加而提高了生产力。这项研究分析了海洋表面温度的近期趋势（SST），Chl-一、北大西洋东部副热带环流 (NASE) 的净初级生产 (NPP) 和经向风应力，以检查是否可以在公海和上升流区域检测到全球趋势以及海洋生物群如何响应。对过去 15-40 年这些变量的卫星数据进行了分析，以计算加那利上升流系统和亚速尔群岛、马德拉群岛和加那利群岛周围开阔海域的上升流区域的平均趋势。我们的结果显示，亚速尔群岛每世纪最高升温 2.7°C。此外，Chl- a的总体下降趋势NPP 似乎在永久性上升流区更为明显，这将导致每世纪全球 NPP 损失 0.13%。我们的结果还强调了海洋沙漠面积显着扩大了 10%，过去 20 年中非生产天数增加了 84 天。在加那利上升流系统分层与风应力的竞争关系可能是在Chl-减少一个更合理的解释一上涌链接到上涌顺风应力和表面变暖的增长领域和NPP。