Under the impact of natural and anthropogenic climate variability, upwelling systems are known to change their properties leading to associated regime shifts in marine ecosystems. These often impact commercial fisheries and societies dependent on them. In a region where in situ hydrographic and biological marine data are scarce, this study uses a combination of remote sensing and ocean modelling to show how a stable seasonal upwelling off the Kenyan coast shifted into the territorial waters of neighboring Tanzania under the influence of the unique 1997/98 El Niño and positive Indian Ocean Dipole event. The formation of an anticyclonic gyre adjacent to the Kenyan/Tanzanian coast led to a reorganization of the surface currents and caused the southward migration of the Somali–Zanzibar confluence zone and is attributed to anomalous wind stress curl over the central Indian Ocean. This caused the lowest observed chlorophyll-a over the North Kenya banks (Kenya), while it reached its historical maximum off Dar Es Salaam (Tanzanian waters). We demonstrate that this situation is specific to the 1997/98 El Niño when compared with other the super El-Niño events of 1972,73, 1982–83 and 2015–16. Despite the lack of available fishery data in the region, the local ecosystem changes that the shift of this upwelling may have caused are discussed based on the literature. The likely negative impacts on local fish stocks in Kenya, affecting fishers’ livelihoods and food security, and the temporary increase in pelagic fishery species’ productivity in Tanzania are highlighted. Finally, we discuss how satellite observations may assist fisheries management bodies to anticipate low productivity periods, and mitigate their potentially negative economic impacts.

中文翻译：

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使用遥感数据检测到的1997/98年超级厄尔尼诺现象在东非沿海水域的主要生态系统变化

在自然和人为气候变化的影响下，已知上升流系统会改变其特性，从而导致海洋生态系统发生相关的政权转移。这些常常影响依赖它们的商业渔业和社会。在原位水文和生物海洋区域 由于缺乏数据，这项研究结合了遥感和海洋模型，显示了在独特的1997/98年厄尔尼诺现象和正印度洋偶极子的影响下，肯尼亚沿海稳定的季节性上升流如何转移到邻国坦桑尼亚的领海中事件。与肯尼亚/坦桑尼亚海岸相邻的反气旋环流的形成导致地表水流的重组，并导致索马里-桑给巴尔汇合区向南迁移，这归因于印度洋中部的异常风应力卷曲。这导致在北肯尼亚河岸（肯尼亚）观测到的最低叶绿素-a，而在达累斯萨拉姆（坦桑尼亚的水域）达到历史最高水平。我们证明，与1972、73、1982-83和2015-16的其他超级厄尔尼诺现象相比，这种情况特定于1997/98厄尔尼诺现象。尽管该地区缺乏可用的渔业数据，但根据文献讨论了这种上升趋势可能引起的当地生态系统变化。强调了对肯尼亚当地鱼类种群可能产生的负面影响，影响了渔民的生计和粮食安全，以及坦桑尼亚中上层渔业物种生产力的暂时增加。最后，我们讨论了卫星观测如何协助渔业管理机构预测低产期并减轻其潜在的负面经济影响。根据文献讨论了这种上升流的移动可能引起的局部生态系统变化。强调了对肯尼亚当地鱼类种群可能产生的负面影响，影响了渔民的生计和粮食安全，以及坦桑尼亚中上层渔业物种生产力的暂时增加。最后，我们讨论了卫星观测如何协助渔业管理机构预测低产期并减轻其潜在的负面经济影响。根据文献讨论了这种上升流的移动可能引起的局部生态系统变化。强调了对肯尼亚当地鱼类种群可能产生的负面影响，影响了渔民的生计和粮食安全，以及坦桑尼亚中上层渔业物种生产力的暂时增加。最后，我们讨论了卫星观测如何协助渔业管理机构预测低产期并减轻其潜在的负面经济影响。