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阿曼沿岸上升流对厄尔尼诺-南方涛动和印度洋偶极子的响应机制

Response mechanism of the Oman coastal upwelling to El Niño-Southern Oscillation and Indian Ocean Dipole

  • 摘要: 沿岸上升流把下层海洋低温、高营养盐、低溶解氧的海水带到上层,对局地气候、生态环境和海洋渔业生产具有重要的影响。受印度夏季风的驱动,在阿曼和索马里沿岸产生全球最强的上升流之一。为了探究该区上升流对厄尔尼诺-南方涛动、印度洋偶极子的响应,本研究基于海表面温度、海面风场、海面热通量等数据,揭示夏季阿曼沿岸上升流对厄尔尼诺-南方涛动、印度洋偶极子的响应机制。结果表明,厄尔尼诺衰减年期间,阿曼沿岸上升流区出现东北风异常,削弱了有利于上升流的盛行西南季风,导致上升流减弱。反之,拉尼娜衰减年期间,阿曼沿岸上升流区出现西南风异常,加强了有利于上升流的盛行西南季风,导致上升流增强。正(负)印度洋偶极子事件在赤道印度洋以北激发出一个反气旋(气旋)式风场异常场,但阿曼沿岸上升流区并没有位于反气旋(气旋)式风场异常场的主轴,因此印度洋偶极子事件导致的风场异常对阿曼沿岸上升流的影响很小。

     

    Abstract: Coastal upwelling brings low temperature, high nutrient and low dissolved oxygen water from deep ocean to the upper layers, significantly impacting local climate, ecological environments, and marine fisheries. Influenced by the summer Indian monsoon, the coastal regions of Oman and Somalia become one of the strongest upwelling zones in the world. To understand the relationship between this upwelling and the larger-scale events such as the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), this study investigated the response mechanism of the summer upwelling along the Oman coast to ENSO and IOD based on remote sensing data such as the sea surface temperature, wind and heat flux. Results indicate that during El Niño decaying years, the anomalous northeasterly winds in the Oman coastal upwelling zone weaken the prevailing southwesterly monsoon which is favorable for the upwelling, and finally result in a weakened upwelling. In contrast, during La Niña decaying years, the anomalous southwesterly winds strengthen the prevailing southwesterly monsoon, which result in an enhanced upwelling. Positive (negative) IOD events induce an anticyclonic (cyclonic) anomalous wind field north of the equatorial Indian Ocean. However, the wind anomalies induced by IOD events have little impact on the upwelling along the Oman coast, for the upwelling zone is not located within the main axis of the anomalous wind field area.

     

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