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<p>The coastal upwelling off eastern Hainan Island (Qiongdong upwelling, QDU) is a significant seasonal upwelling system in the northwestern South China Sea, playing a crucial role in marine biological resources, the carbon cycle, and ecosystem dynamics. Using satellite observed sea surface temperature (SST) and atmospheric reanalysis datasets, combined with numerical simulation, this study investigates the impact of the boreal summer intraseasonal oscillation (BSISO) on the QDU. Results show that under the influence of BSISO, the QDU exhibits pronounced intraseasonal variation characteristics. The changes in QDU further influences SST and chlorophyll <i>a</i> (Chl-<i>a</i>), with their responses lagging behind upwelling by 2–4 d. The BSISO contains two components, BSISO1 (30–60 d period) and BSISO2 (10–20 d period), both of which can affect the QDU through modulating the wind field, with BSISO2 having a more substantial impact than BSISO1. During enhancing phases, the anomalous southerly winds strengthen the QDU through enhanced offshore Ekman transport and local Ekman pumping. During weakening phases, the anomalous northerly winds weaken the QDU through reduced offshore Ekman transport and local Ekman pumping. In this wind-driven modulation process, Ekman transport is found to play a major role. The combined effects of BSISO1 and BSISO2 are also discussed in this study: when both BSISO1 and BSISO2 are in enhancing phases, the anomalous southwesterly winds intensify the QDU to its strongest; conversely, when both are in weakening phases, the northeasterly winds suppress the QDU to its weakest.</p>

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Impact of boreal summer intraseasonal oscillation on the coastal upwelling off eastern Hainan Island

  • 期刊论文

  • 发表日期：

    2026年1月1日

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  • Yuanyuan Xiong,
  • Zheng Ling,
  • Xueming Zhu,
  • Chunlei Ma

摘要

The coastal upwelling off eastern Hainan Island (Qiongdong upwelling, QDU) is a significant seasonal upwelling system in the northwestern South China Sea, playing a crucial role in marine biological resources, the carbon cycle, and ecosystem dynamics. Using satellite observed sea surface temperature (SST) and atmospheric reanalysis datasets, combined with numerical simulation, this study investigates the impact of the boreal summer intraseasonal oscillation (BSISO) on the QDU. Results show that under the influence of BSISO, the QDU exhibits pronounced intraseasonal variation characteristics. The changes in QDU further influences SST and chlorophyll a (Chl-a), with their responses lagging behind upwelling by 2–4 d. The BSISO contains two components, BSISO1 (30–60 d period) and BSISO2 (10–20 d period), both of which can affect the QDU through modulating the wind field, with BSISO2 having a more substantial impact than BSISO1. During enhancing phases, the anomalous southerly winds strengthen the QDU through enhanced offshore Ekman transport and local Ekman pumping. During weakening phases, the anomalous northerly winds weaken the QDU through reduced offshore Ekman transport and local Ekman pumping. In this wind-driven modulation process, Ekman transport is found to play a major role. The combined effects of BSISO1 and BSISO2 are also discussed in this study: when both BSISO1 and BSISO2 are in enhancing phases, the anomalous southwesterly winds intensify the QDU to its strongest; conversely, when both are in weakening phases, the northeasterly winds suppress the QDU to its weakest.