基于卫星地转流线的表层黑潮入侵南海的年际与年代际变化

Interannual and Decadal Variation of the Surface Kuroshio Intrusion Into the South China Sea Based on Satellite Geostrophic Streamlines

  • 摘要: 黑潮入侵对南海的动力和生态环境变化有重要影响,为研究其年际和年代际变异规律,本文基于卫星高度计数据和黑潮地转流线形态,量化了黑潮流套和分支入侵南海的时空变化,并统计分析了二者流量的年际、年代际变异与太平洋年代际振荡(Pacific Decadal Oscillation, PDO)和厄尔尼诺-南方涛动(El Niño-Southern Oscillation, ENSO)的关系。研究结果表明:①在年际尺度上,当PDO指数处于负位相时,Niño3.4指数与流套入 侵流量呈负相关,相关系数达到−0.55(90%显著性检验为0.352),即当Niño3.4指数增大时,流套入侵减弱,Niño3.4指数减小时,流套入侵增强,这与ENSO对吕宋海峡处纬向风应力的调控作用有关,而当PDO指数处于正位相时,Niño3.4指数与黑潮流套入侵流量的相关系数仅为−0.07(90%显著性检验为0.549),两者之间不存在显著相关;PDO指数与黑潮分支入侵流量呈正相关,相关系数为0.50(90%显著性检验为0.296),这与PDO对副热带海区风应力旋度调控引起的北赤道流分叉点位置变化有关。②在年代际尺度上,在PDO指数暖(冷)位相期间,流套入侵流量与分支入侵流量均增大(减弱),两类入侵流量与PDO指数的相关系数分别为0.57和0.72(90%显著性检验为0.296),这与PDO造成的副热带海区风应力旋度的年代际变化造成的北赤道流分叉点位置变化密切相关。本研究量化并统计了不同黑潮入侵形态的流量及其年际和年代际变化规律,对于进一步理解黑潮入侵南海的时空演变和动力机制,提升黑潮入侵南海的可预报性具有一定的促进作用。

     

    Abstract: The Kuroshio intrusion (KI) has significant implications for the dynamics and ecological environment of the South China Sea (SCS). This study employs the satellite altimetry data and geostrophic streamline morphology of the Kuroshio to quantify the spatiotemporal changes of the looping and leaking intrusion transport of the Kuroshio into the SCS. The study also uses statistical methods to analyze the interannual and decadal variability of the KI in relation to the Pacific Decadal Oscillation (PDO) and the El Niño-Southern Oscillation (ENSO). The result indicates that: ①On the interannual timescale, when the PDO is in its negative phase, the ENSO activity is negatively correlated with the volume of the looping intrusion, and the correlation coefficient was −0.55, which means that as Niño3.4 index increases (decreases), the looping intrusion weakens (enhances). This is due to the regulatory role of ENSO on the zonal wind stress at the Luzon Strait, the change of the invasion transport is caused by the change of the Asian monsoon. When the PDO is in positive phase, there is no significant correlation between the ENSO and the looping intrusion, the correlation coefficient between them is merely −0.07. The PDO is positively correlated with the transport of the leaking intrusion, the correlation coefficient was 0.5, which may be related to the position changes of the North Equatorial Current bifurcation caused by the influence of PDO on the wind stress curl over the subtropical gyre. ②On the decadal timescale, during the warm (cold) phase of PDO, both the transport of looping and leaking intrusion increase (decrease), the correlation coefficients with PDO were 0.57 and 0.72, respectively, leading to an enhancement (weakening) of the KI into the SCS. This is closely related to the decadal changes in the wind stress curl caused by the PDO in subtropical region, which affects the location of the North Equatorial Current bifurcation, and then affects the change of the KI. The study quantifies and statistically analyzes the transports of the KI with different forms and their interannual and decadal variability, which can promote a better understanding of the mechanisms of the KI into the SCS and improve the predictability of such events.

     

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