ENSO-Modulated Variability in Winter Shelf Circulation of the Northern South China Sea

IF 3.3 2区 地球科学 Q1 OCEANOGRAPHY
Yunping Song, Yuxin Lin, Qi Quan, Tingting Zu, Zhongya Cai, Peng Zhan, Zhiqiang Liu
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Abstract

We combined long-term observational data from 1999 to 2021 with numerical simulations to study the seasonal changes in the currents along the continental shelf in the Northern South China Sea (NSCS) during winter and how these changes relate to the El Niño-Southern Oscillation (ENSO). Our results indicate that during El Niño events, the eastward movement of the warm pool in the tropical Pacific Ocean not only leads to colder sea surface temperatures and a stronger Kuroshio current intrusion but also significantly affects the formation of a high-pressure system in the subtropics over the NSCS. In El Niño years, an anomalous anticyclonic wind stress curl in the South China Sea weakens the northeast winter monsoon, which in turn weakens the cyclonic shelf circulation. The first principal component from the multivariate empirical orthogonal function decomposition, which accounts for 49.02% of the total variance, shows a significant correlation of 0.64 with the Niño 3.4 index, indicating the circulation's sensitivity to tropical climate changes. Our analysis of the winter shelf circulation, based on the along-isobath depth-integrated vorticity equation, reveals that the exchange of water across the isobaths over the shelf is mainly controlled by the nonlinear advection of relative vorticity, with wind stress curl and bottom stress curl playing a less significant role in regulating the structure of these exchanges. The combined effect of baroclinic forces and topography likely governs the dynamics over the slope.

受厄尔尼诺/南方涛动影响的南海北部冬季大陆架环流变化
我们将 1999 年至 2021 年的长期观测数据与数值模拟相结合,研究了冬季南海北部大陆架海流的季节性变化,以及这些变化与厄尔尼诺-南方涛动(ENSO)的关系。我们的研究结果表明,在厄尔尼诺现象期间,热带太平洋暖池的东移不仅会导致海面温度降低和黑潮入侵增强,而且会显著影响南海北部大陆架上空亚热带高压系统的形成。在厄尔尼诺年,南海的反气旋风应力异常卷曲削弱了东北冬季季风,进而削弱了气旋陆架环流。多变量经验正交函数分解的第一个主成分占总方差的 49.02%,与 3.4 尼诺指数的相关性为 0.64,表明环流对热带气候变化的敏感性。我们根据沿等深线深度积分涡度方程对冬季陆架环流进行的分析表明,陆架上跨等深线的水体交换主要受相对涡度的非线性平流控制,而风应力卷曲和底应力卷曲在调节这些交换结构中的作用并不明显。气压和地形的共同作用可能会影响斜坡上的动态变化。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Geophysical Research-Oceans
Journal of Geophysical Research-Oceans Earth and Planetary Sciences-Oceanography
CiteScore
7.00
自引率
13.90%
发文量
429
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