南海海表盐度变化特征及机制研究

Study on the Variation Characteristics and Mechanism of Sea Surface Salinity in South China Sea

海表面盐度(Sea surface salinity,SSS)的变化机制复杂,主要受海气交换及海洋环流过程影响。南海SSS存在显著的年际及年代际变化,受厄尔尼诺与南方涛动(El Nino-Southern oscillation,ENSO)和太平洋十年涛动(Pacific decadal oscillation,PDO)的复合作用机制尚不明确。本文融合海洋再分析数据和卫星遥感数据,处理生成151 a(1871—2021年)的长期南海SSS数据集,采用EOF和相关分析等方法,分析了南海SSS的长期时空变化特征及机制。研究结果表明:近150年来,南海SSS整体变化不明显,但1940—1958年SSS显著上升(每10年上升0.31);珠江口和吕宋海峡受径流和黑潮作用,SSS变化幅度最大(每10年为-0.04和每10年为0.03);南海SSS整体变化主要由降水和黑潮控制,相关系数分别为-0.41和-0.49,南海陆架和近海海域SSS受河流径流影响显著,相关系数为-0.45;ENSO在年际尺度上控制南海的降水,PDO在年代际尺度上影响黑潮入侵南海的变化,当PDO正位相时,厄尔尼诺事件会导致降水减少,同时黑潮入侵南海强度增加,两者共同作用使南海SSS显著上升。本研究对理解南海海气交换和海洋环流变化有重要意义。

The variation mechanism of Sea Surface Salinity(SSS)is complex and mainly affected by air-sea exchange and ocean circulation processes.There are significant inter-annual and inter-decadal variations of SSS in the South China Sea,and the compound effects of ENSO and PDO is still unclear.In this paper,the long-term SSS dataset of the South China Sea for 151 years(1871—2021)was generated by integrating Marine reanalysis data and satellite remote sensing data.The long-term spatio-temporal characteristics and mechanisms of SSS in the South China Sea were analyzed by using EOF and correlation analysis methods.The results show that the overall SSS of the South China Sea has not changed significantly in the past 150 years,but the SSS increased significantly(0.31per/decade)from 1940 to 1958.The variation of SSS in the Pearl River Estuary and Luzon Strait under the influence of runoff and Kuroshio was the largest(-0.04 and 0.03 per/decade).The overall variation of SSS in the South China Sea was mainly controlled by precipitation and Kuroshio,with correlation coefficients of-0.41 and-0.49,respectively.SSS in the continental shelf and offshore areas of the South China Sea were significantly affected by river runoff,with correlation coefficients of-0.51.ENSO controls the precipitation in the South China Sea in the inter-annual scale,while PDO affects the change of the invasion of the Kuroshio in the South China Sea in the inter-decadal scale.When the PDO is in the positive phase,the occurrence of El Nino will lead to the decrease of precipitation,and the intensity of the invasion of the Kuroshio in the South China Sea will increase,so the SSS of the South China Sea increases significantly.This study is of great significance for understanding air-sea exchange and ocean circulation in the South China Sea.