The global ocean mass has significantly changed during recent decades, which may induce changes in the abyssal ocean circulation. Due to the lack of in situ observations, the response of the abyssal South China Sea (SCS) circulation to ocean mass changes remains unclear. The ocean state estimate, Estimating the Circulation and Climate of the Ocean (ECCO), provides the long-term ocean mass changes in terms of ocean bottom pressure (OBP). Here we use the ECCO OBP data to quantify decadal changes in the abyssal SCS circulation and reveal a weakening trend. The OBP gradient trend manifests in forms of an anomalous anticyclonic circulation that is intensified by topographic effects along the continental slopes to reduce the existing abyssal circulation. The weakening abyssal circulation corresponds to the weakening Luzon Strait overflow that yields a decreasing vorticity budget in the abyssal SCS.

中国南海深海环流的年代际减弱

中文摘要：近几十年来全球海洋水团已发生显著改变，这可能会引起深海环流的变化。但受限于实测数据的不足，中国南海（SCS）深海环流对海洋水团变化的响应仍不清楚。海洋状态估算，海洋环流和气候估算（ECCO）提供了基于海底压强（OBP）的海洋水团长期变化。本文使用ECCO OBP数据量化中国南海深海环流的年代际变化，并揭示其减弱的趋势。OBP梯度趋势以反气旋环流异常的形式表明通过沿陆坡地形效应的增强导致现存深海环流的减弱。深海环流的减弱对应于吕宋海峡溢流的减弱，并导致中国南海深海涡度守恒的下降。