Climate variability over the Tropical and North Pacific Ocean (TPO and NPO, respectively) modulates marginal sea variability. The South China Sea (SCS), the largest marginal sea in the western NPO, is an outstanding example of a region that responds quickly to climate change. However, there is considerable uncertainty regarding the response of the deep SCS to large-scale climate variability. Multivariate empirical orthogonal function analysis revealed three prominent modes of interconnected temperature anomaly fluctuations within the TPO and NPO. These coherent modes highlight the interactive dynamics among climate variations and reveal their modulation mechanisms for previously less explored potential temperature variabilities in the deep SCS. On the atmospheric bridge, external forces modify the upper-layer Luzon Strait Transport (LST) by adjusting the Ekman transport and Kuroshio intrusion. For the oceanic pathway, climate variations disturb the deep-layer LST by adjusting the barotropic flows in the upper layer.

Plain Language Summary

This study utilizes multivariate empirical orthogonal function analysisto examine long-term hydrographic observations and identify coherent variations in surface temperatureanomalies in the Tropical and North Pacific Ocean. The leading mode displays in-phase combinations of theEast Pacific El Niño and warm Pacific Decadal Oscillation. The second mode displays a Central Pacific ElNiño and North Pacific Meridional Mode-like mode. The third mode resembles a Central Pacific El Niño andVictoria Mode-like mode. The objective is to comprehend the synergies between the climatic variabilities inthe Tropical and North Pacific Ocean, as well as the processes by which the predominant climate variabilitiesregulate the undocumented potential temperature variabilities in the deep South China Sea. Extrinsic forcings inthe Tropical and North Pacific Ocean regulate the interannual–decadal temperature variabilities by modulatingthe Luzon Strait Transport. On the atmospheric bridge, these extrinsic forcings affect the upper-layer LuzonStrait Transport by altering the local Ekman transport and Kuroshio intrusion associated with the bifurcation ofthe North Equatorial Current. On the oceanic pathway, climate variabilities disturb the deep-layer Luzon StraitTransport by changing the ocean bottom pressure between the two sides of the Luzon Strait.