Coherent Interannual-Decadal Potential Temperature Variability in the Tropical-North Pacific Ocean and Deep South China Sea

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. This study utilizes multivariate empirical orthogonal function analysis to examine long-term hydrographic observations and identify coherent variations in surface temperature anomalies in the Tropical and North Pacific Ocean. The leading mode displays in-phase combinations of the East Pacific El Nino and warm Pacific Decadal Oscillation. The second mode displays a Central Pacific El Nino and North Pacific Meridional Mode-like mode. The third mode resembles a Central Pacific El Nino and Victoria Mode-like mode. The objective is to comprehend the synergies between the climatic variabilities in the Tropical and North Pacific Ocean, as well as the processes by which the predominant climate variabilities regulate the undocumented potential temperature variabilities in the deep South China Sea. Extrinsic forcings in the Tropical and North Pacific Ocean regulate the interannual-decadal temperature variabilities by modulating the Luzon Strait Transport. On the atmospheric bridge, these extrinsic forcings affect the upper-layer Luzon Strait Transport by altering the local Ekman transport and Kuroshio intrusion associated with the bifurcation of the North Equatorial Current. On the oceanic pathway, climate variabilities disturb the deep-layer Luzon Strait Transport by changing the ocean bottom pressure between the two sides of the Luzon Strait. Coherent climate variabilities in the Tropical and North Pacific Ocean are obtained through MVEOF analysisPotential temperature observations from the deep South China Sea indicate interannual-decadal variabilityClimate variabilities affect deep temperature variability through the changing atmospheric bridge and oceanic pathway