996 / 2024-09-20 00:40:02

Long-term characteristic and variability of the current system in the western Pacific: kinematic study

Western Boundary Current,Western Pacific Ocean

The ocean circulation system in the Western Pacific consists of western boundary currents (WBCs, Kuroshio Current, Mindanao Current, Ryuku Current) and connected North Equatorial Current (NEC). The system as one of the most complicated current systems, is vital for regulating the exchange of mass, energy, and heat transport between the open ocean and the diverse marginal seas. Previous studies in Western Pacific circulations most focused on the variability of the circulations in specific sections that provided a spatiotemporally limited view of the conditions. Using the high-resolution, validated three-dimensional and time-dependent China Sea Multi-scale Ocean Modeling System ((CMOMS, https://odmp.hkust.edu.hk/cmoms/), we quantitatively characterize the variability of the western boundary currents and related circulations in Western Pacific, and investigate their underlying physical processes. Based on physically sensible definitions of the jet stream along streamline coordinate, we identify characteristic width, depth, and along-/cross-stream transports and their unique spatiotemporal variability in the 3D current system. We investigate the underlying dynamics of WBCs and NEC as an integrated NEC-WBC current system. Our findings reveal a prominent seasonal cycle and the variability of mean and eddy kinetic energy, volume transport, heat transport and vorticity balance in the interlinked NEC, Kuroshio Current (KC), Mindanao Current (MC) and Ryuku Current (RC). The dynamics of the variability subject to the controls of momentum and vorticity dynamics are investigated. By resolving three-dimensional, spatiotemporal variability in NEC-MC-KC-RC, the study provides a new understanding to the dynamic connections in the Western Pacific Current system.