The Philippine Sea (PS) is a critical area for the surface tropical/subtropical gyres in the western North Pacific, playing a vital role in regional and global circulations. In this study, we utilize well-validated simulation results from the China Sea Multi-Scale Ocean Modeling System (CMOMS) to examine the three-dimensional circulations in the PS, with a specific focus on the less-known intermediate depths and abyss. Our analysis, based on the Stokes Theorem, reveals the presence of anticyclonic circulations in the upper (<600 m) and middle (600-2400 m) layers with distinct dynamic mechanisms, as well as a cyclonic circulation in the abyssal layer (>2400 m). We apply the Layered-Integrated Vorticity Equation (LIVE) in the PS to diagnose sources/sinks for layered circulation. From the top to bottom, the vorticity horizontal advection, the joint effects of baroclinicity and relief (JEBAR), and vertical viscosity induced by bottom friction are identified as the intrinsic dynamic response to the layered circulation in each respective layer. Moreover, the dynamic analysis underscores the PS as a critical region for the Pacific meridional overturning circulation due to the significant upwelling. We also identify the extrinsic influx/outflux of vorticity for the layered circulation. These new insights enhance our understanding of the circulation mechanisms in the PS.
 

physical oceanography