The Xiamen Symposium on Marine Environmental Sciences (XMAS 2027)

The Western Pacific Basin (WPB) is the terminal convergence zone of the Pacific Meridional Overturning Circulation (PMOC), yet how gateway transport variability modulates its interior flow remains poorly understood. Integrating a sixteen-mooring array with GLORYS12V1 reanalysis (2010–2024) and a potential vorticity (PV) budget framework, we identify two principal interior pathways: a West Axis along the basin's western boundaries and a South Axis linking the New Guinea and Yap–Mariana Junction (YMJ) channels. Gateway forcing dominates basin dynamics: the YMJ and Izu–Ogasawara Ridge channels together explains 75.6% of total lateral PV flux variance, varying in antiphase with a one-month lag. YMJ transport variability strongly correlates with the South Axis, confirming a "side-forcing" mechanism that drives anticyclonic-to-cyclonic transitions along axes. Leveraging this relationship, observation-constrained flow field reconstruction corrects systematic sign errors in GLORYS12V1, reducing velocity biases by 20–70% at key mooring sites.