Xin Yuan, Qingye Wang, Dunxin Hu, Junqiao Feng, Fujun Wang, Zhizhao Tian

Published in Journal of Geophysical Research: Oceans, May 2024

Intraseasonal variability (ISV) in the meridional velocity of multi-layer currents in the Philippines Sea was investigated using near full-depth mooring observations deployed at 130°E, 11°N from September 2015 to October 2019 and the reanalysis data from 2015 to 2019. Prominent bimodal ISVs structures were detected in the power spectra of the meridional velocities at 45- and 62-days, occurring from the surface through to the bottom. Further analysis suggested that the identified ISV of 62-days in the upper 1,500 m was controlled by large-scale oceanic Rossby waves with a zonal wavelength of 687 km. The full-depth 45-days fluctuation is limited by the entire zonal width of the Philippines Basin, which is approximately 900 km. The 45-days variability modulated by the barotropic Rossby normal mode triggered by resonant wind forcing in the key region of 126°–140°E and 5°–13°N. Whereas the deep-layer 62-days fluctuation is limited by the basin width near the bottom (5,700 m), which is approximately 640 km. In addition, two super-intense ISV events occurred in the upper layers following the 2015/16 and 2018/19 El Niño events, which generally lagged the Niño 3.4 index by six/seven months. This study reveals the upper-layer ocean ISVs response in the western Pacific following El Niño events and triggering of the deep-layer ocean ISVs by the actual basin scale. Our findings provide a better understanding of the variations in full-depth currents in the western Pacific Ocean.

Yuan, X., Wang, Q., Hu, D., Feng, J., Wang, F., & Tian, Z. (2024). Intraseasonal variability of full-depth currents in the Philippine Sea. Journal of Geophysical Research: Oceans, 129, e2023JC019827. https://doi.org/10.1029/2023JC019827