Yu, Dai-JyunDai-JyunYuChang, Ming-HueiMing-HueiChangYang, Kai-ChiehKai-ChiehYangJan, SenSenJanMalugao, Mac Euan DMac Euan DMalugao2026-02-262026-02-262025-10-01https://www.scopus.com/pages/publications/105028629542https://scholars.lib.ntu.edu.tw/handle/123456789/736043The influence of extreme climate events on regional water mass variability in the western North Pacific (NP) remains poorly understood. In 2017, Seaglider and Argo float observations revealed an anomalously high-salinity (S > 35) North Pacific Tropical Water (NPTW) in the western boundary region. To investigate the origin of this anomaly, we analyzed in situ hydrographic data, satellite-derived surface fluxes, and model-based ocean reanalysis. Results indicate that the high-salinity NPTW was linked to anomalous atmospheric and oceanic conditions associated with the 2015–2016 extreme El Niño. During this period, an expanded region of excess evaporation over precipitation (E–P) in the eastern–central NP likely enhanced surface salinity, which was subsequently subducted and advected westward via zonal currents. This mechanism led to the westward migration of saline NPTW over a two-year period, culminating in the replacement of the less saline West Philippine Sea Tropical Water by 2017. These findings highlight a delayed and basin-scale impact of extreme El Niño events on regional subsurface salinity distribution in the western North Pacific.El Niñosalinity anomalySeagliderwater masswestern North Pacificjournal article10.1088/2515-7620/ae15db