An Intermediate Current in Tropical North Pacific Observed by Moored Current Meters

Abstract Six years of current meter observation from a subsurface mooring at 130°E, 8.5°N captured an eastward flow below the North Equatorial Undercurrent (NEUC) between 1,500 and 3,000 m. This flow, named Lower‐NEUC, has mean velocity of 0.73 ± 0.08 cm/s and 1.05 ± 0.08 cm/s at 2,000 and 2,500 m, respectively. Its spatial distribution is studied using Argo absolute geostrophic velocity data and ocean reanalysis. In the northwestern Pacific, Lower‐NEUC shifts poleward with increasing longitude and is wider in Argo absolute geostrophic velocity data (around 300 km) and narrower in reanalysis (around 150 km). Vertically, the core of Lower‐NEUC lies mostly between 27.5 and 27.6 in reanalysis, shallower compared to mooring observation. Reanalysis data shows L‐NEUC's generation is connected to deep eddies. After proving that L‐NEUC is not a result of averaging west‐translating eddies, we showed that L‐NEUC is generated by eddy potential vorticity flux convergence.