The observed North Equatorial Counter Current in the far western Pacific Ocean during the 2014-2016 El Niño

Abstract The structure and variations of the North Equatorial Counter Current (NECC) in far western Pacific Ocean during 2014-2016 are investigated using repeated in-situ hydrographic data, altimeter Argo reanalysis data. NECC shifted ~1 degree southward intensified significantly with its transport exceeding 40 Sv (1 = 10 6 m 3 s -1 ), nearly double climatology value, developing phase 2015/16 El Niño event. Observations show that exerted a comparable impact on extreme 1997/98 Ocean. Baroclinic instability provided primary energy source for eddy kinetic (EKE) Niño, which differs from traditional understanding EKE as barotropic low latitude ocean. enhanced vertical shear reduced density jump between layer subsurface Subsurface (NESC) renders NECC–NESC system baroclinically unstable phase. eddy-mean flow interactions here diverse associated various states Southern Oscillation (ENSO).