434 / 2024-09-16 22:51:40

Deep reaching wave energy-flux in the off-equatorial Pacific Ocean during the El Niño and La Niña events

Rossby wave,Kelvin wave,vertical stru,El Nino/Southern Oscillation,Western Pacific Warm Pool

The present study has investigated the vertically propagating waves in the tropical Pacific Ocean based on the result of a linear, continuously stratified ocean model driven by interannual wind forcing, using a seamless energy flux diagnosis scheme which smoothly connects the tropical and subtropical zones. In the eastern Pacific Ocean, the vertical energy flux of equatorial and coastal Kelvin waves could distinguish downwelling and upwelling waves associated with El Niño and La Niña, and the vertical energy flux of off-equatorial Rossby waves is symmetrically distributed along the equator. The authors find that the vertical transfer of wave energy is particularly deep in the off-equatorial regions of the western Pacific Ocean. A unique feature of the vertical transfer of wave energy is its tallness (down to 1000–2000m depth), in contrast to the vertical profiles of energy transfers in the eastern tropical Pacific Ocean. This vertical flux is attributed to off-equatorial Rossby waves and directed downward (upward) during El Niño and upward (downward) during La Niña in the southern (northern) side of the equator. In the southwestern tropical Pacific Ocean, the signal of vertical energy flux at subsurface layer tends to overlap the Western Pacific Warm Pool, with its eastern edge moving eastward during El Niño and westward during La Niña.