[A-OS18] Physical Oceanography (General)

[AOS18-14] Deep reaching wave energy-flux in the off-equatorial central and western regions of the Pacific Ocean during the El Niño and La Niña events

*Borui Wu¹, Hidenori Aiki^2,3 (1.Graduate School of Environmental Studies, Nagoya University, 2.Institute for Space-Earth Environmental Research, Nagoya University, 3.Application Laboratory, Japan Agency for Marine-Earth Science and Technology)

Keywords:Kelvin waves, Rossby waves, wave energy penetration, tropical Pacific Ocean, ENSO cycle

The present study has investigated the vertical structure of wave energy 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 Kelvin waves distinguishes downwelling and upwelling waves associated with El Niño and La Niña, respectively, and the vertical energy flux of off-equatorial Rossby waves is generally symmetric along the equator with a greater magnitude in the northern hemisphere. The authors find that the vertical transfer of wave energy is particularly deep in the North Central Tropical Pacific Ocean and the Southwestern Tropical 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. These vertical fluxes reach a downward peak during El Niño period, followed by a shift to an upward peak when the subsequent La Niña event intensifies. The energy input by wind forcing in the central equatorial Pacific Ocean is a major source of downward peaks in both the North Central Tropical Pacific Ocean and Southwestern Tropical Pacific Ocean. While the wave reflection at the eastern boundary mainly contributes to the downward peak in the North Central Tropical Pacific Ocean.