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The Subsurface Mode Tropical Instability Waves in the Equatorial Pacific Ocean and Their Impacts on Shear and Mixing
Author(s) -
Liu Chuanyu,
Fang Liyuan,
Köhl Armin,
Liu Zhiyu,
Smyth William D.,
Wang Fan
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl085123
Subject(s) - baroclinity , barotropic fluid , equator , instability , geology , amplitude , shear (geology) , climatology , atmospheric sciences , rossby wave , sea surface height , mixing (physics) , physics , mechanics , geodesy , sea surface temperature , latitude , optics , petrology , quantum mechanics
The tropical instability waves (TIWs) in the eastern tropical Pacific have generally been considered as surface‐intensified structures resembling the first baroclinic mode. Here, we report on the existence of subsurface‐intensified TIWs on the equator. These TIWs are primarily manifested in zonal velocities, inducing maximum velocity oscillations at 70–90 m depth with amplitudes of 0.1–0.2 m/s and periods of 5–20 days. They account for ~20% of the variance at 5‐ to 30‐day periods, with another ~50% being contributed by the surface‐intensified TIWs. These waves are most significant during the TIW seasons; they are energized in part by barotropic instabilities and usually last for 3–7 months. Via interacting with the mean flow, they can induce strong out‐of‐phase shear changes between ~50‐m depth and just above the Equatorial Undercurrent core and may lead to complex diapycnal mixing structures. Their horizontal structures, generation mechanism(s), and large‐scale impacts remain to be disclosed.