Observed Deep‐Reaching Signatures of the Madden‐Julian Oscillation in the Ocean Circulation of the Western Tropical Pacific

Abstract

AbstractProminent intraseasonal variability (ISV) of ocean currents was detected by two subsurface moorings deployed at 140°E, 2°N, and 4.7°N during 2014–2018 and shown to be largely induced by westerly wind bursts (WWBs) associated with passages of Madden‐Julian oscillations (MJOs). The North Equatorial Countercurrent between 60 and 200 m is enhanced (attenuated) by 6–8 cm/s prior (subsequent) to the WWB. Current anomalies below 300 m are as large as 2–3 cm/s, close in magnitude to the mean velocities of the North Equatorial Subsurface Current and North Subsurface Countercurrent. The ISV in the upper 600 m shows a vertical dipole structure at 2°N and vertically coherent anomalies at 4.7°N. Further analysis combining satellite data reveals local recirculation structures generated by wind‐forced Rossby waves. Ocean model experiments confirm the importance of the MJO's wind forcing in causing these subsurface ocean ISVs.