[A-CG33] Multi-scale ocean-atmosphere interaction in the tropics

[ACG33-P03] Observed two variations of equatorial undercurrent in the western Pacific fellowing El Niño events

*yilong lyu¹ (1.Institute of Oceanology, Chinese Academy of Sciences)

Keywords:Tropical Western Pacific, Equatorial undercurrent, HYCOM, ENSO

The Equatorial Undercurrent (EUC) in the Western Pacific, a crucial subsurface current driven by trade winds, holds paramount importance in the region's ocean-atmosphere dynamics, particularly during El Niño events. This paper investigates the EUC's dynamics and responses following El Niño, utilizing mooring data from CASSON and JAMSTEC, coupled with the Oceanic General Circulation Model (OGCM). Our research reveals that the EUC demonstrates complex interannual variability in response to El Niño, with distinct changes in velocity and transport. Two groups of EUC changes were identified based on transport anomalies: one with unchanged or weakened EUC transport and another with significantly enhanced transport. Wind anomalies, particularly westerly wind events, were found to play a critical role in these variations. The OGCM experiments elucidate the dynamical processes driving the EUC variations. Results indicate that tropical wind stress anomalies, particularly during the decaying stage of El Niño, are pivotal in driving the observed changes in EUC transport. The study also emphasizing equatorial quasi-torsional oscillation and abnormal wind action. This comprehensive analysis enhances our understanding of EUC behavior in the context of climate variability and its broader implications for the western Pacific region.The Equatorial Undercurrent (EUC) in the Western Pacific, a crucial subsurface current driven by trade winds, holds paramount importance in the region's ocean-atmosphere dynamics, particularly during El Niño events. This paper investigates the EUC's dynamics and responses following El Niño, utilizing mooring data from CASSON and JAMSTEC, coupled with the Oceanic General Circulation Model (OGCM). Our research reveals that the EUC demonstrates complex interannual variability in response to El Niño, with distinct changes in velocity and transport. Two groups of EUC changes were identified based on transport anomalies: one with unchanged or weakened EUC transport and another with significantly enhanced transport. Wind anomalies, particularly westerly wind events, were found to play a critical role in these variations. The OGCM experiments elucidate the dynamical processes driving the EUC variations. Results indicate that tropical wind stress anomalies, particularly during the decaying stage of El Niño, are pivotal in driving the observed changes in EUC transport. The study also emphasizing equatorial quasi-torsional oscillation and abnormal wind action. This comprehensive analysis enhances our understanding of EUC behavior in the context of climate variability and its broader implications for the western Pacific region.The Equatorial Undercurrent (EUC) in the Western Pacific, a crucial subsurface current driven by trade winds, holds paramount importance in the region's ocean-atmosphere dynamics, particularly during El Niño events. This paper investigates the EUC's dynamics and responses following El Niño, utilizing mooring data from CASSON and JAMSTEC, coupled with the Oceanic General Circulation Model (OGCM). Our research reveals that the EUC demonstrates complex interannual variability in response to El Niño, with distinct changes in velocity and transport. Two groups of EUC changes were identified based on transport anomalies: one with unchanged or weakened EUC transport and another with significantly enhanced transport. Wind anomalies, particularly westerly wind events, were found to play a critical role in these variations. The OGCM experiments elucidate the dynamical processes driving the EUC variations. Results indicate that tropical wind stress anomalies, particularly during the decaying stage of El Niño, are pivotal in driving the observed changes in EUC transport. The study also emphasizing equatorial quasi-torsional oscillation and abnormal wind action. This comprehensive analysis enhances our understanding of EUC behavior in the context of climate variability and its broader implications for the western Pacific region.