Investigating the ENSO amplitude reduction during the mid-Holocene in the perspective of ENSO recharge-discharge oscillator
ZHANG Keying
SUN Jingwen
XIE Ruihuang
Abstract：Using the air-sea coupled model simulations from CMIP6 and PMIP4,this study extracts the intrinsic modes of mid-Holocene ENSO(El Niño-Southern Oscillation)in the perspective of the ENSO recharge-discharge oscillator via the linear inverse model method,thereby elucidating the dynamic mechanisms for the ENSO amplitude reduction during this period.The research reveals that the reduced ENSO amplitude in the mid-Holocene results from a decreased growth rate of the intrinsic ENSO mode,which is linked to weakened thermocline feedback and zonal advection feedback.The results are as follows.(1)The weakened thermocline feedback is primarily driven by a significant reduction in the response strength of the zonal slope of the thermocline to the wind stress over the equatorial central Pacific during autumn and winter of the mid-Holocene.(2)Simultaneously,the weakened zonal advection feedback is attributed to a notable decline in the response strength of anomalous zonal currents in the equatorial eastern Pacific to the wind stress over the equatorial central Pacific during summer-winter.The weakening of these two critical positive feedbacks reduces the development rate of the initial ENSO sea surface temperature anomalies emerged in summer,ultimately reducing the ENSO amplitude in winter.(3)In contrast,the enhanced ENSO amplitude in some models is associated with the significantly strengthened thermocline feedback,although the zonal advective feedback is weakened as well but to a smaller extent,compared to the enhancement of thermocline feedback.
Keywords：mid-HoloceneENSO amplitude reductionrecharge-discharge oscillatorintrinsic ENSO modethermocline feedbackzonal advective feedback
Publication Date：2025-12-30
Online Publishing Date：2026-05-22(First online date of this platform, not the publication date of the document)
Pages：16( 71-86 )