Interdecadal modulation of ENSO amplitude by the Atlantic multi-decadal oscillation (AMO)
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Interdecadal modulation of ENSO amplitude by the Atlantic multi‑decadal oscillation (AMO) Yuhan Gong1 · Tim Li1,2 · Lin Chen1,3,4 Received: 27 August 2019 / Accepted: 29 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The impact of the Atlantic Multi-decadal Oscillation (AMO) on the ENSO amplitude was investigated through observational analyses. During the past 90 years the interdecadal variability of ENSO intensity is significantly correlated with the AMO. ENSO variability was strengthened (weakened) during a negative (positive) AMO phase. An ocean mixed layer heat budget analysis reveals that the thermocline feedback is the main process regulating AMO negative phase dependent ENSO growth characteristic. A further examination indicates that a strengthened atmospheric response to unit SST anomaly, an enhanced thermocline response to unit wind stress forcing and a strengthened subsurface temperature response to unit thermocline variation all contribute to the enhanced thermocline feedback during the negative phase of AMO. Such changes are attributed to the increase of background moisture, the weakening of mean subtropical cell (STC) and increase of upper ocean vertical temperature gradient respectively. Keywords AMO · Interdecadal change of ENSO amplitude · Thermocline feedback · Zonal advective feedback · Mixed layer heat budget
1 Introduction El Niño-Southern Oscillation (ENSO) is the strongest interannual variability in the global climate system. It is characterized by a large-scale sea surface temperature (SST) * Yuhan Gong [email protected] 1
Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environmental Change (ILCEC)/ Collaborative Innovation Center On Forecast and Evaluation of Meteorological Disasters (CIC‑FEMD), Nanjing University of Information Science and Technology, Nanjing, China
2
Department of Atmospheric Sciences, School of Ocean and Earth Science and Technology, International Pacific Research Center, University of Hawaii At Manoa, Honolulu, HI 96822, USA
3
State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
4
State Key Laboratory of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
anomaly pattern in the tropical Pacific and remote precipitation and circulation response in a variety of regions (Ropelewski and Halpert 1989; Philander 1990; Halpert and Ropelewski 1992). The structure and evolution characteristics of ENSO has been described by many previous studies (e.g., Rasmusson and Carpenter 1982; Philander 1990; Li 1997; Neelin et al. 1998; see Li and Hsu 2017 for a recent review). One of important characteristics of ENSO is its interdecadal variability (Trenberth and Shea 1987; Wang 1995; Gu and Philander 1997; Wang and An 2002; Lübbecke and Mcphaden 2014).
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