Changes in ENSO amplitude under climate warming and cooling

Wang, Yingying; Luo, Yiyong; Lu, Jian; Liu, Fukai

doi:10.1007/s00382-018-4224-1

Cited by 25 publications

(16 citation statements)

References 43 publications

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“…11c). Here, the relationship between the change in u′ response and that in w′ response is consistent with the findings of previous studies (e.g., Chen et al 2015Chen et al , 2017Wang et al 2018), in which the authors pointed out that the change in w′ response to ′ x in the equatorial region was generally coherent with the change in u′ response to ′…”

Section: The Ek Feedbacksupporting

confidence: 92%

“…The BJ index proposed by Jin et al (2006) has been employed in some recent studies for ENSO stability analysis (Kim and Jin 2011a, b;Jin 2014a, b;Liu et al 2014;Chen et al 2016;Hua et al 2018;Wang et al 2018). The method allows us to assess the contribution of different terms to the growth rate of a coupled ocean-atmosphere instability.…”

Section: The Bj Indexmentioning

confidence: 99%

“…2.2) to quantitatively diagnose the changes in ENSO intensity and its relevant air-sea feedback processes in the MH, and to reveal the physical mechanisms behind ENSO intensity change. It is worth mentioning that the BJ index, as a relatively new approach, has been widely employed as an effective tool in some recent studies to address the issues associated with ENSO intensity change (e.g., Kim et al 2014a;Liu et al 2014;Wang et al 2018).…”

Section: Introductionmentioning

confidence: 99%

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Drivers of reduced ENSO variability in mid-Holocene in a coupled model

Chen

Wang

et al. 2018

Clim Dyn

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The drivers of El Niño-Southern Oscillation (ENSO) intensity change during the mid-Holocene (MH) are investigated through employing a coupled model that exhibits excellent performance in simulating the present-day ENSO behaviors. The model shows a 28% decrease in ENSO intensity in the MH simulation compared to the pre-industrial (PI) simulation, showing an agreement with the ranges indicated by the paleo-proxies. Based on quantitative analyses, we reveal that the changes in the oceanic dynamic processes (including the thermocline, zonal-advection, and Ekman feedback terms, in the order from being most to least important) were the major drivers of the reduced ENSO intensity in the MH. Further diagnosis analyses show that the weakening in all three oceanic dynamic terms could be traced back to the weakened thermocline response to zonal wind stress anomaly in the MH compared to that in the PI. Such weakened thermocline response was due to the relatively flattened meridional structure of ENSO-related interannual anomaly field (e.g., zonal wind stress anomaly field) in the MH, which arose from the strengthening of the mean meridional overturning circulation, namely, the mean Pacific subtropical cell (STC). The process-oriented analyses throughout this study suggest a critical linkage between ENSO intensity change and mean STC change in the MH, through documenting how the mean STC change altered the oceanic dynamic processes and thus drove the ENSO intensity change.

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Section: The Ek Feedbacksupporting

confidence: 92%

Section: The Bj Indexmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Drivers of reduced ENSO variability in mid-Holocene in a coupled model

Chen

Wang

et al. 2018

Clim Dyn

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“…Generally speaking, the diagnostic results based on the MLHB analyses in the supplementary material are consistent with the BJ index diagnostic results above. This result supports that BJ index can be a useful tool for investigating ENSO intensity change in response to the external forcing change, which is also found in a relevant study by Wang et al (2018). Additionally, through conducting the MLHB analyses step-by-step, we found that the nonlinear processes (e.g., the term 3, term 6 and term in Eq.…”

Section: Changes In Bj Index In Mh and Its Relationship With Enso Varsupporting

confidence: 89%

“…Building on the framework in Jin et al 2006, Kim and Jin (2011a, b) further completed the tool of BJ index. Recently, the BJ index has been widely used to study the scientific issues associated with the ENSO variability change (e.g., Kim et al 2014a, b;Liu et al 2014;Chen et al 2016a, b;Lu et al 2016;Zhu et al 2017;Chen et al 2018;Wang et al 2018). Following Kim and Jin (2011a, b), the specific formulations of BJ index employed in this study are shown below:…”

Section: Bj Indexmentioning

confidence: 99%

Towards understanding the suppressed ENSO activity during mid-Holocene in PMIP2 and PMIP3 simulations

2019

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The mechanisms of El Niño-Southern Oscillation (ENSO) variability change during the mid-Holocene (MH) were investigated through analyzing the model simulations from the Paleoclimate Modelling Intercomparison Project Phases (PMIP) phase-2 and phase-3. The majority of PMIP2 and PMIP3 model simulations show a lower level of ENSO activity in the MH simulation compared to the pre-industrial (PI) simulation, which is qualitatively consistent with that inferred from the paleoclimate proxies. Through employing the Bjerknes stability index, we quantified the dynamic and thermodynamic airsea feedbacks in the PI and MH simulations. The quantitative analyses showed that the reduced ENSO variability in MH arose from the weakening in the thermocline (TH), zonal-advection (ZA) and Ekman (EK) feedback terms. We found that all the weakened TH, ZA, and EK terms are associated with the reduction in the response of anomalous thermocline depth (Dʹ) to the zonal wind stress anomaly (′ x) in MH compared to PI. The reduced Dʹ response is attributed to the flattened meridional structure of ENSO-related ′ x field in MH, which is linked to the enhanced surface poleward mean meridional current in MH. Among many aspects of the mean state changes under the MH orbital forcing, this study identified that the surface mean meridional current change might be a key factor behind the suppressed ENSO variability in MH. Lastly, through comparing our findings with the ENSO future projection studies, we found that the wind-thermocline feedback is susceptible in a changing climate, which implies that minimizing the uncertainty in the wind-thermocline feedback change may help constrain future ENSO response. Keywords ENSO amplitude change in mid-Holocene • BJ index • Air-sea feedback • Ocean dynamical processes • Meridional structure change Electronic supplementary material The online version of this article (

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Uncertainty of ENSO-amplitude projections in CMIP5 and CMIP6 models

et al. 2021

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There is a long-standing debate on how the El Niño/Southern Oscillation (ENSO) amplitude may change during the twenty-first century in response to global warming. Here we identify the sources of uncertainty in the ENSO amplitude projections in models participating in the Coupled Model Intercomparison Phase 5 (CMIP5) and Phase 6 (CMIP6), and quantify scenario uncertainty, model uncertainty and uncertainty due to internal variability. The model projections exhibit a large spread, ranging from increasing standard deviation of up to 0.6 °C to diminishing standard deviation of up to − 0.4 °C by the end of the twenty-first century. The ensemble-mean ENSO amplitude change is close to zero. Internal variability is the main contributor to the uncertainty during the first three decades; model uncertainty dominates thereafter, while scenario uncertainty is relatively small throughout the twenty-first century. The total uncertainty increases from CMIP5 to CMIP6: while model uncertainty is reduced, scenario uncertainty is considerably increased. The models with “realistic” ENSO dynamics have been analyzed separately and categorized into models with too small, moderate and too large ENSO amplitude in comparison to instrumental observations. The smallest uncertainties are observed in the sub-ensemble exhibiting realistic ENSO dynamics and moderate ENSO amplitude. However, the global warming signal in ENSO-amplitude change is undetectable in all sub-ensembles. The zonal wind-SST feedback is identified as an important factor determining ENSO amplitude change: global warming signal in ENSO amplitude and zonal wind-SST feedback strength are highly correlated across the CMIP5 and CMIP6 models.

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Changes in ENSO amplitude under climate warming and cooling

Cited by 25 publications

References 43 publications

Drivers of reduced ENSO variability in mid-Holocene in a coupled model

Drivers of reduced ENSO variability in mid-Holocene in a coupled model

Towards understanding the suppressed ENSO activity during mid-Holocene in PMIP2 and PMIP3 simulations

Uncertainty of ENSO-amplitude projections in CMIP5 and CMIP6 models

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