Vertical structure variability in the equatorial Pacific before and after the Pacific climate shift of the 1970s

Moon, Byung-Kwon

doi:10.1029/2003gl018829

Cited by 30 publications

(34 citation statements)

References 16 publications

(23 reference statements)

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“…Alterations of the intensity, frequency and type of the ENSO have also been observed in recent decades Yu 2009, Lee andMcPhaden 2010). This shift could be associated with changes in the Atlantic (Dong et al 2006) and/or Pacific background state (Moon et al 2004), since an alteration of the mean sea surface temperature (SST), thermocline depth (z20) and zonal wind can modify the ENSO characteristics (Federov and Philander 2000). In addition, a "feedback-like mechanism" between the mean state and the interannual events has been documented, so warm (cold) ENSO events seem to increase (decrease) the SST of the equatorial region, changing, in turn, the background state (Kug et al 2009, Lee andMcPhaden 2010).…”

Section: Introductionmentioning

confidence: 90%

Changes in the interannual variability of the tropical Pacific as a response to an equatorial Atlantic forcing

Martín‐Rey¹,

Polo²,

Rodríguez‐Fonseca³

et al. 2012

Sci. Mar.

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SUMMARY: Previous studies have reported that the tropical Atlantic has had an influence on tropical Pacific interannual variability since the 1970s. This variability is studied in the present work, using simulations from a coupled model in the Indo-Pacific but with observed sea surface temperature (SST) prescribed over the Atlantic. The interannual variability is compared with that from a control simulation in which climatological SSTs are prescribed over the Atlantic. Differences in the Pacific mean state and in its variability are found in the forced simulation as a response to a warming in the equatorial Atlantic, characterized by a cooler background state and an increase in the variability over the tropical Pacific. A striking result is that the principal modes of tropical Pacific SST interannual variability show significant differences before and after the 1970s, providing new evidence of the Atlantic influence on the Pacific Ocean. Significant cooling (warming) in the equatorial Atlantic could have caused anomalous winds in the central-easter Pacific during the summer since 1970s. The thermocline depth also seems to be altered, triggering the dynamical processes involved in the development of El Niño (La Niña) phenomenon in the following winter. An increase in frequency of Niño and Niña events favouring the Central Pacific (CP) ones is observed in the last three decades. Further analyses using coupled models are still necessary to help us to understand the causes of this inter-basin connection.Keywords: Tropical Atlantic variability, Atlantic-Pacific connection, ENSO.RESUMEN: Cambios en la variabilidad interanual del PaCífiCo troPiCal Como resPuesta a un forzamiento del atlántiCo eCuatorial. -Trabajos previos han puesto de manifiesto como el Atlántico Tropical influye en la variabilidad interanual del Pacífico a partir de los años 70. El presente trabajo estudia la variabilidad del Pacífico Tropical a partir de simulaciones realizadas con un modelo acoplado en el Indo-Pacífico que considera la Temperatura de la Superficie del Mar (TSM) observada en el Atlántico como forzamiento externo. Los resultados de esta simulación son comparados con los obtenidos en una simulación de control, con TSM climatológicas en el Atlántico. La simulación forzada muestra cambios en el estado base y la variabilidad del Océano Pacífico relacionados con un calentamiento en el Atlántico ecuatorial, destacando un aumento de la variabilidad y un enfriamiento del Pacífico ecuatorial. Además, los principales modos de variabilidad del Pacífico antes y después de los 70 son diferentes, reafirmándose la influencia del Atlántico sobre el Océano Pacífico. Un enfriamiento (calentamiento) en el Atlántico ecuatorial podría generar vientos anómalos en el centro-este de la cuenca del Pacífico durante el verano desde dicha década. La profundidad de la termoclina también se modificaría, desencadenándose los procesos dinámicos involucrados en el desarrollo de El Niño (La Niña) en el invierno siguiente. Los resultados muestran un aumento de la frec...

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Section: Introductionmentioning

confidence: 90%

Changes in the interannual variability of the tropical Pacific as a response to an equatorial Atlantic forcing

Martín‐Rey¹,

Polo²,

Rodríguez‐Fonseca³

et al. 2012

Sci. Mar.

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“…Such changes are likely to be associated with distinct impacts on ENSO dynamics and are consistent with the changes in ENSO statistics. In particular, a decrease in mean zonal SST gradients as observed for the 1976-shifts is concurrent with a flattening mean thermocline (Moon et al, 2004), which impacts ENSO towards larger amplitude modulation (Dewitte et al, 2007a). This also favours the amplification of ENSO nonlinearity (Timmerman and Jin, 2002) and thereby is likely to modify the statistical characteristics considered in this study.…”

Section: Observations: K98 Datamentioning

confidence: 98%

“…Although our knowledge of the phenomenon has increased considerably in the last two decades, ENSO remains difficult to predict and its characteristics change in ways that are not yet understood by the scientific community. In particular, ENSO's characteristics (frequency, amplitude, propagating features and predictability) vary with changes in the mean state of the tropical Pacific (Fedorov and Philander 2000;Moon et al, 2004;An, 2004). The difficulty in predicting ENSO and its evolution lies partly in the limited ability of Gaussian statistics to account for Extreme Events (EEs).…”

Section: Introductionmentioning

confidence: 99%

ENSO's non-stationary and non-Gaussian character: the role of climate shifts

Boucharel

Dewitte

Garel

et al. 2009

Nonlin. Processes Geophys.

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Abstract. El Niño Southern Oscillation (ENSO) is the dominant mode of climate variability in the Pacific, having socio-economic impacts on surrounding regions. ENSO exhibits significant modulation on decadal to inter-decadal time scales which is related to changes in its characteristics (onset, amplitude, frequency, propagation, and predictability). Some of these characteristics tend to be overlooked in ENSO studies, such as its asymmetry (the number and amplitude of warm and cold events are not equal) and the deviation of its statistics from those of the Gaussian distribution. These properties could be related to the ability of the current generation of coupled models to predict ENSO and its modulation.Here, ENSO's non-Gaussian nature and asymmetry are diagnosed from in situ data and a variety of models (from intermediate complexity models to full-physics coupled general circulation models (CGCMs)) using robust statistical tools initially designed for financial mathematics studies. In particular α-stable laws are used as theoretical background material to measure (and quantify) the non-Gaussian character of ENSO time series and to estimate the skill of "naïve" statistical models in producing deviation from Gaussian laws and asymmetry. The former are based on non-stationary processes dominated by abrupt changes in mean state and empirical variance. It is shown that the α-stable character of ENSO may result from the presence of climate shifts in the time series. Also, cool (warm) periods are associated with ENSO statistics having a stronger (weaker) tendency towards Gaussianity and lower (greater) asymmetry. This supports the hypothesis of ENSO being rectified by changes in mean state through nonlinear processes. The relationship betweenCorrespondence to: J. Boucharel (julien.boucharel@legos.obs-mip.fr) changes in mean state and nonlinearity (skewness) is further investigated both in the Zebiak and Cane (1987)'s model and the models of the Intergovernmental Panel for Climate Change (IPCC). Whereas there is a clear relationship in all models between ENSO asymmetry (as measured by skewness or nonlinear advection) and changes in mean state, they exhibit a variety of behaviour with regard to α-stability. This suggests that the dynamics associated with climate shifts and the occurrence of extreme events involve higher-order statistical moments that cannot be accounted for solely by nonlinear advection.

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“…Caution is thus needed here for interpreting the modeled ENSO time scales in case of small differences with SODA (approximately 0.3-0.4 yr). Note that GODAS, which considers the period after the 1976 climate shift known to be characterized with lower ENSO frequency (Moon et al 2004), exhibits a longer time scale.…”

Section: ) Diagnosing the Enso Modementioning

confidence: 99%

ENSO Feedbacks and Associated Time Scales of Variability in a Multimodel Ensemble

Belmadani

Dewitte

2010

Journal of Climate

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The background state of the equatorial Pacific determines the prevalence of a ''slow'' recharge oscillatortype ENSO over a ''fast'' quasi-biennial surface-driven ENSO. The first is controlled to a large extent by the thermocline feedback, whereas the latter is related to enhanced zonal advective feedback. In this study, dynamical diagnostics are used to investigate the relative importance of these two feedbacks in the Coupled Model Intercomparison Project and its relation with the differences in ENSO-like variability among the models. The focus is on the role of the mean oceanic surface circulation in controlling the relative weight of the two feedbacks.By the means of an intermediate-type ocean model of the tropical Pacific ''tuned'' from the coupled general circulation model (CGCM) outputs, the contribution of the advection terms (vertical versus zonal) to the rate of SST change is estimated. A new finding is that biases in the advection terms are to a large extent related to the biases in the mean surface circulation. The latter are used to infer the dominant ENSO feedback for each CGCM. This allows for the classification of the CGCMs into three groups that account for the dominant feedback process of the ENSO cycle: horizontal advection (mainly in the western Pacific), vertical advection (mainly in the eastern Pacific), and the combination of both mechanisms.Based on such classification, the analysis also reveals that the models exhibit distinctive behavior with respect to the characteristics of ENSO: for most models, an enhanced (diminished) contribution of the zonal advective feedback is associated with faster (slower) ENSO and a tendency toward a cooler (warmer) mean state in the western-to-central Pacific Ocean. The results support the interpretation that biases in the mean state are sustained/maintained by the privileged mode of variability associated with the dominant feedback mechanism in the models. In particular, the models having a dominant zonal advective feedback exhibit significant cold SST asymmetry (or negative skewness) in the western equatorial Pacific.

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Vertical structure variability in the equatorial Pacific before and after the Pacific climate shift of the 1970s

Cited by 30 publications

References 16 publications

Changes in the interannual variability of the tropical Pacific as a response to an equatorial Atlantic forcing

Changes in the interannual variability of the tropical Pacific as a response to an equatorial Atlantic forcing

ENSO's non-stationary and non-Gaussian character: the role of climate shifts

ENSO Feedbacks and Associated Time Scales of Variability in a Multimodel Ensemble

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