Thermocline Fluctuations in the Equatorial Pacific Related to the Two Types of El Niño Events

Huang, Rui; Wang, Weiqiang; Zhu, Congwen; Lu, Riyu

doi:10.1175/jcli-d-16-0291.1

Cited by 24 publications

(14 citation statements)

References 49 publications

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“…Both El Niño types influence the global climate distinctly in terms of phase and/or magnitude of the impacts (Ashok et al, ; Cai & Cowan, ; Chen & Tam, ; Gierach et al, ; Kim et al, ; Pradhan et al, ; Preethi et al, ; Taschetto & England, ; Taschetto et al, ; Trenberth & Smith, ; Webster et al, ; Yeh et al, ). The results from a recent paper by Xu et al () underline the vital importance of equatorial Pacific thermocline variations in combination with air‐sea interactions, on the EM. While the distinction of the impacts of two types of ENSOs, particularly that of the warm‐phased events, has been well accepted, the issue of complete distinction between the types has been under discussion.…”

Section: Introductionmentioning

confidence: 91%

Nonlinearities in the Evolutional Distinctions Between El Niño and La Niña Types

et al. 2017

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Using the HadISST, SODA reanalysis, and various other observed and reanalyzed data sets for the period 1950–2010, we explore nonlinearities in the subsurface evolutional distinctions between El Niño types and La Niña types from a few seasons before the onset. Cluster analysis carried out over both summer and winter suggests that while the warm‐phased events of both types are distinguishable, several cold phased events are clustered together. Further, we apply a joint Self‐Organizing Map (SOM) analysis using the monthly sea surface temperature anomaly (SSTA) and thermocline‐depth anomalies in tropical Pacific (TP). Results reveal that the evolutionary paths of El Niño Modoki (EM) and El Niño (EL) are, broadly, different. Subsurface temperature composites of EL and EM show different onset characteristics. During an EL, warm anomaly in the west spreads eastward along the thermocline and reaches the surface in the east in March–May of year(0). During an EM, warm anomaly already exists in the central tropical Pacific and then reaches the surface in the east in September–November of year(0). Composited SSTAs during La Niña (LN) and La Niña Modoki (LM) are distinguishable only at 80% confidence level, but the composited subsurface temperature anomalies show differences in the location of the coldest anomaly as well as evolution at 90% confidence level. Thus, the El Niño flavor distinction is potentially predictable at longer leads.

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Section: Introductionmentioning

confidence: 91%

Nonlinearities in the Evolutional Distinctions Between El Niño and La Niña Types

et al. 2017

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“…Through the wind‐evaporation‐SST (WES) feedback (Xie and Philander, 1994), the anomalous southwesterly wind could weaken the climatological surface trade winds and reduce surface evaporation, and then maintain and enhance the positive PMM anomalies. The sustained warming SSTA in the subtropical northeastern Pacific thus may extend southwestward to the equatorial central Pacific and deepen the thermocline, and ultimately trigger an El Niño in the central Pacific (Yeh et al, ; Xu et al, ; Yu and Fang, ). These anomalies thus caused the westward extension of the negative SLPA over the tropics and reduced the responses of the equatorial low‐level zonal wind to the zonal SSTA gradient, and finally weakened the El Niño magnitude.…”

Section: Impacts Of the North Pacific Climate Variabilitymentioning

confidence: 99%

Weakening of the El Niño amplitude since the late 1990s and its link to decadal change in the North Pacific climate

Wang

Liu

Zhu

2019

Intl Journal of Climatology

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The amplitude of El Niño, measured by the Nino3.4 sea surface temperature anomaly (SSTA) index, has exhibited an interdecadal change with a weakening trend since the late 1990s, characterized by the distinct Bjerknes stability index between 1980-1998 and 1999-2014. Statistical results suggest that this was primarily induced by the attenuation of the zonal wind stress and low-level wind anomalies in response to the zonal equatorial SSTA gradient. The weakened atmospheric responses to the zonal equatorial SSTA gradient were associated with the obvious westward extension of the negative sea level pressure anomalies (SLPA) over the tropics. This was mainly attributed to the transition of the dominant atmospheric circulation over the North Pacific, where the Aleutian Low (AL) mode was replaced by the North Pacific Oscillation (NPO) mode after the late 1990s. Numerical experiments from the long-term historical simulations of the GFDL-CM3 model indicate that both of the AL and NPO were dominant over the North Pacific and alternated on the interdecadal time-scale. When the NPO mode was dominant, it became more effective at playing a role in triggering an El Niño in the central Pacific via the seasonal footprinting mechanism over the subtropical northeastern Pacific. Such a change might cause the westward shift of the tropical SLPA and the attenuated atmospheric responses to the zonal SSTA gradient, ultimately resulting in the weakening of the El Niño amplitude.

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“…Paleoceanographic records from the equatorial Pacific Ocean provide insight into ENSO behavior when global boundary conditions-ocean and atmosphere circulations, sea level and ice volume, atmospheric greenhouse gas concentration, and albedo-were different from today, and thus help in the projection of trends or variance of ENSO in response to climate change. The ENSO cycle is known to be a feature of Earth's climate in the geological past (4,5), and its signal should be more prominent in the thermocline response, as in modern climate (6). However, a lack of tropical thermocline water temperature (TWT) records with high temporal resolution has limited our understanding of how ENSO responds to orbital changes (7,8).…”

mentioning

confidence: 99%

Half-precessional cycle of thermocline temperature in the western equatorial Pacific and its bihemispheric dynamics

Jian

Wang

Dang

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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The El Niño−Southern Oscillation (ENSO), which is tightly coupled to the equatorial thermocline in the Pacific, is the dominant source of interannual climate variability, but its long-term evolution in response to climate change remains highly uncertain. This study uses Mg/Ca in planktonic foraminiferal shells to reconstruct sea surface and thermocline water temperatures (SST and TWT) for the past 142 ky in a western equatorial Pacific (WEP) core MD01-2386. Unlike the dominant 100-ky glacial−interglacial cycle recorded by SST and δ18O, which echoes the pattern seen in other WEP sites, the upper ocean thermal gradient shows a clear half-precessional (9.4 ky or 12.7 ky) cycle as indicated by the reconstructed and simulated temperature (ΔT) and δ18O differences between the surface and thermocline waters. This phenomenon is attributed to the interplay of subtropical-to-tropical thermocline anomalies forced by the antiphased meridional insolation gradients in the two hemispheres at the precessional band. In particular, the TWT shows greater variability than SST, and dominates the ΔT changes which couple with the west−east SST difference in the equatorial Pacific at the half-precessional band, implying a decisive role of the tropical thermocline in orbital-scale climate change.

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Thermocline Fluctuations in the Equatorial Pacific Related to the Two Types of El Niño Events

Cited by 24 publications

References 49 publications

Nonlinearities in the Evolutional Distinctions Between El Niño and La Niña Types

Nonlinearities in the Evolutional Distinctions Between El Niño and La Niña Types

Weakening of the El Niño amplitude since the late 1990s and its link to decadal change in the North Pacific climate

Half-precessional cycle of thermocline temperature in the western equatorial Pacific and its bihemispheric dynamics

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