scholarly journals Do periodic consolidations of Pacific countercurrents trigger global cooling by equatorially symmetric La Niña?

2010 ◽  
Vol 6 (3) ◽  
pp. 905-961
Author(s):  
J. H. Duke
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Internal Tide ◽  
Hadley Cell ◽  
La Niña ◽  
Central Pacific ◽  
Enso Events ◽  
La Nina ◽  
Global Cooling

Abstract. A sporadic phenomenon of internal tide resonance (ITR) in the western equatorial Pacific thermocline is shown to precede 11 of 12 major upturns in the Niño 3.4 index between 1992 and 2008. Observed ITR has up to 9 °C semidiurnal temperature excursions indicating thermocline heave, but is invisible in time resolution longer than one day. It is independent of westerly wind bursts (WWB). A hypothesis is advanced that (1) ITR dissipates vorticity, leading to Pacific countercurrent consolidation (PCC) by reducing the vortex stretching term in Sverdrup balance. The consequence of lost vorticity survives ephemeral ITR events; (2) The specific surface area of countercurrents is reduced by PCC, which reduces frictional opposition to zonal gradient pressure, which triggers eastward advection at El Niño onset; (3) PCC also accelerates transfer of potential energy to the "pycnostad" below the Equatorial Undercurrent. This shoals the equatorial thermocline, leading to a distinct mode of equatorially symmetric La Niña (ESLN) characterized by a winter monsoon cell above a "cold eye" that is separated from the South American continent, as in 1998; (4) Precessional southward intertropical convergence zone migration (ITCZ) is an alternate PCC trigger, but its effect is modulated by obliquity; and (5) ESLN causes global cooling in all timescales by (a) reduced Hadley cell water vapor production when its rising branch is above the cold eye, (b) equatorward shift in southern circumpolar westerlies due to Hadley cell constriction, (c) possible CO2 sequestration by increased EUC iron fertilized export production on the equator, and (d) possible adjacent cloud seeding by biogenic dimethyl sulphide. Surprising coincidences of WWB with perigean eclipses suggest a parallel atmospheric tide influence. Proposed PCC-ESLN forcing operates in multiple timescales, beginning where the annual cycle of strong equinoctial tides coincides with the minimum perigee cycle. This forcing corresponds with El Niño Southern Oscillation (ENSO) events in 1997, 2002, and 2006. Next, extreme central eclipses that perturb perigee-sysygy intervals also correspond with extreme ENSO events, notably in 1877, 1888, and 1982, and a 586 year cycle in the frequency of these eclipses corresponds with known stadial events in the past 4 thousand years. Contrast in the 586 year cycle increases with Earth eccentricity because it is the result of shorter synodic months at aphelion. Longer timescale forcing is by orbital control of the east-central Pacific ITCZ position, yielding a 10 thousand year fast ice sheet melt interval between March and September perihelion. But default ESLN is only interrupted when perihelion in March coincides with rising obliquity. A change in the phase relation between obliquity and precession from 1:2 to 3:5 or 2:5 may therefore explain skipped obliquity cycles after the mid-Pleistocene transition. A secular improvement in eclipse commensurability that parallels Cenozoic cooling is noted.

scholarly journals Response of CO<sub>2</sub> and H<sub>2</sub>O fluxes of a mountainous tropical rain forest in equatorial Indonesia to El Niño events

2015 ◽  
Vol 12 (6) ◽  
pp. 4405-4431 ◽  
Author(s):  
A. Olchev ◽  
A. Ibrom ◽  
O. Panferov ◽  
D. Gushchina ◽  
P. Propastin ◽  
...  
Keyword(s):  
El Niño ◽  
Rain Forest ◽  
Tropical Rain Forest ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Moderate Intensity ◽  
Central Pacific ◽  
Enso Events ◽  
La Nina

Abstract. The possible impact of El Niño–Southern Oscillation (ENSO) events on the main components of CO2 and H2O fluxes in a pristine mountainous tropical rainforest growing in Central Sulawesi in Indonesia is described. The fluxes were continuously measured using the eddy covariance method for the period from January 2004 to June 2008. During this period, two episodes of El Niño and one episode of La Niña were observed. All these ENSO episodes had moderate intensity and were of Central Pacific type. The temporal variability analysis of the main meteorological parameters and components of CO2 and H2O exchange showed a very high sensitivity of Evapotranspiration (ET) and Gross Primary Production (GPP) of the tropical rain forest to meteorological variations caused by both El Niño and La Niña episodes. Incoming solar radiation is the main governing factor that is responsible for ET and GPP variability. Ecosystem Respiration (RE) dynamics depend mainly on the air temperature changes and are almost insensitive to ENSO. Changes of precipitation due to moderate ENSO events did not cause any notable effect on ET and GPP, mainly because of sufficient soil moisture conditions even in periods of anomalous reduction of precipitation in the region.

scholarly journals Response of CO<sub>2</sub> and H<sub>2</sub>O fluxes in a mountainous tropical rainforest in equatorial Indonesia to El Niño events

2015 ◽  
Vol 12 (22) ◽  
pp. 6655-6667 ◽  
Author(s):  
A. Olchev ◽  
A. Ibrom ◽  
O. Panferov ◽  
D. Gushchina ◽  
H. Kreilein ◽  
...  
Keyword(s):  
El Niño ◽  
Tropical Rainforest ◽  
El Nino ◽  
Southern Oscillation ◽  
Ecosystem Respiration ◽  
La Niña ◽  
Moderate Intensity ◽  
Central Pacific ◽  
Enso Events ◽  
La Nina

Abstract. The possible impact of El Niño–Southern Oscillation (ENSO) events on the main components of CO2 and H2O fluxes between the tropical rainforest and the atmosphere is investigated. The fluxes were continuously measured in an old-growth mountainous tropical rainforest in Central Sulawesi in Indonesia using the eddy covariance method for the period from January 2004 to June 2008. During this period, two episodes of El Niño and one episode of La Niña were observed. All these ENSO episodes had moderate intensity and were of the central Pacific type. The temporal variability analysis of the main meteorological parameters and components of CO2 and H2O exchange showed a high sensitivity of evapotranspiration (ET) and gross primary production (GPP) of the tropical rainforest to meteorological variations caused by both El Niño and La Niña episodes. Incoming solar radiation is the main governing factor that is responsible for ET and GPP variability. Ecosystem respiration (RE) dynamics depend mainly on the air temperature changes and are almost insensitive to ENSO. Changes in precipitation due to moderate ENSO events did not have any notable effect on ET and GPP, mainly because of sufficient soil moisture conditions even in periods of an anomalous reduction in precipitation in the region.

scholarly journals The ENSO–Asian Monsoon Interaction in a Coupled Ocean–Atmosphere GCM

2007 ◽  
Vol 20 (20) ◽  
pp. 5164-5177 ◽  
Author(s):  
Ying Li ◽  
Riyu Lu ◽  
Buwen Dong
Keyword(s):  
El Niño ◽  
Asian Monsoon ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Enso Cycle ◽  
Central Pacific ◽  
La Nina ◽  
Ocean Atmosphere ◽  
The Relationship

Abstract In this study, the authors evaluate the (El Niño–Southern Oscillation) ENSO–Asian monsoon interaction in a version of the Hadley Centre coupled ocean–atmosphere general circulation model (CGCM) known as HadCM3. The main focus is on two evolving anomalous anticyclones: one located over the south Indian Ocean (SIO) and the other over the western North Pacific (WNP). These two anomalous anticyclones are closely related to the developing and decaying phases of the ENSO and play a crucial role in linking the Asian monsoon to ENSO. It is found that the HadCM3 can well simulate the main features of the evolution of both anomalous anticyclones and the related SST dipoles, in association with the different phases of the ENSO cycle. By using the simulated results, the authors examine the relationship between the WNP/SIO anomalous anticyclones and the ENSO cycle, in particular the biennial component of the relationship. It is found that a strong El Niño event tends to be followed by a more rapid decay and is much more likely to become a La Niña event in the subsequent winter. The twin anomalous anticyclones in the western Pacific in the summer of a decaying El Niño are crucial for the transition from an El Niño into a La Niña. The El Niño (La Niña) events, especially the strong ones, strengthen significantly the correspondence between the SIO anticyclonic (cyclonic) anomaly in the preceding autumn and WNP anticyclonic (cyclonic) anomaly in the subsequent spring, and favor the persistence of the WNP anomaly from spring to summer. The present results suggest that both El Niño (La Niña) and the SIO/WNP anticyclonic (cyclonic) anomalies are closely tied with the tropospheric biennial oscillation (TBO). In addition, variability in the East Asian summer monsoon, which is dominated by the internal atmospheric variability, seems to be responsible for the appearance of the WNP anticyclonic anomaly through an upper-tropospheric meridional teleconnection pattern over the western and central Pacific.

Composite Analysis of the Effects of ENSO Events on Antarctica

2016 ◽  
Vol 29 (5) ◽  
pp. 1797-1808 ◽  
Author(s):  
Lee J. Welhouse ◽  
Matthew A. Lazzara ◽  
Linda M. Keller ◽  
Gregory J. Tripoli ◽  
Matthew H. Hitchman
Keyword(s):  
El Niño ◽  
Geopotential Height ◽  
El Nino ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
La Niña ◽  
Austral Spring ◽  
Enso Events ◽  
La Nina ◽  
The Relationship

Abstract Previous investigations of the relationship between El Niño–Southern Oscillation (ENSO) and the Antarctic climate have focused on regions that are impacted by both El Niño and La Niña, which favors analysis over the Amundsen and Bellingshausen Seas (ABS). Here, 35 yr (1979–2013) of European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) data are analyzed to investigate the relationship between ENSO and Antarctica for each season using a compositing method that includes nine El Niño and nine La Niña periods. Composites of 2-m temperature (T2m), sea level pressure (SLP), 500-hPa geopotential height, sea surface temperatures (SST), and 300-hPa geopotential height anomalies were calculated separately for El Niño minus neutral and La Niña minus neutral conditions, to provide an analysis of features associated with each phase of ENSO. These anomaly patterns can differ in important ways from El Niño minus La Niña composites, which may be expected from the geographical shift in tropical deep convection and associated pattern of planetary wave propagation into the Southern Hemisphere. The primary new result is the robust signal, during La Niña, of cooling over East Antarctica. This cooling is found from December to August. The link between the southern annular mode (SAM) and this cooling is explored. Both El Niño and La Niña experience the weakest signal during austral autumn. The peak signal for La Niña occurs during austral summer, while El Niño is found to peak during austral spring.

scholarly journals Reversed Spatial Asymmetries between El Niño and La Niña and Their Linkage to Decadal ENSO Modulation in CMIP3 Models

2011 ◽  
Vol 24 (20) ◽  
pp. 5423-5434 ◽  
Author(s):  
Jin-Yi Yu ◽  
Seon Tae Kim
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Interaction Mechanism ◽  
Tropical Pacific ◽  
La Niña ◽  
Enso Events ◽  
La Nina ◽  
Spatial Asymmetries ◽  
Mean State

Abstract This study examines preindustrial simulations from Coupled Model Intercomparison Project, phase 3 (CMIP3), models to show that a tendency exists for El Niño sea surface temperature anomalies to be located farther eastward than La Niña anomalies during strong El Niño–Southern Oscillation (ENSO) events but farther westward than La Niña anomalies during weak ENSO events. Such reversed spatial asymmetries are shown to force a slow change in the tropical Pacific Ocean mean state that in return modulates ENSO amplitude. CMIP3 models that produce strong reversed asymmetries experience cyclic modulations of ENSO intensity, in which strong and weak events occur during opposite phases of a decadal variability mode associated with the residual effects of the reversed asymmetries. It is concluded that the reversed spatial asymmetries enable an ENSO–tropical Pacific mean state interaction mechanism that gives rise to a decadal modulation of ENSO intensity and that at least three CMIP3 models realistically simulate this interaction mechanism.

scholarly journals PDO–ENSO Effects in the Climate of Mexico

2006 ◽  
Vol 19 (24) ◽  
pp. 6433-6438 ◽  
Author(s):  
Edgar G. Pavia ◽  
Federico Graef ◽  
Jorge Reyes
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Climate Anomalies ◽  
Enso Events ◽  
La Nina ◽  
Mean Temperature ◽  
The Pacific

Abstract The role of the Pacific decadal oscillation (PDO) in El Niño–Southern Oscillation (ENSO)-related Mexican climate anomalies during winter and summer is investigated. The precipitation and mean temperature data of approximately 1000 stations throughout Mexico are considered. After sorting ENSO events by warm phase (El Niño) and cold phase (La Niña) and prevailing PDO phase: warm or high (HiPDO) and cold or low (LoPDO), the authors found the following: 1) For precipitation, El Niño favors wet conditions during summers of LoPDO and during winters of HiPDO. 2) For mean temperature, cooler conditions are favored during La Niña summers and during El Niño winters, regardless of the PDO phase; however, warmer conditions are favored by the HiPDO during El Niño summers.

scholarly journals Differential Imprints of Distinct ENSO Flavors in Global Patterns of Very Low and High Seasonal Precipitation

2021 ◽  
Vol 3 ◽  
Author(s):  
Marc Wiedermann ◽  
Jonatan F. Siegmund ◽  
Jonathan F. Donges ◽  
Reik V. Donner
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Spatial Scales ◽  
La Niña ◽  
Seasonal Precipitation ◽  
Central Pacific ◽  
Regional Patterns ◽  
La Nina ◽  
Very High

The effects of El Niño's two distinct flavors, East Pacific (EP) and Central Pacific (CP)/Modoki El Niño, on global climate variability have been studied intensively in recent years. Most of these studies have made use of linear multivariate statistics or composite analysis. Especially the former assumes the same type of linear statistical dependency to apply across different phases of the El Niño–Southern Oscillation (ENSO), which appears not necessarily a justified assumption. Here, we statistically evaluate the likelihood of co-occurrences between very high or very low seasonal precipitation sums over vast parts of the global land surface and the presence of the respective EP and CP types of both, El Niño and La Niña. By employing event coincidence analysis, we uncover differential imprints of both flavors on very low and very high seasonal precipitation patterns over distinct regions across the globe, which may severely affect, among others, agricultural and biomass production or public health. We particularly find that EP periods exhibit statistically significant event coincidence rates with hydrometeorological anomalies at larger spatial scales, whereas sparser patterns emerge along with CP periods. Our statistical analysis confirms previously reported interrelations for EP periods and uncovers additional distinct regional patterns of very high/low seasonal precipitation, such as increased rainfall over Central Asia alongside CP periods that have to our knowledge not been reported so far. Our results demonstrate that a thorough distinction of El Niño and La Niña into their two respective flavors could be crucial for understanding the emergence of strong regional hydrometeorological anomalies and anticipating their associated ecological and socioeconomic impacts.

ENSO continuum and its impacts on worldwide precipitation: Observation vs. CMIP5/6

2020 ◽  
Author(s):  
Bastien Dieppois ◽  
Jonathan Eden ◽  
Paul-Arthur Monerie ◽  
Benjamin Pohl ◽  
Julien Crétat ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Boreal Summer ◽  
Central Pacific ◽  
Rainfall Gradient ◽  
Data Set ◽  
Enso Events ◽  
La Nina ◽  
Central Pacific Enso

&lt;p&gt;It is now widely recognized that El Nino-Southern Oscillation (ENSO) occurs in more than one form, e.g. eastern and central Pacific ENSO. Given that these various ENSO flavours may contribute to climate variability and trends in different ways, this study presents a framework that treats ENSO as a continuum to examine its impact on precipitation, and to evaluate the performance of the last two generations of global climate models (GCMs): CMIP5 and CMIP6.&lt;/p&gt;&lt;p&gt;Uncertainties in the location and intensity of observed El Nino and La Nina events are assessed in various observational and satellite-derived products (ERSSTv5, COBESSTv2, HadSST1 and OISSTv2). The probability distributions of El Nino and La Nina event locations, and intensities, slightly differ from one observational data set to another. For instance, La Nina events are more intense and more likely to occur in the central Pacific using COBESSTv2. All these products also depict consistent decadal variations in the location and intensity of ENSO events: i) central Pacific ENSO events were more likely in the 1940/50s and from the 1980s; ii) eastern Pacific ENSO events were more likely in the 1910/20s and 1960/70s; iii) La Nina events have become more intense during the 20&lt;sup&gt;th&lt;/sup&gt; and early 21&lt;sup&gt;st &lt;/sup&gt;centuries.&lt;/p&gt;&lt;p&gt;These fluctuations in ENSO location and intensity are found to impact precipitation consistently across diverse global precipitation products (CRUv4.03, GPCCv8 and UDELv5.01). Over southern Africa, for instance, more intense eastern (central) Pacific El Nino events are found to favour drought conditions over northern (southern) regions during austral summer. By contrast, over the same regions, more intense La Nina events favours wet conditions, while the location of these events has little effect on precipitation. Over West Africa, ENSO locations favour a zonal (E-W) rainfall gradient in precipitation during boreal summer, while changes in ENSO intensity modulate the strength of the meridional (N-S) rainfall gradient.&lt;/p&gt;&lt;p&gt;Using both historical and pi-Control runs, we demonstrate that most CMIP5 and CMIP6 models favour either eastern or central Pacific ENSO events, but very few models are able to capture the full observed ENSO continuum. Regarding ENSO impacts on worldwide precipitation, contrasted results appear in most models.&lt;/p&gt;

scholarly journals Peruvian Fur Seals as Archivists of El Niño Southern Oscillation Effects

2021 ◽  
Vol 8 ◽  
Author(s):  
Mickie R. Edwards ◽  
Susana Cárdenas-Alayza ◽  
Michael J. Adkesson ◽  
Mya Daniels-Abdulahad ◽  
Amy C. Hirons
Keyword(s):  
Food Web ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Enso Events ◽  
La Nina ◽  
Fur Seal

Peru’s coastal waters are characterized by significant environmental fluctuation due to periodic El Niño- La Niña- Southern Oscillation (ENSO) events. This variability results in ecosystem-wide food web changes which are reflected in the tissues of the Peruvian fur seal (Arctocephalus australis). Stable isotope ratios (δ13C and δ15N) in Peruvian fur seal vibrissae (whiskers) are used to infer temporal primary production and dietary variations in individuals. Sea surface temperature anomaly (SSTA) recordings from the Niño 1+2 Index region captured corresponding ENSO conditions. Fluctuations in δ15N values were correlated to SSTA records, indicating that ENSO conditions likely impact the diet of these apex predators over time. Anomalous warm phase temperatures corresponded to decreased δ15N values, whereas cold phase anomalous conditions corresponded to increased δ15N values, potentially from upwelled, nutrient-rich water. Vibrissae δ13C values revealed general stability from 2004 to 2012, a moderate decline during 2013 (La Niña conditions) followed by a period of increased values concurrent with the 2014–2016 El Niño event. Both δ13C and δ15N values were inversely correlated to each other during the strongest El Niño Southern Oscillation event on record (2014–2016), possibly indicating a decline in production leading to an increase in food web complexity. Lower δ13C and δ15N values were exhibited in female compared to male fur seal vibrissae. Findings suggest ENSO conditions influence resource availability, possibly eliciting changes in pinniped foraging behavior as well as food web of the endangered Peruvian fur seal.

scholarly journals The ENSO-Related West Pacific Sea Surface Temperature Gradient

2013 ◽  
Vol 26 (23) ◽  
pp. 9545-9562 ◽  
Author(s):  
Andrew Hoell ◽  
Chris Funk
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Central Pacific ◽  
The West ◽  
West Pacific ◽  
Enso Events ◽  
West Pacific Ocean ◽  
La Nina

El Niño–Southern Oscillation (ENSO) events are accompanied by an anomalous zonal sea surface temperature (SST) gradient over the west Pacific Ocean, defined here as the west Pacific SST gradient (WPG). The WPG is defined as the standardized difference between area-averaged SST over the central Pacific Ocean (Niño-4 region) and west Pacific Ocean (0°–10°N, 130°–150°E). While the direction of the WPG follows ENSO cycles, the magnitude of the gradient varies considerably between individual El Niño and La Niña events. In this study, El Niño and La Niña events are grouped according to the magnitude of the WPG, and tropical SST, circulations, and precipitation are examined for the period 1948–2011. Until the 1980s the WPG showed little trend as the west and central Pacific warmed at similar rates; however, the west Pacific has recently warmed faster than the central Pacific, which has resulted in an increased WPG during La Niña events. The temporal evolution and distribution of tropical Pacific SST as well as the near-surface tropical Pacific zonal wind, divergence, and vertical velocity are considerably different during ENSO events partitioned according to the strength of the WPG. Modifications to the tropical circulation, resulting in changes to Indo– west Pacific precipitation, are linked to strong and consistent circulation and precipitation modifications throughout the Northern Hemisphere during winter.

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