El Nino-Southern Oscillation Variability Research Articles

Are trends in Olive Ridley sea turtle (Lepidochelys olivacea) nesting abundance affected by El Niño Southern Oscillation (ENSO) variability? Sixteen years of monitoring on the Pacific coast of northern Central America

Long-term monitoring is essential for the identification of population trends, and to understand how these trends are affected by climate variability. The El Niño Southern Oscillation (ENSO) is the strongest global interannual pattern of climate variability, resulting in the disruption of the annual phenological cycles of sea turtles. Among sea turtles, the Olive Ridley (Lepidochelys olivacea) is the most abundant, and on many beaches their nests are relocated to hatcheries as part of conservation management, especially in northern Central America. However, Olive Ridley nesting abundance trends in northern Central America and the effects of ENSO variability on these trends are still not fully understood. Here, we present the first long-term study of this subject. We predicted an upward trend in Olive Ridley nesting abundance on the Pacific coast of Guatemala, and a negative effect of increasing ENSO variability on nesting abundance. As proxies for nesting abundance, we analysed two different data sets; a 16-year period of Olive Ridley nesting data, using nesting tracks from one index beach (Hawaii in Guatemala), and the yearly number of eggs buried in the 25–35 hatcheries that operate along the Pacific coast of Guatemala. Revised Multivariate ENSO Index values were applied to estimate annual ENSO variability. During this 16-year study period, ENSO variability was distributed in eight neutral years, two normal El Niño years, four normal La Niña years and two extreme ENSO events; an extreme La Niña in 2010 and an extreme El Niño in 2015. We found a clear overall upward trend in Olive Ridley numbers of nesting tracks and eggs buried in hatcheries but no clear effect of ENSO variability on these nesting abundance proxies. However, a decrease in the net change of eggs buried in hatcheries occurred the respective years after the two extreme ENSO events during the study period. In the second year after those events, the net change of eggs buried in hatcheries bounced back to resume the overall positive trend. Our results suggest a clear upward trend, resilient to ENSO variability, of the nesting abundance of the Pacific coast Olive Ridley population in Guatemala. Community-based hatchery management efforts seem to be effective for Olive Ridley conservation on the Pacific coast of Guatemala. However, longer term monitoring including additional nesting beaches in northern Central America are necessary to further elucidate the effects of ENSO variability on the nesting abundance of Olive Ridley.

Spatio-temporal variability of temperature and chlorophyll-a concentration of sea surface in Bali Strait, Indonesia

Abstract. Wijaya A, Zakiyah U, Sambah AB, Setyohadi D. 2020. Spatio-temporal variability of temperature and chlorophyll-a concentration of sea surface in Bali Strait, Indonesia. Biodiversitas 21: 5283-5290. The Bali Strait is influenced by seasonal and inter-annual systems. El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are climate variabilities that affect water conditions. The knowledge about influence of ENSO and IOD variations on the fertility of waters in the Bali Strait is still lacking. The purpose of this study was to determine the effect of seasonal and inter-annual variability on the variability of Sea Surface Temperature (SST) and Sea Surface Chlorophyll-a (SSC) in the Bali Strait. This study applied SST and SSC data collected from the Aqua/Terra MODIS satellite, as well as the ENSO and IOD indices during March 2000-December 2019. The results described that the effect of ENSO on SST and SSC was low and IOD on SST and SSC was quite high. The effect was quite high between IOD and SST anomaly of-0.401. Seasonal variations indicate the abundance of high SSC and low SST in the southeast monsoon (JJA) which characterizes upwelling. Meanwhile, in the northwest monsoon (DJF), SSC was low and SST was high which characterizes downwelling. This condition cannot separate from the monsoonal process that occurred in the Bali Strait. The inter-annual variation showed that in the strong El Nino period and IOD (+) triggers a negative SST anomaly and a positive SSC results in strong upwelling, while in the strong La Nina period and strong IOD (-) triggers a positive SST anomaly and a negative SSC results in downwelling. The inter-annual variability of SSC influenced by IOD rather than ENSO. This condition indicates that the ENSO/IOD event changes the period of SSC concentration.

Coral-based proxy calibrations constrain ENSO-driven sea surface temperature and salinity gradients in the Western Pacific Warm Pool

Constraining past variability in ocean conditions in the Western Pacific Warm Pool (WPWP) and examining how it has been influenced by the El-Niño Southern Oscillation (ENSO) is critical to predicting how these systems may change in the future. To characterize the spatiotemporal variability of the WPWP and ENSO during the past three decades, we analyzed climate proxies using coral cores sampled from Porites spp. from Kosrae Island (KOS) and Woleai Atoll (WOL) in the Federated States of Micronesia. Coral skeleton samples drilled along the major growth axis were analyzed for oxygen isotopes (δ18Oc) and trace element ratios (Sr/Ca), used to reconstruct sea surface salinity and temperature (SSS and SST). Pseudocoral δ18O time series (δ18Opseudo) were calculated from gridded instrumental observations and compared to δ18Oc, followed by fine-tuning using coral Sr/Ca and gridded SST, to produce age models for each coral. The thermal component of δ18Oc was removed using Sr/Ca for SST, to derive δ18O of seawater (δ18Osw), a proxy for SSS. The Sr/Ca, and δ18Osw records were compared to instrumental SST and SSS to test their fidelity as regional climate recorders. We found both sites display significant Sr/Ca-SST calibrations at monthly and interannual (dry season, wet season, mean annual) timescales. At each site, δ18Osw also exhibited significant calibrations to SSS across the same timescales. The difference between normalized dry season SST (Sr/Ca) anomalies from KOS and WOL generates a zonal SST gradient (KOSWOLSST), capturing the east-west WPWP migration observed during ENSO events. Similarly, the average of normalized dry season δ18Osw anomalies from both sites produces an SSS index (KOSWOLSSS) reflecting the regional hydrological changes. Both proxy indices, KOSWOLSST and KOSWOLSSS, are significantly correlated to regional ENSO indices. These calibration results highlight the potential for extending the climate record, revealing spatial hydrological gradients within the WPWP and ENSO variability back to the end of the Little Ice Age.

Butterfly effect and a self-modulating El Niño response to global warming.

El Niño and La Niña, collectively referred to as the El Niño-Southern Oscillation (ENSO), are not only highly consequential1-6 but also strongly nonlinear7-14. For example, the maximum warm anomalies of El Niño, which occur in the equatorial eastern Pacific Ocean, are larger than the maximum cold anomalies of La Niña, which are centred in the equatorial central Pacific Ocean7-9. The associated atmospheric nonlinear thermal damping cools the equatorial Pacific during El Niño but warms it during La Niña15,16. Under greenhouse warming, climate models project an increase in the frequency of strong El Niño and La Niña events, but the change differs vastly across models17, which is partially attributed to internal variability18-23. Here we show that like a butterfly effect24, an infinitesimal random perturbation to identical initial conditions induces vastly different initial ENSO variability, which systematically affects its response to greenhouse warming a century later. In experiments with higher initial variability, a greater cumulative oceanic heat loss from ENSO thermal damping reduces stratification of the upper equatorial Pacific Ocean, leading to a smaller increase in ENSO variability under subsquentgreenhouse warming. This self-modulating mechanism operates in two large ensembles generated using two different models, each commencing from identical initial conditions but with a butterfly perturbation24,25; it also operates in a large ensemble generated with another model commencing from different initial conditions25,26 and across climate models participating in the Coupled Model Intercomparison Project27,28. Thus, if the greenhouse-warming-induced increase in ENSO variability29 is initially suppressed by internal variability, future ENSO variability is likely to be enhanced, and vice versa. This self-modulation linking ENSO variability across time presents a different perspective for understanding the dynamics of ENSO variability on multiple timescales in a changing climate.

Tree-ring δ18O from Southeast China reveals monsoon precipitation and ENSO variability

Considerable advances have been made in use of tree-ring δ18O for climate reconstructions in Southeast China, the East Asian summer monsoon region. However, the relationships among tree-ring cellulose δ18O (δ18Ocell), local hydroclimate, precipitation δ18O (δ18Opre) and El Niño–Southern Oscillation (ENSO) have not yet been fully resolved. The usual interpretation has been that local hydroclimate influences δ18Ocell through both the “amount effect” on δ18Opre and evaporative enrichment, but it cannot fully explain the high inter-site correlation of δ18Ocell chronologies or their response pattern to ENSO. In this study, we use a newly-developed δ18Ocell chronology of Pinus massoniana from a water-stressed site in Zhejiang province, in combination with another three δ18Ocell chronologies in Southeast China, to investigate their climatic implications from a regional perspective. The results show that besides local hydroclimate, δ18Opre is also significantly correlated with δ18Ocell, but with different effects. Spatially homogeneous δ18Opre variation causes high spatial correlations among δ18Ocell from different sites. Analyses show that ENSO variations are responsible for the large-scale common signals in δ18Ocell by modulating δ18Opre. Therefore, combining δ18Ocell chronologies from different locations can enhance ENSO signals, which provides us new opportunities to reconstruct paleo-ENSO activities. Furthermore, eliminating the part of ENSO signal that is not related to the growing season hydroclimate from δ18Ocell can increase the explained variance of observed values. These findings provide a guide for future optimized ENSO and local paleoclimate reconstructions using δ18Ocell.

Testing the Trade Wind Charging Mechanism and Its Influence on ENSO Variability

AbstractDuring the positive phase of the North Pacific Oscillation, westerly wind anomalies over the subtropical North Pacific substantially increase subsurface heat content along the equator by “trade wind charging” (TWC). TWC provides a direct pathway between extratropical atmospheric circulation and El Niño–Southern Oscillation (ENSO) initiation. Previous model studies of this mechanism lacked the ocean–atmospheric coupling needed for ENSO growth, so it is crucial to examine whether TWC-induced heat content anomalies develop into ENSO events in a coupled model. Here, coupled model experiments, forced with TWC favorable (+TWC) or unfavorable (−TWC) wind stress, are used to examine the ENSO response to TWC. The forcing is imposed on the ocean component of the model through the first winter and then the model evolves in a fully coupled configuration through the following winter. The +TWC (−TWC) forcing consistently charges (discharges) the equatorial Pacific in spring and generates positive (negative) subsurface temperature anomalies. These subsurface temperature anomalies advect eastward and upward along the equatorial thermocline and emerge as like-signed sea surface temperature (SST) anomalies in the eastern Pacific, creating favorable conditions upon which coupled air–sea feedback can act. During the fully coupled stage, warm SST anomalies in +TWC forced simulations are amplified by coupled feedbacks and lead to El Niño events. However, while −TWC forcing results in cool SST anomalies, pre-existing warm SST anomalies in the far eastern equatorial Pacific persist and induce local westerly wind anomalies that prevent consistent development of La Niña conditions. While the TWC mechanism provides adequate equatorial heat content to fuel ENSO development, other factors also play a role in determining whether an ENSO event develops.

Tropical Pacific Decadal Variability Induced by Nonlinear Rectification of El Niño–Southern Oscillation

AbstractOn the basis of 32 long-term simulations with state-of-the-art coupled GCMs, we investigate the relationship between tropical Pacific decadal variability (TPDV) and El Niño–Southern Oscillation (ENSO). The first empirical orthogonal function (EOF) mode for the 11-yr moving sea surface temperatures (SSTs) in the coupled models is commonly characterized by El Niño–like decadal variability with Bjerknes air–sea interaction. However, the second EOF mode can be separated into two groups, such that 1) some models have a zonal dipole SST pattern and 2) other models are characterized by a meridional dipole pattern. We found that models with the zonal dipole pattern in the second mode tend to simulate strong ENSO amplitude and asymmetry in comparison with those of the other models. Also, the residual patterns, which are defined as the summation of El Niño and La Niña SST composite anomalies, are very similar to the decadal dipole pattern, which suggests that ENSO residuals can cause the dipole decadal variability. It is found that decadal modulation of ENSO variability in these models strongly depends on the phase of the dipole decadal variability. The decadal changes in ENSO residual correspond well with the decadal changes in the dipole pattern, and the nonlinear dynamic heating terms by ENSO anomalies are well matched with the decadal dipole pattern.

Developing a Coral Proxy System Model to Compare Coral and Climate Model Estimates of Changes in Paleo‐ENSO Variability

AbstractCoral records of surface‐ocean conditions extend our knowledge of interannual El Niño–Southern Oscillation (ENSO) variability into the preinstrumental period. That said, the wide range of natural variability within the climate system as well as multiple sources of uncertainties inherent to the coral archive produce challenges for the paleoclimate community to detect forced changes in ENSO using coral geochemical records. We present a new coral proxy system model (PSM) of intermediate complexity, geared toward the evaluation of changes in interannual variance. Our coral PSM adds additional layers of complexity to previously published transfer functions of sensor models that describe how the archive responds to sea surface temperature (SST) and salinity. We use SST and salinity output from the Community Earth System Model Last Millennium Ensemble 850 control to model coral oxygen isotopic ratios and SST derived from Sr/Ca. We present a detailed analysis of our PSM using climate model output for sites in the central and southwest Pacific before extending the analyses to span the broader tropical Pacific. We demonstrate how variable growth rates, analytical and calibration errors, and age model assumptions systematically impact estimates of interannual variance and show that the relative magnitude of the change in interannual variance is location dependent. Importantly, however, we find that even with the added uncertainties in our PSM, corals from many circum‐Pacific locations are broadly able to capture decadal and longer (decadal+) changes in ENSO variability. Our code is publicly available on GitHub to facilitate future comparisons between model output and coral proxy data.

Effect of ENSO and IOD on the Variability of Sea Surface Temperature (SST) in Java Sea

El-Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) climate variability are global climate variability that can affect oceanographic conditions including SST (Sea Surface Temperature). Located between two oceans, the Indian and the Pacific, the variability of SST in Indonesia is influenced by ENSO and IOD. Previous studies have shown that the influence of ENSO in the Java Sea depends on the season, and while positive (negative) IOD decreases (increase) SST in Indonesian seas. This study aims to examine the effect of ENSO and IOD climate variability on the variability of SST in the Java Sea. SST data are obtained from NOAA Pathfinder and Aqua MODIS satellite image data, while wind data is obtained from ECMWF satellite imagery with long observed data for 36 years (1982-2017) using quantitative methods in spatial and temporal, we found that the influence of ENSO and IOD in Java Sea based on the intensity of the anomaly. The intensity of ENSO which is stronger can affect SST more than IOD.

Modulation of orbitally forced ENSO variation by Tibetan Plateau topography

The modulation of the orbitally induced variation in the El Niño/Southern Oscillation (ENSO) by Tibetan Plateau (TP) topography was investigated with four fully coupled ocean–atmosphere model experiments under the modern boundary conditions. The modeled orbitally induced ENSO change was strongly affected by the presence of the TP. Specifically, in the experiments with orbital forcing at 6 ka in comparison to the counterpart experiments with modern orbital forcing, it was shown that the orbitally forced ENSO variability was slightly weakened by 3% in the presence of the TP but increased significantly by 13% in the simulation of the absence of the TP. This difference was primarily attributed to the anomalous zonal winds over the tropical central-to-eastern Pacific in response to the increased summertime incoming insolation, which was intrinsically related to the different changes in the Asian monsoon and tropical Pacific Walker circulation. Under the absence of modulation by the TP, the anomalous westerly winds dominated the equatorial Pacific and favored the development of a stronger El Niño event and, in turn, the further intensification of La Niña due to the stronger heat discharge during the recession of the stronger El Niño. In contrast, the simulation with the presence of the TP showed the enhanced easterly wind anomalies in the boreal summer over the tropical Pacific, which further reduced (increased) the magnitude of the El Niño (La Niña) event in the subsequent winter. These results suggest that the TP is a potentially crucial boundary condition for evaluating the changes in the ENSO dynamics on orbital scales during the Cenozoic.

A tree-ring δ18O based reconstruction of East Asia summer monsoon over the past two centuries.

The East Asian summer monsoon (EASM) exhibits considerable decadal variations since the late 20th century. Efforts to examine long-term behaviors and dynamics of the EASM are impeded largely due to the shortness of instrumental meteorological records. So far, reconstructions of the EASM with annual resolution from its core regions remain limited. We conduct the first 200-year robust EASM reconstruction based on tree-ring cellulose δ18O records derived from Pinus massoniana trees growing in the middle Yangtze River basin, one of the core EASM areas. The δ18O chronology accounts for 46.2% of the actual variation in an index of the EASM from 1948 to 2014. The reconstructed EASM indicates that the monsoon intensity was below average before the 1950s, peaked in the 1950s-1970s, and then began to decline. The reconstructed EASM is negatively correlated with the El Niño-Southern Oscillation (ENSO), but this teleconnection is dynamic through time, i.e. enhanced (reduced) ENSO variability coheres with strong (weak) EASM-ENSO connections. In addition, despite high ENSO variability since the 1980s, the EASM-ENSO relationship weakened possibly due to anthropogenic impact, particularly aerosol emissions.

Investigating the Role of the Tibetan Plateau in ENSO Variability

ABSTRACTThe role of the Tibetan Plateau (TP) in El Niño–Southern Oscillation (ENSO) variability is investigated using coupled model experiments with different topography setups. Removing the TP results in weakened trade winds in the tropical Pacific, an eastward shift of atmospheric convection center, a shallower mixed layer in the equatorial Pacific, and a flattened equatorial thermocline, which leads to an El Niño–like sea surface temperature (SST) response. In association with these mean climate changes in the tropical atmosphere–ocean system, the ENSO variability exhibits a much stronger amplitude in the world without the TP. Detailed diagnoses reveal that in the absence of the TP, both thermocline feedback in the eastern equatorial Pacific and Ekman pumping feedback in the central-eastern equatorial Pacific are enhanced substantially, leading to stronger ENSO variability. The changes of these two feedbacks are caused by the eastward shift of the atmospheric convection center and enhanced ocean sensitivity; the latter is due to the shallower mixed layer and flattened thermocline. This study suggests that the presence of the TP may be of fundamental importance for modern-day tropical climate variability; namely, the TP may have played a role in suppressing ENSO variability.

Coral δ18O-based reconstruction of El Niño-Southern Oscillation from the northern south China sea since 1851 AD

El Niño-Southern Oscillation (ENSO) is the largest source of interannual climate variability over the globe. Knowledge of ENSO variability back to the pre-instrumental period (and earlier) can help to enhance our understanding of its mechanisms and impacts. Here we use the coral record from the northern South China Sea, where the interannual climate variability is associated with ENSO activity, to reconstruct ENSO variability over the past 150 years. Our record, together with other ENSO chronologies, indicated not only the weakened ENSO activity between ~1930s and ~1960s but also the larger variations of El Niño activity relative to that of La Niña based on the sliding window method. The comparison between the SCS and Pacific ENSO band coral records revealed the relatively stronger climatic coupling between the SCS and the equatorial central-eastern Pacific compared with that between SCS and western Pacific, indicating the reliability of teleconnection relationship between the SCS climate and ENSO. Our result indicated that the coral δ18O record from the SCS could contribute to the pan-Pacific ENSO reconstructions.

Two Aspects of Decadal ENSO Variability Modulating the Long‐Term Global Carbon Cycle

AbstractThe El Niño–Southern Oscillation (ENSO) drives variations in terrestrial carbon fluxes by affecting the terrestrial ecosystem via atmospheric teleconnections and thus plays an important role in interannual variability of the global carbon cycle. However, we lack such knowledge on decadal time scales, that is, how the carbon cycle can be affected by decadal variations of ENSO characteristics. Here we examine how, and by how much, decadal ENSO variability affects decadal variability of the global carbon cycle by analyzing a 1,801‐year preindustrial control simulation. We identify two different aspects, together explaining ~36% of the decadal variations in the global carbon cycle. First, climate variations induced by decadal ENSO‐like variability regulate terrestrial carbon flux and hence atmospheric CO2 on decadal time scales. Second, decadal changes in the asymmetrical response of the terrestrial ecosystem, resulting from decadal modulation of ENSO amplitude and asymmetry, rectify the background mean state, thereby generating decadal variability of land carbon fluxes.

Wind variability over the Caspian Sea, its impact on Caspian seawater level and link with ENSO

AbstractNewly available time series of 10‐m winds over last 60 years in the South Caspian Sea (CS) region show a remarkable shift in wind speed in 1995, that is also the year of maximum elevation of the Caspian Sea level (CSL). Our aim is to find the mechanisms linking these two features. This change is not only seen in the wind observations along the Southern CS coast, but also in the European Centre for Medium‐Range Weather Forecasts (ECMWF) reanalysis covering the Southern CS, leading there to an increase of evaporation after 1995. Due to wind increase, evaporation increases but does not lead to enhanced precipitation over the CS catchment area, the water seems to be lost to the east of the drainage basin for the water budget of the CS after 1995. This stopped the CSL rise and caused its post‐1995 fall. The connection between the wind speed and the trend of the CSL can also be seen for the 1977 low stand. Before 1977, the CSL was slightly dropping with relatively strong wind, then the wind speed fell and the CSL started to rise. The change of the wind seems to be induced by a teleconnection from El Niño‐Southern oscillation (ENSO). It is shown that ENSO impact is much stronger than that of North Atlantic oscillation (NAO), not only for the change of the CSL, but also for several key components of the CS water budget, like the Volga river discharge and wind speed. The wind speed is induced by ENSO, which is demonstrated by a shift of the jet stream over the CS area. This could be an explanative link between ENSO and CSL variability, but still needs further understanding. The NAO has a similar impact but to a lesser degree. When NAO and ENSO are working in the same direction, the CSL change is enhanced like from 1990 to 1995.

Enhanced El Niño–Southern Oscillation Variability in Recent Decades

AbstractThe El Niño–Southern Oscillation (ENSO) represents the largest source of year‐to‐year global climate variability. While Earth system models suggest a range of possible shifts in ENSO properties under continued greenhouse gas forcing, many centuries of preindustrial climate data are required to detect a potential shift in the properties of recent ENSO extremes. Here we reconstruct the strength of ENSO variations over the last 7,000 years with a new ensemble of fossil coral oxygen isotope records from the Line Islands, located in the central equatorial Pacific. The corals document a significant decrease in ENSO variance of ~20% from 3,000 to 5,000 years ago, coinciding with changes in spring/fall precessional insolation. We find that ENSO variability over the last five decades is ~25% stronger than during the preindustrial. Our results provide empirical support for recent climate model projections showing an intensification of ENSO extremes under greenhouse forcing.

A Century of Reduced ENSO Variability During the Medieval Climate Anomaly

AbstractClimate model simulations of El Niño–Southern Oscillation (ENSO) behavior for the last millennium demonstrate interdecadal to centennial changes in ENSO variability that can arise purely from stochastic processes internal to the climate system. That said, the instrumental record of ENSO does not have the temporal coverage needed to capture the full range of natural ENSO variability observed in long, unforced climate model simulations. Here we demonstrate a probabilistic framework to quantify changes in ENSO variability via histograms and probability density functions using monthly instrumental and coral‐based sea surface temperature (SST) anomalies from 1900–2005 and 1051–1150 CE. We find that reconstructed SST anomalies from modern corals from the southwest Pacific capture changes in ENSO variability that are consistent with instrumental SST data from the central equatorial Pacific. Fossil coral records indicate 100 years of relatively lower ENSO variability during part of the Medieval Climate Anomaly. Our results demonstrate that periods of reduced ENSO variability can last a century, far longer in duration than modern observations in the instrumental record of ENSO, but consistent with results from unforced climate model simulations.

ENSO-Like Pacing of the Asian Summer Monsoon during the Early Holocene

We present a 230Th-dated stalagmite oxygen isotope (δ18O) record from Loushanguan Cave in the Yangtze River valley, China. The δ18O record, if viewed as a proxy of the Asian summer monsoon (ASM) intensity, provides an ASM history for the early Holocene with clear centennial-scale variability. A significant approximately 200-yr cycle between 10.2 and 9.1 ka BP (before present, where “present” is defined as the year AD 1950), as revealed by spectral power analyses, is of global significance and is probably forced by the Suess or de Vries cycle of solar activity. Here, we explore a physical mechanism to explain the relationship between the solar activity and the ASM. A strong coherence between the ASM and El Nino-Southern Oscillation (ENSO) has been observed by performing cross-wavelet analyses on this cycle. Our study suggests that a strong (weak) ASM state corresponds to a warm (cold) ENSO, which is consistent with modern meteorological observations but contrasts with previous studies on regions far from the Meiyu rainbelt. We argue that the centennial fluctuations of the ASM are a fundamental characteristic forced by the solar activity, with the ENSO variability as a mediator. The relationship between ENSO and the ASM displayed spatial heterogeneity on the centennial scale during the early Holocene, which is a more direct analogue to the observed modern interannual variability of the ASM.

Climate impacts of the El Niño–Southern Oscillation on South America

The climate of South America (SA) has long held an intimate connection with El Nino, historically describing anomalously warm sea-surface temperatures off the coastline of Peru. Indeed, throughout SA, precipitation and temperature exhibit a substantial, yet regionally diverse, relationship with the El Nino–Southern Oscillation (ENSO). For example, El Nino is typically accompanied by drought in the Amazon and north-eastern SA, but flooding in the tropical west coast and south-eastern SA, with marked socio-economic effects. In this Review, we synthesize the understanding of ENSO teleconnections to SA. Recent efforts have sought improved understanding of ocean–atmosphere processes that govern the impact, inter-event and decadal variability, and responses to anthropogenic warming. ENSO’s impacts have been found to vary markedly, affected not only by ENSO diversity, but also by modes of variability within and outside of the Pacific. However, while the understanding of ENSO–SA relationships has improved, with implications for prediction and projection, uncertainty remains in regards to the robustness of the impacts, inter-basin climate interactions and interplay with greenhouse warming. A coordinated international effort is, therefore, needed to close the observational, theoretical and modelling gaps currently limiting progress, with specific efforts in extending palaeoclimate proxies further back in time, reducing systematic model errors and improving simulations of ENSO diversity and teleconnections. The El Nino–Southern Oscillation exerts a strong influence on the global climate, including South America, where understanding of the phenomenon first emerged. This Review outlines the impacts of the El Nino–Southern Oscillation on South America, focusing on the mechanisms and diversity of resulting teleconnections.

Interannual Southern California Precipitation Variability During the Common Era and the ENSO Teleconnection

AbstractSouthern California's Mediterranean‐type hydroclimate is highly variable on interannual time scales due to teleconnected climate forcings such as the El Niño–Southern Oscillation (ENSO). Here we present subannually resolved scanning X‐ray fluorescence Ti counts from deep‐sea cores in Santa Barbara Basin, California, recording 2,000 years of hydroclimate variability. The reconstructed Southern California precipitation record contains interannual variability in the 2‐ to 7‐year band that could be driven by changes in tropical Pacific ENSO variability and/or the strength of the ENSO teleconnection modulated by extratropical pressure systems. Observed interannual precipitation variance increased and was associated with longer periodicities (5–7 years) when the Intertropical Convergence Zone migrated southward (1370–1540 CE) and the Aleutian Low strengthened creating a robust ENSO teleconnection. Weak interannual precipitation variance with shorter periodicity (2–3 years) was observed when the Intertropical Convergence Zone shifted northward (700–900 CE) and/or the Aleutian Low was weak (1540–1680 CE).