ENSO as an integrating concept in earth science

The El Ni?o-Southern Oscillation (ENSO) cycle of alternating warm El Ni?o and cold La Ni?a events is the dominant year-to-year climate signal on Earth. ENSO originates in the tropical Pacific through interactions between the ocean and the atmosphere, but its environmental and socioeconomic impacts are felt worldwide. Spurred on by the powerful 1997-1998 El Ni?o, efforts to understand the causes and consequences of ENSO have greatly expanded in the past few years. These efforts reveal the breadth of ENSO's influence on the Earth system and the potential to exploit its predictability for societal benefit. However, many intertwined issues regarding ENSO dynamics, impacts, forecasting, and applications remain unresolved. Research to address these issues will not only lead to progress across a broad range of scientific disciplines but also provide an opportunity to educate the public and policy makers about the importance of climate variability and change in the modern world.     

Impacts of a global climate cycle on population dynamics of a migratory songbird

Progress toward understanding factors that limit abundances of migratory birds, including climate change, has been difficult because these species move between diverse locations, often on different continents. For black-throated blue warblers (Dendroica caerulescens), demographic rates in both tropical winter quarters and north temperate breeding grounds varied with fluctuations in the El Ni?o Southern Oscillation. Adult survival and fecundity were lower in El Ni?o years and higher in La Ni?a years. Fecundity, in turn, was positively correlated with subsequent recruitment of new individuals into winter and breeding populations. These findings demonstrate that migratory birds can be affected by shifts in global climate patterns and emphasize the need to know how events throughout the annual cycle interact to determine population size.     

Oceanographic events during el nino

El Ni?o events, the most spectacular instances of interannual variability in the ocean, have profound consequences for climate and the ocean ecosystem. The 1982-1983 El Ni?o is perhaps the strongest in this century. El Ni?o events usually have followed a predictable pattern, but the recent event differs markedly. The physical oceanography of this El Ni?o is described and compared with that of earlier events.     

An Improved Procedure for EI Nino Forecasting: Implications for Predictability

A coupled ocean-atmosphere data assimilation procedure yields improved forecasts of El Ni?o for the 1980s compared with previous forecasting procedures. As in earlier forecasts with the same model, no oceanic data were used, and only wind information was assimilated. The improvement is attributed to the explicit consideration of air-sea interaction in the initialization. These results suggest that EI Ni?o is more predictable than previously estimated, but that predictability may vary on decadal or longer time scales. This procedure also eliminates the well-known spring barrier to EI Ni?o prediction, which implies that it may not be intrinsic to the real climate system.     

El Nino on the Devil's Staircase: Annual Subharmonic Steps to Chaos

The source of irregularity in El Ni?o, the large interannual climate variation of the Pacific ocean-atmosphere system, has remained elusive. Results from an El Ni?o model exhibit transition to chaos through a series of frequency-locked steps created by nonlinear resonance with the Earth's annual cycle. The overlapping of these resonances leads to the chaotic behavior. This transition scenario explains a number of climate model results and produces spectral characteristics consistent with currently available data.     

Meteorological aspects of the el nino/southern oscillation

The single most prominent signal in year-to-year climate variability is the Southern Oscillation, which is associated with fluctuations in atmospheric pressure at sea level in the tropics, monsoon rainfall, and wintertime circulation over North America and other parts of the extratropics. Although meteorologists have known about the Southern Oscillation for more than a half-century, its relation to the oceanic El Ni?o phenomenon was not recognized until the late 1960's, and a theoretical understanding of these relations has begun to emerge only during the past few years. The past 18 months have been characterized by what is probably the most pronounced and certainly the best-documented El Ni?o/Southern Oscillation episode of the past century. In this review meteorological aspects of the time history of the 1982-1983 episode are described and compared with a composite based on six previous events between 1950 and 1975, and the impact of these new observations on theoretical interpretations of the event is discussed.     

Permanent El Niño-like conditions during the Pliocene warm period

During the warm early Pliocene (approximately 4.5 to 3.0 million years ago), the most recent interval with a climate warmer than today, the eastern Pacific thermocline was deep and the average west-to-east sea surface temperature difference across the equatorial Pacific was only 1.5 +/- 0.9 degrees C, much like it is during a modern El Ni?o event. Thus, the modern strong sea surface temperature gradient across the equatorial Pacific is not a stable and permanent feature. Sustained El Ni?o-like conditions, including relatively weak zonal atmospheric (Walker) circulation, could be a consequence of, and play an important role in determining, global warmth.     

The Pliocene paradox (mechanisms for a permanent El Niño)

During the early Pliocene, 5 to 3 million years ago, globally averaged temperatures were substantially higher than they are today, even though the external factors that determine climate were essentially the same. In the tropics, El Ni?o was continual (or "permanent") rather than intermittent. The appearance of northern continental glaciers, and of cold surface waters in oceanic upwelling zones in low latitudes (both coastal and equatorial), signaled the termination of those warm climate conditions and the end of permanent El Ni?o. This led to the amplification of obliquity (but not precession) cycles in equatorial sea surface temperatures and in global ice volume, with the former leading the latter by several thousand years. A possible explanation is that the gradual shoaling of the oceanic thermocline reached a threshold around 3 million years ago, when the winds started bringing cold waters to the surface in low latitudes. This introduced feedbacks involving ocean-atmosphere interactions that, along with ice-albedo feedbacks, amplified obliquity cycles. A future melting of glaciers, changes in the hydrological cycle, and a deepening of the thermocline could restore the warm conditions of the early Pliocene.     

A 5000-year record of extreme floods and climate change in the southwestern United States

A 5000-year regional paleoflood chronology, based on flood deposits from 19 rivers in Arizona and Utah, reveals that the largest floods in the region cluster into distinct time intervals that coincide with periods of cool, moist climate and frequent El Ni?o events. The floods were most numerous from 4800 to 3600 years before present (B.P.), around 1000 years B.P., and after 500 years B.P., but decreased markedly from 3600 to 2200 and 800 to 600 years B.P. Analogous modern floods are associated with a specific set of anomalous atmospheric circulation conditions that were probably more prevalent during past flood epochs.     

Cool La Niña during the warmth of the Pliocene?

The role of El Ni?o-Southern Oscillation (ENSO) in greenhouse warming and climate change remains controversial. During the warmth of the early-mid Pliocene, we find evidence for enhanced thermocline tilt and cold upwelling in the equatorial Pacific, consistent with the prevalence of a La Ni?a-like state, rather than the proposed persistent warm El Ni?o-like conditions. Our Pliocene paleothermometer supports the idea of a dynamic "ocean thermostat" in which heating of the tropical Pacific leads to a cooling of the east equatorial Pacific and a La Ni?a-like state, analogous to observations of a transient increasing east-west sea surface temperature gradient in the 20th-century tropical Pacific.     

Eocene El Niño: evidence for robust tropical dynamics in the "hothouse"

Much uncertainty surrounds the interactions between the El Ni?o-Southern Oscillation (ENSO) and long-term global change. Past periods of extreme global warmth, exemplified by the Eocene (55 to 35 million years ago), provide a good testing ground for theories for this interaction. Here, we compare Eocene coupled climate model simulations with annually resolved variability records preserved in lake sediments. The simulations show Pacific deep-ocean and high-latitude surface warming of approximately 10 degrees C but little change in the tropical thermocline structure, atmosphere-ocean dynamics, and ENSO, in agreement with proxies. This result contrasts with theories linking past and future "hothouse" climates with a shift toward a permanent El Ni?o-like state.     

2005—2016年中国东海鲐鱼渔场的时空分布及与海表面温度的关联

根据2005—2016年7—9月中国远洋渔业数据中心提供的我国东海鲐鱼捕捞数据,结合关键因子海表面温度(sea surface temperature, SST),计算各年鲐鱼渔场经纬度重心,量化鲐鱼渔场重心的时空变化。进一步分析捕捞努力量在经度、纬度以及SST上的分布规律,并基于聚类法筛选出代表年份,评估异常气候事件对鲐鱼渔场内SST及渔场重心时空分布的影响。研究结果显示,鲐鱼渔场重心具有明显的年际和月间变化,7—9月渔场逐渐向东北方向移动,且主要分布渔场SST为25～28℃。聚类分析将各月份渔场重心分为4类,其中2007和2015年渔场分布具有显著差异。此外,鲐鱼渔场内SST与尼诺指数具有显著的正相关关系,且代表年份2007和2015年分别对应拉尼娜事件和厄尔尼诺事件,当拉尼娜事件发生时,渔场内SST上升,渔场重心逐渐北移;而厄尔尼诺事件发生时,渔场内SST下降,渔场重心主要分布在南部海域。研究表明,中国东海鲐鱼渔场时空分布受到厄尔尼诺和拉尼娜调控的海表面温度变化的显著影响。     

Climatic anomalies in the tropical pacific ocean and corn yields in the United States

The association between climatic anomalies in the tropical Pacific Ocean, often called El Ni?o events, and annual corn production in the United States was investigated. Temperature and atmospheric pressure in parts of the United States have been correlated with El Ni?o events. This research suggests that in years in which an El Ni?o event causes surface temperatures in the tropical Pacific to become warmer than normal, there is a higher probability of an above-average corn crop in the United States. For years when sea surface temperatures are average or cool, no significant association is observed.     

Modeling ocean circulation

Ocean numerical models have become quite realistic over the past several years as a result of improved methods, faster computers, and global data sets. Models now treat basin-scale to global domains while retaining the fine spatial scales that are important for modeling the transport of heat, salt, and other properties over vast distances. Simulations are reproducing observed satellite results on the energetics of strong currents and are properly showing diverse aspects of thermodynamic and dynamic ocean responses ranging from deep-water production to EI Ni?o. Now models can represent not only currents but also the consequences for climate, biology, and geochemistry over time spans of months to decades. However, much remains to be understood from models about ocean circulation on longer time scales, including the evolution of the dominant water masses, the predictability of climate, and the ocean's influence on global change.     

El Niño-like pattern in ice age tropical Pacific sea surface temperature

Sea surface temperatures (SSTs) in the cold tongue of the eastern equatorial Pacific exert powerful controls on global atmospheric circulation patterns. We examined climate variability in this region from the Last Glacial Maximum (LGM) to the present, using a SST record reconstructed from magnesium/calcium ratios in foraminifera from sea-floor sediments near the Galápagos Islands. Cold-tongue SST varied coherently with precession-induced changes in seasonality during the past 30,000 years. Observed LGM cooling of just 1.2 degrees C implies a relaxation of tropical temperature gradients, weakened Hadley and Walker circulation, southward shift of the Intertropical Convergence Zone, and a persistent El Ni?o-like pattern in the tropical Pacific. This is contrasted with mid-Holocene cooling suggestive of a La Ni?a-like pattern with enhanced SST gradients and strengthened trade winds. Our results support a potent role for altered tropical Pacific SST gradients in global climate variations.     

Variations in the rotation of the Earth

Variations in the earth's rotation (UT1) and length of day have been tracked at the submillisecond level by astronomical radio interferometry and laser ranging to the LAGEOS satellite. Three years of regular measurements reveal complex patterns of variations including UT1 fluctuations as large as 5 milliseconds in a few weeks. Comparison of the observed changes in length of day with variations in the global atmospheric angular momentum indicates that the dominant cause of changes in the earth's spin rate, on time scales from a week to several years, is the exchange of angular momentum between the atmosphere and the mantle. The unusually intense El Ni?o of 1982-1983 was marked by a strong peak in the length of day.     

Reduced interannual rainfall variability in East Africa during the last ice age

Interannual rainfall variations in equatorial East Africa are tightly linked to the El Ni?o Southern Oscillation (ENSO), with more rain and flooding during El Ni?o and droughts in La Ni?a years, both having severe impacts on human habitation and food security. Here we report evidence from an annually laminated lake sediment record from southeastern Kenya for interannual to centennial-scale changes in ENSO-related rainfall variability during the last three millennia and for reductions in both the mean rate and the variability of rainfall in East Africa during the Last Glacial period. Climate model simulations support forward extrapolation from these lake sediment data that future warming will intensify the interannual variability of East Africa's rainfall.     

ENSO drove 2500-year collapse of eastern Pacific coral reefs

Cores of coral reef frameworks along an upwelling gradient in Panamá show that reef ecosystems in the tropical eastern Pacific collapsed for 2500 years, representing as much as 40% of their history, beginning about 4000 years ago. The principal cause of this millennial-scale hiatus in reef growth was increased variability of the El Ni?o-Southern Oscillation (ENSO) and its coupling with the Intertropical Convergence Zone. The hiatus was a Pacific-wide phenomenon with an underlying climatology similar to probable scenarios for the next century. Global climate change is probably driving eastern Pacific reefs toward another regional collapse.     

Breeding patterns of galapagos penguins as an indicator of oceanographic conditions

Surface water changes associated with El Ni?o have been known to affect deleteriously top carnivores along coastal South America. Data on the breeding strategies of Galápagos penguins and other seabirds indicate that the biological effects of El Ni?o extend much farther west. The breeding biology of these seabirds is adapted to frequent changes in productivity which are associated with El Ni?o.