Article

Predicting and Observing El Niño

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Abstract

In October 1974 the occurrence of a weak El Niño event was predicted for early 1975 on the basis of the southern oscillation index. An expedition was organized to observe the event in the waters off Peru and Ecuador during two cruises in order to study its occurrence and its development with time. During the first cruise a massive transgression of warm low salinity water across the equator to 4°S was observed, as well as a depression of the thermocline along the equator and off the coast of South America, indicating the start of El Niño development. During the second cruise the oceanographic situation had changed and conditions were returning to normal.

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... ENSO events occur every 2-7 yr and normally last from 16 to 20 mo (Table 1, Schweigger 1961, Wyrtki et al. 1976, Quinn et al. 1978, Clim. Diag. ...
... Further study of the at-sea habits of this species needed. Wyrtki et al. 1976, Quinn et al. 1978, and others. YEAR STRENGTH 1957-1958strong 1963very weak 1964-1965moderate 1969weak 1972-1973strong 1976-1977moderate 1982strong 1986-1987moderate 1991-1992 ...
... Years of El Niños and strength of event. Data from Schweigger (1961), Wyrtki et al. (1976), Quinn et al. (1978), Climate Diagnostics Bulletin (1982, and others. 1939-1941 strong 1943-1944 weak 1950-1951 weak 1953-1954 moderate 1957-1958 strong 1963-1965 moderate 1969-1970 weak 1972-1973 moderate 1976-1977 moderate 1982-1983 strong 1986-1987 moderate 1990-1991 strong 1993-1995 strong ...
... El Niño events occur every 2-7 yr and normally last 16-20 mo (Table 4). Their effects, while global in extent (Rasmusson andHall 1983, Glynn 1990), are most intense through equatorial Pacific (Wyrtki et al. 1976). During an El Niño, changes in air pressure systems and prevailing winds eventually push warm w. ...
... Strongly affected throughout most of range by El Niño events, which often cause massive breeding failures (Ashmole 1963b, Schreiber and Schreiber 1989, Duffy 1990, Ratcliffe et al. 1999. The effects of these events, while global in extent (Glynn 1990), are most intense through equatorial Pacific (Wyrtki et al. 1976). During an El Niño, changes in major air-pressure systems and prevailing winds push warm Western Pacific waters across the ocean toward the Americas. ...
... Birds throughout world affected by strong events (e.g., 1982-1983), although to a lessening extent with distance from equatorial Pacific and Indian Oceans (Boersma 1978, Rasmussen and Wallace 1983, Duffy et al. 1984, Ainley et al. 1988, Schreiber and Schreiber 1989. Events occur every 2-7 yr, normally last from 16 to 20 mo (Schweigger 1961, Wyrtki et al. 1976, Quinn et al. 1978, Climate Diagnostics Bulletin 1982, Trenberth 1997. ...
... Strongly affected throughout most of range by El Niño events, which often cause massive breeding failures (Ashmole 1963b, Schreiber and Schreiber 1989, Duffy 1990, Ratcliffe et al. 1999. The effects of these events, while global in extent (Glynn 1990), are most intense through equatorial Pacific (Wyrtki et al. 1976). During an El Niño, changes in major air-pressure systems and prevailing winds push warm Western Pacific waters across the ocean toward the Americas. ...
... Birds throughout world affected by strong events (e.g., 1982-1983), although to a lessening extent with distance from equatorial Pacific and Indian Oceans (Boersma 1978, Rasmussen and Wallace 1983, Duffy et al. 1984, Ainley et al. 1988, Schreiber and Schreiber 1989. Events occur every 2-7 yr, normally last from 16 to 20 mo (Schweigger 1961, Wyrtki et al. 1976, Quinn et al. 1978, Climate Diagnostics Bulletin 1982, Trenberth 1997. ...
... Years of El Niños and strength of event. Data from Schweigger (1961), Wyrtki et al. (1976), Quinn et al. (1978), Climate Diagnostics Bulletin (1982, and others. 1939-1941 strong 1943-1944 weak 1950-1951 weak 1953-1954 moderate 1957-1958 strong 1963-1965 moderate 1969-1970 weak 1972-1973 moderate 1976-1977 moderate 1982-1983 strong 1986-1987 moderate 1990-1991 strong 1993-1995 strong ...
... El Niño events occur every 2-7 yr and normally last 16-20 mo (Table 4). Their effects, while global in extent (Rasmusson andHall 1983, Glynn 1990), are most intense through equatorial Pacific (Wyrtki et al. 1976). During an El Niño, changes in air pressure systems and prevailing winds eventually push warm w. ...
... Esta sección tiene como objetivo aportar al conocimiento de la variabilidad interanual de las condiciones oceanográficas de la CPC, haciendo énfasis para ello en el análisis de las variables físicas directamente asociadas con la génesis y evolución de eventos tipo ENOS en el OP. Sin duda, la TSM es considerada una de las variables físicas predictoras más utilizada en la generación de información oportuna frente ocurrencia de anomalías climáticas de distinta periodicidad, dentro de las cuales se encuentran los eventos ENOS (Wyrtki et al., 1976;NOAA, 2019). Por otro lado, dada la importancia de las ondas oceánicas Kelvin ecuatoriales por su asociación con eventos de esta naturaleza, el monitoreo y estudio de variables oceánicas como la temperatura y el nivel del mar, así como a nivel atmosférico, la intensidad y dirección del viento toman considerable relevancia (Alexander et al., 2012). ...
Book
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Capítulo VI - Amenaza por tsunami en la Cuenca Pacífica Colombiana
... Nevertheless, the productivity of the Atacama Desert coastal waters is frequently altered by the El Niño Southern Oscillation (ENSO), defined as a change in the oceanic-atmospheric system that causes significant alterations in climatic behavior along the South American coast. ENSO affects different areas differently, depending on its magnitude, duration and coverage (Wyrtki et al., 1976), and one of its key indicators is ocean surface temperature, which can rise by 1e4 C during an ENSO event, altering environmental conditions and marine ecosystems and having a consequent effect on fishing activity (Santib añez et al., 2005). ...
... For instance, warming of the North Pacific sea surface during ENS0 causes alterations in weather patterns over northern Canada and the United States, most frequently bringing drought to the prairies (Bonsal et al. 1993). Ethiopia and northern India also experience 1982Quinn et al. 1978, Schweigger 1961, Wyrtki et al. 1976 flooding many regions (Ropelewski and Halpert 1987). Northwestern Europe experiences colder than normal winters during ENS0 (Fraedrich and Muller 1992). ...
Article
For a group of birds with similar life-history characteristics (deferred onset of breeding. long life. small clutch size. slow growth). seabirds live in a highly diverse variety of environments in their worldwide distribution . They experience the full gamut of weather patterns. whether daily. seasonally. annually. or on greater scales. and these patterns affect their survival. their habitat. their food supply. their ability to feed. and. thus. the continuing evolution of their species. Effects of weather on birds can be long term, occurring over hundreds of years, or as short as a passing rain storm. The long-term effects of weather on birds undoubtedly have help shaped their particular demography and other life-history characteristics. In the short term, weather effects on seabirds can be seen in more proximate factors: the decision to nest that year or not, where to nest, annual nest success, growth rates of chicks, and survival of adults. Weather can cause the extirpation of a species from an area or only the loss of a few eggs to chilling. It can affect birds directly through increased wind levels or rain causing difficulty in flying, through flooding of nests, and through thermal stress. Effects can also be indirect: weather parameters can alter or destroy nesting habitat, change fish or krill distribution, or cause decreased visibility of prey.
... On the basis of empirical evidence, Bjerknes hypothesized that ENSO was the result of the coupling between eastern and western atmospheric circulations in the Pacific sector and also a coupling between the current and thermal structure of the upper ocean in the eastern equatorial Pacific Ocean. On the basis of a hypothesis linking temperature and wind anomalies, Wyrtki et al. (1976) made the first ENSO forecast. Six major oceanic field programs begun during 1976-1987 provided an observational basis for a better understanding of the annual cycle and interannual variability of the 3 tropical oceans. ...
Article
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The past 2 decades have seen significant improvements in the forecasting of climate variability, based on advances in our understanding of ocean-atmosphere interactions. Such improvements permit the development of applications that predict climate at seasonal to interannual timescales, helping decision makers in the agricultural sector to deal more effectively with the effects of climate variability. The present study describes the current status of agriculture and the need for climate forecasts in light of risk management in rainfed farming, competition for limited water resources, impacts of natural disasters and the multi-dimensional impacts of extreme variability. The short history of climate prediction science demonstrates the progress made in understanding climate variability and the reliability of the predictions in the tropical Pacific region. Several case studies of climate forecast applications are described, illustrating the wide interest in such applications to help the farm sector cope with climate variability. Despite the progress achieved, several challenges lie ahead in enhancing the wider applications of climate forecasts in the agricultural sector. These include the need for improvements in the accuracy of models; generating quantitative evidence about the usefulness of climate forecasts as tools for agricultural risk management; addressing the key issues for promoting beneficial use of forecasts; responding to diverse needs of the users and involving the stakeholders more actively in climate prediction applications; giving greater priority to extension and communication activities; learning from non-adoption situations; deriving more economic benefits through climate prediction applications to trade and storage; and improving the institutional and policy environment.
... Indeed, the presence of El Niño was clearly identified by environmental variables and PC-I, occurring in1982, 1986, 1991, and 1997(Espino and Yamashiro, 2012Meyers et al., 2007;Meinen and McPhaden, 2000). Interannual variability dominated by the El Niño-Southern Oscillation in the study area have been demonstrated byWyrtki et al. (1976), Lynn and Simpson (1987),Blanco et al. (2002), Montecinos et al. (2003), and Hormazábal et al. (2004. The PC-I was significantly correlated with local SST from coastal stations, as well as SST and SSS from surveys. ...
Data
a b s t r a c t The recruitment rate of anchovy in the Peru–Chile upwelling system was studied by testing sensitive to environmental variability when the spawning stock is low in abundance. Times series of sea surface temperature, salinity, depth of the 15 1C isotherm, the upper limit of the oxygen minimum zone, upwelling indices, the Southern Oscillation Index, and indices El Niño 1þ2 and El Niño 3.4 were summarized trough Principal Component Analysis (PCA). The first PCA (PC-I) explained 57% of variance and was related to interannual variability driven by the El Niño-Southern Oscillation. The second Principal Component explained 15% of variance and was linked to upwelling indices. Anchovy recruitment rate anomalies were correlated with PC-I scores on the basis of a 6-year-moving-window and accumulated correlation as time progressed. Signifi-cant correlation coefficients were found when the spawning stock biomass was low in abundance before 1990. Once sufficient
... During the 1970s and 1980s the work of oceanographers (e.g. [13]) was influential in establishing the El Nino as an oceanic phenomenon with profound, large-scale climatic consequences. Climatologists [14,15] had found that the El Nino could be quantified using the Southern Oscillation Index, and that it had a profound effect on south-eastern Australian rainfall. ...
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This brief review identifies seven key science questions in relation to climate variability and change and examines recent research within the Australian and Pacific context: 1. How do the key processes controlling climate variability and predictability operate? 2. What are the nature and causes of regional climate anomalies, past variations in regional climate and extreme weather events and how will they change in the future? 3. How can we provide improved seasonal-to-interannual climate predictions? 4. What are the best projection methods? 5. What are the sea-level changes now and in the future; and how will these impact the coasts? 6. How to have significant benefits on climate service delivery and environmental management? 7. What are the best methods for assessing climate change risks, vulnerability and adaptation options?
... Nevertheless, the productivity of the Atacama Desert coastal waters is frequently altered by the El Niño Southern Oscillation (ENSO), defined as a change in the oceanic-atmospheric system that causes significant alterations in climatic behavior along the South American coast. ENSO affects different areas differently, depending on its magnitude, duration and coverage (Wyrtki et al., 1976), and one of its key indicators is ocean surface temperature, which can rise by 1e4 C during an ENSO event, altering environmental conditions and marine ecosystems and having a consequent effect on fishing activity (Santib añez et al., 2005). ...
Article
The article presents the results of a study conducted on an assemblage of archeofaunal remains from the Copaca 1 archeological site, located on the arid coast of Northern Chile. The site corresponds to an extensive shell midden that was used generally as an occupational site and specifically as a funerary one by specialized marine hunteregatherers exclusively during the Archaic period. The analysis of the faunal remains enabled a general description of the use of local fauna throughout the site's cultural sequence, which range from 7866 to 5040 cal. BP. According to the results obtained, marine and terrestrial fauna, including marine and terrestrial mammals, sea birds, pelagic and oceanic fish, mollusks, crustaceans and equinoderms, were used as a source of both food and technological implements during the Middle Holocene. This implies that the human groups that inhabited Copaca 1 accessed most of the ecoanthropic spheres of the Southern Cone of the Southwestern Pacific coast from early times onward, an adaptation dated since 12,000 BP in the southwestern coast from southern Peru and northern Chile.
... Niue Island lies on the fringes of the PWWP and to the southwest of the South Pacific Convergence Zone (SPCZ) axis (Figure 1). The geographic position of the island causes its inter-annual rainfall pattern to be particularly sensitive to El Niño/Southern Oscillation (ENSO) events such that the incidence of El Niño typically coincides with severe droughts whereas La Niña corresponds with unusually high rainfall (Figure 4) [Wheeler and Aharon, 1997].Figure 12 depicts a remarkably close relationship between the Niue Annual Rainfall (NAR) record (Figure 12c) and ENSO variability record (Figure 12b), expressed as changes in the Southern Oscillation Index (SOI, Tahiti minus Darwin mean sea level pressure difference [Wyrtki et al., 1976]), over the past 90 years. Prominent in both records is the time interval between the late 1940s and 1978– 1979 where changing frequencies in ENSO, attributed to changes in the midlatitude temperature conditions [Gu and Philander, 1997] , left the imprint on NAR as a prolong interval of low rainfall variability (Figure 12). ...
Article
Full-text available
Niue Island is located in close proximity to the epicenter of the South Pacific Convergence Zone (SPCZ), and its rainfall variability is controlled by changes in the phase of the El Niño–Southern Oscillation (ENSO) phenomenon. Four actively growing stalagmites displaying couplets of light and dark calcite layers were sampled from a flank-margin cave on Niue Island in order to determine the dominant climate factor controlling lamina thickness and establish the usefulness of the stalagmites as archives of ENSO variability records. Couplets counting, AMS radiocarbon assays, and growth rates analysis (mean growth rate: 0.34 ± 0.04 mm/yr for n = 604) support the premise that these couplets are annually deposited and their stalagmites contain records of up to two centuries long. Comparison of band thickness records with instrumental records of air temperature and rainfall kept on the island since 1930 and 1906, respectively, suggests that rainfall variability is the dominant controlling factor. Coherency between the spectral power of the annual layers unraveling periodicities at 2.4 and 5.4 years and that of annual and monsoon rainfall at 2.4–2.7 and 5.2 years corroborates the rainfall control on the band thickness variability of the Niuean stalagmites. Phase lags and amplitude discrepancies between rainfall and stalagmite records are attributed to the impact of torrential rains accompanying cyclones that occasionally struck the island. The excellent agreement between the periodicities prominent in the Niuean stalagmites and those typical of the ENSO phenomenon (2.4 and 4.3–6.0 years) suggests the latter exerts a dominant control on the stalagmite growth rates via rainfall variability. Interdecadal periodicities at 10, 14, and 30 years contained in the Niuean stalagmites spectral power are tentatively attributed to ENSO phase changes driven by the Inter-Decadal Pacific Oscillation (IPO). The Niuean stalagmites, exhibiting relative fast growth rates and prominent layered sequences, hold promise to provide continuous century to millennium-long high-resolution atmospheric records of ENSO history that will complement and expand the sea surface temperature records archived in tropical Pacific corals.
... However, as mentioned earlier, both oscillator theories use a linear framework of the equatorial Pacific to depict the periodic features of ENSO; thus, they have inherent deficiencies and cannot fully explain this phenomenon. With increasingly more ENSO events not effectively explained by the simple theoretical models, the idea that "no two events are alike" gradually came into view (Wyrtki et al., 1976). As a result, many studies have been devoted to investigating the uncertainty and complexity of ENSO, and have tried to superimpose the "specialty" they find into the classic periodic framework to complete the ENSO theory. ...
Article
Full-text available
Although the El Niño-Southern Oscillation (ENSO) originates and develops in the equatorial Pacific, it has substantial climatic impacts around the globe. Thus, the ability to effectively simulate and predict ENSO one or more seasons in advance is of great societal importance, but this remains a challenging task. The main obstacles are the diversity, complexity, irregularity, and asymmetry of ENSO. The purpose of this article is to organically integrate the understanding of ENSO based on current progress on the physical mechanisms, prediction, and connections between the interannual ENSO phenomenon and physical processes on other time and space scales, and to provide guidance for future studies by extracting specific important questions.
... Esta sección tiene como objetivo aportar al conocimiento de la variabilidad interanual de las condiciones oceanográficas de la CPC, haciendo énfasis para ello en el análisis de las variables físicas directamente asociadas con la génesis y evolución de eventos tipo ENOS en el OP. Sin duda, la TSM es considerada una de las variables físicas predictoras más utilizada en la generación de información oportuna frente ocurrencia de anomalías climáticas de distinta periodicidad, dentro de las cuales se encuentran los eventos ENOS (Wyrtki et al., 1976;NOAA, 2019). Por otro lado, dada la importancia de las ondas oceánicas Kelvin ecuatoriales por su asociación con eventos de esta naturaleza, el monitoreo y estudio de variables oceánicas como la temperatura y el nivel del mar, así como a nivel atmosférico, la intensidad y dirección del viento toman considerable relevancia (Alexander et al., 2012). ...
... However, no El Niño developed, although he claimed to have observed the conditions required for an El Niño onset (McPhaden, Timmermann, Widlansky, Balmaseda, & Stockdale, 2015;Wyrtki, Stroup, Patzert, Williams, & Quinn, 1976). ...
Chapter
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The El Niño Southern Oscillation is considered to be the most significant form of ‘natural’ climate variability, although its definition and the scientific understanding of the phenomenon is continually evolving. Since its first recorded usage in 1891, the meaning of ‘El Niño’ has morphed from a regular local current affecting coastal Peru, to an occasional Pacific-wide phenomenon that modifies weather patterns throughout the world, and finally to a diversity of weather patterns that share similarities in Pacific heating and changes in trade wind intensity, but exhibit considerable variation in other ways. From the 1960s El Niño has been associated with the Southern Oscillation, originally defined as a statistical relationship in pressure patterns across the Pacific by the British-Indian scientist Gilbert Walker. The first unified model for the El Niño-Southern Oscillation was developed by Jacob Bjerknes in 1969 and it has been updated several times since, but no simple model yet explains apparent diversity in El Niño events. ENSO forecasting has come to be considered a considerable success, but each event still displays surprising characteristics.
... Esta sección tiene como objetivo aportar al conocimiento de la variabilidad interanual de las condiciones oceanográficas de la CPC, haciendo énfasis para ello en el análisis de las variables físicas directamente asociadas con la génesis y evolución de eventos tipo ENOS en el OP. Sin duda, la TSM es considerada una de las variables físicas predictoras más utilizada en la generación de información oportuna frente ocurrencia de anomalías climáticas de distinta periodicidad, dentro de las cuales se encuentran los eventos ENOS (Wyrtki et al., 1976;NOAA, 2019). Por otro lado, dada la importancia de las ondas oceánicas Kelvin ecuatoriales por su asociación con eventos de esta naturaleza, el monitoreo y estudio de variables oceánicas como la temperatura y el nivel del mar, así como a nivel atmosférico, la intensidad y dirección del viento toman considerable relevancia (Alexander et al., 2012). ...
... Esta sección tiene como objetivo aportar al conocimiento de la variabilidad interanual de las condiciones oceanográficas de la CPC, haciendo énfasis para ello en el análisis de las variables físicas directamente asociadas con la génesis y evolución de eventos tipo ENOS en el OP. Sin duda, la TSM es considerada una de las variables físicas predictoras más utilizada en la generación de información oportuna frente ocurrencia de anomalías climáticas de distinta periodicidad, dentro de las cuales se encuentran los eventos ENOS (Wyrtki et al., 1976;NOAA, 2019). Por otro lado, dada la importancia de las ondas oceánicas Kelvin ecuatoriales por su asociación con eventos de esta naturaleza, el monitoreo y estudio de variables oceánicas como la temperatura y el nivel del mar, así como a nivel atmosférico, la intensidad y dirección del viento toman considerable relevancia (Alexander et al., 2012). ...
Book
En el año 2002, el entonces Centro de Control de Contaminación del Pacífico (CCCP) publicó el libro titulado COMPILACIÓN OCEANOGRÁFICA DE LA CUENCA PACÍFICA COLOMBIANA, lo que sería un referente bibliográfico de vital importancia para la caracterización de las zonas marino-costeras del Pacífico colombiano, abarcando un total de cinco capítulos en temas tan variados como las particularidades geográficas de la Cuenca Pacífica Colombiana (CPC) y su investigación oceanográfica, la búsqueda de la relación entre las condiciones oceanográficas de la Cuenca y el ciclo de El Niño Oscilación del Sur (ENOS), además del plan científico del grupo de investigación en oceanografía para el periodo 2001-2010. Han transcurrido 18 largos años desde entonces, y la comunidad científica marina del país, así como la Autoridad Marítima colombiana y el gremio marítimo requieren no solo una actualización de dichas líneas de investigación, sino también mayor cantidad y mejor nivel de detalle en la información disponible para la toma de decisiones con base en el rigor técnico; así como el claro y amplio soporte de conocimiento del medio en el que se desenvuelven para el diario devenir en sus actividades en el mar y en la costa, teniendo en cuenta que las aguas del gran Pacífico no representan la frontera que separa, sino el puente que une a Colombia y los países de Oceanía y del sudeste asiático, considerada como la zona con los mercados de mayor proyección del mundo. Esta es una más de las principales razones, sumada a las necesidades de desarrollo y las aspiraciones nacionales de consolidar factores de seguridad multidimensional y de presencia estatal en las áreas de frontera, para aprovechar las múltiples potencialidades que ofrece el vasto océano Pacífico para una nación en desarrollo, y con la aspiración nacional de llegar a ser una potencia media regional influyente como lo es Colombia. Por lo anterior, el mismo CCCP, ahora denominado Centro de Investigaciones Oceanográficas e Hidrográficas del Pacífico, presenta con orgullo el resultado de un esfuerzo por satisfacer estos requerimientos a través de la publicación del título COMPILACIÓN OCEANOGRÁFICA DEL PACÍFICO COLOMBIANO II, el cual consta de siete capítulos que garantizan la continuidad en los anteriores temas y proporciona algunos nuevos, complementando y ampliando la información ofrecida por la primera edición. Dentro de estas líneas de investigación fueron incluidas las particularidades geográficas y geomorfología de la CPC, su meteorología, la investigación oceanográfica en la Cuenca e influencia de los eventos ENOS, las condiciones de oleaje en el Pacífico colombiano, la variabilidad del nivel del mar, la amenaza por tsunami en la CPC y, finalmente, las tendencias en la biogeoquímica del océano Pacífico Oriental Tropical y Sureste bajo diferentes escenarios de cambio climático. Bienvenidos entonces a una ventana más del conocimiento sobre nuestra Cuenca Pacífica Colombiana, desde donde contribuimos a la “consolidación de Colombia como país marítimo” y aportamos nuestro pequeño pero representativo grano de arena a la defensa del enorme, hermoso e imponente azul de la bandera. El reconocimiento de los espacios marítimos para el desarrollo de un país es de vital importancia. Desde su exploración oceánica y costera, la hidrografía ha representado el conocimiento científico sobre el territorio marítimo colombiano y ha brindado información, instrumentos y herramientas para una mejor compresión y desarrollo de las actividades marítimas en el país. La producción de la cartografía náutica para asegurar las rutas marítimas y el comercio internacional de la nación es un aspecto fundamental, que a su vez ha cumplido un papel importante en el reconocimiento de las profundidades y el descubrimiento de riquezas económicas y culturales en los fondos oceánicos, además de aportar seguridad en la navegación por el espacio marítimo colombiano y un mejor conocimiento de nuestros litorales y sus potencialidades. La hidrografía entonces ha desempeñado eficientemente el rol de fortalecer y desarrollar las riquezas que se encuentran en nuestras aguas jurisdiccionales, y ha sido la disciplina científica que ha aportado al reconocimiento de los territorios costeros y oceánicos, y, consecutivamente, al avance en el desarrollo de la infraestructura marítima para el país. Objetivos que podemos hallar desde sus comienzos y que fueron evidenciados y visibilizados a lo largo de su labor y trabajo en los espacios y frentes marinos, que le han permitido a la Autoridad Marítima Colombiana, a través de un interés nacional y una visión internacional, mantener una navegación segura que haga parte del impulso y progreso económico y nacional, en contribución paralela a los objetivos de desarrollo sostenible de la Organización de las Naciones Unidas.
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A teleconnective linkage between two abyssal water masses consists of one or more zones of interaction, arranged sequentially in space and time. The properties, spatial extent, and advective nature of one of these water masses are directly influenced by the presence of the other via the zones of interaction. The sequence of components in the linkage may in some instances be configured linearly and respond in an irreversible fashion. In other instances the linkage is not unidirectional, but may include one or more feedback “loops” representing the dependence ofeach water mass upon the properties and extent of the other. Three types of water mass interaction are represented in the modern oceans; these are designated as: (1) re-inforcing, (2) lateral blocking/re-direction, and (3) wedging. The criteria for discriminating between these types are geometrical, yet the physical processes and rates of interaction may be distinguishable between, and perhaps characteristics of, these different configurations.
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Two years of satellite-derived maps of sea surface temperature are used to evaluate their oceanographic applications and to study advection in the eastern part of the subtropical gyre of the South Pacific Ocean. The advance and retreat of a tongue of cool water stretching from the coast of Chile to the northwest under the southeast trade winds are analyzed and explained as advection. The time history of the development of this cool tongue is described, and its different behavior during the two years is related to the 1976 El Niño event. During 1976, advection in the subtropical gyre was much weaker than during the year before. It is concluded that satellite-derived surface temperature maps form an important new tool in the analysis and monitoring of the time changes of large-scale thermal features at the surface of the ocean.
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We have made radiocarbon measurements of banded hermatypic corals from Florida, Belize, and the Galapagos Islands. Interpretation is presented here of these previously reported results. These measurements represent the ¹⁴C/¹²C ratios in dissolved inorganic carbon (DIOC) in the surface ocean waters of the Gulf Stream and the Peru Current at the time of coral ring formation. A depletion in radiocarbon concentration was observed incoral rings that grew from A.D. 1900--1952. It was caused by dilution of existing ¹⁴C levels with dead COâ from fossil fuel burning (the Suess effect, or S/sub e/). A similar trend was observed in the distribution of bomb-produced ¹⁴C in corals that had grown during the years following A.D. 1952. The concentration of bomb-produced radiocarbon was much higher in corals from temperate regions (Florida, Belize, Hawaiian Islands) than in corals from tropical regions (Galapagos Islands and Canton Island). The apparent radiocarbon ages of the surface waters in temperate and tropical oceans during the preanthropogenic period range from about 280 to 520 years B.P. (-40 to -69%). At all investigated locations, it is likely that waters at subsurface depths have the same apparent radiocarbon age of about 670 years B.P. From the change of oceanic ..delta..¹⁴C in the surface during post-bomb times, the approximate annual rate of net input of ¹⁴COâ to the ocean waters is calculated to be about 8% of the prevailing ¹⁴C difference between atmosphere and ocean. From this input and from preanthropogenic ..delta..¹⁴C values found at each location, it can be seen that vertical mixing of water in the Peru Current is about 3 times greater than that in the Gulf Stream.
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The rise and fall of the Peruvian anchoveta fishery provides an interesting case study of the mixture of socioeconomic, oceanographic, meteorological, and biological factors that can affect fish populations in coastal upwelling regions. The purpose of this paper is to identify some of the societal factors that might have an adverse effect on the rational management of this fishery. The paper focuses on views expressed in the social and physical sciences literature that relate successes and failures of fisheries management to activities at the international level, the national level, or to individual behavior. While some of the factors occurring at the three levels of analysis are obvious to those involved in fisheries, the effect of others are not so obvious. This framework for analysis of natural resource issues might offer a new approach to an improved understanding of how societies interact with their physical and biological environments.
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The termination of the Equatorial Undercurrent (EUC) in the eastern tropical Pacific has been studied through analysis of the historical hydrographic station data in the region bounded by 5°N, 10°S, 80°W and 100°W. Three distinctive hydrographic features associated with the EUC are used, along with dynamic topography, to trace the mean path of the EUC and to investigate aspects of its seasonal variation. These features are (1) the 13°C thermostad, (2) the high-salinity core, and (3) the high dissolved oxygen concentration tongue.
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In the equatorial Pacific, between the Galapagos Islands and the coast of South America, two kinds of upwelling of oceanic waters occur. One is related to coastal upwelling and the other to surfacing of the Equatorial Undercurrent. Both of those processes are associated with the development of the southeast trade winds blowing in this area. Coastal upwelling is increased when the trade winds are intensified, and the surfacing of the Equatorial Undercurrent occurs when the trades weaken. The development of coastal upwelling and the surfacing of the Equatorial Undercurrent are inferred from the radiolarian assemblages in the sediments. The abundance of quartz, opal, and radiolarian assemblages in the deep-sea sediments of this area, as well as the distance from the sample locations to land and to the quartz source, is correlated with the intensity of the trade winds (in February and August) through multiple regression analysis. The chronostratigraphy of core V1929 (3°35′S, 83°56′W), used in this study, is inferred on basis of its δ180 record. During the last 75,000 years, the fluctuations in intensity of the trade winds have been concurrent with or preceded the fluctuations in the amount of ice stored on the continents. In general, the wind velocity of the winter trades has been intensified during cool climatic stages of the earth (δ180 stages 4 and 2) and they have been relaxed during warm stages (δ180 stages 3 and 1). Seasonal contrast of the trade winds has also fluctuated within time, having been relatively high during the upper part of δ180 stage 3.
Article
This article reviews recent advances in ocean circulation models and climate interactions. Related reviews of one-dimensional models and models of equatorial and polar regions are given in this Quadrennial Report by Garwood [1979], O'Brien [1979] and Baker [1979], respectively. Related reviews of climate are given in the Meteorology section of the Quadrennial Report by Gates [1979], Kutzbach [1979], Perry [1979], and Rotty and Marland [1979]. Several detailed review articles on ocean circulation models and climate were written in the last four years. National Academy of Sciences [1975], U. S. Committee for GARP [1975] and WMO/ICSU [1975] give the status at the beginning of this review period while Pond and Bryan [1976] and Holland [1977a] represent more recent reviews. Kraus [1977] contains review articles on modeling the upper ocean, while Gribbin [1978] contains review articles on the ocean's role in climatic change. The latest detailed reviews of ocean circulation models and their relation to climate were presented at a JOC/SCOR Joint Study Conference held in Helsinki in May, 1977 [WMO/ICSU, 1977]. Many of these reviews will be published in a forthcoming issue of Dynamics of Atmospheres and Oceans. The present review begins with studies of the possible effect of ocean temperature variabilities on the atmosphere, and then proceeds to studies using idealized basin models, world ocean models, and finally coupled ocean-atmosphere models.
Article
Shipboard measurements of atmospheric 222Rn, CO, and CH4 and of dissolved CO in surface waters have been carried out in the equatorial Pacific on a cruise from Ecuador to Hawaii, Tahiti and Panama in March and April of 1974, and during transit from Los Angeles to Antarctica in November and December of 1972. The trace gas results, combined with conventional meteorological data and with satellite images from Nimbus 5 and the defense meteorological satellite project (DMSP), have provided descriptions of the intertropical convergence zones (ITCZ) near 04°N, 102°W and 03°N, 154°W in March of 1974, near 04°N, 86°W in April of 1974, and near 05°N, 139°W in November of 1972. In all cases the ITCZ seems to be located north of the south equatorial current (SEC) as shown by dissolved CO peaks in surface waters. In April of 1974 a 'second' ITCZ was observed near 01°S, 102°W just south of the SEC. A stationary front near Hawaii (20°N, 147°W) in March of 1974 was investigated. The ITCZ was marked by light shifting winds near a zone of heavy cloud cover and precipitation. In the eastern Tropical Pacific atmospheric 222Rn increases distinctly north of the ITCZ and thus serves as an indicator for the ITCZ. CO and CH4 do not always increase coincident with atmospheric 222Rn. The atmospheric features of the stationary front near Hawaii are in many ways similar to those observed for the ITCZ. The front is marked by cloud cover, precipitation zone and light shifting winds. 222Rn, CO and CH4 increase signifantly behind the front in subsiding air which was traced back to the Asian continent. The variation of atmospheric 222Rn, CO and CH4 with time and geographical area over the equatorial Pacific seems to be a consequence of seasonal variations of the trade wind field and long range transport to the central Pacific from Asia and to the eastern equatorial Pacific from North and Central America.
Article
Is El Niño one phase of a continual, self-sustaining natural mode of the coupled ocean-atmosphere that has La Niña as the complementary phase? Or is El Niño a temporary departure from "normal" conditions "triggered" by a random disturbance such as a burst of westerly winds? A growing body of evidencestability analyses, studies of the energetics, simulations that reproduce the statistics of sea surface temperature variations in the eastern equatorial Pacificindicates that reality corresponds to a compromise between these two possibilities: The observed Southern Oscillation between El Niño and La Niña corresponds to a weakly damped mode that is sustained by random disturbances. This means that the predictability of El Niño is limited by the continual presence of "noise" so that forecasts should be probabilistic. The Southern Oscillation is also subject to decadal modulations. How it will be influenced by global warming is a matter of considerable uncertainty.
Article
Stable oxygen isotope ratios from annually banded corals are correlated with historical records of sea surface temperature in the central and eastern tropical Pacific Ocean. El Nino events between 1929 and 1976 are detected using this method, but there are discrepancies between the records of El Ninos from corals and those determined using historical hydrographic and meteorologic data. The average annual depletion of delta O-18 during El Nino events is greater at the Galapagos Island sites (0.45 percent) than at the Fanning and Canton Island sites in the mid-Pacific (0.20-0.30 percent and less than 0.2 percent, respectively). Of prime importance is evidence of decade time scale variability of sea surface temperature (SST) in the tropical Pacific. In particular, annually averaged SST appears to have been 0.5-1 C higher in the eastern tropical Pacific during the 1930s than during subsequent years. A significant net flux of CO2 from the surface ocean to the atmosphere is envisioned during these periods of higher SST.
Article
The Peruvian anchovy industry grew at a compound rate of 42 percent between 1956 and 1965, making Peru the largest fish producer in the world. Between 1967 and 1971 annual catches averaged 10.5 million metric tons. However, in 1972 the anomalous ocean current known as El Nino combined with over-exploitation to decimate the anchovy stock. Anchovy harvests fell by 55 percent in 1972 and another 51 percent in 1973. Despite the efforts of the Institutio del Mar del Peru, an incomplete understanding of the anchovy's behavior and imperfect management practices led to severe economic hardship.This paper presents an anchovy population dynamics model implemented as a computer simulation. It incorporates aspects of several general population models in the literature, the peculiar characteristics of the anchovy ecosystem, and Peru's specific economic needs. Our goal was to find the optimal management policy that can be practically implemented and to develop a methodology that can be applied to other situations. The model indicated that Peru should limit fishing to the springtime and use quotas that favor large modern purse seiners.
Article
Dissolved organic matter was isolated from coastal and open-ocean surface waters having a wide range of biological productivities, and from seawater of intermediate depths. Approximately 50% of the organic matter was recovered by the use of activated-charcoal chromatography. The organic matter isolated from different types of water masses exhibited varying spectroscopic characteristics, and stable carbon-isotope compositions. The ability of the isolated organic matter to interact with copper ions also varied, but over a relatively narrow range which was not exceeded by more than a factor of two by similarly isolated terrigenous organic matter.
Article
The equatorial ocean has always captured the attention of oceanographers. Almost all medium-to-large scale oceanic motions are dominated by the effect of the earth's rotation, the Coriolis acceleration. At the equator, this apparent acceleration vanishes and very special physics apply. The most striking phenomena is upwelling that occurs in a narrow latitude band a few degrees wide along the equator due to the prevailing easterlies (westward winds).
Chapter
A linear numerical model forced by ship-board wind estimates for each month from January, 1961 to December, 1978, has been used to study the interannual variability of the tropical Pacific Ocean. Model pycnocline variations at several stations are similar to the observed sea level fluctuations. El Nino events are depicted as periods when the pycnocline is persistently deep along the eastern boundary. Remotely forced equatorial Kelvin waves are responsible for this response. The character of each simulated El Nino is strongly dependent on the relation between zonal wind stress changes in the western and central equatorial Pacific. A rapid shoaling of the pycnocline in the western tropical Pacific during each El Nino is caused by westward-propagating Rossby waves. Interannual pycnocline displacements in the central equatorial Pacific are determined by the superposition of Kelvin waves excited to the west and first-mode Rossby waves generated to the east.
Article
There are two aspects to environmental risk management. The first is the protection of the environment from human-induced activity. The second is the protection of humans from the damage that the environment may cause - especially as a result of the manifestation of extreme natural hazards. This chapter, though dealing cursorily with protection of the natural environment, will focus on the second aspect that is specifically manifest in the question: how can we protect people from extreme natural hazards? This expression of the question emphasises that the problem is one that links science and society. Knowledge of the extreme natural hazard is an outcome of focussed scientific knowledge. Protection is an outcome of social organisation, community structures, communication, and preparedness. The two are, of course, related. Social organisation develops as a result of the occurrence of past events and disasters. Scientific knowledge, especially when in the form of forecasts, provides the information needed to mobilise societal response. State of the Environment reporting, The success of the Australian society in protecting the environment from human-induced activity is reported every five years in a document known as the State of the Environment Report. The latest State of the Environment Report was issued in 2011 and is abbreviated as SoE2011. SoE2011 has volumes that deal with the following aspects of the Australian environment: atmosphere, inland water, land, marine environment, Antarctic environment, biodiversity, heritage, built environment, and coasts.
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von Storch, H., J. Sündermann and L. Magaard, 2000: Interview with Klaus Wyrtki. GKSS 99/E/74, 42 pp; also in Historisch-Meereskundliches Jahrbuch 2000, Vol. 7, 49-94; also in M. Jochum and T. Murtugudde (eds.), 2006: Physical Oceanography. Developments since 1950, Springer Verlag, ISB 0-387-30261-1, 203-238; also online by the Niels-Bohr Library and Archives of the Center for History of Physics
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Interviews with five significant scientists, all in English
Article
The El NinÂo-Southern Oscillation (ENSO) phenomenon is the strongest year-to-year climate fluctuation on our planet, with impacts that are felt worldwide in both natural systems and human affairs. Jacob Bjerknes, a Norwegian-American meteorologist, famous for his work in the early twentieth century on polar fronts, cyclones, and dynamical weather forecasting, became interested in the El NinÂo problem. He demonstrated that El NinÂo developed through positive feedbacks between the ocean and atmosphere, in which a weakening of the equatorial Pacific trade winds would cause a rise in sea surface temperatures (SSTs), leading to a further weakening of the trades. Klaus Wyrtki of the University of Hawaii began systematic studies of wind-driven ocean circulation in the early 1970s. Wyrtki demonstrated that for a 1-2-year period before El NinÂo, stronger than normal trade winds in the central Pacific would pile up excess warm water in the western basin via an intensified westward-flowing South Equatorial Current. A sudden relaxation of the trades in the central equatorial Pacific would then allow this warm water to slosh back toward the east in the form of an eastward-propagating equatorial Kelvin wave. William Quinn of Oregon State University was developing a prediction scheme for El NinÂo based on the Southern Oscillation index (SOI). Today we can generate historical reconstructions of oceanic variability by combining information from ocean models, atmospheric forcing, and ocean observations.
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The historical effects of El Niño/La Niña events on supplies of selected fresh vegetables and melons (Cucumis melo L.) were evaluated by estimating single-equation supply relationships. Economic variables in the estimated equations were, generally, of the correct sign and significant at usual levels. El Niño events had a negative and statistically significant effect on the Texas muskmelon, Florida fall squash [Praecitrullus fistulosus Stocks) Pang.] and the California fall lettuce (Lactuca sativa L.) supply with expected production declines of 15%, 21%, and 5% relative to historical mean production. In contrast, the expected supplies of United States summer onions (Allium cepa L.) and Florida fall and winter tomatoes (Lycopersicon esculentum Mill.) increased about 7%, 10%, and 25% during El Niño events. La Niña events had a negative and significant effect on Texas muskmelon, honeydew, and watermelon, with supplies expected to decline 20%, 29%, and 13% with the occurrence of this event.
Chapter
Instead of attempting to write an entire book on innovative uses of the ocean I have chosen to highlight some of the more probable future possibilities and avoid the impractical and improbable. In particular, I emphasize possibilities for using the ocean as a source of energy, the interaction of the ocean and climate, fresh water from the ocean, the ocean as an ultimate resting place for nuclear wastes, and imaginative uses of, for example, satellites and the organisms in the ocean. It goes without saying that other major innovative uses of the ocean are likely to be developed that have been completely unanticipated in the writing of the chapter.
Article
The purpose of this article is to explore the connection between past and present environments and evolutionary forces operating on Darwin's finches. The finches diversified from a single ancestral stock on the modern Galápagos Islands probably between 0.5 and 1.5 million years before present. During this time, they were probably exposed to fluctuating climates, and some species are likely to have gone extinct. Climatic conditions have varied from present conditions to much drier ones in the last 50,000 years, during which time all modern species of finches were present. Currently, some finch populations are subjected to intense directional selection on morphological variation in times of drought when food supply is low; possibly selection operates also under extreme wet conditions, but in an opposite direction. Unusually dry conditions and unusually wet conditions each occur once every decade, on average. Given a potential life span of 15 to 20 years, an individual finch may experience at least one drought and one wet year in its life-time. The main implication of these results and suggestions is that natural selection, both in the past and currently, is responsible for at least some and perhaps most of the differences between species. Modern analyses of selection can be extrapolated to yield estimates of the forces and conditions necessary to transform one species into another in the past, which is the key evolutionary process in the adaptive radiation. /// La finalidad de este artículo es explorar la conección entre el ambiente actual y pasado y las fuerzas evolucionarias operante en los pinzones de Darwin. Los pinzones se han diversificado a partir de un único grupo ancestral en las modernas islas Galápagos probablemente entre los últimos 0,5 y 1,5 millones de años. Es muy probable que durante ese tiempo los pinzones se vieran expuestos a climas fluctuantes y quizas algunas especies se extinguieran. Las condiciones climáticas han variado desde las condiciones actuales a otras mucho más secas en los últimos 50.000 años, tiempo en el cual todas las especies modernas de pinzones, ya existían. Actualmente, algunas poblaciones de pinzones están sujetas a una intensa selección direccional en variaciones morfológicas en tiempos de sequía cuando hay poca disponibilidad de comida; posiblemente la selección también se produce en condiciones de extrema humedad, pero en dirección contraria. Como promedio, una vez en cada década se dan condiciones de inusual sequía y así como también de humedad extraordinaria. Si consideramos que los pinzones tienen un lapso potencial de vida de entre 15 y 20 años, un individuo puede experimentar al menos una vez en su vida un año de inusual sequía y otro de inusual humedad. La principal implicatión de estos resultados y sugerencias es que la selección natural, tanto en el pasado como actualmente, es responsable de al menos algunas y quizás la mayoría, de las diferencias entre especies. Se pueden extrapolar modernos analisis de selección para producir estimaciones de las fuerzas y condiciones necesarias en el pasado, para transformar una especie en otra, lo cual es la llave de los procesos evolucionarios en radiación adaptativa.
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El Niño‐Southern Oscillation (ENSO), the primary source of year‐to‐year climate variability on Earth, has profound impacts on the Indian Ocean dipole (IOD), another important climate pattern. Much attention has been paid to potentially increased ENSO predictability by utilizing IOD conditions, inferred from a statistically significant correlation with ENSO at a long lead time. However, the intrinsic dynamics for the causality of this IOD‐ENSO relationship remain largely elusive. Here, we demonstrate that the observed nonstationary IOD‐ENSO lead‐lag relationship is mainly ENSO‐driven and therefore adds no additional information for ENSO predictability. The nonstationarity of their correlation is a manifestation of ENSO cycle complexity. Multi‐climate model and theoretical results further demonstrate that ENSO pacing tightly controls the statistical IOD‐ENSO relationship via changes in ENSO periodicity and regularity. This highlights that ENSO dominates the inter‐basin Pacific‐Indian Ocean interactions, shedding light on the key predictors for interannual pantropical climate variability.
Article
Recent debate about the development of complex societies on the north coast of Peru has turned on the relative importance of marine vs. terrestrial resources and the extent to which different resource zones are upset by El Niño/Southern Oscillation (ENSO) events. While ENSO events are cited frequently as having important consequences for Prehispanic Andean societies, in fact there are few archaeological data about the nature of cultural responses to a specific ENSO event. Archaeological data from two Chimu settlements in the Casma Valley, Peru—Quebrada Sta. Cristina and Manchan—document the occurrence of a fourteenth-century A.D. ENSO event and some of the cultural responses to that prehistoric El Niño.
Article
In this review, the history of El Nino research is traced from its beginnings through the key innovations of Bjerknes and Wyrtki to the unusual 1982-1983 event. Recent research is then reviewed, with detailed discussions of two important processes: instability growth and vacillation between climate states. Throughout the paper there are adjunct discussions of extraregional teleconnections, ecological impacts, and research on El Nino in the ancient record. The final section discusses the present paradigm for vacillations between El Nino and non-El Nino states and speculates on the possibly chaotic nature of El Nino. -from Author
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El Niño-Southern Oscillation is a warming of surface sea temperatures in the eastern Pacific Ocean. Such climatic and oceanographic perturbations have dramatic impacts upon human adaptation and sociocultural development. Evidence multidisciplinary Artificial a mound of dirt in the ceremonial center of Valdivia The Emerancia have documented the abandonment of the site in relation to the El Niño phenomenon. The intial site abandonment was in response to intense or mega event dated to 2150 BC, associated withe the formation of the beach, singing fossil reoccupation C14 and dated ca 2200-1450 BC and final abandonment dated to 1450 B.C. Final abandonment is associated with an earthquake and a short-lived reoccupation. Data from excavation, regional settlement patterns and shellfish frequencies are presented to determine whether repeated and final site abandonment was related to El Niño. Results indicate widespread environmental degradation and geomorphological changes to the surrounding coastline were related to El Niño, and that it was clearly a factor to sociocultural development and adaptive responses. These data explore chronology, assess the intensities, and measure the effects of ancient El Niño events upon pre-Hispanic occupations this ceremonial center and pre-Hispanic occupations along the Arenillas River valley, El Oro Province, Ecuador.
Article
Of the many canal systems of the Chimu empire the Chicama-Moche Intervalley (La Cumbre) Canal connecting the Chicama and Moche valleys represents the highest level of technical achievement. This paper examines the engineering skills of the Chimu as revealed by computer analysis of the open channel flow design techniques they utilized. Analysis of agricultural strategies made possible by this canal and the surveying skills inherent to its use are examined in detail. The presence of many trial canal paths toward the distal end of the canal indicate extreme difficulty in overcoming tectonically induced ground-slope changes caused by fault lines near the intervalley divide. The canal was abandoned prior to completion of construction and thus never served to supply the Moche Valley with Chicama water.
Article
Southern Oscillation indices (differences in sea level atmospheric pressure between Easter Island and Darwin, Australia, and between Juan Fernandez Island and Darwin) were treated so as to emphasize interannual changes and considered for monitoring unusual equatorial Pacific ocean-atmosphere developments and certain of their consequences (e.g., El Niño invasions). It now appears that their trends can be used to predict activity of El Niño intensity several months in advance.
Article
Circulation around the South Pacific anticyclone causes cold water to upwell along the South American coast and along the equator cast of the date line. Normally the atmospheric circulation in the equatorial region is weakest in April, when the Northern Hemisphere near-equatorial convergence is closest to the equator.Six times in the past 80 years, large positive surface temperature anomalies developed along the Peruvian coast and over a large part of the tropical Pacific and persisted for a year or more-the phenomenon now generally known as El Niño. In the past, data from isolated islands were used in attempts to explain the accompanying meteorological events; understandably a variety of hypotheses resulted.In the intense 1972-73 El Niño (March 1972-March 1973) extensive weather satellite data have removed much of the observational uncertainty of earlier studies. The Northern Hemisphere near-equatorial convergence shifted about 3° closer to the equator near the Line Islands while the equatorial "doldrum" belt shifted from west of the date line to cast of the date line. In the equatorial strip, the El Niño year was relatively wet in the central Pacific, but relatively dry in the western Pacific, while in the eastern Pacific no coherent pattern emerged. Certainly no positive correlation could be established between anomalies of sea surface temperature and of rainfall.Our preliminary findings suggest that contrary to previous opinion, ocean-atmosphere feedback may not be important in maintaining El Niño, which could he a Pacific manifestation of a global phenomenon.
Article
El Nino is the occasional appearance of warm water off the coast of Peru; its presence results in catastrophic consequences in the fishing industry. A new theory for the occurrence of El Nino is presented. It isshown that El Nino is not due to a weakening of the southeast trades over the waters off Peru, but that during the two years preceding El Nino, excessively strong southeast trades are present in the central Pacific.These strong southeast trades intensify the subtropical gyre of the South Pacific, strengthen the SouthEquatorial Current, and increase the east-west slope of sea level by building up water in the western equatorial Pacific. As soon as. the wind stress in the central Pacific relaxes, the accumulated water flows eastward,probably in the form of an internal equatorial Kelvin wave. This wave leads to the accumulation of warmwater off Ecuador and Peru and to a depression of the usually shallow thermocline. In total, El Nino is theresult of the response of the equatorial Pacific Ocea...
Article
Geostrophic water transport by the equatorial countercurrent is compared with the observed sea level difference between two pairs of islands situlated north and south of the current. The high correlation between the transport and the sea level difference makes it possible to construct a time series for the countercurrent transport over a 21-year period. The countercurrent carries warm water into the eastern tropical Pacific, and fluctuations in its strength give rise to temperature anomalies off Central America. Periods of exceptionally high transport by the countercurrent in the western Pacific coincide with the occurrence of El Niño several thousand kilometers downstream and demonstrate the existence of teleconnections between events in the Pacific Ocean.
Survey of El Nino 1957-58 in its relation to tropical Pacific meteorology
  • J Bjerknes
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