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The Easter Island Province (EIP) encompasses Easter Island (EI) and Salas y Gómez Island (SGI), which are located in the eastern boundary of the south Pacific subtropical gyre. This province is one of the most oligotrophic region in the world ocean with a high degree of endemism and distinguished by having the clearest waters in the world. Issues related to the biophysical coupling that sustains biological production in this region are still poorly understood. Satellite data compiled over a ten year period was used to characterize the spatial and temporal chlorophyll-α (Chl-α) variability around the EIP and determine the relationship between Chl-α and several physical forcing. Results shows a clear Chl-α annual cycle around the EIP, with maximum concentration during the austral winter. Chl-α spatial distribution shows a strong zonal dipole over EI that divides the island into two zones: southeast and northwest. Due to its small size and low elevation of SGI, it does not generate a significant local effect in Chl-α concentration, but a Chl-α increase is observed southeast of this island (~2 km) associated to a seamount. The mean geostrophic current in the EIP flows eastward, associated with the southeastern boundary of the subtropical gyre. However, recurrent mesoscale eddies traveling northwestward and produce large surface current variability with periods of high velocities in opposite direction. In the spring, wakes of high Chl-α concentration can be observed over EI, associated with the generation and detachment of submesoscale eddies from EI, which could have important biological implications during periods of low regional biological production.

Regional Ocean Modeling System (ROMS) results, combined with chlorophyll-α (Chl-α) and satellite altimetry information as well as information from oceanographic cruises were analyzed to identify interactions between intrathermocline eddies (ITEs) and the Juan Fernández Archipelago (JFA), and discuss their potential impact on surface Chl-α concentrations. The JFA is located off the coast of central Chile (33°S), and is composed of three main islands: Robinson Crusoe (RC), Alejandro Selkirk (AS) and Santa Clara (SC). Results indicate that the surface and subsurface anticyclonic eddies that interact with the JFA are formed primarily within the coastal transition zone between 33° and 39°S. ITEs are present within the JFA region with a semiannual frequency, mainly during the austral autumn, and have a weak surface expression in relation to the adjacent surface eddies, with a slow displacement (1.16 to 1.4 km d-1) in a northwest direction and a coherent structure for periods of ≥ 1 year. During the ITEs' interaction with RC-SC islands and an adjacent seamount, a slight (prominent) thermocline deflection of the upper limit (lower) was observed. The horizontal extent (~70-100 km) was greater than the internal Rossby deformation radius and the average vertical extent was ~400 m. The interaction between the weak surface expression of ITEs, identified with satellite altimetry, and the JFA persisted during autumn for nine weeks until reaching the winter period. Approximately one month after the beginning of the interaction between ITEs and the islands, increases in surface Chl-α associated with the eddy were observed, with values up to three times higher than adjacent oceanic waters.

Las fluctuaciones en abundancia, biomasa, estructura de edad y patrones de distribución de los recursos pesqueros responden, entre otros, a la variabilidad ambiental. Estas respuestas son consecuencia tanto de efectos climáticos directos sobre los recursos como indirectos actuando sobre niveles tróficos relacionados. En este estudio se revisa: i) el estado del conocimiento de los mecanismos físicos asociados a la variabilidad océano-atmósfera y las escalas de variabilidad espaciales y temporales del ambiente y la relación con recursos marinos, basados en datos observacionales y modelos hidrodinámicos, ii) la relación ambiente-recurso para pesquerías pelágicas, demersales y bentónicas, y el uso de modelos biofísicos para entender estas relaciones, iii) manejo actual de recursos pelágicos, demersales y bentónicos y los alcances en relación al uso de variables ambientales, y iv) se discuten los desafíos hacia la asesoría en relación a las estrategias para mejorar la comprensión de la relación ambiente-recurso, así como, las estrategias para incorporar la modelación biofísica y variables ambientales en modelos operacionales para la asesoría hacia el manejo.

The eastern boundary of the Chile-Peru Current System constitutes one of the most biologically productive ecosystems in the world, due largely to coastal upwelling and the horizontal advection of nutrients. In this ecosystem, El Niño events are of great importance in the interannual variability of the environment. A change was observed in the environmental regime at the beginning of the 1970s with the onset of the 1972-1973 El Niño, marking an important decrease in the anchovy fishery (Engraulis ringens). After the mid-1970s, sardine (Sardinops sagax) landings increased noticeably. A second regime shift at the end of the 1980s was seen mostly in the noticeable recovery of anchovy and the decline of sardine. Herein, we present an integrated conceptual model of the different local and large-scale phenomena that affect the marine environment off northern Chile and the distribution and abundance of pelagic resources. The model considers an analysis of environmental and bio-fishery data on different scales and describes how the interdecadal (associated with re-gime shifts) and interannual (associated with El Niño events) fluctuations in the Equatorial Pacific are mani-fested in the eastern South Pacific and, therefore, in the northern zone off Chile, affecting the annual eyele, the dynamic of the coastal trapped waves, and coastal upwelling. In this framework, interdecadal fluctuations play an important role in the anchovy-sardine-anchovy replacement sequence.El borde oriental del Sistema de Corrientes de Chile-Perú constituye uno de los ecosistemas de mayor productividad biológica del mundo, debido principalmente a la surgencia costera y advección horizontal de nutrientes. En este ecosistema, los eventos El Niño son de mayor importancia en la variabilidad interanual del ambiente. No obstante, un cambio de régimen ambiental es observado a inicio de los 70's el que hubiera comenzado con El Niño 1972-73 y que marca la gran disminución de la pesquería de anchoveta (Engraulis ringens); en tanto, desde mediado de los 70's los desembarques de sardina (Sardinops sagax) aumentan notablemente. Un segundo cambio de régimen se observa a finales de los 80's, representado principalmente por la notable recuperación de anchovy y disminución de sardina. Se presenta un modelo conceptual integrador de los diferentes fenómenos locales y de gran escala que afectan el ambiente marino del norte de Chile, y la distribución y abundancia de recursos pelágicos. El modelo considera análisis de datos ambientales y bio-pesqueros a distintas escalas, y describe como las fluctuaciones interdecadales (asociadas a cambios de régimen) e interanuales (asociadas a los eventos El Niño) del Pacífico Ecuatorial se manifiestan en el Pacífico Sur Oriental y por tanto en la zona norte de Chile, afectando el ciclo anual, la dinámica de las ondas atrapadas a la costa y la surgencia costera. En este marco, las fluctuaciones interdecadales estarían jugando un rol importante en la secuencia del reemplazo anchoveta-sardina-anchoveta.

Ten years of continuous current meter recordings near the core of the Peru-Chile Undercurrent (PCU) over the continental slope at 30°S off Chile, local and equatorial wind stress data, and monthly oceanographic sections off Valparaíso (33°S) are used to study the variability of the PCU and the Oxygen Minimum Zone (OMZ) off Chile. The physics that governs the PCU variability differs for intraseasonal periods and for longer periods: Coastal trapped waves dominate the intraseasonal band whereas Rossby waves dominate for periods greater than about 120 days. Semiannual and annual period fluctuations can largely be explained by Rossby waves forced by equatorial Kelvin waves and local winds. Seasonal variations in the PCU are strongly modulated over El Niño/La Niña cycles. During warm El Niño events, the PCU undergoes strong, semiannual variability whereas during La Niña events, annual variability dominates. These results together with oceanographic sections off Valparaíso suggest that Rossby waves provide a physical mechanism to explain a significant fraction of seasonal variability observed in the OMZ. During the downwelling (upwelling) phase of these waves the poleward (equatoward) flow is stronger (90° out of phase with respect to sea level), the isotherms are deeper (shallower), the OMZ thickness increases (decreases), the mean concentration of salinity and silicate increases (decreases) and oxygen concentration and nitrate deficit decrease (increase) in the OMZ.Una década de registros continuos de corrientes medidas cerca del núcleo de la corriente subsuperficial de Perú-Chile (PCU), sobre el talud continental en los 30°S frente a Chile, datos del esfuerzo del viento a lo largo del ecuador y a lo largo de la costa de Chile, además de secciones oceanográficas realizadas mensualmente frente a Valparaíso (33°S), son usados para estudiar la variabilidad de la PCU y la zona de mínimo de oxígeno (OMZ) frente a Chile. La física que gobierna la variabilidad de la PCU es diferente entre periodos intraestacionales y periodos mayores. Ondas atrapadas a la costa dominan la banda intraestacional mientras que las Ondas de Rossby dominan en periodos mayores que 120 días. Fluctuaciones con periodos anuales y semi anuales pueden ser largamente explicadas por ondas de Rossby forzadas por ondas de Kelvin ecuatoriales y por vientos locales. Variaciones estacionales en la PCU son fuertemente moduladas por los ciclos de El Niño/La Niña. Durante los eventos calidos de El Niño, la variabilidad semi anual de la PCU se intensifica, mientras que durante los eventos fríos de La Niña la señal anual es dominante. Estos resultados junto a las secciones oceanográficas realizadas frente a Valparaíso, sugieren que las ondas de Rossby entregan el mecanismo físico para explicar una fracción significativa de la variabilidad estacional observada en la OMZ. Durante la fase de hundimiento (surgencia) de esas ondas el flujo se intensifica (90° desfasado respecto del nivel del mar) hacia el polo (ecuador), las isotermas son mas profundas (más someras), el espesor de la OMZ incrementa (disminuye), la concentración media de salinidad y silicato incrementa (disminuye), y el oxígeno y el déficit de nitrato disminuye (incrementa) en la OMZ.

The goal of the Pacific Ocean Boundary Ecosystem and Climate Study (POBEX) was to diagnose the large-scale climate controls on regional transport dynamics and lower trophic marine ecosystem variability in Pacific Ocean boundary systems. An international team of collaborators shared observational and eddy-resolving modeling data sets collected in the Northeast Pacific, including the Gulf of Alaska (GOA) and the California Current System (CCS), the Humboldt or Peru-Chile Current System (PCCS), and the Kuroshio-Oyashio Extension (KOE) region. POBEX investigators found that a dominant fraction of decadal variability in basin- and regional-scale salinity, nutrients, chlorophyll, and zooplankton taxa is explained by a newly discovered pattern of ocean-climate variability dubbed the North Pacific Gyre Oscillation (NPGO) and the Pacific Decadal Oscillation (PDO). NPGO dynamics are driven by atmospheric variability in the North Pacific and capture the decadal expression of Central Pacific El Niños in the extratropics, much as the PDO captures the low-frequency expression of eastern Pacific El Niños. By combining hindcasts of eddy-resolving ocean models over the period 1950–2008 with model passive tracers and long-term observations (e.g., CalCOFI, Line-P, Newport Hydrographic Line, Odate Collection), POBEX showed that the PDO and the NPGO combine to control low-frequency upwelling and alongshore transport dynamics in the North Pacific sector, while the eastern Pacific El Niño dominates in the South Pacific. Although different climate modes have different regional expressions, changes in vertical transport (e.g., upwelling) were found to explain the dominant nutrient and phytoplankton variability in the CCS, GOA, and PCCS, while changes in alongshore transport forced much of the observed long-term change in zooplankton species composition in the KOE as well as in the northern and southern CCS. In contrast, cross-shelf transport dynamics were linked to mesoscale eddy activity, driven by regional-scale dynamics that are largely decoupled from variations associated with the large-scale climate modes. Preliminary findings suggest that mesoscale eddies play a key role in offshore transport of zooplankton and impact the life cycles of higher trophic levels (e.g., fish) in the CCS, PCCS, and GOA. Looking forward, POBEX results may guide the development of new modeling and observational strategies to establish mechanistic links among climate forcing, mesoscale circulation, and marine population dynamics.

Time-space fluctuations of chlorophyll-a (Chl-a) within the region off central-southern Chile (33–42°S), and their association with meteorological-oceanographic conditions, were analyzed using satellite time series data (2002–2012). The mean distribution of moderate values of Chl-a (~0.5 mg∙m−3) in the northern section (33–38°S) extended out to ~200 km of the coast whereas they were restricted to a narrower band in the southern section (38–42°S). Mean wind stress and wind stress curl were upwelling favorable for most part of the year in the northern section whereas upwelling-downwelling periods were distinct in the southern section. The dominant frequency of Chl-a variability in the coastal zone and the coastal transition zone was annual, as it was for the rest of the variables, except in a transitional band between these zones and where a semi-permanent jet is located. At the annual frequency, the alongshore distribution of coastal Chl-a presented strong discontinuities, with minimum values around upwelling centers (~37 and 40°S) and higher values (> 2 mg∙m−3) in between. Also at the annual frequency, correlation analyses suggest that Ekman transport and Ekman pumping might act synchronously to extend the offshore distribution of the highest Chl-a values during the spring-summer period whereas mesoscale activity appears to contribute to Chl-a increases in the coastal transition zone. Sea surface temperature does not appear to be associated with the annual cycle of Chl-a in the coastal zone and in the coastal transition zone it might be linked to Chl-a variability through the effects of internal waves.

Se utilizan dieciocho anos de datos satelitales de nivel del mar y esfuerzo del viento, en la región del Pacifico suroriental, para mostrar las cualidades del Multitaper Method - Singular Value Decomposition (MTM-SVD) como método de análisis de múltiples series de tiempo distribuidas en extensas áreas del océano. Se realiza una exhaustiva revisión del MTM-SVD, propuesto inicialmente por Mann & Park (1999), y se implementan los algoritmos computacionales en MATLAB, para aprovechar las capacidades de despliegue gráfico de los resultados y facilitar su interpretación y análisis. El MTM-SVD permitió obtener una visión general de las principales frecuencias de variabilidad del nivel del mar, determinar la fracción de la varianza explicada para cada una de estas frecuencias en las distintas regiones de la zona de estudio y determinar sus patrones de oscilación, tanto estacionarios como de propagación. Dentro de las principales frecuencias de variabilidad se encuentra que la senal anual e interanual domina en forma significativa gran parte del registro del nivel del mar en el Pacifico suroriental. La senal anual está asociada a las fluctuaciones del esfuerzo del viento y a la propagación de ondas de Rossby. La senal interanual se encuentra fuertemente asociada a las fluctuaciones de El Niño y la Oscilación del Sur, que se extiende en la región mediante perturbaciones generadas en la costa, que posteriormente viajan hacia el oeste a una velocidad cercana a la velocidad teórica de propagación del primer modo baroclino de una onda de Rossby.Eighteen years of satellite data on sea level and wind stress in the southeastern Pacific region, were used to show the capabilities of Multitaper Method - Singular Value Decomposition (MTM-SVD) as a valuable method to analyze multiple time series distributed over a large area on the ocean. Here we performed a comprehensive review of the MTM-SVD method,that was first proposed by Mann & Park (1999), and also we done an implementation of the MTM-SVD algorithms in MATLAB (MAtrix LABoratory), in order to take advantage of the graphical capabilities that brings this computational language and make easier the result interpretation. The MTM-SVD allowed to obtain a regional view of the main frequencies of sea level variability, and showed the explained variance along the study area for each frequency. Besides, the method also shown the spatial oscillation patterns on each frequency, both stationary or propagation patterns. A significant annual and interannual variability appear dominate much of the sea level fluctuations in the southeastern Pacific. The annual signal was found associated with the wind stress and the propagation of a Rossby wave. The interannual signal was strongly observed associated with the El Niño and the Southern Oscillation. On these frequencies the sea level perturbations were generated on the coast, and then traveling westward at a speed close to the theoretical propagation of the first baroclinic mode of a Rossby wave.

Understanding the influence of mesoscale and submesoscale features on the structure of phytoplankton is a key aspect in the assessment of their influence on marine biogeochemical cycling and cross-shore exchanges of plankton in Eastern Boundary Current Systems (EBCS). In this study, the spatio-temporal evolution of phytoplankton size classes (PSC) in surface waters associated with mesoscale eddies in the EBCS off central-southern Chile was analyzed. Chlorophyll-a (Chl-a) size-fractionated filtration (SFF) data from in situ samplings in coastal and coastal transition waters were used to tune a three-component (micro-, nano-, and pico-phytoplankton) model, which was then applied to total Chl-a satellite data (ESA OC-CCI product) in order to retrieve the Chl-a concentration of each PSC. A sea surface, height-based eddy-tracking algorithm was used to identify and track one cyclonic (sC) and three anticyclonic (ssAC1, ssAC2, sAC) mesoscale eddies between January 2014 and October 2015. Satellite estimates of PSC and in situ SFF Chl-a data were highly correlated (0.64 < r < 0.87), although uncertainty values for the microplankton fraction were moderate to high (50 to 100% depending on the metric used). The largest changes in size structure took place during the early life of eddies (~2 months), and no major differences in PSC between eddy center and periphery were found. The contribution of the microplankton fraction was ~50% (~30%) in sC and ssAC1 (ssAC2 and sAC) eddies when they were located close to the coast, while nanoplankton was dominant (~60–70%) and picoplankton almost constant (

In Eastern Boundary Upwelling Systems, cold coastal waters are separated from offshore by a strong cross-shore Sea Surface Temperature (SST) gradient zone. This upwelling front plays a major role for the coastal ecosystem. This paper proposes a method to automatically identify the front and define its main characteristics (position, width, and intensity) from high resolution data. The spatio-temporal variability of the front characteristics is then analyzed in a region off Central Chile (37°S), from 2003 to 2016. The front is defined on daily 1 km-resolution SST maps by isotherm T0 with T0 computed from mean SST with respect to the distance from the coast. The probability of detecting a front, as well as the front width and intensity are driven by coastal wind conditions and increased over the 2007–2016 period compared to the 2003–2006 period. The front position, highly variable, is related to the coastal jet configuration and does not depend on the atmospheric forcing. This study shows an increase by 14% in the probability of detecting a front and also an intensification by 17% of the cross-front SST difference over the last 14 years. No trend was found in the front position.

An approach that improves the spectral-based PHYSAT method for identifying phytoplankton functional types (PFT) in satellite ocean-color imagery is developed and applied to one study case. This new approach, called PHYSTWO, relies on the assumption that the dominant effect of chlorophyll-a (Chl-a) in the normalized water-leaving radiance (nLw) spectrum can be effectively isolated from the signal of accessory pigment biomarkers of different PFT by using Empirical Orthogonal Function (EOF) decomposition. PHYSTWO operates in the dimensionless plane composed by the first two EOF modes generated through the decomposition of a space–nLw matrix at seven wavelengths (412, 443, 469, 488, 531, 547, and 555 nm). PFT determination is performed using orthogonal models derived from the acceptable ranges of anomalies proposed by PHYSAT but adjusted with the available regional and global data. In applying PHYSTWO to study phytoplankton community structures in the coastal upwelling system off central Chile, we find that this method increases the accuracy of PFT identification, extends the application of this tool to waters with high Chl-a concentration, and significantly decreases (~60%) the undetermined retrievals when compared with PHYSAT. The improved accuracy of PHYSTWO and its applicability for the identification of new PFT are discussed.