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Turbidity is a key indicator of water quality. It has biotic effects due to low penetration of light into the water such as photosynthesis reduction. The seasonal and interannual variability of turbidity in the Eastern Tropical Pacific coast of Mexico were analyzed using ocean color data. The region has an extended continental shelf, with several river discharges and marked seasonal patterns of wind. Remote sensing data (1998 to 2017) of reflectance, wind, rainfall, and river discharges were analyzed through Hovmoller diagrams and Empirical Orthogonal Functions. The results indicated that wind stress explained 76% of the turbidity variance, while 8% was explained by river discharges and rainfall. In winter, turbidity is intensified by resuspension mechanisms in front of the southern river mouths. In spring, turbidity increases due to phytoplankton particulate concentrations enhanced by coastal upwelling. During summer and autumn, wind stress is weaker and river discharges increase, thus turbidity increases in front of northern river mouths. El Nino-Southern Oscillation generates turbidity anomalies by alteration of rainfall and wind stress. Despite the proximity of the river mouths, the coastal water turbidity is explained by different processes, which need to be assessed in coastal management.

An analysis of the main remotly sensed oceanographic variables was conducted to characterize the dominant drivers that modulate the spatial-temporal variability of coastal phytoplankton biomass in the northern limit of the Eastern Tropical Pacific. The phytoplankton biomass was analyzed using monthly average satellite chlorophyll (Chlo) concentration data from MODIS sensors for the period 2003–2017. Oceanographic conditions were analyzed by considering (i) Sea Surface Temperature (SST) high-resolution data from the GHRSST project, (ii) wind stress calculated with data from the zonal and meridional components of the CCMP product, (iii) climatological precipitation, and (iv) climatological river flow. Chlo time series and spatial variability were analyzed using Hovmoller diagrams and Empirical Orthogonal Functions (EOF), respectively. A strong semi-annual signal in Chlo concentration along the coast was observed: the first peak occurs in winter-spring (5.0 mg·m−3) and a second one in summer-autumn (6.5 mg·m−3). A high year-round average of Chlo concentration (3.0–15.0 mg·m−3) was maintained by a 10 km wide along-shore coast, with maximum values spatially associated with river mouths, of which Santiago river registered the highest Chlo values (20.0 mg·m−3). Surface oceanographic conditions showed a marked annual cycle with warmer conditions (30–31 °C) from July to October and colder ones (23–24 °C) from December to April; during the cold period, seasonal wind stress stimulated coastal upwelling. The EOF showed that 70% of Chlo concentration variability was controlled by the semi-annual pattern, which responded to coastal upwelling conditions during cold period, while rivers outflows influenced high Chlo concentration during the warm period. These results highlighted the importance for land-ocean interface to sustain coastal ecosystems' biological production and the major role of watersheds as sources of nutrients to maintain high biological production during warm periods in transitional tropical-subtropical zones.

Surface oceanic fronts are regions characterized by high biological activity. Here, Sea Surface Temperature (SST) fronts are analyzed for the period 2003–2019 using the Multi-scale Ultra-high Resolution (MUR) SST product in northern Patagonia, a coastal region with high environmental variability through river discharges and coastal upwelling events. SST gradient magnitudes were maximum off Chiloé Island in summer and fall, coherent with the highest frontal probability in the coastal oceanic area, which would correspond to the formation of a coastal upwelling front in the meridional direction. Increased gradient magnitudes in the Inner Sea of Chiloé (ISC) were found primarily in spring and summer. The frontal probability analysis revealed the highest occurrences were confined to the northern area (north of Desertores Islands) and around the southern border of Boca del Guafo. An Empirical Orthogonal Function analysis was performed to clarify the dominant modes of variability in SST gradient magnitudes. The meridional coastal fronts explained the dominant mode (78% of the variance) off Chiloé Island, which dominates in summer, whereas the SST fronts inside the ISC (second mode; 15.8%) were found to dominate in spring and early summer (October–January). Future efforts are suggested focusing on high frontal probability areas to study the vertical structure and variability of the coastal fronts in the ISC and its adjacent coastal ocean.

The response of primary producers to seasonal and interannual variabilities in the hydrographic conditions observed between 1997 and 2012 is analyzed for the southern portion of the California Current System (CCS). The analysis uses the optimum rate of primary productivity (PP) normalized by units of chlorophyll (Chla) in the water column (PBopt) and Chla concentration. In situ PP estimations using the 14C method were obtained as part of the seasonal cruises conducted by the Investigaciones Mexicanas de la Corriente de California program. Supplementary data included sea surface temperature (SST) as measured by the AVHRR sensor from 1985–2009. We found the mean value of PBopt to be at 5.1 ± 3.3 mg C·(mg Chla)–1·h–1, with maximum ranges of 0.5 and 17.5 mg C·(mg Chla)–1·h–1. The relationship between PBopt and SST suggested a phytoplankton community change at around 19 oC, which characterized the transitional nature of the southern portion of the CCS. SST data suggested, on the one hand, that on average the 19 oC isotherm is located in the vicinity of Punta Eugenia and, on the other, that its spatial variability defined the alternating cool–warm conditions. At the seasonal scale, this isotherm showed a marked latitudinal displacement (from 24oN to 32oN), which was observed to be even out of this range during interannual events associated with El Nino/La Nina. Under both cool-warm hydrographic conditions, the phytoplanktonic community showed large PBopt rates (~6 mg C·(mg Chla)–1·h–1). At the interannual scale, changes were associated to changes in the abundance and composition of nano-microphytoplankton. Additionally, data suggested that high PP rates during warm periods could be attributed to an enhanced picoplankton contribution. Se analizo la respuesta de los productores primarios a la variabilidad estacional e interanual de las condiciones hidrograficas en la region sur del Sistema de la Corriente de California (SCC) entre 1997 y 2012. El analisis se basa en la tasa optima de productividad primaria (PP) normalizada por unidad de clorofila (Chla) en la columna de agua (PBopt) y en la concentracion de Chla. Como parte del monitoreo que realiza el programa de Investigaciones Mexicanas de la Corriente de California, se obtuvieron para cada estacion del ano datos de PP in situ con la tecnica de 14C. La informacion se complemento con datos de la temperatura superficial del mar (TSM) medida por el sensor AVHRR de 1985 a 2009. El analisis de los datos de TSM demostro que, en el promedio de largo periodo, la isoterma de 19 oC se ubico en las inmediaciones de punta Eugenia y que su variabilidad espacial permite seguir la alternancia del cambio entre las condiciones frias y calidas. En la escala estacional, esta isoterma presento un marcado desplazamiento latitudinal (de 24oN a 32oN), y se extiendio aun mas durante eventos interanuales asociados a El Nino/La Nina. El valor promedio del PBopt fue de 5.1 ± 3.3 mg C·(mg Chla)–1·h–1 y vario de 0.5 a 17.5 mg C· (mg Chla)–1·h–1. La relacion entre el PBopt y la TSM sugiere un cambio en la comunidad del fitoplancton a los 19 oC, lo que se considero como una respuesta al caracter transicional del SCC. La comunidad fitoplanctonica mantuvo altas tasas promedio de PBopt (~6 mg C·(mg Chla)–1·h–1) en ambas condiciones hidrograficas (frio/calido). Las variaciones en la escala estacional e interanual del PBopt estuvieron asociados a cambios en la composicion y abundancia del nano-microfitoplancton. Los datos sugieren que las altas tasas PP en periodos calidos pueden atribuirse a la contribucion del picoplancton.

La península de Mejillones (23°S) es un bloque estructural que se proyecta más de 40 km desde la costa en la zona norte de Chile dando forma a las bahías de Mejillones y Moreno abiertas hacia el norte y el sur, respectivamente. La variabilidad oceanográfica de mesoescala asociada a esta península fue analizada utilizando información satelital de temperatura superficial del mar, concentración de clorofila-a, transporte de Ekman y corrientes geostróficas. Mediante el uso de diagrama Hovmöller y Funciones Empíricas Ortogonales estacional e interanual se demuestra el rol que juega la península de Mejillones en la variabilidad de los parámetros oceanográficos en el norte de Chile. El decaimiento latitudinal de la temperatura y clorofila es interrumpido abruptamente por la presencia de la península. La forma y orientación de las bahías de Mejillones y Moreno favorecen la retención de aguas de surgencia y la producción biológica reflejada en altas concentraciones de clorofila observadas, esto ocurre independiente de la temperatura y el transporte predominante en la cabeza y al sur de la península. La península interrumpe y desvía hacia el oeste la trayectoria de la corriente de chorro, la que varía estacionalmente de intensidad y puede alejarse más de 100 km desde la costa. Además, los resultados muestran la existencia de una latitud crítica (~22,8°S) o de transición en la que se produce un cambio marcado en la distribución latitudinal del transporte de Ekman.

Resumen es: Se realizaron mediciones de corrientes, oleaje y viento en el seno de Reloncavi, el golfo Corcovado, la zona exterior de Chiloe y en isla Italia, al inte...

We present geostrophic velocities obtained using hydrographic-altimeter data and direct measurements of currents from 11 cruises offshore of Baja California from January 2000 to July 2002. The study area was dominated by meanders and eddies in geostrophic balance. Two mechanisms of eddy generation were observed; the first associated with the geometry of the coastline, and the second a product of the cooling of the California Current and the California Undercurrent from the South. There were two persistent eddies observed during the study. The first eddy was offshore of Bahia Vizcaino and had an anticyclonic circulation. Situated in the southern region, the rotation of the second eddy was dependant on which current was first to enter the transition zone along the coast. Spring was a transition period characterized by the formation of meanders. The summer brought a period of eddy generation along the coast. Autumn and winter were marked by a separation of eddies from the coast and their subsequent drift towards the west. The phase velocity of the mesoscale eddies was in accordance with the theory of the linear propagation of a Rossby wave.

Nine years of data (1992–2000) were used to study the evolution of the sea–surface temperature (SST) over the eastern south Pacific. Our analysis shows that the variability in the SST on the interannual scale is attributed mainly to the equatorial El Nino-La Nina events while cooling, associated with the wind-Ekman drift, is an important component of the annual cycle. The anomalies at the interannual scale show up as a front that parallels the coast. At the seasonal scale, anomalous warming and cooling of coastal waters is strongly altered by the local effect of the wind-driven Ekman transport. This latter effect is especially significant along the Peruvian and Northern Chilean coast where wind induced upwelling and cooling is out-of-phase with other important annual forcings (i.e radiation and annual Kelvin waves). These local wind effects show up in the time-latitude plots as a thinning of the warm-water bands along the Peruvian coast (∼10°S y 17°S) and a thickening of the bands further south (∼18°S y 22°S). Three anomalous events that stand out clearly at the interannual scale are El Nino 92–93, La Nina 96 and El Nino 97–98. Their individual evolutions over time and along the coast are very different. Though the least intense of the three, the 92–93 event had the longest duration. The 96 event was the shortest in duration and its strongest anomaly occurred around the Peruvian coast, similar to the warm event of 92–93. The strongest event for the period occurred in 97–98, its warm anomaly showing strongly along the whole latitudinal extent of the study area. Contrary to what occurs at the seasonal scale, the increase on east/west Ekman transport on the interannual scale seems to be in phase with other relevant cooling and warming mechanisms. The interannual Ekman anomalous transports are at their maximum near the Peruvian-northern Chilean coast; however, they do not seem to alter the SST in a significant way. A similar situation has been described for sea-level data in the California Current System, i.e. interannual variability being associated mostly with variability of equatorial origin while seasonal variability is associated to both wind-forced local variability and remotely forced variability (J. Geophys. Res. 94 (1989) 3159)

Fourteen years of satellite images (1983–1996) are used to examine the variability of sea surface temperature (SST) in the Gulf of California. The study focussed on the semiannual, annual and interannual scales and on the average. On average, SST decreases from the mouth to the head and its variability increases. The annual scale is responsible for most of the temporal variability, which oscillates in phase with minor north-south variations. The northern gulf shows the formation of warm anticyclonic eddies during winter and cold cyclonic eddies during summer. The spring transition shows a cyclonic eddy closer to the mainland side of the gulf; the autumn transition shows a not well-defined anticyclonic eddy. The SST around the island region is always colder than the rest of the gulf. The lateral variability in the central and southern regions is associated with upwelling phenomena. The semiannual and annual amplitudes increase to the north by a factor of two with respect to the southern region. On the interannual scale, the 1988–1989 and 1992–1993 events reach all the gulf. Both events appear first in the south and island regions, and the signals are more intense at the islands than the rest of the gulf. This behavior has not been reported before. The 1985, 1987 and 1990 events show a "normal" evolution, i.e., the warm waters appear in the south and gradually progress into the gulf.

La recopilacion de informacion historica, tales como mediciones de corrientes, oleaje y viento no ha sido suficiente para describir la dinamica del seno Reloncavi. Sin embargo, a pesar de la informacion parcelada, las altas magnitudes de corrientes en las zonas de Chaica, Quillaipe y El Paso Nao nos permiten inducir que las corrientes baroclinicas modulan fuertemente la dinamica de la cuenca. Por otro lado, los vientos mostraron una alta variabilidad estacional y son modulados por la linea de costa, siendo estos en parte responsables de la circulacion y el oleaje superficial. Ademas, la circulacion superficial en los primeros 10 m esta fuertemente modulada por el ingreso de aguas dulce del estuario de Reloncavi. Ademas, la maxima amplitud del nivel del mar es de 7.64 m, con una amplitud promedio de 7.46 m, y donde la mayor parte de la variabilidad del nivel del mar esta asociada a la marea. Finalmente, para describir el comportamiento del oleaje se comparan el metodo empirico de Massel con el modelo numerico del Mike21. Resultando que el clima de ola estaria siendo modificado por la gran variabilidad espacial y temporal de la magnitud y direccion de las corrientes de la onda de marea.

Mediante el uso de 110 imagenes mensuales (1999-2008) del esfuerzo del viento proveniente del satelite Quikscat se analizo la zona donde divergen los vientos hacia el ecuador y hacia los polos. En las cercanias del borde oriental del Pacifico, tanto para el norte como para el sur, se estudio el desplazamiento de las zonas de divergencia de los vientos (DZD) mediante una serie de tiempo versus posicion. Mediante analisis estadistico se encontro que el DZD esta influenciado por senales de alta frecuencia (periodo de 3 meses), estacional (periodo de 12 meses) e interanual (periodos superior a dos anos) asociado al evento calido de El Nino. La senal mas robusta de la serie es la estacional, mostrando que el DZD de la region norte esta fuertemente acoplado a la region sur. Ademas, el DZD de la region norte muestra un mayor desplazamiento estacional, asociado posiblemente a la forma de la linea de costa ya que la region sur esta sometida a forzantes de origen polar.

Seasonal anomalies of salinity, phytoplankton chlorophyll a, and zooplankton volume off Baja California were examined from data obtained during 2001–2007. The analyses helped to identify a strong effect of physical processes on the pelagic ecosystem, diminishing near surface salinity and water column integrated phytoplankton biomass, and enhancing zooplankton volume. These changes are associated with an increase of the Pacific Decadal Oscillation (PDO) index, characterizing a warm phase of the index from summer 2002 to at least summer 2006. Negative chlorophyll a anomalies appear to respond to zooplankton grazing activity, with a possible top down effect during this period. Empirical orthogonal functions (EOFs) of Ekman drift reveal the seasonal and interannual patterns that describe the influence of upwelling zones, and there was a strong response to changes in the equatorward wind forcing from 2002 to 2006. The relationship between negative salinity anomalies and the two temporal EOF modes of Ekman drift was evident as a result of relaxation of coastal upwelling during this period. After 2006, the PDO index showed more neutral or negative values, defining the beginning of a cool phase, with positive nearsurface salinity anomalies off Baja California. Se estudiaron las anomalias estacionales de salinidad, clorofila-a y del volumen del zooplancton obtenidas de datos recolectados frente a Baja California de 2001–2007. A partir de su analisis se identifico el efecto de procesos fisicos en el ecosistema pelagico, al disminuir la salinidad cercana a la superficie y la biomasa del fitoplancton integrada en la columna de agua, con un aumento en el volumen del zooplancton. Estos cambios se asociaron con un incremento en el indice de la Oscilacion Decadal del Pacifico (ODP), que caracteriza a un periodo calido del indice a partir del verano de 2002 y al menos hasta el verano de 2006. Las anomalias negativas de clorofila-a parecen responder al pastoreo por el zooplancton, con un posible efecto de arriba hacia abajo durante este periodo. Las funciones empiricas ortogonales (FEOs) de la deriva de Ekman describieron el patron estacional e interanual producido en las zonas de afloramientos costeros de 2002 a 2006, como una respuesta a los cambios en el forzamiento del viento hacia el ecuador. Las semejanzas entre las anomalias negativas de salinidad y la variabilidad en los dos modos temporales de las FEOs fueron evidentes en la serie de tiempo, como resultado del relajamiento en los afloramientos costeros durante el periodo calido. Despues de 2006, el indice de la ODP tuvo mayormente valores neutros o negativos, lo que parece delimitar el inicio de un periodo frio con anomalias positivas de salinidad frente a Baja California.

[1] Satellite-derived data provide the temporal means and seasonal and nonseasonal variability of four physical and biological parameters off Oregon and Washington (41°-48.5°N). Eight years of data (1998-2005) are available for surface chlorophyll concentrations, sea surface temperature (SST), and sea surface height, while six years of data (2000-2005) are available for surface wind stress. Strong cross-shelf and alongshore variability is apparent in the temporal mean and seasonal climatology of all four variables. Two latitudinal regions are identified and separated at 44°-46°N, where the coastal ocean experiences a change in the direction of the mean alongshore wind stress, is influenced by topographic features, and has differing exposure to the Columbia River Plume. All these factors may play a part in defining the distinct regimes in the northern and southern regions. Nonseasonal signals account for ∼60-75% of the dynamical variables. An empirical orthogonal function analysis shows stronger intra-annual variability for alongshore wind, coastal SST, and surface chlorophyll, with stronger interannual variability for surface height. Interannual variability can be caused by distant forcing from equatorial and basin-scale changes in circulation, or by more localized changes in regional winds, all of which can be found in the time series. Correlations are mostly as expected for upwelling systems on intra-annual timescales. Correlations of the interannual timescales are complicated by residual quasi-annual signals created by changes in the timing and strength of the seasonal cycles. Examination of the interannual time series, however, provides a convincing picture of the covariability of chlorophyll, surface temperature, and surface height, with some evidence of regional wind forcing.