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Esta obra ofrece una síntesis de la información recogida en las series temporales de observaciones oceánicas del IEO en la región atlántica del norte de España iniciadas en 1943 con el registro mareográfico; muestra evidencias de cambios interanuales en la física, la química y la biología del océano en relación con los factores climáticos, y estima los impactos más probables del clima en el océano futuro. Este volumen continúa la serie de estudios de la influencia del cambio climático en el mar iniciada con el Cambio climático en el Mediterráneo español (Vargas Yánez et al., 2010). En este caso, el enfoque es multidisciplinar, empleando, por primera vez, series de observaciones recogidas de forma coordinada y simultánea. A lo largo de sus ochos capítulos, se analiza la variabilidad climática atmosférica reciente y su influencia sobre las condiciones oceanográficas de la región, especialmente en relación con la intensidad y frecuencia del afloramiento de aguas profundas que determina, en gran medida, el aporte estacional de nutrientes a la superficie y, por tanto, la producción biológica. Se describen las tendencias en el nivel del mar a partir de las medidas de los mareógrafos de la zona con una estimación de los niveles extremos esperados a largo plazo. Se realiza un análisis comparativo –entre Galicia y el Cantábrico– de la variabilidad en los nutrientes inorgánicos y se determinan los elementos limitantes de la producción primaria en cada zona. Finalmente, se analizan las variaciones en las comunidades de fitoplancton, picoplancton y zooplancton como indicadoras de cambios en el ecosistema pelágico, destacando las fluctuaciones en la biomasa y producción primaria, base de la red trófica pelágica de la región, y la presencia de medusas y salpas y su relación con el clima. This book presents a synthesis of the oceanic time-series observations of IEO in the Atlantic region of northern Spain. These series, starting in 1943 with tide-gauges, reveal evidence of interanual changes in physical, chemical and biological properties of the ocean that were related to climatic factors, allowing to estimate future impacts of climate on the ocean. The volume continues the series started with “Climate Change in the Spanish Mediterranean” (Vargas Yánez et al., 2010). In this case the study is multidisciplinary, including for the first time series obtained in coordinated and simultaneous observational programs. The eight chapters first analyse recent climatic variability and its influence on the regional oceanography, particularly in relation to the intensity and frequency of the deep-water upwelling that largely determines the seasonal inputs of nutrients and primary production in this region. Next, the main trends in sea level revealed by tidal gauges along with the estimates of expected extreme levels are described. The variability in inorganic nutrients and the identification of limiting elements for primary production were presented as a comparative analysis between Galicia (in the West) and the Mar Cantábrico (in the east). Finally, the variability in the composition of the plankton communities, including phytoplankton, picoplankton and zooplankton, is analysed as indicative of changes in the pelagic ecosystem. Particular attention is given to the fluctuations in primary biomass and production and to the presence of salps and jellyfish in relation to climate. Versión del editor

Esta obra ofrece una síntesis de la información recogida en las series temporales de observaciones oceánicas del IEO en la región atlántica del norte de España iniciadas en 1943 con el registro mareográfico; muestra evidencias de cambios interanuales en la física, la química y la biología del océano en relación con los factores climáticos, y estima los impactos más probables del clima en el océano futuro. Este volumen continúa la serie de estudios de la influencia del cambio climático en el mar iniciada con el Cambio climático en el Mediterráneo español (Vargas Yánez et al., 2010). En este caso, el enfoque es multidisciplinar, empleando, por primera vez, series de observaciones recogidas de forma coordinada y simultánea. A lo largo de sus ochos capítulos, se analiza la variabilidad climática atmosférica reciente y su influencia sobre las condiciones oceanográficas de la región, especialmente en relación con la intensidad y frecuencia del afloramiento de aguas profundas que determina, en gran medida, el aporte estacional de nutrientes a la superficie y, por tanto, la producción biológica. Se describen las tendencias en el nivel del mar a partir de las medidas de los mareógrafos de la zona con una estimación de los niveles extremos esperados a largo plazo. Se realiza un análisis comparativo –entre Galicia y el Cantábrico– de la variabilidad en los nutrientes inorgánicos y se determinan los elementos limitantes de la producción primaria en cada zona. Finalmente, se analizan las variaciones en las comunidades de fitoplancton, picoplancton y zooplancton como indicadoras de cambios en el ecosistema pelágico, destacando las fluctuaciones en la biomasa y producción primaria, base de la red trófica pelágica de la región, y la presencia de medusas y salpas y su relación con el clima., This book presents a synthesis of the oceanic time-series observations of IEO in the Atlantic region of northern Spain. These series, starting in 1943 with tide-gauges, reveal evidence of interanual changes in physical, chemical and biological properties of the ocean that were related to climatic factors, allowing to estimate future impacts of climate on the ocean. The volume continues the series started with “Climate Change in the Spanish Mediterranean” (Vargas Yánez et al., 2010). In this case the study is multidisciplinary, including for the first time series obtained in coordinated and simultaneous observational programs. The eight chapters first analyse recent climatic variability and its influence on the regional oceanography, particularly in relation to the intensity and frequency of the deep-water upwelling that largely determines the seasonal inputs of nutrients and primary production in this region. Next, the main trends in sea level revealed by tidal gauges along with the estimates of expected extreme levels are described. The variability in inorganic nutrients and the identification of limiting elements for primary production were presented as a comparative analysis between Galicia (in the West) and the Mar Cantábrico (in the east). Finally, the variability in the composition of the plankton communities, including phytoplankton, picoplankton and zooplankton, is analysed as indicative of changes in the pelagic ecosystem. Particular attention is given to the fluctuations in primary biomass and production and to the presence of salps and jellyfish in relation to climate.

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In the late 80's, the Spanish Institute of Oceanography (IEO) began some ambitious programs of monitoring around the Iberian Peninsula. The coastal observing system core structure was the Radiales program, a series of transects nearby most coastal IEO laboratories where a minimum set of hydrographical, chemical and biological parameters is sampled monthly. The sections are designed to be completed in one-day journeys so the system is supported by quite small vessels, mainly covering the continental shelf with the noteworthy exception of the Santander Section, where the proximity of the shelf-break allows sampling deep waters monthly. During the last 20 years the program has supported many specific scientific research projects and has created a detailed description of seasonal to interannual variability in the coastal ecosystem that serves as a baseline to explore long-term changes or trends...

This paper presents an analysis of data related to the hydrology and currents in the Gulf of ártabro -a region located in the north-western corner of the Galician coast- that were collected from May to September, 1996. The work has been divided into two broad sections; the first of which examines the data collected during two different oceanographic surveys carried out in May and September, in an area covering some 30 ˟ 35 nautical miles, while the second section analyzes the time series of data collected by means of two lines moored outside the area sampled. The first dataset was subjected to a quasi-synoptic analysis (the data collection took place within a timeframe of roughly 5 days), of the distribution of the water masses in the region and their dynamics, based on geostrophic calculations. This is the first comprehensive description of the oceanography in this region. Moreover, since the information comes from two different time periods -one at the beginning and the other in the middle of the upwelling season- it was possible to investigate the variability of the circulation patterns. The most important differences were observed in the upper-layer circulation, ranging from a situation in which the Poleward Current (May, 1996) was still distinguishable, to another one which led to the identification of the basic characteristics of seasonal upwelling episodes in the eastern contours of the subtropical gyres of the large ocean basins. In September, 1996, the upwelling was in a stage of (almost) maximum activity, and hydrological sampling enabled us to identify a structure with filament features emanating from Cape San Adrián (the most rugged topography of the coast in this area), towards the open sea. Minor changes were also observed in the circulation of the vein of Mediterranean water. With the time series, it was possible to examine the variability of the dynamics on different time scales. The most important was found to be the one associated with the tides that exhibit an intense baroclinic mode contribution, with large internal fluctuations and, more interestingly, a marked increase in the intensity of the bottom currents. Detailed analysis of the data collected would suggest that this increase is a consequence of the total reflection of the energy transported by the internal tide, as it hits the continental slope with its supercritical topographic inclination. The recordings of the currents also helped to indentify a less intense inertial wave activity, associated with the passage of strong atmospheric fronts and the transfer of inertial energy contained in the wind field. The most important inertial episodes coincide with pronounced changes in the sub-inertial velocity field, which has led to the hypothesis that the two phenomena might be related. At a lower frequency, the near-surface currents recorded would appear to indicate the regular formation of filaments in the vicinity of Cape San Adrián, insofar as the deepest currents show large fluctuations (tens, or even up to a hundred, meters), in the depth at which the core of the Mediterranean water flows. A curious relationship was noted between the alternation of energy episodes in the near-surface and the deep layers. This relationship has not been studied in this paper. La presente memoria analiza un conjunto de datos hidrológicos y de corrientes recogidos entre mayo y septiembre de 1996 en el denominado golfo ártabro, región situada en la esquina noroccidental del litoral gallego. El trabajo se ha separado en dos grandes bloques, el primero trata los datos recogidos durante las campañas oceanográficas llevadas a cabo en mayo y septiembre en un área de unas 30 ˟ 35 millas náuticas; el segundo analiza las series temporales de datos recogidos por dos líneas de fondeo colocadas en la parte exterior del área muestreada. Con el primero de los conjuntos de datos se ha realizado un análisis casi-sinóptico (los datos fueron recogidos en un lapso de tiempo de, aproximadamente, 5 días) de la distribución de las masas de agua en la región y de su dinámica basada en cálculos geostróficos. Es la primera descripción exhaustiva de la oceanografía de esta región. Además, el hecho de disponer de información en dos épocas diferentes, una al principio de la estación de afloramiento y otra en pleno afloramiento, ha permitido investigar la variabilidad en los patrones de circulación. Las mayores diferencias se observan en la circulación de la capa superior, cambiando desde una situación donde aún es identificable la Poleward Current (mayo, 1996) hasta otra donde se identifican las características esenciales de los afloramientos estacionales en los contornos orientales de los giros subtropicales de las grandes cuencas oceánicas. En septiembre de 1996, el afloramiento estaba en una fase de (casi) máxima actividad y el muestreo hidrológico permitió identificar una estructura con características de filamento emanando desde el cabo San Adrián (la irregularidad topográfica más notable de la costa en la zona) hacia alta mar. También se observaron cambios menores en la circulación de la vena de agua mediterránea. Las series temporales permitieron investigar la variabilidad de la dinámica a distintas escalas temporales. La más importante es la asociada a las mareas, las cuales muestran una intensa contribución baroclina con importantes oscilaciones internas y -más interesante- con una notable intensificación de las corrientes en el fondo. Un análisis detallado de los datos recogidos sugiere que esta intensificación es consecuencia de la reflexión total de la energía transportada por la marea interna al incidir sobre un talud continental con pendiente topográfica supercrítica. Los registros de corrientes también han identificado una actividad de ondas inerciales de menor intensidad vinculadas al paso de frentes atmosféricos intensos y a la transferencia de energía de inercia contenida en el campo de vientos. Los episodios inerciales más importantes coinciden con cambios notables en el campo de velocidad subinercial por lo que se postula una relación entre ambos fenómenos. A más baja frecuencia, los registros de corriente más superficiales sugieren la formación regular de filamentos en las inmediaciones del cabo San Adrián en tanto que los más profundos indican importantes oscilaciones (de decenas a, tal vez, un centenar de metros) en la profundidad a la cual fluye el núcleo de agua mediterránea. Se apunta una relación curiosa entre la alternancia de episodios energéticos en las capas superficial y profunda, relación que no ha sido estudiada en esta memoria. Instituto Español de Oceanografía

This paper presents an analysis of data related to the hydrology and currents in the Gulf of ártabro -a region located in the north-western corner of the Galician coast- that were collected from May to September, 1996. The work has been divided into two broad sections; the first of which examines the data collected during two different oceanographic surveys carried out in May and September, in an area covering some 30 ˟ 35 nautical miles, while the second section analyzes the time series of data collected by means of two lines moored outside the area sampled. The first dataset was subjected to a quasi-synoptic analysis (the data collection took place within a timeframe of roughly 5 days), of the distribution of the water masses in the region and their dynamics, based on geostrophic calculations. This is the first comprehensive description of the oceanography in this region. Moreover, since the information comes from two different time periods -one at the beginning and the other in the middle of the upwelling season- it was possible to investigate the variability of the circulation patterns. The most important differences were observed in the upper-layer circulation, ranging from a situation in which the Poleward Current (May, 1996) was still distinguishable, to another one which led to the identification of the basic characteristics of seasonal upwelling episodes in the eastern contours of the subtropical gyres of the large ocean basins. In September, 1996, the upwelling was in a stage of (almost) maximum activity, and hydrological sampling enabled us to identify a structure with filament features emanating from Cape San Adrián (the most rugged topography of the coast in this area), towards the open sea. Minor changes were also observed in the circulation of the vein of Mediterranean water. With the time series, it was possible to examine the variability of the dynamics on different time scales. The most important was found to be the one associated with the tides that exhibit an intense baroclinic mode contribution, with large internal fluctuations and, more interestingly, a marked increase in the intensity of the bottom currents. Detailed analysis of the data collected would suggest that this increase is a consequence of the total reflection of the energy transported by the internal tide, as it hits the continental slope with its supercritical topographic inclination. The recordings of the currents also helped to indentify a less intense inertial wave activity, associated with the passage of strong atmospheric fronts and the transfer of inertial energy contained in the wind field. The most important inertial episodes coincide with pronounced changes in the sub-inertial velocity field, which has led to the hypothesis that the two phenomena might be related. At a lower frequency, the near-surface currents recorded would appear to indicate the regular formation of filaments in the vicinity of Cape San Adrián, insofar as the deepest currents show large fluctuations (tens, or even up to a hundred, meters), in the depth at which the core of the Mediterranean water flows. A curious relationship was noted between the alternation of energy episodes in the near-surface and the deep layers. This relationship has not been studied in this paper., La presente memoria analiza un conjunto de datos hidrológicos y de corrientes recogidos entre mayo y septiembre de 1996 en el denominado golfo ártabro, región situada en la esquina noroccidental del litoral gallego. El trabajo se ha separado en dos grandes bloques, el primero trata los datos recogidos durante las campañas oceanográficas llevadas a cabo en mayo y septiembre en un área de unas 30 ˟ 35 millas náuticas; el segundo analiza las series temporales de datos recogidos por dos líneas de fondeo colocadas en la parte exterior del área muestreada. Con el primero de los conjuntos de datos se ha realizado un análisis casi-sinóptico (los datos fueron recogidos en un lapso de tiempo de, aproximadamente, 5 días) de la distribución de las masas de agua en la región y de su dinámica basada en cálculos geostróficos. Es la primera descripción exhaustiva de la oceanografía de esta región. Además, el hecho de disponer de información en dos épocas diferentes, una al principio de la estación de afloramiento y otra en pleno afloramiento, ha permitido investigar la variabilidad en los patrones de circulación. Las mayores diferencias se observan en la circulación de la capa superior, cambiando desde una situación donde aún es identificable la Poleward Current (mayo, 1996) hasta otra donde se identifican las características esenciales de los afloramientos estacionales en los contornos orientales de los giros subtropicales de las grandes cuencas oceánicas. En septiembre de 1996, el afloramiento estaba en una fase de (casi) máxima actividad y el muestreo hidrológico permitió identificar una estructura con características de filamento emanando desde el cabo San Adrián (la irregularidad topográfica más notable de la costa en la zona) hacia alta mar. También se observaron cambios menores en la circulación de la vena de agua mediterránea. Las series temporales permitieron investigar la variabilidad de la dinámica a distintas escalas temporales. La más importante es la asociada a las mareas, las cuales muestran una intensa contribución baroclina con importantes oscilaciones internas y -más interesante- con una notable intensificación de las corrientes en el fondo. Un análisis detallado de los datos recogidos sugiere que esta intensificación es consecuencia de la reflexión total de la energía transportada por la marea interna al incidir sobre un talud continental con pendiente topográfica supercrítica. Los registros de corrientes también han identificado una actividad de ondas inerciales de menor intensidad vinculadas al paso de frentes atmosféricos intensos y a la transferencia de energía de inercia contenida en el campo de vientos. Los episodios inerciales más importantes coinciden con cambios notables en el campo de velocidad subinercial por lo que se postula una relación entre ambos fenómenos. A más baja frecuencia, los registros de corriente más superficiales sugieren la formación regular de filamentos en las inmediaciones del cabo San Adrián en tanto que los más profundos indican importantes oscilaciones (de decenas a, tal vez, un centenar de metros) en la profundidad a la cual fluye el núcleo de agua mediterránea. Se apunta una relación curiosa entre la alternancia de episodios energéticos en las capas superficial y profunda, relación que no ha sido estudiada en esta memoria., Instituto Español de Oceanografía

Based on recently gathered swath-bathymetry, high- to ultra-high-resolution seismic, and underwater camera data, along with dredging and coring samples, this paper examines the relationship between sea-floor features and the nature of hydrocarbon-enriched fluid and gas leaks from degassing of deeply buried sediments along the continental margin of the Gulf of Cadiz (eastern Central Atlantic). A classification into three main groups is proposed on the basis of the morphology and nature of deposits: (1) mud volcanoes, (2) methane-derived authigenic carbonates (MDAC) mounds, and (3) crater-like pockmarks. Mud volcanoes are, topographically, cone-shaped sea-floor edifices, built up from catastrophic mud and fluid degassing, intercalated with periods of inactivity. So far more than 25 mud volcanoes have been discovered in the Gulf of Cadiz, named in memory of deceased colleagues (e.g., Ginsburg and Baraza), or researchers’ birth places (e.g. Faro, Cibeles, Almazan, San Petersburgh, Yuma, Rabat, Bonjardim, Coruna, Gades). These structures range from 800 to 2500 m in diameter and tower 150–300 m above the seabed. The volcanoes consistently feature a well-defined outer ring or circular terrace and an inner dome. All mud volcanoes are built up of episodes of mud-breccia flows, intercalated with deep-current deposits, with evident indications of gas saturation: degassing structures, a strong H2S smell, and chemosynthetic fauna (such as Pogonophora sp. tube worms and Calyptogena sp.). Commonly observed carbonate crusts and slabs overlying some mud volcanoes are thought to have been formed by slow, diffuse venting during periods of inactivity or slower rates of fluid venting following the ejection of mud. A “fermentation” process, the result of microbial-mediated oxidation of hydrocarbon-enriched fluids, seems to play an important role in the growth of large deep-water carbonate mounds and chimneys during periods of low methane-seep fluid pressure. More than 400 crater-like pockmarks, a common sea-floor feature in the TASYO field, have been observed. Their seabed diameter ranges from 500 to 3000 m, with steep slopes ranging from 12° to 35°. According to their internal structure, pockmarks can be grouped into: (1) pockmarks with low central mounds and (2) crater-like pockmarks, apparently collapse structures lacking central mounds, with a flat to slightly undulating sea bottom surrounded by steep slopes (up to 25°).

The distribution of the water masses and their circulation in the eastern North Atlantic region off the northern half of the west coast of the Iberian Peninsula are analysed here based on CTD measurements made in May 1993 during the “MORENA 1” cruise. The upper layers of the ocean, down to about 100 m, showed a typical spring, non-upwelling situation with a very shallow seasonal thermocline overlying thicker remnants of the mixed layer from the previous winter. Below, Central Water extended between a subsurface salinity maximum near depths of 100–140 m and a salinity minimum at about 500 m. Using quantitative water mass analysis and geostrophic calculations, a poleward surface current reaching down to depths of 250 m and transporting relatively warm and saline Eastern North Atlantic Central Water (ENACW) of subtropical origin was characterised, centred at a few tens of km offshore the shelf break, therefore indicating that the northward current identified previously in this region during winter (the Portugal Coastal Countercurrent) continues to be present through the spring season. A large-scale transition zone, the Galicia Front, was found in the northwest area of the study region, reaching from the surface layers down to the depths of the Mediterranean Water. To the north of this front, relatively fresh Central Water of Western Atlantic origin replaced the subtropical branch of ENACW. At the deeper Central Water levels, ENACW from subpolar North Atlantic origin was present through the whole study region. The influence of the upper and lower cores of Mediterranean Water was present, centred at levels of 800 and 1100 m, as indicated by their characteristic thermohaline maxima. The deduced flow of Mediterranean Water was towards the north in the whole study region, in clear relation with the Portugal Slope Undercurrent, and showed some tendency to branch towards the west through the gap between the Vigo Seamount and the Galicia Bank. The Mediterranean upper core occupied a relatively thin layer, O (100 m), and underwent a strong dilution of about 45% from the south to the north of the study region; the lower core spread over a larger depth range, of about 400–500 m, and decayed only by about 20% through the region. Below the Mediterranean Water, the influence of North Atlantic Deep Water spread through the study region, and an intermediate layer of Labrador Sea Water was also present, particularly offshore in the northwest zone.

RESUMEN: Con vistas a conocer las condiciones hidrográficas y los procesos biológicos asociados en el canal de Ibiza, durante los meses de noviembre de 1990 y marzo de 1991, se llevaron a cabo dos campañas oceanográficas. A su vez, durante el período comprendido entre el 15 de noviembre de 1990 y el 24 de julio de 1991 se midieron corrientes marinas en el centro del canal en seis niveles de muestreo. La presencia de sistemas frontales superficiales, la circulación de las distintas masas de agua, la variabilidad estacional y los flujos netos a través del canal fueron estudiados y calculados en ambas campañas. En marzo, registramos la presencia de agua de invierno (A1) formando pequeños núcleos por encima de los 100 m de profundidad. Las corrientes geostróficas calculadas están de acuerdo con las velocidades medias obtenidas con los correntímetros más superficiales. En el análisis de las corrientes en baja frecuencia se ha podido observar, a lo largo de los meses, el paso de una situación preferentemente baroclina a comienzos del año 1991 a una situación barotrópica a partir de abril del mismo año., Water masses and associated dynamics in the Ibiza Channel, November 1990 and March 1991. In order to study the hydrographic conditions and the associated biological processes in the Ibiza Channel, two oceanographic surveys were carried out in November 1990 and March 1991. In addition, a mooring equipped with six current meters was deployed close to the sill of the channel from November 1990 to July 1991. Surface frontal systems, water mass circulation, seasonal variation and net fluxes were studied and calculated in both surveys. Small cores of Winter Intermediate Water (WIW) were recorded above the 100 m depth in March. Calculated geostrophic currents were in agreement with data recorded by the uppermost current meters. Low frequency analysis indicated a change from baroclinic conditions at the beginning of 1991 to barotropic conditions in March 1991, Sí

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