Foreword : Planet Ocean

Foreword of special volume: Planet Ocean. Scientia Marina 80(Suppl.1) 2016.-- 2 pagesThe Institute of Fisheries Research (Instituto de Investigaciones Pesqueras, IIP) was created in 1951 as a biology research centre belonging to the Spanish National Research Council (Consejo Superior de Investigaciones Científicas, CSIC). Its headquarters were in Barcelona but it had coastal laboratories in Blanes, Castelló, Cadiz and Vigo. The IIP split into five centres (Barcelona, Castelló, Cádiz and Vigo in 1979, and Blanes in 1985), and in 1987 the Barcelona centre became the Institute of Marine Sciences (Institut de Ciències del Mar, ICM). [...]Peer Reviewe

La memòria oceànica del clima: El sistema circulatori d'un planeta viu

A principis del segle XVI Leonardo da Vinci comparava els corrents oceànics amb el fl ux de sang d’un cos humà. Actualment disposem d’informació sufi cient per a explorar la idea que la Terra té un sistema circulatori responsable de capturar, transformar i distribuir l’energia solar. El paper dels oceans com a reguladors del clima és extraordinari, realment condicionen el present i el futur del planeta

Vertical alignment of the Gulf Stream

10 pages, 10 figuresA historical set of expendable bathythermograph (XBT) and Pegasus sections across the Gulf Stream in natural coordinates is examined to investigate the isopycnic structure of the current off Cape Hatteras. In isopycnic-natural coordinates, the axis of the Stream remains vertically aligned, in contrast to its well-known offshore tilting when plotted as a function of depth. These results are confirmed using the geostrophic velocities obtained from a synthetic temperature field for the Gulf Stream. We prove that a baroclinic current aligned with density cannot be aligned with depth, and vice versa, and we show that the density alignment of the Gulf Stream results from the distortion of the density field and has negligible dependence on the choice of reference level. The invariable character of intense geophysical jets is supported through analogous representations for the upper level atmospheric jet stream in isentropic coordinates. These show that the atmospheric jet, when plotted on to a section normal to the direction of its maximum velocity core, is vertically aligned with potential temperature. Copyright © Blackwell Munksgaard, 2005Part of this work was written while JLP was at the University of Wisconsin-Madison with funding from the Secretar´ıa de Estado de Educación y Universidades of the Spanish Government. This work has also been partly funded by the European Union through project OASIS (EVK3-CT-2002-00073-OASIS)Peer Reviewe

Potential changes in larval dispersal and alongshore connectivity on the central Chilean coast due to an altered wind climate

14 pages, 8 figuresClimate change is likely to result in significant alterations in the atmospheric and oceanic circulation, which may, as a result, affect species that depend on an ocean-driven nutrient supply and particularly those that possess a dispersal phase in their life history. In this paper we investigate the potential changes in larval dispersal and connectivity of marine populations on the Chilean coast due to altered wind forcing consistent with a future climate change scenario. Numerical ocean simulations forced by modeled present-day and future winds under the Intergovernmental Panel on Climate Change A2 scenario are used to investigate the potential changes in nearshore circulation. Off-line particle-tracking simulations are then analyzed to determine resulting changes in larval dispersal and connectivity under each scenario as a function of pelagic larval duration and for two different possible larval behaviors: passive and vertical migration. It is found that the projected future winds drive an intensification of the upwelling circulation, which results in a relative annual mean surface cooling of 1°C over much of the domain, an increase in the strength of the poleward undercurrent, and a more energetic mesoscale eddy field. Neutrally buoyant larvae are inferred to have low rates of settlement under present conditions and are more strongly disadvantaged under the simulated future conditions than larvae with vertically migrating behavior. Larvae that posses an ability to sink out of the surface Ekman layer are found to have higher rates of settlement under present conditions and are, in fact, favored slightly in the A2 scenario for pelagic larval durations longer than 2 days. This behavior-dependent response to future conditions may potentially drive a reorganization of coastal communitiesSupport for this study was provided through the Laboratorio Internacional en Cambio Global (LINCGlobal) and CMA through Fondecyt grant 1100646. We thank Rene Garreaud from the Universidad de Chile for providing the output from the PRECIS model simulations and for his useful comments. The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Center. S.A.N. acknowledges support by FONDAP-FONDECYT grant 15001–0001 to CASEBPeer Reviewe

Relaciones analíticas entre la salinidad y la temperatura para aguas de la termoclina superior en el margen oriental del giro subtropical del Atlántico Norte

[EN] We study the dependence of salinity on temperature in two by two degrees latitude-longitude boxes, for surface and upper-thermocline waters of the eastern North Atlantic subtropical gyre. The initial data set, from historical databases as well as from recent hydrographic cruises in the region, is carefully scrutinized to reject dubious measurements. We search for polynomial relations of variable degree between salinity and temperature, the optimal fit is selected as the polynomial with the lowest degree that satisfies several statistical criteria. An independent hydrographic cruise is used to confirm that the method performs substantially better than estimates from climatological data, and leads to relatively low deviations in geopotential anomaly and other derived quantities. An error propagation analysis using the Monte Carlo method shows equally good results[ES] En este estudio caracterizamos la dependencia de la salinidad con la temperatura en cajas de dos por dos grados de latitud y longitud para aguas superficiales y de la termoclina superior en el margen oriental del giro subtropical del Atlántico Norte. El conjunto inicial de datos, procedente de bases de datos históricos, así como los procedentes de recientes campañas hidrográficas en la región, son cuidadosamente analizados para eliminar las medidas de calidad dudosa. Se analizan varias relaciones polinómicas de grado variable para la salinidad en función de la temperatura, eligiendo como ajuste óptimo aquel polinomio de menor grado que satisface diversos criterios estadísticos. Se utiliza una campaña hidrográfica independiente para confirmar que el método da resultados substancialmente mejores que estimaciones a partir de datos climatológicos, y que produce desviaciones relativamente bajas en la anomalía geopotencial y en otras magnitudes derivadas. Un análisis de la propagación del error usando el Método de Montecarlo muestra resultados igualmente buenosWe are grateful to the Institut für Meereskunde and IFREMER for making their data sets available. The Spanish cruises that gathered some of the data analyzed here were carried out through projects from the Spanish government (program CYTMAR) and the European Union (program MAST). This work has been carried out with the support of the Spanish Government through project FRENTES (AMB95-0731) and the European Union through projects CANIGO (MAS3-CT96-0060) and OASIS (EVK3-CT-2002-00073). Part of this work was written while JLP was at the University of Wisconsin-Madison with funding from the Secretaría de Estado de Educación y Universidades of the Spanish governmentPeer reviewe

Geostrophic and ageostrophic circulation of a shallow anticyclonic eddy off Cape Bojador

European Geosciences Union General Assembly 2014 (EGU2014), 27 april - 2 may 2014, Vienna, Austria.-- 1 pageA shallow mesoscale anticyclonic eddy, observed south of the Canary Islands with satellite altimetry, has been intensively studied with multi-parametric sampling. Hydrographic data from a CTD installed on an undulating Nushuttle platform reveal the presence of a mesoscale anticyclonic eddy of 125 km diameter. The difference in sea level anomaly (SLA) between the interior and the edge of the eddy, as determined from altimetry, is +-15 cm, which compares well with the maximum dynamic height differences as inferred using a very shallow reference level (130 m). Further, the associated surface geostrophic velocities, of about 35 cm/s in the northeast and southwest edges of the eddy, are in good agreement with direct velocity measurements from the ship. Deep rosette-CTD casts (1500 m depth) confirm that the structure is a shallow eddy extending no deeper than 250 m before the fusion with another anticyclone. The SLA-tendency (temporal rate of change of sea surface height) indicates a clear northwestward migration during the two first weeks of November 2008. Applying an eddy SSH based tracker, the eddy¿s velocity propagation is estimated as 4 km/day. Use of the QG-Omega equation diagnoses maximum downward/upward velocities of about +- 2 m/day. The instability of the Canary coastal jet appears to be the mechanism responsible for the generation of the shallow anticyclonic eddyPeer Reviewe

Cambios interdecadales en estratificación y doble difusión en la sección transatlántica 7.5°N

Special volume: Advances in Spanish physical oceanography. Scientia Marina 76(Suppl.1) 2012.-- 19 pages, 15 figures, 3 tables[EN] We use three transatlantic cruises (1957, 1993 and 2010) along 7.5°N to analyse inter-decadal variations of the neutral buoyancy frequency (with neutral density replacing potential density) and Turner angle. We also use Argo data from the 2003-2011 period to show that, within central and intermediate waters, the changes between the three sections are slightly greater than the seasonal and inter-annual variations, so they may be interpreted as actual inter-decadal variations. The results point to a generalized sinking of isoneutrals between 1957 and 2010, with maximum zonally-averaged values of about 100 m in the central and upper deep layers. They also reveal the occurrence of substantial changes in the intermediate and neighbouring water strata, with differential vertical sinking of isoneutrals and the transformation of their thermohaline characteristics. The neutral buoyancy frequency increased in the lower central and upper intermediate layers and decreased in the lower intermediate and upper deep layers. The distributions of Turner angle highlight a predominance of salt-fingering in the North Atlantic, except for a gravitationally doubly-stable layer located immediately below the intermediate water core; this stable layer thinned substantially between 1957 and 2010 because of the sinking of the lower intermediate isoneutrals acting together with actual water transformations from Antarctic Intermediate Waters into North Atlantic Deep Waters. We conclude that a significant portion of the water column underwent both increased vertical stratification and enhanced salt-fingering, two mechanisms with opposite effects on the effective vertical diffusion[ES] Usamos tres campañas transatlánticas (1957, 1993 y 2010) a lo largo de 7.5°N para analizar las variaciones interdecadales de la frecuencia de flotabilidad neutra (con la densidad neutra reemplazando a la densidad potencial) y el ángulo de Turner. También utilizamos datos Argo del periodo 2003-2011 para mostrar que, en las aguas centrales e intermedias, los cambios entre las tres secciones son algo superiores a las variaciones estacionales o interanuales, de modo que pueden interpretarse como cambios interdecadales. Los resultados indican un hundimiento generalizado de las isoneutras entre 1957 y 2010, con valores máximos promediados zonalmente de unos 100 m en las aguas centrales y profundas superiores. También revelan la existencia de cambios substanciales en las aguas intermedias y los estratos vecinos, con desplazamientos verticales diferenciales de las distintas isoneutras, y la transformación de sus características termohalinas. La frecuencia de flotabilidad neutra aumentó en las capas centrales inferiores e intermedias superiores y disminuyó en las capas intermedias inferiores y profundas superiores. Las distribuciones del ángulo de Turner enfatizan la predominancia de dedos de sal en el Atlántico Norte, excepto en una capa gravitacionalmente estable ubicada inmediatamente por debajo del núcleo de aguas intermedias; esta capa estable se estrechó entre 1957 y 2010 debido al efecto conjunto del hundimiento de las isoneutrasintermedias más profundas y la transformación de las Aguas Antárticas Intermedias en Aguas Noratlánticas Profundas. Concluimos que una porción significativa de la columna de agua experimentó tanto un aumento en la estratificación vertical como un incremento en el régimen de dedos de sal, dos mecanismos con efectos opuestos en la difusión vertical efectivaThis research was supported by the Spanish National R&D Plan, in the framework of projects MOC2 (CTM2008-06438-C02-01) and TIC-MOC (CTM2011-28867). The authors are grateful to the BIO Hespérides scientists, technicians and crew for making it possible to gather the 2010 data setPeer reviewe

Seasonal circulation over the Catalan inner-shelf (northwest Mediterranean Sea)

This study characterizes the seasonal cycle of the Catalan inner-shelf circulation using observations and complementary numerical results. The relation between seasonal circulation and forcing mechanisms is explored through the depth-averaged momentum balance, for the period between May 2010 and April 2011, when velocity observations were partially available. The monthly-mean along-shelf flow is mainly controlled by the along-shelf pressure gradient and by surface and bottom stresses. During summer, fall, and winter, the along-shelf momentum balance is dominated by the barotropic pressure gradient and local winds. During spring, both wind stress and pressure gradient act in the same direction and are compensated by bottom stress. In the cross-shelf direction the dominant forces are in geostrophic balance, consistent with dynamic altimetry data. Key Points A hydrodynamic model is implemented for the first time in Catalan inner-shelf. Frictional and pressure gradient are revealed as the main forcing mechanisms A clear seasonal pattern is found in the current velocity.Peer ReviewedPostprint (published version

CO2-driven compromises to marine life along the Chilean coast

CO2-driven compromises to marine life were examined along the Chilean sector of the Humboldt Current System, a particularly vulnerable hypoxic and upwelling area, applying the Respiration index (RI = log10 pO2/pCO2) and the pH-dependent aragonite saturation (Ω) to delineate the water masses where aerobic and calcifying organisms are stressed. There was a remarkable negative relationship between oxygen concentration and pH or pCO2 in the studied area, with the subsurface hypoxic Equatorial Subsurface Waters extending from 100 m to about 300 m depth and supporting elevated pCO2 values. The RI reached a minimum at about 200 m depth and decreased towards the Equator. Increased pCO2 in the hypoxic water layer reduced the RI values by as much as 0.59 RI units, with the upper water layer that presents conditions suitable for aerobic life (RI>0.7) declining by half between 42° S and 28° S. The intermediate waters hardly reached those stations closer to the equator so that the increased pCO2 lowered pH and the saturation of aragonite. A significant fraction of the water column along the Chilean sector of the Humboldt Current System suffers from CO2-driven compromises to biota, including waters corrosive to calcifying organisms, stress to aerobic organisms or both. The habitat free of CO2-driven stresses was restricted to the upper mixed layer and to small water parcels at about 1000 m depth. pCO2 acts as a hinge connecting respiratory and calcification challenges expected to increase in the future, resulting in a spread of the challenges to aerobic organisms. © Author(s) 2008.This is a contribution to the Humboldt-2009 project, funded by the Spanish Ministry of Science and Innovation (ref. CTM2009-02497-E/MA) and was also supported by funding from the LINCGlobal (PUC-CSIC).Peer Reviewe

Cut-off low systems over Iraq: Contribution to annual precipitation and synoptic analysis of extreme events

We combine daily in situ precipitation data with meteorological reanalysis data in order to explore the contribution of cut-off low systems to the seasonal and interannual rainfall variations over Baghdad from 2005 to 2016. During these 12 years (average rainfall of 131 ± 67 mm/year), 38 rainy cut-off lows brought 43% of the total precipitation, with extreme inter-annual variations. Indeed, precipitation associated with autumn cut-off lows was the principal factor that turned an arid into a wet year: during the three most arid years cut-off lows contributed about 25% of the average rainfall (10 out of 40 mm/year) while during the three wettest years they contributed near 67% (171 out of 254 mm/year). The extreme-rain cut-off low systems displayed analogous synoptic characteristics: upper-atmosphere divergence, upwards vertical motions in the middle atmosphere, and lower-atmosphere winds into central Iraq at times when the surface Red Sea and Persian Gulf waters were warmer than the surface air. During those days previous to an extreme event, the surface waters cooled substantially and the amount of precipitable water increased largely, suggesting high latent heat transfer. In order to characterize those conditions that favour rainfall, we focus on the November 18–20, 2013 cut-off low system, which led to the largest flooding and wettest year in Baghdad between 2005 and 2016. The distribution of properties in the middle (500 hPa) and upper (250 hPa) troposphere shows that the region was affected by intense horizontal divergence and upwards motions, coinciding with a surface low over the Arabian Peninsula that caused intense northwards winds over the Persian Gulf and brought substantial moisture to central Iraq. The analysis of several stability indexes indicates that convective instability played a secondary role during the episode.Peer ReviewedPostprint (author's final draft