Memoria de las actividades de validación euleriana y lagrangiana

85 pages.-- Radares de alta frecuencia en el observatorio RAIA, Actividad 2: Gestión y Validación de la Información, Entregable 2.10 - Memoria de las actividades de validación euleriana y lagrangianaLa obtención de medidas precisas de las corrientes marinas constituye un desafío debido a su alta variabilidad espacio-temporal, resultado de la influencia de diversos forzamientos: las mareas, la descarga fluvial de agua dulce, el viento, etc. Las medidas de corrientes proporcionadas por instrumentos convencionales tales como correntímetros, ADCPs o boyas de deriva, aunque útiles, presentan ciertas limitaciones en términos de resolución espacial y su precisión está sujeta al estado dinámico del mar. Por ello, en las últimas décadas se han realizado notables esfuerzos para desarrollar técnicas alternativas tales como la detección remota de mapas 2D de corrientes superficiales en regiones costeras con ayuda de radares HF (High Frequency o de alta frecuencia)Este documento ha sido cofinanciado por el Fondo Europeo de Desarrollo Regional FEDER a través del Programa Interreg V-A España-Portugal (POCTEP) 2014-2020N

Cambios temporales en los transportes y la distribución de las masas de agua a lo largo de la sección 20º W de CAIBOX (Atlántico NE)

24 páginas, 3 tablas, 7 figuras[EN] The CAIBOX cruise was conducted from 25 July to 14 August 2009. Three consecutive transects (zonal, meridional, and transverse) formed a closed box to the west of the Strait of Gibraltar. This study aimed to analyze the thermohaline properties, volume transports, and water mass distributions (percentages) along the meridional section (30–41.5º N, 20º W). We identified the main geostrophic current (Azores Current) and its associated volume transport and interannual changes. Data from previous cruises (AZORES I, A16N, CLIVAR, OACES, and CHAOS) with similar tracks were employed to compare with the CAIBOX meridional section. All but one (CHAOS) were summer cruises. We estimated a mean transport for the Azores Current at 20º W of 9.3 ± 2.6 Sv. There appears to be an inverse relation between the position of this current and its associated transport, with relatively high (low) transports when the current is located roughly south (north) of 35º N. Regarding water masses, an increase of 14.4% was found for Mediterranean Water compared with the 1993, 1998, and 2003 cruises; however, Labrador Sea Water decreased its contribution and southward spreading between 1998 and 2009[ES] Entre el 25 de julio y el 14 de agosto de 2009 se llevó a cabo la campaña CAIBOX, que constó de tres transectos consecutivos (zonal, occidental y transversal) conformando una caja cerrada al oeste del estrecho de Gibraltar. El objetivo principal del presente trabajo fue el estudio de las propiedades termohalinas, los transportes (en términos de volumen) y la distribución de las masas de agua (en porcentajes) a lo largo de la sección occidental (30–41.5º N, 20º W). Se identificó la corriente geostrófica principal (Corriente de las Azores), el transporte asociado a ella y sus cambios interanuales. Adicionalmente se consideraron los datos de cinco campañas anteriores (AZORES I, A16N, CLIVAR, OACES y CHAOS) con secciones similares a las de la campaña CAIBOX. Todas excepto una (CHAOS) fueron campañas estivales. El transporte medio para la Corriente de las Azores a 20º W se estimó en 9.3 ± 2.6 Sv. Parece existir cierta relación inversa entre la posición de dicha corriente y su transporte asociado, con transportes relativamente altos (bajos) cuando la corriente se sitúa al sur (norte) de 35º N. En cuanto a las masas de agua, se observa un incremento de 14.4% del Agua Mediterránea en comparación con las campañas de 1993, 1998 y 2003; sin embargo, el Agua de Labrador ha disminuido su contribución y su propagación hacia el sur entre 1998 y 2009.An important part of the data presented in this paper was obtained through the CAIBEX project: Shelf-ocean Exchanges in the Canaries-Iberia Large Marine Ecosystem (CTM2007-66408-C02/MAR), supported by the Spanish Ministry of Education and Science. The first author, LIC, was funded by a FPU predoctoral fellowship from the National Human Resources Formation Program, within the framework of the 2008–2011 National Scientific Research, Development and Technological Innovation Plan of the Spanish Ministry of Education. The fourth author, NVR, was supported by the Isabel Barreto Program (IN840E) from the Xunta de Galicia.Peer reviewe

Surface waters of the NW Iberian margin: upwelling on the shelf versus outwelling of upwelled waters from the Rías Baixas

A set of hydrographic surveys were carried out in the Ría of Vigo (NW Spain) at 2–4 d intervals during four 2–3 week periods in 1997, covering contrasting seasons. Residual exchange fluxes with the adjacent shelf were estimated with a 2-D, non-steady-state, salinity–temperature weighted box model. Exchange fluxes consist of a steady-state term (dependent on the variability of continental runoff) and a non-steady-state term (dependent on the time changes of density gradients in the embayment). More than 95% of the short-time-scale variability of the exchange fluxes in the middle and outer ría can be explained by the non-steady-state term that, in turns, is correlated (R2>75%) with the offshore Ekman transport. Conversely, 96% of the variability of exchange fluxes in the inner ría rely on the steady-state term. The outer and middle ría are under the direct influence of coastal upwelling, which enhances the positive residual circulation pattern by an order of magnitude: from 10 2 to 10 3 m3s−1. On the contrary, downwelling provokes a reversal of the circulation in the outer ría. The position of the downwelling front along the embayment depends on the relative importance of Ekman transport (Qx, m3s−1km−1) and continental runoff (R, m3s−1). When Qx/ R>7±2 the reversal of the circulation affects the middle ría. Our results are representative for the ‘Rías Baixas’, four large coastal indentations in NW Spain. During the upwelling season (spring and summer), 60% of shelf surface waters off the ‘Rías Baixas’ consist of fresh Eastern North Atlantic Central Water (ENACW) upwelled in situ. The remaining 40% consists of upwelled ENACW that previously enters the rías and it is subsequently outwelled after thermohaline modification. During the downwelling season (autumn and winter), 40% of the warm and salty oceanic subtropic surface water, which piled on the shelf by the predominant southerly winds, enters the rias

Quasi-synoptic transport, budgets and water mass transformation in the Azores–Gibraltar Strait region during summer 2009

We describe the circulation patterns in the Azores–Gibraltar Strait region (North-Eastern Atlantic) during the 2009 CAIBOX cruise on the basis of hydrographic and direct current velocity measurements. This study offers new data for a region where importation of central waters (subpolar and subtropical modes of Eastern North Atlantic Central Water) and exports of Mediterranean Water are strongly related to large-scale dynamics in the North Atlantic Ocean (Azores Current-Mediterranean Water system). The description is backed up quantitatively by the results of a box inverse model, which was used to obtain absolute water mass transport values consistent with thermal wind equations and with conservation of volume, salt and heat. The contributions of water masses were determined in an extended Optimum Multiparameter Analysis from a quasi-synoptic point of view, providing detail in addition to volume, salt and heat transport. The surface–subsurface large-scale current system in the region consists of the Azores Current (13.1 ± 2.5 Sverdrup [Sv], 1 Sv = 106 m3 s−1), the Azores Counter-Current (5.2 ± 2.1 Sv), the Portugal Current (4.5 ± 1.4 Sv) and the Canary Current (7.1 ± 1.1 Sv). Broadly speaking, central waters are imported into the CAIBOX region at a rate of 1.6 ± 0.9 Sv, and Mediterranean Water is exported at a rate of 1.5 ± 0.4 Sv. The downwelling of central waters west of Gibraltar Strait was quantified at 1.1 Sv. Not all this volume participates in MW formation, but 0.8 Sv of entrained central waters; of which 0.5 Sv are from central waters of subpolar origin and 0.3 Sv from subtropical central waters. Of the 4.9 Sv of subtropical central waters advected by the Azores Current, about 0.7 Sv would reach the Gulf of Cadiz region either to take part in central water entrainment or to flow across the Gibraltar Strait as part of the Atlantic inflow to the Mediterranean Sea

Tide and wind coupling in a semienclosed bay driven by coastal upwelling

The Ría de Vigo is a semi-enclosed bay in which tidal residual currents are associated with coastal upwelling events. Both upwelling and downwelling favourable winds generate a bidirectional exchange flow with the shelf – a two-layer circulation with surface waters leaving (entering) the ria and a compensating inflow (outflow) through the bottom layer under upwelling (downwelling) conditions. This vertical circulation changes the vertical density structure inside the ria. In the ria, the tide is mainly semidiurnal (M2, S2 and K2), with some energy in the diurnal band (K1). Our velocity observations show that the vertical structure of the tidal currents in the ria do not exhibit a classic barotropic profile with a bottom boundary layer beneath uniform “free-stream” flow as the tidal bottom boundary layer is affected by stratification. This links tidal circulation to the wind-driven residual circulation, since the latter also greatly helps to control the stratification. We quantify this effect by fitting tidal ellipses to observed velocities through the water column. In addition to this indirect coupling through stratification, there is a direct interaction in which velocities in the upper and bottom layers are best correlated with winds while the mid-water velocities are best correlated with tides. These wind-tide interactions are expected to play a key role in the resuspension and transport of nutrients and phytoplankton in the Ria.CTM2012-3515

Identification and characterization of esential habitats for three cephalopod species in the national parks of Galician Atlantic Islands and Cabrera

31 pages, 16 figures, 8 tables, 1 appendix[EN] We evaluated specific habitat features (bottom substrate type, depth, temperature and season) at random locations in the Cíes archipelago (Galician Atlantic Islands National Park, NW Spain) and to determine their impact on Octopus vulgaris, Sepia officinalis and Loligo vulgaris habitat use. We performed 113 underwater visual transects by scuba diving between April 2012 and August 2015. Habitat features were evaluated as predictors of the presence/absence of spawning dens and egg clusters using Generalized Additive Models. The O. vulgaris spawning essential habitats was found between 5 and 30 m depth in rocky bottoms from Punta Escodelo to Punta Ferreiro (Monteagudo Island), which surface is 6% of the total marine area of the Cíes islands. We propose a complete protection of this area for exploitation. underwater visual transects also showed that there is an O. vulgaris hatchery essential habitat (specimens ≤1000 g) in the sandy bottoms of the Rodas inlet. This small area (2.8% of the total) could be also protected. S. officinalis results revealed two SEH: Bajo de Viños and Piedra del Borrón, hard bottom shoals between 8-13 m covered by sea fans and sea worms and located in the central Cíes islands. We also suggest protecting that small area (0.28% of the total). Very few L. vulgaris eggs masses were found with underwater visual transects and artificial devices attractors in the Cíes islands. Also very few specimens of O. vulgaris and S. officinalis were found with underwater visual transects in Cabrera National Park between 5 and 50 m depth. Two squid spawning essential habitats were located in that park using artificial devices attractors: Na Redona and Ses Rates, both on sandy bottoms from 18 to 50 m depth with fast marine currents. The spawning essential habitats found reveal indicators of three species habitat selection and should help to identify targets for habitat improvement projects and ecosystem management approaches[ES] Mediante 112 censos visuales con escafandra autónoma realizados entre abril de 2012 y agosto de 2015, distribuidos aleatoriamente en el archipiélago de Cíes (Parque Nacional de las Islas Atlánticas de Galicia), se evaluaron las características (tipo de sustrato, profundidad, temperatura y estación) de los hábitats esenciales de Octopus vulgaris, Sepia officinalis y Loligo vulgaris. Dichas características se emplearon como predictores de la presencia/ausencia de guaridas de desove o masas de huevos utilizando Modelos Aditivos Generalizados. El hábitat esencial para el desove de O. vulgaris se localizó entre 5 y 30 m de profundidad en fondos rocosos entre Punta Escodelo y Punta Ferreiro (isla de Monteagudo), cuya superficie es del 6% del total. Proponemos su protección completa para la explotación. Los censos visuales con escafandra autónoma mostraron un hábitat esencial de cría de O. vulgaris en fondos arenosos de la ensenada de Rodas. Esta pequeña área (2,8% del total) podría ser también protegida. Los resultados para S. officinalis revelaron dos HE para el desove: el Bajo de Viños y la Piedra del Borrón, bancos de fondo duro entre 8-13 m cubiertos por gorgonias y poliquetos tubícolas en la ensenada de Rodas. Se sugiere protección para este área (0,28% del total). Apenas se hallaron puestas de L. vulgaris con censos visuales con escafandra autónoma y Dispositivos Atractores de Puesta en Cíes. También se observaron muy escasos ejemplares de S. officinalis y O. vulgaris con censos visuales con escafandra autónoma entre 5 y 50 m de profundidad en el Parque Nacional de Cabrera. Se identificaron dos HE para el desove del calamar en el Parque Nacional de Cabrera usando Dispositivos Atractores de Puesta: Na Redona y Ses Rates, fondos arenosos entre 18 y 50 m de profundidad con rápidas corrientes. Estos HEs son indicadores de selección del hábitat, y constituyen un notable apoyo para identificar objetivos en proyectos de conservación de hábitats y enfoques ecosistémicos en la gestión pesqueraMiguel Cabanellas-Reboredo fue becado por la Conselleria de Educació del Govern de les Illes Balears (Fondo Social Europeo) y actualmente beneficiario de contrato post-doctoral Juan de la Cierva formación (MINECO). Marta Sestelo disfrutó de beca de investigación SFRH/BPD/93928 de Fundacão Ciência e Tecnologia de Portugal y de proyectos del Ministerio de Ciencia e Innovación y la Xunta de Galicia. Este proyecto estuvo financiado por el Organismo Autónomo de Parques Nacionales del Ministerio de Agricultura, Alimentación y Medio Ambiente (CEFAPARQUES, Proyecto número: 458/2011)N

Changes in community assemblages during the development of a thin layer of phytoplankton (TLP)

ASLO 2021 Aquatic Sciences Meeting, 22–27 June, VirtualHigh resolution measurements of phytoplankton (from pico- to mesoplankton) and physicochemical parameters were made from 2 to 14 July, 2018 in a coastal embayment (Ría de Pontevedra, NW Spain). The main objective of this work was to study changes in phytoplankton community structure during the development of a phytoplankton thin layer. The observational approach highlighted the role of short term changes of abiotic and biotic habitat conditions in the dynamics of phytoplankton assemblages. During relaxation conditions in the beginning of the cruise, small rounded dinoWagellates Alexandrium minutum (PSP toxins) and Scrippsiella cf. dominated. Then, during the transition from downwelling to upwelling conditions, a thin layer was formed, composed of Pseudo-Nitzschia spp (ASP toxins) and Leptocylindrus danicus. Fine spatial (cm-m) and temporal (hours-days) scale measurements were carried out. A combination of traditional microscopy analysis (279 samples analyzed at species level when possible) and imaging-in-Wow technique for morphometric characterization (280 samples generating about 480000 raw images, containing plankton, detritus and mineral particles) allowed us to assess the effect of the environmental =ltering on phytoplankton morphological and functional traits. The dynamics of co-occurring populations of Pseudo-nitzschia spp and Alexandrium minutum was considered in the frame of changing habitat conditionsThis study was funded by project REMEDIOS (CTM2016-75451-C2-2-R).N

SPOT and GPRS drifting buoys for HF Radar calibration

9th International Workshop on Marine Technology (MARTECH), virtual, 16-18 June 2021Traditional drifting buoys have been designed to measure the surface currents at a nominal depth of 15m with drogues of 6m height. Herein, in order to assess the performance of HF Radars two designs of Lagrangian drifting buoys have been developed and targeted to provide the vertically averaged velocity of the currents in the frst 2 and 0.5 meters of the water column. These are the layer heights of the HF Radars of RAIA observatory. The buoys were made with standard materials and of-the-shelf electronics, to keep costs as low as possibleN

Air-sea CO2 fluxes in the Atlantic as measured during the FICARAM cruises

A total of fourteen hydrographic cruises spanning from 2000 to 2008 were conducted during the spring and autumn seasons between Spain and the Southern Ocean, under the framework of the Spanish research project FICARAM. The performed underway measurements are processed and analysed to describe the meridional air-sea CO2 fluxes (F CO2) along the Atlantic Ocean. The data was organised into different biogeochemical oceanographic provinces, according mainly to the thermohaline characteristics. The obtained spatial and temporal distributions of F CO2 follow the generally expected patterns and annual trends. The Subtropical regions in both hemispheres alternated the CO2 source and sink nature from autumn to spring, respectively. On the other hand, Tropical waters and the Patagonian Sea clearly behaved as sinks of atmospheric CO2 like the waters of the Drake Passage during autumn. The obtained results during the cruises also revealed significant long-term trends, such as the warming of equatorial waters (0.11±0.03 Cyr−1) and the decrease of surface salinity (−0.16±0.01 yr−1) in tropical waters caused by the influence of the Amazon River plume. This reduction in surface salinity appears to have a direct influence over the CO2 storage rates, fostering the uptake capacity of atmospheric CO2 (−0.09±0.03 molm−2 yr−1). An analysis of the biogeochemical forcing on the CO2 fugacity (fCO2) variability performed from an empirical algorithm highlighted the major role of the Amazon River input in the tropical North Atlantic fluxes. In addition, it has provided a quantitative measure of the importance of the thermodynamic control of F CO2 at temperate latitudes