Water flows through mussel rafts and their relationship with wind speed in a coastal embayment (Ría de Ares-Betanzos, NW Spain)

14 páginas, 4 tablas, 8 figurasKnowledge of water flows through mussel rafts and their controlling factors is required for an ecosystem approach to the sustainable management of this culture in the Galician rías. With this aim, 4 acoustic 2D-ACM current meters were hung from the bow of 4 rafts located in the mussel cultivation areas of the Ría de Ares-Betanzos (NW Spain) during autumn 2007. Simultaneously, an Aanderaa DCM12 Doppler profiler was moored in an area free of rafts in the middle ría. There were differences in the subtidal and tidal dynamics of the middle channel and mussel farm areas. The tide explained 51.5% of the total variance of the surface current in the middle ría. The explained variance in the seed collection areas of Redes (inner ría) and Miranda (outer ría), where only 2–3 rafts are anchored, were 64.1% and 16.8%, respectively. In the cultivation areas of Arnela (inner ría) and Lorbé (middle ría), where 101 and 40 rafts are anchored, 14.3% and 53.4% of the total variance was explained by the tide. These disparities in the contribution of the tide are likely due to a combination of topographic and bathymetric differences among sites and distortions of the natural flow by the rafts and their hanging ropes. Furthermore, there was a marked influence of winds on the subtidal currents within the rafts; contrasting correlation coefficients and lag times between wind speed and currents were observed for the outer and inner sides of the embayment. The filtration rate of the growing mussels and the number of mussels per raft allow an efficient clearing of the particles transported across the hanging ropes by the measured subtidal currents of 2–3 cm s–1 characteristic of the cultivation areas of Arnela and LorbéPROINSA Mussel Farm, codes CSIC20061089 and 0704101100001Xunta de Galicia PGIDIT06RMA018E and PGIDIT09MMA038EESSMA project Spain–Canada Grant of MICINNPeer reviewe

Evidencias do cambio climático na hidrografía e a dinámica das rías e da plataforma galega

16 páginas, 9 figuras, 3 tablas[EN] This study is focused on multidecadal-scale variations of the hydrographic and hydrodynamic features of Rías and shelf waters off Galicia. Water masses take, through their thermohaline characteristics, a footprint of the climatic variability, mainly caused by changes either in the hydrological budget (precipitation, evaporation, runoff), in heat exchange and wind stress. In this study we focus in the evidences of change in the surface and sub-surface water mass characteristics. Regarding surface water masses, a significant warming during the last 45 years has been noticed, at a rate of 0.17 ºC/ decade. This warming was especially intense from the 1970’s, 0.27 ºC/decade. The tendency is opposite in subsurface waters, but it only takes into account data from the last 15 years. Regarding hydrodynamics, because of its strong influence in the renewal time of the Rías and consequently in their living resources, a study of decadal changes in the estuarine circulation of the Rías de Vigo and Arousa has been made. Results showed a progressive decay in the estuarine circulation, which causes an increase of renewal times. On the other hand, indirect evidence of a possible deceleration of the winter Iberian Poleward Current (IPC) are reported. This slow down is partially caused by a decrease in the meridional (N-S) temperature gradient off the Iberian coast. Nevertheless, the fall of the meridional gradient is not clear because it has been inferred from surface waters. On the contrary, IPC seems to be intensified by the increasing southerly autumn winds, although it appears weakened by the decreasing southerly winter winds. Thus, the overall effect of the CIP is still uncertain. Finally, a study of sea level and wave changes on the Galician coast has been made. An increase of (2-2.5 cm/ decade) in the sea level as well as a decrease in the wave height (3 cm/decade) has been reported, but in this last topic results are not significant[GA] Este estudo centrarase en determinar as variacións que ocorren a escalas multidecadais nas características hidrográficas e hidrodinámicas das augas das rías e da plataforma fronte a Galicia. As masas de auga reciben a través das súas características termohalinas unha pegada das alteracións climáticas, principalmente a causa de cambios no balance hidrolóxico (precipitación, evaporación, achegas continentais), do intercambio de calor e da acción do vento. Neste estudo analizaremos as evidencias de cambio nas características das masas de auga superficiais e subsuperficiais. Nas primeiras detectouse quentamento de xeito significativo nos últimos 45 anos a unha taxa media de 0,17 ºC por década, especialmente intenso desde hai 30 anos, 0,27 ºC por década. Nas augas subsuperficiais a tendencia é a inversa, aínda que só se conta con datos dos últimos 15 anos. En canto á hidrodinámica, e pola súa forte implicación nos tempos de renovación da ría e, polo tanto, nos recursos mariños que viven nela, fíxose un estudo sobre os cambios na circulación estuárica das rías de Vigo e Arousa nas últimas décadas. Os resultados amosan un descenso paulatino a longa escala temporal da circulación que causa un aumento dos tempos de renovación. Por outra banda, achéganse evidencias indirectas dunha posible ralentización da corrente invernal cara ao Polo (CIP) causada por un descenso no gradiente meridional (N-S) de temperatura fronte ás costas ibéricas. Non obstante, o descenso do gradiente meridional non está claro, pois induciuse só a partir de datos superficiais. Ademais, a propia CIP amosa estar intensificada pola maior intensidade dos ventos sur no outono e debilitada polo descenso dos ventos do sur no inverno, polo que o efecto global na CIP é aínda incerto. Por último, faise un estudo dos cambios do nivel do mar e da ondada nas costas galegas que amosa un aumento daquel (2-2,5 cm/década) e un descenso desta (3 cm/década), aínda que no caso da ondada os resultados non son concluíntesPeer reviewe

SPOT and GPRS drifting buoys for HF Radar calibration

Traditional 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 possible.Peer Reviewe

Model type II regression for lagrangian validation of HF radar velocities in the NW Iberian Peninsula

Two designs of lagrangian low-cost drifting buoys have been developed in order to monitor the ocean surface dynamics in the North-west Iberian Peninsula and provide ground-truth observations that can be used to assess the performance of High Frequency (HF) Radars of RAIA observatory from 2020 to 2022. Since regression model type I, which is typically used in buoy-HF radar antennas validations, does not consider the presence of errors in the observations from both instruments, regression model type II was proposed to instrument intercomparison. Furthermore, a new metric was developed to better assess both model types regressions in lagrangian validations.Peer Reviewe

Extreme wave height events in NW Spain: a combined multi-sensor and model approach

The Galician coast (NW Spain) is a region that is strongly influenced by the presence of low pressure systems in the mid-Atlantic Ocean and the periodic passage of storms that give rise to severe sea states. Since its wave climate is one of the most energetic in Europe, the objectives of this paper were twofold. The first objective was to characterize the most extreme wave height events in Galicia over the wintertime of a two-year period (2015–2016) by using reliable high-frequency radar wave parameters in concert with predictions from a regional wave (WAV) forecasting system running operationally in the Iberia-Biscay-Ireland (IBI) area, denominated IBI-WAV. The second objective was to showcase the application of satellite wave altimetry (in particular, remote-sensed three-hourly wave height estimations) for the daily skill assessment of the IBI-WAV model product. Special attention was focused on monitoring Ophelia—one of the major hurricanes on record in the easternmost Atlantic—during its 3-day track over Ireland and the UK (15–17 October 2017). Overall, the results reveal the significant accuracy of IBI-WAV forecasts and prove that a combined observational and modeling approach can provide a comprehensive characterization of severe wave conditions in coastal areas and shows the benefits from the complementary nature of both systems.The authors also would like to thank the support by Interreg Atlantic Area project MyCOAST (EAPA 285/2016) co-funded by the ERDF (EU)S

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

Model type II regression for lagrangian validation of HF Radar velocities in the NW Iberian Peninsula

2 pages, 1 figure.-- MARTECH23, 10th Marine International Workshop on Marine Technology, 19-20 de Junio de 2023, Castellón de la PlanaTwo designs of lagrangian low-cost drifting buoys have been developed in order to monitor the ocean surface dynamics in the North-west Iberian Peninsula and provide ground-truth observations that can be used to assess the performance of High Frequency (HF) Radars of RAIA observatory from 2020 to 2022. Since regression model type I, which is typically used in buoy-HF radar antennas validations, does not consider the presence of errors in the observations from both instruments, regression model type II was proposed to instrument intercomparison. Furthermore, a new metric was developed to better assess both model types regressions in lagrangian validationsThe authors also would like to thank the support from projects RADAR ON RAIA (0461_RADAR ON RAIA_1_E, co- funded by the European Union through EP-INTERREG V-A España-Portugal POCTEP program) and STRAUSS (PID2019-106008RB-C21) funded by MCIN/AEI/10.13039/501100011033N

Extreme wave height events in NW Spain: a combined multi-sensor and model approach

The Galician coast (NW Spain) is a region that is strongly influenced by the presence of low pressure systems in the mid-Atlantic Ocean and the periodic passage of storms that give rise to severe sea states. Since its wave climate is one of the most energetic in Europe, the objectives of this paper were twofold. The first objective was to characterize the most extreme wave height events in Galicia over the wintertime of a two-year period (2015–2016) by using reliable high-frequency radar wave parameters in concert with predictions from a regional wave (WAV) forecasting system running operationally in the Iberia-Biscay-Ireland (IBI) area, denominatedIBI-WAV. The second objective was to showcase the application of satellite wave altimetry (in particular, remote-sensed three-hourly wave height estimations) for the daily skill assessment of the IBI-WAV model product. Special attention was focused on monitoring Ophelia—one of the major hurricanes on record in the easternmost Atlantic—during its 3-day track over Ireland and the UK (15–17 October 2017). Overall, the results reveal the significant accuracy of IBI-WAV forecasts and prove that a combined observational and modeling approach can provide a comprehensive characterization of severe wave conditions in coastal areas and shows the benefits from the complementary nature of both systems

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

Radar on RAIA: High frequency radars in the RAIA Observatory

The RADAR ON RAIA project aims to update and extend beyond the Galician border the High Frequency (HF) radar network that has been operating since 2011 in the framework of the RAIA Observatory. The Project is allowing the establishment of a cross-border collaboration beyond the physical infrastructure itself, developing a sharing strategy of maintenance procedures, validation and data processing on both sides of the border, as well as an easy and public access to all the information. In addition, new products are being developed to exploit the potential of the HF radar technology.Peer Reviewe