Evaluating the surface circulation in the Ebro delta (northeastern Spain) with quality-controlled high-frequency radar measurements

The Ebro River delta is a relevant marine protected area in the western Mediterranean. In order to promote the conservation of its ecosystem and support operational decision making in this sensitive area, a three-site standard-range (13.5 MHz) CODAR SeaSonde high-frequency (HF) radar was deployed in December 2013. The main goal of this work is to explore basic features of the sea surface circulation in the Ebro deltaic region as derived from reliable HF radar surface current measurements. For this aim, a combined quality control methodology was applied: firstly, 1-year long (2014) real-time web monitoring of nonvelocity-based diagnostic parameters was conducted to infer both radar site status and HF radar system performance. The signal-to-noise ratio at the monopole exhibited a consistent monthly evolution, although some abrupt decreases (below 10 dB), occasionally detected in June for one of the radar sites, impacted negatively on the spatiotemporal coverage of total current vectors. It seemed to be sporadic episodes since radar site overall performance was found to be robust during 2014. Secondly, a validation of HF radar data with independent in situ observations from a moored current meter was attempted for May–October 2014. The accuracy assessment of radial and total vectors revealed a consistently high agreement. The directional accuracy of the HF radar was rated at better than 8°. The correlation coefficient and root mean square error (RMSE) values emerged in the ranges [0.58–0.83] and [4.02–18.31] cm s−1, respectively. The analysis of the monthly averaged current maps for 2014 showed that the HF radar properly represented basic oceanographic features previously reported, namely, the predominant southwestward flow, the coastal clockwise eddy confined south of the Ebro delta mouth, or the Ebro River impulsive-type freshwater discharge. The EOF analysis related the flow response to local wind forcing and confirmed that the surface current field evolved in space and time according to three significantly dominant modes of variability

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

Origin and fate of a bloom of Skeletonema costatum during a winter upwelling/downwelling sequence in the Ría de Vigo (NW Spain)

Original research paperThe onset, development and decay of a winter bloom of the marine diatom Skeletonema costatum was monitored during a 10 d period in the coastal upwelling system of the Rı´a de Vigo (NW Spain). The succession of upwelling, relaxation and downwelling-favorable coastal winds with a frequency of 10 –20 d is a common feature of the NW Iberian shelf. The onset of the bloom occurred during an upwelling-favorable 1⁄2 wk period under winter thermal inversion conditions. The subsequent 1⁄2 wk coastal wind relaxation period allowed development of the bloom (gross primary production reached 8gCm–2 d–1) utilizing nutrients upwelled during the previous period. Finally, downwelling during the following 1⁄2 wk period forced the decay of the bloom through a combination of cell sinking and downward advection.Financial support came from the Spanish Ministerio de Ciencia y Tecnologı´a (MCyT) grant REN2000-0880-C02-01 and Xunta de Galicia grant PGIDT01MAR40201PN; a fellowship from the MCyT and the I3P-CSIC Program.Versión del editor0,98

Tidal and wind influences on circulation in the southern mouth of the Ría de Vigo (NW Iberian Peninsula)

Tidal and wind influences on the velocity field in the Ría de Vigo were assessed using atmospheric data from two meteorological stations located at Bouzas port and on an oceanic buoy off Silleiro Cape along with oceanic data from an ADCP moored in the Ría for a 72-day period. A two-layer circulation pattern was observed. Near-surface and near-bottom currents are primarily influenced by wind (especially remote winds), separated by an intermediate layer dominated by tidal variability. At subtidal frequencies, residual currents are well correlated with wind variability. Remote wind forcing exhibited a markedly high correlation with surface layer currents, indicating the major role played by wind in the long-term upwelling-modulated circulation of the Ría

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

9th International Workshop on Marine Technology (MARTECH), virtual, 16-18 June 2021The 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 technologyN

A window to the sea: environmental indicators for coastal risk management under the RAIA observatory (NW-Iberian Peninsula)

ECSA 59 Using the best scientific knowledge for the sustainable management of estuaries and coastal seas, San Sebastian (Spain), 5th–8th September 2022The international RAIA Observatory (www.marnaraia.org) resulted from the effort of 12 research and academic institutions and public agencies (Spanish and Portuguese) working in the field of meteorology and oceanography. The RAIA Observatory serves the main maritime activities of the Galicia-Northern Portugal Euroregion and contributes to collaborative observational networks. Under the framework of coastal risk management, environmental indicators are fundamental tools for the evaluation and mitigation of environmental risks, showing the current state and helping to predict future changes on ecosystem health regarding environmental risks. In last years, the different partners of the RAIA Observatory have identified 38 environmental indicators, in which 12 key risks affecting the ecosystem services of the Galicia-Northern Portugal Euroregion are being evaluated. Data was analyzed and compiled by the various partners of the RAIA Observatory and the development and optimization of the environmental indicators has been done according to the specifications provided by the European Environmental Agency (EEA) and the International Panel for Climate Change (IPCC). The resulting environmental indicators are included and shared on a publicly-accessible Web service, georeferenced and accompanied by plots (https://marrisk.inesctec.pt/public/#!/indicators). So far, the current status of the indicators has allowed us to establish risk assessment protocols for the Euroregion, and identify critical gaps in a temporal and spatial coverage. The inclusion of the environmental indicators in the RAIA Observatory is of great relevance for national and international data exchange and promotes future collaborationsN

A window to the sea: environmental indicators for coastal risk management under the RAIA observatory (NW-Iberian Peninsula)

Poster.-- International Ocean Data Conference 2022, Sopot, Poland, 14-16 February 2022Environmental indicators are fundamental tools for the evaluation and mitigation of environmental risks, showing the current state and helping to predict future changes on ecosystem health regarding environmental risks The framework of the RAIA observatory www marnaraia org identified 38 environmental indicators, in which 12 key risks affecting the ecosystem services of the Euroregion Galicia Northern Portugal have been evaluated The objective of this initiative is to optimize and analyze the environmental indicators identified for the Euroregion and make them available through a Web service that allows users to get information on the current state and evolution of the ecosystem healthThis contribution has been funded by the European Union MarRISK project Adaptación costera ante el Cambio Climático conocer los riesgos y aumentar la resiliencia (0262_MarRISK1_E) through EP-INTERREG V A España-Portugal (POCTEP) programN

Evaluating the surface circulation in the Ebro delta (northeastern Spain) with quality-controlled high-frequency radar measurements

The Ebro River delta is a relevant marine protected area in the western Mediterranean. In order to promote the conservation of its ecosystem and support operational decision making in this sensitive area, a three-site standard-range (13.5 MHz) CODAR SeaSonde high-frequency (HF) radar was deployed in December 2013. The main goal of this work is to explore basic features of the sea surface circulation in the Ebro deltaic region as derived from reliable HF radar surface current measurements. For this aim, a combined quality control methodology was applied: firstly, 1-year long (2014) real-time web monitoring of nonvelocity-based diagnostic parameters was conducted to infer both radar site status and HF radar system performance. The signal-to-noise ratio at the monopole exhibited a consistent monthly evolution, although some abrupt decreases (below 10 dB), occasionally detected in June for one of the radar sites, impacted negatively on the spatiotemporal coverage of total current vectors. It seemed to be sporadic episodes since radar site overall performance was found to be robust during 2014. Secondly, a validation of HF radar data with independent in situ observations from a moored current meter was attempted for May–October 2014. The accuracy assessment of radial and total vectors revealed a consistently high agreement. The directional accuracy of the HF radar was rated at better than 8°. The correlation coefficient and root mean square error (RMSE) values emerged in the ranges [0.58–0.83] and [4.02–18.31] cm s−1, respectively. The analysis of the monthly averaged current maps for 2014 showed that the HF radar properly represented basic oceanographic features previously reported, namely, the predominant southwestward flow, the coastal clockwise eddy confined south of the Ebro delta mouth, or the Ebro River impulsive-type freshwater discharge. The EOF analysis related the flow response to local wind forcing and confirmed that the surface current field evolved in space and time according to three significantly dominant modes of variability

Physical–biological coupling in the coastal upwelling system of the Ría de Vigo (NW Spain). I: In situ approach

Original research articleThe fate of the inorganic and organic nitrogen trapped in the coastal upwelling system of Ría de Vigo (NW Spain) was studied at the 2 to 4 d time-scale during July and September 2002. A transient geochemical model was applied to the measured residual currents and concentrations of inorganic nitrogen (NT), and dissolved (DON) and particulate (PON) organic N to obtain (1) the net balance of inputs minus outputs (i – o); (2) the net accumulation; and (3) the net ecosystem production (NEP) of NT, DON and PON. Previously unaccounted lateral variations in residual currents and N species concentrations in the ría were considered. The ría was autotrophic during July (average NEP, 107 mg N m–2 d–1). About 25% of this material was exported to the shelf and the remaining 75% was transferred to the sediments or promoted to higher trophic levels. During summer upwelling episodes, 30 to 70% of the organic N exported to the shelf came from materials previously accumulated in the ría. By contrast, during summer relaxation, 60 to 70% of the accumulated organic N came from in situ conversion of NT and the remaining 30 to 40% was allochthonous. As shown by other authors, NEP was rather low during intense upwelling and increased to high values during its subsequent relaxation. In September, the metabolism changed from heterotrophic to slightly autotrophic (average NEP, 26 mg N m–2 d–1). The DON and PON imported from the shelf during autumn downwelling experienced a different fate: DON was consumed and PON accumulated in the ría. By contrast, DON and PON were produced in situ at the expense of N nutrients previously accumulated into the system during autumn relaxation. The roles of vertical convection and turbulent mixing in the fertilization of the photic layer were also assessed. Mixing was the most important fertilization mechanism, ensuring transport of nutrients under upwelling and downwelling conditions.The Spanish Ministerio de Educación y Ciencia (MEC), grant nos. REN2000-0880-C02-01 and -02 and the Xunta de Galicia grant no. PGIDT01MAR40201PN. This is contribution no. 39 of the Unidad Asociada GOFUVICSIC and predoctoral fellowships from the MEC and postgraduate fellowships from the CSIC-I3P programme and postdoctoral programme ‘Parga Pondal’ of the ‘Xunta de Galicia"Versión del edito