(1) Portuguese Institute for the Sea and Atmosphere (IPMA), Lisbon, Portugal
(2) Dom Luiz Institute, University of Lisbon, IDL-FCUL, Lisbon, Portugal
(3) Portuguese Institute for Nature Conservation and Forests, Portugal
(4) Centre for Marine Sciences (CCMAR), University of Algarve
The Atlantic dimension of Portugal led to the prioritisation of the European Multidisciplinary Seafloor and Water Column Observatory – Portugal (EMSO-PT) in the national scientific infrastructures’ roadmap. EMSO-PT is a research consortium that brings together 15 research institutions, aiming at implementing a network of multidisciplinary underwater observatories located along the Atlantic coast, laboratories, and data processing support infrastructures. The goal of EMSO-PT is to generate continuous scientific data on marine environmental processes related to the interaction between the geosphere, biosphere, and hydrosphere and to develop new sensors and platforms which will extend ocean monitoring national capabilities soon. Monitored parameters include biotic and abiotic variables of the ocean floor and water column, namely temperature, salinity, turbidity, acoustics, currents, dissolved oxygen, and carbon dioxide. EMSO-PT is part of a larger European scale effort and corresponds to the Portuguese counterpart of the European Multidisciplinary Seafloor and Water Column Observatory – European Research Infrastructure Consortiums (EMSO-ERIC). The EMSO-ERIC channels and at the “we are Atlantic” digital platform (Silveira et al, 2022) also focus on disseminating data that enable the integration and dissemination of data acquired by all partners of EMSO-ERIC, and by the research community at large. A combination between fixed observatories and autonomous vehicles is also foreseen to extend regular Eulerian observations to major water masses that interact with the different Portuguese Atlantic territories (Carapuço et al., 2022). In this work, we present four-months of continuous operation of EMSO-ERIC Iberian Margin node carried out within the scope of the EMSO-PT initiative.
1. Scope and role of EMSO-ERIC
EMSO-ERIC is a distributed infrastructure of deep marine observatories that aims to promote long-term observation of marine environmental processes, including the interactions between the geosphere, biosphere, and hydrosphere - preferably in real time. This infrastructure is organised as an ERIC, constituted on September 29, 2016, with headquarters in Rome (Italy), and bringing together seven member states: Italy, Spain, France, Norway, Romany, Greece, and Portugal.
This infrastructure itself is designed as a distributed set of ocean observation resources located in key places for the study of marine processes, in the Arctic, Atlantic, Mediterranean and Black Sea. EMSO-ERIC aims to be the deep marine component of COPERNICUS and coordinates its activity with similar initiatives in Japan (DONET - Dense Oceanfloor Network System for Earthquakes and Tsunamis) and Canada (Ocean Networks Canada's)
2. Seafloor and Water-Column Observation in the Portuguese Margin
Portuguese teams have participated in early EMSO-ERIC initiatives, but with a small role, namely through the incorporation of seismic sensors and biological collectors, in cooperation with Italy (in Iberia) and France (in Azores). The EMSO-PT aims at developing new instrumentation for seafloor and water column sampling, deploying observatories on the seafloor, installing capacities for laboratory analysis and disseminating relevant datasets for ocean monitoring. This integrated approach has the advantage of fostering cooperation between marine engineering research groups and the oceanographic community, whilst ensuring long term sustainability - both from the technological and the scientific point of view.
The first deploy of a deep seafloor station close to SW Iberia (3207m depth, at 36.3646°N, 9.4814°W) was done between August 2007 and August 2008, under the NEAREST - NEAR shore sourcES of Tsunami project: Towards an early warning system. A GEOSTAR - GEophysical and Oceanographic STation for Abyssal Research platform (Favali et al., 2006) was equipped with a bottom pressure sensor, an accelerometer CMG-5T and a broad-band Guralp seismometer CMG-40T, aiming at acquiring data for Tsunami Early Warning purposes. A second mission took place on November 10, 2009, close to the same location. A near real-time communication system was successfully tested, with the automatic issuing of periodic messages containing a summary of the data acquired by the GEOSTAR observatory from the sea floor to the land station via satellite link. Nevertheless, the buoy mooring remained a vulnerable part of the communication chain (Miranda et al., 2015).
After 2021, the EGIM - EMSO Generic Instrument Module (Lantéri et al., 2017) was taken as the basis for the re-occupation of the Iberian Margin node, ensuring a wider range of sensors and parameters. EGIM payload includes sensors to measure conductivity and temperature (SeaBird SBE37), dissolved oxygen (optical DO - Aanderaa 4381dw), absolute pressure (RBRquartz3 BPR), turbidity (WETLabs ECO FNLTU), passive acoustics (OceanSonics icListen HF SC60) and acoustics doppler current profiler (ADCP) (Teledyne RDI 300 kHz Workhorse Monitor direct-reading).
3. Deployment and Operation
The oceanographic campaign “EMSO-PT leg 2” took place between May 31 and June, 1, 2022. The main goal was the installation of three moorings SW of Cape São Vicente (36.8455°N, 8.9271°W), western Gulf of Cadiz: the EGIM, a vertical wave-powered water column profiler (Wirewalker), and a subsurface ADCP. A short documentary about the EMSO-PT oceanographic campaign is available on IPMA’s YouTube channel. The EGIM was installed in a subsurface mooring, suspended 200 m deep, approximately 15 m from the bottom. It was configured with a low-resolution acquisition rate, dependent on the sensor. The conductivity, temperature, turbidity, and dissolved oxygen sensors collect one (1) sample every 15 minutes. The absolute pressure sensor was set to observe at a higher frequency, recording twenty (20) consecutive 1 Hz samples every 2 minutes. The hydrophone (passive acoustics), records one (1) 1-minute audio file every 5 minutes at a rate of 128 kS/s. The EGIM ADCP was set to observe 3 m bins with 120 samples per hour. The Wirewalker was programmed to provide high resolution (2 Hz) and high temporal density (5-6 profiles/hour) vertical profiles of temperature, salinity, Chla, turbidity and dissolved oxygen from the near surface to 150 m depth, complemented by an upward facing ADCP, installed at 150 m depth (Rautenbach et al., 2023).
The three moorings were recovered on October 6, 2022 (Figure 1). Data collected were made freely available through the Centre of Marine Sciences (CCMAR) – ERDDAP: Easier accesses to scientific data
The four-months of continuous operation of EMSO-ERIC Iberian Margin node generated the data displayed in figure 2.
4. Conclusions and Future Work
The four-month of continuous operation of the Iberian Margin node of EMSO-ERIC is an important step towards a continuous operation on the long term. A second EGIM is being acquired by IPMA (and a vertical water column profiler). In the near future, there will always be an equipment on the seafloor while the redundant instrument will be serviced onshore. It also focus on complementing the existing sensors, to allow the monitoring of carbon intake in the ocean. The described operation was fundamental to test the conditions in which the EMSO-PT ocean observation network will be established in the future for long-term monitoring. The number of resources involved in systematic and continued ocean observation demands such assessment, to evaluate local environmental conditions, catch instrument failures and define optimum sensor configuration and layout.
References
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