In the last few years, a number of technologies to use fiber optic cables as sensing devices have been established, among them Distributed Acoustic Sensing (DAS) and State-of-Polarisation (SoP). The potential of these technologies for monitoring a range of Earth System parameters in submarine cables has been demonstrated through several pilot experiments, but full integration with telecommunication infrastructure has not yet been achieved. The SUBMERSE (SUBMarinE cables for ReSearch and Exploration) project links Research and Education Networks (RENs), universities, research institutes and industry to establish multi-method monitoring along submarine optical telecommunication cables at several key oceanic cable routes branching off from Sines in Portugal, Madeira, Svalbard and in the Ionian Sea, and in addition the Transatlantic cable between Fortaleza and Sines. Those pilot sites should serve as a blueprint for establishing continuous monitoring services along many more cables. The project comprises technical developments for integrating DAS and SoP measurements, for establishing differential SoP measurements between repeaters and for operating DAS in a co-existence mode, i.e., in fibers also carrying telecommunications traffic. Furthermore, a range of geoscientific and marine biology use cases are included, which seek to establish code/services for monitoring earthquakes and tsunamis, tracking whales, measuring the sea state and other Earth System variables. The data collected by SUBMERSE will be distributed according to FAIR principles through established community-specific distribution channels such as EIDA for seismological data, with exceptions for security sensitive time periods, spatial or frequency ranges. The presentation will present some example data and methodological developments in the context of this project. Furthermore, an outlook on the seismological real-time and archive products will be provided.

Research infrastructures have been established throughout Europe in order to create robust organizations that will facilitate and enhance research and innovation processes and will advance society with innovative products and services. The Hellenic Integrated Marine Observing, Forecasting and Technology System (component of HIMIOFoTS RI) has been implemented in the framework of the National Roadmap for Research Infrastructures to form a large-scale infrastructure for the marine environment in Greece. It links together ocean observing and forecasting systems, coastal zone monitoring and management practices, as well as ocean engineering testing facilities. The overarching framework of the system supports the coordination of five organizations with expertise in the field of marine science and technology, the central management of research activities, and the common development of services and products. It comprises facilities and resources while it provides open access to research communities (academia, industry) to support the scientific advancements and innovation in their fields. The Hellenic Marine Observing, Forecasting and Technology System was further enhanced during its implementation through significant upgrades and developments in order to extend its observing capacity and the forecasting and technological abilities, while advancing the provided services and products.

Advanced marine observation infrastructures are the most significant scientific tool for the study of marine ecosystem trends and shifts. Ocean monitoring technologies, though highly demanding and expensive, are essential for the monitoring and long-term study of oceanic systems. The POSEIDON system for monitoring and forecasting the marine environment is an augmented research infrastructure, unique in the Eastern Mediterranean basin, contributing to the European Ocean Observing System implementation, focusing—among others—on biogeochemical observations and deep-sea ecosystem and geological processes. The technological evolution of the POSEIDON system through a science-coupled strategy supported by engineers and scientists, resulted in a state-of-the-art ocean observing system. There has been a continuous expansion of the infrastructure with new scientific platforms and supporting facilities. Innovative sensing technologies were introduced in the operational data acquisition and new methodologies and tools were developed to improve the system operations and efficiency. As a part of the scientific community of ocean observatories, POSEIDON contributes actively to the improving of the ocean observing. International access to engineering and field demonstrating services, data products and technology testing facilities has been offered to scientists and industry partners. POSEIDON is a widely recognizable international technology testing/demonstrating node specializing in marine technology providing high-level services.

The European Multidisciplinary Seafoor and water Column Observatory (EMSO, www.emso.eu) is a distributed research infrastructure (RI), composed of fxed-point deep-sea observatories and shallow water test sites at strategic environmental locations from the southern entrance of the Arctic Ocean all the way through the North Atlantic through the Mediterranean to the Black Sea. Working as a single powerful system, it is a valuable new tool for researchers and engineers looking for long time series of high-quality and high-resolution data to study and continuously monitor complex processes interactions among the geosphere, biosphere, hydrosphere and atmosphere, as well as to test, validate and demonstrate new marine technologies.

The integration of the radioactivity spectrometer KATERINA II in a fixed station (buoy) of the POSEIDON network at the North Aegean Sea within the framework of MARRE Project is presented. The acquisition period lasted from 20 November 2019 till 22 February 2020. An intense increment of the activity concentration of radon progenies (up to an order of magnitude) was recorded during rainfall. More specifically, the 214Bi activity concentration varied from 0.09 to 0.53 Bq L−1 without rainfall and the 214Pb activity concentration varied from 0.14 to 0.81 Bq L−1. The 214Bi activity concentration during rainfall ranged from 0.4 to 5.4 Bq L−1 and of 214Pb from 0.3 to 5.3 Bq L−1. The minimum detectable activity of the KATERINA II detection system for measuring low level activities of 137Cs is optimized applying background subtraction and the full spectrum analysis technique.

We present the in-situ biogeochemical data products distributed by the Copernicus Marine Service since 2018. The products offer available data of chlorophyll, oxygen, and nutrients (nitrate, silicate and phosphate), both in near-real time and as re-processed data, collected across the globe. The re-processing involves careful quality control utilizing tailored automated quality control procedures combined with visual inspection of questionable values by experts. Moreover, oxygen data are provided with uniform units for modelers (µmol/l) and other oceanic applications and monitoring purposes (µmol/kg) The products integrate observations aggregated from the Regional EuroGOOS consortium, as well as from SeaDataNet2, National Data Centers (NODCs) and JCOMM global systems, among others.We highlight some use cases, including a study showing an overall decline in the nutrient concentration (nitrate and silicate) of the Atlantic Water flowing though the Nordic Seas en-route to the Arctic Ocean, during the period 1990-2019. Moreover, the study shows indications of a delayed-response reduction further downstream in the Arctic Water exiting the Arctic Ocean through Fram Strait. Other use cases include the study of variability in the concentration of dissolved oxygen in the Mediterranean Sea, showing an association with dynamical processes.The in-situ near-real time biogeochemical product is updated every month whereas the re-processed product is updated two times per year. Products are delivered on NetCDF4 format compliant with the CF1.7 standard and well-documented quality control procedures.

Citation: Testor P, Young Bd, Rudnick DL, Glenn S, Hayes D, Lee CM, Pattiaratchi C, Hill K, Heslop E, Turpin V, Alenius P, Barrera C, Barth JA, Beaird N, Bécu G, Bosse A, Bourrin F, Brearley JA, Chao Y, Chen S, Chiggiato J, Coppola L, Crout R, Cummings J, Curry B, Curry R, Davis R, Desai K, DiMarco S, Edwards C, Fielding S, Fer I, Frajka-Williams E, Gildor H, Goni G, Gutierrez D, Haugan P, Hebert D, Heiderich J, Henson S, Heywood K, Hogan P, Houpert L, Huh S, Inall ME, Ishii M, Ito S-i, Itoh S, Jan S, Kaiser J, Karstensen J, Kirkpatrick B, Klymak J, Kohut J, Krahmann G, Krug M, McClatchie S, Marin F, Mauri E, Mehra A, Meredith MP, Meunier T, Miles T, Morell JM, Mortier L, Nicholson S, O’Callaghan J, O’Conchubhair D, Oke P, Pallàs-Sanz E, Palmer M, Park J, Perivoliotis L, Poulain P-M, Perry R, Queste B, Rainville L, Rehm E, Roughan M, Rome N, Ross T, Ruiz S, Saba G, Schaeffer A, Schönau M, Schroeder K, Shimizu Y, Sloyan BM, Smeed D, Snowden D, Song Y, Swart S, Tenreiro M, Thompson A, Tintore J, Todd RE, Toro C, Venables H, Wagawa T, Waterman S, Watlington RA and Wilson D (2021) Corrigendum: OceanGliders: A Component of the Integrated GOOS. Front. Mar. Sci. 8:696100. doi: 10.3389/fmars.2021.696100 Corrigendum: OceanGliders: A Component of the Integrated GOOS

The Copernicus Marine service is a “one-stop-shop” providing freely available operational data on the state of the marine environment for use by marine managers, advisors, and scientists, as well as intermediate and end users in marine businesses and operations. The Copernicus Marine service offers operationally updated and state-of-the-art products that are well documented and transparent. The European Commission’s long-term commitment to the Copernicus program offers long-term visibility and stability of the Copernicus Marine products. Furthermore, Copernicus Marine offers a dedicated service desk, in addition to training sessions and workshops. Here, we present the in situ biogeochemical data products distributed by the Copernicus Marine System since 2018. It offers available data of chlorophyll-a, oxygen, and nutrients collected across the globe. These products integrate observation aggregated from the Regional EuroGOOS consortium (Arctic-ROOS, BOOS, NOOS, IBI-ROOS, MONGOOS) and Black Sea GOOS as well as from SeaDataNet2 National Data Centers (NODCs) and JCOMM global systems (Argo, GOSUD, OceanSITES, GTSPP, DBCP) and the Global telecommunication system (GTS) used by the Met Offices. The in situ Near Real Time biogeochemical product is updated every month whereas the reprocessed product is updated two times per year. Products are delivered on NetCDF4 format compliant with the CF1.7 standard and well-documented quality control procedures.

The Mediterranean community represented in this paper is the result of more than 30 years of EU and nationally funded coordination, which has led to key contributions in science concepts and operational initiatives. Together with the establishment of operational services, the community has coordinated with universities, research centers, research infrastructures and private companies to implement advanced multi-platform and integrated observing and forecasting systems that facilitate the advancement of operational services, scientific achievements and mission-oriented innovation. Thus, the community can respond to societal challenges and stakeholders needs, developing a variety of fit-for-purpose services such as the Copernicus Marine Service. The combination of state-of-the-art observations and forecasting provides new opportunities for downstream services in response to the needs of the heavily populated Mediterranean coastal areas and to climate change. The challenge over the next decade is to sustain ocean observations within the research community, to monitor the variability at small scales, e.g., the mesoscale/submesoscale, to resolve the sub-basin/seasonal and inter-annual variability in the circulation, and thus establish the decadal variability, understand and correct the model-associated biases and to enhance model-data integration and ensemble forecasting for uncertainty estimation. Better knowledge and understanding of the level of Mediterranean variability will enable a subsequent evaluation of the impacts and mitigation of the effect of human activities and climate change on the biodiversity and the ecosystem, which will support environmental assessments and decisions. Further challenges include extending the science-based added-value products into societal relevant downstream services and engaging with communities to build initiatives that will contribute to the 2030 Agenda and more specifically to SDG14 and the UN's Decade of Ocean Science for sustainable development, by this contributing to bridge the science-policy gap. The Mediterranean observing and forecasting capacity was built on the basis of community best practices in monitoring and modeling, and can serve as a basis for the development of an integrated global ocean observing system.

The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the world: (1) to observe the long-term physical, biogeochemical, and biological ocean processes and phenomena that are relevant for societal applications; and, (2) to contribute to the GOOS through real-time and delayed mode data dissemination. The OceanGliders program is distributed across national and regional observing systems and significantly contributes to integrated, multi-scale and multi-platform sampling strategies. OceanGliders shares best practices, requirements, and scientific knowledge needed for glider operations, data collection and analysis. It also monitors global glider activity and supports the dissemination of glider data through regional and global databases, in real-time and delayed modes, facilitating data access to the wider community. OceanGliders currently supports national, regional and global initiatives to maintain and expand the capabilities and application of gliders to meet key global challenges such as improved measurement of ocean boundary currents, water transformation and storm forecast.

The POSEIDON system is a comprehensive marine monitoring and forecasting system that progressively fills the gaps of observing facilities in the eastern part of the Mediterranean Sea. This system is expanding its various open and coastal sea infrastructure that includes fixed platforms, a cabled deep-ocean observatory, a FerryBox system, high-frequency (HF) radars, gliders, a calibration lab and Argos floats. Besides offering information to science and society, the POSEIDON system via its various platforms is also being used as a technology test-bed for numerous applications. The fields of technological test span from industrial application as material aging, advanced positioning systems, fuel cells technology, new sensor testing, to multiple scientific uses as carbonate system and fluorescence sensors, microplastics and pollutants sampling. These applications are summarized and selected examples are presented. The demand for access to POSEIDON infrastructures for technological tests has increased over the last years thanks to the transnational access activities coordinated by EU projects and is expected to further increase via a national research marine observing infrastructure initiated in 2018. The addition of new infrastructures planned for the near future will further enhance the technological test-bed possibilities and thus the interaction with other research institutions and the industry.

There is a general scarcity of oceanic observations that concurrently examine air–sea interactions, coastal–open-ocean processes and physical–biogeochemical processes, in appropriate spatiotemporal scales and under continuous, long-term data acquisition schemes. In the Mediterranean Sea, the resulting knowledge gaps and observing challenges increase due to its oligotrophic character, especially in the eastern part of the basin. The oligotrophic open Cretan Sea's biogeochemistry is considered to be representative of a greater Mediterranean area up to 106 km2, and understanding its features may be useful on even larger oceanic scales, since the Mediterranean Sea has been considered a miniature model of the global ocean. The spatiotemporal coverage of biogeochemical (BGC) observations in the Cretan Sea has progressively increased over the last decades, especially since the creation of the POSEIDON observing system, which has adopted a multiplatform, multivariable approach, supporting BGC data acquisition. The current POSEIDON system's status includes open and coastal sea fixed platforms, a Ferrybox (FB) system and Bio-Argo autonomous floats that remotely deliver fluorescence as a proxy of chlorophyll-a (Chl-a), O2, pH and pCO2 data, as well as BGC-related physical variables. Since 2010, the list has been further expanded to other BGC (nutrients, vertical particulate matter fluxes), ecosystem and biodiversity (from viruses up to zooplankton) variables, thanks to the addition of sediment traps, frequent research vessel (R/V) visits for seawater–plankton sampling and an acoustic Doppler current profiler (ADCP) delivering information on macrozooplankton–micronekton vertical migration (in the epipelagic to mesopelagic layer). Gliders and drifters are the new (currently under integration to the existing system) platforms, supporting BGC monitoring. Land-based facilities, such as data centres, technical support infrastructure, calibration laboratory and mesocosms, support and give added value to the observatory. The data gathered from these platforms are used to improve the quality of the BGC-ecosystem model predictions, which have recently incorporated atmospheric nutrient deposition processes and assimilation of satellite Chl-a data. Besides addressing open scientific questions at regional and international levels, examples of which are presented, the observatory provides user-oriented services to marine policy makers and the society, and is a technological test bed for new and/or cost-efficient BGC sensor technology and marine equipment. It is part of European and international observing programs, playing a key role in regional data handling and participating in harmonization and best practices procedures. Future expansion plans consider the evolving scientific and society priorities, balanced with sustainable management.

Oil spills in the ocean are a matter of concern due to the damaging effect they can have on coastal and offshore resources. This work presents a review of present-day modeling techniques used in the mitigation of oil spills by booms, skimmers, chemical dispersants, and other equipment and the importance of the controlling parameters of these techniques. Three basic questions need to be addressed by oil spill models: (1) where the spill will move, (2) when will the spill get to the modeled endpoints, and (3) what will be its state when it arrives. The first two questions are relatively urgent, as far as response measures are concerned, and depend closely on the use of accurate data on winds, sea currents, and wave action as oil spill accidents evolve. Obtaining a reasonable answer to the third question lies in the use of reliable fate algorithms. Oil spill models can be divided in two types: Euleurian and Langragian. Adding to information regarding the oil type and its initial location, all oil spill models require data for the wind fields, sea state, sea-surface temperature, and currents, as well as other environmental parameters, if available. Such reliable data suit the needs of oil spill modeling predictions and are available daily at global, regional, and coastal scales within the broader scope of operational oceanography. Advanced oil spill models available at present use satellite synthetic aperture radar (SAR) images/data to detect possible oil slicks and assimilate slick and drifter observations to correct slick predictions. The emphasis of research and governmental institutions has been on improving 4D predictions obtained through simulation of oil spills backward in time to track the slicks back to their source. Such backward simulations, when integrated with ships' Automatic Identification Systems (AIS), will be used to locate the sources of oil slicks around the world's oceans and seas.