Coastal regions are dynamic, complex systems where multiple physical, biological, and chemical processes interact across various spatial and temporal scales. The areas are also characterized with high connectivity. Effective monitoring of these systems requires a holistic and integrated approach that combines advanced environmental modeling with monitoring techniques to provide a comprehensive understanding of estuarial-coastal ecosystems. This study aims to assess if existing estuarial-coastal observing system fit for the purpose of resolving high connectivity and multi-scale processes, identify gaps and make recommendations. This work consists of three studies: the first one is to assess current estuarial-coastal observation and modelling capability in the EU member states, and identify gaps and make recommendations; the second one is to further review current monitoring and modelling capability in resolving Baltic-North Sea connectivity in the transition waters, with focus on carbon observations; the third study focuses on fit-for-purpose information for offshore wind energy, its user needs and potential solutions, current monitoring and modelling capacity, gaps and recommendations.

National observation and modelling capability in estuarial-coastal continuum – assessment and gap analysis:
This study identifies gaps in monitoring systems run by six European countries. The monitoring capacity in this study represents an integrated capacity by combining in-situ, remote sensing and modelling. The gaps in the monitoring capacity were identified to fit for the purposes in key service sectors, i.e., ocean health, climate change, operational forecast and blue economy. Naturally, the focus of the observing systems not only differs between different countries, but also depends on the institutions running the monitoring systems. The project partners responsible for this document represent a mix of operational centers and research institutions and thus provide a quite wide range of different perspectives.

DMI investigated Danish marine monitoring capacities in national waters, including i) observing capacities, both in-situ and remote sensing, in operational agencies, coastal authority, environment agency and part of observing capacities from Fishery monitoring, research community and commercial companies, ii) modeling capacity, consisting of models for operational forecasting, coastal erosion, climate change adaptation, biogeochemical and lower trophic level models, high trophic level models and models for commercial applications, as well as data assimilation capacities wherever relevant. The existing monitoring capacity is reviewed and gaps are identified to fit for the purposes of information services for operational activities, climate change adaptation and ocean health.

FMI analyzed information on Finnish marine observing platforms, modelling and remote sensing. The focus is on operative observations and modelling, and the research activities listed here are carried out mainly by the Finnish Meteorological Institute (FMI) and Finnish Environmental Institute (SYKE).

HEREON reviewed existing in-situ and remote sensing and modelling (including data assimilation) capacity in Germany, and identified correspondent gaps on the particular case of offshore windfarming, which is very illustrative and currently of extremely high relevance in Germany. This application is useful as a demonstrator because it demands information on a wide range of spatial and temporal scales as well as across various disciplines (physics, chemistry, biology).

Deltares focuses on monitoring for eutrophication assessments in the context of OSPAR and MSFD. In 2020 and 2021 the methodology for eutrophication assessments has been revised, using:
- New assessment areas
- New threshold levels and
- Addition of satellite data to complement in-situ observation data for chlorophyll-a.
In the process of revising the methodology for eutrophication assessments, several limitations in the currently available observation data have been encountered.

IMR study covers the Norwegian marine monitoring activities within the territorial waters. The monitoring gaps are identified to serve the purpose of holistic national management plans for their regions in Norway since the beginning of the 2000s.

SOCIB investigated data needs and gaps in the northwestern Mediterranean Jerico-S3 Pilot Super Site where the Italian, French and Spanish monitoring systems are used to reconstruct the 3D dynamics and describe the regional and coastal circulation in the region. In this area, the Northern Current flowing along the slope from Italian to French and Spanish waters is an essential driver of the regional connectivity. Its path, extent and strength have a significant impact on the transport of materials, contaminants, plastics or fish larvae within the region. The WMOP hydrodynamic modelling system developed at SOCIB is used to integrate the maximum number of transnational observations together with modelling tools through data assimilation. A preliminary gap analysis of the regional
monitoring and modelling systems is presented. Although there are differences in the gaps identified in different cases, come common gaps can be identified:
● Need more frequent T/S and BGC profile observations
● Need better BGC data coverage in space
● to integrate observations between operational and non-operational observing sectors
● to improve NRT in-situ data delivery in non-operational observing sectors
● to increase use of coastal observations in modelling via model-observation integration, including assimilation, tuning model parameters, model calibration and validation, hybrid modelling using AI/ML with model data and observations
● to increase use of integrated monitoring and forecast products in non-operational services
Observations for resolving Baltic-North Sea connectivity:
In this study, connectivity of water, nutrients, carbon and pollutants are qualitatively analyzed, observing strategy in the Baltic-North Sea transition waters to improve the understanding and prediction of the connectivity is recommended. A more detailed observation gaps analysis on carbon connectivity is also given. Gaps in monitoring capacity for Baltic-North Sea connectivity are identified in following areas:
● Lack of in-situ pCO2, DOC/POC profiles and microplastic measurements in Kattegat
● Lack of high frequency profile observations for currents (hourly) and T/S (synoptic scale) for calibration and validation (cal/val), and biogeochemical variables (synoptic scale) for both cal/val and assimilation in Kattegat
● Integration of existing monitoring capacities, both in national and regional level, are essential. Such integration includes, but is not limited to,
o to share observations between operational and non-operational observing sectors
o to improve NRT in-situ data delivery in non-operational observing sectors
o to increase use of coastal observations in modelling via model-observation integration, including assimilation, tuning model parameters, model calibration and validation, hybrid modelling using AI/ML with model data and observations
o to increase use of integrated monitoring and forecast products in non-operational services
o Robotics are prospective instruments in the Baltic-North Sea transition waters: AUV for both shallow (<30 m deep) and deep waters (>30 m deep), sail drones for surface and gliders for the deep waters.
Fit-for-purpose information for offshore wind energy:
The rapid expansion of offshore wind farms (OWFs) in European seas is accompanied by many challenges, including efficient and safe operation and maintenance, environmental protection, and biodiversity conservation. Effective decision-making for industry and environmental agencies relies on timely, multi-disciplinary marine data to assess the current state and predict the future state of the marine system. Due to high connectivity in space (land–estuarial–coastal sea), socioeconomic (multi-sectoral and cross-board), and environmental and ecological processes in sea areas containing OWFs, marine observations should be fit for purpose in relation to multiple OWF applications. This study represents an effort to map the major observation requirements (Part-I), identify observation gaps, and recommend solutions to fill those gaps (Part-II) in order to address multi-dimension challenges for the OWF industry. In Part-I, six targeted areas are selected, including OWF operation and maintenance, protection of submarine cables, wake and lee effects, transport and security, contamination, and ecological impact assessments. For each application area, key information products are identified, and integrated modeling–monitoring solutions for generating the information products are proposed based on current state-of-the-art methods. The observation requirements for these solutions, in terms of variables and spatial and temporal sampling needs, are therefore identified. These application areas show many examples of spatial and interdisciplinary connectivity between different types of observation data required for different applications. A fit-for-purpose observation requirement assessment approach is used first to identify user needs on key information products, then to suggest an integrated modeling–monitoring solution for deriving the information products, and finally, to identify observation demands with regard to the use of observations in implementing the solutions. The results should show that demands from governmental stakeholders, OWF operators, and the research community can only be fulfilled by multi-scale and multi-disciplinary observations and dedicated monitoring–modeling integration. In addition, several important issues such as multi-use of OWF platforms, Model-Observation Integration in Areas with High Connectivity and Multiple Scales, Coordinated Data Management for OWF Applications, and Data Transmission, Interoperability, and Accessibility are also discussed. In Part-II, A gap analysis was presented for observation systems and respective integrations with numerical models in the context of fit-for-purpose information products required in the offshore wind energy sector. The study is the second part of two papers, with the first one concentrating on the identification of requirements for six use cases. It was explained that gap analysis is a powerful tool to optimize decision processes by enforcing the development of clear ideas about target scenarios and the transparent assessment of the initial situation. The study also discussed the challenges of applying this tool in the context of offshore wind energy. One key challenge is the balancing of economic and environmental target definitions because this includes discussions about values and ethical aspects that require a broader discussion in society, i.e., this is not a purely scientific issue. The study provided an overview of the monitoring and modeling solutions that are presently used to provide information products for the offshore wind community. It became quite clear that the observation and model systems used today have evolved due to requirements associated with a number of standard applications, e.g., storm surge forecasts or wave predictions for shipping. It also appeared that the monitoring of ecosystem parameters is less mature than respective systems for the measurement of physical quantities. By comparing the present situation with the requirements identified in [8], gaps were identified, which were structured along different categories, e.g., spatial and temporal sampling or data availability and accessibility. Many of the identified gaps have to do with the fact that the existing monitoring systems are not adequate to capture characteristic length scales of today’s offshore wind farms, e.g., related to the spacing of turbines. This means that different types of wake effects and turbine impacts on the environment cannot be assessed appropriately with the available observations. In addition, OWFs create new types of physical, chemical, and biological processes, which are not captured by the present monitoring systems at all, e.g., the generation of turbulence by turbine structures in the water and the atmosphere. Furthermore, it was discussed that most of the fit-for-purpose information products for the offshore energy sector have to include various types of connectivity aspects, e.g., the continuum of land, wind farm, and open ocean spatial scales. Likewise, the treatment of most optimization problems occurring in offshore wind farming requires detailed knowledge about interaction processes between different earth system compartments, e.g., the atmosphere, the ocean, the sea floor, and the ecosystem. There is still a lack of suitable measurements for this purpose, although information about these coupling mechanisms is also highly relevant in other contexts, e.g., climate change. There are also still observations missing to identify, understand, and predict two-way interactions between the technology and the environment. This has become increasingly challenging because of the rapid development of OWF installations in terms of turbine size and OWF coverage. It was also found that with regard to temporal sampling, a measurement strategy is missing to assess the environmental conditions before and after windfarms were installed. The issue is of growing urgency since locations not impacted by OWFs are increasingly hard to find. A number of recommendations to fill the gaps were formulated. These include different technological aspects, e.g., autonomous systems like drones, but also suggestions concerning data policies and cooperation between science and industry. Due to the large-scale interactions of OWFs with the environment and also among each other, the development of measurement strategies across country borders was identified as an essential step forward. It is foreseeable that this step will also be of vital importance for a further synchronization and optimization of the energy system on a larger scale, e.g., across Europe. Another important recommendation concerns the exploitation of synergies by identifying common interests and requirements in different communities and sectors, e.g., the OWF community and operational forecast centers. Finally, it is important to emphasize that this study is meant as a contribution to a discussion, which needs to be continued and extended. The task at hand is challenging not only because of the complexity and the rapid evolution of technology but also because of the diversity of the different communities that have to be brought together to find suitable solutions for the future. The experience in the past has shown that the respective communication and synchronization processes take time and that makes a structured and transparent approach even more important.