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Maritime Forum

Map of the week - Satellite and In Situ Observations for Advancing Ocean Monitoring

In this map of the week, we invite you to compare the satellite-based output with corresponding field-monitoring data on chlorophyll-a concentrations.

Once thought to be a vast, resilient area able to absorb practically unlimited waste, the ocean is currently subject to overuse, loss of resilience and increased vulnerability. Waters that lie above the continental shelf are coastal ocean, representing a frontline in the battle for sustainability. It is home to more than 90% of all marine organisms and complex ecological processes take place through the interaction of terrestrial, aquatic, atmospheric, and human landscapes. Highly dynamic as it is, coastal ocean faces unprecedented challenges to allow socio-economic development while sustaining the ecological and protective functioning.

A Decade of Ocean Science for Sustainable Development (2021–2030) was called to support the UN 2030 Agenda for Sustainable Development and associated Sustainable Development Goals (SDGs). To achieve the vision of a well-functioning, productive, resilient, and sustainable ocean, more open access data, increased knowledge, advanced predictions of the coastal ocean are required[1]. Coastal zone monitoring is essential to pave the way for sustainable use of marine resources to ensure the continuity for future generations.

There are two ways to monitor coastal issues, i.e. satellite data and field monitoring. Remote sensing using satellite sensor systems has been applied on large spatial scales with high temporal resolutions to assess long-term changes for nearly 40 years. Complementary to satellite observations, in-situ observation can capture the level of resolution and provide additional, specific information in many cases satellites cannot. Thus, satellite observation is highly dependent on in-situ observing capabilities for validation and assimilation. The complementation, interconnection, and interdependence between in-situ observations and satellite remote sensing are like Yin and Yang in Ancient Chinese Philosophy. Together they need to be viewed as an integrated system to provide observational data required by monitoring coastal issues.

In this map of the week, we invite you to compare the satellite-based output with corresponding field-monitoring data in European Atlas of the Seas. We use a water quality index Chlorophyll a, the most commonly used parameter for monitoring phytoplankton biomass and nutrient status, as an example. The map on top provided by Copernicus shows monthly global surface ocean Chlorophyll-a concentration. This large-scale satellite based map provides a global view, although at regional scale limitations remain such as low spatial resolution of sensor systems, the optical complexity of coastal waters, unavailability to assess the total amount of phytoplankton present at all water depths and the composition of phytoplankton communities. These are complemented by in situ observation that captures high spatial resolution at regional scale and multiple depth levels. The map provided by EMODnet Chemistry, is an interpolation of the Chlorophyll-a concentration from in-situ measurements performed at multiple depths, in the summer of 2010 (other seasons are also available).

The force arising from the interplay between yin and yang create harmony; similarly, EMODnet and CMEMS (Copernicus Marine Environment Monitoring Service) give rise to each other. To improving access to marine data and data products and information on coastal behaviour, EMODnet and CMEMS met earlier this week to discuss the existing capabilities and emerging areas for collaboration with a regional focus. Great progress has been made towards this direction. CMEMS In-Situ Thematic Assembly Centre provides products based on satellite & in-situ observations and state-of-the-art data fusion techniques. EMODnet Seabed Habitats published broad scale EUSeaMap to support the Marine Strategy Framework Directive. EMODnet Geology[2] published pan-European coastline-migration map layers based on satellite data 2007-2016. The usefulness of the resulting data is discussed in ‘The state of the world’s beaches[3]. With this reinforced partnership EMODnet-CMEMS, we hope to advance the frontiers of ocean observing capacity, provide solutions for the management and sustainable exploitation of the coastal resources and achieve effective and future change-proof sustainable management of coastal zones.

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The data in this map were provided by CMEMS and EMODnet Chemistry.

[1] IOC-UNESCO, “The Science we need for the ocean we want: the United Nations Decade of Ocean Science for Sustainable Development (2021-2030)” (2019).


[3] Luijendijk, A., Hagenaars, G., Ranasinghe, R. et al. The State of the World’s Beaches. Sci Rep 8, 6641 (2018).