Monitoring ocean colour

The Ocean and Land Colour Instrument (OLCI) on board the Sentinel-3A satellite (launched in February 2016) delivers vital information about the biological and biogeochemical activity of aquatic ecosystems.

Monday, 09 April 2018

Thumbnail - Sentinel-3 Launch - Ocean Colour

In April 2018, Sentinel-3B will be launched, to be operated in tandem with Sentinel-3A for optimum global coverage.

Sentinel-3A and –B form part of the fleet of Earth Observation satellites central to the European Union’s (EU) Copernicus Programme.

EUMETSAT operates the Sentinel-3 satellites on behalf of the EU and delivers the marine mission.

Ocean Colour data can be used for a wide variety of purposes. They can help to track and forecast harmful algal blooms, which can endanger humans, marine or freshwater life and aquaculture. These data also support the monitoring of coastal water quality, by tracking eutrophication, nuisance blooms, sedimentation and erosion.

Ocean colour data are also of a truly global importance as they help monitor climate change: ocean colour is one of the so-called Essential Climate Variables (ECV) listed by the World Meteorological Organization that help detect changes in biological activity in the ocean’s surface layer.

Ewa Kwiatkowska, EUMETSAT Remote Sensing Scientist explains: “Phytoplankton take up carbon dioxide (CO2) during photosynthesis, making the ocean the most important carbon sink. Alternatively, ocean colour data can be used to monitor the annual global uptake of CO2 by phytoplankton on a global scale.”

Observations of ocean colour support many industries, including fisheries and aquaculture, because of the phytoplankton role at the base of the aquatic food chain. They also support studies of the Earth system, for instance through monitoring El Niño/La Niña events and their impacts on ocean living ecosystems.

She added: “Ocean colour data can aid reporting obligations of the European Union's legislation within Marine Strategy Framework Directive and Water Framework Directive, the goal of which is to achieve or maintain Good Environmental Status of the seas by the year 2020.”

"Harmful outbreaks of algal bloom, require constant and consistent monitoring and forecasting"

To ensure a steady flow of these vital data, two Sentinels are a must as Kwiatkowska explains.

“Harmful outbreaks of algal bloom, require constant and consistent monitoring and forecasting from the OLCI instrument. With a cloud cover and gaps in coverage between successive orbits, there could be a discontinuity in the observations – with possibly detrimental effects.

She continued “Also, there is a need to time phytoplankton blooms for ecosystem forecasts and to detect trends in eutrophication, where water body gets over-enriched with an excess amount of nutrients. This process induces growth of plants and algae and due to the biomass load, may result in oxygen depletion of the water body.”

Kwiatkowska is looking forward to the launch of Sentinel-3B.

“It will be certainly exciting to see both missions in orbit, which will give us the much- needed increased spatial coverage. Even more exciting will be to see the users benefitting from the Copernicus Sentinel-3 dual mission data and come up with even more operational applications and services from those measurements.”

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