Satellite technologies that measure ocean colour help measure the water-leaving radiance, which is the light that is reflected by the sea. This radiance results from the interaction of sunlight with optically significant constituents - particles that are suspended or dissolved in seawater. Thus, the water-leaving radiance gives information on the properties of the water body and the biological activity beneath the sea surface.
For example, ocean regions with high concentrations of phytoplankton have shades of blue-green depending upon the type and density of the phytoplankton population there. This is because phytoplankton, which uses chlorophyll to remove carbon dioxide from the atmosphere through photosynthesis, highly absorbs light in the blue spectral region.
The Sentinel-3A and -3B satellites of the EU Copernicus Earth Observation Programme are specifically designed to provide information on optically significant constituents of seawater at the global scale. This satellite-derived information, however, requires regional verification in order to quantify uncertainties and, when necessary, to develop new bio-optical algorithms that help generate more accurate Earth observation products.
Within this general context, JRC scientists participated in an oceanographic campaign in sub-Artic regions of the Greenland Sea and in Arctic regions of the Barents Sea in June. The campaign, organised by the NATO Centre for Maritime Research and Experimentation and carried out onboard the Research Vessel Alliance, allowed for the collection of comprehensive in situ data to validate satellite ocean colour products.
These data will help assess Sentinel-3 data products such as phytoplankton chlorophyll a, non-living particles and coloured dissolved organic matter, which are of utmost importance for a comprehensive investigation of biological processes in seas, and essential for monitoring changes in a very climate-sensitive region such as the Arctic.