Approximately 50% of the oxygen we breathe comes from the ocean, where algae not only release oxygen during photosynthesis, but also serve as the base of most oceanic food webs. Since satellites can measure the different wavelengths of light that are absorbed by the planet surface and reflected back to space, scientists can use that data to calculate how much green pigment associated with the algae is contained in the surface waters. Chlorophyll pigment strongly absorbs red and blue wavelengths of light and reflects green. Data from the NASA SeaWiFS, NASA Aqua and NASA/NOAA Suomi NPP satellites have been used by NOAA to monitor oceanic chlorophyll concentration (also called ocean color) since 1997. This data has been instrumental in understanding global productivity, carbon cycling, fisheries habitats, and biochemical oceanography.
In this imagery, areas of the ocean with lower amounts of surface chlorophyll are colored blue, areas with higher concentrations are colored green to yellow. The large patches of gray are areas where the satellite cannot measure the ocean surface due to cloud cover. The areas of gray over the poles during their respective winters is due to the lack of sunlight in those regions. This real-time dataset is updated monthly and frames from the last year are included. In this year long loop, seasonal variations can be seen.