Last month the first results emerged from the long-awaited remote Earth-sensing instrument, SeaWiFS (the Sea-viewing Wide Field-of-view Sensor), which is designed to monitor the colour of the oceans. Ocean colour data provide a means to investigate the abundance of phytoplankton, suspended sediments and organic materials in the surface ocean.

The viability of using satellite-based instruments to measure ocean colour was established over a decade ago. But although the Coastal Zone Color Scanner (a forerunner to SeaWiFS, which operated between 1978 and 1986) provided some information on biological productivity, the data lacked crucial spatial and temporal coverage.

SeaWiFS boasts global coverage every two days, higher sensitivity to visible light, and an improved capability to ‘see’ through the atmosphere. Moreover, some of the SeaWiFS images (as shown here) convey land-vegetation information as well as data on oceanic chlorophyll concentrations (which are lowest in the purple regions, and higher in the green sea areas).

Studies of ocean colour also have potentially wider social and economic implications. The ability to find pockets of high phytoplankton density, for example, could help in the management of fish stocks. Moreover, SeaWiFS can keep a watchful eye out for harmful blooms of coastal algae, which have been linked to outbreaks of human disease.

Credit: nasa/gsfc