Sentinel-3

Ocean Colour

About the OLCI

Thumbnail - Sentinel-3 Launch - Ocean Colour

The Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3 will observe in 21 narrow spectral bands of the visible and near infrared spectrum at a resolution of 300 metres.

With a swath width of 1270 km and five tilted cameras, which are specially optimised to reduce sun glint, the ocean and land colour instrument will provide improved global coverage of ocean colour - in less than 2 days with two Sentinel-3 satellites in operation.

It will expand the medium resolution ocean colour measurements collected by Envisat’s MERIS instrument (2002-2012).

Last Updated:  Monday, 11 January 2016

What affects the colour of the oceans?

The main influence on the colour of the oceans in “clear” waters is the phytoplankton, the microscopic marine plants that form the basis of the marine food chain.

Fig.1

Like plants on land, phytoplankton use chlorophyll and other light-harvesting pigments to carry out photosynthesis, converting water and carbon dioxide into new organic material and oxygen – in the process generating half the oxygen in the atmosphere.

The chlorophyll in the water changes the way it reflects and absorbs sunlight, allowing scientists to map the amount and location of phytoplankton.

In general, the greater the concentration of phytoplankton, the greener the waters will appear, while in contrast, if little phytoplankton is present then the water will appear blue.

Ocean colour measurements from space provide global monitoring of phytoplankton giving scientists valuable insights into the health of the aquatic environment and the global ocean carbon cycle.

In coastal areas, runoff from rivers, suspension of sand and silt from the seabed by tides, waves and storms and a number of other substances can change the colour of the near-shore waters.

How is ocean colour data used?

Ocean colour provides a window into the ocean ecosystem and can be used to:

Fig.1
  • Track and forecast harmful algal blooms that are a danger to humans, marine/freshwater life and aquaculture.
  • Monitor coastal water quality.
  • Guide marine resource management, for example fisheries.
  • Monitor climate change – ocean colour is one of the so-calledEssential Climate Variables  listed by the World Meteorological Organization to detect biological activity in the ocean’s surface layer. In addition phytoplankton take up carbon dioxide (CO2) during photosynthesis, making them important carbon sinks. Ocean colour data can be used to monitor the annual global uptake of CO2 by phytoplankton on a global scale.
  • Monitor global ocean primary production.
  • Track sediment transport in coastal areas.
  • Study the Earth system, for instance monitoring EL Nino/La Nina and impacts on the ocean ecosystem.
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