A team of scientists from four countries have set out on a maritime journey to discover what colour the Atlantic Ocean is.
They want to find out the impact of misty clouds of aerosol particles hanging above the water on algae that are the foundation of the marine food chain.
Around a third of the carbon dioxide free into the atmosphere by human activities is engrossed by microscopic algae in the sea.
This process gives the waters a greenish shade as algae blooms close to the surface thrive.
But satellite images in recent years have shown large aerosol clouds forming above the oceans, chiefly in the southern part of the Atlantic.
They increase the amount of the sun's rays reproduced away from the sea, reducing the amount of algae and therefore decrease the water's greenish hue.
The project engages scientists from Brazil, Argentina, France and the US currently aboard the Melville, a research vessel belonging to the Scripps Institution of Oceanography in San Diego.
The teams hope to gain more accurate measurements of what is happening than those taken from satellites that may be indistinct by strong winds or waves.
Milton Kampel, the National Institute for Space Research (INPE) in Brazil, said: "[The satellite] concentrations have not yet been long-established with field data. We need to see, for example, this is not an effect caused by breaking waves at sea."
They are also taking water samples to study the result on algae.
The Melville left Cape Town in late February and is scheduled to arrive in Valparaiso, Chile, next week.
