Chasing sandstorms at sea

9 March 2006

How do Saharan sandstorms feed Atlantic ocean life? Intrepid environment scientists are braving wind and waves to unravel the mysterious effects of desert dust as it falls from the sky and sinks into the sea.

Antenna dives deeper...

This map shows concentrations of dust in the atmosphere. Highest concentrations appear red.

Image: modified from Mahowald and Jickells

How does desert dust affect the ocean's ecosystem?

Scientists have joined forces to find out - chasing storms in a jet aircraft, and tracking the effects of the dust in a floating lab.

This satellite image shows a Saharan dust cloud above the Atlantic ocean.

Image: NASA

'We're interested in finding out how the ocean and atmosphere interact. Dust storms have effects on both what goes into, and comes out of, the ocean.'
Phil Williamson, environmental scientist, University of East Anglia

Phil Williamson, environmental scientist, University of East Anglia

In a specially equipped jet, high-flying scientists use satellite forecast models to predict where dust storms are heading. Then they fly through the storms, frantically taking measurements.
'We fly against the wind into the storms first, and then chase around and fly back underneath. Probes on the plane sample the dust at different heights and take it back to the lab for analysis.'
Ellie Highwood, atmospheric scientist, University of Reading

Ellie Highwood, atmospheric scientist, University of Reading

What else do the planes measure?
'Clouds of Saharan dust reflect sunlight back into the sky, lowering the temperatures of ocean and land. We use radiometers to measure how much sunlight gets reflected.'
Ellie Highwood

The research plane is a BAE 146, specially equipped with probes and radiometers to sample the dust clouds.

Image: BAE Systems

Meanwhile, aboard their ship Poseidon, the sea-faring scientists sample the sea water to see how the ocean changes during a dust storm.

The research ship Poseidon.

Image: Micha Rijkenberg

'Dust falls into the sea during storms, and nutrients dissolve from the dust into the seawater. This fertilises the ocean, and feeds tiny plants called phytoplankton living near the surface.'
Eric Achterberg, oceanographer, National Oceanography Centre, Southampton

Broadband Version

Watch this video and meet the scientists who have braved the elements aboard the Poseidon.

Video: Science Museum, The National Oceanography Centre, University of Southampton, Mark Stinchcombe, University of East Anglia, BAE Systems

How can desert dust help sea life thrive?
The dust delivers vital nutrients such as iron to the organisms living in remote and barren parts of the oceans.

Phytoplankton, like this one, live in the sunlit upper ocean.

Image: Alex Baker

'If the tiny plants like phytoplankton grow better, they take up more carbon dioxide. When they die, some of this carbon gets carried to the bottom of the sea, removing it from the atmosphere for thousands of years.'
Eric Achterberg
Carbon dioxide is a greenhouse gas, so what does all this mean for climate change?
'More dust reaching the ocean should mean more carbon dioxide taken out of the atmosphere, so that might put a natural brake on global warming. But no one can tell yet how important this effect will be.

Satellite image of Saharan dust moving across the Atlantic.

Image: Copyright 2004 EUMESAT

'Some regions might get drier and dustier, whilst others might be wetter. The best climate models don't have the answers yet.'
Phil Williamson
But swirling Saharan sandstorms already affect extreme weather, and this new research might help us to understand and predict potential disasters.
'The hurricanes that created havoc in the US last year originate in the Cape Verde region where we have been hunting for dust storms. Research has shown that high dust concentrations in this region reduce the likelihood of hurricanes forming.'
Eric Achterberg

Hurricane Katrina tears across the Atlantic ocean.

Image: NASA

Cape Verde's beautiful sunsets are down to the dust clouds too. Desert dust scatters blue light, leaving only red light to reach you - with breathtaking results.