February 7, 2008

Scientists Chase Saharan Sand Around the Globe

A team of scientists are set on finding out how sand from the Sahara Desert is affecting marine life, as well as learning more about the ocean's ability to soak up the greenhouse gas carbon dioxide.

The researchers encountered two large sand storms during their cruise and recorded footage for BBC News.

Eric Achterberg, principal scientist for the Natural Environment Research Council (Nerc) funded Solas (Surface Ocean Lower Atmosphere Study) expedition, said he was relieved to have encountered dust storms during the one-month cruise, after having failed to find Saharan sand during an expedition 2 years ago.

He told the BBC: "We encountered two dust storms: one lasted for about three days, the other was a big one that lasted for about four to five days."

"We were on top of the ship, you could just see it coming - there was a wall of dust coming towards us and it got very hazy after that. The ship was covered in dust - it was just fantastic.

About 1,700 million tons of dust is produced by deserts each year, and about one third of this falls into the oceans. The North Atlantic Ocean receives the most of this dust due to being close to the Sahara Desert.

Dr Achterberg, who is from the National Oceanography Centre, Southampton, explained: "The dust releases nutrients to the ocean. If these organisms grow, they take up more carbon dioxide and remove it from the atmosphere," he said.

"If we understand how the dust functions here, we will have a better idea of how the ecosystem in the North Atlantic takes up carbon dioxide, how quickly it takes it up and how this changes over time."

Aboard U.K. research ship RSS Discovery, the international team of 28 scientists and technicians set off from Tenerife on 5 January. Scientists used satellite images provided by Neodaas (Nerc Earth Observation Data Acquisition and Analysis Service) in order to track wind patterns make predictions about the direction of the storms.

Each time they encountered a dust storm, a range of scientific experiments would commence to find out how the Saharan sand was influencing the ocean's chemistry and biology.

What they found was that sand was affecting the growth of the nitrogen-fixing bacterial organism Trichodesmium.

"These organisms require a lot of iron, which is supplied by the dust," Dr Achterberg said.

He said that the primary goal of the expedition was to study the relationship between carbon dioxide, dust and marine life, but that they were also looking at the affects of climate change on the desert.

A recent report suggests that increases in rainfall levels could make deserts greener, while other studies support the idea that they will grow in size in some regions, according to BBC News. Either way, the amount of sand falling into the oceans around the world could change.

Dr Achterberg said: "We want to ask: 'If the dust levels were increased, what effects might have in the ocean?'"

"And we can do this by collecting dust, looking at its chemistry, looking at its biology. Our project is the first real look at how dust is affecting our oceans."


On the Net:

Video: Sand storm at sea is captured on film

Video: The mission explained

Natural Environment Research Council

National Oceanography Centre