Stopping the spread of global warming may be as simple as salting the world's oceans with iron dust.

That's a global science experiment a SAD 44 seventh-grade science teacher from Bethel and a Maine college professor will tackle this month and next while on a 28-day cruise with other scientists in the northwest Pacific's subarctic.

Bill Caddigan of Telstar Junior High and Mark Wells, a University of Maine at Orono oceanographer, are aboard the research vessel Thomas G. Thompson, a U.S. Navy ship operated by the University of Washington.

The ship left Seattle, Wash., on May 12, cruising northward along the British Columbia coast toward the Queen Charlotte Islands.

From there, it turns offshore and moves into the central north Pacific, heading for Ocean Station P to perform oceanographic research on trace metal interactions with phytoplankton, according to marine education associate Abigail Manahan at the University of Maine's School of Marine Sciences in Walpole.

Phytoplankton are microscopic plants that live in the ocean, are eaten by small fish and some whales, and can influence Earth's climate, according to NASA's Earth Observatory Web site.

The iron feeds phytoplankton, which use carbon dioxide for photosynthesis. The experiment's premise is that the larger the phytoplankton population, the more carbon dioxide gets sucked out of the atmosphere and sinks to the ocean bottom, according to NASA.

Wells made the North Pacific trip in 2004 to study the physical and chemical factors that control phytoplankton.

But this is Caddigan's first time, thanks to the National Oceanic and Atmospheric Administration's Teacher at Sea program, which began in the 1990s.

Under Wells' supervision, Caddigan's duties aboard the Thompson will include assisting with the scientific tasks and objectives of the researchers. He will also be teaching about 85 middle school students in his four science classes via the Internet, something that has yet to be worked out due to the four-hour time difference and bandwidth problems, Telstar Middle School Principal Russell Tornrose said Tuesday in Bethel.

"Right now, it's not working in real time unless they have the ship stopped," he added.

As part of the Teacher at Sea program, Caddigan must also contribute to and maintain a daily blog or Web site diary that will highlight life aboard ship and the science being practices.

Neither Wells nor Caddigan could be reached for comment. Wells stated Wednesday morning in an e-mail that they've both been very busy getting experiments under way.