Satellite Data May show Hurricanes’ Effect on Global Climate

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A team of U.S. scientists hopes to build on its previous satellite imagery research to determine whether hurricanes leave behind more or less atmospheric carbon dioxide , a factor that could play into predictions of global warming.

In a previous NASA-funded study, the scientists used ocean color readings from the Sea-viewing Wide Field of View Sensor (SeaWiFS) on Orbital Science Corp.’s OrbView-2 spacecraft to show how phytoplankton algae proliferated in the cold, nutrient-rich waters that were produced in the aftermath of 13 hurricanes that crossed the Atlantic Ocean between 1998 and 2001.

The National Science Foundation (NSF) and NASA are considering separate proposals from the team for an expanded study. The scientists would use a mathematical model to try to measure the net effect of hurricane-induced phytoplankton blooms on levels of airborne carbon dioxide in the wakes of hurricanes.

The scientists would study archived satellite data and buoy readings for hurricanes that crossed the Atlantic in 2002, 2003 and 2004, and continue the study through the 2005, 2006 and 2007 hurricane seasons using new SeaWiFS imagery and buoy readings to capture the state of the sea before and after the storms.

Steven Babin of John’s Hopkins University’s Applied Physics Laboratory in Laurel, Md., would lead the study and work closely with ocean-modeling expert Jerry Wiggert of Old Dominion University of Norfolk, Va., and ocean-buoy expert Tommy Dickey of the University of California, Santa Barbara.

The team initially requested $300,000 from NASA in 2004 for the expanded study through the agency’s three-year, $16 million interdisciplinary Oceans and Ice research program. NASA managers had planned to announce winners of that competition in October 2004, but a delay in the congressional budget appropriation and an ensuing internal budget review at NASA forced managers to delay the awards.

The hurricane team submitted a backup proposal to the National Science Foundation in February and informed NSF about the proposal that was pending at NASA, Babin said.

NASA’s Jack Kaye, director of the research and analysis program under NASA’s Earth-Sun System Division, said the agency was preparing to inform the competitors of the agency’s selections, which Kaye said would be made public soon.

In terms of overall funding for the Oceans and Ice program, Kay said “I’m quite hopeful we’ll be right at where we were in the [project announcement] and we may be a little more.”

Babin said he expects the new hurricane study to be useful to global warming researchers because it will address the impact hurricanes have on levels of carbon dioxide, which most scientists believe is causing the Earth’s climate to warm as the gas accumulates in the atmosphere due to man-made and natural events.

“The big issue in trying to understand climate change is to understand the carbon cycle. But there are missing pieces. This hurricane effect could be one of the missing pieces of the carbon cycle,” Babin said.

Other scientists have shown that hurricanes stir the ocean to a froth and release bubbles of carbon dioxide into the atmosphere. But phytoplankton absorb carbon dioxide from the air and release it into the water. The scientists want to know whether the phytoplankton that grow in the wakes of hurricanes are able to reabsorb all the carbon dioxide that hurricanes release when they stir the ocean.

That information is important, Babin said, because climate scientists are debating whether global warming is likely to spawn more hurricanes or fewer due to effects like El Nino, the cyclical pattern of warm water in the Pacific Ocean that suppresses Atlantic hurricanes.

“If global warming is going make the number of hurricanes increase all over the globe, and if each hurricane is going to make [carbon dioxide levels] worse, that would be a bad feedback. But if each hurricane compensates somewhat, then hurricanes might help,” Babin said.

“We don’t know what the net [carbon dioxide] effect is. Is it a net good thing or a net bad thing? That’s one of the things we want to try to determine with further study,” Babin said.

The scientists will check their models against actual chemical and physical-ocean measurements made from a scientific buoy operated near Bermuda by Dickey of the University of California’s Ocean Physics Laboratory in Santa Barbara. The buoy, called the Bermuda Testbed Mooring, is often impacted by Atlantic Ocean hurricanes, Babin said.