NM Tech Researcher Studies Ocean Acidity's Effects on Climate, March 6, 2007

Max Zeigler and Karl Haase

Right: Students Max Zeigler and Karl Haase were co-authors of the research paper, along with chemistry professor Oliver Wingenter. Max is now a grad student at the University of Washington, and Karl is a grad student at the University of New Hampshire.

by George Zamora

SOCORRO, N.M., March 6, 2007 – New Mexico Tech chemistry professor Oliver W. Wingenter is the principal author of research paper published in the March 7, 2007 issue of Geophysical Research Letters (GRL), which investigates how increased levels of ocean acidity and carbon dioxide concentrations have resulted in unexpected changes in marine biological production of organic gases that affect the Earth’s climate.

The study, funded by New Mexico Tech, the National Science Foundation and the Comer Foundation, sheds light on several chemical processes that regularly occur throughout the world’s oceans and which may have the potential to help regulate the Earth’s climate and slow down global warming.

In the GRL article titled “Unexpected consequences of increasing CO2 and ocean acidity on marine production of DMS and CH2CH: Potential climate impacts,” Wingenter and his research colleagues have determined that by increasing atmospheric mixing ratios of carbon dioxide, the scientists were then able to make ocean surface waters three times more acidic than normal.

Other recent scientific studies have shown that ocean acidity is rising at a rate of about 100 times faster than at any known time, Wingenter said, but this newly published study links the effect of increasing ocean acidity to changes in phytoplankton ecosystems that consume and produce carbon dioxide and other organic “greenhouse gases.”

“Pronounced physiological changes in some phytoplankton have been observed during previous CO2 perturbation experiments,” said Wingenter. “And although the changes in ocean acidity can be predicted, the consequences for marine organisms, their ecosystems, and climate-relevant organic gas emissions are largely unknown.”

In their month-long field experiment, conducted in late spring of 2005 at the Large-Scale Marine Facilities of the University of Bergen, Norway, Wingenter and his research team used three sets of three large plastic bags — two meters in diameter, and filled to a depth of 10 meters with seawater — to simulate present-day carbon dioxide concentrations and ocean acidity, as well as CO2 levels that are expected to be found at the end of this century and the middle of the next one.

During the study, concentrations of dimethyl sulfide (DMS) and chloroiodomethane, which are produced by phytoplankton in the ocean water, were analyzed, measured and recorded.

“Marine microorganisms produce DMS, which is a radiatively important gas,” Wingenter explained. “In the atmosphere, DMS is rapidly oxidized to sulfur dioxide, which can form sulfate aerosols.

“As a result, emissions of DMS are a major source of cloud condensation nuclei in the clean marine atmosphere,” he added.

“In addition, chloroiodomethane and other iodocarbons produced by phytoplankton quickly react with sunlight in the atmosphere and end up releasing iodine that can destroy ozone and lead to aerosol nucleation,” Wingenter said.

The marked increases in the climate-relevant gases and ocean acidity observed in the study may be directly attributable to changes the phytoplankton’s environment brought on by adding more carbon dioxide, the researchers said in their paper.

“Enhanced future production of these gases may contribute to planetary cooling and may eventually slow down global warming,” Wingenter pointed out.

“This experimental study points to the need for similar work to determine the changes in other phytoplankton communities in response to future CO2 concentrations and any resultant changes in organic gas production,” said Wingenter.

“Combining future experimental and modeling efforts will lead to a better understanding of the feedback systems between the atmosphere and ocean in the future,” he added.

Wingenter’s co-authors of the recent GRL paper include then New Mexico Tech undergraduates Karl Haase and Max Ziegler, as well as research colleagues from the University of Bergen, the University of New Hampshire, the University of Kiel in Germany, and the University of California at Irvine.