by Jeff McIntire-Strasburg, St. Louis, MO on 05.18.07
Science & Technology (science)


While the potential direct effects of climate change are often frightening enough, the possibility of feedback loops, in which these changes end up causing, and even reinforcing, others, are more worrisome over the long term. According to National Geographic News, one such positive feedback loop may be hampering the ability of oceans around Antarctica to absorb carbon dioxide. Scientists believed that these waters would serve as a massive sink for CO2 emissions, but, according to a new study that will be published in Science today, these oceans are no longer absorbing the greenhouse gas at the levels they once did.

Lead researcher Corinne Le Quéré, of the Max Planck Institute for Biochemistry in Jena, Germany, and her team "examined atmospheric carbon dioxide measurements taken from points around the world during the past 24 years," and expected to find that the Southern oceans would absorb CO2 at a rate consistent with the growth in emissions. They discovered, however, that climate change and the Antarctic ozone hole were actually hampering these waters natural ability to mop up rising carbon levels:

Since the 1980s, the team estimated that the oceans carbon dioxide sink mechanism has weakened, and it is currently absorbing around one-third less than expected.
That means about 5 percent of human-caused greenhouse emissions are being left with nowhere to go.

Previous calculations have suggested that the oceans around Antarctica had capacity to absorb even more carbon dioxide, so the scientists were surprised to find the current low rate of uptake.

The problem appears to be an increase in winds over these oceans, and Le Quéré and her colleagues believe this is a result of "an increase in greenhouse gases and less ozone, which have both changed how heat is distributed in the atmosphere..." An independent study by Nicolas Gruber and Nicole Lovenduski of UCLA backs up these findings, and Gruber believes a feedback loop could be created, further hampering the ocean's ability to absorb CO2:
...if the oceans absorb less carbon dioxide, then there is more of the gas in the atmosphere.
"This could make the wind strength increase even more, meaning the oceans absorb even less carbon dioxide, and so on," [Gruber] said.

The ozone hole over Antarctica appears to be closing; that could provide some relief from higher wind speeds. Both Gruber and Le Quéré , however, note that reducing and stabilizing greenhouse gas emissions provides the only real long-term solution for this problem. ::National Geographic News and Inter Press Service News Agency
Photo credit: Maria Stenzel/NGS