Researchers Report Southern Ocean Absorbing Less Atmospheric Carbon

Scientists studying the Southern Ocean have discovered that stronger winds are weakening the ocean's ability to absorb carbon dioxide from the atmosphere, according to new research published online 17 May by Science, at the Science Express website.

These new wind patterns, the authors say, are likely the result of a rise in global surface air and water temperatures caused by human activities.

"This weakening is attributed to the observed increase in Southern Ocean winds resulting from human activities and projected to continue in the future," wrote lead author Corinne Le Quéré, a researcher at the Max Planck Institute of Biochemistry in Germany.

Additionally, the upswing in winds has been linked with new water circulation patterns further affecting the Southern Ocean's ability to absorb atmospheric carbon dioxide changes, the authors wrote.

Through carbon dioxide sink, also known as sequestration, the world's oceans remove carbon dioxide from the atmosphere. Sequestration takes place through two main processes: the direct interaction of gas with the seawater as well as the use of carbon dioxide by small organisms such as algae and plankton.

For their study, Le Quéré and an international team collected atmospheric carbon dioxide data from 11 stations in the Southern Ocean, which surrounds Antarctica, along with an additional 40 stations across the globe.

The authors believe that changes in carbon dioxide sink are due variations in the physical mixing and upwelling in the oceans, caused by changing winds, which affect the natural oceanic carbon cycles.

Because this process is weakening, concentrations of the greenhouse gas in Earth's atmosphere may be higher in the future than predicted, the researchers say.

"Atmospheric CO₂ increases at only half the rate of human-induced CO₂ emissions because of the presence of large CO₂ sinks in the ocean and on land," wrote the team.

Over the next 25 years, the researchers estimate that the Southern Ocean carbon dioxide sink efficiency will continue to decline, affecting atmospheric carbon dioxide levels over several centuries.

Evelyn Brown and Benjamin Somers

18 May 2007