Climate, Carbon, and the Southern Ocean
New research by scientists from the UK's University of Southampton, British Antarctic Survey, the University of East Anglia and Germany's Alfred Wegener Institute challenges existing theory regarding how carbon dioxide (CO2) is absorbed in the Southern Ocean that circulates around Antarctica.
The world's oceans are the largest carbon sink on the planet, modulating temperatures by absorbing carbon dioxide over time scales of hundreds to thousands of years. Understanding how that's done is key to scientists understanding how climate has changed throughout earth history, including dramatic shifts that led to ice ages and sea level rise that has submerged continental land masses.
The researchers investigated the ocean circulation and carbon concentration of the Weddell Gyre an area of the Southern Ocean east of the Antarctic Peninsula. They found that biological processes far out in the open Southern Ocean are the most important factors that determine how carbon dioxide is absorbed. That runs contrary to existing mainstream belief that the creation of dense water in shallow seas near the Antarctic coast.
The Southern Ocean's biological carbon pump
More particularly, the researchers determined that phytoplankton, microscopic, oceanic plants that turn sunlight into energy to live, play the key role in how carbon dioxide is absorbed in the Southern Ocean.
Phytoplankton absorb carbon dioxide from the atmosphere at and near the ocean surface, assimilating it into their bodies as they grow, then wind up storing it when they die and sink to the ocean floor. It's a process scientists call the biological carbon pump.
“The findings were important both for our understanding of climate transitions in the past, such as the ice ages, as well as our projections of future climate change," study leader Graeme MacGilchrist from the University of Southampton was quoted in a news report.
“The results carry implications for our understanding of how the high-latitude Southern Ocean, close to the Antarctic continent, influences atmospheric carbon and global climate on 100 to 1000-year timescales," he added.