Southern Ocean's CO2 release crucial for climate history

Scientists have learned more about how the Southern Ocean near Antarctica affects global climate. They studied tiny fossils called foraminifera found on the ocean floor. These fossils can help us understand carbon dioxide (CO2) levels in the past. Research shows that between 18,000 and 11,000 years ago, there was a significant rise in atmospheric CO2. This increase caused rapid global warming, melted glaciers, and marked the end of the last ice age. Much of this CO2 came from the Southern Ocean, but scientists had limited knowledge about how this happened. The team examined the chemistry of sand-sized foraminifera collected from mud on the seafloor near Tasmania. Foraminifera are small organisms that build protective shells. When they die, their shells remain on the seabed and can be analyzed by scientists. These shells hold important information about the conditions of seawater over millions of years. To study them, researchers collected mud from the ocean floor using a giant tube. They brought the mud back to their labs, where they examined individual foraminifera shells under microscopes. The chemical composition of these shells allows scientists to reconstruct historical seawater temperatures and conditions. While foraminifera are found in many places in the ocean, they are scarce in the Southern Ocean because the water there can dissolve their shells. However, the depth of the ocean near Tasmania is suitable for collecting data on the chemistry of the Southern Ocean. By analyzing foraminifera from this specific area, researchers mapped out changes in CO2 levels during the last ice age. They found that some of the CO2 released came from biological activities, while other amounts escaped directly from the seawater into the atmosphere. These findings enhance scientists' climate models, helping them predict future atmospheric CO2 levels and understand the Southern Ocean's role in climate change. This information is crucial for creating strategies to reduce CO2 emissions.