Foraminifera fossils reveal past carbon dioxide levels

Tiny sand-sized fossils called foraminifera are providing important insights into Earth's climate history. These microscopic organisms have lived in the ocean for millions of years, and their fossilized shells hold valuable information about past atmospheric conditions. A recent study published in Nature Communications studies their role during the end of the last ice age, when carbon dioxide levels rose sharply. Between 18,000 and 11,000 years ago, carbon dioxide in the atmosphere increased rapidly, causing global temperatures to rise and glaciers to melt. Much of this CO2 came from the Southern Ocean near Antarctica. Scientists had limited knowledge about how this CO2 was released during that time. The new research reveals the extent of CO2 emissions from the Southern Ocean and identifies the factors that influenced these changes. Researchers collected mud samples from the ocean floor south of Tasmania, where foraminifera shells are abundant. These shells contain trace elements from the surrounding seawater, which can help reconstruct past oceanic conditions. By analyzing the chemical makeup of these shells, scientists can learn about historical seawater chemistry and temperature. The study found that two main processes contributed to CO2 release: biological and physical. Initially, the biological processes, involving marine life, played a greater role. Later on, physical processes, where CO2 escaped from the seawater into the atmosphere, became more significant. This research is crucial for improving climate models that predict future changes. By understanding past CO2 fluctuations, scientists can better forecast how the polar Southern Ocean may influence atmospheric conditions in the future. This knowledge is vital for creating effective strategies to manage carbon emissions and mitigate climate change.