The Role of the Southern Ocean in Ocean Oxygen Levels and Carbon Storage

A recent study conducted by a team of scientists led by a Tulane University oceanographer has shed light on the connection between ocean oxygen levels and carbon dioxide in the Earth’s atmosphere during the last ice age. The findings, published in Science Advances, provide valuable insights into the role of the Southern Ocean in past glacial melting cycles and its potential impact on future climate change.

Oceans have a significant influence on atmospheric carbon dioxide levels. As ice ages transition to warmer climates, oceans release stored carbon from within their depths, thereby adjusting the atmospheric CO2 concentrations. This process is critical in regulating global carbon cycles. The recent study demonstrates a remarkable correlation between global ocean oxygen contents and atmospheric CO2 levels from the last ice age up to the present day. This research offers valuable insights into how carbon release from the deep sea could increase as the climate continues to warm.

The study highlights the crucial role played by the Southern Ocean in controlling the global ocean oxygen reservoir and carbon storage. Lead researcher Yi Wang, an assistant professor of Earth and Environmental Sciences at Tulane University, emphasizes the significance of these findings in understanding the dynamic relationship between the ocean, particularly the Southern Ocean, and atmospheric CO2 concentrations in the future.

The research team analyzed seafloor sediments collected from the Arabian Sea to reconstruct average global ocean oxygen levels during the last ice age. By meticulously measuring thallium isotopes in the sediments, which serve as indicators of dissolved oxygen, the scientists were able to recreate the ocean’s oxygen content from thousands of years ago. This novel approach of studying metal isotopes during glacial-interglacial transitions provided unprecedented insights into past ocean oxygenation.

The study revealed a global ocean deoxygenation that occurred over a thousand years during abrupt warming in the Northern Hemisphere. Conversely, the ocean gained more oxygen during abrupt cooling as the transition from the last ice age to the present took place. These observed changes in ocean oxygen levels were mainly attributed to processes occurring in the Southern Ocean.

The research findings are particularly significant as they present an average overview of how the oxygen content of the global oceans evolved during the transition from the last glacial period to the warmer climate of the last 10,000 years. Sune Nielsen, an associate scientist at the Woods Hole Oceanographic Institution (WHOI) and co-author of the study, acknowledges the importance of this study, stating that the new data shed light on the critical role played by the Southern Ocean in modulating atmospheric CO2 concentrations.

The role of the Southern Ocean in influencing ocean oxygen levels and carbon storage is now better understood thanks to the recent study led by scientists from Tulane University and WHOI. By analyzing seafloor sediments and measuring thallium isotopes, the researchers have offered valuable insights into the past relationship between ocean oxygen and atmospheric CO2 concentrations. These findings have important implications for predicting how ocean carbon cycles will respond to global warming. As we continue to face the pressing challenge of climate change, understanding the intricate interactions between the oceans, atmosphere, and carbon storage is crucial for developing effective strategies to mitigate its impact.