Scientists have found a new way to measure the ocean oxygen level and its association with carbon dioxide in the Earth’s atmosphere during the last ice age, which ended over 11,000 years ago, using deposits deep under the ocean floor. This could explain how oceans responded to past glacial melting cycles and help better prepare for the future.
The study, conducted by researchers from Tulane University, found that this new measurement enables an understanding of the role oceans played in previous glacial melting cycles and helps improve predictions of how ocean carbon cycles will respond to global warming.
As ice ages transition to warmer climates, oceans adjust atmospheric carbon dioxide by releasing the greenhouse gas from carbon stored within the deep ocean, the university’s press statement reveals. The new study shows a significant association between global ocean oxygen contents and atmospheric carbon dioxide from the last ice age to today. It also highlights how the release of carbon from the deep sea may increase as the climate warms.
For the study, the researchers analysed seafloor sediments from the Arabian Sea to reconstruct average global ocean oxygen levels thousands of years ago. The statement explains that the researchers accurately measured isotopes of the metal thallium in the sediments, which show the amount of oxygen that was dissolved in the global ocean when the sediments were formed.
According to the researchers, the examination of these metal isotopes on glacial-interglacial transitions has never been looked at before, and this allowed them to recreate the past.
The study, published in the journal Science Advances, showed that the global ocean lost oxygen during the last ice age compared to the current, warmer interglacial period, an Earth.com report explained. The findings showed that during sudden warming in the Northern Hemisphere, the global ocean experienced considerable deoxygenation, while abrupt cooling led to an increase in oceanic oxygen. These changes were closely linked to processes in the Southern Ocean.
“The research reveals the important role of the Southern Ocean in controlling the global ocean oxygen reservoir and carbon storage,” lead author Yi Wang said in the press statement. “This will have implications for understanding how the ocean, especially the Southern Ocean, will dynamically affect the atmospheric carbon dioxide in the future.”
The new data also shows that the Southern Ocean plays an important role in modulating atmospheric carbon dioxide. As high latitude regions are those most affected by anthropogenic climate change, it is concerning that these have an outsize impact on atmospheric carbon dioxide in the first place, the researchers said in the statement.
According to the researchers, it’s important to understand the connections between the ocean, particularly the Southern Ocean, and atmospheric carbon dioxide to predict how the ocean’s carbon cycles will respond to ongoing climate change.