Study says ice age could help predict ocean response to global warming

A team of scientists led by a Tulane University oceanographer has discovered that deposits deep beneath the ocean floor reveal a way to measure ocean oxygen levels and its links to carbon dioxide in Earth’s atmosphere during the last ice age, which ended more than 11,000 years ago. There is.

The results, published in Scientists progresshelp explain the role oceans played in past cycles of glacier melting and could improve predictions of how ocean carbon cycles will respond to global warming.

Oceans adjust atmospheric CO₂ as ice ages move toward warmer climates releasing greenhouse gases from carbon stored in the depths of the oceans. Research demonstrates striking correlation between global ocean oxygen content and atmospheric CO₂ from the last ice age to today – and how deep-sea carbon emissions could increase as the climate warms.

“The research reveals the important role of the Southern Ocean in controlling the global oxygen reservoir and carbon storage,” said Yi Wang, principal investigator and assistant professor of earth and environmental sciences at the Tulane University School of Science and Engineering. Wang specializes in marine biogeochemistry and paleoceanography.

“This will have implications for understanding how the ocean, particularly the Southern Ocean, will dynamically affect atmospheric CO.₂ in the future,” she said.

Wang conducted the study with colleagues at the Woods Hole Oceanographic Institution, the world’s leading independent nonprofit organization dedicated to ocean research, exploration and education. She worked for the institute before joining Tulane in 2023.

The team analyzed seafloor sediments collected from the Arabian Sea to reconstruct average oxygen levels in the world’s oceans thousands of years ago. They precisely measured isotopes of metallic thallium trapped in the sediments, which indicate the amount of dissolved oxygen in the global ocean when the sediments formed.

“Studying these metal isotopes over glacial-interglacial transitions has never been considered before, and these measurements allowed us to essentially recreate the past,” Wang said.

Thallium isotope ratios have shown that the global ocean overall lost oxygen during the last ice age compared to the current, warmer interglacial period. Their study found global ocean deoxygenation over a thousand years during an abrupt warming in the Northern Hemisphere, while the ocean gained more oxygen during an abrupt cooling during the transition from the last ice age to Today. The researchers attributed the observed changes in ocean oxygen to processes in the Southern Ocean.

“This study is the first to present an average picture of how the oxygen content of the world’s oceans has changed as Earth has moved from the last ice age to the warmer climate of the past 10,000 years,” said Sune Nielsen , associate scientist at WHOI and co. -author of the research.

“These new data are very important because they show that the Southern Ocean plays an essential role in modulating atmospheric CO.₂. Given that high-latitude regions are most affected by anthropogenic climate change, it is troubling that these also have an outsized impact on atmospheric CO.₂ in the first place. »