Ancient climate study links past ocean acidification to current trends

A research team led by Prof. Li Mingsong at Peking University has provided new insights into the Paleocene-Eocene Thermal Maximum (PETM) and its effects on ocean chemistry.

The study, titled “Coupled decline in ocean pH and carbonate saturation during the Palaeocene–Eocene Thermal Maximum,” published in Nature Geoscience reconstructs ocean acidification during this ancient climate event, offering parallels with current trends linked to human-driven CO₂ emissions.

The Paleocene-Eocene Thermal Maximum (PETM), 56 million years ago, was a major carbon release event that resulted in rapid global warming and significant ocean acidification. This study highlights parallels with current climate change, emphasizing the need to understand past events to predict future impacts. The findings stress the urgency of addressing human-driven CO₂ emissions to protect marine ecosystems, particularly in vulnerable regions like the Arctic.

Ocean acidification

The team used paleoclimate data assimilation (DA), integrating proxy data and Earth system model simulations to reconstruct ocean carbonate chemistry. Atmospheric CO₂ rose dramatically from 890 ppm to 1980 ppm during the PETM. Acidification was most severe in high-latitude regions, similar to current trends in the Arctic, where aragonite saturation is declining.

The PETM was triggered by a massive carbon release, causing rapid warming and disrupting ecosystems. Ocean pH declined by 0.46 units, from 7.91 to 7.45, causing widespread disruptions to marine life. The ocean acidification led to the extinction of 30%–50% of benthic foraminifera and significant marine biodiversity loss.

Current CO₂ emissions are rising faster than during the PETM, threatening marine ecosystems and emphasizing the need for urgent climate action.