Arctic's Ancient Methane Shift: A Warning for Modern Climate Change

A recent study published in Nature Geoscience on September 25, 2025, by researchers from the Guangzhou Institute of Geochemistry (GIG) of the Chinese Academy of Sciences, has unveiled a significant shift in methane oxidation processes during the Paleocene-Eocene Thermal Maximum (PETM) approximately 56 million years ago. This shift transformed the Arctic Ocean from a methane sink into a substantial source of carbon dioxide, intensifying global warming and ocean acidification. The findings suggest that similar processes could occur in the modern Arctic as it warms and freshens, potentially creating a "methane switch" that may exacerbate current climate change.

The PETM was a period of rapid global warming, characterized by a significant increase in global temperatures and ocean acidification. During this time, reduced sulfate concentrations in Arctic waters led to a transition from anaerobic oxidation of methane (AOM) in sediments to aerobic oxidation of methane (AeOM) in the water column. This shift resulted in the Arctic Ocean becoming a significant source of carbon dioxide, amplifying global warming and contributing to ocean acidification.

Professor Zhang Yige of GIG stated, "Microbes utilize sulfate as their 'fuel' to convert methane energy with high efficiency, while simultaneously generating alkaline by-products that help counteract ocean acidification." The study found that during the PETM, sulfate concentration in Arctic waters was less than one-third of its current level, leading to increased carbon dioxide emissions from the Arctic Ocean.

The potential for a modern "methane switch" in the Arctic Ocean has significant implications for global climate change. Increased carbon dioxide emissions from the Arctic could accelerate global warming, leading to more extreme weather events, sea-level rise, and disruptions to ecosystems and human societies. Understanding these processes is crucial for developing effective climate mitigation and adaptation strategies.

The GIG is a leading research institution in China, focusing on geochemistry, environmental science, and related fields. It has a history of conducting significant research on climate change and geochemical processes.

Understanding the mechanisms of methane oxidation and their impact on climate is essential for predicting and mitigating future climate change scenarios.