How Rock Weathering Creates a Climate Feedback Loop
▼ Summary
– Since the 1980s, scientists have known that rock erosion removes CO₂ from the atmosphere, but recent studies show it can also emit CO₂ by oxidizing organic carbon in sediments.
– The study in Nature Communications examined the Toarcian Ocean Anoxic Event, a volcanic global warming episode 183 million years ago, to test how erosion’s competing effects on CO₂ balance out.
– Researchers found that eroding organic carbon amplified climate warming during the Jurassic event, suggesting a similar process may apply to modern climate change.
– The Toarcian event was triggered by massive volcanic eruptions across South Africa and Antarctica, causing 6°–7°C of global warming and mass extinctions of corals and marine species.
– The study’s lead author is Dr. Madeleine Stow of the University of Oxford, with coauthors from the UK and France.
Since the early 1980s, geoscientists have recognized that the erosion and weathering of rock gradually pulls carbon dioxide from the atmosphere, acting as a natural thermostat for Earth’s climate over geological time. However, more recent research reveals that erosion can also release CO₂ by oxidizing the organic carbon trapped within eroding sediments. The net effect of these opposing forces,carbon removal via rock weathering versus carbon emission via organic carbon weathering,has long remained unclear.
A newly published study in Nature Communications turns to the deep past to resolve this balance. Dr. Madeleine Stow from the University of Oxford, working alongside colleagues across the UK and France, focused on a volcanic-driven warming episode from the early Jurassic period, roughly 183 million years ago. Known as the Toarcian Ocean Anoxic Event, this period saw Earth’s temperature spike dramatically.
The team’s findings suggest that eroding organic carbon actually amplified the warming during that ancient event. This raises a sobering possibility: the same mechanism could be influencing modern climate change today. But whether history will repeat itself remains an open question.
Reading ancient air from seafloor sediments
The Toarcian event belongs to a small group of past climate upheavals triggered by massive volcanic phenomena called large igneous provinces. Several of these episodes are linked to mass extinctions, most famously the Permian-Triassic extinction event, or “Great Dying,” caused by the Siberian Traps. In the Toarcian case, colossal eruptions across what is now South Africa and Antarctica,then joined as a single landmass,unleashed enough greenhouse gases to raise global temperatures by 6° to 7° Celsius. This reshuffled plant and dinosaur communities on land and wiped out many coral and marine species.
“This event had been well studied before. We understand its drivers, we understand how it caused mass extinctions, and it’s driven by this Large Igneous Province release,” said Professor Bob Hilton of the University of Oxford, a coauthor and principal investigator on the study. The new research adds a critical layer: the feedback loop created by eroding organic carbon may have made the warming worse than the volcanoes alone could have achieved.
(Source: Ars Technica)