Rock Weathering as a CO₂ Sink Or?: A New Perspective

In a recent study led by the University of Oxford, the traditional view of natural rock weathering as a CO₂ sink has been challenged. Contrary to popular belief, rock weathering can also act as a significant CO₂ source, on par with the emissions from volcanoes.

“A new study led by the University of Oxford has overturned the view that natural rock weathering acts as a CO₂ sink, indicating instead that this can also act as a large CO₂ source, rivalling that of volcanoes.”

Rocks, which contain vast amounts of carbon from ancient plant and animal remains, play a pivotal role in the “geological carbon cycle.” This cycle has been instrumental in regulating Earth’s temperature for over a billion years. One of the primary mechanisms believed to help in this regulation is the absorption of CO₂ during chemical weathering. This process was thought to counterbalance the continuous CO₂ emissions from global volcanic activity.

“Rocks contain an enormous store of carbon in the ancient remains of plants and animals that lived millions of years ago. This means that the “geological carbon cycle” acts as a thermostat that helps to regulate the Earth’s temperature.”

However, this study has unveiled an additional natural process of CO₂ release from rocks, which is as significant as the CO₂ emissions from volcanoes. This revelation underscores the fact that this process has been overlooked in most models of the natural carbon cycle.

“However, for the first time this new study measured an additional natural process of CO₂ release from rocks to the atmosphere, finding that it is as significant as the CO₂ released from volcanoes around the world.”

The process in question occurs when rocks formed on ancient seafloors are pushed back to the Earth’s surface, exposing the organic carbon within them to oxygen. This exposure can lead to a reaction that releases CO₂, suggesting that weathering rocks might be a source of CO₂ rather than the assumed sink.

“The process occurs when rocks that formed on ancient seafloors (where plants and animals were buried in sediments) are pushed back up to Earth’s surface… This means that weathering rocks could be a source of CO₂, rather than the commonly assumed sink.”

To quantify this CO₂ release, the researchers employed a novel method using a tracer element, rhenium. By sampling river water for rhenium levels, they could estimate the CO₂ release from weathering organic carbon in rocks. Their findings identified several regions where weathering was a significant CO₂ source, particularly in mountain ranges like the eastern Himalayas, the Rocky Mountains, and the Andes.

“The global CO₂ release from rock organic carbon weathering was found to be 68 megatons of carbon per year.”

While this release appears to be small compared to estimates of human-induced emissions from fossil fuels, it is comparable to the CO₂ emissions from global volcanic activity. This discovery underscores the need for a more nuanced understanding of Earth’s natural carbon cycle.

In conclusion, understanding these natural fluxes is crucial for predicting our carbon budget.

“While the carbon dioxide release from rock weathering is small compared to present-day human emissions, the improved understanding of these natural fluxes will help us better predict our carbon budget” concluded Dr. Zondervan.

Source: EurekAlert!