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The surprising role of low-relief mountain ranges in climate regulation

The Earth’s climate system is remarkably stable, allowing life to flourish on our planet for hundreds of millions of years. This stability is evident as surface temperatures have varied by no more than 20° Celsius. It suggests a natural “thermostat” exists, finely tuning the concentration of atmospheric carbon dioxide (CO2) over geological time periods.

A recent study spearheaded by Aaron Bufe, an LMU geologist, and Niels Hovius from the German Research Center for Geosciences, sheds new light on the intricate processes that contribute to this natural climate regulation, specifically the role of erosion and weathering of rocks.

Impact of weathering on the carbon cycle

Weathering, the breakdown of rocks through exposure to water and wind, plays a pivotal role in the carbon cycle. Silicate minerals, when weathered, remove CO2 from the atmosphere, which is later deposited as calcium carbonate. However, not all weathering processes aid in carbon capture.

The weathering of carbonates, sulfides, and organic carbon-rich rocks can actually release CO2 back into the atmosphere. “These reactions are typically much faster than silicate weathering,” Hovius explains. This underscores the complex impact that mountain building has on the carbon cycle and climate regulation.

Insights on natural climate regulation

To delve into this complexity, the research team employed a weathering model to analyze the rates of sulfide, carbonate, and silicate weathering across several regions with varying erosion rates, including Taiwan and New Zealand.

The findings reveal consistent patterns across all studied locations. “We discovered similar behaviors in all locations, pointing to common mechanisms,” says Bufe, indicating a fundamental understanding of how these processes interact globally.

Interestingly, the study revealed that the relationship between erosion rates and CO2 fluxes is not straightforward. CO2 capture through weathering reaches its peak at moderate erosion rates, approximately 0.1 millimeters per year. Beyond this rate, CO2 capture diminishes.

Additionally, the process can even become a source of atmospheric CO2, especially in regions with high erosion rates like Taiwan or the Himalayas. This occurs because the increase in silicate weathering cannot keep pace with erosion. Meanwhile, the weathering of carbonates and sulfides continues to escalate.

The climate significance of low-relief mountain ranges

The research underscores the unique role of low-relief mountain ranges as significant carbon sinks. Examples include the Black Forest in Germany and the Oregon Coast Range in the USA.

These regions, with erosion rates around the optimal 0.1 millimeters per year, see an efficient weathering of silicate minerals, which significantly contributes to carbon capture. Bufe elucidates, “Over geological timescales, the temperature to which Earth’s ‘thermostat’ is set therefore depends strongly on the global distribution of erosion rates.”

Broader implications

The study not only enhances our understanding of the carbon cycle and its impact on global climate regulation but also sets the stage for future research.

Bufe suggests that to gain a more comprehensive understanding of erosion’s effects on the Earth’s climate system, future studies should explore the role of organic carbon sinks and weathering processes in floodplains.

The research underscores the importance of interdisciplinary approaches in tackling complex environmental issues and deepens our appreciation for the subtle, yet powerful, forces that have made our planet hospitable for life.

The full study was published in the journal Physical Review X.


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