Throughout the history of the Earth, the surface temperature has remained relatively stable, fluctuating by only about 20 degrees Celsius. This stability has been crucial for the development and sustenance of life on our planet. The key to maintaining this stable temperature lies in Earth’s ability to regulate the concentration of atmospheric carbon dioxide over long periods, effectively acting as a ‘thermostat’. One of the primary mechanisms that contribute to this regulation is the process of erosion and weathering of rocks.

Recent research led by geologists Aaron Bufe and Niels Hovius has shed new light on how erosion rates impact the carbon cycle and global temperatures. Contrary to common assumptions, the study found that the highest CO2 capture through weathering reactions occurs in low-relief mountain ranges with moderate erosion rates, rather than in areas with the fastest erosion rates. Weathering, which occurs when rocks are exposed to water and wind, plays a critical role in removing carbon from the atmosphere.

The team of researchers used a weathering model to analyze the fluxes of different types of weathering reactions, such as sulfide, carbonate, and silicate weathering, in various study regions like Taiwan and New Zealand. Their findings, published in Science, revealed common mechanisms at play in all locations. The relationship between erosion rates and CO2 fluxes was found to be non-linear, with CO2 capture peaking at an erosion rate of approximately 0.1 millimeters per year.

In regions with high erosion rates, such as Taiwan or the Himalayas, weathering shifts from being a CO2 sink to a source. This is due to silicate weathering reaching a saturation point at some stage, while the weathering of carbonates and sulfides continues to increase. On the other hand, landscapes with moderate erosion rates around 0.1 millimeters per year, like the Black Forest or the Oregon Coast Range, are identified as the most significant CO2 sinks. In these areas, rapidly weathering carbonates and sulfides become depleted, allowing silicate minerals to efficiently weather.

The researchers emphasize that over geological timescales, the temperature regulation of Earth’s ‘thermostat’ is heavily influenced by the global distribution of erosion rates. Understanding the effects of erosion on Earth’s climate system requires a comprehensive consideration of all factors, including organic carbon sinks and weathering in floodplains. Aaron Bufe suggests that future studies should delve deeper into these aspects to gain a more detailed understanding of Earth’s intricate climate mechanisms.

Earth

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