A study published in Nature Geoscience reports new findings on the effects that erosion has on the carbon cycle. The study comes from a group of researchers led by Aaron Bufe and Niels Hovius of the German Research Center for Geosciences (GFZ) who investigated erosion rates and carbon emissions in Taiwan.
Taiwan offers a unique opportunity to study geoscience because of its ever-shifting topographical change. Sitting just atop the subduction zone where an oceanic plate slides under the Asian continent, Taiwan is witness to near non-stop mountain growth. This becomes obvious when looking at the tall center of the island compared to the low southern end of the island, which is a result of erosion processes in the center of the island happening up to a thousand times faster than in the south of the island.
This difference in erosion rates provides the perfect real-world laboratory for geoscientists to investigate how uplift and erosion of rocks determine the balance of carbon emissions and uptake. The connection between mountain building and chemical weathering is still not fully understood, but scientists are eager to explore the influence that chemical weathering has on the carbon cycle on a global scale.
In conducting their study, the research team gathered water from mountains at different locations with different erosion rates. From this information, they could estimate the amount of CO2 that is sequestered as well as the amount released by different rates of weathering. They concluded that weathering processes release carbon dioxide at high erosion rates, meanwhile, they sequester carbon from the atmosphere at low erosion rates. First author Aaron Bufe adds, "We found that in the southernmost part of Taiwan, atmospheric CO2 sequestration dominates. However, farther north, where mountains are eroding faster, carbonate and sulfide weathering rates dominate and CO2 is released."
Bufe says that this sheds insight on the ways that mountain formation affects the carbon cycle, at least in Taiwan. "We can make relatively good statements about Taiwan. It appears that chemical weathering in this most active of mountain belts is a net emitter of CO2 to the atmosphere due to chemical weathering. But, perhaps the story changes when sediments washed down from the mountains are trapped in vast alluvial plains; like at the foot of the Himalayas or the Alps. Those sediments are often rich in silicates, the weathering of which will sequester CO2. In addition, mountain building brings not only sedimentary rocks with pyrite and carbonate to the Earth's surface, but also rock types that have formed from solidified magma and contain many fresh silicates that weather quickly. Researchers have some mountains to climb before we fully know the net effect of weathering on the Earth's climate."