Chemical weathering in mountain regions

Chemical weathering

The chemical dissolution (weathering) of calcium and magnesium silicate minerals with carbonic acid removes CO2 from the atmosphere. Therefore, silicate weathering regulates Earth’s climate on geologic timescales. The weathering of other minerals can also impact the CO2 budget. For example, the dissolution of carbonates by sulfuric acid releases CO2 from the solid Earth. This release can lead to transient increases in atmospheric CO2 concentrations for >10 My. During my postdoc at the GFZ, I have been studying the impact of erosion rates and extreme storm precipitation on chemical fluxes from both silicates and carbonates in the Taiwanese mountain range.

Weathering fluxes during a storm event

A large portion of rainfall in Taiwan is generated during Typhoons and other storms. During a field season in Taiwan in May 2017, we were “lucky” to experience a major rain storm during which 1.3 m of rain fell within three days. These rainfall amounts are equivalent to the rain that fell on Houston during Hurricane Harvey! We are currently generating a detailed record of changes in the river chemistry across this major storm event. Moreover, I am working with a Taiwanese colleague on time-series of water chemistry across major Typhoon events.

Links between erosion and weathering

Active mountain ranges produce the majority of fresh sediments on Earth’s surface, and strongly impact chemical weathering. Traveling north from the southernmost tip of Taiwan, the landscape changes dramatically from gentle, soil-mantled hillslopes that are eroding at rates of < 0.05 mm/y, to steep mountains that are eroding at rates of up to 10 mm/y and that are characterized by frequent landsliding. By measuring the change of river-water chemistry across this transition, we are investigating how erosion rates impact the volume of the weathering zone and the export of solute fluxes.