Warmer, Wetter Climates Accelerate Mechanical Weathering In Field Data, Independent Of Stress-Loading

Weathering is a foundational process in most Earth systems, but there has been a lack of data directly quantifying what influences mechanical weathering. Here we use multiple years of in situ field data, "listening" to acoustic emissions of naturally cracking rocks, to test a hypothesized link between climate and subcritical crack-tip processes (i.e., the bond-breaking mechanism thought to embody most mechanical weathering). Our results challenge the assumption of a singular dependence of mechanical weathering on stresses. We find that mechanical weathering rates exponentially increase as functions of atmospheric vapor pressure (VP), temperature, and relative humidity, even when controlling for stress-loading. VP exerts the most pronounced influence on the observed mechanical weathering rates. Put in the context of global climate change, our results underscore the potential for climate-dependent subcritical crack-tip processes to influence all weathering-allied problems including the long-term stabilization of the climate by weathering-carbon-cycle feedbacks.Plain Language Summary Weathering refers to the mechanisms by which rocks physically and chemically break down into soil, sediment, and dissolved molecules. Chemical weathering rates are frequently inferred to be strongly coupled to climate, because chemical reactions depend on factors like moisture and temperature. In past studies, climate has been connected to physical weathering only through its influence on stress-inducing processes like freezing or temperature cycling. In this study, we use field observations of the sounds that natural rock cracking makes and find that cracking accelerates in warmer, wetter conditions, even when controlling for stresses. Thus, this study provides field data to support a climatic influence on weathering via a pathway-molecular bond-breaking at crack-tips-that is additional to, and distinct from, how climate may influence stresses or chemical weathering. Accordingly, any system connected to weathering, such as Earth's carbon cycle, surface erosion, or biosphere, could be impacted by this additional process of accelerated rock breakdown during warmer and wetter climates, such as those predicted under modern global warming trends.