An investigation of rock weathering processes in the McMurdo Dry Valleys, Antarctica using acoustic emission and micrometeorological monitoring

Bedrock and boulders located in the polar desert environment of the McMurdo Dry Valleys (MDV) experience some of the lowest rates of weathering and erosion on Earth. Because the MDV region is the largest ice-free area in Antarctica, and one of the coldest, driest, and windiest places on the planet, it serves as an extreme endmember for terrestrial surface processes. However, our understanding of the drivers of rock breakdown in this unique landscape is limited, particularly in inland and high elevation locations where liquid water is rare year-round. In order to characterize better the weathering and erosional processes in the MDV, we require a way to (1) detect the slow growth of cracks, which ultimately leads to rock disaggregation, and (2) relate crack formation and growth to the responsible environmental catalysts.

Here, we present preliminary data from an in situ rock breakdown monitoring station deployed in one of the inland-most portions of the MDV, Beacon Valley. The station consists of an acoustic-emission (AE) monitoring system, which detects elastic waves that are released during the formation and extension of cracks in rock, thermocouples and surface moisture sensors adhered to rock surfaces, and a micrometeorological station that records air temperature, humidity, wind speed/direction, solar radiation, and barometric pressure. Four adjacent dolerite boulders with differing crystal sizes and degrees of weathering were instrumented with six AE sensors each, enabling us to both record and locate cracking events beginning in the 2018-2019 austral summer. We will compare the timing of AE events (cracking) to the associated micrometeorological data to determine what environmental forcings (e.g., temperature fluctuations, high humidity, the presence of liquid water, etc.) are responsible for rock breakdown in the coldest and driest portions of the MDV.