Soil Gas Controls on Chemical Weathering Fluxes

The chemical weathering of rocks by carbonic acid as rainfall percolates through the ground sequesters CO2 in the form of alkalinity, which is transported via rivers to the ocean. Rates of chemical weathering are thought to scale with climate and act as a negative feedback to atmospheric CO2 concentrations. This natural process is hypothesized to be the primary mechanism by which the Earth’s climate has remained habitable over the past 4 billion years despite significant changes in solar luminosity and tectonic degassing rates. My research is investigating the relationship between CO2 concentrations in soil environments (controlled by atmospheric concentrations, soil respiration of organic carbon, and soil diffusivity) and thermodynamic limits that set the potential amount of chemical weathering that can occur. READ MORE

Coupled Pyrite Oxidation and Carbonate Dissolution in Shales

The weathering of shales, which comprise roughly 20% of Earth’s terrestrial surface-exposed rocks, involves the oxidation of pyrite minerals and dissolution of calcium carbonate. Together, these coupled weathering reactions have been hypothesized to act as primary regulators of atmospheric CO2 and O2 concentrations over geological timescales. Additionally, the oxidative weathering of shales is known to release metal contaminants into water supplies that can drastically affect freshwater resources. My research is looking to characterize the dynamics of these coupled weathering reactions and their implications for carbon cycling and stream geochemistry in shale catchments, primarily focusing on the Mancos shale in the East River watershed in Colorado. READ MORE

Water Isotopes and Terrestrial Hydrology

Terrestrial moisture recycling that occurs via evapotranspiration represents the dominant flux of water that falls on land. Despite this fact, evapotranspiration dynamics, including the partitioning between plant transpiration and soil evaporation, represent a major uncertainty in our ability to project future climate. This uncertainty has large implications for local temperature, rainfall patterns, and freshwater availability. Stable isotopes of hydrogen (δD) and oxygen (δ18O) in water molecules provide unique insights into terrestrial moisture recycling based on mass-dependent fractionation processes that occur during evaporation and precipitation. My research uses the isotopic characterization of meteoric waters along with reactive transport models of atmospheric water vapor to quantify moisture recycling in modern- and paleo-terrestrial systems. READ MORE

Funded Projects

NSF EAR 2103520: Stream Corridor Hydrologic Controls on Carbon Dioxide Fluxes. NSF Hydrologic Sciences Program, PI: M. Winnick, co-PI: D. Boutt, 2021-2024.

NSF AGS 2102983: P2C2: A Speleothem and Cave Monitoring Research Program to Reconstruct the Paleoclimatology of the Yucatan Peninsula–Testing Modes and Causes of Variability in the North American. NSF Paleo Perspectives on Climate Change Program, PI: M. Medina-Elizalde, co-PI: M. Winnick, 2021-2024.

NSF EAR 1906079: Acquisition of an isotope-ratio-monitoring mass spectrometer at the University of Massachusetts Amherst. NSF Instruments and Facilities Program, PI: I. Castañeda, co-PI’s: S. Burns, M. Winnick, 2019-2021.