ADVANCING METHODS TO MEASURE THE ATMOSPHERIC CO2 SINK FROM CARBONATE ROCK WEATHERING

Atmospheric CO₂ concentrations are an important factor impacting current global climate change. As such, a more detailed understanding of processes that impact atmospheric CO₂ fluxes is required in order to predict and potentially mitigate future climate change. While a sink of atmospheric carbon from the continents to the ocean from carbonate mineral weathering has been considered to be offset by carbonate mineral precipitation in the oceans, efforts are underway to make direct measurements of the fluxes and processes, and how these are impacted by changing global geochemical environments. In making such measurements of the carbonate mineral weathering flux from the continents there is first a question of what variables need to be considered among geologic, climatic, and human influences, and secondly a balance between spatial and temporal resolution of data and practical tractability. We are investigating the use of existing, freely available data to estimate the atmospheric CO₂ sink from carbonate weathering within a 4,248 km² portion of the Barren River drainage basin in southern Kentucky and northern Tennessee, with 3,911 km² of carbonate mineral outcrop. Using a site with US Geological Survey discharge data and eight-hour resolution water quality data from the Bowling Green Municipal Utilities water treatment facility, along with precipitation and evapotranspiration (et) from regional climatic networks, a value of the atmospheric CO₂ sink from carbonate rock weathering, normalized by time, area of carbonate rock, and precipitation-et can be calculated. Favorable comparison between of such normalized values from multiple drainage systems would indicate that analysis of additional basins with similar data may lead to quantitative relationships between geologic and climatic data, so that the flux could potentially be mapped over large areas with existing sources of data.