Airborne detection of diffuse carbon dioxide emissions at Mammoth Mountain, California

We report the first airborne detection of CO₂ degassing from diffuse volcanic sources. Airborne measurement of diffuse CO₂ degassing offers a rapid alternative for monitoring CO₂ emission rates at Mammoth Mountain. CO₂ concentrations, temperatures, and barometric pressures were measured at ∼2,500 GPS-referenced locations during a one-hour, eleven-orbit survey of air around Mammoth Mountain at ∼3 km from the summit and altitudes of 2,895–3,657 m. A volcanic CO₂ anomaly 4–5 km across with CO₂ levels ∼1 ppm above background was revealed downwind of tree-kill areas. It contained a 1-km core with concentrations exceeding background by >3 ppm. Emission rates of ∼250 t d⁻¹ are indicated. Orographic winds may play a key role in transporting the diffusely degassed CO₂ upslope to elevations where it is lofted into the regional wind system.