CO 2 emissions from the Yellowstone volcanic system

Two methods are used to estimate CO 2 degassing from the Yellowstone magmatic‐hydrothermal system. The amount of magmatic CO 2 released as basaltic magma emplaces from the mantle into the crust beneath the Yellowstone caldera is calculated and compared to CO 2 fluxes measured in three different types of hydrothermal regions within Yellowstone. Comparison of modeled estimates with surface measurements suggests that 3.7 ± 1.3 × 10 11 mol y −1 (45 ± 16 kt d −1 ) of CO 2 are released from Yellowstone due to diffuse degassing. Flux measurements suggest that the diffuse flux in acid‐sulfate regions is significant in total calculations (>96% of the total), whereas the diffuse flux in neutral‐chloride and travertine‐precipitating areas is not significant. Analyses of carbon and helium isotopes suggest that ∼50% of the CO 2 emitted is derived from sedimentary sources at locations outside the caldera, whereas locations inside the caldera likely have sedimentary contributions <30%. In addition to release of CO 2 with emplacement, magma crystallization in the subsurface is thought to contribute significantly to the CO 2 emissions at the surface. The contribution of CO 2 from Yellowstone to global volcanic CO 2 emissions (∼6–7 × 10 12 mol y −1 ) is comparable to the CO 2 contribution from other large volcanic systems like Popocatepetl, Mexico and the combined contribution from the Hawaii hot spot. Likewise, the amount of CO 2 emitted per land area from Yellowstone (on average 10 8 mol CO 2 km −2 y −1 ) is comparable to other large volcanic and hydrothermal systems worldwide.