Hydrocode simulation of the Chicxulub impact event and the production of climatically active gases

We constructed a numerical model of the Chicxulub impact event using the Chart-D Squared (CSQ) code coupled with the ANalytic Equation Of State (ANEOS) package. In the simulations we utilized a target stratigraphy based on borehole data and employed newly developed equations of state for the materials that are believed to play a crucial role in the impact-related extinction hypothesis: carbonates (calcite) and evaporites (anhydrite). Simulations explored the effects of different projectile sizes (10 to 30 km in diameter) and porosity (0 to 50%). The effect of impact speed is addressed by doing simulations of asteroid impacts (v_i=20km/s) and comet impacts (v_i=50km/s). The masses of climatically important species injected into the upper atmosphere by the impact increase with the energy of the impact event, ranging from 350 to 3500 Gt for CO₂, from 40 to 560 Gt for S, and from 200 to 1400 Gt for water vapor. While our results are in good agreement with those of Ivanov et al. [1996], our estimated CO₂ production is 1 to 2 orders of magnitude lower than the results of Takata and Ahrens [1994], indicating that the impact event enhanced the end-Cretaceous atmospheric CO₂ inventory by, at most, 40%. Consequently, sulfur may have been the most important climatically active gas injected into the stratosphere. The amount of S released by the impact is several orders of magnitude higher than any known volcanic eruption and, with H₂O, is high enough to produce a sudden and significant perturbation of Earth's climate.