SENSITIVITY OF THE LATE PERMIAN CLIMATE TO BATHYMETRIC CHANGES, ATMOSPHERIC CO2 CONCENTRATIONS, AND THE IMPLICATIONS FOR THE MASS EXTINCTION

The largest mass extinction during the Paleozoic Era occurred near the Permian-Triassic boundary (ca. 252 Ma). The loss of biodiversity within the terrestrial and marine realms coincided with the eruption of the Siberian Flood Basalts as well as wide spread dysoxic, anoxic, and euxinic conditions in the oceans. A significant carbon isotope shift indicates perturbations in the carbon cycle occurred during the Late Permian and persisted into the Early Triassic. Despite several studies of the Permian-Triassic mass extinction, the exact mechanism that may have triggered such an extinction event is still controversial. Recent studies suggest extreme volcanism may have increased the CO₂ content of the atmosphere resulting in positive feedback loop. To assist with the determination of the overall global climatic conditions that may have contributed to the Permian-Triassic extinction, the combining of climate model simulations with mapping of phytogeographic patterns and climate sensitive sediments could be an invaluable method.

Sensitivity experiments conducted with the National Center for Atmospheric Research's (NCAR) Community Climate System Model v. 3 (CCSM3), a comprehensive fully coupled model, were performed with variations in atmospheric CO₂ concentrations, bathymetric features and orbital settings. Previous models on the Late Permian climate have largely been done with a flat-bottom ocean configuration. Past global biome studies have focused on the climatic changes that occurred during the Early and Middle Permian rather than the Late Permian due to the lack of available fossil evidence. Simulations completed in this study suggest sills isolating the deep-water exchange between the Paleo-Tethys and Panthalassa Oceans enhanced stratification of the Paleo-Tethys leading to a reduced oxygen concentration of the water masses. Sensitivity experiments conducted for this project combined the simulation of biomes with the mapping of phytogeographic patterns and climate sensitive sediments for a broader understanding of the end-Permian climate.