Glacial‐Interglacial Controls on Ocean Circulation and Temperature during the Permo‐Carboniferous

The apex of Earth's penultimate icehouse during the Permo-Carboniferous coincided with dramatic glacial-interglacial fluctuations in atmospheric CO2, sea level, and high-latitude ice. Global transformations in marine fauna also occurred during this interval, including a rise to peak foraminiferal diversity, suggesting that glacial-interglacial climate change impacted marine ecosystems. Nevertheless, changes in ocean circulation and temperature over the Permo-Carboniferous and their influence on marine ecosystem change are largely unknown. Here, we present simulations of glacial and interglacial phases of the latest Carboniferous-early Permian (similar to 305-295 Ma) using the Community Earth System Model version 1.2 to provide estimates of global ocean circulation and temperature during this interval. We characterize general patterns of glacial and interglacial surface ocean currents, temperature, and salinity, and compare them to the documented abundance and distribution of Permo-Carboniferous marine fauna as well as a preindustrial climate simulation. We then explore how glacial-interglacial changes in atmospheric CO2, sea level, and high-latitude ice extent impact thermohaline circulation. We find that glacial-interglacial changes in equatorial surface temperatures are consistently similar to 3-6 degrees C. Ocean circulation is stronger overall in the glacial simulation, particularly as lower atmospheric CO2 enables deep convection in the Northern Hemisphere. Wind-driven circulation, heat transport, and upwelling intensity are stronger overall in the Permo-Carboniferous superocean relative to the preindustrial oceans at the same level of atmospheric CO2. We also find that CO2-induced glacial conditions of the early Permian may have promoted foraminiferal diversity through increased thermal gradients and suppressed riverine input in marine shelf environments.