Early Eocene arctic climate sensitivity to pCO₂ and basin geography

We present results from new early Eocene (∼55-45 Ma) climate modeling experiments with the NCAR Community Climate System Model. These experiments test the sensitivity of climate to a large increase in atmospheric greenhouse gases, such as may have occurred at the Paleocene-Eocene (P-E) boundary (∼55.5 Ma), and also allow us to explore the role of Arctic basin configuration on climate. Experiments were run with pCO₂ at 560 and 2240 ppm, and a third experiment, at 2240 ppm, incorporates a passage to a neighboring ocean to explore the potential effect of the ocean on Arctic warming, were the Arctic not isolated. Quadrupling pCO₂ warms the Arctic by ∼8°C in the annual average, doubles atmospheric moisture content in this region and eliminates Arctic sea ice, consistent with proxy estimates of warming at the P-E boundary. Opening the Arctic Ocean warms mean annual sea surface temperature by an additional ∼4°C.