Simulated Modes Of Variability In the Permian (251 Ma): The North Panthalassic Oscillation

An Arctic Oscillation-type variability is found and investigated in two multi-millennia fully coupled climate simulations of the Permian/Triassic (251Ma) period using the Community Climate System Model, Version 3 (CCSM3). We refer to this mode of variability as the North Panthalassic Oscillation (NPO) and diagnose its character in both Permian experiments. The first simulation is a realistic representation of the Permian/Triassic boundary where CO2 levels are set to 10 times present day values. The NPO in this experiment manifests in the western Panthalassic Ocean (akin to the Pacific Ocean). The second simulation represents a much colder Permian world where CO2 levels are set to present day values. In this experiment, the NPO demonstrates its ability to change its maximum variance location from eastern Panthalassa (akin to the Atlantic Ocean) to western Panthalassa, by the end of the simulation. The NPO's ability to flip dominance location is influenced by sea ice expansion into eastern Panthalassa and subsequent changes in baroclinicity and storm tracks. Tropical precipitation is also shown to play a smaller role in the cold case where the mid-latitude connection to the tropics is stronger.