Small impact of stratospheric dynamics and chemistry on the surface temperature of the Last Glacial Maximum in CESM2(WACCM6ma)

Abstract

Stratospheric dynamics and chemistry can impact the tropospheric climate through changing radiatively active atmospheric constituents and stratosphere-troposphere interactions. The impact of stratospheric dynamics and chemistry on the Last Glacial Maximum (LGM) climate is not well studied and remains an uncertain aspect of glacial-interglacial climate change.Here we perform coupled LGM simulations using the Community Earth System Model version 2 (CESM2), with a high-top atmosphere-the Whole Atmosphere Community Climate Model version 6 with a middle atmosphere chemistry mechanism (WACCM6ma). The CESM2(WACCM6ma) LGM simulations show a weaker stratospheric circulation than the preindustrial, 10-35% less tropospheric ozone and 10-50% more ozone in the lower stratosphere. These stratospheric dynamics and chemistry changes cause slightly colder (by <5%) LGM surface and tropospheric temperatures than parallel simulations using a low-top atmosphere model without active chemistry. The results suggest that stratospheric dynamics and chemistry have little direct effect on the glacial-interglacial climate change. Hosted filewaccm6ma_lgm.si.docx available at https://authorea.com/users/535865/articles/605841-smallimpact-of-stratospheric-dynamics-and-chemistry-on-the-surface-temperature-of-the-lastglacial-maximum-in-cesm2-waccm6maSmall impact of stratospheric dynamics and chemistry on the surface temperature of the Last Glacial Maximum in CESM2(WACCM6ma)