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.