Impact of Interactive Ozone on Climate Reconstruction in an Earth System Model: the Case of Antarctica in mid-Holocene

Abstract:

Stratospheric ozone change can influence on tropospheric climate. For example, Sigmond and Fyfe (2010) pointed out the Antarctic sea ice could increase due to the Antarctic ozone hole: Stratospheric cooling due to the ozone hole increases a westerly anomaly of the polar night jet by satisfying the thermal wind balance, and annular mode response increases westerly anomaly near the surface. The increase of the surface westerly intensifies the northward component of the Ekman transport in the ocean and promotes the sea ice transport to lower latitudes. However, the impact of ozone change in paleoclimate has not been investigated in detail. In most of paleoclimate experiments of CMIP5/PMIP3, the distribution of ozone is fixed to the estimated value of 1850 AD despite the ozone distribution depends on the solar radiation distribution as a function of latitude and time (season). This treatment may cause some bias to the simulation results. In this study, therefore, we examine the impacts of forecasted ozone distribution in paleoclimate experiments with an Earth system model. In this presentation, we focus on the Antarctic region in the mid-Holocene (6k year before present, hereafter MH) experiment, where significant impact is obtained.

We utilize Japan Meteorological Agency Meteorological Research Institute (JMA-MRI) Earth system model, which is a coupled model of the atmosphere-ocean-aerosol general circulation model of MRI-CGCM3 (Yukimoto et al., 2012) which was used in CMIP5 and the chemistry model of MRI-CCM2 (Deushi and Shibata, 2011). We examine the MH experiment and the preindustrial control experiment under the condition of 1850 AD, both of which are corresponding to CMIP5.

We investigated the impact of the ozone variations to climate by the change of orbital parameters of the Earth. The Antarctic sea ice in spring decreases through the deceleration of the westerly jet due to the increase of stratospheric ozone. As a result, temperature anomaly is up to about 1 K near the surface. This result suggests that the ozone distribution consistent with the solar insolation in the targeted era should be used in paleoclimate simulations in order to improve the accuracy of the climate reconstruction in the polar regions.