Simulation of Martian Dust Effects on Polar CO2 Ice Caps and Atmospheric Circulation Using the MarsWRF Model. Issue 12 (16th December 2021) - Zhao, Yang
Abstract: Martian dust plays an important role in modulating climate. However, the effects of dust on polar CO2 ice caps, atmospheric circulation processes and the relationship between them are not yet clear. In this study, a Mars general circulation model (MarsWRF) was applied to investigate the impacts of the magnitude and timing of Martian dust storms on the spatiotemporal characteristics of polar CO2 ice caps and atmospheric circulation. The results show that dust can inhibit the sublimation of southern CO2 ice through the radiation effect. Under the "High Dust" scenario, the ice edge can extend up to 5° more equatorward than that under the "Standard" scenario around Ls = 220°. The extent of northern CO2 ice cap is hardly affected by dust because the impacts induced by dust mainly appear north of 80°N. By shifting the timing of maximum dust loading during the dust season, the "Early Dust" scenario inhibits the sublimation of the southern ice cap, while the "Late Dust" scenario accelerates the sublimation process. In addition, the variations in dust loading strength can lead to changes in three near‐surface wind belts, which are related to intensified Hardly circulation. The appearance of the warming vortex under the "Early Dust" scenario is delayed, and its intensity is 60 K lower than that observed in the "High Dust" and "Late Dust" scenarios. When dust loading increases, the northern CO2 condensation process in the Western Hemisphere accelerates, which is due to the increased pole‐to‐equator temperature gradient and the increased meridional wind speed. Plain Language Summary: Dust has a strong influence on the Martian climate. However, the dust effects on polar CO2 ice caps and wind fields have not yet been fully investigated. In this study, a numerical model that simulates the Martian climate was applied to investigate changes in the spatial and temporal patterns of CO2 ice caps and three‐dimensional wind fields. The results show that dust can inhibit the sublimation of southern CO2 ice by influencing the surface energy balance, while the coverage area of the northern CO2 ice cap is hardly affected by dust because the impacts induced by dust mainly appear north of 80°N. In terms of the timing of Martian dust storms, when a dust storm starts early (late), the sublimation of the southern ice cap is inhibited (accelerated). The appearance of the warming vortex will be delayed and its temperature will be 60 K lower than that in the general scenario if the dust storm starts early. When dust loading increases, the northern surface CO2 ice in the Western Hemisphere also increases, which is due to the increased pole‐to‐equator temperature gradient and increased meridional wind speed. Key Points: High dust loading decelerates the recession of southern CO2 ice cap, while the extent of northern CO2 ice cap is hardly affected by dust When Martian dust storm starts early, the appearance of the warming vortex is delayed and its intensity weakens The increase in northern surface CO2 ice is induced by the increased polar‐equator temperature gradient and the increased meridional flow