Atmospheric Responses to a Tropical Dust Storm and Their Role in North Polar Ice Cap Reduction on Mars

Abstract Using observations from the Mars Climate Sounder (MCS) and images from the Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter (MRO), this study identifies a suppression of north polar ice cap expansion before the northern fall equinox (Ls ∼160°) in Martian Year 36 (MY36) compared to the same season in other years. This reduction coincides with an earlier‐occurring tropical regional dust storm (Z storm). Simulations using the Mars Planetary Climate Model (PCM), along with a control experiment that excludes the Z storm, show an unusual decrease in atmospheric water vapor in the northern polar region, indicating that the ice cap anomaly is linked to dust storm–induced changes in atmospheric circulation and water transport. The Mars PCM simulations capture the key features of atmospheric temperature and water vapor changes during the Z storm period. To understand how the Z storm influenced polar water vapor, we conducted two PCM simulations for MY36: one representing the actual dust storm conditions and another representing a control experiment without the storm. Dynamical analysis showed that tropical dust activity excited anomalous planetary waves, which propagated poleward and affected the polar background circulation. As a result, circulation patterns in the lower polar atmosphere, including eastward zonal winds and meridional flows, were significantly disrupted, substantially reducing poleward water vapor transport to the northern polar region. These results provide new insights into the role of dust‐related climate processes in modulating polar ice accumulation, contributing to a deeper understanding of the mechanisms driving long‐term climate evolution on Mars.