Modeling the “B” Regional Dust Storm on Mars: Dust Lofting Mechanisms Predicted by the New NASA Ames Mars GCM

During years in which Mars does not experience a Global Dust Storm, the Thermal Emission Spectrometer (TES) instrument on Mars Global Surveyor (MGS) and the Mars Climate Sounder (MCS) instrument on Mars Reconnaissance Orbiter (MRO) have observed three annually-recurring regional-scale dust storms that occur in the southern hemisphere during southern spring and summer. These storms produce dust extinctions in excess of 10−3 km−1 and increase temperatures to over 200 K in the middle atmosphere (50 Pa, or ∼25 km). Whereas the first and last storms in the occurrence are located in the middle latitudes, the second storm, known as the “B” storm, is confined to the south pole over the receding CO2 ice cap. In this work, we reproduce the “B” storm in the new NASA Ames Mars Global Climate Model (MGCM), and we use our simulation to investigate the mechanisms lofting dust into the middle atmosphere during the storm. We find that a series of semi-regular dust pluming events that occur poleward of 70° S loft dust to and above 50 Pa during the “B” storm. These plumes share some characteristics with rocket dust storms and often produce detached dust layers whose subsequent evolution resembles the solar escalator effect.