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Asymmetric Impacts on Mars’ Polar Vortices From an Equinoctial Global Dust Storm
Author(s) -
Streeter Paul M.,
Lewis Stephen R.,
Patel Manish R.,
Holmes James A.,
Fedorova Anna A.,
Kass David M.,
Kleinböhl Armin
Publication year - 2021
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2020je006774
Subject(s) - polar vortex , mars exploration program , atmospheric sciences , storm , vortex , geology , polar , dust storm , climatology , martian , jet stream , physics , geophysics , jet (fluid) , stratosphere , meteorology , astrobiology , oceanography , astronomy , mechanics
Mars possesses dynamical features called polar vortices: regions of cold, isolated air over the poles circumscribed by powerful westerly jets which can act as barriers to transport to dust, water, and chemical species. The 2018 Global Dust Storm was observed by multiple orbiters and offered a valuable opportunity to study the effects of such a storm on polar dynamics. To this end, we assimilate data from the Mars Climate Sounder and Atmospheric Chemistry Suite into a Mars Global Climate Model. We find that the storm had asymmetrical hemispherical impacts, with the northern vortex remaining relatively robust while the southern vortex was substantially diminished in its intensity. We propose that this asymmetry was due both to the storm’s latitudinal extent, as it extended further south than north, and to its equinoctial timing, occurring as the southern vortex was already decaying. We show that both polar vortices, in particular the northern, were reduced in ellipticity by the storm. There was a well‐correlated reduction in stationary topographic wave activity at high latitudes in both hemispheres. We demonstrate that the characteristic elliptical Martian polar vortex shape is the pattern of the stationary waves, which was suppressed by the shifting of the polar jet away from regions of high mechanical forcing (north) or reduction of polar jet intensity by a reduced meridional temperature gradient (south). These asymmetric effects suggest increased transport into the southern (but not northern) polar region during global dust storms at northern autumn equinox, and more longitudinally symmetric transport around both poles.