Atmospheric transport into polar regions on Mars in different orbital epochs

The variation of the transport of air into Martian polar regions with obliquity is examined using a series of MarsWRF general circulation model simulations which include idealized age of air and exponential decay tracers. These show substantial changes in the circulation, polar vortex structure, and tracer transport with changes in obliquity. These changes are non-monotonic with respect to obliquity, as well as differing between the summer and winter polar regions. In particular, there is an increase in the rate of vertically-integrated transport of air to the winter pole as obliquity increases from 5° to 25° followed by a decrease from 25° to 55°, with generally the reverse trends for transport to the summer pole. This behavior suggests that the amount of dust transport into polar regions will vary with obliquity, and could contribute to the apparent cyclical deposition of dust in polar regions as expressed in the polar layered deposits. Furthermore, the non-monotonic variation with obliquity suggests that visible changes in the appearance of polar layering may vary on a cycle with half the period of the cycle over the full obliquity variation range.