The South Polar Residual Cap and Secular Climate Change on Mars: What Can We Learn From Observations and Models?

Details The South Polar Residual Cap and Secular Climate Change on Mars: What Can We Learn From Observations and Models? The South Polar Residual Cap and Secular Climate Change on Mars: What Can We Learn From Observations and Models?

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p53a..06h&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #P53A-06

Physics

[0325] Atmospheric Composition And Structure / Evolution Of The Atmosphere, [0343] Atmospheric Composition And Structure / Planetary Atmospheres, [0350] Atmospheric Composition And Structure / Pressure, Density, And Temperature

Scientific paper

The prospect for multi-decadal secular climate change on Mars is a new concept that stems from observations of an apparently eroding South Polar Residual Cap (SPRC). Several years ago MOC images of the growth of circular depressions in the SPRC were interpreted to imply a net annual loss of approximately 2-10 x 10**9 m**3 of CO2 between 1999 and 2001 [1]. More recent studies using CTX images suggest a smaller loss, but one that is still potentially significant [2]. Taken together these data imply that if the all the CO2 sublimating from the SRPC goes into the atmosphere, as seems likely [3], an upper limit for the equivalent rate of increase in globally averaged surface pressure should be ~ 4 Pa per Mars Decade. About one and a half Mars decades have elapsed since the beginning of the Viking mission and the end of the Phoenix mission. If the net erosion of the SPRC has been steady during this period at the rate listed above, it would have produced about a 6 Pa increase in the global and annual mean surface pressure. Could such an increase be detected in the Viking and Phoenix pressure data? Clearly, this is a challenging question to answer, but one we feel needs careful examination. We report here the analysis of these data sets and the use of models to interpret them. Models are needed because surface pressure measurements at a few sites do not directly yield global mass budgets because dynamical processes and scale height changes influence surface pressure as well as seasonal exchange with the polar caps [4]. To reduce model uncertainties, we employ an ensemble of independently developed models including the NASA/Ames and LMD General Circulation Models, and the OSU MMM5 Mesoscale Model. References: [1] Malin, M.C. et al. (2001), Science, 294, 2146-2148. [2] Thomas, P. et al. (2009), Icarus, submitted. [3] Haberle, R.M. et al. (2009), 3rd International Workshop on Mars Polar Energy Balance and the CO2 Cycle (/http://www.lpi.usra.edu/meetings/mpeb2009). [4] Hourdin, F. et al. (1993) J. Atmos. Sci., 50, 3625-3640.

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