Science Projects

Coupling the CO2 and Dust Cycles

The Viking Landers measured a highly repeatable annual cycle of surface pressure, which suggests that the CO2 cycle has very little interannual variability. This is intriguing given the highly variable nature of the dust cycle and the reasonable assumption that interactions between the dust and CO2 cycles affect the CO2 cycle. We are utilizing the GCM to explore coupling mechanisms between the dust and CO2 cycles with the goal of identifying possible feedbacks that could explain the repeatable nature of the CO2 cycle. The first paper that resulted from this work (Kahre and Haberle, 2010; in press [link to Icarus]) focuses on the effects of airborne dust on the amount of CO2 that condenses on the seasonal CO2 caps. We have found that increasing the atmospheric dust loading suppresses CO2 condensation when the CO2 ice emissivity is high but enhances CO2 condensation when the CO2 ice emissivity is low. This result illuminates the possibility that the CO2 cycle is repeatable because the CO2 ice emissivity is equal to a value such that varying the dust loading does not change the CO2 condensation rate.

The second part of this work is in progress and focuses on the effects of incorporating varying amounts of dust in the seasonal CO2 ice caps on the ice albedo (reflectivity). Since the albedo of the surface affects polar energy balance, we are investigating the sensitivity of the CO2 cycle to self consistently time-varying ice albedos.