| Summary: | The continuity of life evolution over 3.5 billion years has been attributed to Earth's ability to maintain a habitable climate. However, the Neoproterozoic era was interrupted by multiple Snowball Earth episodes when the silicate weathering thermostat broke down and global-scale glaciations ensued. It remains a major challenge to explain how life has survived these severe glaciations, which depends critically on the surface temperature. The work presented in this thesis contains a series of modeling endeavors dedicated to advancing our understanding of the temperature history during the Snowball Earth events. With an energy balance model, we demonstrate that the critical phase for life is the early stage of Snowball, when surface temperature has plunged after the initiation. Using the FOAM GCM specially modified for the Snowball climate, we investigate the peculiar hydrological cycle of a Snowball state. With an idealized ice shell model, we study how the global-scale ice flow may act as a dust conveyor belt and escalate dust accumulation in the tropical ablation zone. We then explore the stability of the dusty Snowball state in a coupled atmosphere-ice-dust model. We propose a dust thermostat mechanism based on the coupled model simulations of the dusty ice scenario, which suggests that the Snowball Earth might have been much warmer than previously thought.
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