Exploring the effects of topography and land-ice coverage on Paleoproterozoic deglaciation

Abstract

The Paleoproterozoic glaciation (~2500-1600 Ma) was a time period in Earth’s history when its surface was completely covered in ice, creating a climate state known as a Snowball Earth. The Neoproterozoic glaciation (~1000-539 Ma), on the other hand, was a “Slushball" Earth climate state with partially ice-covered continents and open equatorial waters. This partial ice coverage and the presence of open equatorial waters during the Slushball period facilitated an active hydrological cycle, playing a key role in deglaciating the Earth during the Neoproterozoic. However, the process of transitioning from the Paleoproterozoic Snowball Earth to a Slushball Earth state (similar to the conditions seen during the Neoproterozoic) remains poorly understood. The complete ice coverage of the Snowball Earth shuts down the hydrological cycle, effectively isolating the oceans from the atmosphere and hindering deglaciation. This stark difference in the behavior of the hydrological cycle presents a challenge in explaining how the Paleoproterozoic Snowball Earth underwent a deglaciation process similar to the Neoproterozoic Slushball Earth. The buildup of CO₂ through volcanic emissions is a possible deglaciation mechanism for a Snowball Earth since oceanic ice coverage inhibits the removal of atmospheric CO₂ through weathering and the oceans. Experiments with varying CO₂ concentrations are currently being performed to test how high CO₂ needs to be to deglaciate a Snowball Earth but these simulations assume no permanent ice sheets or topography on land. To test the implications of varying topography and the extent of the ice sheets on how high CO₂ needs to be to deglaciate the Paleoproterozoic Snowball Earth we are designing new boundary condition files for a global climate model with a coupled dynamic ocean model (ROCKE-3D). The topography for these boundary condition files was edited by placing the elevation data from the Tibetan Plateau, Andes Mountains, and Rocky Mountains in various locations on the landmass. The land ice cover was edited by changing the maximum latitude at which ground ice was present.