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The Jormungand Global Climate State and Implications for Neoproterozoic Glaciations


IPGP - Îlot Cuvier


Séminaires Géochimie

Salle 310

Dorian Abboot

University of Chicago (USA)

Geological and geochemical evidence can be interpreted as indicating strong hysteresis in global climate during the Neoproterozoic glacial events (~630 Ma and ?715 Ma). Standard climate theory only allows such strong hysteresis if global climate enters a fully-glaciated “Snowball” state. However, the survival of photosynthetic, eukaryotic, marine species through these glaciations may indicate that there were large areas of open ocean. A previously-proposed “Slushball” model for Neoproterozoic glaciations could easily explain the survival of these organisms because it has open ocean throughout the tropics, but there is only a small amount of hysteresis associated with the Slushball state. I will propose a new state of global climate, the Jormungand state, that is nearly, but not completely, ice-covered. I analyze this state using global climate models and the Budyko-Sellers model, and find that there is strong hysteresis associated with it as greenhouse gas levels are varied. This makes the Jormungand state a potential model for Neoproterozoic glaciations.