Joint Seminar: The Jormungand Global Climate State and Implications for Snowball Earth

Geological and geochemical evidence can be interpreted as indicating strong hysteresis in global climate during the Neoproterozoic glacial events (~630 Ma and ~715 Ma). Previous 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. In this paper a new state of global climate, the "Jormungand" state, is proposed. In this state the ocean is very nearly globally ice-covered, but a very small strip of the tropical ocean remains ice-free. The Jormungand state results from the interaction of atmospheric and cryospheric dynamics and shows strong hysteresis when greenhouse gas levels are varied, as illustrated here in two different atmospheric global climate models and in the Budyko-Sellers model. By offering a scenario that could naturally explain both the strong hysteresis and the survival of life, the Jormungand state represents a potential model for Neoproterozoic glaciations, although further study of this issue is needed.

Date

23.03.2011

Time

13:30 h

Place

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

Speaker

Dorian Schuyler Abbot, University of Chicago

Organizers

Aiko Voigt

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