HR: 1340h
AN: PP23B-1337    [Abstracts]
TI: The Transition From the Present-Day Climate to a Snowball Earth Simulated With a Comprehensive Climate Model
AU: * Voigt, A
EM: aiko.voigt@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg, 20146, Germany
AU: * Voigt, A
EM: aiko.voigt@zmaw.de
AF: International Max Planck Research School on Earth System Modelling, Bundesstrasse 53, Hamburg, 20146, Germany
AU: Marotzke, J
EM: jochem.marotzke@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg, 20146, Germany
AB: Recently, Marotzke and Botzet (2007) have shown that in a comprehensive climate model both the current climate and a completely ice-covered Earth are stable states under today's total solar irradiance (TSI) and greenhouse gas concentrations. By setting TSI to near-zero they were able to cause a transition from the present-day climate to the ice-covered state within 15 years [1]. In order to study the bifurcation point, we have repeated this experiment with the same model, i.e. the Max Planck Institute for Meteorology coupled atmosphere-ocean general circulation model ECHAM5/MPI-OM, at lower resolution (horizontally T31 in the atmosphere and 3.0 degrees in the ocean). We give estimates for the critical values of TSI and greenhouse gas concentrations needed to trigger the transition from the present-day to the ice- covered state. Starting from today's climate and setting TSI to 44% of today's value leads to a glaciation within 30 years. Furthermore, we investigate the degree of oceanic ice-cover needed for an unstoppable glaciation. We find that only an almost completely ice-covered ocean guarantees that the model does not return to the present-day climate when TSI is reset to its today's value. Our results indicate that a snowball Earth could, in principle, be triggered by a brief decrease of TSI. [1] Marotzke, J. and M. Botzet (2007), Present-day and ice-covered equilibrium states in a comprehensive climate model, Geophys. Res. Lett., Vol. 34, No. 16, L16704, doi:10.1029/2006GL028880
DE: 1600 GLOBAL CHANGE
DE: 4928 Global climate models (1626, 3337)
DE: 4930 Greenhouse gases
DE: 4934 Insolation forcing
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting