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The icy demise and revamping of GFDL's ESM2G Earth System Model
Robert Hallberg, Alistair Adcroft, John Dunne, Stephen Griffies, John Krasting
NOAA/GFDL
(Abstract received 12/17/2010 for session X)
ABSTRACT
GFDL is preparing two new 1-degree ocean resolution coupled earth-system models for submission to the IPCC AR5 - ESM2M and ESM2G - both based on the atmospheric model from of GFDL's CM2.1 coupled climate model. The ESM2G differs ESM2M only in their ocean components - an isopycnal coordinate Generalized Ocean Layered Dynamics (GOLD) configuration in the case of ESM2G, compared with a Z*-coordinate MOM4.1 configuration for ESM2M. Because the biogeochemistry takes so long to come into equilibrium, these models were spun up for more than 2000 years with preindustrial forcing. This was the first time that a GOLD-based coupled model was run for such a long time. Despite an attempt to use similar diapycal diffusivities, the abyssal oceans in ESM2M and ESM2G drifted significantly in opposite directions. In the case of ESM2G, the cold abyssal drift eventually led to such large surface cooling that the climate state became problematic. This talk documents the importance of the interior-ocean diapycal diffusivity to the long-term ocean evolution, and describes the changes to a second long run of ESM2G that might have led to a viable Earth System Model.
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2011 LOM Workshop, Miami, Florida February 7 - 9, 2011