| Summary: | Sea ice schemes with a few vertical levels are typically used to simulate the thermodynamic evolution of sea ice in global climate models. Here it is shown that these schemes overestimate the magnitude of the diurnal surface temperature cycle by a factor of 2–3 when they are used to simulate tropical ice in a Snowball earth event. This could strongly influence our understanding of Snowball termination, which occurs in global climate models when the midday surface temperature in the tropics reaches the melting point. A hierarchy of models is used to show that accurate simulation of surface temperature variation on a given time scale requires that a sea ice model resolve the e-folding depth to which a periodic signal on that time scale penetrates. This is used to suggest modifications to the sea ice schemes used in global climate models that would allow more accurate simulation of Snowball deglaciation. © 2010 American Meteorological Society. Manuscript received 24 February 2010, in final form 28 June 2010. We thank Stephen Warren, Cecilia Bitz, and an anonymous reviewer for comments. DSA was supported by the T. C. Chamberlin Fellowship of the University of Chicago and the Canadian Institute for Advanced Research. IE was supported a Prize Postdoctoral Fellowship through the California Institute of Technology Division of Geological and Planetary Sciences and a NOAA Climate and Global Change Postdoctoral Fellowship administered by the University Corporation for Atmospheric Research. This work was supported by the NSF P2C2 program (ATM-0902844) and NSF ATM-0933936. Published - Abbot2010p12357J_Climate.pdf
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