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Hydrological cycle changes explain weak Snowball Earth storm track despite increased surface baroclinicity
  • Tiffany A Shaw,
  • Robert James Graham
Tiffany A Shaw
University of Chicago

Corresponding Author:tas1@uchicago.edu

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Robert James Graham
University of Oxford
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Simulations show storm tracks were weaker during past cold, icy climates relative to the modern climate despite increased surface baroclinicity. Previous work explained the weak storm track using dry zonally-asymmetric mechanisms associated with orographic forcing. Here we show zonally-symmetric changes in the hydrological cycle explain the weak Snowball Earth storm track. According to the moist static energy framework, the weak storm track is connected to decreased latent heat flux (evaporation) and meridional surface moist static energy gradient. The weak storm track can be predicted using the Clausius-Clapeyron relation and a surface ice albedo. The weak storm track is also consistent with decreased latent heat release aloft in the tropics, which decreases upper-tropospheric baroclinicity and Mean Available Potential Energy, and is significantly correlated with the meridional surface moist static energy gradient. Our insights may apply to other climates such as the Last Glacial Maximum.
28 Oct 2020Published in Geophysical Research Letters volume 47 issue 20. 10.1029/2020GL089866