The Snowball Stratosphere
Abstract
Earth has experienced low-latitude glaciations (Snowball Earth states) in both the Paleoproterozoic and Neoproterozoic. Prior studies have used global climate models (GCMs) to examine the effects such an extreme climate state might have on the structure and dynamics of Earth's troposphere, but the behavior of the stratosphere has not been modeled. Understanding the Snowball stratosphere is essential for developing an accurate account of the Earth's radiative and chemical properties during these episodes. In this contribution we conduct the first detailed analysis of the stratosphere of the Snowball Earth using simple theoretical calculations and ECHAM5 GCM simulations. We present three main findings: 1.) Snowball-induced changes in the cross-tropopause mass exchange rate are balanced by corresponding changes in the stratospheric mixing efficiency. This means that our results do not affect existing oxygen isotope-based estimates of Snowball pCO2. 2.) The amplitude of wave activity fluxes in the stratosphere of the Snowball are substantially different from those of the modern case, which may alter high-altitude chemistry, momentum, and heat distribution relative to the modern Earth. 3.) The Snowball stratosphere consistently reaches temperatures cool enough for the formation of nacreous stratospheric clouds over both the poles and the equator. These clouds play a role in the depletion of ozone and can generate strong greenhouse warming. Further investigation into whether these clouds were widespread during the Snowball is necessary given their potential impact on deglaciation scenarios and proposals for the distribution of "refugia" for life during the glaciation. This work shows how even the remote stratosphere can have an important effect on the surface and surviving geological evidence from climatic events in the distant past.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP53E1251G
- Keywords:
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- 1199 General or miscellaneous;
- GEOCHRONOLOGYDE: 1599 General or miscellaneous;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1620 Climate dynamics;
- GLOBAL CHANGEDE: 4914 Continental climate records;
- PALEOCEANOGRAPHY