Radiative effects of the ozone layer on Snowball Earth
Abstract
Geochemical and geological evidence suggested that atmospheric oxygen rose from about 2% to about 10% of the present atmospheric level over the period of 750-580 million years ago when several nearly global glaciations or Snowball Earth events formed. The increase in oxygen would lead to an increase in ozone concentration in the atmosphere. Since ozone is a greenhouse gas, changes in ozone concentration would alter surface temperatures. Thus, ozone changes would have important influences on Snowball Earth formation or deglaciation. Previous works for either the initiation or the deglaciation of the hard Snowball Earth have not taken the radiative effects of the ozone layer into account. Here, we study this issue by carrying out simulations using an atmospheric general circulation model with various ozone concentrations and spatial distributions. Simulation results show that as O3 concentration is uniformly reduced from 100% to 50%, the global-mean surface temperature is decreased by approximately 1 K, and the largest decrease is located at the subpolar region, with values up to 3 K. As ozone concentration is reduced, the ozone layer is lowered, and weak ozone transport from the tropics to higher latitudes, surface temperature is decreased by approximately 1 K in the tropics and by about 6 K in polar regions. These results suggest that simulations with the present-day ozone concentration and spatial distributions would overestimate (underestimate) the CO2 threshold required to initiate (terminate) the Snowball Earth.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.P11G..02H
- Keywords:
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- 0340 ATMOSPHERIC COMPOSITION AND STRUCTURE / Middle atmosphere: composition and chemistry;
- 0343 ATMOSPHERIC COMPOSITION AND STRUCTURE / Planetary atmospheres;
- 4926 PALEOCEANOGRAPHY / Glacial;
- 4926 PALEOCEANOGRAPHY / Glacial