Climate and ocean circulation in the aftermath of a Marinoan snowball Earth
<p>When a snowball Earth deglaciates through a very high atmospheric <span class="inline-formula">CO<sub>2</sub></span> concentration, the resulting inflow of freshwater leads to a stably stratified ocean, and the strong greenhouse conditions drive the climate...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-04-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/18/759/2022/cp-18-759-2022.pdf |
| Summary: | <p>When a snowball Earth deglaciates through a very high atmospheric <span class="inline-formula">CO<sub>2</sub></span> concentration, the resulting inflow of freshwater leads to a stably stratified ocean, and the strong greenhouse conditions drive the climate into a very warm state. Here, we use a coupled atmosphere–ocean general circulation model, applying different scenarios for the evolution of atmospheric <span class="inline-formula">CO<sub>2</sub></span>, to conduct the first simulation of the climate and the three-dimensional ocean circulation in the aftermath of the Marinoan snowball Earth. The simulations show that the strong freshwater stratification breaks up on a timescale of the order of <span class="inline-formula">10<sup>3</sup></span> years, mostly independent of the applied <span class="inline-formula">CO<sub>2</sub></span> scenario. This is driven by the upwelling of salty waters in high latitudes, mainly the Northern Hemisphere, where a strong circumpolar current dominates the circulation. In the warmest <span class="inline-formula">CO<sub>2</sub></span> scenario, the simulated Marinoan supergreenhouse climate reaches a global mean surface temperature of about 30 <span class="inline-formula"><sup>∘</sup></span>C under an atmospheric <span class="inline-formula">CO<sub>2</sub></span> concentration of <span class="inline-formula">15×10<sup>3</sup></span> parts per million by volume, which is a moderate temperature compared to previous estimates. Consequently, the thermal expansion of seawater causes a sea-level rise of only 8 m, with most of it occurring during the first 3000 years. Our results imply that the surface temperatures of that time were potentially not as threatening for early metazoa as previously assumed. Furthermore, the short destratification timescale found in this study implies that Marinoan cap dolostones accumulated during the deglacial period, given that they were deposited under the influence of a freshwater environment.</p> |
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| ISSN: | 1814-9324 1814-9332 |