Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.u22a..08k&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #U22A-08
Physics
0456 Life In Extreme Environments, 1605 Abrupt/Rapid Climate Change (4901, 8408), 1621 Cryospheric Change (0776), 5420 Impact Phenomena, Cratering (6022, 8136)
Scientific paper
Observational evidence indicates that the Precambrian Earth's history had episodes of total ice coverage of the planet. The Snowball Earth hypothesis states that the Sturtian (about 710 Ma) and Marinoan glaciations (about 635 Ma) were of global extent and lasted for several million years each. A variation of this hypothesis, called the Slushball Earth, requires milder conditions without substantial equatorial sea ice. The Snowball Earth glaciations would have ended abruptly in a greenhouse environment, whereas the Slushball would have experienced a slower deglaciation. Not only is the cause of a possible glaciation unclear, but the cause and mechanism of deglaciation is also debated. The goal of our study is to investigate if it is conceivable that a large-scale impact event might have triggered the deglaciation. The problem of the climatic effects of large impact events is not clear, as previously a Chicxulub-scale impact was suggested to induce global freezing. In terms of cratering rates, it is statistically plausible that the impact of a ~5 km diameter asteroid occurs during a "snowball period" with a duration of several million years. Most probably is an impact into the ice-covered ocean. In such a case a vapor plume with a total mass of n×1015 kg will rise up and then collapse over the atmosphere, creating a transient "hot spot". The more indirect consequences may include a global enrichment of the upper atmosphere with water vapors, dust and sea salt particles (in the case of an impact into ocean). Photochemical reactions should be taken into account for a further climatic modeling. At this point our simulations do not allow a conclusion if an impact of a realistic magnitude could cause deglaciation of a Snowball Earth.
Goodman Jeremy
Ivanov Boris A.
Koeberl Christian
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