http://arxiv.org/abs/1810.01995
Motivated by the occurrence of a moderately nearby supernova near the beginning of the Pleistocene, we investigate whether nitrate rainout resulting from the atmospheric ionization of enhanced cosmic ray flux could have, through its fertilizer effect, initiated carbon dioxide drawdown. Such a drawdown could possibly reduce the greenhouse effect and induce the climate change that led to the Pleistocene glaciations. We estimate that the nitrogen flux enhancement onto the surface from an event at 50 pc would be of order 10%, probably too small for dramatic changes. We estimate deposition of iron (another potential fertilizer) and find it also to be too small to be significant. There are also competing effects of opposite sign, including muon irradiation and reduction in photosynthetic yield caused by UV increase from stratospheric ozone layer depletion. We conclude that the effect may be of interest from much nearer supernovae in the geological past, but more work needs to be done to clarify the magnitude of various competing effects.
A. Melott, B. Thomas and B. Fields
Fri, 5 Oct 18
38/53
Comments: N/A