Terrestrial Ozone Depletion Due to a Milky Way Gamma-Ray Burst

• Published in: arXiv.org 2005-02
• Main Authors: Thomas, Brian C, Jackman, Charles H, Melott, Adrian L, Laird, Claude M, Stolarski, Richard S, Gehrels, Neil, Cannizzo, John K, Hogan, Daniel P
• Format: Article
• Language: English
• Subjects: Atmospheric models; Gamma ray astronomy; Gamma ray bursts; Gamma rays; Milky Way Galaxy; Nitrogen dioxide; Ozone depletion; Two dimensional models
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0411284

Based on cosmological rates, it is probable that at least once in the last Gy the Earth has been irradiated by a gamma-ray burst in our Galaxy from within 2 kpc. Using a two-dimensional atmospheric model we have performed the first computation of the effects upon the Earth's atmosphere of one such impulsive event. A ten second burst delivering 100 kJ/m^2 to the Earth penetrates to the stratosphere and results in globally averaged ozone depletion of 35%, with depletion reaching 55% at some latitudes. Significant global depletion persists for over 5 years after the burst. This depletion would have dramatic implications for life since a 50% decrease in ozone column density results in approximately three times the normal UVB flux. Widespread extinctions are likely, based on extrapolation from UVB sensitivity of modern organisms. Additional effects include a shot of nitrate fertilizer and NO2 opacity in the visible providing a cooling perturbation to the climate over a similar timescale. These results lend support to the hypothesis that a GRB may have initiated the late Ordovician mass extinction (Melott et al. 2004).