Atmospheric History of H<sub>2</sub> Over the Past Century Reconstructed From South Pole Firn Air
John D. Patterson, Murat Aydın, Andrew M. Crotwell, Gabrielle Pétron, Jeffrey P. Severinghaus, E. S. Saltzman
Abstract
Abstract Molecular hydrogen (H 2 ) is an abundant and reactive constituent of Earth's atmosphere, with links to climate and air quality. Anthropogenic emissions of H 2 are expected to rise as the use of H 2 as an energy source increases. Documenting past variations in atmospheric H 2 will help to validate current understanding of the global H 2 budget. The modern instrumental record begins in the 1980s; there is little information about atmospheric H 2 prior to that time. Here, we use firn air measurements from a 2001 South Pole campaign to reconstruct atmospheric H 2 levels over the 20th century. Inversion of the measurements indicates that H 2 over South Pole has increased from 350–540 ppb from 1910–2000. A biogeochemical box model indicates that the atmospheric burden of H 2 increased by 37% over that time. The rise in H 2 is consistent with increasing H 2 emissions from fossil fuel combustion and increasing atmospheric production from methane oxidation.