Reconstruction of Paleofire Emissions Over the Past Millennium From Measurements of Ice Core Acetylene

Acetylene is a short-lived trace gas produced during combustion of fossil fuels, biomass, and biofuels. Biomass burning is likely the only major source of acetylene in the preindustrial atmosphere, making ice core acetylene a powerful tool for reconstructing paleofire emissions. Here we present a 2,000-year atmospheric record of acetylene reconstructed from analysis of air bubbles trapped in Greenland and Antarctic ice cores and infer pyrogenic acetylene emissions using a chemistry transport model. From 0 to 1500 CE, Antarctic acetylene averages 36 +/- 1 pmol mol(-1) (mean +/- 1 SE), roughly double the annual mean over Antarctica today. Antarctic acetylene declines during the Little Ice Age by over 50% to 17 +/- 2 pmol mol-1 from 1650 to 1750 CE. Acetylene over Greenland declines less dramatically over the same period. Modeling results suggest that pyrogenic acetylene emissions during 1000-1500 CE were sustained at rates significantly greater than modern day and declined by over 50% during the 1650-1750 CE period.