Abstract:
Biomass burning is an important component of the earth system that is closely connected to climate. The relationship between fire and climate on multi-millennial timescales is not well understood, in part, because of the difficulty of reconstructing trends in fire activity. Quantitative estimates of paleo-fire and paleo-fire emissions would help validate earth system models used to project future fire in a changing climate. In this dissertation, new measurements of acetylene from Greenland and Antarctic ice cores spanning the last 21,000 years are presented. Acetylene is a trace gas produced solely by biomass burning in the pre-industrial atmosphere. The idea behind this work is the variations in the atmospheric levels of acetylene contain a quantitative history of paleo-fire emissions.
Measurements of acetylene were made on Greenland ice core samples ranging in age. The analyses were done by wet extraction of gases from ice core samples. Tandem gas chromatography and high-resolution mass spectrometry were utilized to separate and quantify acetylene in ice core samples. Inferred acetylene emissions and dry matter burned from paleofire are obtained using modeled sensitivities and biomass burning emission factors.
Acetylene measurements on Greenland and Antarctic ice show a significant increase from glacial to interglacial conditions for Greenland and Antarctica. Assuming the atmospheric lifetime and transport has not changed dramatically, the data indicate that global biomass burning (dry matter burned, Pg yr-1) increased 3-fold between the glacial and interglacial. The paleo-fire record inferred from acetylene is compared to records from other fire proxies such as charcoal and stable isotopic composition of methane.
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