Collaborative Research: Investigating the Rate of Potential Biological in Situ Gas Production of CO and CH4 in Arctic Ice

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Atmospheric gas records developed from polar ice cores are cornerstones of climate change science. The overarching goal of this project is to develop and apply new understanding of high-time-resolution Arctic records of methane and carbon monoxide. Methane is a powerful greenhouse gas and carbon monoxide is linked to the atmospheric lifetime of other greenhouse gases including carbon dioxide. Thus, developing reliable records of both gases is important for understanding past and future atmospheric chemistry and radiative forcing. High-depth-resolution records of carbon monoxide, and to a lesser extent methane, in Arctic ice cores show evidence of non-atmospheric anomalies that are poorly understood. One potential source of such anomalies is biological activity within the ice. Microbes can be active at temperatures well below freezing, and ice cores are subjected to relatively warm temperatures after the ice is extracted from glaciers and ice sheets while they are stored or transported prior to measurement. Special sample handling protocols will be used to evaluate the effects of post-collection ice temperature on methane and carbon monoxide production, and potentially allow development of methane and carbon monoxide records over recent centuries that are free from any artifacts. Funding will support early career investigators, graduate students and undergraduate students who will be involved in field work, laboratory analysis, and data interpretation. The investigators will involve undergraduates from underrepresented groups to foster diversity in earth sciences. Public outreach will be achieved through public lectures, lab tours, and media interactions. The specific goals of this project are to (1) investigate the rate and timing of temperature-dependent in situ biological production of carbon monoxide and methane in an Arctic ice core, (2) develop records of atmospheric carbon monoxide and methane spanning recent centuries that are free of in situ production artifacts, and (3) determine the roles that ice impurity concentration and microbial community structure play in situ gas production. To accomplish these goals, a 150-meter ice core will be collected at Summit, Greenland using the large-diameter Blue Ice Drill. To address goal (1), successive measurements of carbon monoxide and methane will be made in the field on eight parallel longitudinal samples from a 12 meter-long section of the core, with the different samples consistently stored and monitored at temperatures ranging from well below the -31 °C ice sheet temperature at Summit to well above the -26 °C cell vitrification temperature where cellular metabolism is possible. For goal (2), measurements of these two gases will be made in the field on ice that has been kept consistently at -40 °C after extraction. For goal (3), a portion of the entire ice core will be returned to the U.S. for microbial analyses, measurements of a range of elements and chemical species using a well-established, NSF-funded continuous ice core analytical system, and continuous carbon monoxide and methane measurements to complement the field measurements. Microbiological analysis will be conducted on ice samples characterized by high and low in situ gas anomalies to determine what microbes are present that may be responsible for creating the observed gas artifacts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.