USAP-DC

This project will develop methods to measure the ratios of carbon-13 to carbon-12, and heavy to light hydrogen in methane in air trapped in ice cores. The ratios of the different forms of carbon and hydrogen are "fingerprints" of different sources of this gas in the past--for example wetlands in the tropics versus methane frozen in the sea floor. Once the analysis method is developed, the measurements will be used to examine why methane changed abruptly in the past, both during the last ice age, and during previous warm periods. The data will be used to understand how methane sources like wildfires, methane hydrates, and wetlands respond to climate change. This information is needed to understand future risks of large changes in methane in the atmosphere as Earth warms.

The project involves two tasks. First, the investigators will build and test a gas extraction system for methane isotopic measurements using continuous flow methods, with the goal of equaling or bettering the precision attained by the few other laboratories that make these measurements. The system will be interfaced with existing mass spectrometers at Oregon State University. The system consists of a vacuum chamber and sequence of traps, purification columns, and furnaces that separate methane from other gases and convert it to carbon dioxide or hydrogen for mass spectrometry. Second, the team will measure the isotopic composition of methane across large changes in concentration associated with two past interglacial periods and during abrupt methane changes of the last ice age. These measurements will be used to understand if the main reason for these concentration changes is climate-driven changes in emissions from wetlands, or whether other sources are involved, for example methane hydrates or wildfires.

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.

Person	Role
Brook, Edward	Investigator and contact
Riddell-Young, Benjamin	Researcher

Antarctic Glaciology

Award # 1745078

USAP-1745078_1

None in the Database

Repository	Title (link)	Format(s)	Status
USAP-DC	Carbon-13 isotopic composition of atmospheric methane across Heinrich Stadials 1 and 5, and Dansgaard Oesgher Event 12, WAIS Divide Ice Core, Antarctica	Excel	exists
USAP-DC	Atmospheric methane across the Last Glacial Maximum and deglaciation from the GISP2, NEEM and WAIS Divide ice cores	Excel	deprecated
USAP-DC	Atmospheric methane interpolar difference and four-box troposphere model output across the Last Glacial Maximum and Deglaciation	CSV	exists
USAP-DC	Atmospheric methane across the Last Glacial Maximum and deglaciation from the GISP2, NEEM and WAIS Divide ice cores	CSV	exists

1. Riddell-Young, B., Rosen, J., Brook, E., Buizert, C., Martin, K., Lee, J., Edwards, J., Mühl, M., Schmitt, J., Fischer, H., & Blunier, T. (2023). Atmospheric methane variability through the Last Glacial Maximum and deglaciation mainly controlled by tropical sources. Nature Geoscience, 16(12), 1174–1180. (doi:10.1038/s41561-023-01332-x)