9321623 Sowers This award is for support to continue research on the concentration of methane, the isotopic composition and concentration of oxygen, nitrogen, argon, and total gas content of samples from the Greenland Ice Sheet Project Two (GISP2) ice core. The methane concentration of air is a proxy for the extent of wetlands and the warm, wet climates they signify. Methane is also a radiatively active gas which affects climate. The isotopic composition of oxygen in air reflects relative rates of primary production in the terrestrial and marine environments, and humidity in productive continental areas. Methane and the isotopic composition of oxygen are also constant (or nearly so) throughout the atmosphere at any one time. They therefore serve as time stratigraphic markers for correlating Greenland and Antarctic ice cores. Nitrogen and Argon isotopes indicate the extent of gravitational fractionation during the trapping process and allow for correction of the measured concentrations and isotopic compositions of these gases. Total gas content reflects paleoelevation of ice sheets among other poorly understood influences. This work will provide information on climate and biogeochemistry during the last approximately 250,000 years of Earth history. ***
