Understanding the production and retention of in situ cosmogenic 14C in polar firn

Wednesday, 17 December 2014
Benjamin Hmiel1, Vasilii V Petrenko1, Andrew Smith2, Christo Buizert3, Christina M Harth4, Ross Beaudette4, Philip Place Jr1, Quan Hua2, Bin Yang2, Isaac Vimont5, Ray F Weiss4, Jeffrey P Severinghaus4, Edward Brook3 and James W C White5, (1)University of Rochester, Department of Earth and Environmental Sciences, Rochester, NY, United States, (2)Australian Nuclear Science and Technology Organisation (ANSTO), Kirrawee DC, NSW, Australia, (3)Oregon State University, College of Earth, Ocean and Atmospheric Sciences, Corvallis, OR, United States, (4)University of California San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States, (5)Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, United States
Radiocarbon in CO2, CO and CH4 trapped in polar ice is of interest for dating of ice cores, studies of past solar activity and cosmic ray flux, as well as studies of the paleoatmospheric CH4 budget. The major difficulty with interpreting 14C measurements in ice cores stems from the fact that the measured 14C represents a combination of trapped paleoatmospheric 14C and 14C that is cosmogenically produced within the ice matrix. This in situ cosmogenic 14C component in ice is at present poorly understood. Prior ice core 14C studies show conflicting results with regard to the retention of cosmogenic 14C in polar firn and partitioning of this 14C among CO2, CO and CH4. Our new study aims to comprehensively characterize the 14C of CO2, CO, and CH4 in both the air and the ice matrix throughout the firn column at Summit, Greenland. We will present new measurements of 14C in Summit firn air (the first phase of this study) and discuss the implications for in situ cosmogenic 14C production and retention.