IN-SITU COSMOGENIC 14C IN ICE AND IMPLICATIONS FOR ICE PROCESSES

Polar ice contains two varieties of carbon-14 resulting from both the 14C trapped in atmospheric air and 14C which is produced by the effects of cosmic rays on the ice. This cosmogenic 14C is production in the upper ~1m of the ice. In-situ-produced 14C has been studied in both accumulating and ablating ice regions. The concentration of in-situ 14C in ice is expected to be inversely proportional to the accumulation rate and directly proportional to the production rate. At GISP-2 and ablating regions, the amounts of in-situ 14C are broadly understandable in these terms. At some Antarctic accumulation sites, the amounts of 14C appear to be influenced by more complex processes. We will report on some studies of in-situ-produced 14C in polar ices cores from various locations and their implications for our understanding of the ice.

These studies would be impossible without the low-level detection capabilities of accelerator mass spectrometry. This paper is dedicated to John Andrews' early interest in the use of AMS for his research, he was an early user of the Arizona AMS Lab and has remained one of its most loyal supporters.