HIGH-RESOLUTION HOLOCENE AND LATE-GLACIAL ATMOSPHERIC CO2 RECORD - VARIABILITY TIED TO CHANGES IN THERMOHALINE CIRCULATION

Here we present results from a new method for detecting changes in atmospheric CO2 based on delta(13)C analyses of selected peat components from a peat core in southern South America. The paleo-CO2-record has decadal resolution spanning the last 14,000 radiocarbon years and compares well with Antarctic ice core CO2 data Sharp peaks in CO2 are detected during the late glacial, specifically at 10,200, 11,600 and 12,900 yeats B.P. When compared to two deep-sea records interpreted to reflect changes in thermohaline circulation, these CO2 pulses appear to relate to degassing events of the ocean associated with reinitiation of the thermohaline circulation occurring at this time. Concomitant decreases in atmospheric Delta(14)C during the late glacial are also consistent with a deep oceanic carbon source for the large atmospheric pulses in CO2. Results from a simple three-box model indicate that the magnitude of the CO2 released during these degassing events is compatible with our observations. The rate of degassing, however, is much slower than that observed in the paleo-CO2-record. Two broad Holocene CO2 excursions are also identified with peaks at 4,200 and 7,700 years B.P. The driving mechanism behind these excursions appear to be different than those in the late glacial.