Sub-millennial atmospheric CO2 variations at around Antarctic warming event 1

How atmospheric CO2 varies and is controlled on various time scales is an important question for understanding how the carbon cycle and climate change are linked. Past CO2 variations on orbital to millennial timescales are relatively well studied, but variations on decadal to centennial timescales are not. Here we show preliminary submillennial-scale CO2 variations from the Siple Dome, Antarctica ice core. So far we analyzed 40 samples from 37.3-40.5 ka (on GISP2 time scale). The average time resolution is 80 years, but with a better resolution at some rapid changes of CO2. The time interval is of great interest because it covers or partly includes Antarctic warming event 1, Dansgaard-Oeschger event 8 (DO-8) and Heinrich event 4 (H-4). In general, the Siple Dome high-resolution records confirm the previous millennial records from Taylor Dome and Byrd ice cores. A striking feature of the Siple Dome record is rapid CO2 changes of 5-18 ppm in decades or a century, compared to 20-40 ppm variations on millennial timescales. One of the CO2 jumps occurred at the time of the abrupt warming in Greenland associated with DO-8 event. The true CO2 change rate could have been larger because our data resolution is similar to time intervals of the abrupt changes, and gas exchange before bubble close-off and gas diffusion in ice after bubble close-off smooth the rapid changes. Precise comparison of CO2 and the timing of H-4 is difficult due to chronological uncertainties. We will continue the CO2 analysis for the Siple Dome ice core and the updated results will be presented at the meeting.