Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

摘要

Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remotedome summits in Antarctica, were volcanically synchronized to improve ourunderstanding of their chronologies. Within the past 216 kyr, 1401 volcanictie points have been identified. DFO2006 is the chronology for the DF corethat strictly follows O₂ / N₂ age constraints with interpolationusing an ice flow model. AICC2012 is the chronology for five cores, includingthe EDC core, and is characterized by glaciological approaches combining iceflow modelling with various age markers. A precise comparison between thetwo chronologies was performed. The age differences between them are within2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older thanAICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5dand MIS 5b, respectively. Accordingly, the ratios of duration(AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. Whenmaking a comparison with accurately dated speleothem records, the age ofDFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well atMIS 5b, supporting their accuracy at these stages. In addition, we found thatglaciological approaches tend to give chronologies with younger ages andwith longer durations than age markers suggest at MIS 5d–6. Therefore, wehypothesize that the causes of the DFO2006–AICC2012 age differences at MIS 5are (i) overestimation in surface mass balance at around MIS 5d–6 in theglaciological approach and (ii) an error in one of the O₂ / N₂ ageconstraints by ~ 3 kyr at MIS 5b. Overall, we improved ourknowledge of the timing and duration of climatic stages at MIS 5. This newunderstanding will be incorporated into the production of the next commonage scale. Additionally, we found that the deuterium signals of ice, δD_ice, at DF tends to lead the one at EDC, with the DF lead being morepronounced during cold periods. The lead of DF is by +710 years (maximum)at MIS 5d, ?230 years (minimum) at MIS 7a and +60 to +126 years on average.