Tightened constraints on the time-lag between Antarctic temperature and CO2 during the last deglaciation

Antarctic ice cores provide clear evidence of a close coupling between variations in Antarctic temperature and the atmospheric concentration of CO₂ during the glacial/interglacial cycles of at least the past 800-thousand years. Precise information on the relative timing of the temperature and CO₂ changes can assist in refining our understanding of the physical processes involved in this coupling. Here, we focus on the last deglaciation, 19 000 to 11 000 yr before present, during which CO₂ concentrations increased by ~80 parts per million by volume and Antarctic temperature increased by ~10 Celsius degree. Utilising a recently developed proxy for regional Antarctic temperature, derived from five near-coastal ice cores and two ice core CO₂ records with high dating precision, we show that the increase in CO₂ likely lagged the increase in regional Antarctic temperature by less than 400 yr and that even a short lead of CO₂ over temperature cannot be excluded. This result, consistent for both CO₂ records, implies a faster coupling between temperature and CO₂ than previous estimates, which had permitted up to millennial-scale lags.