Stomatal evidence for a decline in atmospheric CO2 concentration during the Younger Dryas stadial: a comparison with Antarctic ice core records

A recent high‐resolution record of Late‐glacial CO₂ change from Dome Concordia in Antarctica reveals a trend of increasing CO₂ across the Younger Dryas stadial (GS‐1). These results are in good agreement with previous Antarctic ice‐core records. However, they contrast markedly with a proxy CO₂ record based on the stomatal approach to CO₂ reconstruction, which records a ca. 70 ppm mean CO₂ decline at the onset of GS‐1. To address these apparent discrepancies we tested the validity of the stomatal‐based CO₂ reconstructions from Kråkenes by obtaining further proxy CO₂ records based on a similar approach using fossil leaves from two independent lakes in Atlantic Canada. Our Late‐glacial CO₂ reconstructions reveal an abrupt ca. 77 ppm decrease in atmospheric CO₂ at the onset of the Younger Dryas stadial, which lagged climatic cooling by ca. 130 yr. Furthermore, the trends recorded in the most accurate high‐resolution ice‐core record of CO₂, from Dome Concordia, can be reproduced from our stomatal‐based CO₂ records, when time‐averaged by the mean age distribution of air contained within Dome Concordia ice (200 to 550 yr). If correct, our results indicate an abrupt drawdown of atmospheric CO₂ within two centuries at the onset of GS‐1, suggesting that some re‐evaluation of the behaviour of atmospheric CO₂ sinks and sources during times of rapid climatic change, such as the Late‐glacial, may be required. Copyright © 2002 John Wiley & Sons, Ltd.