Rapid atmospheric CO_2 changes associated with the 8,200-years-B.P. cooling event

摘要

By applying the inverse relation between numbers of leaf stomata and atmospheric CO_2 concentration, stomatal frequency analysis of fossil birch leaves from lake deposits in Denmark reveals a century-scale CO_2 change during the prominent Holocene cooling event that occurred in the North Atlantic region between 8,400 and 8,100 years B.P. In contrast to conventional CO_2 reconstructions based on ice cores from Antarctica, quantification of the stomatal frequency signal corroborates a distinctive temperature-CO_2 correlation. Results indicate a global CO_2 decline of ≈25 ppm by volume over ≈300 years. This reduction is in harmony with observed and modeled lowering of North Atlantic sea-surface temperatures associated with a short-term weakening of thermohaline circulation.