Abstract:
We report a decadally resolved record of atmospheric CO₂ concentration for the last 1000 years, obtained from the West Antarctic Ice Sheet (WAIS) Divide shallow ice core. The most prominent feature of the pre-industrial period is a rapid ∼7 ppm decrease of CO₂ in a span of ∼20–50 years at ∼1600 A.D. This observation confirms the timing of an abrupt atmospheric CO₂ decrease of ∼10 ppm observed for that time period in the Law Dome ice core CO₂ records, but the true magnitude of the decrease remains unclear. Atmospheric CO₂ variations over the time period 1000–1800 A.D. are statistically correlated with northern hemispheric climate and tropical Indo-Pacific sea surface temperature. However, the exact relationship between CO₂ and climate remains elusive due to regional climate variations and/or uneven geographical data density of paleoclimate records. We observe small differences of 0 ∼ 2% (0 ∼ 6 ppm) among the high-precision CO₂ records from the Law Dome, EPICA Dronning Maud Land and WAIS Divide Antarctic ice cores. However, those records share common trends of CO₂ change on centennial to multicentennial time scales, and clearly show that atmospheric CO₂ has been increasing above preindustrial levels since ∼1850 A.D.
