Atmospheric CO2 variations on millennial time scales during the early Holocene

Abstract

The objective of this study is to decipher the relationship between climate and carbon cycles on millennial time scales during the early Holocene. The early Holocene (11.7–7.0 ka) is a climatically dynamic period on millennial timescales as seen in paleoproxy records for ice sheet collapse (Bond Cycle) in the North Atlantic, sea ice extent variations in the Southern Ocean, and El Niño–like and La Niña–like variation in the eastern equatorial Pacific. We may expect atmospheric CO2 concentration change during the early Holocene because CO2 is controlled by physical and biological processes in ocean and land. However, existing CO2 records from EPICA Dome C and Taylor Dome ice cores do not address the issue due to lack of sufficient temporal resolution and chronology. In this study, a new Siple Dome CO2 record for the time period of 9.0-11.7 ka is obtained. Combined with an existing Siple Dome CO2 record for 7.3-9.0 ka, a high-resolution CO2 record for the early Holocene (7.3-11.7 ka) is constructed. The sampling resolution is better than 30 years for 11.7–7.3 ka. The Siple Dome CO2 data show a decrease of CO2 of ~10 ppm from 10.9 to 7.3 ka and multi-centennial to millennial variability of 2-6 ppm with local minima at 11.1, 10.1, 9.0 and 8.3 ka. The millennial-scale CO2 variation correlates with paleoclimate records and show that atmospheric CO2 change was in harmony with global climate change. Possible control mechanisms for CO2 variations are discussed.