Reconstruction of glacial/interglacial changes in the global carbon cycle from CO2 and d13 CO2 in Antarctic ice cores (scientific paper)

摘要

High-resolution CO2 and δ13CO2 records from the Taylor Dome ice core, Antarctica, reveal significant changes in the global carbon cycle over the last 30,000 yrs. CO2 concentrations increase from 180 ppmv at 20 kyr before present to 275 ppmv at the start of the Holocene with an intermittent decline during the Antarctic Cold Reversal. δ13C shows a net increase from the average glacial level of -6.7‰ to mean Holocene values of around -6.5‰. However, the transition period is initiated by an 0.5‰ drop at 20 kyr before present followed by an 0.7 ‰ increase which is interrupted by an 0.2‰ decline during the Antarctic Cold Reversal. Isotope budget considerations show that during the Holocene and the Last Glacial Maximum changes in the size of terrestrial biosphere can account for the observed changes in CO2 and δ13C. In contrast changes in the atmosphere/ocean system are dominant during termination I. The size of the CO2 increase cannot be explained by variations in ocean temperature, salinity or net transfer of carbon into the terrestrial biosphere alone. The strong temporal correlation of CO2 and Antarctic isotope temperatures is in conflict with hypotheses to account for the missing CO2 which are connected to sea level change or a dust induced change in the biological productivity in the Southern Ocean. Changes in the Southern Ocean sea ice cover, however, may provide a direct link to temperature which appears to be able to account for the observed changes in atmospheric CO2 and δ13C.