Reconstructions of the 14С cosmogenic isotope content from natural archives after the last glacial termination

Abstract

Data on the content of the ¹⁴C cosmogenic isotope in tree rings, which were obtained as a result of laboratory measurements, are often used when solar activity (SA) is reconstructed for previous epochs, in which direct observations are absent. However, these data contain information not only about SA variations but also about changes in the Earth climatic parameters, such as the global temperature and the CO₂ content in the Earth’s atmosphere. The effect of these variations on the ¹⁴C isotope content in different natural reservoirs after the last glacial termination to the middle of the Holocene is considered. The global temperature and the CO₂ content increased on this time interval. In this case the ¹⁴C absolute content in the atmosphere increased on this time interval, even though the ¹⁴С to ¹²С isotope concentration ratio (as described by the Δ¹⁴С parameter) decreased. These variations in the radiocarbon absolute content can be caused by its redistribution between natural reservoirs. It has been indicated that such a redistribution is possible only when the rate of carbon exchange between the ocean and atmosphere depends on temperature. The values of the corresponding temperature coefficient for the 17–10 ka BC time interval, which make it possible to describe the carbon redistribution between the ocean and atmosphere, have been obtained.