Possibility of Climatically Induced Variations in the 14C and 13C Enrichment Patterns as Recorded by a 300-Year-Old Norwegian Pine

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Abstract
The secular patterns of Δ and δ13C measured in wood cellulose are compared with a palaeotemperature index published for the immediate growth region. 14C enrichment shows an overall decrease of ca 20% (Δ) during the 18th and 19th centuries with shorter term (decade) variations superimposed on the general trend. Measured Δ values correlate significantly with the average mean summer temperatures and indicate a linear coefficient of ca − 10.2% °C–1. Short-term variations in the natural concentration of 14C which are closely related to climatic change may reflect the latitudinal dependence for atmospheric mixing.The secular trend in δ13C covers a range of 2% but variations of this magnitude reflect influences other than those directly associated with climatic change, eg, possible assimilation of recycled biospheric CO2 during early life and post AD 1850 anthropogenic effects. No evidence was found to suggest a significant correlation between δ13C and the mean atmospheric temperature during summer growth periods.