Glacial-interglacial excursion in the concentration of atmospheric CO₂: effect in the ¹³C/¹²C ratio in wood cellulose

Abstract

Stable carbon isotope ratios (¹³C/¹²C) of cellulose extracted from wood belonging to the last glacial-maximum period (20 ± 2k yr) is on the average 4‰ higher than that for the corresponding ratios from the recent interglacial age, and could not be the result of any changes in humidity or temperature alone. This temporal variation of δ13C in wood cellulose corresponds chronologically to the reduced concentration of atmospheric CO₂ measured in glacial ice cores, thus providing the first direct evidence of the effect of reduced atmospheric CO₂ concentration on land biota. The higher δ13C in wood cellulose and the manner in which it varies with time could be explained if, in addition to causes introduced by a changing ocean chemistry during glacial time, there is an additional carbon reservoir created by vegetation flourishing in the newly exposed land surfaces accompanying a lowering of the sea level.