Intra-annual oxygen isotope variations in Central Indian teak cellulose: possibility of improved resolution for past monsoon reconstruction

Abstract

A clear seasonal cycle has been detected in the intraannual oxygen isotope variations (δ¹⁸O) of cellulose from several annual growth rings of teak trees that grew in central India. This persistent cycle is marked by higher δ¹⁸O values at the ring boundaries and lower δ¹⁸O values at intermediate parts. The amplitude of this seasonal cycle varies up to 6.8‰. Based on the pattern of teak growth reported in the literature and a plant physiological model that interprets the δ¹⁸O of plant cellulose, it seems possible to identify subsections of a ring that formed during pre-monsoon, peak-monsoon and post-monsoon. Comparison of the δ¹⁸O profile of a ring (year AD 1971), analysed with the highest resolution, and a model profile based on concurrent local meteorological data indicates the possibility of achieving a ~20 day resolution in monsoon reconstruction by intra-annual δ¹⁸O measurements.