Absolutely dated, annually resolved, wood samples provided through WP1 will provide the sample material for our isotopic analyses. Since the relative composition of wholewood is variable a-cellulose will be prepared from the wholewood. At present a variety of techniques are currently in use by stable isotope laboratories across Europe. The different procedures will therefore be adapted and harmonised accordingly. This will be achieved by introducing the technicians in charge of the preparations to the appropriate chemical procedures. In preparing pure a-cellulose the wood is broken down such that the resulting material is completely homogeneous.

Stable carbon and oxygen isotope analysis will be performed on the pure homogeneous a-cellulose at the partner laboratories using well established stable isotope mass spectrometry methods. Work is allocated according to the expertise and analytical capabilities of the individual institutions. Stable hydrogen isotope analyses will be performed on the nitrated cellulose. This additional processing is essential in order to exclude the influence of post-synthesic exchangeable hydrogen atoms. As a consequence of this and available analytical capability for analysis of this isotope, studies will initially be restricted to a continuous period  from AD1901-AD2000. This period is of interest to climatologists as it includes not only the recent period of anthropogenic warming but also several shifts in the phase of the North Atlantic Oscillation. Additional target sampling will also supplement this sequence based upon the presence of isotopic “pointer years” in the C & O isotope series. To ensure that all laboratories are standardised in their reporting of their isotope data regular inter-laboratory comparisons and the sustained analysis of multiple reference materials will ensure parity and analytical stability between the laboratories.

As a direct consequence of the rate limiting nature of preparative and analytical processes required for stable (hydrogen) isotope analysis Partners APU & UNIBE will also investigate the refinement of batch processing methods for cellulose (nitrate) preparation and the development of a fast hydrogen isotope preparation procedure.

In total over 18,300 isotope measurements will be performed on the network samples in order to provide the necessary coverage and replication for this study. Additional d¹⁸O and dD from water samples taken at tree sites far from GNIP stations will be analysed. The results will feed into WP4 (Model development & Evaluation) which will use these data in conjunction with novel transfer functions and mechanistic models to reconstruct spatial variability in stable (C,H,O) isotopes and associated climatic parameters.