Workpackage 4: Model Development, Evaluation & Application


Workpackage Leader:

N.N.


Objectives:

To develop models using annually and interannually resolved stable isotope time series to reconstruct past spatio-temporal climatic variability across Europe during the last 400 years.

To use field data and high-resolution isotope analyses to elucidate the inter- and intra-annual (seasonal) signal contained within tree-rings of deciduous oak and evergreen pine.

To provide novel non-linear transfer functions and trained mechanistic models linking isotopic information from tree-rings with IAEA-GNIP & instrumental meteorological records for climate reconstruction.

The development of a digital map array and website displaying the ISONET data electronically and sequentially to demonstrate trends in climate variability, extreme events and isotopic trends.


Methodology / work description:

In addition to conventional statistical analysis of the isotopic time series and application of spectral analytical methods the tree-ring isotope ratios will be fully explored using a variety of newly developed & novel applications. Using a chain of transfer functions, the nature of isotopic discrimination starting with climate/isotope input data and leading from leaf via intermediate steps to its final fixation in tree-ring cellulose will be applied. Since the question to be answered is not the calculation of an output (isotope) ratio for given (climate) input variable, but the calculation of climatic (output) information from set of (input) isotope ratios, the problems of inverse modeling and the potential multiple outcomes of transfer function chains must be addressed.

Initially, models leading from source/environmental inputs to the sink (isotope ratios) will be adapted or newly established for the target species. The isotopic composition of cellulose depends principally on four processes; the isotopic composition of the source materials, discrimination during photsynthesis, nonuniform growth/allocation within the organism and post photosynthetic modification. Of these processes all but the last are to a certain extent understood (yet require additional attention through this project), whilst the last must be tackled empirically [eg. 36].

In light of the complexity of the mechanisms under study, Model development will proceed simultaneously along two strands. Initially, parameterised readily available process models for stand carbon balance, isotopic discrimination and wood accumulation (ie:SICA/SIMFORG) will be fine-tuned using the experimental results from WP1-3. A second, statistical description of the weather/isotope relations within the intervals identified which extends beyond the commonly used linear multivariate approaches and tackles robustly nonlinear relationships will also be applied. Both will be thoroughly evaluated to yield quantitative estimates of climatic variables.

The resulting data will also be exploited fully by all partners using conventional methods to investigate trends, extremes and significant or persistant periodicities in the individual and composite data series and the results published in high impact scientific journals. These data will also be displayed digitally as a series of time slices to demonstrate trends in the absolute, temporal and spatial variability of these sequences and once sequentially animated through the project website will provide an accessible, easily communicable, concise and engaging demonstration of our scientific achievements.