Anglia Ruskin Research Online (ARRO)
Browse

File(s) not publicly available

Correction of tree ring stable carbon isotope chronologies for changes in the carbon dioxide content of the atmosphere

journal contribution
posted on 2023-07-26, 13:26 authored by Danny McCarroll, Mary H. Gagen, Neil J. Loader, Iain Robertson, Kevin J. Anchukaitis, Sietse Los, Giles H. F. Young, Risto Jalkanen, Andreas Kirchhefer, John S. Waterhouse
Tree-ring stable carbon isotope ratios (δ13C) often display a decline over the industrial period (post-AD1850) that is only partly explained by changes in the isotopic ratio of carbon dioxide (CO2) and may represent a response to increased atmospheric concentrations of CO2 (ca). If this is not addressed, reconstructions using long tree-ring stable isotope chronologies calibrated using the modern period, for which meteorological records are available, may be compromised. We propose a correction procedure that attempts to calculate the δ13C values that would have been obtained under pre-industrial conditions. The correction procedure uses nonlinear (loess) regression but the magnitude of the adjustment made is restricted by two logical constraints based on the physiological response of trees: first, that a unit increase in ca cannot result in more than the same unit increase in the internal concentration of CO2 (ci), and second, that increases in water-use efficiency as a result of an increase in ca are limited to maintaining a constant ci/ca ratio. The first constraint allows retention of a falling trend in δ13C, which exceeds that which could logically be attributed to a passive response to rising ca. The second constraint ensures that any increase in δ13C, reflecting a change in water-use efficiency beyond maintenance of a constant ci/ca, is not removed. The procedure is tested using ‘pseudoproxies’, to demonstrate the effect of the correction on time-series with different shapes, and data from three sites in Finland and Norway. Two of the time-series retain a significant trend after correction, and in all three cases the correction improves the correlation with local meteorological measurements.

History

Refereed

  • Yes

Volume

73

Issue number

6

Page range

1539-1547

Publication title

Geochimica et Cosmochimica Acta

ISSN

0016-7037

Publisher

Elsevier

Language

  • other

Legacy posted date

2013-09-16

Legacy Faculty/School/Department

ARCHIVED Faculty of Science & Technology (until September 2018)

Usage metrics

    ARU Outputs

    Categories

    No categories selected

    Keywords

    Licence

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC