Atmospheric CO2 during the 13th century AD: reconciliation of data from ice core measurements and stomatal frequency analysis

Authors

  • THOMAS B. Van HOOF,

    Corresponding author
    1. Department of Palaeoecology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 14, 3584 CD Utrecht, The Netherlands
      *Corresponding author.
      e-mail: T.B.vanHoof@bio.uu.nl
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  • KARSTEN A. KASPERS,

    1. Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
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  • FRIEDERIKE WAGNER,

    1. Department of Palaeoecology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 14, 3584 CD Utrecht, The Netherlands
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  • RODERIK S. W. Van De WAL,

    1. Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
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  • WOLFRAM M. KÜRSCHNER,

    1. Department of Palaeoecology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 14, 3584 CD Utrecht, The Netherlands
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  • HENK VISSCHER

    1. Department of Palaeoecology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 14, 3584 CD Utrecht, The Netherlands
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*Corresponding author.
e-mail: T.B.vanHoof@bio.uu.nl

ABSTRACT

Atmospheric CO2 reconstructions are currently available from direct measurements of air enclosures in Antarctic ice and, alternatively, from stomatal frequency analysis performed on fossil leaves. A period where both methods consistently provide evidence for natural CO2 changes is during the 13th century ad. The results of the two independent methods differ significantly in the amplitude of the estimated CO2 changes (10 ppmv ice versus 34 ppmv stomatal frequency). Here, we compare the stomatal frequency and ice core results by using a firn diffusion model in order to assess the potential influence of smoothing during enclosure on the temporal resolution as well as the amplitude of the CO2 changes. The seemingly large discrepancies between the amplitudes estimated by the contrasting methods diminish when the raw stomatal data are smoothed in an analogous way to the natural smoothing which occurs in the firn.

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