Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/cp-2017-92
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
17 Jul 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Climate of the Past (CP).
Novel approach for ice core based temperature reconstructions – a synthetic data study for Holocene δ15N data
Michael Döring1,2 and Markus Leuenberger1,2 1Climate and Environmental Physics, University of Bern, Switzerland
2Oeschger Centre for Climate Change Research (OCCR), Bern, Switzerland
Abstract. We present a novel approach for reconstructing the Holocene surface temperature histories by forcing the output of a firn densification and heat diffusion model to fit nitrogen isotope data (δ15N) extracted from ancient air in Greenland ice cores. The performance of this novel approach is demonstrated using synthetic data. The presented approach works completely automated and leads to a match of the δ15N target data in the low permeg level and to related temperature deviations of a few tenths of Kelvin for different data scenarios, showing the robustness of the reconstruction method. The obtained, final mismatches follow a symmetric, standard distribution function. 95% of the mismatches compared to the synthetic target data are in an envelope in between 3.0-6.3 permeg for δ15N and 0.23-0.51 K for temperature (2σ, respectively). We solve the inverse problem T(δ15N) by using a combination of Monte Carlo sampling and quantitative data analysis, based on cubic spline filtering of random numbers and the measured temperature sensitivity for nitrogen isotopes. Additionally, the presented reconstruction approach was tested by fitting δ40Ar and δ15Nexcess data (Döring et al., in prep.), which leads to same robust agreement between modelled and measurement data. In addition to Holocene temperature reconstructions, the fitting approach can also be used for glacial temperature reconstructions (Döring et al., in prep.) and it is reasonable to adapt the approach for model inversions of other non-linear physical processes.

Citation: Döring, M. and Leuenberger, M.: Novel approach for ice core based temperature reconstructions – a synthetic data study for Holocene δ15N data, Clim. Past Discuss., https://doi.org/10.5194/cp-2017-92, in review, 2017.
Michael Döring and Markus Leuenberger
Michael Döring and Markus Leuenberger
Michael Döring and Markus Leuenberger

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Short summary
We present a novel approach for ice core based temperature reconstructions, which is based on nitrogen isotope data measured on enclosed air bubbles in ice cores. The processes of air movement and enclosure are highly temperature dependent due to heat diffusion in and densification of the snow and ice. Our method inverts a model, which describes these processes, to desired temperature histories. This paper examines the performance of our approach on different synthetic isotope data scenarios.
We present a novel approach for ice core based temperature reconstructions, which is based on...
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