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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2020-110
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-110
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 26 Apr 2020

Submitted as: research article | 26 Apr 2020

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This preprint is currently under review for the journal BG.

Peatland area and carbon over the past 21 000 years – a global process based model investigation

Jurek Müller1,2 and Fortunat Joos1,2 Jurek Müller and Fortunat Joos
  • 1Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
  • 2Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland

Abstract. Peatlands are an essential part of the terrestrial carbon cycle and the climate system. Understanding their history is key to understand future and past land-atmosphere carbon fluxes. We performed transient simulations over the past 22 000 years with a dynamic global peat and vegetation model forced by Earth System Model climate output, thereby complementing data-based reconstructions for peatlands. Our novel results demonstrate a highly dynamic evolution with concomitant gains and losses of active peatland areas. Modelled gross area changes exceed net changes several fold, while net peat area increases by 60 % over the deglaciation. Peatlands expand to higher northern latitudes in response to warmer and wetter conditions and retreating ice sheets and are partly lost in mid-latitude regions. In the tropics peatlands are partly lost due to flooding of continental shelves and regained by non-linear interactions between temperature, precipitation and CO2. Large north-south shifts of tropical peatlands are driven by shifts in the position of the Inter Tropical Convergence Zone associated with the abrupt climate events of the glacial termination. Time slice simulations for the Last Glacial Maximum (LGM) demonstrate large uncertainties in modelled peatland extent (global range: 1.5 to 3.4 Mkm2) stemming from uncertainties in climate forcing. Net uptake of atmospheric CO2 through peatlands, modelled at 350 GtC since the LGM, includes decay from former peatlands. Carbon uptake would be misestimated, in particular during periods of rapid climate change and subsequent peatland area shifts, when considering only changes in the area of currently active peatlands. Our study highlights the dynamic nature of peatland distribution and calls for an improved understanding of former peatlands to better constrain peat carbon sources and sinks.

Jurek Müller and Fortunat Joos

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Jurek Müller and Fortunat Joos

Jurek Müller and Fortunat Joos

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Latest update: 03 Jun 2020
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Short summary
We present an in depth model analysis of transient peatland area and carbon dynamics over the last 22 000 years. Our novel results show that the consideration of both gross positive and negative area changes are necessary to understand the transient evolution of peatlands and their net effect on atmospheric carbon. The study includes the attributions to drivers through factorial simulations, assessments of uncertainty from climate forcing, and determination of the global net carbon balance.
We present an in depth model analysis of transient peatland area and carbon dynamics over the...
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