Articles | Volume 10, issue 12
Geosci. Model Dev., 10, 4665–4691, 2017
Geosci. Model Dev., 10, 4665–4691, 2017

Model description paper 22 Dec 2017

Model description paper | 22 Dec 2017

HIMMELI v1.0: HelsinkI Model of MEthane buiLd-up and emIssion for peatlands

Maarit Raivonen1, Sampo Smolander1,2, Leif Backman3, Jouni Susiluoto3,4, Tuula Aalto3, Tiina Markkanen3, Jarmo Mäkelä3, Janne Rinne5, Olli Peltola1, Mika Aurela3, Annalea Lohila3, Marin Tomasic1, Xuefei Li1, Tuula Larmola6, Sari Juutinen7, Eeva-Stiina Tuittila8, Martin Heimann1,9, Sanna Sevanto10, Thomas Kleinen11, Victor Brovkin11, and Timo Vesala1,12 Maarit Raivonen et al.
  • 1Division of Atmospheric Sciences, Department of Physics, University of Helsinki, P.O. Box 68, 00014 Helsinki, Finland
  • 2Princeton Environmental Institute, Guyot Hall, Princeton University, Princeton, NJ 08544, USA
  • 3Climate research, Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland
  • 4Lappeenranta University of Technology, School of Science, 53850 Lappeenranta, Finland
  • 5Department of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 22362 Lund, Sweden
  • 6Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki, Finland
  • 7Department of Environmental Sciences, University of Helsinki, Viikinkaari 1, 00790 Helsinki, Finland
  • 8School of Forest Sciences, University of Eastern Finland, P.O. Box 111, 80770 Joensuu, Finland
  • 9Max Planck Institute for Biogeochemistry, 07745 Jena, Germany
  • 10Earth and Environmental Sciences Division, Los Alamos National Laboratory, Bikini Atoll Rd. MS J535, Los Alamos, NM 87545, USA
  • 11Max Planck Institute for Meteorology, Bundesstr, 53, 20146, Hamburg, Germany
  • 12Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 Helsinki, Finland

Abstract. Wetlands are one of the most significant natural sources of methane (CH4) to the atmosphere. They emit CH4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH4, in addition to carbon dioxide (CO2). Production of CH4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH4 emissions are thus needed for upscaling observations to estimate present CH4 emissions and for producing scenarios of future atmospheric CH4 concentrations. Aiming at a CH4 model that can be added to models describing peatland carbon cycling, we composed a model called HIMMELI that describes CH4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peatland vegetation, and water table depth (WTD), it simulates the concentrations and transport of CH4, CO2, and oxygen (O2) in a layered one-dimensional peat column. Here, we present the HIMMELI model structure and results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and demonstrate that HIMMELI outputs realistic fluxes by comparing modeled and measured fluxes at two peatland sites. As HIMMELI describes only the CH4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that (1) the model is flexible and robust and thus suitable for different environments; (2) the simulated CH4 emissions largely depend on the prescribed rate of anoxic respiration; (3) the sensitivity of the total CH4 emission to other input variables is mainly mediated via the concentrations of dissolved gases, in particular, the O2 concentrations that affect the CH4 production and oxidation rates; (4) with given input respiration, the peat column description does not significantly affect the simulated CH4 emissions in this model version.

Short summary
Wetlands are one of the most significant natural sources of the strong greenhouse gas methane. We developed a model that can be used within a larger wetland carbon model to simulate the methane emissions. In this study, we present the model and results of its testing. We found that the model works well with different settings and that the results depend primarily on the rate of input anoxic soil respiration and also on factors that affect the simulated oxygen concentrations in the wetland soil.