Preprints
https://doi.org/10.5194/bg-2022-240
https://doi.org/10.5194/bg-2022-240
 
13 Jan 2023
13 Jan 2023
Status: this preprint is currently under review for the journal BG.

Simulated methane emissions from Arctic ponds are highly sensitive to warming

Zoé Rehder1,2, Thomas Kleinen1, Lars Kutzbach3,4, Victor Stepanenko5,6,7, Moritz Langer8,9, and Victor Brovkin1,4 Zoé Rehder et al.
  • 1Department of the Ocean in the Earth System, Max-Planck-Institute for Meteorology, Hamburg, Germany
  • 2International Max Planck Research School on Earth System Modeling, Hamburg, Germany
  • 3Institute of Soil Science, Universität Hamburg, Hamburg, Germany
  • 4Center for Earth System Research and Sustainability, Universität Hamburg, Hamburg, Germany
  • 5Research Computing Center, Moscow State University, Moscow, Russia
  • 6Faculty of Geography, Moscow State University, Moscow, Russia
  • 7Moscow Center of Fundamental and Applied Mathematics, Moscow, Russia
  • 8Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
  • 9Department of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands

Abstract. We employ a new, process-based model for methane emissions from ponds (MeEP) to investigate the methane-emission response of polygonal-tundra ponds in Northeast Siberia to warming. Small and shallow water bodies such as ponds are vulnerable to warming due to their low thermal inertia compared to larger lakes, and the Arctic is warming at an above-average rate. While ponds are a relevant landscape-scale source of methane under the current climate, the response of pond methane emissions to warming is uncertain. MeEP differentiates between the three main pond types of the polygonal tundra, ice-wedge, polygonal-center, and merged polygonal ponds. The model resolves the three main pathways of methane emissions – diffusion, ebullition, and plant-mediated transport – at the temporal resolution of one hour, thus capturing daily and seasonal variability of the methane emissions. The model was tuned using chamber measurements resolving the three methane pathways. We perform idealized warming experiments, with increases in the mean annual temperature of 2.5, 5, and 7.5 °C on top of a historical simulation. The simulations reveal an overall increase of 1.33 g CH4 year-1 °C-1 per square meter of pond area. Under annual temperatures 5 °C above present temperatures pond methane emissions are more than three times higher than now. Most of this emission increase is due to the additional substrate provided by the increased net productivity of the vascular plants. Furthermore, plant-mediated transport is the dominating pathway of methane emissions in all simulations. We conclude that vascular plants as a substrate source and efficient methane pathway should be included in future pan-Arctic assessments of pond methane emissions.

Zoé Rehder et al.

Status: open (until 27 Feb 2023)

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Zoé Rehder et al.

Zoé Rehder et al.

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Short summary
We use a new model to investigate how methane emissions from Arctic ponds change with warming. We fine that emissions increase substantially. Under annual temperatures 5 °C above present temperatures pond methane emissions are more than three times higher than now. Most of this increase is caused by an increase in plant productivity as plant provide the substrate microbes use to produce methane. We conclude that vegetation changes need to be included in predictions of pond methane emissions.
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