Simulated methane emissions from Arctic ponds are highly sensitive to warming

• Published in: Biogeosciences
• Main Authors: Rehder, Zoé, Kleinen, Thomas, Kutzbach, Lars, Stepanenko, Victor, Langer, Moritz, Brovkin, Victor
• Format: Text
• Language: English
• Published: 2023
• Subjects: Arctic; Tundra; Siberia
• Online Access: https://doi.org/10.5194/bg-20-2837-2023; https://bg.copernicus.org/articles/20/2837/2023/

The Arctic is warming at an above-average rate, and small, shallow waterbodies such as ponds are vulnerable to this warming due to their low thermal inertia compared to larger lakes. While ponds are a relevant landscape-scale source of methane under the current climate, the response of pond methane emissions to warming is uncertain. We employ a new, process-based model for methane emissions from ponds (MeEP) to investigate the methane emission response of polygonal-tundra ponds in northeastern Siberia to warming. MeEP is the first dedicated model of pond methane emissions which differentiates between the three main pond types of the polygonal-tundra, ice-wedge, polygonal-center, and merged polygonal ponds and resolves the three main pathways of methane emissions – diffusion, ebullition, and plant-mediated transport. 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 approximately linear increase in emissions from ponds of 1.33 g CH 4 yr −1 ∘ C −1 m −2 in this temperature range. Under annual temperatures 5 ∘ C above present temperatures, pond methane emissions are more than 3 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.