Winter CH4 and CO2 Accumulation from a Permafrost Peatland Pond is Critical to Spring thaw Carbon Emissions

Abstract

Peatland ponds are abundant in the boreal permafrost landscapes, which is a hotspot for greenhouse gas emissions. In this study, we observed annual CH₄ and CO₂ fluxes, as well as CH₄ and CO₂ concentrations of water and ice-trapped bubbles in a peatland pond in the permafrost region of Northeast China. The results show that water CH₄ and CO₂ concentrations increased by 1–4 orders of magnitude during the ice cover period compared to the open water period. (CH₄: 300.37 µM vs. 0.014 µM, CO₂: 2915.73 µM vs. 300.34 µM). During the spring thaw period, water CH₄ and CO₂ concentrations decrease dramatically, with CH₄ and CO₂ fluxes reaching the highest values (CH₄ flux: 30.01 mg m^− 2 h^− 1, CO₂ flux: 401.88 mg m^− 2 h^− 1). High fluxes of CH₄ and CO₂ during the spring thaw period came not only from the release of CH₄ and CO₂ in water under the ice, but also from bubbles trapped in the ice. This study showed the importance of considering CH₄ and CO₂ storage during the ice cover period and spring thaw fluxes in boreal peatland ponds. Given that dynamics of CH₄ and CO₂ fluxes during the spring thaw period in peatland ponds remain understudied, we encourage an increased focus on observations of CH₄ and CO₂ fluxes dynamics during the spring thaw period. The lack of observation during the spring thaw period may underestimate the annual budget for CH₄ and CO₂ in peatland ponds.