Elevated Spring Methane Emissions in a Sub‐Arctic Peatland Fen

Abstract

The Arctic boreal region is rapidly shifting in response to global climate change, including rapid warming and permafrost thaw. Year‐round monitoring of carbon fluxes in these regions is crucial to understanding seasonal and annual carbon budgets, including methane (CH4), a potent greenhouse gas with 80 times the warming potential of carbon dioxide over a 20‐year timeframe. Here we investigate the seasonal patterns and controls of CH4 fluxes from a subarctic peatland fen in Churchill, MB, Canada using eddy covariance CH4 flux data from 2008 to 2011 and more recent data from 2022 to 2023 in the same location. Recent data showed that surface soil temperature beneath a hollow water pool was the best predictor of CH4 emissions with an r2 of 0.79. There was a negative hysteretic trend in the relationship between CH4 and soil temperature, characterized by a sustained spring methane pulse and tapering off CH4 emissions in the fall, which is uncommon in both Arctic and wetland ecosystems. The spring pulse caused a 9.8% higher budget than would be expected based on the temperature relationship alone. The total annual CH4 budget was 61% or 3.1 g CH4‐C m−2 y−1 higher in 2023 (8.3 ± 1.0 g CH4‐C m−2 y−1) compared to the average 2008–2011 annual estimate (5.2 ± 0.6 g CH4‐C m−2 y−1).