Surface water inundation in the boreal-Arctic: potential impacts on regional methane emissions

TLDR

Northern wetlands may be vulnerable to increased methane emissions under warming trends, yet dynamic open‑water inundation and wetting/drying patterns could constrain regional releases, offsetting potential gains. The study aims to investigate how surface warming and moisture variability jointly influence high‑latitude wetland methane emissions using satellite data. A satellite‑driven model assessed sub‑grid changes in fractional water inundation at 15‑day, monthly, and annual intervals with 25‑km microwave retrievals, and evaluated the impact of recent wetting/drying on emissions. Model simulations indicate boreal‑Arctic wetlands emit ~53 Tg CH₄ yr⁻¹ in summer, with 10–16 % from open water and emergent vegetation, and that Arctic wetting and summer warming increased emissions by 0.56 Tg yr⁻¹ while sub‑Arctic drying offset this by 0.38 Tg yr⁻¹, underscoring the need to monitor surface moisture and temperature changes.

Abstract

Northern wetlands may be vulnerable to increased carbon losses from methane (CH4), a potent greenhouse gas, under current warming trends. However, the dynamic nature of open water inundation and wetting/drying patterns may constrain regional emissions, offsetting the potential magnitude of methane release. Here we conduct a satellite data driven model investigation of the combined effects of surface warming and moisture variability on high northern latitude (⩾45° N) wetland CH4 emissions, by considering (1) sub-grid scale changes in fractional water inundation (Fw) at 15 day, monthly and annual intervals using 25 km resolution satellite microwave retrievals, and (2) the impact of recent (2003–11) wetting/drying on northern CH4 emissions. The model simulations indicate mean summer contributions of 53 Tg CH4 yr−1 from boreal-Arctic wetlands. Approximately 10% and 16% of the emissions originate from open water and landscapes with emergent vegetation, as determined from respective 15 day Fw means or maximums, and significant increases in regional CH4 efflux were observed when incorporating satellite observed inundated land fractions into the model simulations at monthly or annual time scales. The satellite Fw record reveals widespread wetting across the Arctic continuous permafrost zone, contrasting with surface drying in boreal Canada, Alaska and western Eurasia. Arctic wetting and summer warming increased wetland emissions by 0.56 Tg CH4 yr−1 compared to the 2003–11 mean, but this was mainly offset by decreasing emissions (−0.38 Tg CH4 yr−1) in sub-Arctic areas experiencing surface drying or cooling. These findings underscore the importance of monitoring changes in surface moisture and temperature when assessing the vulnerability of boreal-Arctic wetlands to enhanced greenhouse gas emissions under a shifting climate.