Arctic soil methane sink increases with drier conditions and higher ecosystem respiration

Abstract

Arctic wetlands are known methane (CH4) emitters but recent studies suggest that the Arctic CH4 sink strength may be underestimated. Here we explore the capacity of well-drained Arctic soils to consume atmospheric CH4 using >40,000 hourly flux observations and spatially distributed flux measurements from 4 sites and 14 surface types. While consumption of atmospheric CH4 occurred at all sites at rates of 0.092 ± 0.011 mgCH4 m−2 h−1 (mean ± s.e.), CH4 uptake displayed distinct diel and seasonal patterns reflecting ecosystem respiration. Combining in situ flux data with laboratory investigations and a machine learning approach, we find biotic drivers to be highly important. Soil moisture outweighed temperature as an abiotic control and higher CH4 uptake was linked to increased availability of labile carbon. Our findings imply that soil drying and enhanced nutrient supply will promote CH4 uptake by Arctic soils, providing a negative feedback to global climate change.

Permafrost Carbon: Progress on Understanding Stocks and Fluxes Across Northern Terrestrial Ecosystems

“…However, barriers remain to using these manual chamber data for modeling because of the limited spatial and temporal scales of measurements; statistical upscaling may offer some possibilities to further use these data (Natali et al, 2019;Virkkala et al, 2021a). Semi-permanent mobile towers or automated chambers could be utilized to enhance spatial coverage and complement the existing flux network of long-term monitoring sites (Varner et al, 2022;Voigt et al, 2023). Further improvements in flux estimates can be expected as new sites are added, more recent data are integrated to repositories, and newer methods are developed to leverage the sparse and disparate existing datasets.…”

“…Unlike upland areas in temperate regions that are net sinks of atmospheric CH 4 (Le Mer & Roger, 2001), upland (i.e., nonwetland) areas in tundra and boreal forest can be net CH 4 sources to the atmosphere due to periodically saturated conditions and cold-season emissions (Hashemi et al, 2021;Hiyama et al, 2021;Kuhn et al, 2021b;Treat et al, 2018b;Zona et al, 2016). However, upland tundra can also oxidize more CH 4 than previously thought (Jorgensen et al, 2015;Oh et al, 2020;Voigt et al, 2023); understanding the controls on these differences and net effect remains to be explored. For permafrost wetlands, CH 4 emissions are generally smaller than in permafrostfree wetlands due to the lower temperatures (Kuhn et al, 2021b;Olefeldt et al, 2013;Treat et al, 2018b).…”

“…Challenges also remain for modeling CH 4 cycling beyond the borders of wetlands, particularly in uplands and lakes. Uplands cover close to 80% of the permafrost region and can be both annual CH 4 sources (Zona et al, 2016) and sinks (Oh et al, 2020;Voigt et al, 2023). Wetlands and lakes have differing CH 4 emissions and processes (Kuhn et al, 2021b;Wik et al, 2016), but distinguishing these landforms in observations and remote sensing images can be difficult, leading to possible double counting of emissions sources (Thornton et al, 2016).…”

Atmospheric methane removal may reduce climate risks

“…Proposed approaches in this category include soil amendments and selectively breeding or engineering methanotrophs to increase their affinity for methane. The factors limiting natural biological methane sinks-such as the presence of nitrogen and copper, water saturation, and methane concentration [18]-must be better understood in order to evaluate the potential for scaling up enhancement of these sinks. As for all approaches, any increase in methane oxidation must be weighed against potential negative side effects, including nitrous oxide production and water quality impacts from runoff.…”

The Net GHG Balance and Budget of the Permafrost Region (2000–2020) From Ecosystem Flux Upscaling

“…Despite their large spatial coverage, the Dry Tundra was a small source of CH 4 during the growing season (1.4 ( 0.3, 2.9) Tg CH 4 -C gs 1 ), although the low end of the CI suggests that it could remain a sink. More measurements from these drier ecosystems are needed, as also recent studies indicate that tundra soils, in particular well-drained uplands, could be important CH 4 sinks (D'Imperio et al, 2023;Oh et al, 2020;Voigt et al, 2023). Note.…”