Spatiotemporal variability and environmental controls on aquatic methane emissions in an Arctic permafrost catchment

Abstract. Understanding spatiotemporal dynamics and drivers of methane (CH4) fluxes from rapidly changing permafrost regions is critical for improving our understanding of such changes. Between May and August 2023 and 2024, we measured CH4 using floating chambers in a small Arctic permafrost catchment on Disko Island, Greenland. Fluxes were derived from 707 chamber measurements using a semi-automated algorithm incorporating boosted regression trees and generalized additive models. Highest fluxes occurred in streams and along lakeshores associated with inlets. Diffusive fluxes dominated (∼ 98 % of observations), while only ∼ 1 % of chamber deployments exhibited non-linear concentration increases indicative of ebullition, while the other ∼ 1 % were attributed to uptake. Median diffusive fluxes were 5.0 nmol m−2 s−1 (−0.1 to 271.8), peaking at ice-break. Ebullition had a median of 939 nmol m−2 s−1 (5.2–14 893), but did not impact overall fluxes. Model results suggest that thaw-season CH4 fluxes were initially driven by meteorological conditions and catchment soil conditions, but shifted rapidly – within approximately one week after ice-off – to biogeochemical controls, including dissolved organic matter, oxygen saturation, and pH.