Abrupt permafrost thaw drives spatially heterogeneous soil moisture and carbon dioxide fluxes in upland tundra

• DOI: 10.1111/gcb.16936
• Publication Date: 2023-09-11T12:20:15Z
• Authors: Heidi Rodenhizer; Susan M. Natali; Marguerite Mauritz; Meghan A. Taylor; Gerardo Celis; Stephanie Kadej; Allison K. Kelley; Emma R. Lathrop; Justin Ledman; Elaine F. Pegoraro; Verity G. Salmon; Christina Schädel; Craig See; Elizabeth E. Webb; Edward A. G. Schuur
• Keywords: Thermokarst; Soil carbon; Growing season; Active layer; Carbon sink

Permafrost thaw causes the seasonally thawed active layer to deepen, causing Arctic shift toward carbon release as soil organic matter becomes susceptible decomposition. Ground subsidence initiated by ice loss can cause these soils collapse abruptly, rapidly shifting moisture microtopography changes and also accelerating nutrient mobilization. The uncertainty of trajectories during makes it difficult predict role abrupt in suppressing or exacerbating losses. In this study, we investigated conditions on dioxide fluxes a 13-year permafrost warming experiment that exhibited thaw. Warming deepened differentially across treatments, leading variable rates formation thermokarst depressions. turn, differential caused gradient conditions, with some plots becoming consistently inundated water within depressions others exhibiting generally dry, but more outside Experimentally induced initially drove increasing growing season gross primary productivity (GPP), ecosystem respiration (Reco ), net exchange (NEE) (higher uptake), began reverse trend high level spatial heterogeneity. Plots subsided at slowest rate stayed relatively dry supported higher CO2 throughout experiment, while very into center feature became wet experienced rapid decline GPP, Reco , NEE (lower uptake release). These findings indicate Earth system models, which do not simulate often drier likely overestimate abruptly thawing landscapes.