Journal
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Volume 125, Issue 6, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2019JG005528
Keywords
permafrost; climate change; Arctic; tundra; carbon
Funding
- U.S. Department of Energy, Office of Biological and Environmental Research, Terrestrial Ecosystem Science (TES) Program [DE-SC0006982, DESC0014085]
- National Science Foundation CAREER program [0747195]
- National Parks Inventory and Monitoring Program
- National Science Foundation Bonanza Creek LTER program [1026415]
- National Science Foundation Office of Polar Programs [1203777]
- NNA: LTREB: The Arctic Carbon and Climate (ACCLIMATE) Observatory: Tundra Ecosystem Carbon Balance and Old Carbon Loss as a Consequence of Permafrost Degradation [1754839]
- Direct For Biological Sciences
- Division Of Environmental Biology [0747195] Funding Source: National Science Foundation
- Division Of Environmental Biology
- Direct For Biological Sciences [1026415] Funding Source: National Science Foundation
- Office of Polar Programs (OPP)
- Directorate For Geosciences [1203777] Funding Source: National Science Foundation
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Permafrost thaw is typically measured with active layer thickness, or the maximum seasonal thaw measured from the ground surface. However, previous work has shown that this measurement alone fails to account for ground subsidence and therefore underestimates permafrost thaw. To determine the impact of subsidence on observed permafrost thaw and thawed soil carbon stocks, we quantified subsidence using high-accuracy GPS and identified its environmental drivers in a permafrost warming experiment near the southern limit of permafrost in Alaska. With permafrost temperatures near 0 degrees C, 10.8 cm of subsidence was observed in control plots over 9 years. Experimental air and soil warming increased subsidence by five times and created inundated microsites. Across treatments, ice and soil loss drove 85-91% and 9-15% of subsidence, respectively. Accounting for subsidence, permafrost thawed between 19% (control) and 49% (warming) deeper than active layer thickness indicated, and the amount of newly thawed carbon within the active layer was between 37% (control) and 113% (warming) greater. As additional carbon thaws as the active layer deepens, carbon fluxes to the atmosphere and lateral transport of carbon in groundwater could increase. The magnitude of this impact is uncertain at the landscape scale, though, due to limited subsidence measurements. Therefore, to determine the full extent of permafrost thaw across the circumpolar region and its feedback on the carbon cycle, it is necessary to quantify subsidence more broadly across the circumpolar region.
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