Carbon Dioxide and Methane Flux in a Dynamic Arctic Tundra Landscape: Decadal‐Scale Impacts of Ice Wedge Degradation and Stabilization. Issue 22 (18th November 2020)

• Record Type: Journal Article
• Authors: Wickland, K. P.; Jorgenson, M. T.; Koch, J. C.; Kanevskiy, M.; Striegl, R. G.
• Is Part Of: Geophysical research letters. Volume 47:Issue 22(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-18
• Subjects: carbon dioxide -- methane -- thermokarst pond -- greenhouse gas -- Arctic; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL089894
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Ice wedge degradation is a widespread occurrence across the circumpolar Arctic causing extreme spatial heterogeneity in water distribution, vegetation, and energy balance across landscapes. These heterogeneities influence carbon dioxide (CO2 ) and methane (CH4 ) fluxes, yet there is little understanding of how they effect change in landscape‐level carbon (C) gas flux over time. We measured CO2 and CH4 fluxes in an area undergoing ice wedge degradation near Prudhoe Bay, Alaska, and combined with repeat imagery analysis to estimate seasonal landscape‐level C flux response to geomorphic change. Net CO2 and CH4 emissions changed by −25% and +42%, respectively, resulting in a 14% increase in seasonal CO2 ‐C equivalent emissions over 69 years as ice wedge degradation formed water‐filled troughs. The dynamic ice wedge degradation/stabilization process can cause significant changes in CO2 and CH4 fluxes over time, and the integration of this process is important to forecasting landscape‐level C fluxes in permafrost regions abundant in ice wedges. Plain Language Summary: Large wedge‐shaped masses of ice commonly occur in Arctic tundra just below the ground surface. These ice wedges form polygon patterns observable by aircraft and remote sensing. Warming temperatures are causing ice wedges to melt, forming troughs that widen, deepen, and flood over time to become small ponds. Some ice wedges reform over decades as troughs become drier and seasonal frost persists belowground. We conducted field measurements to quantify how melting and regrowing ice wedges affect the exchange of greenhouse gases carbon dioxide (CO2 ) and methane (CH4 ) between ground and pond surfaces and Earth's atmosphere in an area of Arctic Alaska where ice wedges are melting, and some are regrowing. Then we combined field measurement results with study area aerial photos from nine different years during 1949–2018 to assess how ice wedge distribution and greenhouse gas exchange has changed over the past seven decades. CH4 emissions to the atmosphere increased over time as ice wedges melted, but at the same time, more CO2 was taken out of the atmosphere by increased localized plant growth, counteracting some of the warming effect of CH4 . The balance of these simultaneous changes indicates a net potential of melting ice wedges to add to a warming climate. Key Points: Mean seasonal CO2 and CH4 fluxes were significantly different across ice wedge degradation/stabilization stages Ice wedge degradation decreased seasonal net CO2 emissions and increased CH4 emissions at the landscape scale over 69 years Seasonal CO2 ‐C equivalent flux was strongly correlated with abundance of water‐filled troughs formed from advanced ice wedge degradation