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Title: Cold season emissions dominate the Arctic tundra methane budget

Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥ 50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the “zero curtain” period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y–1, ~25% of global emissions from extratropical wetlands, or ~6% of total global wetland methane emissions. Here, the dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra aremore » not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.« less
Authors:
 [1] ;  [2] ; ORCiD logo [3] ;  [3] ;  [3] ;  [4] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [10] ;  [10] ;  [11] ;  [12] ;  [12] ;  [10] ;  [13]
  1. San Diego State Univ., San Diego, CA (United States); Univ. of Sheffield, Sheffield (United Kingdom)
  2. Institute of Biometeorology, Firenze (Italy)
  3. Harvard Univ., Cambridge, MA (United States)
  4. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  5. Univ. of Helsinki, Helsinki (Finland)
  6. Univ. of Colorado, Boulder, CO (United States); National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States)
  7. Univ. of Colorado, Boulder, CO (United States)
  8. Harvard Univ., Cambridge, MA (United States); Dalhousie Univ., Halifax, NS (Canada)
  9. Atmospheric and Environmental Research, Inc., Lexington, MA (United States)
  10. San Diego State Univ., San Diego, CA (United States)
  11. Univ. of Alaska, Fairbanks, AK (United States)
  12. The Univ. of Montana, Missoula, MT (United States)
  13. San Diego State Univ., San Diego, CA (United States); Open Univ., Milton Keynes (United Kingdom)
Publication Date:
OSTI Identifier:
1237500
Grant/Contract Number:
SC0005160; SC005160
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 1; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
San Diego State Univ., San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; permafrost; aircraft; fall; winter; warming