Carbon dioxide sources from Alaska driven by increasing early winter respiration from Arctic tundra

TitleCarbon dioxide sources from Alaska driven by increasing early winter respiration from Arctic tundra
Publication TypeJournal Article
Year of Publication2017
AuthorsCommane R, Lindaas J, Benmergui J, Luus KA, Chang RY-W, Daube BC, Euskirchen ES, Henderson JM, Karion A, Miller JB, Miller SM, Parazoo NC, Randerson JT, Sweeney C, Tans P, Thoning K, Veraverbeke S, Miller CE, Wofsy SC
JournalProceedings of the National Academy of Sciences
Volume114
Issue21
Pagination5361
Date Published2017/05/23
AbstractRising arctic temperatures could mobilize reservoirs of soil organic carbon trapped in permafrost. We present the first quantitative evidence for large, regional-scale early winter respiration flux, which more than offsets carbon uptake in summer in the Arctic. Data from the National Oceanic and Atmospheric Administration’s Barrow station indicate that October through December emissions of CO2 from surrounding tundra increased by 73% since 1975, supporting the view that rising temperatures have made Arctic ecosystems a net source of CO2. It has been known for over 50 y that tundra soils remain unfrozen and biologically active in early winter, yet many Earth System Models do not correctly represent this phenomenon or the associated CO2 emissions, and hence they underestimate current, and likely future, CO2 emissions under climate change.High-latitude ecosystems have the capacity to release large amounts of carbon dioxide (CO2) to the atmosphere in response to increasing temperatures, representing a potentially significant positive feedback within the climate system. Here, we combine aircraft and tower observations of atmospheric CO2 with remote sensing data and meteorological products to derive temporally and spatially resolved year-round CO2 fluxes across Alaska during 2012–2014. We find that tundra ecosystems were a net source of CO2 to the atmosphere annually, with especially high rates of respiration during early winter (October through December). Long-term records at Barrow, AK, suggest that CO2 emission rates from North Slope tundra have increased during the October through December period by 73% ± 11% since 1975, and are correlated with rising summer temperatures. Together, these results imply increasing early winter respiration and net annual emission of CO2 in Alaska, in response to climate warming. Our results provide evidence that the decadal-scale increase in the amplitude of the CO2 seasonal cycle may be linked with increasing biogenic emissions in the Arctic, following the growing season. Early winter respiration was not well simulated by the Earth System Models used to forecast future carbon fluxes in recent climate assessments. Therefore, these assessments may underestimate the carbon release from Arctic soils in response to a warming climate.
URLhttp://www.pnas.org/content/114/21/5361.abstract
Short TitleProc Natl Acad Sci USA