Large tundra methane burst during onset of freezing

Mastepanov, Mikhail; Sigsgaard, Charlotte; Dlugokencky, Edward J.; Houweling, Sander; Ström, Lena; Tamstorf, Mikkel P.; Christensen, Torben R.

doi:10.1038/nature07464

Cited by 304 publications

(308 citation statements)

References 20 publications

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“…Warming ground can play a significant role in carbon cycles in landatmosphere processes (Koven et al, 2011;Schuur et al, 2009;DeConto et al, 2012;Tagesson et al, 2012), but the mechanism of this role is complex and not clear, even though studies have found correlations between growing season carbon fluxes and increased soil temperature, particularly in the high Arctic (Tagesson et al, 2012;Mastepanov et al, 2008;Heimann and Reichstein, 2008). Other studies have shown that increasing temperature results in the lengthening of the growing season and improved productivity (Kimball et al, 2006;Barichivich et al, 2013).…”

Section: Comparisons With Previous Resultsmentioning

confidence: 99%

Changes in the timing and duration of the near-surface soil freeze/thaw status from 1956 to 2006 across China

2015

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Abstract. The near-surface soil freeze/thaw status is an important indicator of climate change. Using data from 636 meteorological stations across China, we investigated the changes in the first date, the last date, the duration, and the number of days of the near-surface soil freeze over the period 1956-2006. The results reveal that the first date of the near-surface soil freeze was delayed by about 5 days, or at a rate of 0.10 ± 0.03 day yr −1 , and the last date was advanced by about 7 days, or at a rate of 0.15 ± 0.02 day yr −1 . The duration of the near-surface soil freeze decreased by about 12 days or at a rate of 0.25 ± 0.04 day yr −1 , while the actual number of the near-surface soil freeze days decreased by about 10 days or at a rate of 0.20 ± 0.03 day yr −1 . The rates of changes in the near-surface soil freeze/thaw status increased dramatically from the early 1990s through the end of the study period. Regionally, the changes in western China were greater than those in eastern China. Changes in the nearsurface soil freeze/thaw status were primarily controlled by changes in air temperature, but urbanization may also play an important role.

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Section: Comparisons With Previous Resultsmentioning

confidence: 99%

Changes in the timing and duration of the near-surface soil freeze/thaw status from 1956 to 2006 across China

2015

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“…However, the fall, winter, and spring months represent 70-80% of the year in the Arctic and have been shown to have significant emissions of CO 2 (16)(17)(18). The few measurements of CH 4 fluxes in the Arctic that extend into the fall (6,7,9,10) show complex patterns of CH 4 emissions, with a number indicating high fluxes (7,10). Winter and early spring data appear to be absent in Arctic tundra over continuous permafrost.…”

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confidence: 99%

“…This period has been denoted as the "zero curtain" (19). Soil freezing toward the end of the zero curtain period was considered responsible for sporadic peaks in CH 4 emissions observed in the fall (7,10), but very sparse data are available to evaluate the importance of fall emissions over a larger scale. The processes influencing CH 4 production and emission in tundra during the cold period ( Fig.…”

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confidence: 99%

Cold season emissions dominate the Arctic tundra methane budget

Zona

Gioli

Commane

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

331

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Arctic terrestrial ecosystems are major global sources of methane (CH 4 ); hence, it is important to understand the seasonal and climatic controls on CH 4 emissions from these systems. Here, we report year-round CH 4 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 CH 4 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 CH 4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH 4 derived from aircraft data demonstrate the large spatial extent of late season CH 4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH 4 y −1 , ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH 4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.permafrost | aircraft | fall | winter | warming E missions of methane (CH 4 ) from Arctic terrestrial ecosystems could increase dramatically in response to climate change (1-3), a potentially significant positive feedback on climate warming. High latitudes have warmed at a rate almost two times faster than the Northern Hemisphere mean over the past century, with the most intense warming in the colder seasons (4) [up to 4°C in winter in 30 y (5)]. Poor understanding of controls on CH 4 emissions outside of the summer season (6-10) represents a large source of uncertainty for the Arctic CH 4 budget. Warmer air temperatures and increased snowfall can potentially increase soil temperatures and deepen the seasonal thawed layer, stimulating CH 4 and CO 2 emissions from the vast stores of labile organic matter in the Arctic (11). The overwhelming majority of prior studies of CH 4 fluxes in the Arctic have been carried out during the summer months (12-15). However, the fall, winter, and spring months represent 70-80% of the year in the Arctic and have been shown to have significant emissions of CO 2 (16-18). The few measurements of CH 4 fluxes in the Arctic that extend into the fall (6, 7, 9, 10) show complex patterns of CH 4 emissions, with a number indicating high fluxes (7, 10). Winter and early spring data appear to be absent in Arctic tundra over continuous permafrost.Beginning usually in late August or early September, the...

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“…Until now it is unclear whether permafrost regions will turn into massive sources of greenhouse gases, such as methane and carbon dioxide, as the frozen soils begin to thaw (Hobbie et al, 2000;Davidson and Janssens, 2006). Recent measurements taken at wet tundra landscapes demonstrate the importance of the freeze and thaw dynamics for methane emission, which are related in a non-linear manner (Christensen et al, 2003;Sachs et al, 2008;Mastepanov et al, 2008). For this purpose, efforts have been initiated to incorporate permafrost and the annual freeze and thaw dynamics into global climate models (e.g., Stendel and Christensen, 2002;Lawrence and Slater, 2005;Nicolsky et al, 2007;Lawrence et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

The surface energy balance of a polygonal tundra site in northern Siberia – Part 1: Spring to fall

et al. 2011

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Abstract. In this article, we present a study on the surface energy balance of a polygonal tundra landscape in northeast Siberia. The study was performed during half-year periods from April to September in each of 2007 and 2008. The surface energy balance is obtained from independent measurements of the net radiation, the turbulent heat fluxes, and the ground heat flux at several sites. Short-wave radiation is the dominant factor controlling the magnitude of all the other components of the surface energy balance during the entire observation period. About 50% of the available net radiation is consumed by the latent heat flux, while the sensible and the ground heat flux are each around 20 to 30%. The ground heat flux is mainly consumed by active layer thawing. About 60% of the energy storage in the ground is attributed to the phase change of soil water. The remainder is used for soil warming down to a depth of 15 m. In particular, the controlling factors for the surface energy partitioning are snow cover, cloud cover, and the temperature gradient in the soil. The thin snow cover melts within a few days, during which the equivalent of about 20% of the snow-water evaporates or sublimates. Surface temperature differences of the heterogeneous landscape indicate spatial variabilities of sensible and latent heat fluxes, which are verified by measurements. However, spatial differences in the partitioning between sensible and latent heat flux are only measured during conditions of high radiative forcing, which only occur occasionally.

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Large tundra methane burst during onset of freezing

Cited by 304 publications

References 20 publications

Changes in the timing and duration of the near-surface soil freeze/thaw status from 1956 to 2006 across China

Changes in the timing and duration of the near-surface soil freeze/thaw status from 1956 to 2006 across China

Cold season emissions dominate the Arctic tundra methane budget

The surface energy balance of a polygonal tundra site in northern Siberia – Part 1: Spring to fall

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