Siberian CO2 efflux in winter as a CO2 source and cause of seasonality in atmospheric CO2

Abstract

Over three years, we found a consistent CO2 efflux from forest tundra of the Russian North throughout the year, including a large (89 g C m -2 yr -1 ) efflux during winter. Our results provide one explanation for the observations that the highest atmospheric CO2 concentration and greatest seasonal amplitude occur at high latitudes rather than over the mid-latitudes, where fossil fuel sources are large, and where high summer productivity offset by winter respiration should give large seasonal oscillations in atmospheric CO2. Winter respiration probably contributed substantially to the boreal winter CO2 efflux. Respiration is an exothermic process that produces enough heat to warm soils and promote further decomposition. We suggest that, as a result of this positive feedback, small changes in surface heat flux, associated with human activities in the North or with regional or global warming, could release large quantities of organic carbon that are presently stored in permafrost.

Ecosystem Respiration in a Seasonally Snow-Covered Subalpine Grassland

“…3), which is consistent with a growing body of evidence that respiration continues beneath snow (Sommerfeld et al, 1993;Zimov et al, 1996;Jones et al, 1999;Mariko et al, 2000;McDowell et al, 2000;Grogan et al, 2001;Grogan and Jonasson, 2005;Mo et al, 2005;Monson et al, 2006aMonson et al, , 2006bLarsen et al, 2007;Liptzin et al, 2009). Measured rates of ecosystem respiration under snow were between 0.2 and 0.9 mmol CO 2 m 22 s…”

“…The percentage of annual flux during the snow-covered season varies among studies from as little as 10-15% in cool-temperate deciduous forests in Japan (Mariko et al, 2000;Mo et al, 2005) and coniferous subalpine forest in Austria (Schindlbacher et al, 2007), to as much as 50% in tundra forest in Russia (Zimov et al, 1996). These trends among sites in the quantitative significance of respiration beneath snow suggest that the length of the snowcovered season would appear to be one of the main determinants of the percentage of annual flux during the snow-covered season.…”

“…In alpine and subalpine ecosystems of the northern hemisphere, under-snow respiration is commonly 10-20% of annual respiration (Brooks et al, 1996(Brooks et al, , 1997Mariko et al, 2000;McDowell et al, 2000;Mo et al, 2005;Monson et al, 2006a;Schindlbacher et al, 2007), but may be as high as 30% (subalpine meadow in Colorado [Liptzin et al, 2009]), or even 50% (tundra forest in Russia [Zimov et al, 1996]). In the present study, under-snow ecosystem respiration was estimated to be 4.1-4.3% of annual ecosystem respiration using a model with two temperature response functions (Table 2) or 5.9-7.1% using one temperature response function (data not shown).…”

Wintertime CO2 efflux from Arctic soils: Implications for annual carbon budgets

“…By including the winter respiratory losses reported in this study, estimates of annual soil respiration in arctic tundra increase by 3% to 41%, depending on the tundra community type (Table 2) [Zimov et al, 1993[Zimov et al, , 1996 Keeling, C.D., J.F.S. Chin, and T.P.…”

Modeling permafrost thaw and ecosystem carbon cycle under annual and seasonal warming at an Arctic tundra site in Alaska

“…Frozen C within permafrost zone can be stimulated by warming via microbial decomposition and released to the atmosphere in a large quantity and spatial extent Tarnocai et al, 2009;Harden et al, 2012]. Thawing permafrost therefore can increase the amplitude of the C cycle and exert an important influence on the future landscape level C balance [Zimov et al, 1996]. It was recently hypothesized that the permafrost thawed carbon can be up to 147-436 pg C from 2050 to 2100 [Harden et al, 2012;Schuur et al, 2013].…”