finding 11.2 : key-message-11-2

Soils in the northern circumpolar permafrost zone store 1,460 to 1,600 petagrams of organic carbon (Pg C), almost twice the amount contained in the atmosphere and about an order of magnitude more carbon than contained in plant biomass (55 Pg C), woody debris (16 Pg C), and litter (29 Pg C) in the boreal and tundra biomes combined. This large permafrost zone soil carbon pool has accumulated over hundreds to thousands of years. There are additional reservoirs in subsea permafrost and regions of deep sediments that are not added to this estimate because of data scarcity (very high confidence).



This finding is from chapter 11 of Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report.

Description of evidence base: Key Finding 2 is supported by observational evidence from ground-based measurements of ecosystem carbon pools. Large surface soil carbon pools (to 1 m in depth) have been reported in the literature for decades (e.g., Gorham 1991), with new information on deeper permafrost carbon pools accumulating over the last decade (Hugelius et al., 2014; Schuur et al., 2015; Tarnocai et al., 2009; Zimov et al., 2006). Biomass pools have been synthesized from forest inventory data (Pan et al., 2011), and more recently using remote sensing (Neigh et al., 2013; Raynolds et al., 2012).

New information and remaining uncertainties: There is very high confidence that permafrost soil carbon stocks are large and protected currently by waterlogged and frozen soil conditions across much of the region. There is also very high confidence that soil carbon stocks are more than 10 times larger than stocks of carbon in plant biomass, woody debris, and litter pools.

Assessment of confidence based on evidence: There is very high confidence that permafrost soil carbon stocks are large and protected currently by waterlogged and frozen soil conditions across much of the region. There is also very high confidence that soil carbon stocks are more than 10 times larger than stocks of carbon in plant biomass, woody debris, and litter pools.

Provenance
This finding was derived from figure P.2: P.2. Likelihood and Confidence Evaluation

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