The permafrost carbon feedback, ctd

Field information links permafrost carbon to physical vulnerabilities of thawing

Deep soil profiles containing permafrost (Gelisols) were characterized for organic carbon (C) and total nitrogen (N) stocks to 3 m depths. Using the Community Climate System Model (CCSM4) we calculate cumulative distributions of active layer thickness (ALT) under current and future climates. The difference in cumulative ALT distributions over time was multiplied by C and N contents of soil horizons in Gelisol suborders to calculate newly thawed C and N. Thawing ranged from 147 PgC with 10 PgN by 2050 (representative concentration pathway RCP scenario 4.5) to 436 PgC with 29 PgN by 2100 (RCP 8.5). Organic horizons that thaw are vulnerable to combustion, and all horizon types are vulnerable to shifts in hydrology and decomposition. The rates and extent of such losses are unknown and can be further constrained by linking field and modelling approaches. These changes have the potential for strong additional loading to our atmosphere, water resources, and ecosystems. 

Similar general estimates as compared with this paper: 68 billion tons to 508 billion tons in 2100 versus 436 billion tons. This is estimated thawed carbon, though; it's not clear to me from the abstract if they even attempt to estimate how much of that ends up in the atmosphere. This is particularly important in the case of nitrogen, given that NO2 is a powerful greenhouse gas (with 310 times the warming potential of CO2) as well as an ozone-eating chemical.