Linking soil descriptions to the thawing of permafrost: insights into fate of carbon and nitrogen

• Main Authors: Harden, Jennifer W., Koven, C., Hugelius, Gustaf, Ping, Chien-Lu, McGuire, A. D., Camill, P., Jorgenson, Torre, Kuhry, Peter, Michaelson, G., O`Donnell, Jonathan A., Schuur, Edward. A. G., Tarnocai, Charles, Johnson, K., Grosse, Guido, Schädel, Christina
• Format: Conference Object
• Language: unknown
• Published: Stockholm University 2014
• Subjects: Active layer thickness; Ice; permafrost
• Online Access: https://epic.awi.de/id/eprint/35919/; https://hdl.handle.net/10013/epic.43835

Permafrost soils were characterized first in the field by numerous investigators according to standard soil descriptions and were sampled by depth increment within soil horizon boundaries. Measures of bulk density, C, N, and pH were used to further characterize C and N storage for soil horizons and profiles. Field attributes for organic (Oi, Oe, Oa or L, F, H) horizons, mineral (A, E, B, C) horizons, cryoturbated (jj subscripts with mixtures of organic and mineral matrices), and gleying (subscript g with reduced colors), ice-rich layers (e.g., Wf/Cgfjj, Wf/Oafjj) were examined for differences in C, N, and bulk density. Using the Community Climate System Model (CCSM4) we calculated cumulative distributions of active layer thickness (ALT) under current and future climates. We then superposed physical state over soil horizons to explore how chemical attributes are exposed by progressive thaw. Thawing will likely expose 147 Pg of C with 10 Pg of N by 2050 (representative concentration pathway RCP scenario 4.5) and as much as 436 PgC with 29 PgN by 2100 (RCP 8.5). This represents about 30% and 80% of circumarctic permafrost carbon for yr 2050 (RCP 4.5) and yr 2100 (RCP 8.5) scenarios, respectively. Organic horizons will likely contribute the earliest pulse of CO2 via combustion and decomposition. These changes have the potential for strong additional loading to our atmosphere, water resources, and ecosystems.