The importance of "Deep" organic carbon in permafrost-affected soils of arctic Alaska

Reporting characteristics for the upper 100 cm of the pedon is common for Gelisols and soil C budgets. The amount of soil organic carbon (SOC) sequestered at a depth of 100 to 200 cm was determined for 29 permafrost-affected soils from northern Alaska. An average of 29 kg C m(-3) was present within the 100- to 200-cm depth interval, which is contained in the upper permafrost. For a 200-cm-deep profile, about 36% of the SOC pool occurs below 100 cm. From limited data, there were no significant differences in "deep" SOC levels among Histels, Turbels, and Orthels, the three suborders of Gelisols. Based on a previous survey of the Barrow Peninsula, permafrost-affected soils, contain 66.5 Tg of SOC in the upper 100 cm, and another 36 Tg in the 100- to 200-cm zone. This C pool is vulnerable to mobilization following warming and increased summer thaw depth in the arctic.