Soil Organic Carbon Storage and Distribution in Arctic Tundra, Barrow, Alaska

Soil organic C (SOC) levels were determined to a depth of 100 cm for the nine units designated on a 1957 1:20000 soil map of Barrow, AK prepared by J.V. Drew. The legend was updated by converting Drew's map units into the recently adopted Gelisol order in U.S. soil taxonomy and field verified. The SOC varied from 2.5 kg m −3 in modern beach sediments to >73 kg m −3 in Typic Sapristels in high‐centered, ice‐wedge polygons developed in reworked organic‐rich lake sediments. The SOC averaged 50 kg m −3 for the entire 64‐km 2 area (excluding open water). Considerable variability in SOC exists within individual soil map units. For example, SOC levels in a Typic Aquiturbel (formerly classified as a Meadow Tundra, Normal Phase soil) ranged from 24 to 109 kg m −3 Substantial variation in SOC occurs within individual patterned‐ground units. For a high‐centered, ice‐wedge polygon with a diameter of 15 m, SOC levels are 24, 32, and 64 kg m −3 for the wedge trough, rim, and center, respectively. In a low‐centered, ice‐wedge polygon, SOC levels are 28 and 83 kg m −3 for the trough and center. The variation in SOC within soil map units and individual patterned‐ground units is due primarily to differences in the amount of ground ice. Active‐layer thickness varies within and between soil map units, ranging from 31 cm in Typic Sapristels to >100 cm in modern beach sediments. About 47% of the SOC in the upper meter of soil was in the active layer at the time of sampling; the remainder occurring in frozen ground, much of it meeting the definition of permafrost. Some of the SOC originates from past reworking of organic‐rich lake sediments. Carbon stocks in near‐surface permafrost may be of global significance and should be inventoried in other tundra regions.