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

Abstract

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‐km2 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.

Permafrost soils and carbon cycling

“…However, as concerns about global warming increased, this raised fears that the organic carbon stored in permafrost-region soils might become a source of rather than a sink for atmospheric carbon (Oechel et al, 1993). Consequently, a series of studies was conducted in the northern circumpolar regions to explore the depth distribution of stored biogenic carbon in Gelisols (Michaelson et al, 1996Ping et al, 1998Ping et al, , 2008bBockheim and Hinkel, 2007;Bockheim et al, 1999;Tarnocai et al, 2009;Hugelius et al, 2010Hugelius et al, , 2013aStrauss et al, 2012Strauss et al, , 2013. Generally, on gentle to moderate slopes of glaciated uplands, SOM was cryoturbated to depths of mostly 80 to 120 cm.…”

Temporal stereophotogrammetric analysis of retrogressive thaw slumps on Herschel Island, Yukon Territory

“…1) is one of the most ice-rich areas in the Canadian Arctic with widespread massive ground ice, and numerous retrogressive thaw slumps (Lantuit and Pollard, in review 1 ;Pollard, 1990;Pollard and French, 1980). Permafrost soils are widely recognized as potential reservoirs of organic carbon and greenhouse gases (Bockheim et al, 1999;Oechel et al, 1995). If the volume fraction of soil organic carbon (SOC) is known, the volume of sediments removed by thermokarst and coastal erosion can be used to estimate the potential contribution of organic carbon from arctic coasts into the Arctic Ocean (Rachold et al.…”

“…An increase in SOC released by Arctic coasts would potentially modify the carbon balance of the Arctic Ocean (Rachold et al, 2003). Under most climate change scenarios thermokarst processes are expected to increase, but since there are no long-term studies of thaw-related volume losses and only a few estimates of carbon content (Bockheim et al, 1999), this potential contribution is largely unknown (Lewkowicz, 1991). The recycling of carbon is a potentially important positive climate change feedback.…”

Human Land-Use and Soil Change

“…The active layer and upper permafrost can contain large quantities of organic C compared to soils in temperate ecosystems as a result of frost churning (Bockheim et al 1999;Ping et al 1997;Ping 2013;Tarnocai 2009). In the subarctic, land-use change has been found to increase soil temperatures by 4-5°C, lengthen the season of biological activity by 2-3 weeks, and enhance plant residue decomposition by 25 % (Grünzweig et al 2003).…”