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Dissolved organic carbon (DOC) from massive ground ice along the Yukon coast - Why does it matter?

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Citation:
Fritz, M. , Lantuit, H. , Couture, N. J. and Pollard, W. H. (2010): Dissolved organic carbon (DOC) from massive ground ice along the Yukon coast - Why does it matter? , ArcticNet Annual Scientific Meeting (ASM 2010), Ottawa, Canada, 14 December 2010 - 17 December 2010 .
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Abstract:

Permafrost soils are known to hold around 50% of the global soil carbon pool, mostly as particulate organic carbon (POC). The carbon is often stored deep in the soil profile, because of its redistribution through cryoturbation or simply because of the nature of the depositional processes that led to the storage of carbon in these lower horizons. Soils are rarely wholly vertically exposed, because of the progressive nature of thaw processes, except in thermokarst, river shores and coastlines, where large vertical sections of ice-rich permafrost can be in contact with both the sea and the atmosphere. As arctic permafrost coasts make up 34 % of the world’s coastline (ca. 400,000 km) and are often made of ice-rich unconsolidated sediments highly susceptible to coastal erosion as shown by the large rates of erosion recently reported in the literature, it is likely that large quantities of carbon are released from coastal erosion. Current estimates of carbon release by coastal erosion focus solely on particulate organic carbon, emphasizing the overwhelming role of the soil POC in the overall release of total organic carbon from erosion. Dissolved Organic Carbon (DOC) is generally not included in these estimates, as it is considered to be negligible in the equation. Estimations of DOC contents in ground ice, which is overwhelmingly present along arctic coasts do not exist though and this study aimed at investigating DOC contents in massive ice. Along the Yukon Coastal Plain, in the Western Canadian Arctic, massive ground ice bodies such as ice wedges, buried glacier ice, and segregated massive ice form an overwhelming component of the coastal sections. In some cases, virtually pure ground ice occupies as much as 90% of 40 m coastal exposures and erodes at rates approaching 10 m/yr. Here we present the first results of dissolved organic carbon from massive ground ice from Herschel Island (69.583 °N; 139.083 °W) in the Southern Beaufort Sea. First data suggest that Holocene ice wedges possess the highest DOC content of all massive ice types. Buried glacier ice, basal regelation ice or segregation ice show strong internal variation due to their complex interaction with host sediments and their parent organic carbon content. We draw from these results some numbers showing the relevance of DOC in computing sediment budgets for large areas and for the Arctic. We highlight the need to collect samples from a range of exposures affected by other cryogenic processes to get a comprehensive picture of DOC contents in ground ice along arctic coasts.

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