Patterns and persistence of hydrologic carbon and nutrient export from collapsing upland permafrost

[摘要] As high latitudes warm, vast stocks of carbon and nitrogen stored inpermafrost will become available for transport to aquatic ecosystems. Whilethere is a growing understanding of the potential effects of permafrostcollapse (thermokarst) on aquatic biogeochemical cycles, neither the spatialextent nor temporal duration of these effects is known. To test hypothesesconcerning patterns and persistence of elemental export from uplandthermokarst, we sampled hydrologic outflow from 83 thermokarst features invarious stages of development across the North Slope of Alaska. Wehypothesized that an initial pulse of carbon and nutrients would be followedby a period of elemental retention during feature recovery, and that theduration of these stages would depend on feature morphology. Thermokarstcaused substantial increases in dissolved organic carbon and other soluteconcentrations with a particularly large impact on inorganic nitrogen.Magnitude and duration of thermokarst effects on water chemistry differed byfeature type and secondarily by landscape age. Most solutes returned toundisturbed concentrations after feature stabilization, but elevateddissolved carbon, inorganic nitrogen, and sulfate concentrations persistedthrough stabilization for some feature types, suggesting that aquaticdisturbance by thermokarst for these solutes is long-lived. Dissolvedmethane decreased by 90% for most feature types, potentially due to highconcentrations of sulfate and inorganic nitrogen. Spatial patterns of carbonand nutrient export from thermokarst suggest that upland thermokarst may bea dominant linkage transferring carbon and nutrients from terrestrial toaquatic ecosystems as the Arctic warms.

[学科分类] 地球化学与岩石