Estimated stocks of circumpolar permafrost carbon with quantifieduncertainty ranges and identified data gaps

[摘要] Soils and other unconsolidated deposits in the northern circumpolarpermafrost region store large amounts of soil organic carbon (SOC). This SOCis potentially vulnerable to remobilization following soil warming andpermafrost thaw, but SOC stock estimates were poorly constrained andquantitative error estimates were lacking. This study presents revisedestimates of permafrost SOC stocks, including quantitative uncertaintyestimates, in the 0–3 m depth range in soils as well as for sedimentsdeeper than 3 m in deltaic deposits of major rivers and in the Yedoma regionof Siberia and Alaska. Revised estimates are based on significantly largerdatabases compared to previous studies. Despite this there is evidence ofsignificant remaining regional data gaps. Estimates remain particularlypoorly constrained for soils in the High Arctic region and physiographicregions with thin sedimentary overburden (mountains, highlands and plateaus)as well as for deposits below 3 m depth in deltas and the Yedoma region.While some components of the revised SOC stocks are similar in magnitude tothose previously reported for this region, there are substantial differencesin other components, including the fraction of perennially frozen SOC.Upscaled based on regional soil maps, estimated permafrost region SOC stocksare 217 ± 12 and 472 ± 27 Pg for the 0–0.3 and 0–1 m soildepths, respectively (±95% confidence intervals). Storage of SOC in0–3 m of soils is estimated to 1035 ± 150 Pg. Of this, 34 ±16 Pg C is stored in poorly developed soils of the High Arctic.Based on generalized calculations, storage of SOC below 3 m of surface soilsin deltaic alluvium of major Arctic rivers is estimated as 91 ±52 Pg. In the Yedoma region, estimated SOC stocks below 3 m depthare 181 ± 54 Pg, of which 74 ± 20 Pg is stored inintact Yedoma (late Pleistocene ice- and organic-rich silty sediments) withthe remainder in refrozen thermokarst deposits. Total estimated SOC storagefor the permafrost region is ∼1300 Pg with an uncertainty rangeof ∼1100 to 1500 Pg. Of this, ∼500 Pg is innon-permafrost soils, seasonally thawed in the active layer or in deepertaliks, while ∼800 Pg is perennially frozen. This represents asubstantial ∼300 Pg lowering of the estimated perenniallyfrozen SOC stock compared to previous estimates.

[学科分类] 地球化学与岩石