Holocene development and permafrost history in sub‐arctic peatlands in Tavvavuoma, northern Sweden

Abstract

Under changing climatic conditions permafrost peatlands can play an important role in the global carbon budget through permafrost carbon feedbacks and shifts in carbon assimilation. To better predict future dynamics in these ecosystems an increased understanding of their Holocene carbon and permafrost history is needed. In Tavvavuoma, northern Sweden, we have performed detailed analyses of vegetation succession and geochemical properties at six permafrost peatland sites. Peatland initiation took place around 10 000 to 9600 cal. a BP, soon after retreat of the Fennoscandian Ice Sheet, and the peatlands have remained permafrost‐free fens throughout most of the Holocene. At the four sites that showed a continuous accumulation record during the late Holocene radiocarbon dating of the shift from wet fen to dry bog vegetation, characteristic of the present permafrost peatland surface, suggests that permafrost developed at around 600–100 cal. a BP. At the other two sites peat accumulation was halted during the late Holocene, possibly due to abrasion, making it more difficult to imply the timing of permafrost aggradation. However also at these sites there are no indications of permafrost inception prior to the Little Ice Age. The mean long‐term Holocene carbon accumulation rate at all six sites was 12.3±2.4 gC m−2 a−1 (±SD), and the mean soil organic carbon storage was 114±27 kg m−2.

Inconsistent Response of Arctic Permafrost Peatland Carbon Accumulation to Warm Climate Phases

“…During these periods peat accumulation rates were as low as 2 × 10 −5 m 2 /year. Moreover, a long‐term hiatus in the accumulation record may occur, as has been detected in the age‐depth model of Sei2 (see also Routh et al, ; Sannel et al, ). In addition, the very low CARs, when followed by thaw, could also be the results of peat decomposition of the formerly frozen peat layers upon thaw (see Jones et al, ; O'Donnell et al, ).…”

Ground temperature and snow depth variability within a subarctic peat plateau landscape

“…Permafrost did not develop in these wetlands until during the Little Ice Age ~600–100 cal yr BP . Within the peat plateau complex, peat depth varies from around 0.5 to >2 m. The mean SOC content in the organic layer is ~114 kg Cm −2 , and in the permafrost the wet‐basis gravimetric ice content is >77% . At present, the active layer depth in the peat plateau is around 55–60 cm, and the mean annual ground temperature (MAGT) is above −0.3°C and has increased by 0.06°C/yr between 2006 and 2013 .…”

“…The peat is underlain by glaciofluvial and lacustrine sediments . Peat formation at the site started soon after deglaciation of the Fennoscandian Ice Sheet ~10,000 cal yr BP . Permafrost did not develop in these wetlands until during the Little Ice Age ~600–100 cal yr BP .…”

“…Peat formation at the site started soon after deglaciation of the Fennoscandian Ice Sheet ~10,000 cal yr BP . Permafrost did not develop in these wetlands until during the Little Ice Age ~600–100 cal yr BP . Within the peat plateau complex, peat depth varies from around 0.5 to >2 m. The mean SOC content in the organic layer is ~114 kg Cm −2 , and in the permafrost the wet‐basis gravimetric ice content is >77% .…”

Indicator value of oribatid mites in determining past permafrost dynamics in northern European sub‐Arctic peatlands

“…; Sannel et al . ). These analyses are based on rapid shifts in typical plant/moss assemblages and the absence of certain species, which never occur on permafrost (Oksanen ).…”