Geophysical mapping of palsa peatland permafrost

Sjöberg, Ylva; Marklund, Per; Pettersson, R.; Lyon, Steve W.

doi:10.5194/tc-9-465-2015

Cited by 62 publications

(57 citation statements)

References 45 publications

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“…10 m, e.g. small drainages and depressions with or without ponds, are ignored in the delineation process, as they are likely to be still underlain by permafrost (Sjöberg et al, 2015).…”

Section: Methodology and Datamentioning

confidence: 99%

“…In contrast, the interior of palsas and peat plateaus can also experience thaw subsidence, resulting in thermokarst depressions and suprapermafrost taliks, as seen for peat plateaus in northern Sweden (Åkerman and Johansson, 2008;Sjöberg et al, 2015). Based on calculated thaw rates and an instant increase in air temperature of 2 • C, Sjöberg et al (2015) estimated that it will take 175-260 years for the permafrost at their investigated peat plateaus to completely thaw.…”

Section: Degradation Of Palsas and Peat Plateaus Through Lateral Erosionmentioning

confidence: 99%

“…Based on calculated thaw rates and an instant increase in air temperature of 2 • C, Sjöberg et al (2015) estimated that it will take 175-260 years for the permafrost at their investigated peat plateaus to completely thaw. However, much more rapid degradation has been observed in the same region (Zuidhoff, 2002), which could be an indication that lateral erosion considerably increases the degradation rates.…”

Section: Degradation Of Palsas and Peat Plateaus Through Lateral Erosionmentioning

confidence: 99%

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Strong degradation of palsas and peat plateaus in northern Norway during the last 60 years

et al. 2017

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Abstract. Palsas and peat plateaus are permafrost landforms occurring in subarctic mires which constitute sensitive ecosystems with strong significance for vegetation, wildlife, hydrology and carbon cycle. Firstly, we have systematically mapped the occurrence of palsas and peat plateaus in the northernmost county of Norway (Finnmark, ∼ 50 000 km 2 ) by manual interpretation of aerial images from 2005 to 2014 at a spatial resolution of 250 m. At this resolution, mires and wetlands with palsas or peat plateaus occur in about 850 km 2 of Finnmark, with the actual palsas and peat plateaus underlain by permafrost covering a surface area of approximately 110 km 2 . Secondly, we have quantified the lateral changes of the extent of palsas and peat plateaus for four study areas located along a NW-SE transect through Finnmark by utilizing repeat aerial imagery from the 1950s to the 2010s. The results of the lateral changes reveal a total decrease of 33-71 % in the areal extent of palsas and peat plateaus during the study period, with the largest lateral change rates observed in the last decade. However, the results indicate that degradation of palsas and peat plateaus in northern Norway has been a consistent process during the second half of the 20th century and possibly even earlier. Significant rates of areal change are observed in all investigated time periods since the 1950s, and thermokarst landforms observed on aerial images from the 1950s suggest that lateral degradation was already an ongoing process at this time. The results of this study show that lateral erosion of palsas and peat plateaus is an important pathway for permafrost degradation in the sporadic permafrost zone in northern Scandinavia. While the environmental factors governing the rate of erosion are not yet fully understood, we note a moderate increase in air temperature, precipitation and snow depth during the last few decades in the region.

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“…10 m, e.g. small drainages and depressions with or without ponds, are ignored in the delineation process, as they are likely to be still underlain by permafrost (Sjöberg et al, 2015).…”

Section: Methodology and Datamentioning

confidence: 99%

Section: Degradation Of Palsas and Peat Plateaus Through Lateral Erosionmentioning

confidence: 99%

Section: Degradation Of Palsas and Peat Plateaus Through Lateral Erosionmentioning

confidence: 99%

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Strong degradation of palsas and peat plateaus in northern Norway during the last 60 years

et al. 2017

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“…More recent attempts have also incorporated ground-based remote sensing, such as ground-penetrating radar (GPR) and electrical resistivity measurements, but only over limited local extents (Sjöberg et al, 2015;Jorgenson and Grosse, 2016). Several studies have used empirical models driven by in situ ground observations and other geospatial datasets to provide fine-scale (< 100 m resolution) estimates of active layer and near-surface permafrost conditions (Mishra and Riley, 2014;Pastick et al, 2015).…”

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confidence: 99%

Characterizing permafrost active layer dynamics and sensitivity to landscape spatial heterogeneity in Alaska

Kimball

Chen

et al. 2018

The Cryosphere

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Abstract. An important feature of the Arctic is large spatial heterogeneity in active layer conditions, which is generally poorly represented by global models and can lead to large uncertainties in predicting regional ecosystem responses and climate feedbacks. In this study, we developed a spatially integrated modeling and analysis framework combining field observations, local-scale ( ∼ 50 m resolution) active layer thickness (ALT) and soil moisture maps derived from low-frequency (L + P-band) airborne radar measurements, and global satellite environmental observations to investigate the ALT sensitivity to recent climate trends and landscape heterogeneity in Alaska. Modeled ALT results show good correspondence with in situ measurements in higherpermafrost-probability (PP ≥ 70 %) areas (n = 33; R = 0.60; mean bias = 1.58 cm; RMSE = 20.32 cm), but with larger uncertainty in sporadic and discontinuous permafrost areas. The model results also reveal widespread ALT deepening since 2001, with smaller ALT increases in northern Alaska (mean trend = 0.32 ± 1.18 cm yr −1 ) and much larger increases (> 3 cm yr −1 ) across interior and southern Alaska. The positive ALT trend coincides with regional warming and a longer snow-free season (R = 0.60 ± 0.32). A spatially integrated analysis of the radar retrievals and model sensitivity simulations demonstrated that uncertainty in the spatial and vertical distribution of soil organic carbon (SOC) was the largest factor affecting modeled ALT accuracy, while soil moisture played a secondary role. Potential improvements in characterizing SOC heterogeneity, including better spatial sampling of soil conditions and advances in remote sensing of SOC and soil moisture, will enable more accurate predictions of active layer conditions and refinement of the modeling framework across a larger domain.

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“…To date, most field-based studies of changes in peatland permafrost have focused on the sporadic and extensive discontinuous zones (e.g. Halsey et al, 1995;James et al, 2013;Kwong and Gan, 1994;Sjöberg et al, 2015;Swindles et al, 2016;Thibault and Payette, 2009). A better understanding of the 10 current distribution and characteristics of isolated bodies of permafrost is needed to assess the likelihood of their persistence or degradation in the face of climate warming.…”

Section: Introductionmentioning

confidence: 99%

Characteristics and fate of isolated permafrost patches in coastal Labrador, Canada

Way¹,

Lewkowicz²,

Yu³

2018

Preprint

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Abstract. Bodies of peatland permafrost were examined at five sites along a 300 km transect spanning the isolated patches permafrost zone in the coastal barrens of southeastern Labrador. Mean annual air temperatures ranged from +1°C in the south (latitude 51.4°N) to -1.1°C in the north (53.7°N) while mean ground temperatures at the top of permafrost varied 10 respectively from -0.7°C to -2.3°C with shallow active layers (40-60 cm) throughout. Small surface offsets due to wind scouring of snow from the crests of palsas and peat plateaux, and large thermal offsets due to thick peat are critical to permafrost, which is therefore absent in wetland, forested and forest-tundra areas inland, notwithstanding average air temperatures much lower than near the coast. Most permafrost peatland bodies are less than 5 m thick with a maximum of 10 m with steep geothermal gradients. One-dimensional thermal modelling for two sites showed that they are in equilibrium 15 with the current climate, but the permafrost mounds are generally relict and could not form today without the low snow depths that result from a heaved peat surface. Despite the warm permafrost, model predictions using downscaled global warming scenarios (RCP2.6, 4.5 and 8.5) indicate that perennially frozen ground will thaw from the base up and may persist at the southern site until the middle of the 21 st Century. At the northern site, permafrost is more resilient, persisting to the 2060s under RCP8.5, the 2090s under RCP4.5, or beyond the 21 st century under RCP2.6. Despite evidence of peatland 20 permafrost degradation in the study region, the local-scale modelling suggests that the southern boundary of permafrost may not move as quickly as had previously been thought.

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Geophysical mapping of palsa peatland permafrost

Cited by 62 publications

References 45 publications

Strong degradation of palsas and peat plateaus in northern Norway during the last 60 years

Strong degradation of palsas and peat plateaus in northern Norway during the last 60 years

Characterizing permafrost active layer dynamics and sensitivity to landscape spatial heterogeneity in Alaska

Characteristics and fate of isolated permafrost patches in coastal Labrador, Canada

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