| 1. |
- Biskaborn, Boris K., et al.
(författare)
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Permafrost is warming at a global scale
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Permafrost to evaluate temperature change across permafrost regions for the period since the International Polar Year (2007–2009). During the reference decade between 2007 and 2016, ground temperature near the depth of zero annual amplitude in the continuous permafrost zone increased by 0.39 ± 0.15 °C. Over the same period, discontinuous permafrost warmed by 0.20 ± 0.10 °C. Permafrost in mountains warmed by 0.19 ± 0.05 °C and in Antarctica by 0.37 ± 0.10 °C. Globally, permafrost temperature increased by 0.29 ± 0.12 °C. The observed trend follows the Arctic amplification of air temperature increase in the Northern Hemisphere. In the discontinuous zone, however, ground warming occurred due to increased snow thickness while air temperature remained statistically unchanged.
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| 2. |
- Hugelius, Gustaf, 1980-, et al.
(författare)
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Estimating soil organic carbon storage in periglacial terrain at very high resolution; a case study from the European Russian Arctic
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 1 Introduction While recent research advances have significantly increased our understanding of SOC storage in the periglacial landscape, there are still many uncertainties. Local scale studies have shown that the landscape distribution of SOC is highly heterogeneous (e.g. Hugelius and Kuhry, 2009). Some landscape components, such as peat deposits or cryoturbated soil horizons, can dominate local SOC storage. However, there are no clear trends in landscape distribution and regional differences emerge (Kuhry et al., in prep.). We have conducted a very high resolution study of SOC storage in four study sites (Seida and Rogovaya 1-3) in discontinuous permafrost terrain, European Russian Arctic. Point pedon data is upscaled to areal coverage using two different upscaling tools, land cover classifications and soil maps. 2 Methods 2.1 Soil sampling and upscaling Soil sampling was performed (i) along landscape transects and (ii) according to a weighted, stratified random sampling program. Sampling was done in 10 cm increments to 1 m depth or to full depth of peat deposits in a total of 94 sites. Point pedon data is upscaled to areal coverage using two different upscaling tools: 1. Thematic land cover classifications based on multiresolution segmentation of high-resolution Quickbird imagery (2.44 m raster resolution, 17 separate land cover classes, software Definiens Professional 5.0) and: 2. High resolution thematic soil maps following World Reference Base for Soil Resources terminology (20 distinct soil types, median polygon size 1960 m2). Mean SOC storage for each land cover or soil type is multiplied by the areal coverage within the study areas to calculate total storage and landscape partitioning of SOC. Figure 1 illustrates the spatial resolution of the two upscaling tools. It also shows 4 pixels of Landsat TM resolution, representing the highest resolution of previous land cover based SOC storage studies in permafrost terrain. 3 results Preliminary calculations show that the estimates in the four different areas are between 38-58 kg C m-2 for land cover upscaling and between 37-49 kg C m-2 for soil map upscaling. Both upscaling methods yield higher estimates than what has previously been reported for this area (Hugelius and Kuhry, 2009). A majority of SOC is stored in Cryic Histosols or Folic/Histic Cryosols. Contiguous permafrost peat plateaus are present in all study areas, covering ~20-30 % of the landscape. The mean depth of peat deposits in the four plateaus is between 150-250 cm, but it is highly variable (recorded range 30-420 cm). There is no evidence of any significant deep burial of SOC through cryoturbation processes. References Hugelius G. and Kuhry P. 2009, Landscape partitioning and environmental gradient analyses of soil organic carbon in a permafrost environment. Global Biogeochemical Cycles, 23, GB3006, doi:10.1029/2008GB003419. Kuhry, P., Dorrepaal, E., Hugelius G., Schuur, E.A.G. and Tarnocai C., Potential remobilization of permafrost carbon under future global warming. Permafrost and Periglacial Processes, Submitted.
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| 3. |
- Hugelius, Gustaf, et al.
(författare)
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High-resolution mapping of ecosystem carbon storage and potential effects of permafrost thaw in periglacial terrain, European Russian Arctic
- 2011
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 116, s. G03024-
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Tidskriftsartikel (refereegranskat)abstract
- This study describes detailed partitioning of phytomass carbon (C) and soil organic carbon (SOC) for four study areas in discontinuous permafrost terrain, Northeast European Russia. The mean aboveground phytomass C storage is 0.7 kg C m(-2). Estimated landscape SOC storage in the four areas varies between 34.5 and 47.0 kg C m(-2) with LCC (land cover classification) upscaling and 32.5-49.0 kg C m(-2) with soil map upscaling. A nested upscaling approach using a Landsat thematic mapper land cover classification for the surrounding region provides estimates within 5 +/- 5% of the local high-resolution estimates. Permafrost peat plateaus hold the majority of total and frozen SOC, especially in the more southern study areas. Burying of SOC through cryoturbation of O- or A-horizons contributes between 1% and 16% (mean 5%) of total landscape SOC. The effect of active layer deepening and thermokarst expansion on SOC remobilization is modeled for one of the four areas. The active layer thickness dynamics from 1980 to 2099 is modeled using a transient spatially distributed permafrost model and lateral expansion of peat plateau thermokarst lakes is simulated using geographic information system analyses. Active layer deepening is expected to increase the proportion of SOC affected by seasonal thawing from 29% to 58%. A lateral expansion of 30 m would increase the amount of SOC stored in thermokarst lakes/fens from 2% to 22% of all SOC. By the end of this century, active layer deepening will likely affect more SOC than thermokarst expansion, but the SOC stores vulnerable to thermokarst are less decomposed.
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| 4. |
- Treat, Claire C., et al.
(författare)
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Tundra landscape heterogeneity, not interannual variability, controls the decadal regional carbon balance in the Western Russian Arctic
- 2018
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 24:11, s. 5188-5204
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Tidskriftsartikel (refereegranskat)abstract
- Across the Arctic, the net ecosystem carbon (C) balance of tundra ecosystems is highly uncertain due to substantial temporal variability of C fluxes and to landscape heterogeneity. We modeled both carbon dioxide (CO2) and methane (CH4) fluxes for the dominant land cover types in a similar to 100-km(2) sub-Arctic tundra region in northeast European Russia for the period of 2006-2015 using process-based biogeochemical models. Modeled net annual CO2 fluxes ranged from --300 g C m(-2) year(-1) [net uptake] in a willow fen to 3 g Cm-2 year(-1) [net source] in dry lichen tundra. Modeled annual CH4 emissions ranged from -0.2 to 22.3 g Cm-2 year(-1) at a peat plateau site and a willow fen site, respectively. Interannual variability over the decade was relatively small (20%-25%) in comparison with variability among the land cover types (150%). Using high-resolution land cover classification, the region was a net sink of atmospheric CO2 across most land cover types but a net source of CH4 to the atmosphere due to high emissions from permafrost-free fens. Using a lower resolution for land cover classification resulted in a 20%-65% underestimation of regional CH4 flux relative to high-resolution classification and smaller (10%) overestimation of regional CO2 uptake due to the underestimation of wetland area by 60%. The relative fraction of uplands versus wetlands was key to determining the net regional C balance at this and other Arctic tundra sites because wetlands were hot spots for C cycling in Arctic tundra ecosystems.
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| 5. |
- Väliranta, Minna, et al.
(författare)
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Warming climate forcing impact from a sub-arctic peatland as a result of late Holocene permafrost aggradation and initiation of bare peat surfaces
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 264
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Tidskriftsartikel (refereegranskat)abstract
- Effects of permafrost aggradation on greenhouse gas (GHG) dynamics and climate forcing have not been previously quantified. Here, we reconstruct changes in GHG balances over the late Holocene for a sub-arctic peatland by applying palaeoecological data combined with measured GHG flux data, focusing on the impact of permafrost aggradation in particular. Our data suggest that permafrost initiation around 3000 years ago resulted in GHG emissions, thereby slightly weakening the general long-term peatland cooling impact. As a novel discovery, based on our chronological data of bare peat surfaces, we found that current sporadic bare peat surfaces in subarctic regions are probably remnants of more extensive bare peat areas formed by permafrost initiation. Paradoxically, our data suggest that permafrost initiation triggered by the late Holocene cooling climate generated a positive radiative forcing and a short-term climate warming feedback, mitigating the general insolation-driven late Holocene summer cooling trend. Our work with historical data demonstrates the importance of permafrost peatland dynamics for atmospheric GHG concentrations, both in the past and future. It suggests that, while thawing permafrost is likely to initially trigger a change towards wetter conditions and consequent increase in CH4 forcing, eventually the accelerated C uptake capacity under warmer climate may overcome the thaw effect when a new hydrological balance becomes established.
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