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  • 1. Abbott, Benjamin W.
    et al.
    Jones, Jeremy B.
    Schuur, Edward A. G.
    Chapin, F. Stuart
    Bowden, William B.
    Bret-Harte, M. Syndonia
    Epstein, Howard E.
    Flannigan, Michael D.
    Harms, Tamara K.
    Hollingsworth, Teresa N.
    Mack, Michelle C.
    McGuire, A. David
    Natali, Susan M.
    Rocha, Adrian V.
    Tank, Suzanne E.
    Turetsky, Merritt R.
    Vonk, Jorien E.
    Wickland, Kimberly P.
    Aiken, George R.
    Alexander, Heather D.
    Amon, Rainer M. W.
    Benscoter, Brian W.
    Bergeron, Yves
    Bishop, Kevin
    Blarquez, Olivier
    Bond-Lamberty, Ben
    Breen, Amy L.
    Buffam, Ishi
    Cai, Yihua
    Carcaillet, Christopher
    Carey, Sean K.
    Chen, Jing M.
    Chen, Han Y. H.
    Christensen, Torben R.
    Cooper, Lee W.
    Cornelissen, J. Hans C.
    de Groot, William J.
    DeLuca, Thomas H.
    Dorrepaal, Ellen
    Fetcher, Ned
    Finlay, Jacques C.
    Forbes, Bruce C.
    French, Nancy H. F.
    Gauthier, Sylvie
    Girardin, Martin P.
    Goetz, Scott J.
    Goldammer, Johann G.
    Gough, Laura
    Grogan, Paul
    Guo, Laodong
    Higuera, Philip E.
    Hinzman, Larry
    Hu, Feng Sheng
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jafarov, Elchin E.
    Jandt, Randi
    Johnstone, Jill F.
    Karlsson, Jan
    Kasischke, Eric S.
    Kattner, Gerhard
    Kelly, Ryan
    Keuper, Frida
    Kling, George W.
    Kortelainen, Pirkko
    Kouki, Jari
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Laudon, Hjalmar
    Laurion, Isabelle
    Macdonald, Robie W.
    Mann, Paul J.
    Martikainen, Pertti J.
    McClelland, James W.
    Molau, Ulf
    Oberbauer, Steven F.
    Olefeldt, David
    Pare, David
    Parisien, Marc-Andre
    Payette, Serge
    Peng, Changhui
    Pokrovsky, Oleg S.
    Rastetter, Edward B.
    Raymond, Peter A.
    Raynolds, Martha K.
    Rein, Guillermo
    Reynolds, James F.
    Robards, Martin
    Rogers, Brendan M.
    Schaedel, Christina
    Schaefer, Kevin
    Schmidt, Inger K.
    Shvidenko, Anatoly
    Sky, Jasper
    Spencer, Robert G. M.
    Starr, Gregory
    Striegl, Robert G.
    Teisserenc, Roman
    Tranvik, Lars J.
    Virtanen, Tarmo
    Welker, Jeffrey M.
    Zimov, Sergei
    Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: an expert assessment2016In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 11, no 3, article id 034014Article in journal (Refereed)
    Abstract [en]

    As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.

  • 2. Alfredsson, H.
    et al.
    Clymans, W.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Conley, D. J.
    Estimated storage of amorphous silica in soils of the circum-Arctic tundra region2016In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 30, no 3, p. 479-500Article in journal (Refereed)
    Abstract [en]

    We investigated the vertical distribution, storage, landscape partitioning, and spatial variability of soil amorphous silica (ASi) at four different sites underlain by continuous permafrost and representative of mountainous and lowland tundra, in the circum-Arctic region. Based on a larger set of data, we present the first estimate of the ASi soil reservoir (0-1m depth) in circum-Arctic tundra terrain. At all sites, the vertical distribution of ASi concentrations followed the pattern of either (1) declining concentrations with depth (most common) or (2) increasing/maximum concentrations with depth. Our results suggest that a set of processes, including biological control, solifluction and other slope processes, cryoturbation, and formation of inorganic precipitates influence vertical distributions of ASi in permafrost terrain, with the capacity to retain stored ASi on millennial timescales. At the four study sites, areal ASi storage (0-1m) is generally higher in graminoid tundra compared to wetlands. Our circum-Arctic upscaling estimates, based on both vegetation and soil classification separately, suggest a storage amounting to 219 +/- 28 and 274 +/- 33 Tmol Si, respectively, of which at least 30% is stored in permafrost. This estimate would account for about 3% of the global soil ASi storage while occupying an equal portion of the global land area. This result does not support the hypothesis that the circum-Arctic tundra soil ASi reservoir contains relatively higher amounts of ASi than other biomes globally as demonstrated for carbon. Nevertheless, climate warming has the potential to significantly alter ASi storage and terrestrial Si cycling in the Arctic.

  • 3. Alfredsson, Hanna
    et al.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Clymans, Wim
    Stadmark, Johanna
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Conley, Daniel J.
    Amorphous silica pools in permafrost soils of the Central Canadian Arctic and the potential impact of climate change2015In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 124, no 1-3, p. 441-459Article in journal (Refereed)
    Abstract [en]

    We investigated the distribution, storage and landscape partitioning of soil amorphous silica (ASi) in a central Canadian region dominated by tundra and peatlands to provide a first estimate of the amount of ASi stored in Arctic permafrost ecosystems. We hypothesize that, similar to soil organic matter, Arctic soils store large amounts of ASi which may be affected by projected climate changes and associated changes in permafrost regimes. Average soil ASi storage (top 1 m) ranged between 9600 and 83,500 kg SiO2 ha(-1) among different land-cover types. Lichen tundra contained the lowest amounts of ASi while no significant differences were found in ASi storage among other land-cover types. Clear differences were observed between ASi storage allocated into the top organic versus the mineral horizon of soils. Bog peatlands, fen peatlands and wet shrub tundra stored between 7090 and 45,400 kg SiO2 ha(-1) in the top organic horizon, while the corresponding storage in lichen tundra, moist shrub- and dry shrub tundra only amounted to 1500-1760 kg SiO2 ha(-1). Diatoms and phytoliths are important components of ASi storage in the top organic horizon of peatlands and shrub tundra systems, while it appears to be a negligible component of ASi storage in the mineral horizon of shrub tundra classes. ASi concentrations decrease with depth in the soil profile for fen peatlands and all shrub tundra classes, suggesting recycling of ASi, whereas bog peatlands appeared to act as sinks retaining stored ASi on millennial time scales. Our results provide a conceptual framework to assess the potential effects of climate change impacts on terrestrial Si cycling in the Arctic. We believe that ASi stored in peatlands are particularly sensitive to climate change, because a larger fraction of the ASi pool is stored in perennially frozen ground compared to shrub tundra systems. A likely outcome of climate warming and permafrost thaw could be mobilization of previously frozen ASi, altered soil storage of biogenically derived ASi and an increased Si flux to the Arctic Ocean.

  • 4.
    Andersson, Rina Argelia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Meyers, Philip
    Department of Earth and Environmental Sciences, The University of Michigan, Ann Arbor, Michigan, U.S.A..
    Zebür, Yngve
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Crill, Patrick
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Impacts of paleohydrological changes on n-alkane biomarker compositions of a Holocene peat sequence in the eastern European Russian Arctic2011In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 42, no 9, p. 1065-1075Article in journal (Refereed)
    Abstract [en]

    Coupled analyses of n-alkane biomarkers and plant macrofossils from a peat plateau deposit in the northeast European Russian Arctic were carried out to assess the effects of past hydrology on the molecular contributions of plants to the peat. The n-alkane biomarkers accumulated over 9.6 kyr of local paleohydrological changes in this complex peat profile in which a succession of vegetation changes occurred during a transition from a wet fen to a relatively dry peat plateau bog. This study shows that the contribution of the n-C31 alkane from rootlets to peat layers rich in fine and dark roots is important. The results further indicate that the n-alkanePaqandn-C23/n-C29 biomarker proxies that have been useful to reconstruct past water table levels in many peat deposits can be misleading when the contributions of Betulaand Sphagnum fuscum to the peat are large. Under these conditions, the C23/(C27+ C31) n-alkane ratio seems to correct for the presence of BetulaandS. fuscum and provides a better description for the relative amounts of moisture. The average chain length (ACL) n-alkane proxy also appears to be a good paleohydrology proxy in having larger values during dry and cold conditions in this Arctic bog setting.

  • 5.
    Andersson, Rina Argelia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meyers, Philip
    Hornibrook, Edward
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Morth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Elemental and isotopic carbon and nitrogen records of organic matter accumulation in a Holocene permafrost peat sequence in the East European Russian Arctic2012In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 27, no 6, p. 545-552Article in journal (Refereed)
    Abstract [en]

    A peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (similar to 2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss-dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water-saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. delta 15N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in delta 13C values appear to reflect mainly changes in plant assemblages. Positive shifts in both delta 15N and delta 13C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed 15N-enrichment.

  • 6.
    Andersson, Rina Argelia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meyers, Philip
    Department of Earth and Environmental Sciences, The University of Michigan, Ann Arbor, Michigan, U.S.A..
    Hornibrook, Edward
    Bristol Biogeochemistry Research Centre & Cabot Institute, School of Earth Sciences, University of Bristol, Queens Road, Bristol BS8 1RJ, United Kingdom.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Mörth, Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Elemental and isotopic carbon and itrogen records of organic matter accumulation in a Holocene permafrots peat sequence in the East European Russian ArcticManuscript (preprint) (Other academic)
    Abstract [en]

    A peat deposit from the East European Russian Arctic, spanning nearly 10,000 years, was investigated to reconstruct past environmental conditions and to study soil organic matter (SOM) degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (~2,500 cal a BP). Total organic carbon (TOC) and total nitrogen (N) concentrations are different in the bog peat compared to the fen peat, with lower values in the moss-dominated bog peat layers.  Lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues.  The atomic ratios of bulk elemental parameters indicate better preservation of organic matter in peat deposits dominated by bryophytes relative to vascular plants.  The presence of permafrost in the peat plateau stage and water-saturated conditions at the bottom of the fen stage appear to be associated with better preservation of organic plant material.  δ15N values suggest N isotopic fractionation was driven primarily by microbial decomposition while differences in δ13C values appear to be associated mainly with changes in plant assemblages rather than diagenesis.  Positive shifts in both δ15N and δ13C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface.  This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed 15N-enrichment.

  • 7. Bartsch, Annett
    et al.
    Widhalm, Barbara
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Siewert, Matthias Benjamin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Can C-band synthetic aperture radar be used to estimate soil organic carbon storage in tundra?2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 19, p. 5453-5470Article in journal (Refereed)
    Abstract [en]

    A new approach for the estimation of soil organic carbon (SOC) pools north of the tree line has been developed based on synthetic aperture radar (SAR; ENVISAT Advanced SAR Global Monitoring mode) data. SOC values are directly determined from backscatter values instead of upscaling using land cover or soil classes. The multi-mode capability of SAR allows application across scales. It can be shown that measurements in C band under frozen conditions represent vegetation and surface structure properties which relate to soil properties, specifically SOC. It is estimated that at least 29 Pg C is stored in the upper 30 cm of soils north of the tree line. This is approximately 25% less than stocks derived from the soil-map-based Northern Circumpolar Soil Carbon Database (NCSCD). The total stored carbon is underestimated since the established empirical relationship is not valid for peatlands or strongly cryoturbated soils. The approach does, however, provide the first spatially consistent account of soil organic carbon across the Arctic. Furthermore, it could be shown that values obtained from 1 km resolution SAR correspond to accounts based on a high spatial resolution (2 m) land cover map over a study area of about 7 x 7 km in NE Siberia. The approach can be also potentially transferred to medium-resolution C-band SAR data such as ENVISAT ASAR Wide Swath with similar to 120m resolution but it is in general limited to regions without woody vegetation. Global Monitoring-mode-derived SOC increases with unfrozen period length. This indicates the importance of this parameter for modelling of the spatial distribution of soil organic carbon storage.

  • 8. Chadburn, Sarah E.
    et al.
    Krinner, Gerhard
    Porada, Philipp
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bartsch, Annett
    Beer, Christian
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Belelli Marchesini, Luca
    Boike, Julia
    Ekici, Altug
    Elberling, Bo
    Friborg, Thomas
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Johansson, Margareta
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kutzbach, Lars
    Langer, Moritz
    Lund, Magnus
    Parmentier, Frans-Jan W.
    Peng, Shushi
    Van Huissteden, Ko
    Wang, Tao
    Westermann, Sebastian
    Zhu, Dan
    Burke, Eleanor J.
    Carbon stocks and fluxes in the high latitudes: using site-level data to evaluate Earth system models2017In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 14, no 22, p. 5143-5169Article in journal (Refereed)
    Abstract [en]

    It is important that climate models can accurately simulate the terrestrial carbon cycle in the Arctic due to the large and potentially labile carbon stocks found in permafrost-affected environments, which can lead to a positive climate feedback, along with the possibility of future carbon sinks from northward expansion of vegetation under climate warming. Here we evaluate the simulation of tundra carbon stocks and fluxes in three land surface schemes that each form part of major Earth system models (JSBACH, Germany; JULES, UK; ORCHIDEE, France). We use a site-level approach in which comprehensive, high-frequency datasets allow us to disentangle the importance of different processes. The models have improved physical permafrost processes and there is a reasonable correspondence between the simulated and measured physical variables, including soil temperature, soil moisture and snow. We show that if the models simulate the correct leaf area index (LAI), the standard C3 photosynthesis schemes produce the correct order of magnitude of carbon fluxes. Therefore, simulating the correct LAI is one of the first priorities. LAI depends quite strongly on climatic variables alone, as we see by the fact that the dynamic vegetation model can simulate most of the differences in LAI between sites, based almost entirely on climate inputs. However, we also identify an influence from nutrient limitation as the LAI becomes too large at some of the more nutrient-limited sites. We conclude that including moss as well as vascular plants is of primary importance to the carbon budget, as moss contributes a large fraction to the seasonal CO2 flux in nutrient-limited conditions. Moss photosynthetic activity can be strongly influenced by the moisture content of moss, and the carbon uptake can be significantly different from vascular plants with a similar LAI. The soil carbon stocks depend strongly on the rate of input of carbon from the vegetation to the soil, and our analysis suggests that an improved simulation of photosynthesis would also lead to an improved simulation of soil carbon stocks. However, the stocks are also influenced by soil carbon burial (e.g. through cryoturbation) and the rate of heterotrophic respiration, which depends on the soil physical state. More detailed below-ground measurements are needed to fully evaluate biological and physical soil processes. Furthermore, even if these processes are well modelled, the soil carbon profiles cannot resemble peat layers as peat accumulation processes are not represented in the models. Thus, we identify three priority areas for model development: (1) dynamic vegetation including (a) climate and (b) nutrient limitation effects; (2) adding moss as a plant functional type; and an (3) improved vertical profile of soil carbon including peat processes.

  • 9. Faucherre, Samuel
    et al.
    Juncher Jørgensen, Christian
    Blok, Daan
    Weiss, Niels
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Siewert, Matthias Benjamin
    Stockholm University, Faculty of Science, Department of Physical Geography. Umeå University, Sweden.
    Bang-Andreasen, Toke
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Elberling, Bo
    Short and Long-Term Controls on Active Layer and Permafrost Carbon Turnover Across the Arctic2018In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 123, no 2, p. 372-390Article in journal (Refereed)
    Abstract [en]

    Decomposition of soil organic matter (SOM) in permafrost terrain and the production of greenhouse gases is a key factor for understanding climate change-carbon feedbacks. Previous studies have shown that SOM decomposition is mostly controlled by soil temperature, soil moisture, and carbon-nitrogen ratio (C:N). However, focus has generally been on site-specific processes and little is known about variations in the controls on SOM decomposition across Arctic sites. For assessing SOM decomposition, we retrieved 241 samples from 101 soil profiles across three contrasting Arctic regions and incubated them in the laboratory under aerobic conditions. We assessed soil carbon losses (C-loss) five times during a 1year incubation. The incubated material consisted of near-surface active layer (AL(NS)), subsurface active layer (AL(SS)), peat, and permafrost samples. Samples were analyzed for carbon, nitrogen, water content, C-13, N-15, and dry bulk density (DBD). While no significant differences were observed between total AL(SS) and permafrost C-loss over 1year incubation (2.32.4% and 2.51.5% C-loss, respectively), AL(NS) samples showed higher C-loss (7.94.2%). DBD was the best explanatory parameter for active layer C-loss across sites. Additionally, results of permafrost samples show that C:N ratio can be used to characterize initial C-loss between sites. This data set on the influence of abiotic parameter on microbial SOM decomposition can improve model simulations of Arctic soil CO2 production by providing representative mean values of CO2 production rates and identifying standard parameters or proxies for upscaling potential CO2 production from site to regional scales.

  • 10.
    Fuchs, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Low below-ground organic carbon storage in a subarctic Alpine permafrost environment2015In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 9, no 2, p. 427-438Article in journal (Refereed)
    Abstract [en]

    This study investigates the soil organic carbon (SOC) storage in Tarfala Valley, northern Sweden. Field inventories, upscaled based on land cover, show that this alpine permafrost environment does not store large amounts of SOC, with an estimate mean of 0.9 +/- 0.2 kg C m(-2) for the upper meter of soil. This is 1 to 2 orders of magnitude lower than what has been reported for lowland permafrost terrain. The SOC storage varies for different land cover classes and ranges from 0.05 kg C m(-2) for stone-dominated to 8.4 kg C m(-2) for grass-dominated areas. No signs of organic matter burial through cryoturbation or slope processes were found, and radiocarbon-dated SOC is generally of recent origin (< 2000 cal yr BP). An inventory of permafrost distribution in Tarfala Valley, based on the bottom temperature of snow measurements and a logistic regression model, showed that at an altitude where permafrost is probable the SOC storage is very low. In the high-altitude permafrost zones (above 1500 m), soils store only ca. 0.1 kg C m(-2). Under future climate warming, an upward shift of vegetation zones may lead to a net ecosystem C uptake from increased biomass and soil development. As a consequence, alpine permafrost environments could act as a net carbon sink in the future, as there is no loss of older or deeper SOC from thawing permafrost.

  • 11. Gentsch, N.
    et al.
    Mikutta, R.
    Alves, R. J. E.
    Barta, J.
    Capek, P.
    Gittel, A.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lashchinskiy, N.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Richter, A.
    Santruckova, H.
    Schnecker, J.
    Shibistova, O.
    Urich, T.
    Wild, B.
    Guggenberger, G.
    Storage and transformation of organic matter fractions in cryoturbated permafrost soils across the Siberian Arctic2015In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 12, no 14, p. 4525-4542Article in journal (Refereed)
    Abstract [en]

    In permafrost soils, the temperature regime and the resulting cryogenic processes are important determinants of the storage of organic carbon (OC) and its small-scale spatial variability. For cryoturbated soils, there is a lack of research assessing pedon-scale heterogeneity in OC stocks and the transformation of functionally different organic matter (OM) fractions, such as particulate and mineral-associated OM. Therefore, pedons of 28 Turbels were sampled in 5m wide soil trenches across the Siberian Arctic to calculate OC and total nitrogen (TN) stocks based on digital profile mapping. Density fractionation of soil samples was performed to distinguish between particulate OM (light fraction, LF, < 1.6 g cm(-3)), mineral associated OM (heavy fraction, HF, > 1.6 g cm(-3)), and a mobilizable dissolved pool (mobilizable fraction, MoF). Across all investigated soil profiles, the total OC storage was 20.2 +/- 8.0 kgm(-2) (mean +/- SD) to 100 cm soil depth. Fifty-four percent of this OC was located in the horizons of the active layer (annual summer thawing layer), showing evidence of cryoturbation, and another 35% was present in the upper permafrost. The HF-OC dominated the overall OC stocks (55 %), followed by LF-OC (19% in mineral and 13% in organic horizons). During fractionation, approximately 13% of the OC was released as MoF, which likely represents a readily bioavailable OM pool. Cryogenic activity in combination with cold and wet conditions was the principle mechanism through which large OC stocks were sequestered in the subsoil (16.4 +/- 8.1 kgm(-2); all mineral B, C, and permafrost horizons). Approximately 22% of the subsoil OC stock can be attributed to LF material subducted by cryoturbation, whereas migration of soluble OM along freezing gradients appeared to be the principle source of the dominant HF (63 %) in the subsoil. Despite the unfavourable abiotic conditions, low C/N ratios and high delta C-13 values indicated substantial microbial OM transformation in the subsoil, but this was not reflected in altered LF and HF pool sizes. Partial least-squares regression analyses suggest that OC accumulates in the HF fraction due to co-precipitation with multivalent cations (Al, Fe) and association with poorly crystalline iron oxides and clay minerals. Our data show that, across all permafrost pedons, the mineral-associated OM represents the dominant OM fraction, suggesting that the HF-OC is the OM pool in permafrost soils on which changing soil conditions will have the largest impact.

  • 12. Gisnås, Kjersti
    et al.
    Etzelmuller, Bernd
    Lussana, Cristian
    Hjort, Jan
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Isaksen, Ketil
    Westermann, Sebastian
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Christiansen, Hanne H.
    Frampton, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Åkerman, Jonas
    Permafrost Map for Norway, Sweden and Finland2017In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 28, no 2, p. 359-378Article in journal (Refereed)
    Abstract [en]

    A research-based understanding of permafrost distribution at a sufficient spatial resolution is important to meet the demands of science, education and society. We present a new permafrost map for Norway, Sweden and Finland that provides a more detailed and updated description of permafrost distribution in this area than previously available. We implemented the CryoGRID1 model at 1km(2) resolution, forced by a new operationally gridded data-set of daily air temperature and snow cover for Finland, Norway and Sweden. Hundred model realisations were run for each grid cell, based on statistical snow distributions, allowing for the representation of sub-grid variability of ground temperature. The new map indicates a total permafrost area (excluding palsas) of 23 400km(2) in equilibrium with the average 1981-2010 climate, corresponding to 2.2 per cent of the total land area. About 56 per cent of the area is in Norway, 35 per cent in Sweden and 9 per cent in Finland. The model results are thoroughly evaluated, both quantitatively and qualitatively, as a collaboration project including permafrost experts in the three countries. Observed ground temperatures from 25 boreholes are within +/- 2 degrees C of the average modelled grid cell ground temperature, and all are within the range of the modelled ground temperature for the corresponding grid cell. Qualitative model evaluation by field investigators within the three countries shows that the map reproduces the observed lower altitudinal limits of mountain permafrost and the distribution of lowland permafrost.

  • 13. Harden, Jennifer W.
    et al.
    Koven, Charles D.
    Ping, Chien-Lu
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    McGuire, A. David
    Camill, Phillip
    Jorgenson, Torre
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Michaelson, Gary J.
    O'Donnell, Jonathan A.
    Schuur, Edward A. G.
    Tarnocai, Charles
    Johnson, Kristopher
    Grosse, Guido
    Field information links permafrost carbon to physical vulnerabilities of thawing2012In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 39, p. L15704-Article in journal (Refereed)
    Abstract [en]

    Deep soil profiles containing permafrost (Gelisols) were characterized for organic carbon (C) and total nitrogen (N) stocks to 3 m depths. Using the Community Climate System Model (CCSM4) we calculate cumulative distributions of active layer thickness (ALT) under current and future climates. The difference in cumulative ALT distributions over time was multiplied by C and N contents of soil horizons in Gelisol suborders to calculate newly thawed C and N. Thawing ranged from 147 PgC with 10 PgN by 2050 (representative concentration pathway RCP scenario 4.5) to 436 PgC with 29 PgN by 2100 (RCP 8.5). Organic horizons that thaw are vulnerable to combustion, and all horizon types are vulnerable to shifts in hydrology and decomposition. The rates and extent of such losses are unknown and can be further constrained by linking field and modelling approaches. These changes have the potential for strong additional loading to our atmosphere, water resources, and ecosystems. Citation: Harden, J. W., et al. (2012), Field information links permafrost carbon to physical vulnerabilities of thawing, Geophys. Res. Lett., 39, L15704, doi: 10.1029/2012GL051958.

  • 14.
    Holzkämper, Steffen
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tillman, Päivi Kaislahti
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Esper, Jan
    Comparison of stable carbon and oxygen isotopes in Picea glauca tree rings and Sphagnum fuscum moss remains from subarctic Canada2012In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 78, no 2, p. 295-302Article in journal (Refereed)
    Abstract [en]

    Stable isotope ratios from tree rings and peatland mosses have become important proxies of past climate variations. We here compare recent stable carbon and oxygen isotope ratios in cellulose of tree rings from white spruce (Picea glauca), growing near the arctic tree line; and cellulose of Sphagnum fuscum stems, growing in a hummock of a subarctic peatland, in west-central Canada. Results show that carbon isotopes in S. fuscum correlate significantly with July temperatures over the past similar to 20 yr. The oxygen isotopes correlate with both summer temperature and precipitation. Analyses of the tree-ring isotopes revealed summer temperatures to be the main controlling factor for carbon isotope variations, whereas tree-ring oxygen isotope ratios are controlled by a combination of spring temperatures and precipitation totals. We also explore the potential of combining high-frequency (annual) climate signals derived from long tree-ring series with low-frequency (decadal to centennial) climate signals derived from the moss remains in peat deposits. This cross-archive comparison revealed no association between the oxygen isotopes, which likely results from the varying sensitivity of the archives to different seasons. For the carbon isotopes, common variance could be achieved through adjustments of the Sphagnum age model within dating error.

  • 15.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Landscape partitioning and environmental gradient analyses of soil organic carbon in a permafrost environment2009In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 23, no GB3006Article in journal (Refereed)
    Abstract [en]

    This study investigates landscape allocation and environmental gradients in soil organic carbon (C) storage in northeastern European Russia. The lowlands of the investigated Usa River Basin range from taiga with isolated permafrost to tundra vegetation on continuous permafrost. We compile and analyze databases on soil properties, permafrost, vegetation, and modeled climate. Mean soil C storage is estimated at 38.3 kg C m−2, with similar amounts in taiga and tundra regions. Permafrost soils hold 42% of the total soil C in the area. Peatlands dominate soil C storage with 72% of the total pool and 98% of permafrost C. Multivariate gradient analyses show that local vegetation and permafrost are strong predictors of soil chemical properties, overshadowing the effect of climate variables. This study highlights the importance of peatlands, particularly bogs, in bulk soil C storage. Soil organic matter stored in permafrost has higher C:N ratios than unfrozen material. Permafrost bogs constitute the main vulnerable C pool in the region. Remobilization of this frozen C can occur through gradual but widespread deepening of the active layer with subsequent talik formation or through more rapid but localized thermokarst erosion.

  • 16.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Patterns in Soil C Distribution in the Usa Basin (Russia): Linking Soil Properties to Environmental Variables in Constrained Gradient Analysis2008In: Ninth International Conference on Permafrost: Extended Abstracts, 2008, p. 105-106Conference paper (Other academic)
  • 17.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Tarnocai, Charles
    Ideas and perspectives: Holocene thermokarst sediments of the Yedoma permafrost region do not increase the northern peatland carbon pool2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 7, p. 2003-2010Article in journal (Refereed)
    Abstract [en]

    Permafrost deposits in the Beringian Yedoma region store large amounts of organic carbon (OC). Walter Anthony et al. (2014) describe a previously unrecognized pool of 159 Pg OC accumulated in Holocene thermokarst sediments deposited in Yedoma region alases (thermokarst depressions). They claim that these alas sediments increase the previously recognized circumpolar permafrost peat OC pool by 50 %. It is stated that previous integrated studies of the permafrost OC pool have failed to account for these deposits because the Northern Circumpolar Soil Carbon Database (NCSCD) is biased towards non-alas field sites and that the soil maps used in the NCSCD underestimate coverage of organic permafrost soils. Here we evaluate these statements against a brief literature review, existing data sets on Yedoma region soil OC storage and independent field-based and geospatial data sets of peat soil distribution in the Siberian Yedoma region. Our findings are summarized in three main points. Firstly, the sediments described by Walter Anthony et al. (2014) are primarily mineral lake sediments and do not match widely used international scientific definitions of peat or organic soils. They can therefore not be considered an addition to the circumpolar peat carbon pool. We also emphasize that a clear distinction between mineral and organic soil types is important since they show very different vulnerability trajectories under climate change. Secondly, independent field data and geospatial analyses show that the Siberian Yedoma region is dominated by mineral soils, not peatlands. Thus, there is no evidence to suggest any systematic bias in the NCSCD field data or maps. Thirdly, there is spatial overlap between these Holocene thermokarst sediments and previous estimates of permafrost soil and sediment OC stocks. These carbon stocks were already accounted for by previous studies and they do not significantly increase the known circumpolar OC pool. We suggest that these inaccurate statements made in Walter Anthony et al. (2014) mainly resulted from misunderstandings caused by conflicting definitions and terminologies across different geoscientific disciplines. A careful cross-disciplinary review of terminologies would help future studies to appropriately harmonize definitions between different fields.

  • 18.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tarnocai, Charles
    Virtanen, Tarmo
    Soil Organic Carbon Pools in a Periglacial Landscape; a Case Study from the Central Canadian Arctic2010In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 21, no 1, p. 16-29Article in journal (Refereed)
    Abstract [en]

    We investigated total storage and landscape partitioning of soil organic carbon (SOC) in continuous permafrost terrain, central Canadian Arctic. The study is based on soil chemical analyses of pedons sampled to 1-m depth at 35 individual sites along three transects. Radiocarbon dating of cryoturbated soil pockets, basal peat and fossil wood shows that cryoturbation processes have been occurring since the Middle Holocene and that peat deposits started to accumulate in a forest-tundra environment where spruce was present (∼6000 cal yrs BP). Detailed partitioning of SOC into surface organic horizons, cryoturbated soil pockets and non-cryoturbated mineral soil horizons is calculated (with storage in active layer and permafrost calculated separately) and explored using principal component analysis. The detailed partitioning and mean storage of SOC in the landscape are estimated from transect vegetation inventories and a land cover classification based on a Landsat satellite image. Mean SOC storage in the 0–100-cm depth interval is 33.8 kg C m−2, of which 11.8 kg C m−2 is in permafrost. Fifty-six per cent of the total SOC mass is stored in peatlands (mainly bogs), but cryoturbated soil pockets in Turbic Cryosols also contribute significantly (17%). Elemental C/N ratios indicate that this cryoturbated soil organic matter (SOM) decomposes more slowly than SOM in surface O-horizons.

  • 19.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tarnocai, Charles
    Virtanen, Tarmo
    Total Storage and Landscape Distribution of Soil Carbon in the Central Canadian Arctic Using Different Upscaling Tools2008Conference paper (Other academic)
  • 20.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tarnocai, Charles
    Virtanen, Tarmo
    Total Storage and Landscape Distribution of Soil Carbon in the Central Canadian Arctic Using Different Upscaling Tools2009In: Geophysical Research Abstracts vol. 11, 2009, p. EGU2009-9573Conference paper (Other academic)
  • 21.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Virtanen, Tarmo
    University of Helsinki.
    Kaverin, Dmitry
    Komi Science Centre.
    Pastukhov, Alexander
    Komi Science Centre.
    Rivkin, Felix
    Institute FSUE Fundamentprojekt.
    Marchenko, Sergey
    University of Alaska Fairbanks.
    Romanovsky, Vladimir
    University of Alaska Fairbanks.
    High‐resolution mapping of ecosystem carbon storageand potential effects of permafrost thaw in periglacialterrain, European Russian Arctic2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116Article in journal (Refereed)
    Abstract [en]

    This study describes detailed partitioning of phytomass carbon (C) and soil organiccarbon (SOC) for four study areas in discontinuous permafrost terrain, Northeast EuropeanRussia. The mean aboveground phytomass C storage is 0.7 kg C m−2. Estimated landscapeSOC storage in the four areas varies between 34.5 and 47.0 kg C m−2 with LCC (landcover classification) upscaling and 32.5–49.0 kg C m−2 with soil map upscaling. A nestedupscaling approach using a Landsat thematic mapper land cover classification for thesurrounding region provides estimates within 5 ± 5% of the local high‐resolutionestimates. Permafrost peat plateaus hold the majority of total and frozen SOC, especially inthe more southern study areas. Burying of SOC through cryoturbation of O‐ or A‐horizonscontributes between 1% and 16% (mean 5%) of total landscape SOC. The effect ofactive layer deepening and thermokarst expansion on SOC remobilization is modeled forone of the four areas. The active layer thickness dynamics from 1980 to 2099 is modeledusing a transient spatially distributed permafrost model and lateral expansion of peatplateau thermokarst lakes is simulated using geographic information system analyses.Active layer deepening is expected to increase the proportion of SOC affected by seasonalthawing from 29% to 58%. A lateral expansion of 30 m would increase the amount ofSOC stored in thermokarst lakes/fens from 2% to 22% of all SOC. By the end of thiscentury, active layer deepening will likely affect more SOC than thermokarst expansion,but the SOC stores vulnerable to thermokarst are less decomposed.

  • 22.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Routh, Joyanto
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Crill, Patrick
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mapping the degree of decomposition and thaw remobilization potential of soil organic matter in discontinuous permafrost terrain2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, p. G02030-Article in journal (Refereed)
    Abstract [en]

    Soil organic matter (SOM) stored in permafrost terrain is a key component in the global carbon cycle, but its composition and lability are largely unknown. We characterize and assess the degree of decomposition of SOM at nine sites representing major land-cover and soil types (including peat deposits) in an area of discontinuous permafrost in the European Russian Arctic. We analyze the elemental and stable isotopic composition of bulk SOM, and the degree of humification and elemental composition of humic acids (HA). The degree of decomposition is low in the O-horizons of mineral soils and peat deposits. In the permafrost free non-peatland soils there is enrichment of C-13 and N-15, and decrease in bulk C/N ratios indicating more decomposed material with depth. Spectral characterization of HA indicates low humification in O-horizons and peat deposits, but increase in humification in the deeper soil horizons of non-peatland soils, and in mineral horizons underlying peat deposits. GIS based maps indicate that less decomposed OM characteristic of the O-horizon and permafrost peat deposits constitute the bulk of landscape SOM (>70% of landscape soil C). We conclude, however, that permafrost has not been the key environmental factor controlling the current degree of decomposition of SOM in this landscape due to relatively recent permafrost aggradation. In this century, active layer deepening will mainly affect SOM with a relatively high degree of decomposition in deeper mineral soil horizons. Additionally, thawing permafrost in peat plateaus may cause rapid remobilization of less decomposed SOM through thermokarst expansion.

  • 23.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Routh, Joyanto
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Patrick, Crill
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chemical characteristics and lability of soil organic matter in permafrost terrain, European Russian ArcticManuscript (preprint) (Other academic)
  • 24.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Strauss, J.
    Zubrzycki, S.
    Harden, J. W.
    Schuur, E. A. G.
    Ping, C. -L
    Schirrmeister, L.
    Grosse, G.
    Michaelson, G. J.
    Koven, C. D.
    O'Donnell, J. A.
    Elberling, B.
    Mishra, U.
    Camill, P.
    Yu, Z.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps2014In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, no 23, p. 6573-6593Article in journal (Refereed)
    Abstract [en]

    Soils and other unconsolidated deposits in the northern circumpolar permafrost region store large amounts of soil organic carbon (SOC). This SOC is potentially vulnerable to remobilization following soil warming and permafrost thaw, but SOC stock estimates were poorly constrained and quantitative error estimates were lacking. This study presents revised estimates of permafrost SOC stocks, including quantitative uncertainty estimates, in the 0-3m depth range in soils as well as for sediments deeper than 3m in deltaic deposits of major rivers and in the Yedoma region of Siberia and Alaska. Revised estimates are based on significantly larger databases compared to previous studies. Despite this there is evidence of significant remaining regional data gaps. Estimates remain particularly poorly constrained for soils in the High Arctic region and physiographic regions with thin sedimentary overburden (mountains, highlands and plateaus) as well as for deposits below 3mdepth in deltas and the Yedoma region. While some components of the revised SOC stocks are similar in magnitude to those previously reported for this region, there are substantial differences in other components, including the fraction of perennially frozen SOC. Upscaled based on regional soil maps, estimated permafrost region SOC stocks are 217 +/- 12 and 472 +/- 27 Pg for the 0-0.3 and 0-1 m soil depths, respectively (+/- 95% confidence intervals). Storage of SOC in 0-3m of soils is estimated to 1035 +/- 150 Pg. Of this, 34 +/- 16 PgC is stored in poorly developed soils of the High Arctic. Based on generalized calculations, storage of SOC below 3m of surface soils in deltaic alluvium of major Arctic rivers is estimated as 91 +/- 52 Pg. In the Yedoma region, estimated SOC stocks below 3mdepth are 181 +/- 54 Pg, of which 74 +/- 20 Pg is stored in intact Yedoma (late Pleistocene ice-and organic-rich silty sediments) with the remainder in refrozen thermokarst deposits. Total estimated SOC storage for the permafrost region is similar to 1300 Pg with an uncertainty range of similar to 1100 to 1500 Pg. Of this, similar to 500 Pg is in non-permafrost soils, seasonally thawed in the active layer or in deeper taliks, while similar to 800 Pg is perennially frozen. This represents a substantial similar to 300 Pg lowering of the estimated perennially frozen SOC stock compared to previous estimates.

  • 25.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Virtanen, Tarmo
    Kaverin, Dmitry
    Pastukhov, Alexander
    Rivkin, Felix
    Marchenko, Sergey
    Romanovsky, Vladimir
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    High-resolution mapping of ecosystem carbon storage and potential effects of permafrost thaw in periglacial terrain, European Russian Arctic2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, p. G03024-Article in journal (Refereed)
    Abstract [en]

    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.

  • 26.
    Kaislahti Tillman, Päivi
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holzkämper, Steffen
    Andersen, Thorbjoern Joest
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Oksanen, Pirita
    Stable isotope records of Sphagnum fuscum peat as late Holocene climate proxies in north-eastern European RussiaManuscript (preprint) (Other academic)
  • 27.
    Kaislahti Tillman, Päivi
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holzkämper, Steffen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Joest Andersen, Thorbjörn
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Oksanen, Pirita
    Stable isotopes in Sphagnum fuscum peat as late-Holocene climate proxies in northeastern European Russia2013In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 23, no 10, p. 1381-1390Article in journal (Refereed)
    Abstract [en]

    The environment of the northern taiga to tundra transition is highly sensitive to climate fluctuations. In this study from northeastern European Russia, stable carbon and oxygen isotope ratios (δ13C, δ18O) in α-cellulose of Sphagnum fuscum stems subsampled from hummocks and peat plateau profiles have been used as climate proxies. The entire isotope time series, dated by lead (210Pb), caesium (137Cs) and AMS-radiocarbon (14C) dating, spans the past 2500 years. Plant macrofossil analyses were used as an aid in single species selection, but are also helpful in identifying past surface moisture conditions. The most significant relationships were found between the recent δ13C record and summer (July–August) temperatures (R 2 = 0.58, p < 0.01), and the recent δ18O record and winter (October–May) precipitation anomalies in the tundra region (R 2 = 0.36, p < 0.01). The study demonstrates that stable isotopes preserved in northern peat deposits are useful indicators for summer temperature and winter precipitation at decadal to millennial timescales.

  • 28.
    Kaislahti Tillman, Päivi
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holzkämper, Steffen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Loader, Neil J.
    Robertson, Iain
    Stable carbon and oxygen isotopes in Sphagnum fuscum peat from subarctic Canada: implications for palaeoclimate studies2010In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 270, no 1-4, p. 216-226Article in journal (Refereed)
    Abstract [en]

    Stable carbon and oxygen isotope ratios in single plant components in Sphagnum peat have a good potential to reveal environmental changes in peat archives. Two peat profiles, covering the past ~6000 years, and a Sphagnum hummock from a discontinuous permafrost area in west central Canada were studied in order to evaluate the effect of decomposition rate on isotope records and to assess which plant components are most suitable for climate reconstructions. The stable isotope values from the most recently forming Sphagnum tissues were compared with observational climate data to study the impact of variations in temperature and precipitation on the peat isotopes. Our results show that there is high correlation between δ13C values in α-cellulose isolated from Sphagnum fuscum stems and summer temperatures, whereas δ18O in the plant tissues is controlled by several factors, such as summer precipitation, summer temperature and evaporation. According to our results, decomposition as derived from C/N values and colorimetry does not seem to affect the oxygen and carbon isotope values of α-cellulose from Sphagnum fuscum peat significantly. There is, however, a (quasi-) constant offset between the isotope values of branches and stems and between whole plant material and  α-cellulose, which makes it crucial to select single moss-fractions when past climate and environmental changes are to be derived from the isotope record.

  • 29.
    Kaislahti Tillman, Päivi
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holzkämper, Steffen
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Loader, Neil J.
    Robinson, Iain
    Long-term climate variability in continental subarctic Canada: A 6200-year record derived from stable isotopes in peat2010In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 298, no 3, p. 235-246Article in journal (Refereed)
    Abstract [en]

    The rapid warming of arctic regions during recent decades has been recorded by instrumental monitoring, but the natural climate variability in the past is still sparsely reconstructed across many areas. We have reconstructed past climate changes in subarctic west-central Canada. Stable carbon and oxygen isotope ratios (δ13C, δ18O) were derived from a single Sphagnum fuscum plant component; α-cellulose isolated from stems. Periods of warmer and cooler conditions identified in this region, described in terms of a “Mediaeval Climatic Anomaly” and “Little Ice Age” were registered in the temperature reconstruction based on the δ13C record. Some conclusions could be drawn about wet/dry shifts during the same time interval from the δ18O record, humification indices and the macrofossil analysis. The results were compared with other proxy data from the vicinity of the study area. The amplitude of the temperature change was similar to that in chironomid based reconstructions, showing c. 6.5±2.3°C variability in July temperatures during the past 6.2 ka.

  • 30. Koven, C. D.
    et al.
    Schuur, E. A. G.
    Schaedel, C.
    Bohn, T. J.
    Burke, E. J.
    Chen, G.
    Chen, X.
    Ciais, P.
    Grosse, G.
    Harden, J. W.
    Hayes, D. J.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jafarov, E. E.
    Krinner, G.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lawrence, D. M.
    MacDougall, A. H.
    Marchenko, S. S.
    McGuire, A. D.
    Natali, S. M.
    Nicolsky, D. J.
    Olefeldt, D.
    Peng, S.
    Romanovsky, V. E.
    Schaefer, K. M.
    Strauss, J.
    Treat, C. C.
    Turetsky, M.
    A simplified, data-constrained approach to estimate the permafrost carbon-climate feedback2015In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 373, no 2054, article id 20140423Article in journal (Refereed)
    Abstract [en]

    We present an approach to estimate the feedback from large-scale thawing of permafrost soils using a simplified, data-constrained model that combines three elements: soil carbon (C) maps and profiles to identify the distribution and type of C in permafrost soils; incubation experiments to quantify the rates of C lost after thaw; and models of soil thermal dynamics in response to climate warming. We call the approach the Permafrost Carbon Network Incubation-Panarctic Thermal scaling approach (PInc-PanTher). The approach assumes that C stocks do not decompose at all when frozen, but once thawed follow set decomposition trajectories as a function of soil temperature. The trajectories are determined according to a three-pool decomposition model fitted to incubation data using parameters specific to soil horizon types. We calculate litterfall C inputs required to maintain steady-state C balance for the current climate, and hold those inputs constant. Soil temperatures are taken from the soil thermal modules of ecosystem model simulations forced by a common set of future climate change anomalies under two warming scenarios over the period 2010 to 2100. Under a medium warming scenario (RCP4.5), the approach projects permafrost soil C losses of 12.2-33.4 Pg C; under a high warming scenario (RCP8.5), the approach projects C losses of 27.9-112.6 Pg C. Projected C losses are roughly linearly proportional to global temperature changes across the two scenarios. These results indicate a global sensitivity of frozen soil C to climate change (gamma sensitivity) of -14 to -19 PgC degrees C-1 on a 100 year time scale. For CH4 emissions, our approach assumes a fixed saturated area and that increases in CH4 emissions are related to increased heterotrophic respiration in anoxic soil, yielding CH4 emission increases of 7% and 35% for the RCP4.5 and RCP8.5 scenarios, respectively, which add an additional greenhouse gas forcing of approximately 10-18%. The simplified approach presented here neglects many important processes that may amplify or mitigate C release from permafrost soils, but serves as a data-constrained estimate on the forced, large-scale permafrost C response to warming.

  • 31.
    Kuhry, P.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Dorrepaal, E.
    Hugelius, G.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Schuur, E. A. G.
    Tarnocai, C.
    Potential Remobilization of Belowground Permafrost Carbon under Future Global Warming2010In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 21, no 2, p. 208-214Article in journal (Refereed)
    Abstract [en]

    Research on permafrost carbon has dramatically increased in the past few years. A new estimate of 1672 Pg C of belowground organic carbon in the northern circumpolar permafrost region more than doubles the previous value and highlights the potential role of permafrost carbon in the Earth System. Uncertainties in this new estimate remain due to relatively few available pedon data for certain geographic sectors and the deeper cryoturbated soil horizons, and the large polygon size in the soil maps used for upscaling. The large permafrost carbon pool is not equally distributed across the landscape: peat deposits, cryoturbated soils and the loess-like deposits of the yedoma complex contain disproportionately large amounts of soil organic matter, often exhibiting a low degree of decomposition. Recent findings in Alaska and northern Sweden provide strong evidence that the deeper soil carbon in permafrost terrain is starting to be released, supporting previous reports from Siberia. The permafrost carbon pool is not yet fully integrated in climate and ecosystem models and an important objective should be to define typical pedons appropriate for model setups. The thawing permafrost carbon feedback needs to be included in model projections of future climate change.

  • 32.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Palsa and peat plateau development in the Hudson Bay Lowlands, Canada: timing, pathways and causes2008In: Boreas, ISSN 0300-9483, Vol. 37, no 2, p. 316-327Article in journal (Refereed)
    Abstract [en]

    The Holocene development of a treed palsa bog and a peat plateau bog, located near the railroad to Churchill in the Hudson Bay Lowlands of northeastern Manitoba, was traced using peat macrofossil and radiocarbon analyses. Both sites first developed as wet rich fens through paludification of forested uplands around 6800 cal. yr BP. Results show a 20th-century age for the palsa formation and repeated periods of permafrost aggradation and collapse at the peat plateau site during the late Holocene. This timing of permafrost dynamics corroborates well with that inferred from previous studies on other permafrost peatlands in the same region. The developmental history of the palsa and peat plateau bogs is similar to that of adjacent permafrost-free fens, except for the specific frost heave and collapse features associated with permafrost dynamics. Permafrost aggradation and degradation is ascribed to regional climatic, local autogenic and other factors. Particularly the very recent palsa development can be assessed in terms of climatic changes as inferred from meteorological data and surface hydrological changes related to construction of the railroad. The results indicate that cold years with limited snowfall as well as altered drainage patterns associated with infrastructure development may have contributed to the recent palsa formation.

  • 33.
    Kuhry, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Grosse, G.
    Harden, J. W.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Koven, C. D.
    Ping, C-L
    Schirrmeister, L.
    Tarnocai, C.
    Characterisation of the Permafrost Carbon Pool2013In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 24, no 2, p. 146-155Article in journal (Refereed)
    Abstract [en]

    The current estimate of the soil organic carbon (SOC) pool in the northern permafrost region of 1672 Petagrams (Pg) C is much larger than previously reported and needs to be incorporated in global soil carbon (C) inventories. The Northern Circumpolar Soil Carbon Database (NCSCD), extended to include the range 0-300cm, is now available online for wider use by the scientific community. An important future aim is to provide quantitative uncertainty ranges for C pool estimates. Recent studies have greatly improved understanding of the regional patterns, landscape distribution and vertical (soil horizon) partitioning of the permafrost C pool in the upper 3m of soils. However, the deeper C pools in unconsolidated Quaternary deposits need to be better constrained. A general lability classification of the permafrost C pool should be developed to address potential C release upon thaw. The permafrost C pool and its dynamics are beginning to be incorporated into Earth System models, although key periglacial processes such as thermokarst still need to be properly represented to obtain a better quantification of the full permafrost C feedback on global climate change.

  • 34.
    Lindgren, Amelie
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Extensive loss of past permafrost carbon but a net accumulation into present-day soils2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 560, no 7717, p. 219-+Article in journal (Refereed)
    Abstract [en]

    Atmospheric concentrations of carbon dioxide increased between the Last Glacial Maximum (LGM, around 21,000 years ago) and the preindustrial era(1). It is thought that the evolution of this atmospheric carbon dioxide (and that of atmospheric methane) during the glacial-to-interglacial transition was influenced by organic carbon that was stored in permafrost during the LGM and then underwent decomposition and release following thaw(2,3). It has also been suggested that the rather erratic atmospheric delta C-13 and Delta C-14 signals seen during deglaciation(1.4) could partly be explained by the presence of a large terrestrial inert LGM carbon stock, despite the biosphere being less productive (and therefore storing less carbon)(5,6). Here we present an empirically derived estimate of the carbon stored in permafrost during the LGM by reconstructing the extent and carbon content of LGM biomes, peatland regions and deep sedimentary deposits. We find that the total estimated soil carbon stock for the LGM northern permafrost region is smaller than the estimated present-day storage (in both permafrost and non-permafrost soils) for the same region. A substantial decrease in the permafrost area from the LGM to the present day has been accompanied by a roughly 400-petagram increase in the total soil carbon stock. This increase in soil carbon suggests that permafrost carbon has made no net contribution to the atmospheric carbon pool since the LGM. However, our results also indicate potential postglacial reductions in the portion of the carbon stock that is trapped in permafrost, of around 1,000 petagrams, supporting earlier studies(7). We further find that carbon has shifted from being primarily stored in permafrost mineral soils and loess deposits during the LGM, to being roughly equally divided between peatlands, mineral soils and permafrost loess deposits today.

  • 35.
    Lindgren, Amelie
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Lund University, Sweden.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Christensen, Torben R.
    Vandenberghe, Jef
    GIS-based Maps and Area Estimates of Northern Hemisphere Permafrost Extent during the Last Glacial Maximum2016In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 27, no 1, p. 6-16Article in journal (Refereed)
    Abstract [en]

    This study presents GIS-based estimates of permafrost extent in the northern circumpolar region during the Last Glacial Maximum (LGM), based on a review of previously published maps and compilations of field evidence in the form of ice-wedge pseudomorphs and relict sand wedges. We focus on field evidence localities in areas thought to have been located along the past southern border of permafrost. We present different reconstructions of permafrost extent, with areal estimates of exposed sea shelf, ice sheets and glaciers, to assess areas of minimum, likely and maximum permafrost extents. The GIS-based mapping of these empirical reconstructions allows us to estimate the likely area of northern permafrost during the LGM as 34.5 million km(2) (which includes 4.7 million km(2) of permafrost on exposed coastal sea shelves). The minimum estimate is 32.7 million km(2) and the maximum estimate is 35.3 million km(2). The extent of LGM permafrost is estimated to have been between c. 9.1 to 11.7 million km(2) larger than its current extent on land (23.6 million km(2)). However, 2.4 million km(2) of the lost land area currently remains as subsea permafrost on the submerged coastal shelves. The LGM permafrost extent in the northern circumpolar region during the LGM was therefore about 33 percent larger than at present. The net loss of northern permafrost since the LGM is due to its disappearance in large parts of Eurasia, which is not compensated for by gains in North America in areas formerly covered by the Laurentide ice sheet.

  • 36. Loisel, Julie
    et al.
    Yu, Zicheng
    Beilman, David W.
    Camill, Philip
    Alm, Jukka
    Amesbury, Matthew J.
    Anderson, David
    Andersson, Sofia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bochicchio, Christopher
    Barber, Keith
    Belyea, Lisa R.
    Bunbury, Joan
    Chambers, Frank M.
    Charman, Daniel J.
    De Vleeschouwer, Francois
    Fialkiewicz-Koziel, Barbara
    Finkelstein, Sarah A.
    Galka, Mariusz
    Garneau, Michelle
    Hammarlund, Dan
    Hinchcliffe, William
    Holmquist, James
    Hughes, Paul
    Jones, Miriam C.
    Klein, Eric S.
    Kokfelt, Ulla
    Korhola, Atte
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lamarre, Alexandre
    Lamentowicz, Mariusz
    Large, David
    Lavoie, Martin
    MacDonald, Glen
    Magnan, Gabriel
    Makila, Markku
    Mallon, Gunnar
    Mathijssen, Paul
    Mauquoy, Dmitri
    McCarroll, Julia
    Moore, Tim R.
    Nichols, Jonathan
    O'Reilly, Benjamin
    Oksanen, Pirita
    Packalen, Maara
    Peteet, Dorothy
    Richard, Pierre J. H.
    Robinson, Stephen
    Ronkainen, Tiina
    Rundgren, Mats
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tarnocai, Charles
    Thom, Tim
    Tuittila, Eeva-Stiina
    Turetsky, Merritt
    Valiranta, Minna
    van der Linden, Marjolein
    van Geel, Bas
    van Bellen, Simon
    Vitt, Dale
    Zhao, Yan
    Zhou, Weijian
    A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation2014In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 24, no 9, p. 1028-1042Article in journal (Refereed)
    Abstract [en]

    Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45 degrees N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan Plateau. For all northern peatlands, carbon content in organic matter was estimated at 42 +/- 3% (standard deviation) for Sphagnum peat, 51 +/- 2% for non-Sphagnum peat, and at 49 +/- 2% overall. Dry bulk density averaged 0.12 +/- 0.07 g/cm(3), organic matter bulk density averaged 0.11 +/- 0.05 g/cm(3), and total carbon content in peat averaged 47 +/- 6%. In general, large differences were found between Sphagnum and non-Sphagnum peat types in terms of peat properties. Time-weighted peat carbon accumulation rates averaged 23 +/- 2 (standard error of mean) g C/m(2)/yr during the Holocene on the basis of 151 peat cores from 127 sites, with the highest rates of carbon accumulation (25-28 g C/m(2)/yr) recorded during the early Holocene when the climate was warmer than the present. Furthermore, we estimate the northern peatland carbon and nitrogen pools at 436 and 10 gigatons, respectively. The database is publicly available at https://peatlands.lehigh.edu.

  • 37. Luoto, Tomi P.
    et al.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holzkämper, Steffen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Solovieva, Nadia
    Self, Angela E.
    A 2000-year record of lake ontogeny and climate variability from the north-eastern European Russian Arctic2017In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 27, no 3, p. 339-348Article in journal (Refereed)
    Abstract [en]

    A lake sediment record from the north-eastern European Russian Arctic was examined using palaeolimnological methods, including subfossil chironomid and diatom analysis. The objective of this study is to disentangle environmental history of the lake and climate variability during the past 2000 years. The sediment profile was divided into two main sections following changes in the lithology, separating the limno-telmatic phase between similar to 2000 and 1200 cal. yr BP and the lacustrine phase between similar to 1200 cal. yr BP and the present. Owing to the large proportion of semi-terrestrial chironomids and poor modern analogues, a reliable chironomid-based temperature reconstruction for the limno-telmatic phase was not possible. However, the lacustrine phase showed gradually cooling climate conditions from similar to 1200 cal. yr BP until similar to 700 cal. yr BP. The increase in stream chironomids within this sediment section indicates that this period may also have had increased precipitation that caused the adjacent river to overflow, subsequently transporting chironomids to the lacustrine basin. After a short-lived warm phase at similar to 700 cal. yr BP, the climate again cooled, and a progressive climate warming trend was evident from the most recent sediment samples, where the biological assemblages seem to have experienced an eutrophication-like response to climate warming. The temperature reconstruction showed more similarities with the climate development in the Siberian side of the Urals than with northern Europe. This study provides a characteristic archive of arctic lake ontogeny and a valuable temperature record from a remote climate-sensitive area of northern Russia.

  • 38. Markkula, Inkeri
    et al.
    Oksanen, Pirita
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Indicator value of oribatid mites in determining past permafrost dynamics in northern European sub-Arctic peatlands2018In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 47, no 3, p. 884-896Article in journal (Refereed)
    Abstract [en]

    Permafrost dynamics play an important role in the surface hydrology and carbon balance of northern peatlands. Plant macrofossil analysis with radiocarbon dating has been widely used in detecting past permafrost dynamics in peatlands; however, there is a lack of permafrost-specific plant indicator species, which makes it challenging to determine the exact timing of historical permafrost aggradation. We investigated the indicator value of oribatid mites in determining past permafrost dynamics in sub-Arctic peatlands. Analyses of subfossil oribatid mite assemblages of Holocene peat profiles from two mires, one in northern Finland and one in northeastern European Russia, were carried out and interpreted using modern calibration data from the same study areas. The results were compared with previously published reconstructions of permafrost history based on plant macrofossil analyses from the same locations. The results suggest that the oribatid mites Carabodes labyrinthicus, Chamobates borealis and Neoribates aurantiacus are promising indicator species to detect past permafrost occurrence in peatlands. In addition, N.aurantiacus is clearly associated with the presence of lichens, which is particularly useful because lichen remains are rarely preserved in peat deposits. Results are in accordance with earlier studies showing that oribatid mites are useful indicators of past environmental change.

  • 39.
    Matthes, Heidrun
    et al.
    Alfred Wegener Inst Polar & Marine Res, Potsdam, Germany .
    Rinke, Anette
    Alfred Wegener Inst Polar & Marine Res, Potsdam, Germany .
    Miller, Paul A.
    Lund Univ, Dept Earth & Ecosyst Sci, Lund, Sweden .
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dethloff, Klaus
    Alfred Wegener Inst Polar & Marine Res, Potsdam, Germany .
    Wolf, Anett
    Swiss Fed Inst Technol, Inst Terr Ecosyst, Zurich, Switzerland .
    Sensitivity of high-resolution Arctic regional climate model projections to different implementations of land surface processes2012In: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 111, no 2, p. 197-214Article in journal (Refereed)
    Abstract [en]

    This paper discusses the effects of vegetation cover and soil parameters on the climate change projections of a regional climate model over the Arctic domain. Different setups of the land surface model of the regional climate model HIRHAM were realized to analyze differences in the atmospheric circulation caused by (1) the incorporation of freezing/thawing of soil moisture, (2) the consideration of top organic soil horizons typical for the Arctic and (3) a vegetation shift due to a changing climate. The largest direct thermal effect in 2 m air temperature was found for the vegetation shift, which ranged between −1.5 K and 3 K. The inclusion of a freeze/thaw scheme for soil moisture shows equally large sensitivities in spring over cool areas with high soil moisture content. Although the sensitivity signal in 2 m air temperature for the experiments differs in amplitude, all experiments show changes in mean sea level pressure (mslp) and geopotential height (z) throughout the troposphere of similar magnitude (mslp: −2 hPa to 1.5 hPa, z: −15 gpm to 5 gpm). This points to the importance of dynamical feedbacks within the atmosphere-land system. Land and soil processes have a distinct remote influence on large scale atmospheric circulation patterns in addition to their direct, regional effects. The assessment of induced uncertainties due to the changed implementations of land surface processes discussed in this study demonstrates the need to take all those processes for future Arctic climate projections into account, and demonstrates a clear need to include similar implementations in regional and global climate models.

  • 40. McGuire, A. David
    et al.
    Macdonald, Robie W.
    Schuur, Edward A. G.
    Harden, Jennifer W.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Hayes, Daniel J.
    Christensen, Torben R.
    Heimann, Martin
    The carbon budget of the northern cryosphere region2010In: Current Opinion in Environmental Sustainability, ISSN 1877-3435, Vol. 2, no 4, p. 231-236Article, review/survey (Refereed)
    Abstract [en]

    The northern cryosphere is undergoing substantial warming of permafrost and loss of sea ice. Release of stored carbon to the atmosphere in response to this change has the potential to affect the global climate system. Studies indicate that the northern cryosphere has been not only a substantial sink for atmospheric CO2 in recent decades, but also an important source of CH4 because of emissions from wetlands and lakes. Analyses suggest that the sensitivity of the carbon cycle of the region over the 21st Century is potentially large, but highly uncertain because numerous pathways of response will be affected by warming. Further research should focus on sensitive elements of the carbon cycle such as the consequences of increased fire disturbance, permafrost degradation, and sea ice loss in the northern cryosphere region.

  • 41. Mishra, U.
    et al.
    Jastrow, J. D.
    Matamala, R.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Koven, C. D.
    Harden, J. W.
    Ping, C. L.
    Michaelson, G. J.
    Fan, Z.
    Miller, R. M.
    McGuire, A. D.
    Tarnocai, C.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Riley, W. J.
    Schaefer, K.
    Schuur, E. A. G.
    Jörgenson, M. T.
    Hinzman, L. D.
    Empirical estimates to reduce modeling uncertainties of soil organic carbon in permafrost regions: a review of recent progress and remaining challenges2013In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 8, no 3, p. 035020-Article in journal (Refereed)
    Abstract [en]

    The vast amount of organic carbon (OC) stored in soils of the northern circumpolar permafrost region is a potentially vulnerable component of the global carbon cycle. However, estimates of the quantity, decomposability, and combustibility of OC contained in permafrost-region soils remain highly uncertain, thereby limiting our ability to predict the release of greenhouse gases due to permafrost thawing. Substantial differences exist between empirical and modeling estimates of the quantity and distribution of permafrost-region soil OC, which contribute to large uncertainties in predictions of carbon-climate feedbacks under future warming. Here, we identify research challenges that constrain current assessments of the distribution and potential decomposability of soil OC stocks in the northern permafrost region and suggest priorities for future empirical and modeling studies to address these challenges.

  • 42. Olefeldt, D.
    et al.
    Goswami, S.
    Grosse, G.
    Hayes, D.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    McGuire, A. D.
    Romanovsky, V. E.
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Schuur, E. A. G.
    Turetsky, M. R.
    Circumpolar distribution and carbon storage of thermokarst landscapes2016In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 13043Article in journal (Refereed)
    Abstract [en]

    Thermokarst is the process whereby the thawing of ice- rich permafrost ground causes land subsidence, resulting in development of distinctive landforms. Accelerated thermokarst due to climate change will damage infrastructure, but also impact hydrology, ecology and biogeochemistry. Here, we present a circumpolar assessment of the distribution of thermokarst landscapes, defined as landscapes comprised of current thermokarst landforms and areas susceptible to future thermokarst development. At 3.6 x 10(6) km(2), thermokarst landscapes are estimated to cover similar to 20% of the northern permafrost region, with approximately equal contributions from three landscape types where characteristic wetland, lake and hillslope thermokarst landforms occur. We estimate that approximately half of the below-ground organic carbon within the study region is stored in thermokarst landscapes. Our results highlight the importance of explicitly considering thermokarst when assessing impacts of climate change, including future landscape greenhouse gas emissions, and provide a means for assessing such impacts at the circumpolar scale.

  • 43.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cable, Stefanie
    Christiansen, Hanne H.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Landform partitioning and estimates of deep storage of soil organic matter in Zackenberg, Greenland2018In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 12, no 5, p. 1735-1744Article in journal (Refereed)
    Abstract [en]

    Soils in the northern high latitudes are a key component in the global carbon cycle, with potential feedback on climate. This study aims to improve the previous soil organic carbon (SOC) and total nitrogen (TN) storage estimates for the Zackenberg area (NE Greenland) that were based on a land cover classification (LCC) approach, by using geomorphological upscaling. In addition, novel organic carbon (OC) estimates for deeper alluvial and deltaic deposits (down to 300 cm depth) are presented. We hypothesise that land-forms will better represent the long-term slope and depositional processes that result in deep SOC burial in this type of mountain permafrost environments. The updated mean SOC storage for the 0-100 cm soil depth is 4.8 kg Cm-2, which is 42% lower than the previous estimate of 8.3 kg Cm-2 based on land cover upscaling. Similarly, the mean soil TN storage in the 0-100 cm depth decreased with 44% from 0.50 kg (+/- 0.1 CI) to 0.28 (+/- 0.1 CI) kg TN m(-2). We ascribe the differences to a previous areal overestimate of SOC- and TN-rich vegetated land cover classes. The landform-based approach more correctly constrains the depositional areas in alluvial fans and deltas with high SOC and TN storage. These are also areas of deep carbon storage with an additional 2.4 kg Cm-2 in the 100-300 cm depth interval. This research emphasises the need to consider geomorphology when assessing SOC pools in mountain permafrost landscapes.

  • 44.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Soil organic carbon storage in continuous permafrost terrain; two case studies from NE Greenlandand NE Siberia2011Conference paper (Other academic)
    Abstract [en]

    The northern circumpolar permafrost region occupies about 16% of the global soil areaand holds approximately 50% of the global belowground soil organic carbon (SOC). We describe thequantity and quality of soil organic matter (SOM) in two areas of continuous permafrost in NE Greenland andNE Siberia. The main emphasis lies on the role of cryoturbation and Pleistocene loess-like deposits(yedoma) for SOC storage. This study is based on field work in three different study sites: Zackenberg(Greenland) and Shalaurovo and Chersky (Siberia), as well as laboratory analysis and radiocarbon dating.The estimated mean SOC storage in the upper meter of soil for Zackenberg is 10.5 kg C m-2 with 16% incryoturbated soil pockets. In Shalaurovo, the mean SOC storage is 29.0 kg C m-2 and in Chersky 21.7 kg Cm-2 with more than 30% stored in cryoturbated soil pockets. The study also presents new analyses for deepyedoma deposits(down to 5 m depth). Data from these sites show that the dry bulk densities are muchlower (due to excess ground ice) than those previously reported in the literature, leading to lower estimatesof SOC storage in these deposits.

  • 45.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lashchinskiy, Nikolay
    Tamstorf, Mikkel P.
    Richter, Andreas
    Elberling, Bo
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Storage, Landscape Distribution, and Burial History of Soil Organic Matter in Contrasting Areas of Continuous Permafrost2015In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 47, no 1, p. 71-88Article in journal (Refereed)
    Abstract [en]

    This study describes and compares soil organic matter (SOM) quantity and characteristics in two areas of continuous permafrost, a mountainous region in NE Greenland (Zackenberg study site) and a lowland region in NE Siberia (Cherskiy and Shalaurovo study sites). Our assessments are based on stratified-random landscape-level inventories of soil profiles down to 1 m depth, with physico-chemical, elemental, and radiocarbon-dating analyses. The estimated mean soil organic carbon (SOC) storage in the upper meter of soils in the NE Greenland site is 8.3 ± 1.8 kg C m-2 compared to 20.3 ± 2.2 kg C m-2 and 30.0 ± 2.0 kg C m-2 in the NE Siberian sites (95% confidence intervals). The lower SOC storage in the High Arctic site in NE Greenland can be largely explained by the fact that 59% of the study area is located at higher elevation with mostly barren ground and thus very low SOC contents. In addition, SOC-rich fens and bogs occupy a much smaller proportion of the landscape in NE Greenland (∼3%) than in NE Siberia (∼20%). The contribution of deeper buried C-enriched material in the mineral soil horizons to the total SOC storage is lower in the NE Greenland site (∼13%) compared to the NE Siberian sites (∼24%–30%). Buried SOM seems generally more decomposed in NE Greenland than in NE Siberia, which we relate to different burial mechanisms prevailing in these regions.

  • 46.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Grain size controls on cryoturbation and soil organic carbon density in permafrost-affected soils2018In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 29, no 2, p. 112-120Article in journal (Refereed)
    Abstract [en]

    This meta-analysis aims to describe the relationship between grain size distributions and soil organic carbon (SOC) storage in mineral subsoil and SOC-enriched cryoturbated pockets in five areas of continuous permafrost that differ in glaciation history and soil parent materials. Our results show a positive relationship between the proportion of soil particles in fine-grained fractions (colloid to medium silt) and SOC storage. Finer textured soils had significantly higher SOC storage in mineral subsoil samples (not SOC-enriched through cryoturbation) than coarser textured soils. However, the process of SOC enrichment through cryoturbation was most pronounced in soils with coarser grain sizes in the range of coarse silt and very fine sand. Although fine-grained textures provide better physical and biochemical protection for soil organic matter, their strong cohesion reduces the mixing of soil horizons and the effectiveness of cryoturbation. A higher ratio of coarse silt to clay in samples was a good predictor of SOC enrichment through cryoturbation across soil samples, soil profiles and study areas.

  • 47.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ramage, Justine
    Stockholm University, Faculty of Science, Department of Physical Geography. Helmholtz Centre for Polar and Marine Research, Germany.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gentsch, Norman
    Lashchinskiy, Nikolay
    Richter, Andreas
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Controls on the storage of organic carbon in permafrost soil in northern Siberia2016In: European Journal of Soil Science, ISSN 1351-0754, E-ISSN 1365-2389, Vol. 67, no 4, p. 478-491Article in journal (Refereed)
    Abstract [en]

    This research examined soil organic carbon (SOC), total nitrogen (TN) and aboveground phytomass carbon(PhC) stocks in two areas of the Taymyr Peninsula, northern Siberia.We combined field sampling, chemical and14C radiocarbon dating analyses with land cover classifications for landscape-level assessments. The estimatedmean for the 0–100-cm depth SOC stocks was 14.8 and 20.8 kgCm−2 in Ary-Mas and Logata, respectively. Thecorresponding values for TN were 1.0 and 1.3 kgNm−2. On average, about 2% only (range 0–12%) of the totalecosystem C is stored in PhC. In both study areas about 34% of the SOC at 0–100 cm is stored in cryoturbatedpockets, which have formed since at least the early Holocene. The larger carbon/nitrogen (C/N) ratio of thiscryoturbated material indicates that it consists of relatively undecomposed soil organic matter (SOM). Thereare substantial differences in SOC stocks and SOM properties within and between the two study areas, whichemphasizes the need to consider both geomorphology and soil texture in the assessment of landscape-level andregional SOC stocks.

    Highlights

    • This research addresses landscape-scale and regional variation in SOC stocks.

    • Landform and soil texture are taken into account in the analysis.

    • The contribution of phytomass to total ecosystem C stored is limited.

    • Large SOC stocks are susceptible to decomposition following permafrost thaw.

  • 48.
    Pluchon, Nathalie
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Swedish University of Agricultural Sciences, Sweden.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuusinen, Nea
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Recent paludification rates and effects on total ecosystem carbon storage in two boreal peatlands of Northeast European Russia2014In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 24, no 9, p. 1126-1136Article in journal (Refereed)
    Abstract [en]

    Forest and peatland ecosystems constitute the two major carbon pools in the boreal region. We assess the evolution in total storage and partitioning of ecosystem carbon following recent paludification of forest into peatland at two sites in Northeast European Russia. Based on radiocarbon dating of basal peat and quantification of total ecosystem carbon storage, our results show that paludification rates and its consequences for carbon storage vary significantly between sites. A peatland expanding on ground with steeper slopes has experienced a slow lateral advance in recent times, about 2.6 m on average per century, whereas a peatland in flatter terrain has expanded much more rapidly, about 35 m on average per century. The total ecosystem carbon storage (sum of phytomass, top soil organics or peat, and 30 cm of underlying mineral soil) showed a long-term trend toward increased ecosystem C storage following the replacement of forest (mean value = 20.8 kg C/m(2), range = 13.0-43.4 kg C/m(2)) by peatland (>100 kg C/m(2) in the deepest peat deposits). However, the transitional stage in which the forest is replaced by the margin of the peatland results in a short-term decrease of carbon stored in the ecosystem with a mean loss of 7.5 kg C/m(2). After the initiation of a peatland through paludification, a period of decades to centuries of peat accumulation is needed to compensate for the initial loss of carbon. In the short term, an intensification of the paludification process could lead to a loss of carbon stored in the boreal region.

  • 49. Rinke, A.
    et al.
    Matthes, H.
    Christensen, J. H.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Romanovsky, V. E.
    Dethloff, K.
    Arctic RCM simulations of temperature and precipitation derived indices relevant to future frozen ground conditions2012In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 80-81, p. 136-148Article in journal (Refereed)
    Abstract [en]

    A regional climate model with high horizontal resolution (25 km) is used to downscale 20-year-long time slices of present-day (1980–1999) and future (2046–2065, 2080–2099) Arctic climate, as simulated by the ECHAM5/MPI-OM general circulation model under the A1B emission scenario. Changes in simulated air temperature and derived indices at the end of the century indicate that significant impacts on permafrost conditions should be expected. But the magnitude of the change is regionally conditioned beyond what is obvious: Warm permafrost in the sporadic to discontinuous zone is threatened and may degrade or even complete thaw before the end of the century. A decrease in freezing and increase in thawing degree-days is interpreted as potential decrease in seasonal freeze depth and increase in active layer thickness (ALT). We show that for some regions increasing maximum summer temperature is associated with an increase of interannual temperature variability in summer, while in other regions decreased maximum summer temperatures are related to decreased variability. The occurrence of warm/cold summers and spells changes significantly in the future time slices using the present-day criteria for classification. Taken together this implies a regionally varying exposure to significant change in permafrost conditions. In addition to these aspects of the general warming trend that would promote an increase in ALT and a northward shift of the southern permafrost boundary, an analysis of the occurrence of warm summers and spells highlight some particularly vulnerable regions for permafrost degradation (e.g. West Siberian Plain, Laptev Sea coast, Canadian Archipelago), but also some less vulnerable regions (e.g. Mackenzie Mountains).

  • 50. Routh, J.
    et al.
    Bianchi, T. S.
    Hutchings, J. A.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ranjan, R. K.
    Organic carbon characteristics in Swedish forest soil trace post-depositional carbon dynamics2016In: European Journal of Soil Science, ISSN 1351-0754, E-ISSN 1365-2389, Vol. 67, no 4, p. 492-503Article in journal (Refereed)
    Abstract [en]

    We investigated soil organic carbon (SOC) characteristics in three forests along a north-south transect in Sweden where these forest types cover about 69% of the landscape. There was variation in C-14 ages, and the median ages ranged from about 25 to > 2500 cal BP in SOC. Although total SOC and nitrogen (N) contents decreased, stable carbon isotope and humification indices increased with depth. These progressive changes with depth and age were related to degradation. The delta C-13 values and specific biomarkers indicated that organic carbon was primarily from C-3 plants. Biomarkers were effective in distinguishing OC input from specific sources (i.e. angiosperms, gymnosperms and grasses). A sharp decrease in biomarkers with depth indicated degradation of OC in the upper soil horizon, and limited contribution in the subsoil towards the stabilization of SOC. The sharp decrease in carbon stocks and C-14 age in the soil OC pool with increasing soil depth, and quite large values for the percentage of modern carbon, suggested a decrease in SOC pools. Overall, these results showed that carbon sequestration in high latitude forests was small, and their role as potential carbon sinks needs to be reassessed.

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