scholarly journals Ecosystem changes across a gradient of permafrost degradation in subarctic Québec (Tasiapik Valley, Nunavik, Canada)

2019 ◽  
Vol 5 (1) ◽  
pp. 1-26 ◽  
Author(s):  
Maude Pelletier ◽  
Michel Allard ◽  
Esther Levesque
Keyword(s):  
Snow Cover ◽  
Climate Warming ◽  
Organic Matter Content ◽  
Integrated Approach ◽  
Matter Content ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Permafrost Thaw ◽  
Discontinuous Permafrost ◽  
Cover Thickness

Permafrost thaw, tundra shrubification, and changes in snow cover properties are documented impacts of climate warming, particularly in subarctic regions where discontinuous permafrost is disappearing. To obtain some insight into those changes, permafrost, active layer thickness, vegetation, snow cover, ground temperature, soil profiles, and carbon content were surveyed in an integrated approach in six field plots along a chronosequence of permafrost thaw on an ice-rich silty soil. Historical air photographs and dendrochronology provided the chronological context. Comparison of the plots reveals a positive feedback effect between thaw settlement, increased snow cover thickness, shrub growth, increase in soil temperature, and the process of permafrost decay. By the end of the sequence permafrost was no longer sustainable. Along the estimated 90 year duration of the chronosequence, the originally centimeter-thin pedogenic horizons under mosses and lichens increased to a thickness of nearly 65 cm under shrubs and trees. Snow cover increased from negligible to over 2 m. The thickness of soil organic layers and soil organic matter content increased manyfold, likely a result of the increased productivity in the shrub-dominated landscape. The results of this study strongly suggest that permafrost ecosystems in the subarctic are being replaced under climate warming by shrub and forest ecosystems enriched in carbon on more evolved soils.

scholarly journals Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014

2021 ◽  
Vol 380 (2215) ◽  
Author(s):  
Ruth K. Varner ◽  
Patrick M. Crill ◽  
Steve Frolking ◽  
Carmody K. McCalley ◽  
Sophia A. Burke ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Open Water ◽  
Climate Forcing ◽  
Trace Gas ◽  
Active Layer Thickness ◽  
Emission Rates ◽  
Trace Gas Emissions ◽  
Permafrost Thaw ◽  
Discontinuous Permafrost ◽  
Vegetation Species

Permafrost thaw increases active layer thickness, changes landscape hydrology and influences vegetation species composition. These changes alter belowground microbial and geochemical processes, affecting production, consumption and net emission rates of climate forcing trace gases. Net carbon dioxide (CO 2 ) and methane (CH 4 ) fluxes determine the radiative forcing contribution from these climate-sensitive ecosystems. Permafrost peatlands may be a mosaic of dry frozen hummocks, semi-thawed or perched sphagnum dominated areas, wet permafrost-free sedge dominated sites and open water ponds. We revisited estimates of climate forcing made for 1970 and 2000 for Stordalen Mire in northern Sweden and found the trend of increasing forcing continued into 2014. The Mire continued to transition from dry permafrost to sedge and open water areas, increasing by 100% and 35%, respectively, over the 45-year period, causing the net radiative forcing of Stordalen Mire to shift from negative to positive. This trend is driven by transitioning vegetation community composition, improved estimates of annual CO 2 and CH 4 exchange and a 22% increase in the IPCC's 100-year global warming potential (GWP_100) value for CH 4 . These results indicate that discontinuous permafrost ecosystems, while still remaining a net overall sink of C, can become a positive feedback to climate change on decadal timescales. This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.

scholarly journals The trajectory of landcover change in peatland complexes with discontinuous permafrost, northwestern Canada

2020 ◽  
Author(s):  
Olivia Carpino ◽  
Kristine Haynes ◽  
Ryan Connon ◽  
James Craig ◽  
Élise Devoie ◽  
...  
Keyword(s):  
Climate Warming ◽  
Permafrost Zone ◽  
High Rate ◽  
Permafrost Thaw ◽  
Landcover Change ◽  
Plateau Wetland ◽  
Discontinuous Permafrost ◽  
Local Mean ◽  
Time Substitution ◽  
Rapid Transformation

Abstract. The discontinuous permafrost zone is undergoing rapid transformation as a result of unprecedented permafrost thaw brought on by circumpolar climate warming. Rapid climate warming over recent decades has significantly decreased the area underlain by permafrost in peatland complexes. It has catalyzed extensive landscape transitions in the Taiga Plains of northwestern Canada, transforming forest-dominated landscapes to those that are wetland-dominated. The high rate and large spatial extent of this thaw-induced landcover transformation indicates that this region is particularly sensitive to warming temperatures and will continue to respond to climatic changes and landscape disturbances. This study explores the current trajectory of landcover change across a 300 000 km2 region of northwestern Canada's discontinuous permafrost zone by presenting a space-for-time substitution that capitalizes on the region's 600 km latitudinal span. To illustrate this trajectory of change we present the distribution of peatland-rich environments that govern permafrost coverage in this region of the discontinuous permafrost zone. We also establish that relatively undisturbed forested plateau-wetland complexes dominate the region's higher latitudes, forest-wetland patchworks are most prevalent at the medial latitudes, and forested peatlands are increasingly present across lower latitudes, indicating not only a climatic gradient but also a landscape in transition as local mean temperatures increase. This study combines extensive geomatics data with ground-based meteorological and hydrological measurements to inform a new conceptual model of landscape evolution that accounts for the observed patterns of permafrost thaw-induced landcover change, and provides a basis for predicting future changes.

Modelling of long-term permafrost evolution in the discontinuous permafrost zone of North-West Siberia

2020 ◽  
Author(s):  
Ekaterina Ezhova ◽  
Ilmo Kukkonen ◽  
Elli Suhonen ◽  
Olga Ponomareva ◽  
Andrey Gravis ◽  
...  
Keyword(s):  
Snow Cover ◽  
Warm Season ◽  
Thermal Conditions ◽  
West Siberia ◽  
The Arctic ◽  
High Porosity ◽  
Permafrost Degradation ◽  
North West ◽  
Discontinuous Permafrost

<p>The rate of climate warming in North-West Siberia is among the highest in the world and this trend is especially pronounced in summer [1]. Analysis of permafrost thermal conditions in this area provides plausible scenarios of permafrost degradation also elsewhere. An increase in the summer mean temperature together with the prolongation of the warm season results in the increase of the thawing degree-days enhancing thawing of permafrost. Here we present the results of decadal temperature observations from three boreholes near Nadym, North-West Siberia. We further use the results and the observed cryolithological structure of soils in two boreholes to model the long-term evolution of the deep permafrost under two climate scenarios, RCP2.6 (climate action, fast reduction of CO<sub>2 </sub>emissions) and RCP8.5 (‘business as usual’). Both borehole sites have a topmost high-porosity, high-ice content layer of peat which helps prolonging the degradation. The main difference between the boreholes is snow cover resulting from the difference of borehole positions (one is located on the top of the hill). Our results suggest that under RCP8.5 scenario permafrost will degrade in both boreholes. On the contrary, under RCP2.6 scenario permafrost will degrade in one borehole with the deeper snow cover, where it already shows the signs of degradation. For the other borehole, the model predicts that permafrost will not degrade within the next 300 years, although the permafrost temperatures are eventually above -1°C.</p><p>[1] Frey K.E. & Smith L.C. Recent temperature and precipitation increases in West Siberia and their association with the Arctic Oscillation. Polar Research <strong>22(2)</strong>, 287–300 (2003).</p>

scholarly journals Changes in floodplain geo-ecology in the Belgian loess belt during the first millennium AD

2021 ◽  
Vol 100 ◽  
Author(s):  
Nils Broothaerts ◽  
Ward Swinnen ◽  
Renske Hoevers ◽  
Gert Verstraeten
Keyword(s):  
Human Impact ◽  
Organic Matter Content ◽  
Integrated Approach ◽  
Matter Content ◽  
Short Term ◽  
Alluvial Deposits ◽  
Lowland Rivers ◽  
Valley Side ◽  
First Millennium ◽  
River Valleys

Abstract Variation in human activities has greatly impacted the processes and intensities of erosion, sediment transport and storage throughout the Late Holocene, and many lowland rivers around the world have responded to these variations. Although this long-term process–response relationship has been established before, the effects of short-term (c.200-year) changes in human impact on lowland rivers are less well studied. Here, we followed an integrated approach whereby observations of floodplain changes are evaluated against detailed data on human impact for three lowland rivers in the Belgian loess belt: Dijle, Mombeek and Gete rivers. Pollen data were used to reconstruct changes in local and regional vegetation and to calculate human impact scores. Corings along transects and a database of c.160 radiocarbon ages were used to reconstruct geomorphic changes in the river valleys. Our results show a decrease in human impact between 200 and 800 AD, which can be related to the decreased population density in Europe during the first millennium AD. During this period, forests in the studied catchments regenerated, soil erosion decreased, hillslope–floodplain connectivity decreased due to the regeneration of valley-side vegetation barriers, and sediment input in the floodplain decreased. A reaction to this decreased human impact can be observed in the river valleys during the first millennium AD, with a regrowth of the alder carr forest and an increase in the organic matter content of the alluvial deposits with a local reactivation of peat growth. The observed trajectories of Belgian river valleys during the first millennium AD provide more insight into the sensitivity of these river valleys to short-term variations in human impact. These results can in turn be used to better estimate the effects of future changes in the catchments on the fluvial system.

scholarly journals Recent degradation of Interior Alaska permafrost mapped with ground surveys, geophysics, deep drilling, and repeat airborne LiDAR

2021 ◽  
Author(s):  
Thomas A. Douglas ◽  
Christopher A. Hiemstra ◽  
John E. Anderson ◽  
Robyn A. Barbato ◽  
Kevin L. Bjella ◽  
...  
Keyword(s):  
Active Layer ◽  
Climate Warming ◽  
Airborne Lidar ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Top Down ◽  
Bottom Up ◽  
Near Surface ◽  
Permafrost Thaw ◽  
Tussock Tundra

Abstract. Permafrost underlies one quarter of the northern hemisphere but is at increasing risk of thaw from climate warming. Recent studies across the Arctic have identified areas of rapid permafrost degradation from both top-down and lateral thaw. Of particular concern is thawing of ice rich high carbon content syngenetic yedoma permafrost like much of the permafrost in the region around Fairbanks, Alaska. With a mean annual temperature of −2 °C subtle differences in ecotype and permafrost ice and soil content control the near-surface permafrost thermal regime. Long-term measurements of the seasonally thawed active layer across central Alaska have identified an increase in permafrost thaw degradation that is expected to continue, and even accelerate, in coming decades. A major knowledge gap is relating belowground measurements of seasonal thaw, permafrost characteristics, and talik development with aboveground ecotype properties and thermokarst expansion that can readily quantify vegetation cover and track surface elevation changes over time. This study was conducted from 2013–2020 along four 400 to 500 m long transects near Fairbanks, Alaska. Repeat end of season active layer depths, near-surface permafrost temperature measurements, electrical resistivity tomography (ERT), deep (> 5 m) boreholes, and repeat airborne LiDAR were used to measure top down thaw and map thermokarst development at the sites. Our study confirms previous work using ERT to map surface thawed zones, however, our deep boreholes confirm the boundaries between frozen and thawed zones that are needed to model top down, lateral, and bottom-up thaw. At disturbed sites seasonal thaw increased up to 25 % between mid-August and early October and suggests active layer depths must be made as late in the fall season as possible because the projected increase in the summer season of just a few weeks could lead to significant additional thaw. At our sites, tussock tundra and spruce forest are associated with the lowest mean annual near-surface permafrost temperatures while mixed forest ecotypes are the warmest and exhibit the highest degree of recent temperature warming and thaw degradation. Thermokarst features and perennially thawed zones (taliks) have been identified at all sites. Our measurements, when combined with longer-term records from yedoma across the 500,000 km2 area of central Alaska show widespread initiation of near-surface permafrost thaw since roughly 2010. Using this partial area of the yedoma domain and projecting our thaw depth increases, by ecotype, across this domain we calculate 0.44 Gt of permafrost soil C have been thawed over the 7 year period, an amount equal to the yearly CO2 emissions of Australia. Since the yedoma permafrost and the variety of ecotypes at our sites represent much of the Arctic and subarctic land cover this study shows remote sensing measurements, top-down and bottom-up thermal modelling, and ground based surveys can be used predictively to identify areas of highest risk for permafrost thaw from projected future climate warming.

scholarly journals Recent degradation of interior Alaska permafrost mapped with ground surveys, geophysics, deep drilling, and repeat airborne lidar

2021 ◽  
Vol 15 (8) ◽  
pp. 3555-3575
Author(s):  
Thomas A. Douglas ◽  
Christopher A. Hiemstra ◽  
John E. Anderson ◽  
Robyn A. Barbato ◽  
Kevin L. Bjella ◽  
...  
Keyword(s):  
Active Layer ◽  
Climate Warming ◽  
Airborne Lidar ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Top Down ◽  
Bottom Up ◽  
Near Surface ◽  
Permafrost Thaw ◽  
Tussock Tundra

Abstract. Permafrost underlies one-quarter of the Northern Hemisphere but is at increasing risk of thaw from climate warming. Recent studies across the Arctic have identified areas of rapid permafrost degradation from both top-down and lateral thaw. Of particular concern is thawing syngenetic “yedoma” permafrost which is ice-rich and has a high carbon content. This type of permafrost is common in the region around Fairbanks, Alaska, and across central Alaska expanding westward to the Seward Peninsula. A major knowledge gap is relating belowground measurements of seasonal thaw, permafrost characteristics, and residual thaw layer development with aboveground ecotype properties and thermokarst expansion that can readily quantify vegetation cover and track surface elevation changes over time. This study was conducted from 2013 to 2020 along four 400 to 500 m long transects near Fairbanks, Alaska. Repeat active layer depths, near-surface permafrost temperature measurements, electrical resistivity tomography (ERT), deep (> 5 m) boreholes, and repeat airborne light detection and ranging (lidar) were used to measure top-down permafrost thaw and map thermokarst development at the sites. Our study confirms previous work using ERT to map surface thawed zones; however, our deep boreholes confirm the boundaries between frozen and thawed zones that are needed to model top-down, lateral, and bottom-up thaw. At disturbed sites seasonal thaw increased up to 25 % between mid-August and early October and suggests measurements to evaluate active layer depth must be made as late in the fall season as possible because the projected increase in the summer season of just a few weeks could lead to significant additional thaw. At our sites, tussock tundra and spruce forest are associated with the lowest mean annual near-surface permafrost temperatures while mixed-forest ecotypes are the warmest and exhibit the highest degree of recent temperature warming and thaw degradation. Thermokarst features, residual thaw layers, and taliks have been identified at all sites. Our measurements, when combined with longer-term records from yedoma across the 500 000 km2 area of central Alaska, show widespread near-surface permafrost thaw since 2010. Projecting our thaw depth increases, by ecotype, across the yedoma domain, we calculate a first-order estimate that 0.44 Pg of organic carbon in permafrost soil has thawed over the past 7 years, which, for perspective, is an amount of carbon nearly equal to the yearly CO2 emissions of Australia. Since the yedoma permafrost and the variety of ecotypes at our sites represent much of the Arctic and subarctic land cover, this study shows remote sensing measurements, top-down and bottom-up thermal modeling, and ground-based surveys can be used predictively to identify areas of the highest risk for permafrost thaw from projected future climate warming.

scholarly journals High Spatial Resolution Modeling of Climate Change Impacts on Permafrost Thermal Conditions for the Beiluhe Basin, Qinghai-Tibet Plateau

2019 ◽  
Vol 11 (11) ◽  
pp. 1294 ◽  
Author(s):  
Jing Luo ◽  
Guoan Yin ◽  
Fujun Niu ◽  
Zhanju Lin ◽  
Minghao Liu
Keyword(s):  
Climate Change ◽  
Climate Change Impacts ◽  
Tibet Plateau ◽  
Ecosystem Change ◽  
Active Layer Thickness ◽  
Climate Projections ◽  
Permafrost Degradation ◽  
Thermal Dynamics ◽  
Discontinuous Permafrost ◽  
Qinghai Tibet Plateau

Permafrost is degrading on the Qinghai-Tibet Plateau (QTP) due to climate change. Permafrost degradation can result in ecosystem changes and damage to infrastructure. However, we lack baseline data related to permafrost thermal dynamics at a local scale. Here, we model climate change impacts on permafrost from 1986 to 2075 at a high resolution using a numerical model for the Beiluhe basin, which includes representative permafrost environments of the QTP. Ground surface temperatures are derived from air temperature using an n-factor vs Normalized Differential Vegetation Index (NDVI) relationship. Soil properties are defined by field measurements and ecosystem types. The climate projections are based on long-term observations. The modelled ground temperature (MAGT) and active-layer thickness (ALT) are close to in situ observations. The results show a discontinuous permafrost distribution (61.4%) in the Beiluhe basin at present. For the past 30 years, the permafrost area has decreased rapidly, by a total of 26%. The mean ALT has increased by 0.46 m. For the next 60 years, 8.5–35% of the permafrost area is likely to degrade under different trends of climate warming. The ALT will probably increase by 0.38–0.86 m. The results of this study are useful for developing a deeper understanding of ecosystem change, permafrost development, and infrastructure development on the QTP.

Status, Changes and Impacts of Permafrost on Qinghai-Tibet Plateau

2020 ◽  
Author(s):  
Lin Zhao ◽  
Guojie Hu ◽  
Defu Zou ◽  
Ren Li ◽  
Yu Sheng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Active Layer ◽  
Climate Warming ◽  
Global Climate ◽  
Tibet Plateau ◽  
Active Layer Thickness ◽  
Permafrost Region ◽  
Permafrost Degradation ◽  
Qinghai Tibet Plateau

<p>Due to the climate warming, permafrost on the Qinghai-Tibet Plateau (QTP) was degradating in the past decades. Since its impacts on East Asian monsoon, and even on the global climate system, it is fundamental to reveal permafrost status, changes and its physical processes. Based on previous research results and new observation data, this paper reviews the characteristics of the status of permafrost on the QTP, including the active layer thickness (ALT), the spatial distribution of permafrost, permafrost temperature and thickness, as well as the ground ice and soil carbon storage in permafrost region.</p><p>The results showed that the permafrost and seasonally frozen ground area (excluding glaciers and lakes) is 1.06 million square kilometters and 1.45 million square kilometters on the QTP. The permafrost thickness varies greatly among topography, with the maximum value in mountainous areas, which could be deeper than 200 m, while the minimum value in the flat areas and mountain valleys, which could be less than 60 m. The mean value of active layer thickness is about 2.3 m. Soil temperature at 0~10 cm, 10~40 cm, 40~100 cm, 100~200 cm increased at a rate of 0.439, 0.449, 0.396, and 0.259°C/10a, respectively, from 1980 to 2015. The increasing rate of the soil temperature at the bottom of active layer was 0.486 oC/10a from 2004 to 2018.</p><p>The volume of ground ice contained in permafrost on QTP is estimated up to 1.27×10<sup>4</sup> km<sup>3</sup> (liquid water equivalent). The soil organic carbon staored in the upper 2 m of soils within the permafrost region is about 17 Pg. Most of the research results showed that the permafrost ecosystem is still a carbon sink at the present, but it might be shifted to a carbon source due to the loss of soil organic carbon along with permafrost degradation.</p><p>Overall, the plateau permafrost has undergone remarkable degradation during past decades, which are clearly proven by the increasing ALTs and ground temperature. Most of the permafrost on the QTP belongs to the unstable permafrost, meaning that permafrost over TPQ is very sensitive to climate warming. The permafrost interacts closely with water, soil, greenhouse gases emission and biosphere. Therefore, the permafrost degradation greatly affects the regional hydrology, ecology and even the global climate system.</p>

15 years of snow manipulation reveals huge impact on lowland permafrost and vegetation

2020 ◽  
Author(s):  
Margareta Johansson ◽  
Jonas Åkerman ◽  
Gesche Blume-Werry ◽  
Terry V. Callaghan ◽  
Torben R. Christensen ◽  
...  
Keyword(s):  
Snow Cover ◽  
Layer Thickness ◽  
Active Layer ◽  
Snow Depth ◽  
Bacterial Community Composition ◽  
Strong Increase ◽  
Past Century ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Significant Difference

<p>Snow depth increases observed and predicted in the sub-arctic are of critical importance for the dynamics of lowland permafrost and vegetation. Snow acts as an insulator that protects vegetation but may lead to permafrost degradation. In the Abisko area, in northernmost Sweden, there has been an increasing trend in snow depth during the last Century. Downscaled climate scenarios predict an increase in precipitation by 1.5 - 2% per decade for the coming 60 years. The observed changes in snow cover have affected peat mires in this area as thawing of permafrost, increases in active layer thickness and associated vegetation changes have been reported during the last decades. An experimental manipulation was set up at one of these lowland permafrost sites in the Abisko area (68°20’48’’N, 18°58’16’’E) 15 years ago, to simulate projected future increases in winter precipitation and to study their effect on permafrost and vegetation. The snow cover has been more than twice as thick in manipulated plots compared to control plots and it has had a large impact on permafrost and vegetation. It resulted in statistically significant differences in mean winter and minimum ground temperatures between the control and the manipulated plots. Already after three years there was a statistically significant difference between active layer thickness in the manipulated plots compared to the control plots. In 2019, the active layer thickness in the control plots were around 70 cm whereas in the manipulated plots it was 110 cm. The increased active layer thickness has led to surface subsidence due to melting of ground ice in all the manipulated plots. The increased snow thickness has prolonged the duration of the snow cover in spring with up to 22 days. However, this loss in early season photosynthesis was well compensated for by the increased absorption of PAR and higher light use efficiency throughout the whole growing seasons in the manipulated plots. Eriophorum vaginatum is a species that has been especially favored in the manipulated plots. It has increased both in number and in size. Underneath the soil surface, the roots have also been affected. There has been a strong increase in total root length and growth in the active layer, and deep roots has invaded the newly thawed permafrost in the manipulated plots. The increased active layer thickness has also had an effect on the bacterial community composition in the newly thawed areas. According to past, century-long patterns of increasing snow depth and projections of continuing increases, it is very likely that the changes in permafrost and vegetation that have been demonstrated by this experimental treatment will occur in the future under natural conditions.</p>

HEAVY METAL SPECIATION IN BOTTOM SEDIMENTS OF THE VYSHNEVOLOTSKY RESERVOIR

2018 ◽  
pp. 46-54
Author(s):  
O. A. Lipatnikova
Keyword(s):  
Heavy Metal ◽  
Organic Matter ◽  
Bottom Sediments ◽  
Metal Speciation ◽  
Organic Matter Content ◽  
Water Reservoir ◽  
Matter Content ◽  
Heavy Metal Speciation ◽  
Mobile Forms ◽  
Manganese Hydroxides

The study of heavy metal speciation in bottom sediments of the Vyshnevolotsky water reservoir is presented in this paper. Sequential selective procedure was used to determine the heavy metal speciation in bottom sediments and thermodynamic calculation — to determine ones in interstitial water. It has been shown that Mn are mainly presented in exchangeable and carbonate forms; for Fe, Zn, Pb и Co the forms are related to iron and manganese hydroxides is played an important role; and Cu and Ni are mainly associated with organic matter. In interstitial waters the main forms of heavy metal speciation are free ions for Zn, Ni, Co and Cd, carbonate complexes for Pb, fulvate complexes for Cu. Effects of particle size and organic matter content in sediments on distribution of mobile and potentially mobile forms of toxic elements have been revealed.

Sign in / Sign up

Export Citation Format

Share Document