scholarly journals Nonlinear thermal and moisture response of ice-wedge polygons to permafrost disturbance increases heterogeneity of high Arctic wetland

2016 ◽  
Vol 13 (5) ◽  
pp. 1439-1452 ◽  
Author(s):  
Etienne Godin ◽  
Daniel Fortier ◽  
Esther Lévesque
Keyword(s):  
Active Layer ◽  
Vegetation Dynamics ◽  
Arid Region ◽  
High Arctic ◽  
Permafrost Soil ◽  
Active Layer Thickness ◽  
Heterogeneous Nature ◽  
Thaw Depth ◽  
Ice Wedge ◽  
Permafrost Regions

Abstract. Low-center polygonal terrains with gentle sloping surfaces and lowlands in the high Arctic have a potential to retain water in the lower central portion of ice-wedge polygons and are considered high-latitude wetlands. Such wetlands in the continuous permafrost regions have an important ecological role in an otherwise generally arid region. In the valley of the glacier C-79 on Bylot Island (Nunavut, Canada), thermal erosion gullies were rapidly eroding the permafrost along ice wedges affecting the integrity of the polygons by breaching and collapsing the surrounding rims. Intact polygons were characterized by a relative homogeneity in terms of topography, snow cover, maximum active layer thaw depth, ground moisture content and vegetation cover (where eroded polygons responded nonlinearly to perturbations, which resulted in differing conditions in the latter elements). The heterogeneous nature of disturbed terrains impacted active layer thickness, ground ice aggradation in the upper portion of permafrost, soil moisture, vegetation dynamics and carbon storage.

scholarly journals Nonlinear thermal and moisture dynamics of high Arctic wetland polygons following permafrost disturbance

2015 ◽  
Vol 12 (14) ◽  
pp. 11797-11831 ◽  
Author(s):  
E. Godin ◽  
D. Fortier ◽  
E. Lévesque
Keyword(s):  
Active Layer ◽  
Arid Region ◽  
High Arctic ◽  
Permafrost Soil ◽  
Active Layer Thickness ◽  
Green House Gas ◽  
Heterogeneous Nature ◽  
Thaw Depth ◽  
Moisture Dynamics ◽  
Permafrost Regions

Abstract. Low-centre polygonal terrain developing within gentle sloping surfaces and lowlands in the high Arctic have a potential to retain snowmelt water in their bowl-shaped centre and as such are considered high latitude wetlands. Such wetlands in the continuous permafrost regions have an important ecological role in an otherwise generally arid region. In the valley of the glacier C-79 on Bylot Island (Nunavut, Canada), thermal erosion gullies are rapidly eroding the permafrost along ice wedges affecting the integrity of the polygons by breaching and collapsing the surrounding rims. While intact polygons were characterized by a relative homogeneity (topography, snow cover, maximum active layer thaw depth, ground moisture content, vegetation cover), eroded polygons had a non-linear response for the same elements following their perturbation. The heterogeneous nature of disturbed terrains impacts active layer thickness, ground ice aggradation in the upper portion of permafrost, soil moisture and vegetation dynamics, carbon storage and terrestrial green-house gas emissions.

scholarly journals The influence of climate and hydrological variables on opposite anomaly in active-layer thickness between Eurasian and North American watersheds

2013 ◽  
Vol 7 (2) ◽  
pp. 631-645 ◽  
Author(s):  
H. Park ◽  
J. Walsh ◽  
A. N. Fedorov ◽  
A. B. Sherstiukov ◽  
Y. Iijima ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
North American ◽  
Land Surface ◽  
Snow Depth ◽  
The Arctic ◽  
Surface Model ◽  
Active Layer Thickness ◽  
Hydrological Variables ◽  
Permafrost Regions

Abstract. This study not only examined the spatiotemporal variations of active-layer thickness (ALT) in permafrost regions during 1948–2006 over the terrestrial Arctic regions experiencing climate changes, but also identified the associated drivers based on observational data and a simulation conducted by a land surface model (CHANGE). The focus on the ALT extends previous studies that have emphasized ground temperatures in permafrost regions. The Ob, Yenisey, Lena, Yukon, and Mackenzie watersheds are foci of the study. Time series of ALT in Eurasian watersheds showed generally increasing trends, while the increase in ALT in North American watersheds was not significant. However, ALT in the North American watersheds has been negatively anomalous since 1990 when the Arctic air temperature entered into a warming phase. The warming temperatures were not simply expressed to increases in ALT. Since 1990 when the warming increased, the forcing of the ALT by the higher annual thawing index (ATI) in the Mackenzie and Yukon basins has been offset by the combined effects of less insulation caused by thinner snow depth and drier soil during summer. In contrast, the increasing ATI together with thicker snow depth and higher summer soil moisture in the Lena contributed to the increase in ALT. The results imply that the soil thermal and moisture regimes formed in the pre-thaw season(s) provide memory that manifests itself during the summer. The different ALT anomalies between Eurasian and North American watersheds highlight increased importance of the variability of hydrological variables.

Ground-penetrating radar-derived measurements of active-layer thickness on the landscape scale with sparse calibration at Toolik and Happy Valley, Alaska

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. H9-H19 ◽  
Author(s):  
Albert Chen ◽  
Andrew D. Parsekian ◽  
Kevin Schaefer ◽  
Elchin Jafarov ◽  
Santosh Panda ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Ground Penetrating Radar ◽  
Empirical Relationship ◽  
Monitoring Network ◽  
Active Layer Thickness ◽  
Antenna Coupling ◽  
Thaw Depth ◽  
Ground Penetrating ◽  
Happy Valley

Active-layer thickness (ALT) is an important parameter for studying surface energy balance, ecosystems, and hydrologic processes in cold regions. We measured ALT along 10 routes with lengths ranging from 0.7 to 6.9 km located on the Alaska North Slope near Toolik Lake and the Happy Valley airstrip (between 68.475° and 69.150°N, and [Formula: see text] and [Formula: see text]). Using a ground-penetrating radar (GPR) system in a common-offset configuration, we measured the two-way traveltimes from the surface to the bottom of the active layer at the end of summer, when the thaw depth was greatest. We used 500 and 800 MHz antennas; the 500 MHz antenna provided suitable vertical resolution, while producing more unambiguous active-layer reflections in the presence of nonideal antenna coupling and active layer inhomogeneity. We derived ALT measurements and their uncertainties from GPR two-way traveltimes, with mechanical probing for velocity calibration. Using an empirical relationship between the wave velocity and soil volumetric water content (VWC), we found that the velocities were consistent with soil VWCs ranging from 0.46 to 0.63. In 31% of traces, the permafrost table horizon was identifiable, resulting in ALT measurements with uncertainties of generally less than 25%. The average ALT was 48.1 cm, with a standard deviation of 16.1 cm. We found distinct patterns of ALT spatial variability at different sites and different length scales. At some sites, the ALT at one point was effectively uncorrelated with ALT at other points separated by lag distances as small as tens of meters; for other sites, there was correlation at lag distances up to approximately 400 m. The ALT statistics were similar to nearby long-term in situ ALT measurements from the Circumpolar Active Layer Monitoring Network, through which yearly ALT measurements have been made since 1990.

scholarly journals Spatiotemporal Changes in Active Layer Thickness under Contemporary and Projected Climate in the Northern Hemisphere

2017 ◽  
Vol 31 (1) ◽  
pp. 251-266 ◽  
Author(s):  
Xiaoqing Peng ◽  
Tingjun Zhang ◽  
Oliver W. Frauenfeld ◽  
Kang Wang ◽  
Dongliang Luo ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Northern Hemisphere ◽  
Active Layer ◽  
Extreme Values ◽  
Primary Objective ◽  
Climatic Research Unit ◽  
Active Layer Thickness ◽  
Detailed Knowledge ◽  
Permafrost Regions

Abstract Variability of active layer thickness (ALT) in permafrost regions is critical for assessments of climate change, water resources, and engineering applications. Detailed knowledge of ALT variations is also important for studies on ecosystem, hydrological, and geomorphological processes in cold regions. The primary objective of this study is therefore to provide a comprehensive 1971–2000 climatology of ALT and its changes across the entire Northern Hemisphere from 1850 through 2100. To accomplish this, in situ observations, the Stefan solution based on a thawing index, and the edaphic factor (E factor) are employed to calculate ALT. The thawing index is derived from (i) the multimodel ensemble mean of 16 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) over 1850–2005, (ii) three representative concentration pathways (RCP2.6, RCP4.5, and RCP8.5) for 2006–2100, and (iii) Climatic Research Unit (CRU) gridded observations for 1901–2014. The results show significant spatial variability in in situ ALT that generally ranges from 40 to 320 cm, with some extreme values of 900 cm in the Alps. The differences in the ALT climatology between the three RCPs and the historical experiments ranged from 0 to 200 cm. The biggest increases, of 120–200 cm, are on the Qinghai–Tibetan Plateau, while the smallest increases of less than 20 cm are in Alaska. Averaged over all permafrost regions, mean ALT from CMIP5 increased significantly at 0.57 ± 0.04 cm decade−1 during 1850–2005, while 2006–2100 projections show ALT increases of 0.77 ± 0.08 cm decade−1 for RCP2.6, 2.56 ± 0.07 cm decade−1 for RCP4.5, and 6.51 ± 0.07 cm decade−1 for RCP8.5.

scholarly journals Impact of lateral groundwater flow on hydrothermal conditions of the active layer in a high-Arctic hillslope setting

2021 ◽  
Vol 15 (10) ◽  
pp. 4853-4871
Author(s):  
Alexandra Hamm ◽  
Andrew Frampton
Keyword(s):  
Heat Loss ◽  
Active Layer ◽  
High Arctic ◽  
Control Case ◽  
Catchment Scale ◽  
Hydrothermal Conditions ◽  
Additional Energy ◽  
Ground Temperatures ◽  
Thaw Depth ◽  
Lower Heat

Abstract. Modeling the physical state of permafrost landscapes is a crucial addition to field observations in order to understand the feedback mechanisms between permafrost and the atmosphere within a warming climate. A common hypothesis in permafrost modeling is that vertical heat conduction is most relevant to derive subsurface temperatures. While this approach is mostly applicable to flat landscapes with little topography, landscapes with more topography are subject to lateral flow processes as well. With our study, we contribute to the growing body of evidence that lateral surface and subsurface processes can have a significant impact on permafrost temperatures and active layer properties. We use a numerical model to simulate two idealized hillslopes (a steep and a medium case) with inclinations that can be found in Adventdalen, Svalbard, and compare them to a flat control case. We find that ground temperatures within the active layer uphill are generally warmer than downhill in both slopes (with a difference of up to ∼0.8 ∘C in the steep and ∼0.6 ∘C in the medium slope). Further, the slopes are found to be warmer in the uphill section and colder in the base of the slopes compared to the flat control case. As a result, maximum thaw depth increases by about 5 cm from the flat (0.98 m) to the medium (1.03 m) and the steep slope (1.03 m). Uphill warming on the slopes is explained by overall lower heat capacity, additional energy gain through infiltration, and lower evaporation rates due to drier conditions caused by subsurface runoff. The major governing process causing the cooling on the downslope side is heat loss to the atmosphere through evaporation in summer and enhanced heat loss in winter due to wetter conditions and resulting increased thermal conductivity. On a catchment scale, these results suggest that temperature distributions in sloped terrain can vary considerably compared to flat terrain, which might impact the response of subsurface hydrothermal conditions to ongoing climate change.

Climate warming and active layer thaw in the boreal and tundra environments of the Mackenzie Valley

2007 ◽  
Vol 44 (6) ◽  
pp. 733-743 ◽  
Author(s):  
Ming-ko Woo ◽  
Michael Mollinga ◽  
Sharon L Smith
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Climate Warming ◽  
Probability Distributions ◽  
Organic Layer ◽  
Active Layer Thickness ◽  
Near Surface ◽  
Ground Temperatures ◽  
Thaw Depth ◽  
Mineral Soils

The variability of maximum active layer thickness in boreal and tundra environments has important implications for hydrological processes, terrestrial and aquatic ecosystems, and the integrity of northern infrastructure. For most planning and management purposes, the long-term probability distribution of active layer thickness is of primary interest. A robust method is presented to calculate maximum active layer thickness, employing the Stefan equation to compute phase change of moisture in soils and using air temperature as the sole climatic forcing variable. Near-surface ground temperatures (boundary condition for the Stefan equation) were estimated based on empirical relationships established for several sites in the Mackenzie valley. Simulations were performed for typically saturated mineral soils, overlain with varying thickness of peat in boreal and tundra environments. The probability distributions of simulated maximum active layer thickness encompass the range of measured thaw depths provided by field data. The effects of climate warming under A2 and B2 scenarios for 2050 and 2100 were investigated. Under the A2 scenario in 2100, the simulated median thaw depth under a thin organic cover may increase by 0.3 m, to reach 1 m depth for a tundra site and 1.6 m depth for a boreal site. The median thaw depth in 2100 is dampened by about 50% under a 1 m thick organic layer. Without an insulating organic cover, thaw penetration can increase to reach 1.7 m at the tundra site. The simulations provide quantitative support that future thaw penetration in permafrost terrain will deepen differentially depending on location and soil.

scholarly journals The ERA5-Land Soil-Temperature Bias in Permafrost Regions

2020 ◽  
Author(s):  
Bin Cao ◽  
Stephan Gruber ◽  
Donghai Zheng ◽  
Xin Li
Keyword(s):  
Soil Temperature ◽  
Layer Thickness ◽  
Active Layer ◽  
Active Layer Thickness ◽  
Near Surface ◽  
Average Bias ◽  
Warm Bias ◽  
Temperature Bias ◽  
Low Latitudes ◽  
Permafrost Regions

Abstract. ERA5-Land (ERA5L) is a reanalysis product derived by running the land component of ERA5 at increased resolution. This study evaluates its soil temperature in permafrost regions based on observations and published permafrost products. Soil in ERA5L is predicted too warm in northern Canada and Alaska, but too cold in mid-low latitudes, leading to an average bias of −0.08 °C. The warm bias of ERA5L soil is stronger in winter than in other seasons. Diagnosed from its soil temperature, ERA5L overestimates active-layer thickness and underestimates near-surface (

scholarly journals PERICLIMv1.0: a model deriving palaeo-air temperatures from thaw depth in past permafrost regions

2021 ◽  
Vol 14 (4) ◽  
pp. 1865-1884
Author(s):  
Tomáš Uxa ◽  
Marek Křížek ◽  
Filip Hrbáček
Keyword(s):  
Air Temperature ◽  
Cold Climate ◽  
Active Layer Thickness ◽  
Full Potential ◽  
Temperature Characteristics ◽  
Air Temperatures ◽  
Climate Controls ◽  
Thaw Depth ◽  
Temperature Records ◽  
Permafrost Regions

Abstract. Periglacial features, such as various kinds of patterned ground, cryoturbations, frost wedges, solifluction structures, and blockfields, are among the most common relics of cold climate periods, which repetitively occurred throughout the Quaternary. As such, they are widespread archives of past environmental conditions. Climate controls on the development of most periglacial features, however, remain poorly known, and thus empirical palaeo-climate reconstructions based on them have limited validity. This study presents and evaluates a simple new inverse modelling scheme called PERICLIMv1.0 (PERIglacial CLIMate) that derives palaeo-air temperature characteristics related to the palaeo-active-layer thickness, which can be recognized using many relict periglacial features found in past permafrost regions. The evaluation against modern temperature records showed that the model reproduces air temperature characteristics with average errors ≤1.3 ∘C. The past mean annual air temperature modelled experimentally for two sites in the Czech Republic hosting relict cryoturbation structures was between -7.0±1.9 and -3.2±1.5 ∘C, which is well in line with earlier reconstructions utilizing various palaeo-archives. These initial results are promising and suggest that the model could become a useful tool for reconstructing Quaternary palaeo-environments across vast areas of mid-latitudes and low latitudes where relict periglacial assemblages frequently occur, but their full potential remains to be exploited.

scholarly journals The new database of the Global Terrestrial Network for Permafrost (GTN-P)

2015 ◽  
Vol 7 (2) ◽  
pp. 245-259 ◽  
Author(s):  
B. K. Biskaborn ◽  
J.-P. Lanckman ◽  
H. Lantuit ◽  
K. Elger ◽  
D. A. Streletskiy ◽  
...  
Keyword(s):  
Active Layer ◽  
Voronoi Tessellation ◽  
Extreme Temperature ◽  
Data Management System ◽  
Active Layer Thickness ◽  
Global Models ◽  
Sample Distribution ◽  
Site Distribution ◽  
Terrestrial Network ◽  
Permafrost Regions

Abstract. The Global Terrestrial Network for Permafrost (GTN-P) provides the first dynamic database associated with the Thermal State of Permafrost (TSP) and the Circumpolar Active Layer Monitoring (CALM) programs, which extensively collect permafrost temperature and active layer thickness (ALT) data from Arctic, Antarctic and mountain permafrost regions. The purpose of GTN-P is to establish an early warning system for the consequences of climate change in permafrost regions and to provide standardized thermal permafrost data to global models. In this paper we introduce the GTN-P database and perform statistical analysis of the GTN-P metadata to identify and quantify the spatial gaps in the site distribution in relation to climate-effective environmental parameters. We describe the concept and structure of the data management system in regard to user operability, data transfer and data policy. We outline data sources and data processing including quality control strategies based on national correspondents. Assessment of the metadata and data quality reveals 63 % metadata completeness at active layer sites and 50 % metadata completeness for boreholes. Voronoi tessellation analysis on the spatial sample distribution of boreholes and active layer measurement sites quantifies the distribution inhomogeneity and provides a potential method to locate additional permafrost research sites by improving the representativeness of thermal monitoring across areas underlain by permafrost. The depth distribution of the boreholes reveals that 73 % are shallower than 25 m and 27 % are deeper, reaching a maximum of 1 km depth. Comparison of the GTN-P site distribution with permafrost zones, soil organic carbon contents and vegetation types exhibits different local to regional monitoring situations, which are illustrated with maps. Preferential slope orientation at the sites most likely causes a bias in the temperature monitoring and should be taken into account when using the data for global models. The distribution of GTN-P sites within zones of projected temperature change show a high representation of areas with smaller expected temperature rise but a lower number of sites within Arctic areas where climate models project extreme temperature increase. GTN-P metadata used in this paper are available at doi:10.1594/PANGAEA.842821.

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