scholarly journals Validation of Permafrost Active Layer Estimates from Airborne SAR Observations

2021 ◽  
Vol 13 (15) ◽  
pp. 2876
Author(s):  
Andrew D. Parsekian ◽  
Richard H. Chen ◽  
Roger J. Michaelides ◽  
Taylor D. Sullivan ◽  
Leah K. Clayton ◽  
...  
Keyword(s):  
Active Layer ◽  
Remotely Sensed ◽  
Validation Dataset ◽  
Active Layer Thickness ◽  
Field Observations ◽  
Elemental Cycling ◽  
Airborne Sar ◽  
Minimal Bias ◽  
Average Uncertainty ◽  
Permafrost Regions

In permafrost regions, active layer thickness (ALT) observations measure the effects of climate change and predict hydrologic and elemental cycling. Often, ALT is measured through direct ground-based measurements. Recently, synthetic aperture radar (SAR) measurements from airborne platforms have emerged as a method for observing seasonal thaw subsidence, soil moisture, and ALT in permafrost regions. This study validates airborne SAR-derived ALT estimates in three regions of Alaska, USA using calibrated ground penetrating radar (GPR) geophysical data. The remotely sensed ALT estimates matched the field observations within uncertainty for 79% of locations. The average uncertainty for the GPR-derived ALT validation dataset was 0.14 m while the average uncertainty for the SAR-derived ALT in pixels coincident with GPR data was 0.19 m. In the region near Utqiaġvik, the remotely sensed ALT appeared slightly larger than field observations while in the Yukon-Kuskokwim Delta region, the remotely sensed ALT appeared slightly smaller than field observations. In the northern foothills of the Brooks Range, near Toolik Lake, there was minimal bias between the field data and remotely sensed estimates. These findings suggest that airborne SAR-derived ALT estimates compare well with in situ probing and GPR, making SAR an effective tool to monitor permafrost measurements.

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.

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 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 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 Remotely Sensed Active Layer Thickness (ReSALT) at Barrow, Alaska Using Interferometric Synthetic Aperture Radar

2015 ◽  
Vol 7 (4) ◽  
pp. 3735-3759 ◽  
Author(s):  
Kevin Schaefer ◽  
Lin Liu ◽  
Andrew Parsekian ◽  
Elchin Jafarov ◽  
Albert Chen ◽  
...  
Keyword(s):  
Synthetic Aperture Radar ◽  
Layer Thickness ◽  
Active Layer ◽  
Remotely Sensed ◽  
Synthetic Aperture ◽  
Active Layer Thickness ◽  
Interferometric Synthetic Aperture Radar ◽  
Aperture Radar

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 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.

scholarly journals Modelling and mapping climate change impacts on permafrost at high spatial resolution for a region with complex terrain

2012 ◽  
Vol 6 (6) ◽  
pp. 4599-4636
Author(s):  
Y. Zhang ◽  
X. Wang ◽  
R. Fraser ◽  
I. Olthof ◽  
W. Chen ◽  
...  
Keyword(s):  
Climate Change ◽  
Layer Thickness ◽  
Spatial Resolution ◽  
Active Layer ◽  
Complex Terrain ◽  
High Spatial Resolution ◽  
Climate Change Impacts ◽  
Active Layer Thickness ◽  
Topographic Effects ◽  
Field Observations

Abstract. Most spatial modelling of climate change impacts on permafrost has been conducted at half-degree latitude/longitude or coarser spatial resolution. At such coarse resolution, topographic effects on insolation cannot be considered accurately and the modelling results are difficult to use for land managers and ecologists. Here we mapped climate change impacts on permafrost from 1968 to 2100 at 10 m resolution using a process-based model for Ivvavik National Park, a region with complex terrain in northern Yukon, Canada. Soil and drainage conditions were defined based on ecosystem types, which were mapped using SPOT imagery, a digital elevation model and field observations. Leaf area indices were mapped using Landsat imagery and the ecosystem map. Climate distribution was estimated based on elevation and station observations, and the effects of topography on insolation were estimated based on slope, aspect and viewshed. To reduce computation time, we clustered climate distribution and topographic effects on insolation into discrete types. The modelled active-layer thickness and permafrost distribution were comparable with field observations and other studies, demonstrating that it is practical to model and map climate change impacts on permafrost at high spatial resolution for areas with complex terrain. The map portrayed large variations in active-layer thickness, with ecosystem types being the most important controlling variable, followed by climate, including topographic effects on insolation. This study also shows that climate scenarios and ground conditions are the major sources of uncertainty for high resolution permafrost mapping.

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