scholarly journals Permafrost distribution and conditions at the headwalls of two receding glaciers (Schladming and Hallstatt glaciers) in the Dachstein Massif, Northern Calcareous Alps, Austria

2020 ◽  
Vol 14 (4) ◽  
pp. 1173-1186
Author(s):  
Matthias Rode ◽  
Oliver Sass ◽  
Andreas Kellerer-Pirklbauer ◽  
Harald Schnepfleitner ◽  
Christoph Gitschthaler
Keyword(s):  
Active Layer ◽  
Ground Surface ◽  
Ice Age ◽  
Small Scale ◽  
Active Layer Thickness ◽  
High Mountain ◽  
Glacier Surface ◽  
Near Surface ◽  
Rock Stability ◽  
Multi Method Approach

Abstract. Permafrost distribution in rock walls surrounding receding glaciers is an important factor in rock stability and rock wall retreat. We investigated bedrock permafrost distribution in the Dachstein Massif, Austria, reaching up to 2995 m a.s.l. The occurrence, thickness and thermal regime of permafrost at this partly glaciated mountain massif are scarcely known. We applied a multi-method approach with continuous ground surface and near-surface temperature monitoring (GST), measurement of the bottom temperature of the winter snow cover (BTS), electrical resistivity tomography (ERT), airborne photogrammetry, topographic maps, visual observations, and field mapping. Our research focused on several steep rock walls consisting of massive limestone above receding glaciers exposed to different slope aspects at elevations between ca. 2600 and 2700 m a.s.l. We aimed to quantify the distribution and conditions of bedrock permafrost particularly at the transition zone between the present glacier surface and the adjacent rock walls. According to our ground temperature data, permafrost is mainly found at north-facing rock walls. At south-east-facing rock walls, permafrost is probable only in very favourable cold conditions at radiation-sheltered higher elevations (>2700 m a.s.l.). ERT measurements reveal high resistivities (>30 000 Ω m) at ≥1.5 m depth at north-exposed slopes (highest values >100 kΩ m). Deducted from laboratory studies and additional small-scale ERT measurements, these values indicate permafrost existence. Permafrost bodies were found at several rock walls independent of investigated slope orientation; however, particularly large permafrost bodies were found at north-exposed sites. Furthermore, at vertical survey lines, a pronounced imprint of the former Little Ice Age (LIA) ice margin was detected. Resistivities above and below the LIA line are markedly different. At the LIA glacier surface, the highest resistivities and lowest active-layer thicknesses were observed. The active-layer thickness increases downslope from this zone. Permafrost below the LIA line could be due to permafrost aggradation or degradation; however, the spatial patterns of frozen rock point to permafrost aggradation following glacier surface lowering or retreat. This finding is significant for permafrost and cirque erosion studies in terms of frost-influence weathering in similar high-mountain settings.

scholarly journals Permafrost thaw and ground settlement considering long-term climate impact in northern Alaska

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Zhaohui Joey Yang ◽  
Kannon C. Lee ◽  
Haibo Liu
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Climate Model ◽  
Ground Surface ◽  
Active Layer Thickness ◽  
Near Surface ◽  
Surface Conditions ◽  
Ice Content ◽  
Northern Alaska

AbstractAlaska’s North Slope is predicted to experience twice the warming expected globally. When summers are longer and winters are shortened, ground surface conditions in the Arctic are expected to change considerably. This is significant for Arctic Alaska, a region that supports surface infrastructure such as energy extraction and transport assets (pipelines), buildings, roadways, and bridges. Climatic change at the ground surface has been shown to impact soil layers beneath through the harmonic fluctuation of the active layer, and warmer air temperature can result in progressive permafrost thaw, leading to a deeper active layer. This study attempts to assess climate change based on the climate model data from the fifth phase of the Coupled Model Intercomparison Project and its impact on a permafrost environment in Northern Alaska. The predicted air temperature data are analyzed to evaluate how the freezing and thawing indices will change due to climate warming. A thermal model was developed that incorporated a ground surface condition defined by either undisturbed intact tundra or a gravel fill surface and applied climate model predicted air temperatures. Results indicate similar fluctuation in active layer thickness and values that fall within the range of minimum and maximum readings for the last quarter-century. It is found that the active layer thickness increases, with the amount depending on climate model predictions and ground surface conditions. These variations in active layer thickness are then analyzed by considering the near-surface frozen soil ice content. Analysis of results indicates that thaw strain is most significant in the near-surface layers, indicating that settlement would be concurrent with annual thaw penetration. Moreover, ice content is a major factor in the settlement prediction. This assessment methodology, after improvement, and the results can help enhance the resilience of the existing and future new infrastructure in a changing Arctic environment.

scholarly journals Permafrost Thaw and Ground Settlement Considering Long-Term Climate Impact in Northern Alaska

2021 ◽  
Author(s):  
Joey Yang ◽  
Kannon C. Lee ◽  
Haibo Liu
Keyword(s):  
Active Layer ◽  
Air Temperature ◽  
Climate Model ◽  
Ground Surface ◽  
North Slope ◽  
Active Layer Thickness ◽  
Near Surface ◽  
Surface Conditions ◽  
Air Temperatures ◽  
Ice Content

Abstract Alaska’s North Slope is predicted to experience twice the warming expected globally. When summers are longer and winters are shortened, ground surface conditions in the Arctic are expected to change considerably. This is significant for Arctic Alaska, a region that supports surface infrastructure such as energy extraction and transport assets (pipelines), buildings, roadways, and bridges. Climatic change at the ground surface has been shown to infiltrate soil layers beneath through the harmonic fluctuation of the active layer. Past studies found that warmer air temperature resulted in increasingly deeper thaw, leading to a deeper active layer. This study attempts to assess climate change based on the climate model data from the fifth phase of the Coupled Model Intercomparison Project and its impact on a study site on the North Slope. The predicted air temperature data are analyzed to evaluate how the freezing and thawing indices will change due to climate warming. A thermal model was developed that incorporated a ground surface condition defined by either undisturbed intact tundra or a gravel fill surface and applied climate model predicted air temperatures. Results indicate similar fluctuation in active layer thickness and values that fall within the range of minimum and maximum readings. It is found that the active layer thickens when the ground surface is either gravel fill or undisturbed tundra, but its thickness varies based on climate model predictions. These variations in active layer thickness are then analyzed by considering the near-surface frozen soil ice content. Analysis of results indicates that strain is most significant in the near-surface layers during thaw, indicating that settlement would be concurrent with annual thaw penetration. From this study, the climate model predicted air temperatures for a warming Arctic suggest that the thaw of near-surface frozen ground is largely dependent on ground surface conditions and the thermal properties of soil. Moreover, ice content is a major factor in the settlement predictions on Alaska’s North Slope. This study's results can help enhance the resilience of the existing and future new infrastructure in a changing Arctic environment.

scholarly journals Warming permafrost and active layer variability at Cime Bianche, Western Alps

2014 ◽  
Vol 8 (4) ◽  
pp. 4033-4074
Author(s):  
P. Pogliotti ◽  
M. Guglielmin ◽  
E. Cremonese ◽  
U. Morra di Cella ◽  
G. Filippa ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Snow Cover ◽  
Layer Thickness ◽  
Active Layer ◽  
Ground Surface ◽  
Small Scale ◽  
Active Layer Thickness ◽  
Spatial And Temporal Variability ◽  
Monitoring Site ◽  
Surface Temperatures

Abstract. The objective of this paper is to provide a first synthesis on the state and recent evolution of permafrost at the monitoring site of Cime Bianche (3100 m a.s.l.). The analysis is based on seven years of ground temperatures observations in two boreholes and seven surface points. The analysis aims to quantify the spatial and temporal variability of ground surface temperatures in relation to snow cover, the small scale spatial variability of the active layer thickness and the warming trends on deep permafrost temperatures. Results show that the heterogeneity of snow cover thickness, both in space and time, is the main factor controlling ground surface temperatures and leads to a mean range of spatial variability (2.5±0.15°C) which far exceeds the mean range of observed inter-annual variability (1.6±0.12°C). The active layer thickness measured in two boreholes 30 m apart, shows a mean difference of 2.03±0.15 m with the active layer of one borehole consistently lower. As revealed by temperature analysis and geophysical soundings, such a difference is mainly driven by the ice/water content in the sub-surface and not by the snow cover regimes. The analysis of deep temperature time series reveals that permafrost is warming. The detected linear trends are statistically significant starting from depth below 8 m, span the range 0.1–0.01°C year−1 and decrease exponentially with depth. Our findings are discussed in the context of the existing literature.

scholarly journals Permafrost distribution and conditions at the headwalls of two receding glaciers (Schladminger and Hallstadt glaciers) in the Dachstein Massif, Northern Calcareous Alps, Austria

2019 ◽  
Author(s):  
Matthias Rode ◽  
Harald Schnepfleitner ◽  
Oliver Sass ◽  
Andreas Kellerer-Pirklbauer ◽  
Christoph Gitschthaler
Keyword(s):  
Transition Zone ◽  
Slope Failure ◽  
Ground Surface ◽  
Northern Calcareous Alps ◽  
Small Scale ◽  
European Alps ◽  
Glacier Surface ◽  
Near Surface ◽  
Northern Calcareous ◽  
Discontinuous Permafrost

Abstract. Permafrost distribution in rockwalls surrounding receding glaciers is an important factor for rock slope failure and rockwall retreat. The Northern Calcareous Alps of the Eastern European Alps form a geological and climatological transition zone between the Alpine Foreland and the Central Alps. Some of highest summits of this area are located in the Dachstein Massif (47°28'32'' N, 13°36'23'' E) in Austria reaching up to 2995 m a.s.l. Occurrence, thickness and thermal regime of permafrost at this partly glaciated mountain massif are scarcely known and related knowledge is primarily based on regional modeling approaches. We applied a multi method approach with continuous ground surface and near-surface temperature monitoring, measurement of bottom temperature of the winter snow cover, electrical resistivity tomography/ERT, airborne photogrammetry, topographic maps, visual observations and field mapping for permafrost assessment. Our research focused on steep rockwalls consisting of massive limestone above several receding glaciers exposed to different slope aspects at elevations between c.2600–2700 m a.s.l. We aimed to quantify distribution and conditions of bedrock permafrost particularly at the transition zone between the present glacier surface and the adjacent rockwalls. Low ground temperature data suggest that permafrost is mainly found at cold, north exposed rockwalls. At southeast exposed rockwalls permafrost is only expected in very favourable cold conditions at shadowed higher elevations (2700 m a.s.l.). ERT measurements reveal high resistivities (> 30.000 ohm.m) at ≥ 1.5 m depth at north-exposed slopes (highest measured resistivity values > 100 kohm.m). Based on laboratory studies and additional measurements with small scale ERT, these values indicate permafrost existence. Such permafrost bodies were found in the rockwalls at all measurement sites independent of investigated slope orientation. ERT data indicate large permafrost bodies at north exposed sites whereas discontinuous permafrost bodies prevail at northwest and northeast facing rockwalls. In summary, permafrost distribution and conditions around the headwalls of the glaciers of the Dachstein Massif is primarily restricted to the north exposed sector, whereas at the south exposed sector permafrost is restricted to the summit region.

scholarly journals Warming permafrost and active layer variability at Cime Bianche, Western European Alps

2015 ◽  
Vol 9 (2) ◽  
pp. 647-661 ◽  
Author(s):  
P. Pogliotti ◽  
M. Guglielmin ◽  
E. Cremonese ◽  
U. Morra di Cella ◽  
G. Filippa ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Snow Cover ◽  
Layer Thickness ◽  
Active Layer ◽  
Ground Surface ◽  
Small Scale ◽  
Active Layer Thickness ◽  
Spatial And Temporal Variability ◽  
Monitoring Site ◽  
European Alps

Abstract. The objective of this paper is to provide a first synthesis on the state and recent evolution of permafrost at the monitoring site of Cime Bianche (3100 m a.s.l.) on the Italian side of the Western Alps. The analysis is based on 7 years of ground temperature observations in two boreholes and seven surface points. The analysis aims to quantify the spatial and temporal variability of ground surface temperature in relation to snow cover, the small-scale spatial variability of the active layer thickness and current temperature trends in deep permafrost. Results show that the heterogeneity of snow cover thickness, both in space and time, is the main factor controlling ground surface temperatures and leads to a mean range of spatial variability (2.5 ± 0.1 °C) which far exceeds the mean range of observed inter-annual variability (1.6 ± 0.1 °C). The active layer thickness measured in two boreholes at a distance of 30 m shows a mean difference of 2.0 ± 0.1 m with the active layer of one borehole consistently deeper. As revealed by temperature analysis and geophysical soundings, such a difference is mainly driven by the ice/water content in the sub-surface and not by the snow cover regimes. The analysis of deep temperature time series reveals that permafrost is warming. The detected trends are statistically significant starting from a depth below 8 m with warming rates between 0.1 and 0.01 °C yr−1.

scholarly journals An integrated approach to investigate climate-driven rockfall occurrence in high alpine slopes: the Bessanese glacial basin, Western Italian Alps

2020 ◽  
Vol 17 (11) ◽  
pp. 2591-2610
Author(s):  
Cristina Viani ◽  
Marta Chiarle ◽  
Roberta Paranunzio ◽  
Andrea Merlone ◽  
Chiara Musacchio ◽  
...  
Keyword(s):  
Climate Change ◽  
Active Layer ◽  
Integrated Approach ◽  
Slope Instability ◽  
High Mountain ◽  
Positive Temperature ◽  
Rock Slopes ◽  
Italian Alps ◽  
Near Surface ◽  
Basin Scale

Abstract Rockfalls are one of the most common instability processes in high mountains. They represent a relevant issue, both for the risks they represent for (infra) structures and frequentation, and for their potential role as terrestrial indicators of climate change. This study aims to contribute to the growing topic of the relationship between climate change and slope instability at the basin scale. The selected study area is the Bessanese glacial basin (Western Italian Alps) which, since 2016, has been specifically equipped, monitored and investigated for this purpose. In order to provide a broader context for the interpretation of the recent rockfall events and associated climate conditions, a cross-temporal and integrated approach has been adopted. For this purpose, geomorphological investigations (last 100 years), local climate (last 30 years) and near-surface rock/air temperatures analyses, have been carried out. First research outcomes show that rockfalls occurred in two different geomorphological positions: on rock slopes in permafrost condition, facing from NW to NE and/or along the glacier margins, on rock slopes uncovered by the ice in the last decades. Seasonal thaw of the active layer and/or glacier debutressing can be deemed responsible for slope failure preparation. With regard to timing, almost all dated rock falls occurred in summer. For the July events, initiation may have been caused by a combination of rapid snow melt and enhanced seasonal thaw of the active layer due to anomalous high temperatures, and rainfall. August events are, instead, associated with a significant positive temperature anomaly on the quarterly scale, and they can be ascribed to the rapid and/or in depth thaw of the permafrost active layer. According to our findings, we can expect that in the Bessanese glacierized basin, as in similar high mountain areas, climate change will cause an increase of slope instability in the future. To fasten knowledge deepening, we highlight the need for a growth of a network of high elevation experimental sites at the basin scale, and the definition of shared methodological and measurement standards, that would allow a more rapid and effective comparison of data.

Permafrost and active layer research on James Ross Island: An overview

2019 ◽  
Vol 9 (1) ◽  
pp. 20-36 ◽  
Author(s):  
Filip Hrbáček ◽  
Daniel Nývlt ◽  
Kamil Láska ◽  
Michaela Kňažková ◽  
Barbora Kampová ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Thermal Regime ◽  
Ground Temperature ◽  
Active Layer Thickness ◽  
Near Surface ◽  
James Ross Island ◽  
The Mean

This study summarizes the current state of the active layer and permafrost research on James Ross Island. The analysis of climate parameters covers the reference period 2011–2017. The mean annual air temperature at the AWS-JGM site was -6.9°C (ranged from -3.9°C to -8.2°C). The mean annual ground temperature at the depth of 5 cm was -5.5°C (ranged from -3.3°C to -6.7°C) and it also reached -5.6°C (ranged from -4.0 to -6.8°C) at the depth of 50 cm. The mean daily ground temperature at the depth of 5 cm correlated moderately up to strongly with the air temperature depending on the season of the year. Analysis of the snow effect on the ground thermal regime confirmed a low insulating effect of snow cover when snow thickness reached up to 50 cm. A thicker snow accumulation, reaching at least 70 cm, can develop around the hyaloclastite breccia boulders where a well pronounced insulation effect on the near-surface ground thermal regime was observed. The effect of lithology on the ground physical properties and the active layer thickness was also investigated. Laboratory analysis of ground thermal properties showed variation in thermal conductivity (0.3 to 0.9 W m-1 K-1). The thickest active layer (89 cm) was observed on the Berry Hill slopes site, where the lowest thawing degree days index (321 to 382°C·day) and the highest value of thermal conductivity (0.9 W m-1 K-1) was observed. The clearest influence of lithological conditions on active layer thickness was observed on the CALM-S grid. The site comprises a sandy Holocene marine terrace and muddy sand of the Whisky Bay Formation. Surveying using a manual probe, ground penetrating radar, and an electromagnetic conductivity meter clearly showed the effect of the lithological boundary on local variability of the active layer thickness.

The use of Frequency Domain Electro-magnetometry for the characterization of permafrost active layers: case studies in the Swiss Alps

2020 ◽  
Author(s):  
Jacopo Boaga ◽  
Marcia Phillips ◽  
Jeannette Noetzli ◽  
Anna haberkorn ◽  
Robert Kenner ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Active Layer ◽  
Electrical Contact ◽  
Slope Instability ◽  
Swiss Alps ◽  
Active Layer Thickness ◽  
High Mountain ◽  
Contactless Method ◽  
Geophysical Surveys

<p>The characterization of the active layer (AL) in mountain permafrost is an important part of monitoring climate change effects in periglagical environments and may help to determine potential slope instability. Permafrost affects 25% of the Northern Hemisphere and 17% of the entire Earth. It has been studied for decades both in the polar regions and – starting a few decades later – in high mountain environments. Typical point information from permafrost boreholes can be extended to wider areas by geophysical prospecting and provide information that cannot be detected by thermal observations alone.</p><p>During Summer 2019 we performed several geophysical surveys at permafrost borehole sites in the Swiss Alps. We focused on electrical resistivity tomography (ERT) and Frequency Domain Electro-magnetic techniques (FDEM) to compare the methods and test the applicability of FDEM for active layer characterization, i.e., its thickness and lateral continuity. ERT provides an electrical image of the subsoil and can discern active layer thickness, changes in ground ice and geological features of the subsoil. From a logistic point of view a contactless method such as FDEM would be preferable : i) it can provide electrical properties of the subsoil with no need of physical electrical contact with the soil; ii) it can cover a wider area of exploration compared to ERT, iii) it is faster and data collection is simpler than with ERT due to lighter instruments and less preparation time needed.</p><p>Based on the FDEM surveys at the Swiss permafrost sites we were able to detect the frozen/unfrozen boundary and to achieve results that were in agreement with those obtained from classical ERT and borehole temperature data. The results were promising for future active layer monitoring with the contactless FDEM method.</p>

Microscale Mechanical Behavior of the Subsurface by Finishing Processes

2005 ◽  
Vol 127 (2) ◽  
pp. 333-338 ◽  
Author(s):  
Y. B. Guo ◽  
A. W. Warren
Keyword(s):  
Mechanical Behavior ◽  
Hard Turning ◽  
White Layer ◽  
Subsurface Layer ◽  
Ground Surface ◽  
Small Scale ◽  
Near Surface ◽  
Microstructure Changes ◽  
Shallow Layer ◽  
Finishing Processes

Hard turning, grinding, and honing are common finishing processes in today’s production. The machined subsurface undergoes severe deformation and possible microstructure changes in a small scale subsurface layer <20μm. Mechanical behavior of this shallow layer is critical for component performance such as fatigue and wear. Due to the small size of this region, mechanical behavior of this shallow layer is hard to measure using traditional material testing. With the nanoindentation method, mechanical behavior (nanohardness and modulus) at the microscale in subsurface was measured for AISI 52100 and AISI 1070 steel components machined by hard turning, grinding, and honing. The test results show that white layer increases nanohardness but decreases modulus of a turned surface. Nanohardness and modulus of the ground surface are slightly smaller than the honed one in the subsurface. However, grinding produces higher nanohardness and modulus in near-surface <10μm than honing, while honing produces more uniform hardness and modulus in the near-surface and subsurface, and would improve component performance. Nanohardness and modulus of the machined near-surface are strongly influenced by strain hardening, residual stress, size-effect, and microstructure changes.

scholarly journals An improved representation of physical permafrost dynamics in the JULES land surface model

2015 ◽  
Vol 8 (1) ◽  
pp. 715-759 ◽  
Author(s):  
S. Chadburn ◽  
E. Burke ◽  
R. Essery ◽  
J. Boike ◽  
M. Langer ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Moisture ◽  
Active Layer ◽  
Land Surface ◽  
Climate Models ◽  
Surface Soil ◽  
Active Layer Thickness ◽  
Mean Square ◽  
Near Surface ◽  
Soil Temperatures

Abstract. It is important to correctly simulate permafrost in global climate models, since the stored carbon represents the source of a potentially important climate feedback. This carbon feedback depends on the physical state of the permafrost. We have therefore included improved physical permafrost processes in JULES, which is the land-surface scheme used in the Hadley Centre climate models. The thermal and hydraulic properties of the soil were modified to account for the presence of organic matter, and the insulating effects of a surface layer of moss were added, allowing for fractional moss cover. We also simulate a higher-resolution soil column and deeper soil, and include an additional thermal column at the base of the soil to represent bedrock. In addition, the snow scheme was improved to allow it to run with arbitrarily thin layers. Point-site simulations at Samoylov Island, Siberia, show that the model is now able to simulate soil temperatures and thaw depth much closer to the observations. The root mean square error for the near-surface soil temperatures reduces by approximately 30%, and the active layer thickness is reduced from being over 1 m too deep to within 0.1 m of the observed active layer thickness. All of the model improvements contribute to improving the simulations, with organic matter having the single greatest impact. A new method is used to estimate active layer depth more accurately using the fraction of unfrozen water. Soil hydrology and snow are investigated further by holding the soil moisture fixed and adjusting the parameters to make the soil moisture and snow density match better with observations. The root mean square error in near-surface soil temperatures is reduced by a further 20% as a result.

Sign in / Sign up

Export Citation Format

Share Document