scholarly journals Thermal characterization of the active layer at the Limnopolar Lake CALM-S site on Byers Peninsula (Livingston Island), Antarctica

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 721-739 ◽  
Author(s):  
M. A. de Pablo ◽  
M. Ramos ◽  
A. Molina
Keyword(s):  
Thermal Behavior ◽  
Active Layer ◽  
Thermal Characterization ◽  
Active Layer Thickness ◽  
Freezing And Thawing ◽  
Thermal Amplitude ◽  
Permafrost Table ◽  
Different Depths

Abstract. The Limnopolar Lake site (A25), of the Circumpolar Active Layer Monitoring-South network (CALM-S), is located on Byers Peninsula, where the active layer thickness is monitored systematically (by mechanical probing during the thawing season and by temperature devices continuously since 2009). Air, surface, snow and ground temperature devices have been installed to monitor ground thermal behavior, which is presented and characterized here. We use the air and ground mean daily temperature values to define the following parameters: maximum, minimum and mean temperatures, the zero annual thermal amplitude, and the depth and position of the top of the permafrost table. The freezing and thawing seasons (defining their starting dates as well as their length) and the existence of zero curtain periods have also been established. We also derive apparent thermal diffusivity and plot thermograms to study the thermal behavior of the ground at different depths and seasons. After this complete thermal characterization of the active layer, we propose the potential existence of a permafrost table at approximately 130 cm in depth as well as a former transitional layer above it, and discuss the role of water in connection with the thermal behavior of the ground during the study period.

scholarly journals Thermal characterization of the active layer at the Limnopolar Lake CALM-S site on Byers Peninsula (Livingston Island), Antarctica

2014 ◽  
Vol 6 (1) ◽  
pp. 679-729 ◽  
Author(s):  
M. A. de Pablo ◽  
M. Ramos ◽  
A. Molina
Keyword(s):  
Thermal Behavior ◽  
Active Layer ◽  
Thermal Characterization ◽  
Transitional Zone ◽  
Active Layer Thickness ◽  
Freezing And Thawing ◽  
Thermal Amplitude ◽  
Permafrost Table ◽  
Different Depths

Abstract. The Limnopolar Lake CALM-S site (A25) is the unique location on Byers peninsula where the active layer thickness is systematically monitorized (by mechanical probing during the thaw season and by temperature devices continuously since 2009). An air, surface, snow and ground temperature monitoring devices have been installed to monitor ground thermal behavior. We analyzed these data to present there the active layer thermal characterization. We use the air and ground mean daily temperature data to define the following parameters: maximum, minimum and mean temperatures at the air and at different depths, the zero annual thermal amplitude depths and position of the top of the permafrost table. The freezing and thawing seasons (defining their starting dates as well as their length), and the existence of zero curtain periods has been also established. We also derive apparent thermal diffusivity and plot thermograms to study the thermal behavior of the ground at different depths. After this complete thermal characterization of the active layer, we propose the potential existence of a~permafrost table at about 130 cm in depth as well as the transitional zone above it, and discuss the role of water in connection with the thermal behavior of the ground during the study period.

Transient Thermal Characterization of ErAs/In0.53Ga0.47As Thermoelectric Module

2007 ◽  
Author(s):  
Y. Ezzahri ◽  
R. Singh ◽  
K. Fukutani ◽  
Z. Bian ◽  
A. Shakouri ◽  
...  
Keyword(s):  
Metallic Nanoparticles ◽  
Thermoelectric Module ◽  
Thermal Characterization ◽  
Hot Electrons ◽  
Thermoelectric Power Factor ◽  
Scattering Centers ◽  
Network Identification ◽  
Transient Thermal

Embedded metallic nanoparticles in semiconductors have recently been proven to be of great interest for thermoelectric applications. These metallic nanoparticles play the role of scattering centers for phonons and a source of doping for electrons; they reduce simultaneously the thermal conductivity and increase the thermoelectric power factor of the semiconductor. It has also shown that metal/semiconductor heterostructures can be used to break the crystal momentum symmetry for hot electrons in thermionic devices, then increasing the number of electrons participating in transport. A thermoelectric module of 200 N-P pairs of InGaAlAs with embedded ErAs metallic nanoparticles has been fabricated. Network Identification by Deconvolution (NID) technique is then applied for transient thermal characterization of this thermoelectric module. The combination of this new representation of the dynamic behavior of the packaged device with high resolution thin film temperature measurement allows us to obtain information about heat transfer within the thermoelectric module. This is used to extract the thermal resistances and heat capacitances of the module.

Multi-methodological investigation of a retrogressive thaw slump in the Richardson Mountains, Northwest Territories, Canada

2020 ◽  
Author(s):  
Julius Kunz ◽  
Christof Kneisel ◽  
Tobias Ullmann ◽  
Roland Baumhauer
Keyword(s):  
Electrical Resistivity ◽  
Active Layer ◽  
Geophysical Methods ◽  
Three Dimensional ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Low Resistivity ◽  
Permafrost Table ◽  
Retrogressive Thaw Slump ◽  
Richardson Mountains

<p>The Mackenzie-Delta Region is known for strong morphological activity in context of global warming and permafrost degradation, which reveals in a large number of retrogressive thaw slumps. These are frequently found along the shorelines of inland lakes and the coast; however, this geomorphological phenomenon also occurs at inland ​​streams and creeks of the Peel Plateau and the Richardson Mountains, located in the southwest of the delta. Here several active retrogressive thaw slumps are found of which some have reached an extent of several hectares, e.g. the mega slump at the Dempster Creek.</p><p>In this study we investigated a recent retrogressive thaw slump at the edge of the Richardson Mountains close to the Dempster Highway to determine the subsurface properties using non-invasive geophysical methods. We performed three-dimensional Ground Penetrating Radar (GPR) surveys, as well as quasi-three-dimensional Electrical Resistivity Tomography (ERT) surveys in order to investigate the subsurface characteristics adjacent to the retreating headwall of the slump. These measurements provide information on the topography of the permafrost table, ice content and/or water pathways on top, within or under the permafrost layer. Additionally, we performed manual measurements of the active layer thickness for validation of the geophysical models. The approach was complemented by the analysis of high-resolution photogrammetric digital elevation models (DEM) that were generated using in situ drone acquisitions.</p><p>The measured active layer depths show a strong influence of the relief and especially of small creeks on the permafrost table topography. Likely, this influence also is the primary trigger for the initial slump activity. In addition, the ERT measurements show strong variations of the electrical resistivity values in the upper few meters, which are indicative for heterogeneities, also within the ice-rich permafrost body. Especially noticeable is a layer of low resistivity values in an area adjacent to the slump headwall. This layer is found at depths between 4m to 7m, which approximately corresponds to the base of the headwall. Here, the low resistivity values could be indicative for an unfrozen or water-rich layer below the ice-rich permafrost. Consequently, this layer may have contributed to the initial formation of the slump and is important for the spatial extension of the slump.</p><p>These results present new insights into the subsurface of an area adjacent to an active retrogressive thaw slump and may contribute to a better understanding of slump development.</p>

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>

scholarly journals Frozen ground and snow cover monitoring in the South Shetland Islands, Antarctica: Instrumentation, effects on ground thermal behaviour and future research

2016 ◽  
Vol 42 (2) ◽  
pp. 475 ◽  
Author(s):  
M. A. De Pablo ◽  
M. Ramos ◽  
A. Molina ◽  
G. Vieira ◽  
M. A. Hidalgo ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Snow Cover ◽  
Active Layer ◽  
Antarctic Peninsula ◽  
Snow Water Equivalent ◽  
South Shetland Islands ◽  
Active Layer Thickness ◽  
The South ◽  
Shetland Islands ◽  
Snow Cover Duration

The study of the thermal behavior of permafrost and active layer on the South Shetland Islands, in the western side of the Antarctic Peninsula (Antarctica), has been our research topic since 1991, especially after 2006 when we established different active layer thickness and ground thermal monitoring sites of the CALM and GTN-P international networks of the International Permafrost Association. Along this period, the snow cover thickness did not change at those sites, but since 2010, we observed an elongation on the snow cover duration, with similar snow onset, but a delay on the snow offset. Due to the important effects of  snow cover on the ground thermal behavior, we started in late 2015 a new research project (PERMASNOW) focused on the accurate monitoring of the snow cover (duration, density, snow water equivalent and distribution), from very different approaches, including new instrumentation, pictures analysis and remote sensing on optical and radar bands. Also, this interdisciplinary and international research team intends to compare the snow cover and ground thermal behavior with other monitoring sites in the Eastern Antarctic Peninsula where the snow cover is minimum and remains approximately constant.

scholarly journals Optical and Thermal Analysis of Secondary Optics in Light Emitting Diodes’ Packaging: Analysis of MR16 Lamp

2021 ◽  
Vol 2116 (1) ◽  
pp. 012121
Author(s):  
Mohammad Azarifar ◽  
Ceren Cengiz ◽  
Mehmet Arik
Keyword(s):  
Heat Dissipation ◽  
Light Emitting Diodes ◽  
Thermal Characterization ◽  
Thermal Control ◽  
Light Extraction Efficiency ◽  
Thickness Effect ◽  
Package Design ◽  
Light Emitting

Abstract Optical and thermal control are two main factors in package design process of lighting products, specifically light emitting diodes (LEDs). This research is aimed to study the role of secondary optics in opto-thermal characterization of LED packages. Novel thin total internal reflection (TIR) multifaceted reflector (MR) lens is modelled and optimized in Monte-Carlo ray-tracing simulations for MR16 package, regarded as one of the widely used LED lighting products. With criteria of designing an optical lens with 50% reduced thickness in comparison to commercially available lenses utilized in MR16 packages, nearly same light extraction efficiency and more uniform beam angles are achieved. Optical performance of the new lens is compared with the experimental results of the MR16 lamp with conventional lens. Only 2.3% reduction in maximum light intensity is obtained while lens size reduction was more than 25%. Based on the detailed CAD design, heat transfer simulations are performed comparing the lens thickness effect on heat dissipation of MR16 lamp. It was observed that using thinner lenses can reduce the lens and chip temperature, which can result in improved light quality and lifetime of both lens and light source.

Improved thermal characterization of alpine permafrost sites by broadband SIP measurements

2020 ◽  
Author(s):  
Jonas K. Limbrock ◽  
Maximilian Weigand ◽  
Andreas Kemna
Keyword(s):  
Thermal State ◽  
Pore Space ◽  
Field Measurements ◽  
Thermal Characterization ◽  
Active Layer Thickness ◽  
Complex Frequency ◽  
Frequency Range ◽  
Borehole Temperature ◽  
Ice Content

<p>Geoelectrical methods are increasingly used for non-invasive characterization and monitoring of permafrost sites, since the electrical properties of the subsoil are sensitive to the phase change of liquid to frozen water. In this context, electrical subsurface parameters act as proxies for temperature and ice content.  However, it is still challenging to distinguish between air and ice in the pore space of the rock based on the resistivity method alone due to their similarly low electrical conductivity. This ambiguity in the subsurface conduction properties can be reduced by considering the spectral electrical polarization signature of ice using the Spectral Induced Polarization (SIP) method, in which the complex, frequency-dependent impedance is measured. These measurements are hypothesized to allowing for the quantification of ice content (and thus differentiation of ice and air), and for the improved thermal characterization of alpine permafrost sites.</p><p>In the present study, vertical SIP sounding measurements have been made at different alpine permafrost sites in a frequency range from 100 mHz to 45 kHz. From borehole temperature measurements, we know the thermal state of these sites during our SIP soundings, i.e., an active layer thickness of about 4 m at the Schilthorn field site. In order to understand and to calibrate ice and temperature relationships, the electrical impedance was likewise measured on water-saturated soil and rock samples from these field sites in a frequency range from 10 mHz to 45 kHz during controlled freeze-thaw cycles (+20°C to -40°C) in the laboratory.</p><p>For field and laboratory measurements, the resistance (impedance magnitude) shows a similar temperature dependence, with increasing resistance for decreasing temperatures. For each sample, the impedance phase spectra exhibit the well-known temperature-dependent relaxation behavior of ice at higher frequencies (1 kHz - 45 kHz), with an increasing polarization magnitude for lower temperatures or larger depths of investigation, respectively. At lower frequencies (1 Hz - 1 kHz), a polarization with a low frequency dependence is observed in the unfrozen state of the samples. We interpret this response as membrane polarization, considering that it decreases in magnitude with decreasing temperature (i.e., with ongoing freezing).</p><p>Using the independently measured borehole temperature data, a systematic comparison of the SIP laboratory and field measurements indicates the possibility of a thermal characterization of an alpine permafrost site using SIP.</p>

scholarly journals Thermal state of the active layer and permafrost along the Qinghai-Xizang (Tibet) railway from 2006 to 2010

2011 ◽  
Vol 5 (5) ◽  
pp. 2465-2481 ◽  
Author(s):  
Q. Wu ◽  
T. Zhang ◽  
Y. Liu
Keyword(s):  
Linear Regression ◽  
Layer Thickness ◽  
Active Layer ◽  
Thermal State ◽  
Monitoring Network ◽  
The Arctic ◽  
Active Layer Thickness ◽  
Different Depths ◽  
The Mean ◽  
Using Data

Abstract. In this study, we investigated changes in active layer thickness (ALT) and permafrost temperatures at different depths using data from permafrost monitoring network along the Qinghai-Xizang (Tibet) Railway since 2005. Among sites, average ALT is about 3.1 m with a range from about 1.1 m to 4.9 m. From 2006 through 2010, ALT has increased at a rate of about 6.3 cm a−1. The mean rising rate of permafrost temperature at the depth of 6.0 m is about 0.02 °C a−1 estimated by linear regression using five years of data, and the mean rising rate of mean annual ground temperature (MAGT) at depth of zero amplitude is about 0.012 °C a−1. Changes for colder permafrost (MAGT < −1.0 °C) is greater than that for relatively warmer permafrost (MAGT > −1.0 °C). This is consistent with results observed in the Arctic and Subarctic.

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