scholarly journals Melting temperature changes during slip across subglacial cavities drive basal mass exchange

2021 ◽  
pp. 1-7
Author(s):  
Alan W. Rempel ◽  
Colin R. Meyer ◽  
Kiya L. Riverman
Keyword(s):  
Normal Stress ◽  
Melting Temperature ◽  
Formation Mechanism ◽  
Mass Exchange ◽  
Liquid Water ◽  
Early Recognition ◽  
Temperature Changes ◽  
Basal Ice ◽  
Bed Materials ◽  
Subglacial Drainage

Abstract The importance of glacier sliding has motivated a rich literature describing the thermomechanical interactions between ice, liquid water and bed materials. Early recognition of the gradient in melting temperature across small bed obstacles led to focused studies of regelation. An appreciation for the limits on ice deformation rates downstream of larger obstacles highlighted a role for cavitation, which has subsequently gained prominence in descriptions of subglacial drainage. Here, we show that the changes in melting temperature that accompany changes in normal stress along a sliding ice interface near cavities and other macroscopic drainage elements cause appreciable supercooling and basal mass exchange. This provides the basis of a novel formation mechanism for widely observed laminated debris-rich basal ice layers.

scholarly journals Melting temperature changes during slip across subglacial cavities drive basal mass exchange

2021 ◽  
Author(s):  
Alan Rempel ◽  
Colin Meyer ◽  
Kiya Riverman
Keyword(s):  
Normal Stress ◽  
Melting Temperature ◽  
Formation Mechanism ◽  
Mass Exchange ◽  
Liquid Water ◽  
Early Recognition ◽  
Temperature Changes ◽  
Basal Ice ◽  
Bed Materials ◽  
Subglacial Drainage

The importance of glacier sliding has motivated a rich literature describing the thermomechanical interactions between ice, liquid water, and bed materials. Early recognition of the gradient in melting temperature across small bed obstacles led to focussed studies of regelation. An appreciation for the limits on ice deformation rates downstream of larger obstacles highlighted a role for cavitation, which has subsequently gained prominence in descriptions of subglacial drainage. Here, we show that the changes in melting temperature that accompany changes in normal stress along a sliding ice interface near cavities and other macroscopic drainage elements cause appreciable supercooling and basal mass exchange. This provides the basis of a novel formation mechanism for widely observed laminated debris-rich basal ice layers.

scholarly journals Temporal isotope changes in wet snow layers in association with mass exchange between snow particles and liquid water in between the particles

2005 ◽  
Vol 40 ◽  
pp. 128-132 ◽  
Author(s):  
S. Hashimoto ◽  
S. Zhou ◽  
M. Nakawo ◽  
M. Shimizu ◽  
N. Ishikawa
Keyword(s):  
Melting Point ◽  
Water Content ◽  
Pore Water ◽  
Mass Exchange ◽  
Liquid Water ◽  
Closed System ◽  
Temporal Change ◽  
Field Observations ◽  
Isotope Concentration ◽  
Wet Snow

AbstractWe carried out snow-pit observations at Nagaoka, Niigata prefecture, Japan, where the snow layers were at the melting point. It was observed that the water content in the snowpack was nearly constant at approximately 10%, and the coarsening rate of snow particles was about 0.4×10–3mm3 h–1, which was in the range between the rate for dry snow and that for snow soaked in water. The isotope change of snow particles by melting and freezing in a closed system under isothermal conditions at 0˚C was modeled. The temporal change in isotope concentration was calculated for wet snow layers, based on the fractionation between snow particles and liquid water in between the particles, in association with the coarsening of snow particles. The results compared well with field observations. These results suggest that the isotope concentration of the pore water that flows downward from the surface contributed significantly to the isotope change of snow particles.

The Melting Temperature of Liquid Water with the Effective Fragment Potential

2015 ◽  
Vol 6 (18) ◽  
pp. 3555-3559 ◽  
Author(s):  
Kurt R. Brorsen ◽  
Soohaeng Yoo Willow ◽  
Sotiris S. Xantheas ◽  
Mark S. Gordon
Keyword(s):  
Melting Temperature ◽  
Liquid Water ◽  
Effective Fragment Potential

scholarly journals Channelized subglacial drainage over a deformable bed

1994 ◽  
Vol 40 (134) ◽  
pp. 3-15 ◽  
Author(s):  
Joseph S. Walder ◽  
Andrew Fowler
Keyword(s):  
Water Pressure ◽  
Ice Sheets ◽  
Drainage System ◽  
West Antarctica ◽  
Plausible Assumption ◽  
Basal Ice ◽  
Ice Stream B ◽  
Steep Slopes ◽  
Subglacial Drainage

AbstractWe develop theoretically a description of a possible subglacial drainage mechanism for glaciers and ice sheets moving over saturated, deformable till. The model is based on the plausible assumption that flow of water in a thin film at the ice-till interface is unstable to the formation of a channelized drainage system, and is restricted to the case in which meltwater cannot escape through the till to an underlying aquifer. In describing the physics of such channelized drainage, we have generalized and extended Röthlisberger’s model of channels cut into basal ice to include “canals” cut into the till, paying particular attention to the role of sediment properties and the mechanics of sediment transport. We show that sediment-floored Röthlisberger (R) channels can exist for high effective pressures, and wide, shallow, ice-roofed canals cut into the till for low effective pressures. Canals should form a distributed, non-arborescent system, unlike R channels. For steep slopes typical of alpine glaciers, both drainage systems can exist, but with the water pressure lower in the R channels than in the canals; the canal drainage should therefore be unstable in the presence of channels. For small slopes typical of ice sheets, only canals can exist and we therefore predict that, if channelized meltwater flow occurs under ice sheets moving over deformable till, it takes the form of shallow, distributed canals at low effective pressure, similar to that measured at Ice Stream B in West Antarctica. Geologic evidence derived from land forms and deposits left by the Pleistocene ice sheets in North America and Europe is also consistent with predictions of the model.

Variations of the Specimen Temperature Depending on the Pattern of the Multiaxial Load – Preliminary Research

2012 ◽  
Vol 726 ◽  
pp. 162-168 ◽  
Author(s):  
Adam Lipski ◽  
Dariusz Skibicki
Keyword(s):  
Plastic Strain ◽  
Normal Stress ◽  
Temperature Change ◽  
Infrared Thermography ◽  
Strain Energy ◽  
Temperature Changes ◽  
Average Temperature ◽  
Specimen Temperature ◽  
Preliminary Research ◽  
Plastic Strain Energy

This paper provides the results of research on temperature changes of cylindrical specimens depending on the pattern of the multiaxial load. The research were made by using passive infrared thermography. It was found out that the average temperature value is significantly dependent on the plastic strain energy and that the temperature change amplitude depends on the nominal normal stress (except for torsion).

Effect of Melting Temperature on Microstructure of In Situ TiC/Al Composite and Formation Mechanism of TiC

2014 ◽  
Vol 989-994 ◽  
pp. 320-324
Author(s):  
Huan Long Yuan ◽  
Ze Hua Zhou ◽  
Ze Hua Wang ◽  
Zhao Jun Zhong ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Melting Temperature ◽  
Formation Mechanism ◽  
Al Composite ◽  
The Matrix ◽  
In Situ Tic ◽  
Reaction Speed ◽  
Al Matrix

Formation mechanism of TiC in Al matrix at a rather low melting temperature using in situ technology was studied. And effect of the melting temperature on the microstructure of in-situ TiC/Al composite was investigated. The results indicate that, the resultants of TiC and Al3Ti were found out in the matrix; however, no evidence showed that Al4C3, a resultant phase existed probably in TiC/Al composite in accordance with the relative reference, was found out. Compared to the sample of T750, more TiC and less Al3Ti existed in the sample of T850, and morphography of Al3Ti changed from block to bar with the increasing melting temperature. The melting temperature affected extremely the reaction speed and the resultants.

scholarly journals Channelized subglacial drainage over a deformable bed

1994 ◽  
Vol 40 (134) ◽  
pp. 3-15 ◽  
Author(s):  
Joseph S. Walder ◽  
Andrew Fowler
Keyword(s):  
Water Pressure ◽  
Ice Sheets ◽  
Drainage System ◽  
West Antarctica ◽  
Plausible Assumption ◽  
Basal Ice ◽  
Ice Stream B ◽  
Steep Slopes ◽  
Subglacial Drainage

AbstractWe develop theoretically a description of a possible subglacial drainage mechanism for glaciers and ice sheets moving over saturated, deformable till. The model is based on the plausible assumption that flow of water in a thin film at the ice-till interface is unstable to the formation of a channelized drainage system, and is restricted to the case in which meltwater cannot escape through the till to an underlying aquifer. In describing the physics of such channelized drainage, we have generalized and extended Röthlisberger’s model of channels cut into basal ice to include “canals” cut into the till, paying particular attention to the role of sediment properties and the mechanics of sediment transport. We show that sediment-floored Röthlisberger (R) channels can exist for high effective pressures, and wide, shallow, ice-roofed canals cut into the till for low effective pressures. Canals should form a distributed, non-arborescent system, unlike R channels. For steep slopes typical of alpine glaciers, both drainage systems can exist, but with the water pressure lower in the R channels than in the canals; the canal drainage should therefore be unstable in the presence of channels. For small slopes typical of ice sheets, only canals can exist and we therefore predict that, if channelized meltwater flow occurs under ice sheets moving over deformable till, it takes the form of shallow, distributed canals at low effective pressure, similar to that measured at Ice Stream B in West Antarctica. Geologic evidence derived from land forms and deposits left by the Pleistocene ice sheets in North America and Europe is also consistent with predictions of the model.

Classification of Thermography Breast Images for Cancer Detection using Machine Learning

2020 ◽  
pp. 01-06
Author(s):  
Aishwarya Nirkhede ◽  
Ruchika Adkine ◽  
Bhargavi Lohit ◽  
Dipali Lande ◽  
Swita Nitnaware ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Urban Communities ◽  
Cancer Cells ◽  
Cancer Detection ◽  
Rural Areas ◽  
Early Recognition ◽  
Skin Layer ◽  
Temperature Changes ◽  
The Individual

Breast cancer is presently the most well-known cancer in many urban communities in India, and the second generally normal in rural areas. Early recognition of breast cancer by orderly assessment of the individual may improve the endurance rate. Infrared thermography one of the imaging strategies that produce high goals infrared pictures shows the warmth design dependent on the temperature changes in breast regarding the movement of the cancer cells. Expanded metabolic movement and the bloodstream because of the augmentation of cancer cells instigates more warmth on the skin layer which are caught by the warm camera to deliver the thermal images. This paper talks about the picture handling calculation to recognize the nearness of cancer from the procured warm pictures. The approach incorporates the preprocessing the procured picture and fragmenting the area of enthusiasm, extricating the features from the divided picture followed by feature selection and classification.

scholarly journals Ice–shelf Grounding: Ice and Bedrock Temperature Changes

1980 ◽  
Vol 25 (93) ◽  
pp. 397-400 ◽  
Author(s):  
Douglas R. MacAyeal ◽  
Robert H. Thomas
Keyword(s):  
Sea Water ◽  
Thermal Inertia ◽  
Equilibrium Temperature ◽  
Transient Temperature ◽  
Ice Shelf ◽  
Temperature Changes ◽  
Basal Ice ◽  
Equivalent Time ◽  
Sea Bed ◽  
Surface Slopes

AbstractIce rises form where an ice shelf runs aground on the sea bed. After grounding occurs, basal ice temperatures cool from the sea-water temperature towards an equilibrium temperature appropriate to grounded ice. This cooling can take many thousands of years, and much of the delay is due to the thermal inertia of the bedrock. Here, we calculate transient temperature profiles for an ice rise with a final summit thickness of 520 m that formed by grounding of ice shelf 420 m thick. Seventy-five per cent cooling of the basal ice takes between 7 000 and 11 500 years, depending on the “thermal memory” of the bedrock. This compares with an equivalent time of only 1400 years if we neglect the thermal inertia of the bedrock.Because the surface slopes of the ice rise are related to the flow properties of the underlying ice, the summit thickness will tend to thicken as the basal ice cools. In principle, it should be possible to estimate the age of a recently-formed ice rise by examining its temperature/depth profile.

A Study of Mechanisms of Poly (PhenyleneSulfide) Thermal Degradation in Air

2010 ◽  
Vol 112 ◽  
pp. 9-17 ◽  
Author(s):  
Celine Gros ◽  
Julie Tarrieu ◽  
Valérie Nassiet ◽  
Emmanuel Dutarde
Keyword(s):  
Thermal Degradation ◽  
Melting Temperature ◽  
Extensive Study ◽  
Temperature Changes ◽  
Dsc Measurements ◽  
Melting Endotherm ◽  
The Subject ◽  
Industrial Needs ◽  
Intensive Work

Because of its special properties and commercial significance, Poly(phenylene sulfide) (PPS) has been the subject of many research efforts since its commercial introduction in 1967. Intensive work has been done on its crystalline structure and morphology and its thermal behaviour. But fewer investigations have been carried out to understand long term behaviour in high temperature environments. Always anticipating industrial needs linked to power integration, we have launched an extensive study on thermal aging in air of PPS at 250°C. This study has shown that PPS thermal degradation in air happens by intermolecular branching reaction, similar to crosslinking. This phenomenon was already known for temperature above 300°C. This crosslinking is evidenced by rheometry where the relative position of G’ and G’’ above melting temperature changes with aging. IR spectroscopy confirms that para substituted benzene in PPS molecule is transformed in 1,2,4 trisubstituted benzene. DSC measurements evidence both an elevation of melting temperature and a change in melting endotherm showing significant changes in crystalline morphology along aging, which tends to indicate that crosslinking occurs in crystalline phase. Then degradation implies drastic loss of mechanical properties leading to destruction of the sample.

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