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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.

The retreat of ice shelves and glaciers over the last century provides unequivocal evidence of recent global warming. Glacierets (miniature glaciers) and ice patches are important components of the cryosphere that highlight the global retreat of glaciers, but knowledge of their behaviour prior to the Little Ice Age is lacking. Here, we report the uranium–thorium age of subglacial carbonate deposits from a recently exposed surface previously occupied by the disappearing Triglav Glacier (southeastern European Alps) that may elucidate the glacier's presence throughout the entire Holocene. The ages suggest the deposits' possible preservation since the Last Glacial Maximum and Younger Dryas. These thin deposits, formed by regelation, are easily eroded if exposed during previous Holocene climatic optima. The age data indicate the glacier's present unprecedented level of retreat since the Last Glacial Maximum and the potential of subglacial carbonates as additional proxies to highlight the extraordinary nature of the current global climatic changes.

We investigate the migration by thermal regelation of single particles and clusters of particles surrounded by ice subjected to a temperature gradient. This phenomenon is relevant to the casting of porous materials, to cryopreservation of biological tissue, and to the degradation of paleoclimatic signals held in ice sheets, for example. Using carefully controlled laboratory experiments, we measure the migration rates of single particles and clusters as they approach the freezing front. We find that clusters migrate at a constant rate, while single particles accelerate towards the freezing front. This fundamental difference is attributed to the fact that, during regelation, melt water passes through the interstices of a cluster, limited by its constant permeability, but for a single particle must flow through a thin layer of pre-melted ice whose thickness diverges as the freezing temperature is approached, reducing the viscous resistance to migration. We extend existing theories of particle and cluster migration to include the influences of different thermal conductivities and of latent heat on the local temperature field in and around the particle or cluster. We find that if the specific latent heat is large or the viscous resistance to flow is sufficiently small then the migration rate is determined solely by heat transport.

Subglacial rock friction is an important control on the sliding dynamics and erosive potential of hard-bedded glaciers, yet it remains largely unconstrained. To explore the relative influence of basal melt rate, effective stress and ice temperature on frictional resistance, we conducted abrasion experiments in which limestone beds were slid beneath a fixed slab of ice laden with granitic rock fragments. Shear stress scales linearly with melt rate and cryostatic stress, confirming that both viscous drag and effective stress are first-order controls on the contact force in drained conditions. Furthermore, temperature gradients in the ice increase the contribution of viscous drag on basal shear stress. In all experiments, the relationship between melt rate and shear stress is best explained by a model that accounts for the effects of regelation and viscous creep on the bed-normal drag force. We interpret this to mean fluid flow around entrained clasts contributed to basal drag even at subfreezing temperatures. Incorporating premelting dynamics into the Watts/Hallet model for subglacial rock friction, we find that the predicted debris-bed drag decreases by approximately an order of magnitude, with a corresponding ~3.5 × increase in the transition radius. This is lower than we observe for ice slightly below the pressure melting point.

Johannes Weertman published his first glaciological paper in 1957 only 5 years after getting his DSc in metallurgy from the Carnegie Institute of Technology. The paper presented the very first sliding law developed quantitatively from first principles, and involved the unconventional idealization of bed roughness using cubic ‘tombstones’ of rock. Since 1957, there has been a great deal of progress in understanding glacier sliding, but few studies, if any, have preserved the original tombstone geometry that was a hallmark of this first theory. The current study presents a partial reanalysis of the sliding process over a bed with tombstone obstacles using modern numerical methods. The result confirms the enduring applicability of Weertman's model as a pedagogical tool and motivates new questions about (1) folding flow near bedrock obstacles that invert normal ice stratigraphy, (2) the presence and role of stress singularities on sharp edges of bedrock, and (3) the validity of a presumption that regelation flow can be plug-like.

Glacier sliding over small obstacles relies on melting on their upstream sides and refreezing downstream. Previous treatments have appealed to ‘pressure melting’ as the cause of the spatial variations in melting temperature that drive thisregelationprocess. However, we show that typical liquid pressure variations across small obstacles are negligible and therefore variations in ice pressure closely approximate variations in effective stress. For a given change in effective stress, the equilibrium melting temperature changes by an order of magnitude more than when the pressure of ice and liquid both change by an equal amount. In consequence, the temperature gradients that drive heat flow across small obstacles are larger than previously recognized and the rate of regelation is faster. Under typical conditions, the transition wavelength at which ice deformation and regelation contribute equally is of m-scale, several times longer than previous predictions, which have been reported to underestimate field inferences.

The retreat of ice shelves and glaciers over the last century provides unequivocal evidence of recent global warming. Glacierets (miniature glaciers) are an important component that highlights the global retreat of glaciers, but knowledge of their behaviour prior to the Little Ice Age is lacking. Here, we present subglacial carbonate deposits from a recently exposed surface previously occupied by the disappearing Triglav Glacier (southeastern European Alps) that may elucidate the glacier’s existence throughout the entire Holocene since their maximum uranium-thorium (U-Th) ages suggest their possible preservation since the Last Glacial Maximum and Younger Dryas. These thin deposits, formed by regelation, are easily eroded if exposed during previous Holocene climatic optima. The age data indicate the glacier’s present unprecedented level of retreat since the Last Glacial Maximum, and the potential of subglacial carbonates as additional proxies to highlight the extraordinary nature of the current global climatic changes.

In this article we review some of the most important and relevant literature on the properties of ice. We focus on three of its surface properties, namely, the slipperiness of ice, the phenomena of a string under load passing through a block of ice without cutting the block in half, and pressure melting and adhesion of blocks of ice. We then provide an argument for the most plausible factor responsible for each of these effects.

The classic regelation experiment of Thomson in the 1850s deals with cutting an ice cube, followed by refreezing. The cutting was attributed to pressure-induced melting but has been challenged continuously, and only lately consensus emerged by understanding that compression shortens the O:H nonbond and lengthens the H–O bond simultaneously. This H–O elongation leads to energy loss and lowers the melting point. The hot debate survived well over 150 years, mainly due to a poorly defined heat exchange with the environment in the experiment. In our current experiment, we achieved thermal isolation from the environment and studied the fully reversible ice–liquid water transition for water confined between graphene and muscovite mica. We observe a transition from two-dimensional (2D) ice into a quasi-liquid phase by applying a pressure exerted by an atomic force microscopy tip. At room temperature, the critical pressure amounts to about 6 GPa. The transition is completely reversible: refreezing occurs when the applied pressure is lifted. The critical pressure to melt the 2D ice decreases with temperature, and we measured the phase coexistence line between 293 and 333 K. From a Clausius–Clapeyron analysis, we determine the latent heat of fusion of two-dimensional ice at 0.15 eV/molecule, being twice as large as that of bulk ice.

When a particle is placed in a material with a lower bulk melting temperature, intermolecular forces can lead to the existence of a premelted liquid film of the lower melting temperature material. Despite the system being below the melting temperatures of both solids, the liquid film is a consequence of thermodynamic equilibrium, controlled by intermolecular, ionic and other interactions. An imposed temperature gradient drives the translation of the particle by a process of melting and refreezing known as thermal regelation. We calculate the rate of regelation of spherical particles surrounded by premelted films that contain ionic impurities. The impurities enhance the rate of motion thereby influencing the dynamics of single particles and distributions of particles, which we describe in addition to the consequences in natural and technological settings., Comment: 6 pages, 6 figures, Soft Matter, 2020

Phonon spectrometrics examination of the effect of pressure, temperature, molecular undercoordination, and charge injection by acid, base, and salt solvation establishes the regulations for the hydrogen bonding and electronic dynamics and the properties of the deionized water and aqueous solutions. Consistency between theory and measurements confirms the essentiality of the quasisolid phase of negative thermal expansion due to O:H–O segmental specific heat disparity, and the supersolid phase due to electrostatic polarization by ions injection or molecular undercoordination. Lewis acid and base solvation creates the H↔H anti–HB due to the excessive protons and the O:⇔:O super–HB because of the excessive lone pairs, respectively. The multifield mediation of the HB network results in anomalies of water ice and aqueous solutions such as ice friction, ice floating, regelation, superheating and supercooling, warm water speedy cooling, and critical conditions for phase transition. Extending the knowledge towards the deep engineering of liquid water would be promising.

The inter oxygen repulsion opposes compression minimizing the compressibility. Polarization enlarges the bandgap and the dielectric permittivity of water ice by raising the nonbonding states above the Fermi energy. Progress evidences the efficiency and essentiality of the coupled hydrogen bonding and electronic dynamics in revealing the core physics and chemistry of water ice, which could extend to other molecular crystals such as energetic materials., Comment: 15 k words, 118 refs, 17 figures

Micromorphology of quartz sand grains is used to reconstruct processes occurring in the glacial environment and to distinguish the latter from other environments. Two processes dominate in the glacial environment, i.e., crushing and abrasion, or a combination thereof. Their effect is a wide range of microstructures on the surface of quartz grains, e.g., chattermarks, conchoidal fractures and multiple grooves. However, the periglacial environment also effectively modifies the surface of quartz grains. The active layer of permafrost is considered to have a significantly higher contribution to the formation of crushed grains and the number of microstructures resulting from mechanical destruction (e.g., breakage blocks or conchoidal fractures), as compared to deposits which are not affected by freeze–thaw cycles. However, only a few microstructures are found in both environments. At the same time, there are several processes in subglacial environments related to freeze–thaw cycles, e.g., regelation, congelation, basal adfreezing, and glaciohydraulic supercooling. Most likely, therefore, the role of the glacial environment in the destruction of quartz grains has been misinterpreted, and consequently the conclusions regarding environmental processes drawn on the basis of the number of crushed grains and edge-to-edge contacts are erroneous.

I present a theory for ice friction for ice sliding on a hard randomly rough surface which includes ice melting-freezing (regelation), viscoelastic energy dissipation, and cavitation. The theory is an extension of earlier work by Weertman, Lliboutry, Nye, and Kamb. I present numerical results for surfaces with realistic surface roughness power spectra. I consider both airfilled and (pressurized) waterfilled cavities. The calculated frictional shear stresses are consistent with experimental observations for temperate glaciers.

The growth dynamics of D2O ice in liquid H2O in a microfluidic device were investigated between the melting points of D2O ice (3.8 °C) and H2O ice (0 °C). As the temperature was decreased at rates between 0.002 °C/s and 0.1 °C/s, the ice front advanced but retreated immediately upon cessation of cooling, regardless of the temperature. This is a consequence of the competition between diffusion of H2O into the D2O ice, which favors melting of the interface, and the driving force for growth supplied by cooling. Raman microscopy tracked H/D exchange across the solid H2O–solid D2O interface, with diffusion coefficients consistent with transport of intact H2O molecules at the D2O ice interface. At fixed temperatures below 3 °C, the D2O ice front melted continuously, but at temperatures near 0 °C a scalloped interface morphology appeared with convex and concave sections that cycled between growth and retreat. This behavior, not observed for D2O ice in contact with D2O liquid or H2O ice in contact with H2O liquid, reflects a complex set of cooperative phenomena, including H/D exchange across the solid–liquid interface, latent heat exchange, local thermal gradients, and the Gibbs–Thomson effect on the melting points of the convex and concave features.

The sliding of an ice mass over its bed represents one of the main mechanisms for the forward motion of glaciers and ice sheets, facilitated by the periodic introduction of meltwater along the ice-bed interface or regelation of the overriding ice. In the geological record, however, physical evidence of this process having occurred beneath former ice masses is apparently limited. This paper presents the results of a detailed micromorphological study of thinly stratified subglacial tills exposed at two sites: (i) Galmis in Switzerland and (ii) Plumpe Farm, near Gretna in SW Scotland. The stratification within these tills comprises alternating layers of massive to weakly foliated diamicton and variably deformed (folded, faulted) laminated silt and clay. Microtextural and microstructural evidence is interpreted in terms of repeated phases of basal sliding as the ice overrode a soft-sediment bed. Elevated meltwater contents/pressures encountered immediately prior to, and during basal sliding promoted localised liquefaction within the bed. Decoupling of the ice mass from its bed enabled the injection of the liquefied diamicton along the ice-bed interface and/or into the laminated sediments immediately adjacent to this boundary. The laminated silts and clays record the settling out of fines (clay, silt) from meltwater trapped along the ice-bed interface after an individual phase of basal sliding has ceased. Injection of till into the locally water saturated silts and clays resulted in partial liquefaction and incomplete mixing of these fine-grained sediments with the diamicton. Density contrasts between the two liquefied sediments led to the development of a complex ‘vinaigrette-like’ texture comprising rounded to irregular till pebbles within a matrix of variably homogenised silty clay. Recoupling of the ice with its bed led to localised folding and thrusting within the laminated silts and clays, hydrofracturing and injection of a network of sand-filled veins, and the imposition of a variably developed clast microfabric in the diamicton layers. Analysis of the clast microfabrics indicates that the intensity of these fabrics is highly variable reflecting the variation in the intensity of deformation imposed by the overriding ice.

Fine ice particles that make up an ice slurry have an advantage in heat transfer and melt rapidly because of their large specific surface area. In a dynamic-type ice storage system, an ice particle bed is melted by warm water flowing through it to obtain cooled water. The melting process generates a wide flow channel, causing a temperature rise in the ejected water and residual unmelted ice. The melting shape of an ice particle bed depends on the initial shape and the inhomogeneity of porosity in it. This study examined the effect of the initial shape of the ice particle bed on the melting behavior to thereby control the melting shape. The melting shape was controlled by establishing a gap on the surface of the ice particle bed. The pressure distribution in the ice bed varied with the size of the gap, and it strongly affected the melting shape.

Present-day sediment distribution offers a potentially strong constraint on past ice sheet evolution. Glacial system models (GSMs), however, cannot address this constraint while lacking appropriate representations of subglacial sediment production and transport. Incorporating these elements in GSMs is also required in order to quantify the impact of a changing sediment cover on glacial cycle dynamics. Towards these goals, we present a subglacial process model (hereafter referred to as the sediment model) that incorporates mechanisms for sediment production, entrainment, transport, and deposition. Bedrock erosion is calculated by both Hallet's and Boulton's abrasion laws separately, and by a novel quarrying law parametrized as a function of subglacial cavity extent. These process-oriented erosion laws are compared against a simple empirical relationship between erosion rate and the work done by basal stress. Sediment entrainment is represented by Philip's law for regelation intrusion and soft-bed deformation is included as a subglacial sediment transport mechanism. The model is driven by the data-calibrated MUN (3D) GSM and a newly developed subglacial hydrology module. The sediment model is applied to the last North American glacial cycle and predicts sediment thickness and cumulative erosion patterns. Results are obtained in the context of a sensitivity analysis and are compared against the present-day distribution of glacigenic sediment and geological estimates of Laurentide Ice Sheet erosion. Given plausible ranges for the sensitivity parameters, chosen a priori based on available literature or on heuristic arguments, the calculated erosion depths overlap with the geological estimates of Laurentide erosion. Most of the runs in the sensitivity set produce unrealistically thick and continuous moraines along the eastern, southern and western margins of the North American ice complex, which suggests that the model overestimates sediment entrainment and thus englacial transport. A realistic sediment distribution is only obtained when the entrainment rate is capped at the average basal melting rate, which suggests that modelled entrainment and basal melting rates should be of the same order of magnitude.

In terms of Kangalassky Open Pit Mine, the authors discuss in situ monitoring of temperature on the surface of blasted overburden rock pile in the course of gradual dragline operation. It is shown that dragline capacity can be related with the surface layer temperature and average size of the blasted overburden fragment.

There is abundant evidence for liquid water on early Mars, but the debate remains whether early Mars was warm and wet or cold and icy with punctuated periods of melting. To further investigate the hypothesis of a cold and icy early Mars, we collected rocks and sediments from the Collier and Diller glacial valleys in the Three Sisters volcanic complex in Oregon. We analyzed rocks and sediments with X-ray diffraction (XRD), scanning and transmission electron microscopies with energy dispersive spectroscopy (SEM, TEM, EDS), and visible, short-wave infrared (VSWIR) and thermal-IR (TIR) spectroscopies to characterize chemical weathering and sediment transport through the valleys. Here, we focus on the composition and mineralogy of the weathering products and how they compare to those identified on the martian surface. Phyllosilicates (smectite), zeolites, and poorly crystalline phases were discovered in pro- and supra-glacial sediments, whereas Si-rich regelation films were found on hand samples and boulders in the proglacial valleys. Most phyllosilicates and zeolites are likely detrital, originating from hydrothermally altered units on North Sister. TEM-EDS analyses of the

A laboratory device was built to measure the forces that ice exerts on a 0.05 m diameter rigid plastic sphere in two different configurations: in contact with a flat bed or isolated from the bed. Measurements indicated that bed-normal contact forces were 1.8 times larger than drag forces due to creeping flow past a slippery sphere isolated from the bed. Measurements of forces as a function of the bed-normal ice velocity, estimations of the ice viscosity parameter and observations of markers in the ice indicate ice is Newtonian with a viscosity of ~1.3x 1011 Pas. Newtonian behavior is expected due to small and transient stresses. A model of regelation indicates that it had a negligible (

As an important lifeline, regelation have a lot of serious effects to the transmission towers and transmission lines. China has been serious affected by the macroclimate, microtopography and microclimate condition, many accidents caused by ice cover occured frequently, it seriously impacted on people’s life and the development of social economy. In order to strengthen and improve the anti-icing capability of transmission tower-line system, it is necessary to study the iced transmission tower-line system. In this paper, the wire model, ground wire model and insulator model were established, and made a reasonable layout at the same time, then the coupled model of the transmission tower-line system is set up. It is supposed that the ice and transmission line are combined closely when there is no external loads, the ice is considered as circular cross-section, the composite structure of ice-transmission line is set up, then the coupled model of the composite structure-tower is set up, the dynamic characteristics of model can be obtained by the model analysis used the finite element analysis software SAP2000.

A mixture of tris-urea 1 and acetone formed a gel on ultrasound irradiation. The gel-to-sol phase transition proceeded by adding halide ions as tetrabutylammonium (TBA) salts. The sols (solutions) were able to regel by mixing them with other metal salts followed by ultrasound irradiation. The regelation ability of various metal salts was tested. Anion selective and non-selective regelation was observed depending on the metal salt used. The mechanistic aspects of the sol-to-gel phase transition in the presence of metal salts were investigated using 1H NMR employing a model compound.

We report on the development of depth hoar and its relation to stable oxygen isotopic content in snow–firn stratigraphy in the percolation zone of Ürümqi glacier No. 1, eastern Tien Shan, China, during the period September 2004–August 2006. The essential condition for the development of depth hoar in the snow–firn pack is the temperature gradient. When the temperature gradient of the snow–firn pack reaches a maximum value of 13.0˚Cm–1 in mid-October, depth hoar begins to develop. By the end of March, the depth hoar might account for 25% of the total snow–firn pack depth. From April to June, as the weather becomes warm, the transport of water vapor diminishes and melting– regelation metamorphism replaces metamorphism caused by the temperature gradient. As a result, the depth hoar turns into coarse-grained firn. Fractionation of the oxygen isotopic content also occurs during formation of the depth hoar. The bottom 15 cm of the depth-hoar δ18O values were depleted in the lighter isotopic species as the snow sublimated from the lower to the upper crystals, and the δ values increased from –9.4% to –7.0% from 8 September 2004 to 25 January 2005. The upper 10 cm of the depth-hoar δ18O values were enriched in the lighter isotopic species and the δ values decreased from –6.8% to –9.3% during the same period.

The two main theories for the origin of the thick bodies of massive ground ice known to exist in the Western Canadian Arctic are (1) segregation-injection and (2) buried glacier ice. Because buried glacier ice may contain significant quantities of stratified debris and may have experienced thawing and refreezing (regelation) on several occasions, it may be very difficult to distinguish between massive segregated ice and buried basal glacier ice. By use of cryostratigraphic and cryotextural (petrofabric) observations, massive ground ice bodies observed in the Sandhills Moraine, southern Banks Island, and the southern Eskimo Lakes region, Pleistocene Mackenzie Delta, are both interpreted as basal glacier ice. Other massive ground ice bodies which have been examined in the Western Canadian Arctic are best explained in terms of segregation-injection. Les deux theories principales qui ont ete avancees pour expliquer l'origine des glaces massives qui existent dans le sol de l'Arctique canadien occidental consistent a les considerer soit comme de la glace de segregation-injection, soit comme de la glace de glacier enfouie. Comme la glace de glacier enfouie peut contenir des quantites significatives de debris stratifies et peut avoir subi des phenomenes de fusion et de regel (regelation) en plusieurs occasions, il est souvent tres difficile de distinguer ces deux types de glace. Sur la base d'observations cryostratigraphiques et cryotexturales (petrofabrique), des corps de glace massive observees dans la moraine Sandhills (au sud de l'ǐle de Banks) et dans la region meridionale de la region des lacs Esquimaux (delta pleistocene du Mackenzie) sont toutes deux interpretees comme de la glace du glacier. D'autres corps de glace massive qui ont ete examines dans l'Arctique canadien occidental sont le mieux expliques comme de la glace de segregation-injection.

Flow and fracture of some soft solids may be described by the ‘solid’ mechanical properties of elastic modulus, yield stress and fracture toughness, all being dependent on rate, temperature and environment. Other soft solids behave more like very viscous materials. When cutting soft solids, friction is often high between the blade and the material, and cutting is made easier when performed with a thin wire. The wire may be held taut in a frame like a fretsaw, but cutting is often done using an initially slack wire pulled into the solid by hand or machine. For both types of material behaviours, we investigate the curved shape taken by a loaded wire, elements along which cut into the material both radially and tangentially. For soft materials displaying solid properties, the treatment is based on the analysis of bi-directional cutting by Atkins et al . (Atkins et al . 2004 J. Mater. Sci. 39 , 2761–2766), in which it was shown that the ratio ξ of tangential to radial displacements strongly influences the cutting forces. The shapes of wires of various lengths arranged as bowstrings, and the loads in the wires, are assessed against experiments on cheddar cheese. The resultant force takes a minimum value for a particular length of the wire, owing to the competition between lower cutting forces, but higher friction at large ξ and vice versa. Passage of a wire through very viscous materials is flow at very low Reynolds number. To determine the path swept out, we make use of the property of all slender bodies of revolution in highly viscous flow, namely, that the drag exerted across the body is approximately twice as large as along. Comparison is made with the experiments on weighted threads falling under gravity in glycerine. Regelation is another example of passage of a wire through a solid. The mechanism is completely different but, in the context of the present paper, we provide in appendix A the solution for the typical hours-long school demonstration where, unlike most reported studies, non-uniform temperature fields develop in the block of ice. Comparison is made with experiment.

Basal sliding is one of the most important components in the dynamics of fast–flowing glaciers, but remains poorly understood on a theoretical level. In this paper, the problem of glacier sliding with cavitation over hard beds is addressed in detail. First, a bound on drag generated by the bed is derived for arbitrary bed geometries. This bound shows that the commonly used sliding law, τ b = Cu m b N n , cannot apply to beds with bounded slopes. In order to resolve the issue of a realistic sliding law, we consider the classical Nye–Kamb sliding problem, extended to cover the case of cavitation but neglecting regelation. Based on an analogy with contact problems in elasticity, we develop a method which allows solutions to be constructed for any finite number of cavities per bed period. The method is then used to find sliding laws for irregular hard beds, and to test previously developed theories for calculating the drag generated by beds on which obstacles of many different sizes are present. It is found that the maximum drag attained is controlled by those bed obstacles which have the steepest slopes.

Thrust-block naled in front of Kuannersuit Glacier, West Greenland, appears to have formed during the termination of a terrestrial surge event by a combination of enhanced winter runoff, rapid advance of the glacier terminus, and proglacial stress release by thrusting and stacking of naled blocks. This process is equivalent to the formation of thrust-block moraines. The thrust-block naled consists of at least seven thrust sheets, which are characterized by stratified ice with beds composed of a lower debris-rich lamina, an intermediate dispersed lamina and a top clean-ice lamina, and underlain by frozen outwash deposits. The thrust-block naled differs from basal stratified ice in the absence of internal deformation structures, a relatively low debris concentration, a clay-rich particle-size distribution and a preferential sorting of lighter minerals. The oxygen isotope composition of the thrust-block naled is indistinguishable from δ18O values from meteoric glacier ice and bulk meltwater, but different from basal stratified ice facies. The d–δD relationship indicates that thrust-block naled has been formed by freezing of successive thin layers of bulk waters with variable isotopic composition, whereas basal stratified ice has developed in a subglacial environment with regelation. This work shows that the association between proglacial naled and rapidly advancing glaciers may have significant consequences for the proglacial geomorphology and the interpretation of basal ice layers.

Basal ice samples were collected from ice exposures in a natural subglacial cavity beneath an outlet glacier of Oksfjordjokelen, North Norway. Sediment and cation (Ca 2+ , Mg 2+ , Na + , K + ) concentrations were then determined, and indicate stacking of basal ice units producing a repeat pattern of 'clean firnification ice' overlying sediment-rich ice. All measured cations show correlation with sediment concentration indicating weathering reactions to be the dominant contributor of cations. Regressions of specific sediment surface area per unit volume with cation concentration are performed and used to predict cation concentrations. These predicted values provide an indication of cation relocation within the basal ice sequence. The results suggest limited melting and refreezing resulting in the relocation of predominantly monovalent cations downward through the profile. Exchange of cations into solution during the melting of sediment-rich ice samples has previously been suggested as a source of error in such investigations. Analyses of sediment-free regelation ice spicules formed at the bed show cation concentrations above firnification ice levels and comparable, in many instances, to the basal ice samples.

Regelation, i.e., ice melts under compression and freezes again when the pressure is relieved, remains puzzling since its discovery in 1850’s by Faraday. Here we show that hydrogen bond (O:H-O) cooperativity and its extraordinary recoverability resolve this anomaly. The H-O bond and the O:H nonbond possesses each a specific heat ηx(T/ΘDx) whose Debye temperature ΘDx is proportional to its characteristic phonon frequency ωx according to Einstein’s relationship. A superposition of the ηx(T/ΘDx) curves for the H-O bond (x = H, ωH ~ 3200 cm−1) and the O:H nonbond (x = L, ωL ~ 200 cm−1, ΘDL = 198 K) yields two intersecting temperatures that define the liquid/quasisolid/solid phase boundaries. Compression shortens the O:H nonbond and stiffens its phonon but does the opposite to the H-O bond through O-O Coulomb repulsion, which closes up the intersection temperatures and hence depress the melting temperature of quasisolid ice. Reproduction of the Tm(P) profile clarifies that the H-O bond energy EH determines the Tm with derivative of EH = 3.97 eV for bulk water and ice. Oxygen atom always finds bonding partners to retain its sp3-orbital hybridization once the O:H breaks, which ensures O:H-O bond recoverability to its original state once the pressure is relieved.

Deglaciated bedrock surfaces in limestone areas often exhibit extensive patterning by solutional furrows and carbonate deposits that occur in close association with undulations in the bed topography. These features clearly result from subglacial dissolution and precipitation of calcite on the bed — induced, for instance, by melting and freezing in a regelation water film — but little is known about the observed morphology. In particular, it is intriguing that (i) the solutional furrows, whose formation requires explanation, are collectively organized into arcuate patterns, with characteristic spacing, and (ii) a fluted or “spiculed” surface texture is ubiquitous on the calcite deposits. Herein, we propose specific mechanisms for such patterning based on a theory where chemical processes in the water film are coupled to regelation physics. Solutional furrows reflect locally enhanced dissolution along stoss surfaces, where CO2-rich bubbles advected in the ice from up-glacier come into contact with the bed. The bubbles form as CO2 is exsolved from freezing film water at the lee of bed bumps. The flutings on the deposit are inherently the manifestation of a spatial instability at the interface where calcite precipitation occurs. Complex interactions underlie some of the striking glacier-bed features shaped by subglacial chemical processes.

An extension of the theory of Ornstein (1906) and Nye (1967) for the drag force on circular wires and other solid bodies creeping through ice by means of pressure-melting and regelation is provided. Nye's theory leads to a form of Stokes law, with rates controlled by heat conduction and lubrication flow in a thin water layer between ice and solid body. New analytical solutions are given for the corresponding drag force and torque on elliptical cylinders and spheroids for the special case of thermally thin water layers and for certain special forms of uncoupled translation and rotation that allow for single-harmonic temperature fields. The present results differ from those proposed by Nye for general body shapes in the limit of negligible thermal resistance of the water layer. Also, the present results for the drag force on elliptic cylinders do not agree with the formulae derived by Tyvand and Bejan (1992) for small ellipticity. A brief review is given for various effects that might account for certain departures of the Nye theory from experiment on circular wires, in the hope that the present results may suggest simpler experiments aimed at systematic modification of the theory to account for such anomalies. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1488–1498, 2014

The melting process of packed beds of ice slurry consisting of aqueous solution and ice particles with a mean diameter of 0.2 mm, so-called liquid ice, was studied. The packed ice layer was melted with aqueous solution sprayed on top of it directly and indirectly. Experiments of the melting process were done by changing the mass of ice, the inlet temperature and the flow rate. The time history of the outlet temperature of the bed was measured and the melting phenomenon was observed. During the melting, it was found that passages through the ice layer were formed and the aqueous solution sprayed on the top of the ice layer hardly permeated the ice layer, but flowed through the passages. Assuming that the flow rate of the solution through the passages was known, the melting process was analyzed. In the case of direct spraying, the effects on the outlet temperature and the formation of passage were clarified by changing the initial mass of ice, the flow rate and the inlet temperature. When the solution was sprayed on top of the ice layer directly (direct spraying), the outlet temperature was kept constant because the heat exchange was enhanced by the mixing effects of spraying. On the contrary, when an obstacle was placed on top of the ice layer (indirect spraying), the outlet temperature was higher than that in the case of direct spraying and was not kept constant.

The melting of a horizontal ice plate from above into a calcium chloride aqueous solution in a rectangular cavity is considered numerically and experimentally. The ice plate melts spontaneously with decreasing temperature at the melting front, even when there exists no initial temperature difference between ice and liquid. Visual observations in the liquid reveal a complicated and random natural convection mainly dominated by the concentration gradient which appears near the melting front. A very coarse and curious surface of the melting front is seen after the melting experiment, that is considered to promote the ice melting. The two-dimensional numerical model proposed in the present study predicts approximately the melting rate.

At Engabreen, Norway, an instrumented panel containing a decimetric obstacle was mounted flush with the bed surface beneath 210 m of ice. Simultaneous measurements of normal and shear stresses, ice velocity and temperature were obtained as dirty basal ice flowed past the obstacle. Our measurements were broadly consistent with ice thickness, flow conditions and bedrock topography near the site of the experiment. Ice speed 0.45 m above the bed was about 130 mm d−1, much less than the surface velocity of 800 mm d−1. Average normal stress on the panel was 1.0–1.6 MPa, smaller than the expected ice overburden pressure. Normal stress was larger and temperature was lower on the stoss side than on the lee side, in accord with flow dynamics and equilibrium thermodynamics. Annual differences in normal stresses were correlated with changes in sliding speed and ice-flow direction. These temporal variations may have been caused by changes in ice rheology associated with changes in sediment concentration, water content or both. Temperature and normal stress were generally correlated, except when clasts presumably collided with the panel. Temperature gradients in the obstacle indicated that regelation was negligible, consistent with the obstacle size. Melt rate was about 10% of the sliding speed. Despite high sliding speed, no significant ice/bed separation was observed in the lee of the obstacle. Frictional forces between sediment particles in the ice and the panel, estimated from Hallet’s (1981) model, indicated that friction accounted for about 5% of the measured bed-parallel force. This value is uncertain, as friction theories are largely untested. Some of these findings agree with sliding theories, others do not.

Experimental results indicate that wet-based, soft-bedded glaciers may penetrate their substrates by regelation (melting and refreezing) and thereby entrain sediment. In principle, there should be a steady depth of penetration at which the downward regelation speed, driven by the interfacial effective pressure, equals the basal melt rate. Herein, the magnitude and distribution of penetration are estimated for the case of a glacier resting on a deformable bed with channelized basal drainage. The distance between channels and the distribution of effective pressure across the bed are calculated, and special attention is paid to the interdependence of the basal melt rate and effective pressure. A major uncertainty is whether fine-grained tills may impede or prevent regelation as a result of high surface tension at the ice/water interface. Predicted penetration depths range from millimetres to a few decimetres, and thus, dirty basal ice layers of such thicknesses might be expected. Predicted distances between channels agree well with those indicated by borehole measurements at Ice Stream B, West Antarctica. Effective pressures, and hence penetration depths, increase toward channels. Therefore, the edges of interfluves, bounded by anastomosing subglacial channels, should be eroded preferentially. This motivates the testable hypothesis that such erosion contributes to the formation of streamlined landforms, such as drumlins. Copyright © 2000 John Wiley & Sons, Ltd.

Melting phenomena are related to a wide variety of engineering fields: purification of metals, welding, electroslag melting, thawing of moist soil, and latent heat-of-fusion thermal-energy storage are a few of important applications which have motivated research in this area. Melting is a phase transformation process that is accompanied by absorption of thermal energy. The essential feature of the systems that exhibit melting phenomena is the existence of a liquid–solid interface that separates the two phases containing different thermophysical properties and the absorption of thermal energy at the interface. The major problem in melting is thus to determine transport phenomena of the latent and sensible heat of the system. There is quite a large body of literature concerning a variety of such problems in engineering as well as in the applied sciences. Recent reviews summarize prior work in this area 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . In previous studies pertaining to melting of a solid contained in a confined vessel, consideration has been given to either to a melting solid which is constrained to prevent its possible movement owing to gravity or to a solid which is free to fall under gravity [8] . In the first case, the melting solid is maintained at a fixed position inside the vessel throughout the melting process, then is completely surrounded by the liquid melt, and the energy needed for the melting is transported from the heating wall to the solid–liquid interface by free convection within the liquid melt. In the second case, the solid is free to respond to the net force acting on it. If the solid phase has higher density than the liquid phase the solid sinks to the bottom of the vessel. On the contrary, if the solid phase is lighter than the liquid phase the unmelted solid is drawn by buoyancy to the top of the vessel. In either case, a region of close-contact melting arises between the solid and the heating wall. Utilization of thermal-energy storage system for air conditioning has recently evoked energy saving and normalizing the requirement level of the electric power supply 9 , 10 . For conventional ice-storage systems using a pure ice system as a phase change material (PCM) it has been pointed out 11 , 12 , 13 , 14 that the melting heat transfer performance may be reduced with time because the melting ice surface is separated more far from the heat transfer wall. Marked attention has recently been given to a slush ice 15 , 16 , which is essentially a mixture of fine ice particles and aqueous binary solution, as a new PCM in place of common ice owing to demand of both high efficient ice producing and regulate handling of melting heat transfer performance as well as transportability. With respect to the melting heat transfer performance in releasing the cold thermal energy from the slush ice, the melting characteristics of a quiescent slush ice around a horizontal heated tube [17] and in a rectangular capsule with a vertical heated wall [18] as well as with a top heated wall [18] were determined experimentally. In addition, a solid–gas–liquid three-phase fluidized bed heat exchange system [19] and a direct contact heat-exchange system, in which the slush ice is operated as the fluidized bed, was proposed for releasing the cold thermal energy. Detailed basic data on the melting characteristics of the slush ice are highly required for developing high efficient heat exchanger using the slush ice. However, there seems to be a variety of unknown characteristics on the melting mechanism as well as the melting behavior for releasing both efficiently and regulatively the cold thermal energy from the slush ice. This paper reports a study on the melting characteristics of slush ice in a horizontal cylindrical capsule. In order to inspect the local heat transfer coefficient distribution in circumference direction in detail, the capsule wall was electrically heated to be a constant heat flux condition. Experimental runs were carried out to investigate the effects of heat flux and initial concentration of aqueous binary solution on both the melting behavior and the heat transfer characteristics of the slush ice. Photographs of flow patterns are presented, and dependence of the double-diffusion on the flow structure is discussed. The results obtained form present study have great importance and usefulness not only for design of the high efficient heat exchanger using the slush ice, but also for operations of the thermal energy storage system.

We have observed sliding at a cold (-17 oC) ice-rock interface beneath Meserve Glacier, Antarctica, and the segregation of ice into clean lenses amidst the dirty basal layers of this glacier. We interpret these as manifestation's of thin water films at ice-rock interfaces. We use Shreve's theory for sub-freezing sliding to esti- mate the nominal film thickness to be at least tens of nanometers. Such water films should exist around rocks in most polar ices, and likely have high solute concen- trations due to solute rejection during regelation and due to exchange with veins and grain boundaries where impurities reside.