Ice Layer Thickness Research Articles

Thermal tracking of meltwater retention in Greenland's accumulation area

Poorly understood processes controlling retention of meltwater in snow and firn have important implications for Greenland Ice Sheet's mass balance and flow dynamics. Here we present results from a 3 year (2007–2009) field campaign studying firn thermal profiles and density structure along an 85 km transect of the percolation zone of west Greenland. We installed one or two thermistor strings at 14 study sites, each string having 32 sensors spaced between 0 and 10 m depth. Data from our network of over 500 sensors were collected at 15–60 min intervals for 1–2 years, thereby recording the thermal signature of meltwater infiltration and refreezing during annual melt cycles. We document three types of heating of firn related to different mechanisms of meltwater motion and freezing, including heterogeneous breakthrough events, wetting front advance, and year‐round heating from freezing of residual deep pore water. Vertically infiltrating meltwater commonly penetrates through cold firn accumulated over decades, even where ice layers are present at the previous summer surface and where ice layer thickness exceeds several decimeters. The offset between the mean annual air temperature and the 10 m firn temperature reveals the elevation dependency of meltwater retention along our transect. The firn is > 10°C warmer than the mean annual air temperature at the region where meltwater runoff initiates. During 2007–2009, runoff was limited to elevations lower than ∼1500 m with no sharp “runoff limit”; rather, the ratio of retention to runoff transitioned from all retention to all runoff across a ∼20 km wide zone.

Numerical Heat Transfer Analysis of Flake Ice Storage System with Nanofluids

Ice Storage air-condition can be used to shift electrical load from on-peak hours to off-peak hours, which can bring mutual benefits to power supplier and consumers. An unsteady heat transfer numerical model is developed to predict the increment of thickness of ice layer of flake ice storage system with Cu-H2O nanofluids solidification. In this study, the speed of increment of ice layer of water and Cu-H2O nanofluids are compared.

An experimental and theoretical study of solidification in a free-convection flow inside a vertical annular enclosure

The natural convection and solidification in an annular enclosure has been studied experimentally and theoretically. Here the inner cylinder of the annular enclosure was cooled below the solidification temperature of the water, while the outer cylinder was kept on a uniform temperature well above 0 °C. The problem of the unsteady growth of the ice-layer on the inner cold cylindrical surface is studied theoretically and an approximate solution has been obtained for the quasi-steady development of the ice-layer thickness. In addition, it has been found that the influence of the contact layer between the frozen layer and the cold surface is of significant importance for the solidification process. Results are presented and compared between the experimental and the analytical investigation.

Development and validation of a one-dimensional snow-ice algae model against observations in Resolute Passage, Canadian Arctic Archipelago

[1] Ice algae are an important component of the carbon cycle in the Arctic. We investigate the dynamics of an ice algae bloom by coupling an ice algae-nutrient model with a multilayer σ coordinate thermodynamic sea ice model. The model is tested with the simulation of an algal bloom at the base of first-year ice over the spring. Model output is compared with data from Barrow Strait in the Canadian Arctic Archipelago. Snow cover, through its influence on ice melt, is a dominant factor controlling the decline of the bloom in the model, a finding that supports past studies. The results show that under a higher snow cover (20 cm), biomass in the early stages of the algal bloom is less than expected from the observed data. This discrepancy is due to the severely light-limited algal growth, despite the close match between simulated and observed under-ice photosynthetically active radiation. This result raises issues of how photosynthetic parameters as well as radiative transfer is represented in one-dimensional ice models. This study also shows that for higher algal concentrations, when biomass is split over multiple layers rather than concentrated in one layer at the ice base, there is a reduction in algae accumulation, a result of self shading. In addition, experiments show a sensitivity of total biomass to the oceanic heat flux and ice layer thickness, both of which affect biomass loss at the ice base. Being able to accurately model physical conditions is essential before the seasonal dynamics of ice algae can be accurately modeled, and some recommendations for improvement are discussed.

H ATOM IRRADIATION OF CARBON GRAINS UNDER SIMULATED DENSE INTERSTELLAR MEDIUM CONDITIONS: THE EVOLUTION OF ORGANICS FROM DIFFUSE INTERSTELLAR CLOUDS TO THE SOLAR SYSTEM

We present the results of experiments aimed at studying the interaction of hydrogen atoms at 80 K with carbon grains covered with a water ice layer at 12 K. The effects of H processing have been analyzed, using IR spectroscopy, as a function of the water ice layer. The results confirm that exposure of the samples to H atoms induces the activation of the band at 3.47 μm with no evidence for the formation of aromatic and aliphatic C-H bonds in the CH2 and CH3 functional groups. The formation cross section of the 3.47 μm band has been estimated from the increase of its integrated optical depth as a function of the H atom fluence. The cross section decreases with increasing thickness of the water ice layer, indicating an increase of adsorption of H atoms in the water ice layer. A penetration depth of 100 nm has been estimated for H atoms in the porous water ice covering carbon grains. Sample warm-up at room temperature causes the activation of the IR features due to the vibrations of the CH2 and CH3 aliphatic functional groups. The evolution of the 3.47 μm band carrier has been evaluated for dense and diffuse interstellar clouds, using the estimated formation cross section and assuming that the destruction cross section by energetic processing is the same as that derived for the 3.4 μm band. In both environments, the presence of the 3.47 μm band carrier is compatible with the evolutionary timescale limit imposed by fast cycling of materials between dense and diffuse regions of the interstellar medium. In diffuse regions the formation of the CH2 and CH3 aliphatic bands, inhibited in dense regions, takes place, masking the 3.47 μm band. The activation of the CH2 and CH3 aliphatic vibrational modes at the end of H processing after sample warm-up represents the first experimental evidence supporting an evolutionary connection between the interstellar carbon grain population, which is responsible for the 3.4 μm band (diffuse regions) and contributes to the absorption at 3.47 μm (dense regions), and the organics observed in interplanetary dust particles and cometary Stardust grains.

Simulation and Experimental Investigation of DC Ice-Melting Process on an Iced Conductor

Ice melting with dc is one of the key technologies to prevent the Chinese power grid from ice storms. Especially after the severe ice storm in the southern part of China in early 2008, dc ice-melting technology has drawn more attention than ever before. However, there are few satisfactory methods to select correct parameters so the ice-melting project rarely achieves desired effects in some cases when applied in Hunan, Guizhou, and other provinces in China. Therefore, it is of great significance to develop a method to estimate parameters which is applicable in the practical situation for dc ice melting. To handle this, the factors, such as wind velocity, ambient temperature, current density and ice-layer thickness were analyzed and then a dc ice-melting model is put forward in this paper. Both the results of simulations and experiments show that the ice-melting process can be divided into three stages composed of temperature rising, ice melting, and ice shedding, among which the ice melting is the key stage consuming most of the ice-melting time. In this stage, an elliptic airgap is formed and widened gradually with an influence on the ice-melting time and the temperature of the conductor. The experiments in the artificial climate chamber demonstrate that the results of the presented model are consistent with those of the experiments generally, so it can be employed to estimate the parameters of ice melting in practical engineering as reference.

Ice layers as an indicator of summer warmth and atmospheric blocking in Alaska

AbstractSamples were collected from a snow pit and shallow firn core near Kahiltna Pass (2970 m a.s.l.), Denali National Park, Alaska, USA, in May 2008. The record spans autumn 2003 to spring 2008 and reveals clusters of ice layers interpreted as summertime intervals of above-freezing temperatures. High correlation coefficients (0.75–1.00) between annual ice-layer thickness and regional summertime station temperatures for 4 years (n = 4) indicate ice-layer thickness is a good proxy for mean and extreme summertime temperatures across Alaska, at least over the short period of record. A Rex-block (aka high-over-low) pattern, a downstream trough over Hudson Bay, Canada, and an upstream trough over eastern Siberia occurred during the three melting events that lasted at least 2 weeks. About half of all shorter melting events were associated with a cut-off low traversing the Gulf of Alaska. We hypothesize that a surface-to-bedrock core extracted from this location would provide a high-quality record of summer temperature and atmospheric blocking variability for the last several hundred years.

鉛直角管路内の層流片側冷却における非定常凝固特性 : 浮力の効果による速度分布の変化と凝固に与える影響(熱工学,内燃機関,動力など)

Numerical and experimental studies on forced and mixed convection heat transfer and freezing for low Reynolds numbers in a vertical duct with asymmetric side-wall cooling at a subzero temperature have been conducted. Numerical results on the ice-layer thickness at steady state were compared with experimental measurements, and a qualitative agreement was observed. It is found that, after the cooling is initiated, a new velocity profile of the main stream, which is formed under the influence of buoyancy, develops in a short time. As the ice-layer grows thicker, however, the parabolic velocity profile is recovered again. The experimental measurements are also in fair agreement with the analytical predictions based on Graetz theory. However, in the experiment, the super cooling always takes place over the entire cooling surface, and it delays the ice formation significantly. The same super cooling was observed at high Reynolds numbers. Consequently, in the growth limit of solidification, the average thickness of ice-layer is found to be proportional to about -1/3 power of the Reynolds number.

The morphology of ice-structure in a planar nozzle subjected to forced internal convection flow

The present paper deals with the ice-formation in a planar nozzle with various convergence angles. Experiments have been carried out for different wall cooling parameters B in the range between 4 and 25 and for different flow rate Reynolds numbers in the range of 5,000 < Re4h < 50,000 for two different convergence angles of the nozzle. For all experiments with the larger convergence angle of the nozzle (2.5°), only smooth ice-layers could be observed. However, for the nozzle with the smaller convergence angle (1.25°), also wavy ice-layers could be detected. This interesting result is a justification for the hypothesis that the formation of wavy ice-layers is caused by flow laminarisation (due to the rapid growth in ice-layer thickness with increasing axial position from the inlet) and retransition to the fully turbulent state (after the acceleration falls below a certain critical value). Thus, this paper proves for the first time, that wavy ice-layers are suppressed by superimposed strong flow acceleration.

Modeling of frost salt scaling

This paper discusses the numerical modeling of deterioration in cement-based materials due to frost salt scaling (FSS). Several aspects of FSS are investigated such as carbonation, microstructure, mechanical properties and testing conditions. Mainly blast-furnace slag cement (henceforth slag cement) systems are of interest in this paper since several reports have been indicated that cementitious materials bearing slag-rich cement are critically vulnerable under combined attack of frost and de-icing salts. In the first part, the paper deals with the effect of carbonation on the micromechanical properties and FSS resistance of 1-year-old slag cement and ordinary Portland cement pastes with W/C 0.45. The micromechanical properties were evaluated by the nano-indentation technique and the results are used to evaluate the behavior of these pastes under frost salt attack. FSS damage on the paste samples is modeled according to the glue-spall theory with the aid of Delft Lattice Model. Additionally, the carbonated cement paste microstructures are characterized by ESEM/BSE. In the second part, parameters that are varied in the investigation are the salt concentration in the external water layer and ice-layer thickness on the surface. Again the lattice type model is used to simulate the mechanism in which the material structure is implemented using digital images of the real material. Both experiments and the simulation with the model show that the amount of scaling increases with increasing thickness of the ice layer on the surface. Furthermore it is shown that with the model the well known pessimum effect for salt concentration in the water (which causes maximum damage at 3% salt) can be reproduced. The outcome of the model indicates that glue-spall theory can successfully explain FSS.

On the Measurement of Thickness of Ice Layers on Power Transmission Lines

In this paper, measurement of ice and ice/water layer thickness on power transmission lines using Goubau modes at 1, 2.54 and 10 GHz is analyzed, simulated and discussed. Ice layer thicknesses change the phase and attenuation of Goubau mode propagation over a given line length. It is found feasible to determine layer thickness by measuring the phase and attenuation of the Goubau mode at a few GHz. In addition to the thickness, it is also possible, to determine the composition of the layer by measuring the different dielectric properties of ice, water and their mixture over a wide bandwidth to develop a database for comparison with measured data. The sensitivity of suggested instrumentation is sufficient for short line lengths (up to 1 m) or long lengths (several km). The implementation of instrumentation on long lines is still to be done but no major obstacles are foreseen. The decision to de-ice transmission line using any given and established techniques is facilitated if average ice thickness on transmission line between supporting transmission line towers can be measured.

One-dimensional ice growth due to incoming supercooled droplets impacting on a thin conducting substrate

A one-dimensional model for ice accretion due to incoming supercooled water impacting on a conducting substrate is developed, where the substrate is cooled from below by a liquid or gas. Both rime and glaze ice situations are considered. Non-dimensionalisation shows that conduction is the dominant method of heat transfer and so the heat equations are reduced to pseudo-steady forms. In this case the problem reduces to solving a single equation for the ice layer thickness. The water height and temperatures in the ice, water and substrate may subsequently be found. The asymptotic solution is validated by comparison with results from a numerical scheme which solves the full Stefan problem. This is an extension of a previously published solution method that involved simpler boundary conditions. For glaze ice, a comparison including water droplet energy either in the boundary conditions or as a source term in the heat equations, is also performed.

Three-Dimensional Characterization of Cryogenic Target Ice Layers Using Multiple Shadowgraph Views

Backlit optical shadowgraphy is the primary diagnostic for D2 ice layer characterization of cryogenic targets for the OMEGA Laser System at the Laboratory for Laser Energetics (LLE). Reflection and refraction of light passing through the ice layer produce characteristic rings. The position of the most prominent of the shadowgraph rings, known as the bright ring, can be resolved to ∼0.1-pixel rms, corresponding to about 0.12 μm for typical LLE target shadowgraphs. Measurement of the bright ring position in conjunction with ray-trace model predictions determines the ice layer thickness and the Fourier-mode spectrum of the ice roughness for that view. The LLE target characterization stations use two camera angles and target rotation to record target shadowgraphs from many different views. Combining these views allows construction of a 3-D ice layer representation, an estimation of the global surface roughness, and a determination of a Legendre-mode spectrum suitable for implosion modeling. The standard operating procedure is to construct a 3-D ice layer representation using the analysis of 48 separate shadowgraphic views. The 3-D ice surface is then decomposed in terms of spherical harmonics, allowing the determination of low-mode number (ℓ ≤ to 10) elements of a Legendre-mode power spectrum. Higher-mode number elements of the Legendre power spectrum are determined by mapping the Fourier-mode power spectrum averaged over all views

Optimum design of vaporizer fin with Liquefied Natural Gas by numerical analysis

Generally, the temperature drop under 0℃ on vaporizer surface creates frozen dews. This problem seems to increase as the time progress and humidity rises. In addition, the frozen dews create frost deposition. Consequently, heat transfer on vaporizer decreases because frost deposition causes adiabatic condition. Therefore, it is very important to solve this problem. This paper aims to study of the optimum design of used vaporizer at local LNG station. In this paper, experimental results were compared with numerical results. Geometries of numerical and experimental vaporizers were identical. Studied parameters of vaporizer are angle between two fins (Φ) and fin thickness (TH F ). Numerical analysis results were presented through the correlations between the ice layer thickness (TH ICE ) on the vaporizer surface to the temperature distribution of inside vaporizer (T IN ), fin thickness (TH F ), and angle between two fins (Φ). Numerical result shows good agreement with experimental outcome. Finally, the correlations for optimum design of vaporizer are proposed on this paper.

A measurement method of ice layer thickness based on resistance-capacitance circuit for closed loop external melt ice storage tank

The measurement of the ice layer thickness in closed loop external melt ice storage tank not only affects the optimal operation of the ice storage system but also directly determines the safety of the system. The traditional methods could not satisfy the needs of rapidity and accuracy very well. A measurement method to quickly and accurately predict the thickness of ice layer is presented in this paper. Based on the differences of permittivity and resistivity between ice and water, the frequency response principle of resistance–capacitance circuit is applied to develop a measuring unit of ice layer thickness. The interpolation method is used in the transducer to increase the precision of this device. Experimental and analytic results show that the sensor is accurate enough for industrial application and has remarkable rapidity and stability in measuring the ice thickness on the plate or ice on the coil, which can be used to calculate the ice packing factor (IPF) of the ice storage system.

Temporal changes in the radiophysical properties of a polythermal glacier in Spitsbergen

AbstractIn order to study the seasonal and inter-seasonal variations in radio-wave velocity (RWV), radiophysical investigations were made at Hansbreen, a polythermal glacier in Spitsbergen, in July– August 2003 and April 2004. These investigations included repeated radar profiling (20 and 25 MHz) along a transverse profile, repeated common-midpoint measurements, continuous radar measurements during 8 days at a fixed site, meteorological observations, and continuous ice surface velocity monitoring by differential GPS. Seasonal and inter-seasonal RWV changes in the temperate ice layer are attributed, respectively, to rapid water redistribution within it during the summer, and to variations in water content from 2.1% in summer to 0.4% in spring. The reflection properties of the temperate ice layer correlate well with the air temperature, with a nearly semi-diurnal time lag. The temporal variability of the reflection properties of the internal horizon suggests enlargement of water inclusions or water drainage from the horizon. Repeated profiling shows a stable spatial pattern in bed reflection power interpreted as changes in water content controlled by bedrock topography. The spatial variations of internal reflection energy along the repeated profile correlate with the thickness of the cold ice layer and the occurrence of drainage and crevasse systems.

Spatial distribution of surface mass balance on Amundsenisen plateau, Antarctica, derived from ice-penetrating radar studies

AbstractThe distribution of surface mass balance on Amundsenisen, Dronning Maud Land, Antarctica, is investigated along a continous profile line. Ice-penetrating radar is used to map variations in ice-layer thickness within the upper 100 m of the ice sheet. The route passes several firn- and ice-core drilling sites over a distance of 320 km. Dielectric-profiling data of ice cores are used to calculate the depths of selected reflection horizons and the cumulative mass of the ice column. The local surface mass balance is determined as a temporal average, covering a time-span of almost two centuries. The findings indicate a complex accumulation pattern superimposed on a generally low surface mass balance, which is related to small-scale surface undulations. The results of the radar soundings are in general in good agreement with surface mass-balance data derived from firn-core studies. Discrepancies between these two datasets can be explained by spatial mismatch or by minor quality of either ice-core profiles or radar data. For regional comparison of radar-based accumulation data we use an accumulation distribution interpolated from point measurements. The surface mass balance varies up to 50% over short distances, with correlation lengths of &lt;10 km. We conclude that the current utilization schemes of point sampling are only capable of reproducing local values and regional trends but provide no information on the small-scale variability of surface mass balance.

The drainage pattern of Hansbreen and Werenskioldbreen, two polythermal glaciers in Svalbard

To improve our understanding of Svalbard-type polythermal glacier drainage, hydraulic geometry models of the subglacial hydrology of two contrasting glaciers in Svalbard have been constructed. The models are tested against a uniquely long and rich set of field observations spanning 45 years. Digital elevation models (DEMs) were constructed from bedrock data measured with ground penetrating radar and surface data of two medium-sized polythermal glaciers, Hansbreen and Werenskioldbreen, in south-west Spitsbergen. Hansbreen has a low angle bed with over-deepenings and a calving front, while Werenskioldbreen has steeper bed and terminates on land. Together they are representative of many Svalbard glaciers. The DEMs were used to derive maps of hydraulic potential and subglacial drainage networks. Validation of the models was done using field observations including location mapping and speleological exploration of active moulins, positions of main river outflows, dyetracing and water chemistry studies, and observations of water pressure inside moulins. Results suggest that the water pressure is generally close to ice overburden pressure but varies greatly depending on local conditions such as bed location, the thickness of cold ice layer, the thickness of the glacier and seasonal changes in meltwater input.

Probing Europa's interior with natural sound sources

Europa's interior structure may be determined by relatively simple and robust seismo-acoustic echo sounding techniques. The strategy is to use ice cracking events or impacts that are hypothesized to occur regularly on Europa's surface as sources of opportunity. A single passive geophone on Europa's surface may then be used to estimate the thickness of its ice shell and the depth of its ocean by measuring the travel time of seismo-acoustic reflections from the corresponding internal strata. Quantitative analysis is presented with full-field seismo-acoustic modeling of the Europan environment. This includes models for Europan ambient noise and conditions on signal-to-noise ratio necessary for the proposed technique to be feasible. The possibility of determining Europa's ice layer thickness by surface wave and modal analysis with a single geophone is also investigated.

A study on effects of process parameters in rapid freeze prototyping

Rapid freeze prototyping is a relatively new solid freeform fabrication process, which builds a three‐dimensional part according to a CAD model by depositing and freezing water droplets layer by layer. A study on the effects of RFP process parameters including the nozzle scanning speed, droplet size, and droplet frequency in building ice parts with a single‐nozzle work head is made. Presented in this paper are the results of this study which indicate that these process parameters determine the ice layer thickness and ice line width, which in turn determine the surface roughness and the waiting time required after depositing each layer of water (i.e. between successive layers) during the ice part building process.