Ice-melting Models Research Articles

Spatial pattern of the debris-cover effect and its role in the Hindu Kush-Pamir-Karakoram-Himalaya glaciers

Supraglacial debris is widespread on the Hindu Kush-Pamir-Karakoram-Himalaya (HPKH) glaciers, which influences ice melt rates and glacier response to climate change, with important consequences for regional water resources. Supraglacial debris has shown an expanding trend with glacier shrinkage and mass loss, but knowledge about regional spatial patterns of debris cover and associated impacts on HPKH glaciers is still incomplete, which markedly affects the assessment accuracy of regional debris-covered glacier status and hydrological impacts. Here, we address these issues based on ASTER imagery, glacier inventory, and a physically-based ice melt model. We find that about 14.3 % of the regional glacier area is covered by supraglacial debris, and its thickness decreases gradually from northwest to southeast of the region overall. Except for the glaciers of western Himalaya and Karakoram, where the acceleration effect of debris cover is dominant, the insulation effect of debris cover on the glaciers of Pamir, Hindu-Kush, central and eastern Himalaya is particularly significant. The heterogeneous distribution of debris thickness and the resulting melt hotspots (ice cliffs and supraglacial ponds) enhance debris-covered surface thinning in the HPKH region, but it is not the dominant cause of surface thinning. Overall, the net effect of considering spatially distributed debris thickness can reduce total mass loss of debris-covered glaciers by 0.44 ± 0.04 m water equivalent (w. e.) yr−1. As a result, the presence of debris cover retards accelerated glacier melting caused by current climate warming, with important implications for slowing down regional water shortage and ecological environment risk in the HPKH region. Our findings highlight the importance of including the debris-cover effect in regional glacier models for assessing future glacier change and associated hydrological impacts in the HPKH region.

Effect of shape parameters on the enhancement of ice-melting performance in a novel perforated gas diffusion layer of proton exchange membrane fuel cell

To explore ice-melting process in a perforated gas diffusion layer and an effective and efficient GDL structure to enhance ice melting performance, a three-dimensional ice-melting model was established via lattice Boltzmann method based on enthalpy. The modified curved boundary condition was used in the model to consider complex carbon fiber surface. The influence of the hole shape parameters on ice melting was investigated. The main finding of the work is that the ice in a perforated gas diffusion layer can be melted faster than that in a conventional gas diffusion layer, which means that perforated gas diffusion layer has better ice melting ability. The width mainly influences the enhancement area of heat transfer. When the Fourier number is 0.1, as the width increases, the melting rate increases from 0.55 to 0.62. If the hole depth is larger than 0.5 times the thickness of the gas diffusion layer, the hole can act to enhance the ice melting. The maximum ice melting rate at a Fourier number of 0.1 is only 0.59. The increasing number of holes makes the temperature more evenly distributed. When the Fourier number is 0.1, as the number increases, the ice melting rate increases from 0.55 to 0.62.

Numerical Modeling and Parametric Study of the Melting Behavior of Ice Crystal Particles

Ice crystal icing has been identified as a risk to flight safety, due to its ability to reduce engine performance and its potential to cause engine damage and flameout. A critical factor in the sticking efficiency of ice crystals is the melting behavior of ice crystals. This paper presents an ice melting model integrated with surface blowing and porosity. A parametric study is performed to understand the effects of flow conditions (total pressure, humidity, total temperature, Mach number, and slip velocity) and particle properties (particle size, aspect ratio, and porosity factor) on ice melting behavior. The model is compared against the melting time of single ice particles in an acoustic levitator. The results show that employing sphericity and porosity could improve prediction performance. Surface blowing from evaporation increases melting time, and its effect is larger with a higher gas temperature. Ice melting time increases with pressure at high humidity, whereas an opposite trend is observed at low humidity. Increasing gas temperature, humidity, slip velocity, aspect ratio, and particle temperature can decrease ice melting time, whereas increasing Mach number, particle size, and porosity factor can increase ice melting time. Although wet bulb temperature can be used to evaluate ice melting potential when only one flow parameter is varied, it appears insufficient alone under scenarios where multiple flow parameters are changing simultaneously.

Assessment of adaptive capacity to sea level rise using open-loop system, case study: Cirebon and Pangandaran

This research aims to assess the adaptive capacity of three adaptive strategies applied in Cirebon and Pangandaran by estimating community assets under threat of Sea-Level Rise (SLR) through open-loop system. Firstly, SLR in Cirebon and Pangandaran each month from 2006 to 2100 is simulated using ocean heat flux and ice melting model data by Representative Concentration Pathways (RCP) 8.5, Intergovernmental Panel of Climate Change Assessment Report (IPCC AR) 5. This simulation result is then added with ocean phenomena such as tide, Indian Ocean Dipole (IOD), Madden-Julian Oscillation (MJO), storm surge, and Kelvin wave along with their frequencies. By the year 2100, the sea level in Cirebon will reach 115.65 cm and 148.09 cm in Pangandaran. Secondly, the SLR and applied strategies are converted to be inundation maps of community assets. Overall, the result shows the best policy for both regencies is protect which has an adaptive capacity value of 96.30% and 76.65% respectively. But deeper, the adaptive strategy for each district in both regencies differs one to another.

Experimental and numerical investigation of the performance of bogie chassis heater deicing systems

In winter, a large amount of icing and snowing occurs in outdoor equipment and systems, which adversely affects their lifespan. The melting process is divided into two parts: convection melting and gravity shedding melting. This paper is based on an experiment with a real high-speed train unit, and it establishes a three-dimensional computational fluid dynamics model of the bogie area to validate the mathematical model of the winter ice melting experiment. A numerical simulation was used to calculate the airflow in the baffle-enclosed space and to predict the effects of interactions between air and the ice body on heat transfer and phase change. The influence of air velocity and temperature on the heat transfer was analyzed. The computational simulation effectively quantifies the amount of heat transfer and energy consumption under different conditions. This paper also presents a research method for the simulation of gravity shedding in complex models. These models provide information for the construction of similar ice melting models. This paper has suggested that for thin ice bodies, convection melting was the dominant strategy. For thick ice bodies, however, gravity shedding melting became dominant. The study also confirmed that enclosed hot-air ice-melting systems gave a better energy performance than unenclosed systems.

Numerical Simulation of Bohai Oil Spill in the Winter Sea Ice Period

The Bohai Sea is a seasonal icy sea area that has the lowest latitude of any sea experiencing icing in the northern hemisphere, and simulation studies on oil spills during its sea ice period are the key to analyzing winter oil spill accidents. This study applied the three-dimensional free surface to establish a high-resolution hydrodynamic model and simulate tidal distributions in the Bohai Sea. Then, the oil spill model of the open sea area and thermodynamic model were combined to establish a numerical model for the Bohai oil spill during the winter sea ice period. The hydrodynamic model and sea ice growth and melting model were verified, and the parameters were adjusted based on the measured values, which indicate that the numerical model established in this paper is of high accuracy, stability and ubiquity. Finally, after checking the calculations repeatedly, the diffusion coefficient for the Bohai Sea was determined to be 1.0×10–7 m2/s. It is better that the comprehensive weathering attenuation coefficient is lower than that of a non-winter oil spill, with 1.3×10–7 m2/s being the most appropriate coefficient. This study can provide the reliable technical support for the operational safety and reduction in losses caused by winter oil spill accidents for the petroleum industry.

Ice cover decay and heat balance in Lake Kilpisjärvi in Arctic tundra

To gain more understanding of lake ice melting process, field research was carried out in an arctic tundra lake, Kilpisjärvi (surface area 37.1 km2, maximum depth 57 m) in the melting periods of 2013 and 2014. The heat budget of the ice cover was dominated by the radiation balance; turbulent heat fluxes were large in 2013 due to warm air advection but small in 2014. Transmittance of solar radiation through ice was 0.25 in 2013 and 0.10 in 2014, snow-ice was absent in 2013 but in 2014 accounted for 50% of the ice cover. The melting rate was 4.4 cm d-1 in 2013, 1.9 cm d-1 in 2014. The portions of surface, bottom and internal melting were, respectively, 2.9, 1.0 and 0.5 cm d-1 in 2013 and 0.8, 1.0 and 0.1 cm d-1 in 2014. Internal melting was realized in increase of ice porosity. In 2013 a rapid ice breakage event completed the ice breakup in short time when ice porosity had reached 40-50%. A lake ice melting model should include the thickness and porosity of ice, with porosity connected to an ice strength criterion.

Beneficial mutation-selection dynamics in finite asexual populations: a free boundary approach

Using a free boundary approach based on an analogy with ice melting models, we propose a deterministic PDE framework to describe the dynamics of fitness distributions in the presence of beneficial mutations with non-epistatic effects on fitness. Contrarily to most approaches based on deterministic models, our framework does not rely on an infinite population size assumption, and successfully captures the transient as well as the long time dynamics of fitness distributions. In particular, consistently with stochastic individual-based approaches or stochastic PDE approaches, it leads to a constant asymptotic rate of adaptation at large times, that most deterministic approaches failed to describe. We derive analytic formulas for the asymptotic rate of adaptation and the full asymptotic distribution of fitness. These formulas depend explicitly on the population size, and are shown to be accurate for a wide range of population sizes and mutation rates, compared to individual-based simulations. Although we were not able to derive an analytic description for the transient dynamics, numerical computations lead to accurate predictions and are computationally efficient compared to stochastic simulations. These computations show that the fitness distribution converges towards a travelling wave with constant speed, and whose profile can be computed analytically.

Analysis of ice disasters on ultra-high-voltage direct-current transmission lines

Ice disaster is one of the biggest natural disasters posing great threat to the safe operation of power grid. With the construction and operation of ultra-high-voltage direct-current (UHVDC) Transmission Project, it is urgent to carry out research on ice-coating and ice-melting of large-section current-carrying conductors to provide technical support for the safe operation of UHVDC transmission project. Researchers have made a large amount of research on small-section conductors. However, these research results for small-section conductors cannot be applied to large-section conductors. Thus, our research team carries out the research on ice-coating and ice-melting of large-section current-carrying conductors under artificial conditions. The typical large-section current-carrying conductor LGJ-630/55 is employed to analyze the ice-coating and ice-melting characteristics of large-section current-carrying conductors with some main factors, including wind, precipitation, temperature, current, and so on. Based on the experiments’ results, we have arrived at several rules of ice-coating and ice-melting of large-section current-carrying conductors. Meanwhile, an improved Ice-melting Model taking account Heat Exchange and Gravity (IMHEG) is proposed in this paper. This IMHEG model is verified to be more proper than the traditional ice-melting model, and can be a useful model for practical application.

Asynchronism of ice shedding from the de‐iced conductor based on heat transfer

When overhead line is de-iced using Joule-effect heating, which is one of the main methods for resisting ice disasters in cold regions, the ice layer on the conductor will always be shed by section. However, the asynchoronism of ice shedding based on heat transfer is ignored in almost all ice melting models of de-iced conductors. On the basis of an ice-melting simulation of a three-dimensional model of a de-iced conductor, the effects of wind velocity and ambient temperature on the asynchoronism of ice shedding is analysed with the experimental results from a natural icing station. The influence of the two factors on the allowable current of de-iced is also discussed. The variation of wind velocity along the de-iced conductor is considered as the cause of the asynchoronism of ice shedding. The ice shedding rate is higher with lower wind velocity or higher ambient temperature. The relationships between the allowable current and wind velocity or ambient temperature are segmented, which could be a reference to the ice melting conducted by Joule-effect methods.

Coupling a glacier melt model to the Variable Infiltration Capacity (VIC) model for hydrological modeling in north-western China

For the sustainable utilization of rivers in the mid and downstream regions, it is essential that land surface hydrological processes are quantified in high cold mountains regions, as it is in these regions where most of the larger rivers in China acquire their headstreams. Glaciers are one of the most important water resources of north-west China. However, they are seldom explicitly considered within hydrological models, and climate-change effects on glaciers, permafrost and snow cover will have increasingly important consequences for runoff. In this study, an energy-balance ice-melt model was integrated within the Variable Infiltration Capacity (VIC) macroscale hydrological model. The extended VIC model was applied to simulate the hydrological processes in the Aksu River basin, a large mountainous and glaciered catchment in north-west China. The runoff components and their response to climate change were analyzed based on the simulated and observed data. The model showed an acceptable performance, and achieved an efficiency coefficient R2 ≈ 0.8 for the complete simulation period. The results indicate that a large proportion of the catchment runoff is derived from ice meltwater and snowmelt water. In addition, over the last 38 years, rising temperature caused an extension in the snow/ice melting period and a reduction in the seasonality signal of runoff. Due to teh increased precipitation runoff, the Aksu catchment annual runoff had a positive trend, increasing by about 40.00 × 106 m3 per year, or 25.7 %.

DC Ice-Melting Model for Elliptic Glaze Iced Conductor

Both practices and experiments show that the cross-section shape of iced conductor has an obvious influence on ice-melting time, but it is ignored by almost all existing ice-melting models which assume that the iced conductor has a perfect circular cross-section shape. Based on the observed results in the natural icing station, this paper has analyzed the shape characteristic of the iced conductor, and described the cross-section shape of iced conductor with an ellipse, then put forward a model to simulate the ice-melting process on an iced conductor with an elliptic cross-section. The simulated results have been validated in the natural icing station. The results of experiments and simulations show that the ice-melting time of the elliptic iced conductor is less than that of the circular iced conductor.

Climate change effects on snow melt and discharge of a partly glacierized watershed in Central Switzerland (SoilTrec Critical Zone Observatory)

A comprehensive hydrological modeling study in the drainage area of a hydropower reservoir in central Switzerland is presented. Two models were tested to reproduce the measured discharge dynamics: (1) a detailed energy-balance model (ALPINE3D) primarily designed for snow simulations; (2) a conceptual runoff model system (PREVAH), including a distributed temperature-index snow and ice melt model. Considerable effort was put into distributing available meteorological station data to the model grids as forcing data. The recent EU regional climate modeling initiative ENSEMBLES provided up-to-date climate predictions for two 30-a periods in mid and late 21st century. These were used to estimate evolutions in the water supply of the hydropower reservoir in response to expected climate changes. The simulations suggest a shift of spring peak-flow by almost two months for the end of the century. Warmer winter temperatures will cause higher winter base-flow. Due to glacier retreat, late-summer flow will decrease at the end of the century.

DC ice-melting model for wet-growth icing conductor and its experimental investigation

Icicles are often formed under the downside surface of conductor in the wet growth icing of overhead power line. When the ice deposit around overhead power line is molten by Joule heat produced by current, the pattern of heat transfer of ice deposit with icicles is dissimilar to that without icicle, so the ice-melting model for the columnar icing conductor cannot be applied to icicle-shaped icing conductor. According to the heat-transfer characteristic of the icicle-shaped icing conductor, this paper puts forward a DC ice-melting model for the icicle-shaped icing conductor. Because this full model includes three-dimensional heat-transfer and interface movement, which cannot be solved in closed form, a finite element scheme in space-domain and a finite difference scheme in time-domain are employed to discretize the governing equations. Firstly the whole ice-melting process on the icicle-shaped icing conductor is simulated by this model. Then the simulated results are validated by ice-melting experiments in the artificial chamber. The study from the model and the experiments shows that the size and length of icicle as well as the space between the adjacent icicles are factors to affect ice-melting. With the shorter icicle space, the bigger icicle size and the longer icicle-length, the surface of ice layer is enlarged and then more heat is taken away by the convection and radiation, so the ice melting time will get longer.

Hydrological modelling of glacierized catchments focussing on the validation of simulated snow patterns – applications within the flood forecasting system of the Tyrolean river Inn

Abstract. The catchment of the river Inn is located in the Swiss and Austrian Alps. In the frame of the flood forecasting system "HoPI" (Hochwasserprognose für den Tiroler Inn), the Austrian part of the river Inn and its tributaries are covered within a hybrid numerical model. The runoff from the glacierized headwaters of the south-western Inn tributaries is calculated using the Snow- and Icemelt Model "SES" which utilizes a spatially-distributed energy balance approach; within SES, the accumulation and melting processes for snow, firn, and ice are considered. It is of great importance that such a type of model is used in the simulation of alpine areas since in these regions stream flow is influenced by the accumulation and melt of snow and ice and snow-free glaciers have also the potential to increase or even induce flood flow. For a prototype of the forecast system, SES was calibrated using the snow depletion of a glacier, but later, following the first results during the operational mode, the model was recalibrated and validated using remotely-sensed data covering all 13 glacierized catchments. Using the final snow-parameter setting, a simulation run of 15 hydrological years without any state corrections achieved overall agreements between observed and simulated snow cover ranging from 68% to 88% for all individual catchments. Runoff was calibrated and validated using the data from three different gauges. A parameter set, including both validated snow and runoff parameters, was applied for the modelling of a fourth gauged catchment and also achieved accurate results. This final unique parameterization was transferred to the remaining, ungauged watersheds.

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.

Hydrological modeling in alpine catchments: sensing the critical parameters towards an efficient model calibration

For the Tyrolean part of the river Inn, a hybrid model for flood forecast has been set up and is currently in its test phase. The system is a hybrid system which comprises of a hydraulic 1D model for the river Inn, and the hydrological models HQsim (Rainfall-runoff-discharge model) and the snow and ice melt model SES for modeling the rainfall runoff form non-glaciated and glaciated tributary catchment respectively. Within this paper the focus is put on the hydrological modeling of the totally 49 connected non-glaciated catchments realized with the software HQsim. In the course of model calibration, the identification of the most sensitive parameters is important aiming at an efficient calibration procedure. The indicators used for explaining the parameter sensitivities were chosen specifically for the purpose of flood forecasting. Finally five model parameters could be identified as being sensitive for model calibration when aiming for a well calibrated model for flood conditions. In addition two parameters were identified which are sensitive in situations where the snow line plays an important role.

Flow and heat transfer simulations for the design of the Helsinki Vuosaari harbour ice control system

The accelerated growth of brash ice is a problem that the port operator has to deal with in busy cold region harbour basins. Flow and heat transfer simulations have to be used to investigate the ice control design options for the new Helsinki Vuosaari harbour. For that purpose, a flow and heat transfer solver has been modified to combine 3 types of empirical ice-melting models, i.e. the smooth ice model, the slightly rough ice model and the rough ice model, as the heat transfer boundary conditions. A simple bubbler model has also been developed into the flow solver to simulate the complicated bubble-driven water flow in the harbour basin. The ice control problem for the Vuosaari harbour has two parts. One is the supply of warm water across a narrow basin. A suction pump arrangement has been studied as an alternative to crossing the basin with a pipe. The thermal energy balance and the ice melting in the basin have been estimated numerically. The numerical investigations show that the heat-supply efficiency can be of the order of 95% if the suction is 5 m 3 /s while the warm water supply flow is 4 m 3 /s. The principal problem is how to combine the warm water supply and bubbler devices to melt ice effectively in the main harbour basin. Five design options with different warm water supply locations and bubbler arrangements have been studied using numerical simulations. A solution that provides fairly even ice-melting patterns for the berths has been found. More than 70% of the thermal input gets used for ice melting in the basin according to the simulation. The paper illustrates, how flow and heat transfer simulations can be used for the design of ice control systems. It shows that the use of bubbler lines may greatly improve the efficiency of warm water input in ice control.

Are basal Ediacaran (635 Ma) post-glacial “cap dolostones” diachronous?

A layer of shallow-water dolostone (“cap dolostone”) with idiosyncratic sedimentary structures was deposited across continental margins world-wide in the aftermath of the terminal Cryogenian snowball Earth. The dolostone has a global average thickness of 18.5 m and is interpreted stratigraphically in different ways in the current literature: as diachronous (top and bottom) and tracking glacioeustatic flooding, as semi-diachronous (bottom diachronous, top isochronous) and outlasting the flood, or as isochronous (top and bottom) and recording ocean-wide changes over time subsequent to deglaciation. Each interpretation carries a different implication for the timescale of cap dolostones and their isotopic signatures, and therefore for their origin. In northern Namibia, we studied the Keilberg cap dolostone (635 Ma) across the Otavi carbonate bank and down a contiguous submarine paleoslope to estimated depths of ∼ 0.5 km. We find giant wave ripples and other wave-generated structures in all areas, including the lower slope, pointing to a base-level change of large amplitude. No other formation in the carbonate succession contains wave-generated bedforms on the lower slope. Carbon isotope records from the bank are similar in shape and absolute value, irrespective of thickness. Slope records are also similar to one another, but different in shape and value from those on the bank. If the cap is isochronous, lower-slope waters were enriched in 13C by 2–3‰ compared with the bank, which seems improbable. If diachronous, the lower slope, upper slope and bank records collectively describe a sigmoidal δ 13C curve over time with a net decline of 4.4‰. In addition, a lateral gradient of 1.0‰/100 km existed from the inner to outer bank. If the flooding was rapid (< 10 kyr), as suggested by ice-melting models, the δ 13C change may reflect strong surface warming, methane release, and kinetic isotope effects associated with rapid carbonate production. If the transgression was prolonged (> 100 kyr), as implied by actualistic interpretation of paleomagnetic reversals in this and other cap dolostones, the δ 13C change could record Rayleigh distillation associated with the drawdown of a large atmospheric CO 2 reservoir, built up during the preceding snowball glaciation. Either way, the sedimentology and isotopes support the diachronous interpretation, and are inconsistent with the semi-diachronous and isochronous models. The base-level rise of ∼ 0.5 km implies a glacioeustatic origin, meaning that cap dolostone sedimentation was synchronous with land ice melting. This leaves the actualistic interpretation of reversal frequency and speed in cap dolostones in conflict with ice-melting models.

Sea ice and oxygen isotopes in Foxe Basin, Hudson Bay, and Hudson Strait, Canada

The summer distribution of sea ice meltwater and river runoff and the surface circulation in Foxe Basin, Hudson Bay, and Hudson Strait have been studied by oxygen isotope techniques. On the basis of oxygen isotope and salinity relationships, the reduction of surface salinity in summer in Foxe Basin is predominantly due to sea ice meltwater. River runoff and sea ice meltwater contribute equally to the summer surface layer in northern Hudson Bay. The isotopic data clearly show the flow of Foxe Basin water through Roes Welcome Sound into northwestern Hudson Bay, but no evidence for this outflow is found in the passages connecting Hudson Bay and Hudson Strait. Oxygen isotopes indicate that recent river runoff is concentrated in a narrow band along the south side of Hudson Strait. The wide variety of relationships between oxygen isotope ratios and salinity is explained by the known ice dynamics and the seasonal variability predicted from ice melting and freezing models.