Ice-water Interface Research Articles

Unraveling Molecular Mechanism on Dilute Surfactant Solution Controlled Ice Recrystallization.

Ice recrystallization (IR) is ubiquitous, playing an important role in many areas of science, such as cryobiology, food science, and atmospheric physics. However, controllable ice recrystallization remains a challenging task largely due to an incomplete understanding of the physical mechanism associated with ice recrystallization. Herein, we explore the molecular mechanism underlying the controlling of ice recrystallization by using different small amphiphilic molecules (surfactants) through joint experimental measurements and molecular dynamics simulation. Our experiment shows that in nonionic/zwitterionic surfactant solutions, the mean size of the recrystallized ice grains increases monotonically with the concentration of surfactants, whereas in the ionic surfactant solutions, the mean size of the recrystallized ice grains tends to increase first and then decrease with increasing the concentration, yielding a peak typically at ∼5 μM. Further sequential ice affinity purification experiments and molecular dynamics simulations show that the surfactants actually do not bind to ice directly. Rather, the different spatial distributions of counter ions and molecular surfactants in the interfacial regions (ice-water interface and water-air interface) and bulk region can markedly affect the mean size of the recrystallized ice grain.

Deep-learning-enhanced ice thickness measurement using Raman scattering.

In ice thickness measurement (ICM) procedures based on Raman scattering, a key issue is the detection of ice-water interface using the slight difference between the Raman spectra of ice and water. To tackle this issue, we developed a new deep residual network (DRN) to cast this detection as an identification problem. Thus, the interface detection is converted to the prediction of the Raman spectra of ice and water. We enabled this process by designing a powerful DRN that was trained by a set of Raman spectral data, obtained in advance. In contrast to the state-of-the-art Gaussian fitting method (GFM), the proposed DRN enables ICM with a simple operation and low costs, as well as high accuracy and speed. Experimental results were collected to demonstrate the feasibility and effectiveness of the proposed DRN.

Ice lens induced interfacial hydraulic resistance in frost heave

Frost heave and ice lens cause the failure of engineerings and change the soil structure in cold regions. It is known that the water migrates from the unfrozen zone to feed the ice lens, but the mechanism of water migration in the vicinity of the ice lens is not well understood. In this study, the water migration at the interface between the ice lens and soil particles is theoretically investigated. Pore water flows from the soil pores to the unfrozen film between the ice lens and soil particles to expands the integral ice lens. The kinetics of the microscopic flow in the unfrozen film produces the hydraulic resistance at the macroscopic interface between ice lens and soil particles. Based on the global mechanical equilibrium at the ice-water interface, the rate of frost heave is derived for freezing soils with and without a frozen fringe. An expression for the neutral stress in the frozen fringe is developed to predict the initiation of new ice lenses with considering the effect of anisotropic stress of ice. The impacts of overburden pressure, temperature gradient, and interfacial hydraulic resistance on the rate of frost heave are discussed. In a relatively thick frozen fringe, the interfacial hydraulic resistance is insignificant compared to the hydraulic resistance of frozen fringe. However, if the thickness of frozen fringe is less than a critical value the interfacial hydraulic resistance will play a dominant role in the frost heave. This research is expected to facilitate the improvement of frost heave models, studying the influence of the interfacial hydraulic resistance on the characteristic of frost heave with and without a frozen fringe.

An Under-Ice Hyperspectral and RGB Imaging System to Capture Fine-Scale Biophysical Properties of Sea Ice

Sea-ice biophysical properties are characterized by high spatio-temporal variability ranging from the meso- to the millimeter scale. Ice coring is a common yet coarse point sampling technique that struggles to capture such variability in a non-invasive manner. This hinders quantification and understanding of ice algae biomass patchiness and its complex interaction with some of its sea ice physical drivers. In response to these limitations, a novel under-ice sled system was designed to capture proxies of biomass together with 3D models of bottom topography of land-fast sea-ice. This system couples a pushbroom hyperspectral imaging (HI) sensor with a standard digital RGB camera and was trialed at Cape Evans, Antarctica. HI aims to quantify per-pixel chlorophyll-a content and other ice algae biological properties at the ice-water interface based on light transmitted through the ice. RGB imagery processed with digital photogrammetry aims to capture under-ice structure and topography. Results from a 20 m transect capturing a 0.61 m wide swath at sub-mm spatial resolution are presented. We outline the technical and logistical approach taken and provide recommendations for future deployments and developments of similar systems. A preliminary transect subsample was processed using both established and novel under-ice bio-optical indices (e.g., normalized difference indexes and the area normalized by the maximal band depth) and explorative analyses (e.g., principal component analyses) to establish proxies of algal biomass. This first deployment of HI and digital photogrammetry under-ice provides a proof-of-concept of a novel methodology capable of delivering non-invasive and highly resolved estimates of ice algal biomass in-situ, together with some of its environmental drivers. Nonetheless, various challenges and limitations remain before our method can be adopted across a range of sea-ice conditions. Our work concludes with suggested solutions to these challenges and proposes further method and system developments for future research.

Formation of a Hydrate Layer at a Gas–Water (Ice) Interface

The problem on the formation of a hydrate layer in a spherical particle with an ice core and on the surface of a gas bubble coming to the surface of a water was solved numerically. As a limiting scheme of hydrate formation in these cases, the diffusion mechanism, implying the diffusion of a gas (water) in the hydrate layer formed at the contact line between a gas and an ice or a water to the surface of contact of the hydrate with the ice, the water, or the gas, was adopted. A comparative analysis of the results of numerical calculations of the formation of a hydrate layer in the indicated cases with the corresponding experimental data made it possible to estimate the reduced coefficients of diffusion of a gas and water in such a hydrate layer. It is shown that the model of hydrate formation comprising kinetic relations, obtained as a result of the solution of a quasi-stationary diffusion equation, allows one to define the transformation of a water or a gas into the hydrate state with the use of a single empirical parameter having the dimensions of the diffusion coefficient. The qualitative and quantitative patterns of the formation of a hydrate particle, obtained with the use of the indicated kinetic relations, agree with the corresponding experimental data and theoretical calculations of other researchers, and by them, a large number of empirical parameters, which are not known in advance but should be determined, can be estimated.

Considerations on Protein Stability During Freezing and Its Impact on the Freeze-Drying Cycle: A Design Space Approach.

Freezing is widely used during the manufacturing process of protein-based therapeutics, but it may result in undesired loss of biological activity. Many variables come into play during freezing that could adversely affect protein stability, creating a complex landscape of interrelated effects. The current approach to the selection of freezing conditions is however nonsystematic, resulting in poor process control. Here we show how mathematical models, and a design space approach, can guide the selection of the optimal freezing protocol, focusing on protein stability. Two opposite scenarios are identified, suggesting that the ice-water interface is the dominant cause of denaturation for proteins with high bulk stability, while the duration of the freezing process itself is the key parameter to be controlled for proteins that are susceptible to cold denaturation. Experimental data for lactate dehydrogenase and myoglobin as model proteins support the model results, with a slow freezing rate being optimal for lactate dehydrogenase and the opposite being true for myoglobin. A possible application of the calculated design space to the freezing and freeze-drying of biopharmaceuticals is finally described, and some considerations on process efficiency are discussed as well.

LBM modelling of supercooled water freezing with inclusion of the recalescence stage

Once nucleated, the solidification process of supercooled water undergoes stages of recalescence, freezing, and solid cooling. In existing LBM models for predicting the water solidification process, the recalescence stage was often treated by simply setting the system temperature to 0 °C on account of the latent heat release. However, apart from the temperature rise, another important feature of the recalescence stage is the rapid growth of dendritic ice over the entire supercooled space, which was often overlooked. In this study the recalescence stage is included in the conventional LBM, aiming to quantify the effect of initial ice fraction distribution on the freezing kinetics of supercooled water.Good agreements are achieved between the predicted results and the experimental data on the kinetics of water freezing in terms of the local temperature variation, freezing rate and evolution of the ice-water interface. However, the conventional LBM without considering the recalescence stage provides a poor description of ice-water interface evolution. The discrepancy between the predicted results using models with and without considering the recalescence stage increases as the supercooling increases and rises to 31% for a supercooling of 20 °C. Moreover, the method based on the Stefan number proves valid in calculating the initial ice fraction over the entire spectrum of supercooling degrees, whereas for high supercooling degrees (>28.2 °C) the application of the enthalpy-based method leads to erroneous results. For water systems of small volume that often bear a supercooling more than 30 °C, the recalescence stage should be considered in the modelling.

Application of elastic parabolic equation solutions to acoustic reverberation in ice-covered underwater environments

Parabolic equation solutions can be obtained for underwater acoustic environments where elastic boundaries affect the acoustic propagation. One example of this situation is in the Arctic where a (potentially rough) ice layer is on top of the water column. The parabolic equation method shown here rigorously applies the zero-traction and fluid-elastic interface boundary conditions to obtain full field Green’s function estimates near the ice-water interface. This solution is crucial for calculation of recently derived reverberation estimates that require both horizontal and vertical derivatives of the complex acoustic field. Monostatic reverberation estimates for a rough under-ice interface are calculated for an upward refracting water sound speed profile and an elastic ocean bottom with a nearly fluid mud layer. These calculations could be used, for example, to estimate areal distribution of the ice layer roughness from azimuth-time dependence of acoustic reverberation measured in Arctic environments. Performance of the Pade rational function approach in the presence of thin ice cover and low shear speed ocean bottom layers will be addressed.

A time-domain model of high-frequency backscatter from sea ice with applications to upward looking sonar data analysis

Upward looking sonar (ULS) systems are commonly used in ice-covered environments to evaluate sea-ice draft and related characteristics (such as the ice thickness distribution). The involved backscatter data inversion algorithms are mostly based on estimating the two-way propagation time and using some simplifying assumptions which may result in significant limitations, uncertainties, and errors. This work is aimed to develop an improved remote sensing technique of sea-ice characterization based on a more detailed, physics-based analysis of the backscatter intensity time series, the echo shape. The underlying model accounts for two major mechanisms of high-frequency acoustic backscatter, the ice-water interface roughness and volume heterogeneity of the ice layer, provides an estimate of their relative contributions, and includes the echo parameterization in terms of ULS system characteristics (such as the frequency, transmitted pulse’ duration and shape, and the directivity pattern). Using this model, computer simulations were performed for the ULS received signal time series to provide a sensitivity analysis for various physical properties of the ice. Optimal parameters of the system to enhance the ice-properties’ inversion are suggested which, in particular, may result in a possibility to remotely discriminate between first-year and multi-year ice types. [Work supported by ONR.]

Phase-field model of graphene aerogel formation by ice template method

A phase-field model is exploited to simulate the microstructure of graphene aerogel formation during the water freezing process. The nucleation of ice grains and the graphene redistribution play significant roles in preparation of graphene aerogel by the ice template method. Our simulation clarifies the process of polycrystalline ice nucleation, the graphene redistribution between the ice-water interface and the anisotropic growth process of ice grains. The result shows that the morphology and size of the graphene wall structure in aerogel are derived from the comprehensive effects of ice nucleation, polycrystalline growth, and graphene diffusion. The present study therefore contributes to the understanding of graphene aerogel formation and provides guidance for experiments to design a high specific surface area, light weight, and high strength three-dimensional porous structure.

Thermal structure and water-ice heat transfer in a shallow ice-covered thermokarst lake in central Qinghai-Tibet Plateau

A large number of lakes and ponds are unevenly distributed over the Qinghai-Tibet Plateau (QTP). Little is known about their ice processes and thermal regimes. Seasonal ice mass balance, thermal regime and stratification of under-ice water were investigated in a shallow thermokarst lake in central QTP using in situ observations and global reanalysis data. Congelation ice grew to 60–70 cm depth while continuous surface sublimation caused a total ice loss of over 30 cm. The bulk lake temperature below ice remained above 3.0 °C through the ice freezing period and rose gradually up to 7–9 °C during the melting period. The vertical thermal structure of under-ice water consisted of a stable strongly stratified interfacial layer (IL) and an underlying convective layer reaching the lake bottom. A warm layer existed just beneath the IL since the middle equilibrium period and increased in thickness and temperature. There was seasonal variation of IL depth and temperature gradient in response to the ice thermodynamics and atmospheric conditions. The calculated daily water-ice heat flux (Fw) was of 10 W m−2 magnitude. Seasonal variation of Fw manifested both diffusive and convective heat transport to the ice-water interface. This study suggests that strong penetration of solar radiative flux is the dominant contributor to high Fw, which results in a relatively thin ice compared with other equivalent high-latitude climate.

Hidden biogeochemical anonymities under Antarctic fast ice

Climate change is negatively affecting the extent of summer sea ice and the global oceanic oxygen concentrations, it is therefore imperative to decipher the life processes under the Antarctic fast ice. The biogeochemical parameters like dissolved oxygen, inorganic carbon, macronutrients, phytoplankton, and chlorophyll a (Chl a) were studied under the fast ice (by drilling ∼1.8 m thick ice) around Larsemann Hills, East Antarctica during India’s Scientific Expedition to Antarctica (31-ISEA-2011/12 and 33-ISEA-2013/14). The waters under ice cover were characterized by hyperoxia (up to 10.6 ml/L). Macronutrient concentrations under sea ice were depleted (<0.1 μM NO3, PO4 and <2 μM SiO4); this could be ascribed to the nutrient demand from under ice algae. The water under the ice cover exhibited higher algal biomass (Chl a up to 6.1 mg/m3) and CO2 under saturation (pCO2 <10 μatm). This is reflected through the Spearman rank correlation indicating a negative correlation between Chl a and pCO2 (r=−0.41). The strong negative correlation between dissolved oxygen and pCO2 (r=−0.67) suggests that photosynthesis regulates the concentrations of both these climatically important gases. The waters under the sea ice cover had brownish mucilaginous aggregates comprised of tube-forming diatoms Berkeleya adelienses and Nitzschia lecointei. These unusual biogeochemical changes were seen only at the ice water interface, and not at deeper depths. This study suggests that with global warming and sea ice melting, Antarctica might witness phytoplankton community shifts.

Ice growth rate: Temperature dependence and effect of heat dissipation.

The transformation of liquid water into solid ice is arguably the most important phase transition on Earth. A key aspect of such transformation is the speed with which ice grows once it is nucleated. There are contradictory experimental results as to whether the ice growth rate shows a maximum on cooling. Previous simulation results point to the existence of such a maximum. However, simulations were performed at constant temperature with the aid of a thermostat that dissipates the heat released at the ice-water interface unrealistically fast. Here, we perform simulations of ice growth without any thermostat. Large systems are required to perform these simulations at constant overall thermodynamic conditions (pressure and temperature). We obtain the same growth rate as in previous thermostatted simulations. This implies that the dynamics of ice growth is not affected by heat dissipation. Our results strongly support the experiments predicting the existence of a maximum in the ice growth rate. By using the Wilson-Frenkel kinetic theory, we argue that such maximum is due to a competition between an increasing crystallization thermodynamic driving force and a decreasing molecular mobility on cooling.

A red tide in the pack ice of the Arctic Ocean

In the Arctic Ocean ice algae constitute a key ecosystem component and the ice algal spring bloom a critical event in the annual production cycle. The bulk of ice algal biomass is usually found in the bottom few cm of the sea ice and dominated by pennate diatoms attached to the ice matrix. Here we report a red tide of the phototrophic ciliate Mesodinium rubrum located at the ice-water interface of newly formed pack ice of the high Arctic in early spring. These planktonic ciliates are not able to attach to the ice. Based on observations and theory of fluid dynamics, we propose that convection caused by brine rejection in growing sea ice enabled M. rubrum to bloom at the ice-water interface despite the relative flow between water and ice. We argue that red tides of M. rubrum are more likely to occur under the thinning Arctic sea ice regime.

Ice Scallops: A Laboratory Investigation of the Ice-Water Interface.

Ice scallops are a small-scale (5-20cm) quasi-periodic ripple pattern that occurs at the ice-water interface. Previous work has suggested that scallops form due to a self-reinforcing interaction between an evolving ice-surface geometry, an adjacent turbulent flow field, and the resulting differential melt rates that occur along the interface. In this study, we perform a series of laboratory experiments in a refrigerated flume to quantitatively investigate the mechanisms of scallop formation and evolution in high resolution. Using particle-image velocimetry, we probe an evolving ice-water boundary layer at sub-millimeter scales and 15Hz frequency. Our data reveals three distinct regimes of ice-water interface evolution: A transition from flat to scalloped ice; an equilibrium scallop geometry; and an adjusting scallop interface. We find that scalloped ice geometry produces a clear modification to the ice-water boundary layer, characterized by a time-mean recirculating eddy feature that forms in the scallop trough. Our primary finding is that scallops form due to a self reinforcing feedback between the ice-interface geometry and shear production of turbulent kinetic energy in the flow interior. The length of this shear production zone is therefore hypothesized to set the scallop wavelength.

Reflection Characteristics of a Near-Interface Cavity in Ice at Supercritical Incidence

The long-range propagation modes in an acoustic channel under ice are basically caused by supercritical incidence. The energy distribution and transmission loss in the acoustic channel under ice are changed by a scatter in ice. The influence of a slender cylindrical cavity near and parallel to the ice-water interface on the sound propagation is analyzed using Fourier-Bessel series and Sommerfeld-Watson transformation. The research found that the acoustic field presents a beam in the mirror reflection direction at supercritical incidence, and the beam-width is proportional to secant of incident angle; meanwhile, the reflected coefficient is proportional to cosine of incident angle. The reflection coefficient increases with relative depth and Helmholtz number if the incident angle is a constant.

Spreading fully at the ice-water interface is required for high ice recrystallization inhibition activity

Although materials for ice recrystallization inhibition (IRI) are essential for the cryopreservation of cells and tissues, there exists no guiding mechanism for the design of such materials. Therefore, the construction of materials for IRI relies on the try-and-error strategy. Herein, through changing the tacticity of hydroxyl groups on poly(vinyl alcohol) (PVA) backbones with the affinities of PVAs to ice unchanged, we experimentally find IRI activity decreases significantly for isotactic PVA in comparison to that of atactic PVA. Molecular dynamics simulation shows atactic PVA spreads fully at the ice-water interface due to its much stronger interaction with water. This indicates atactic PVA can cover more ice surface and possess a higher IRI activity when the same amount of PVAs are used, which is consistent with the results that PVA can cover the same amount of ice surface more efficiently through experimentally measuring the adsorption of PVAs on the ice surface. A guiding mechanism of high active IRI materials can be obtained: only having affinity to ice is not enough to obtain high IRI activity ( i.e ., only small amount of materials is required to reduce the size of ice crystals to ca. (35± 10) μm), IRI agents must also have high affinity to water, i.e. , low interfacial energies, to both ice and water. The former is to guarantee the adsorption of the IRI agent on the ice surface, and the latter is required for the IRI agent to spread sufficiently at the ice-water interface. Therefore, each IRI molecule can effectively block the diffusion of water onto the ice surface, and consequently inhibits the growth of ice. A spreading coefficient of IRI agents is therefore introduced to quantitatively assess the capability of IRI agents to spread at the ice-water interface.

Investigation of the freezing process of water droplets based on average and local initial ice fraction

ABSTRACTWe presented both experimental and numerical studies on the freezing of impacting water droplets on a cold surface at different surface temperatures. The numerical model consists of two parts. The first one is to determine the temperature evolution of the droplet prior to the occurrence of freezing by solving the heat conduction equation, and the second one is to simulate the freezing process via an extended phase change model. Experiments were conducted to observe and record the freezing process. The droplet profile and the propagation of moving water–ice interface during freezing were obtained from image analysis. Based on the numerical pre-recalescence temperature of the droplet, the average initial ice fraction and local initial ice fraction were obtained. Then, both the two kinds of initial ice fractions were used to figure out the difference that they brought to the predicted freezing process. Through a comparison of the experimental observations and the numerical predictions, the freezing process predicted by using local initial ice fraction showed a better agreement with the experiment than using average initial ice fraction.

Turbulent mixing and heat fluxes under lake ice: the role of seiche oscillations

Abstract. We performed a field study on mixing and vertical heat transport under the ice cover of an Arctic lake. Mixing intensities were estimated from small-scale oscillations of water temperature and turbulent kinetic energy dissipation rates derived from current velocity fluctuations. Well-developed turbulent conditions prevailed in the stably stratified interfacial layer separating the ice base from the warmer deep waters. The source of turbulent mixing was identified as whole-lake (barotropic) oscillations of the water body driven by strong wind events over the ice surface. We derive a scaling of ice–water heat flux based on dissipative Kolmogorov scales and successfully tested against measured dissipation rates and under-ice temperature gradients. The results discard the conventional assumption of nearly conductive heat transport within the stratified under-ice layer and suggest contribution of the basal heat flux into the melt of ice cover is higher than commonly assumed. Decline of the seasonal ice cover in the Arctic is currently gaining recognition as a major indicator of climate change. The heat transfer at the ice–water interface remains the least studied among the mechanisms governing the growth and melting of seasonal ice. The outcomes of the study find application in the heat budget of seasonal ice on inland and coastal waters.

Soil freezing process and different expressions for the soil-freezing characteristic curve

The soil-freezing characteristic curve (SFCC), which represents the relationship between unfrozen water content and sub-freezing temperature (or suction at ice-water interface) in a freezing soil, can be used for understanding the transportation of heat, water, and solute in frozen soils. In this paper, the soil freezing process and the similarity between the SFCC of saturated frozen soil and soil-water characteristic curve (SWCC) of unfrozen unsaturated soil are reviewed. Based on similar characteristics between SWCC and SFCC, a conceptual SFCC is drawn for illustrating the main features of soil freezing and thawing processes. Various SFCC expressions from the literature are summarized. Four widely used expressions ( i.e. , power relationship, exponential relationship, van Genuchten 1980 equation and Fredlund and Xing 1994 equation) are evaluated using published experimental data on four different soils ( i.e. , sandy loam, silt, clay, and saline silt). Results show that the exponential relationship and van Genuchten (1980) equation are more suitable for sandy soils. The simple power relationship can be used to reasonably best-fit the SFCC for soils with different particle sizes; however, it exhibits limitations when fitting the saline silt data. The Fredlund and Xing (1994) equation is suitable for fitting the SFCCs for all soils studied in this paper.