Free Surface Of Ice Research Articles

A theoretical model of excess attenuation of acoustic signals propagating under cracked sea-ice landscapes.

The Arctic sheet is transitioning from a continuous cover of thick multi-year ice to a fragmented landscape of thin young ice. If the type of acoustic transmission allows repetitive interaction of rays with the sea surface, in the fragmented scenario acoustic rays will undergo a random sequence of reflections from water or sea-ice interfaces. Calm sea conditions in the water channels between the ice floes (leads) and the smooth, flat surface of the young ice bottom reduce scattering due to interface roughness, resulting only in scattering due to inhomogeneity in surface reflectivity. Using an idealized framework, this study investigates the extent to which the mid- to high-frequency underwater acoustic propagation is altered due to repetitive interactions of acoustic signals with a sea surface consisting of a random distribution of ice sheets and leads. An expression for the coherent field (the acoustic field averaged over an ensemble of realizations of sea-ice distributions) was derived from theory. Any deviation from a homogeneous surface condition (either by randomly adding ice slabs in a free ice surface or by including leads in a fully ice-covered sea surface) leads to an excess attenuation of the coherent field. Results are validated by numerical simulations.

A meshfree approach to non-Newtonian free surface ice flow: Application to the Haut Glacier d'Arolla

Numerical models of glacier and ice sheet dynamics traditionally employ finite difference or finite element methods. Although these are highly developed and mature methods, they suffer from some drawbacks, such as inability to handle complex geometries (finite differences) or a costly assembly procedure for nonlinear problems (finite elements). Additionally, they are mesh-based, and therefore moving domains become a challenge. In this paper, we introduce a novel meshfree approach based on a radial basis function (RBF) method. The meshfree nature of RBF methods enables efficient handling of moving margins and free ice surface. RBF methods are also accurate, easy to implement, and allow for reduction the computational cost associated with the linear system assembly, since stated in strong form. To demonstrate the global RBF method we model the velocity field of ice flow in the Haut Glacier d'Arolla, which is governed by the nonlinear Stokes equations. We test the method for different basal conditions and for a free moving surface. We also compare the global RBF method with its localized counterpart—the RBF partition of unity method (RBF-PUM)—that allows for a significant gain in the computational efficiency. Both RBF methods are compared with the classical finite element method in terms of accuracy and efficiency. We find that the RBF methods are more efficient than the finite element method and well suited for ice dynamics modeling, especially the partition of unity approach.

The thickness of a liquid layer on the free surface of ice as obtained from computer simulation

Molecular dynamic simulations were performed for ice I(h) with a free surface by using four water models, SPC/E, TIP4P, TIP4P/Ice, and TIP4P/2005. The behavior of the basal plane, the primary prismatic plane, and of the secondary prismatic plane when exposed to vacuum was analyzed. We observe the formation of a thin liquid layer at the ice surface at temperatures below the melting point for all models and the three planes considered. For a given plane it was found that the thickness of a liquid layer was similar for different water models, when the comparison is made at the same undercooling with respect to the melting point of the model. The liquid layer thickness is found to increase with temperature. For a fixed temperature it was found that the thickness of the liquid layer decreases in the following order: the basal plane, the primary prismatic plane, and the secondary prismatic plane. For the TIP4P/Ice model, a model reproducing the experimental value of the melting temperature of ice, the first clear indication of the formation of a liquid layer, appears at about -100 degrees C for the basal plane, at about -80 degrees C for the primary prismatic plane, and at about -70 degrees C for the secondary prismatic plane.

Proton ordering in ice at an ice-metal interface

The structure of the proton sublattice of ice at an ice-metal interface is analyzed by solving the Ginzburg-Landau equation for an order parameter describing the proton ordering under an appropriate boundary condition [1, 2]. When the interaction between protons and the substrate is weak, the ice rules that govern proton order are weaker at the interface as compared to bulk ice, but to a lesser extent than at the free ice surface. In the case of strong proton-substrate interaction (clean interface and/or high conductivity of the substrate), the ice rules are stronger at the interface as compared to bulk ice, which corresponds to a more ordered proton sublattice. The latter case corresponds to a lower concentration of defects in the proton sublattice, which determine important properties of ice, such as adhesion, electrical conductivity, plasticity, and electric field distribution near the interface. A qualitative correlation is described between electrical properties of the substrate and mechanical properties of the interface, including adhesion and friction.

The improvement of heat transfer efficiencies in cool‐thermal discharge systems with complete removal of melt

AbstractA new device of air time–velocity variations in cool‐thermal discharge systems from ice melting with complete melt removal was proposed and the mathematical formulation for calculating the outlet chilled air temperature with convective transfer by adjusting the air mass velocity on free ice surface was developed. The proposed device in this study is a technical feasibility in controlling the outlet chilled air temperature by adjusting the air mass velocity and enhancing heat transfer efficiency by removing melt with a maximum temperature gradient. Three numerical examples of the inlet ambient air temperature were illustrated for practical applications under complete melt removal, and hence the time history of the air mass velocity was also obtained for the desired outlet chilled air temperature. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(6): 524–532, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj/10119

A hydrophobic self-assembled monolayer with improved adhesion to aluminum for deicing application

A previously developed laser-generated stress wave procedure for measuring the tensile strength of ice/solid interfaces was used to study the effectiveness of a self-assembled monolayer of dimethyl- n-octadecilcholorsilane (DMOCS) in providing a hydrophobic surface to a 6061 Al alloy. In this experiment, a laser-induced compressive stress wave travels through a substrate disc that has a layer of ice grown on its front surface. The compressive stress pulse reflects into a tensile wave from the free surface of ice and pulls the ice/Al interface apart at a sufficiently high amplitude. The interface strength was calculated using a wave mechanics simulation, with the interferometrically recorded free surface velocity of a bare Al substrate (measured under identical ice spallation conditions) as an input. The tensile strength of the ice/DMOCS interface at −10°C was found to be 131 MPa, which is the lowest among all surfaces tested to date, which include, as-received Al surfaces (274 MPa), surfaces prepared with chemical and mechanical polishing (181 MPa), and PMMA-coated (190 MPa) and polyimide-coated (177 MPa) Al surfaces. The two methyl groups attached to the outer end of the carbon chain in the DMOCS coating provide a completely hydrophobic surface, while its silane group at the bottom most end reacts with the adsorbed hydroxyl groups on the aluminum surface to form a strong Si to Al covalent bond. Thus, DMOCS coatings present an appealing alternative to various presently available ice mitigating surface strategies, by providing a longer-lasting surface with the highest hydrophobicity possible.

Detailed observations of the rippled surface of Antarctic blue-ice areas

AbstractThis paper presents detailed observations of the regularly rippled surface on an Antarctic blue-ice area near Svea, at five sites. The wavelength of the ripples was found to be 20–24 cm, while the wave height (crest–trough) was 1–2 cm. The ripple crests are generally oriented perpendicular to the direction of the strongest winds. Repeated measurements show that wave heights increase throughout the summer, with most ablation occurring in the wave troughs. This implies that traditional methods of measuring ablation (such as stakes when a rod on the ice surface is used to define a mean surface height) tend to underestimate total ablation because they sample only crests. One site exhibited significant migration of the surface ripples of about 2 cm month−1 in the downwind direction, whereas three other sites showed no significant wave movement. The formation and the specific characteristics of the surface ripples are most likely caused by self-amplifying interaction mechanisms between the free ice surface and the overlying turbulent atmosphere, which necessarily involve spatial variations in sublimation. A simple model was used to quantify the interaction between the surface ripples, the airflow aloft and the sublimation rate. The model is able to predict wavelengths and migration rates that are in reasonable agreement with the observations.

Cylindrical Flow in and Over Channels of Irregular Shape

AbstractEarlier work by Nye (1965), who obtained numerical solutions for axial independent flow of a non-linear Glen material in channels of rectangular, elliptic, and parabolic cross-sections with a null-slip basal condition, is extended by using an inverse technique. Exact analytical solutions are obtained for flow in irregular-shaped channels (subject to symmetry restrictions) for both a Newtonian and an n = 3 Glen material. The cross-sections are regulated by multi-parameters. Solutions are obtained for two types of channel: (a) those whose side walls meet the free ice surface vertically, and (b) periodic channel arrays whose basal profiles do not intersect the free ice surface, i.e. overfilled channels. Solutions for the second type have not been presented previously. The solutions for then= 3 Glen material employ a small parameter which limits the geometry variation to perturbations on semicircular or uniform-depth channels. Basal slip conditions can be incorporated although results are not presented here.

Cylindrical Flow in and Over Channels of Irregular Shape

AbstractEarlier work by Nye (1965), who obtained numerical solutions for axial independent flow of a non-linear Glen material in channels of rectangular, elliptic, and parabolic cross-sections with a null-slip basal condition, is extended by using an inverse technique. Exact analytical solutions are obtained for flow in irregular-shaped channels (subject to symmetry restrictions) for both a Newtonian and an n = 3 Glen material. The cross-sections are regulated by multi-parameters. Solutions are obtained for two types of channel: (a) those whose side walls meet the free ice surface vertically, and (b) periodic channel arrays whose basal profiles do not intersect the free ice surface, i.e. overfilled channels. Solutions for the second type have not been presented previously. The solutions for the n = 3 Glen material employ a small parameter which limits the geometry variation to perturbations on semicircular or uniform-depth channels. Basal slip conditions can be incorporated although results are not presented here.