Brinicles as a Case of Inverse Chemical Gardens

Geochimica et Cosmochimica Acta, 1990

Several mechanisms (evaporation, water-rock interaction, ultra-filtration) have been suggested to explain the evolution of ubiquito~ C&chloride subsurface brines.

The Cryosphere Discussions, 2019

The microstructure of polycrystalline ice with a threading solution of brine controls its numerous characteristics, including the ice mechanical properties, ice-atmosphere interactions, sea-ice albedo, and (photo)chemical behavior in/on the ice. Ice samples were previously prepared in laboratories to study various facets of ice-impurities interactions and (photo)reactions to model natural ice-impurities behavior. We examine the impact of the freezing conditions and solute (CsCl used as a proxy for naturally occurring salts) concentrations on the microscopic structure of ice samples via an environmental scanning electron microscope. The method allows us to observe in detail the ice surfaces, namely, the free ice, brine puddles, brine-containing grain boundary grooves, individual ice crystals, and imprints left by entrapped air bubbles at temperatures higher than-25°C. The amount of brine on the external surface is found proportional to the solute concentration and is strongly dependent on the sample preparation method. Time-lapse images in the condition of slight sublimation reveal sub-surface association of air bubbles with brine. With rising temperature (up to-14 °C), the brine surface coverage increases to remain enhanced during the subsequent cooling and until the final crystallization below the eutectic temperature. The ice recrystallization dynamics identifies the role of surface spikes in retarding the ice boundaries propagation (Zeener pining). The findings thus quantify the amounts of brine exposed to incoming radiation, available for the gas exchange, and influencing other mechanical and optical properties of ice. The results have straightforward implications for artificially prepared and naturally occurring salty ices.

Physical Review Fluids

Journal of Fluid Mechanics, 1980

Plate 1 FIGURE 3. A salinity gradicnt heated from the side, through a central metal cylinder. Depth of water 26 em; specific gravity a t bottom 1.044 and a t top 1-017; T, = 21.5 "C, T, = 31.9 "C. Photograph taken 74 minutes after heating was begun. Note the downward tilt of thc layers as they extend away from the wall. FIGURE 5. A salinity gradient cooled from the side, through a central metal cylinder. Depth of water 26.5 cm; specific gravity a t bottom 1.027 and a t top 1.000; T, = 21.4 "C, nominal temperature of inner cylinder 0 "C. Photograph taken 8 minutes after brine and ice mixture was added to the central cylinder. Note the upward tilt of the layers as they extend outwards, and the slow downward transport of dye from an originally horizontal layer of dye put into the tank during filling.

Solar Energy

The basis of a novel method for passive solar water heating homologous to the thermosiphon but driven by induced salinity, which causes a fluid to circulate without the need for a mechanical pump and with inverse natural convection (downward heat transfer), is outlined. The brinesiphon, like the thermosiphon, operates by harnessing the tendency of a less dense fluid to rise above a denser fluid, resulting in fluid motion through a collector, but with two exceptions: first, the buoyancy is controlled by induced salinity gradients rather than thermal gradients, and second, as a result, natural convection is in the opposite direction than that in the homologous thermosiphon concept; i.e., hot fluid flows down, and cold fluid rises. A brinesyphon may be more suitable for solar domestic water heating systems than the thermosiphon because the direction of flow allows downward transfer from a solar collector to a lower storage tank without any type of mechanical pumping system.

Journal of Fluid Mechanics, 1974

In an experimental and theoretical study, we model a phenomenon observed in the summer Arctic, where a fresh-water layer at a temperature of 0°C floats both over a sea-water layer at its freezing point and under an ice layer. Our results show that the ice growth in this system takes place in three phases. First, because the fresh-water density decreases upon supercooling, the rapid diffusion of heat relative to salt from the fresh to the salt water causes a density inversion and thereby generates a high Rayleigh number convection in the fresh water. In this convection, supercooled water rises to the ice layer, where it nucleates into thin vertical interlocking ice crystals. When these sheets grow down to the interface, supercooling ceases. Second, the presence of the vertical ice sheets both constrains the temperature T and salinity s to lie on the freezing curve and allows them to diffuse in the vertical. In the interfacial region, the combination of these processes generates a lat...

The Journal of Physical Chemistry C, 2018

According to the classical Archimedes' principle ice floats in water and has a fraction of its volume above the water surface. However, for very small ice particles, other competing forces such as van der Waals forces due to fluctuating charge distributions and ionic forces due to salt ions and charge on the ice surface also contribute to the force balance. The latter crucially depend on both the pH of the water and the salt concentration. The role of these forces in governing the initial stages of ice condensation has never been considered. Here we show that small ice particles can only form below an exclusion zone, from 2 nm (in high salt concentrations) up to 1 µm (in pure water at pH 7) thick, under the water surface. This distance is defined by an equilibrium of upwards buoyancy forces and repulsive van der Waals forces. Ionic forces due to salt and ice surface charge push this zone further down. Only after growing to a radius larger than 10 µm will the ice particles eventually float towards the water surface in agreement with the simple intuition based on Archimedes' principle. Our result is the first prediction of observable repulsive van der Waals forces between ice particles and the water surface outside a laboratory setting. We posit that it has consequences on the biology of ice water as we predict an exclusion zone free of ice particles near the water surface which is sufficient to support the presence of bacteria.

Europhysics Letters (EPL), 1992

The common observation of cellular substructure ((1 + at the seaice-ocean interface is explained by modelling the natural solidification of seawater as that of a dilute H20-NaCl solution. Linear and nonlinear perturbation theories reveal that the onedimensional planar steady state is morphologically unstable, and a bifurcation to cells occurs in geophysically relevant growth regimes. We compute the range of solidification velocity V, < V < V, in which the system is unstable for fxed far-field solute concentration C, , and bound the geophysical observations. The system exhibits weak wavelength selection near V, and the nonlinear theory shows that the bifurcation to cells is subcritical.

We analyze the early phase of brine entrapment in sea ice, using a phase field model. This model for a first-order phase transition couples non-conserved order parameter kinetics to salt diffusion. The evolution equations are derived from a Landau-Ginzburg order parameter gradient dynamics together with salinity conservation. The numerical solution of model equations by an exponential time differencing scheme describes the time evolution of phase separation between liquid water with high salinity and the ice phase with low salinity. The numerical solution in one and two dimensions indicates the formation of one dominant wavelength which sets the length scale of short-time frozen structures. A stability analysis provides the phase diagram in terms of two Landau parameters. It is distinguished an uniform ice phase, a homogeneous liquid saline water solution and a phase where solidification structures can be formed. The Landau parameters are extracted from the supercooling and superhea...

Journal of Geophysical Research: Oceans, 2019

Sea ice in part controls surface water properties and the ocean-atmosphere exchange of greenhouse gases at high latitudes. In sea ice, gas exists dissolved in brine and as air bubbles contained in liquid brine inclusions or as bubbles trapped directly within the ice matrix. Current research on gas dynamics within the ocean-sea ice-atmosphere interface has been based on the premise that brine with dissolved air becomes supersaturated with respect to the atmosphere during ice growth. Based on Henry's law, gas bubbles within brine should grow when brine reaches saturation during cooling, given that the total partial pressure of atmospheric gases is above the implicit pressure in brine of 1 atm. Using high-resolution light microscopy time series imagery of gas bubble evolution inside discrete brine pockets, we observed bubbles shrinking during cooling events in response to the development of freezing pressure above 3 atm. During warming of discrete brine pockets, existing bubbles expand and new bubbles nucleate in response to depressurization. Pressure variation within these inclusions has direct impacts on aqueous-gaseous equilibrium, indicating that Henry's law at a constant pressure of 1 atm is inadequate to assess the partitioning between dissolved and gaseous fractions of gas in sea ice. This new evidence of pressure build-up in discrete brine inclusions controlling the solubility of gas and nucleation of bubbles in these inclusions has the potential to affect the transport pathways of air bubbles and dissolved gases within sea ice-ocean-atmosphere interface and modifies brine biochemical properties. Plain Language Summary Sea ice plays an important role in controlling surface water properties and the ocean-atmosphere exchange of greenhouse gases at high latitudes. Within sea ice, gas exists dissolved in brine and as air bubbles contained in liquid brine inclusions. The amount of gas dissolved in brine as well as the amount of gas contained in air bubbles depends of the aqueous-gaseous equilibrium described by the Henry's law. Until now, it is assumed that the pressure in sea ice brine inclusions is 1 atm (standard pressure condition). Our work reveals visual evidence of variation of pressure within discrete brine pockets. These pressure regimes modify the aqueous-gaseous equilibrium and induce bubbles to shrink during cooling and enlarge or nucleate during warming. This new evidence of pressure build-up in discrete brine controlling the solubility of gas has the potential to affect the transport pathways of air bubbles and dissolved gases between ocean and atmosphere in the presence of sea ice and to modify brine biochemical properties.

Desalination, 2020

Publisher: Elsevier NOTICE: this is the author's version of a work that was accepted for publication in Desalination. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Desalination, 496:1 (2020)

Annals of Glaciology, 2001

It is well established that during sea-ice formation, crystals aggregate into a solid matrix, and dissolved sea-water constituents, including inorganic nutrients, are rejected from the ice matrix. However, the behaviour of dissolved organic matter (DOM) during ice formation and growth has not been studied to date. DOM is the primary energetic substrate for microbial heterotrophic activity in sea water and sea ice, and therefore it is at the base of the trophic fluxes within the microbial food web. The aim of our study was to compare the behaviour of DOM and inorganic nutrients during formation and growth of sea ice. Experiments were conducted in a large indoor ice-tank facility (Hamburg Ship Model Basin, Germany) at^15³C. Three 1m 3 tanks, to which synthetic sea water, nutrients and dissolved organic compounds (diatom-extracted DOM) had been added, were sampled over a period of 5 days during sea-ice formation. Samples were collected throughout the experiment from water underlying the ice, and at the end from the ice as well. Brine was obtained from the ice by centrifuging ice cores. Inorganic nutrients (nitrate and phosphate) were substantially enriched in brine in comparison to water and ice phases, consistent with the processes of ice formation and brine rejection. Dissolved organic carbon (DOC) was also enriched in brine but was more variable and enriched in comparison to a dilution line. No difference in bacteria numbers was observed between water, ice and brine. No bacteria growth was measured, and this therefore had no influence on the measurable DOC levels. We conclude that the incorporation of dissolved organic compounds in newly forming ice is conservative. However, since the proportions of DOC in the brine were partially higher than those of the inorganic nutrients, concentrating effects of DOC in brine might be different compared to salts.

The Cryosphere Discussions, 2017

The brine network in sea ice is a complex labyrinth whose precise microstructure is critical in governing the movement of brine and gas between the ocean and the sea ice surface. Recent advances in three-dimensional imaging using x-ray micro-computed tomography have enabled the visualization and quantification of the brine network morphology and variability. Using imaging of first-year sea ice samples at in-situ temperatures, we create a new mathematical network model to characterize the topology and connectivity of the brine channels. This model provides a statistical framework where we can characterize the pore networks via two parameters, depth and temperature, for use in dynamical sea ice models. Our approach advances the quantification of brine connectivity in sea ice, which can help investigations of bulk physical properties, such as fluid permeability, that are key in both global and regional sea ice models.

Journal of Colloid and Interface Science, 1989

Ice was grown on a microporous filter to elucidate the mechanism of ice segregation. The nuclepore filter is a thin plastic membrane (6 #m thick) with numerous micropores of uniform size. When the temperature of the ice on the filter and the water under the filter was lowered to slightly below 0°C, water was drawn through the filter toward the freezing front, where an ice column grew upward. The growth rate of the ice column was proportional to the degree of supercooling at the freezing front, which was determined by the surrounding heat conduction process. When the temperature was lowered further to a certain degree, the supercooled water under the filter began freezing and thus the ice column stopped growing. This degree, called the critical degree of supercooling, increases with decreasing size of the micropores. Supercooling of the water under the filter was caused by the existence of the micropores, which also allowed the migration of water to the freezing front. As a result, ice segregation occurred.