Ice Growth Research Articles

Spatio-temporal variability of small-scale leads based on helicopter maps of winter sea ice surface temperatures

Observations of sea ice surface temperature provide crucial information for studying Arctic climate, particularly during winter. We examined 1 m resolution surface temperature maps from 35 helicopter flights between October 2, 2019, and April 23, 2020, recorded during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). The seasonal cycle of the average surface temperature spanned from 265.6 K on October 2, 2019, to 231.8 K on January 28, 2020. The surface temperature was affected by atmospheric changes and varied across scales. Leads in sea ice (cracks of open water) were of particular interest because they allow greater heat exchange between ocean and atmosphere than thick, snow-covered ice. Leads were classified by a temperature threshold. The lead area fraction varied between 0% and 4% with higher variability on the local (5–10 km) than regional scale (20–40 km). On the regional scale, it remained stable at 0–1% until mid-January, increasing afterward to 4%. Variability in the lead area is caused by sea ice dynamics (opening and closing of leads), as well as thermodynamics with ice growth (lead closing). We identified lead orientation distributions, which varied between different flights but mostly showed one prominent orientation peak. The lead width distribution followed a power law with a negative exponent of 2.63, which is in the range of exponents identified in other studies, demonstrating the comparability to other data sets and extending the existing power law relationship to smaller scales down to 3 m. The appearance of many more narrow leads than wide leads is important, as narrow leads are not resolved by current thermal infrared satellite observations. Such small-scale lead statistics are essential for Arctic climate investigations because the ocean–atmosphere heat exchange does not scale linearly with lead width and is larger for narrower leads.

Extended Temperature Range of the Ice-Binding Protein Activity.

Ice-binding proteins (IBPs) are expressed in various organisms for several functions, such as protecting them from freezing and freeze injuries. Via adsorption on ice surfaces, IBPs depress ice growth and recrystallization and affect nucleation and ice shaping. IBPs have shown promise in mitigating ice growth under moderate supercooling conditions, but their functionality under cryogenic conditions has been less explored. In this study, we investigate the impact of two types of antifreeze proteins (AFPs): type III AFP from fish and a hyperactive AFP from an insect, the Tenebrio molitor AFP, in vitrified dimethylsulfoxide (DMSO) solutions. We report that these AFPs depress devitrification at -80 °C. Furthermore, in cases where devitrification does occur, AFPs depress ice recrystallization during the warming stage. The data directly demonstrate that AFPs are active at temperatures below the regime of homogeneous nucleation. This research paves the way for exploring AFPs as potential enhancers of cryopreservation techniques, minimizing ice-growth-related damage, and promoting advancements in this vital field.

Anti-freezing hydrogel regulated by ice-structuring proteins/cellulose nanofibers system as flexible sensor for winter sports

Conductive hydrogels are widely used as sensors in wearable devices. However, hydrogels cannot endure harsh low-temperature environments. Herein, a new regulatory system based on natural ice-structuring proteins (ISPs) and cellulose nanofibers (CNFs) is introduced into hydrogel network consisting of chemically crosslinked network of copolymerized acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and physically crosslinked polyvinyl alcohol chains, affording an anti-freezing hydrogel with high conductivity (2.63 S/m). These hydrogels show excellent adhesion behavior to various matrices (including aluminum, glass, pigskin, and plastic). Their mechanical properties are significantly improved with the increase in CNF content (tensile strength of 106.4 kPa, elastic modulus of 133.8 kPa). In addition, ISPs inhibit the growth of ice. This endows the hydrogels with anti-freezing property and allows them to maintain satisfactory mechanical properties, conductivity and sensing properties below zero degrees. Moreover, this hydrogel shows high sensitivity to tensile and compressive deformation (GF = 5.07 at 600–800 % strain). Therefore, it can be utilized to develop strain-type pressure sensors that can be attached directly to human skin for detecting various body motions accurately, reliably, and stably. This study proposes a simple strategy to improve the anti-freezing property of hydrogels, which provides new insights for developing flexible hydrogel electronic devices for application in winter sports.

Turbulence as a Key Driver of Ice Aggregation and Riming in Arctic Low‐Level Mixed‐Phase Clouds, Revealed by Long‐Term Cloud Radar Observations

AbstractTurbulence in clouds is known to enhance particle collision rates, as widely demonstrated for warm rain formation. A similar impact on ice growth processes is expected but a solid observational basis is missing. A statistical analysis of a 15‐month data set of cloud radar observations allows for the first time to quantify the impact of turbulence on ice aggregation and riming in Arctic low‐level mixed‐phase clouds. Increasing eddy dissipation rate (EDR), from below 10−4 to above 10−3 m2 s−3, yields larger ice aggregates, and higher particle concentration, likely caused by increasing fragmentation. In conditions more favorable to riming, higher EDR is associated with dramatically higher particle fall velocities (by up to 125%), under similar liquid water paths, indicative of markedly higher degrees of riming. Our findings thus reveal the key role of turbulence for cold precipitation formation, and highlight the need for an improved understanding of turbulence‐hydrometeor interactions in cold clouds.

Monitoring Aqueous Sucrose Solutions Using Droplet Microfluidics: Ice Nucleation, Growth, Glass Transition, and Melting.

Freezing and freeze-drying processes are commonly used to extend the shelf life of drug products and to ensure their safety and efficacy upon use. When designing a freezing process, it is beneficial to characterize multiple physicochemical properties of the formulation, such as nucleation rate, crystal growth rate, temperature and concentration of the maximally freeze-concentrated solution, and melting point. Differential scanning calorimetry has predominantly been used in this context but does have practical limitations and is unable to quantify the kinetics of crystal growth and nucleation. In this work, we introduce a microfluidic technique capable of quantifying the properties of interest and use it to investigate aqueous sucrose solutions of varying concentration. Three freeze-thaw cycles were performed on droplets with 75-μm diameters at cooling and warming rates of 1 °C/min. During each cycle, the visual appearance of the droplets was optically monitored as they experienced nucleation, crystal growth, formation of the maximally freeze-concentrated solution, and melting. Nucleation and crystal growth manifested as increases in droplet brightness during the cooling phase. Heating was associated with a further increase as the temperature associated with the maximally freeze-concentrated solution was approached. Heating beyond the melting point corresponded to a decrease in brightness. Comparison with the literature confirmed the accuracy of the new technique while offering new visual data on the maximally freeze-concentrated solution. Thus, the microfluidic technique presented here may serve as a complement to differential scanning calorimetry in the context of freezing and freeze-drying. In the future, it could be applied to a plethora of mixtures that undergo such processing, whether in pharmaceutics, food production, or beyond.

Interannual Variability of August Precipitation in China Associated With the Antarctic Sea Ice Anomaly

AbstractThrough observational analysis and atmospheric simulation experiments, the relationship between sea ice in the region of South Pole and August precipitation in China was determined. Results indicate that the leading mode of August precipitation in China is significantly correlated with July sea ice concentration (SIC) in South Pole, specifically in eastern Indian Ocean (EIO) region. Typically, the SIC growth is followed by positive rainfall anomalies in the middle and lower reaches of Yangtze River Basin (YRB) and Northeast China (NEC), while South China (SC) is under the control of negative rainfall anomalies. Precisely, owing to the temporal persistence of sea ice in the South Polar region from May to August, sea ice anomalies exert a strong influence on August atmospheric stability in EIO of Southern Hemisphere via regulating turbulent heat flux and air temperature anomalies. As SIC increases, the atmospheric circulation in horizontal exhibits the characteristics of the Antarctic Oscillation (AAO) positive phase, affecting the zonal wind anomalies. Subsequently, the anomalous circulation with a barotropic structure propagates to Australia and the East Asian via the strengthened vertical meridional cells and zonal winds. Moreover, numerical simulations confirm that due to the growth of South Polar sea ice in EIO, abnormal cyclone and anticyclone appear over North China and SC respectively, together with the moisture converging anomalies in the middle and lower reaches of YRB, and diverging anomalies in SC. Accordingly, these atmospheric circulation anomalies triggered by Antarctic sea ice conducive to a wet (dry) August in northern (southern) China.

Interfacial ice sprouting during salty water droplet freezing

Icing of seawater droplets is capable of causing catastrophic damage to vessels, buildings, and human life, yet it also holds great potential for enhancing applications such as droplet-based freeze desalination and anti-icing of sea sprays. While large-scale sea ice growth has been investigated for decades, the icing features of small salty droplets remain poorly understood. Here, we demonstrate that salty droplet icing is governed by salt rejection-accompanied ice crystal growth, resulting in freezing dynamics different from pure water. Aided by the observation of brine films emerging on top of frozen salty droplets, we propose a universal definition of freezing duration to quantify the icing rate of droplets having varying salt concentrations. Furthermore, we show that the morphology of frozen salty droplets is governed by ice crystals that sprout from the bottom of the brine film. These crystals grow until they pierce the free interface, which we term ice sprouting. We reveal that ice sprouting is controlled by condensation at the brine film free interface, a mechanism validated through molecular dynamics simulations. Our findings shed light on the distinct physics that govern salty droplet icing, knowledge that is essential for the development of related technologies.

Grain growth of ice doped with soluble impurities

Abstract. The grain size of polycrystalline ice affects key parameters related to the dynamics of ice masses, such as the rheological and dielectric properties of terrestrial ice as well as the ice shells of icy satellites. To investigate the effect of soluble impurities on the grain-growth kinetics of polycrystalline ice, we conducted annealing experiments on polycrystalline ice samples doped with different concentrations of KCl (10−2, 10−3, 10−4 and 10−5 mol L−1) or MgSO4 (10−2 and 10−5 mol L−1). Samples were annealed for a maximum of 100 h at a hydrostatic confining pressure of 20 MPa (corresponding to a depth of about 2 km) and different constant temperatures of 268, 263, 258 and 253 K (corresponding to −5, −10, −15 and −20 °C, respectively). After each experiment, images of a polished sample surface were obtained using an optical microscope equipped with a cold stage. With grain boundaries detected, grains were reconstructed from the images, and an average grain size was determined for each sample. Normal grain growth occurred in all samples. Grain-size data are interpreted using the following grain-growth model: dn-d0n=kt (d: grain size; d0: starting grain size; n: grain-growth exponent; k: growth constant; t: duration). Values of the best-fit grain-growth exponent, n, for all samples range from 2.6 to 6.2, with an average value of 4.7. Pure ice exhibits 3.1 ⩽n⩽ 4.6, with an average value of 3.8. Above the eutectic point, soluble impurities enhance grain growth, as a melt phase is formed, and it could provide a fast diffusion pathway. Below the eutectic point, soluble impurities impede grain growth probably via the formation of salt hydrates that could pin the grain boundaries. Close to the eutectic point, the grain growth of doped ice is similar to pure ice. Natural ice is impure, often containing air bubbles and soluble impurities, and is usually subjected to a hydrostatic pressure. Our data set will provide new insights into the evolution of grain size within and the dynamics of natural ice masses.

PERSPECTIVE: Targeted development and optimization of small-molecule ice recrystallization inhibitors (IRIs) for the cryopreservation of biological systems

Despite the routine use of cryopreservation for the storage of biological materials, its outcomes are often sub-optimal (including reduced post-thaw viability, recovery, and functionality) due to the damage caused by uncontrolled ice growth. Traditional cryoprotective agents (CPAs), including dimethyl sulfoxide (DMSO), fail to prevent damage caused by ice growth and concerns over CPA cytotoxicity have fostered an increased interest in developing improved CPAs and cryoprotection strategies. The inhibition of ice recrystallization by natural antifreeze (glyco)proteins [AF(G)Ps] to improve cryopreservation outcomes has been examined; however, the ice binding properties of these substances and their challenging large-scale production make them poor CPA candidates. Therefore, the development and deployment of biocompatible, small-molecule ice recrystallization inhibitors (IRIs) for use as CPAs is a worthwhile objective. Extensive structure-activity relationship studies on AF(G)Ps revealed that simple carbohydrate derivatives could inhibit ice recrystallization. It was later discovered that this activity could be fine-tuned by delicately balancing the molecule’s hydrophobicity and hydrophilicity. Current generation small-molecule IRIs have been meticulously designed to avoid binding to the surface of ice and subsequent biological testing (for both cytotoxicity and cryopreservation efficacy) has demonstrated significant improvements to the cryopreservation outcomes of several cell types. However, an individualized cell-specific approach for the simultaneous assessment of multiple cryopreservation outcomes is necessary to realize the full potential of IRIs as CPAs. This article provides a detailed overview of the development of small-molecule carbohydrate-based IRIs and highlights the crucial cell-specific biological considerations that must be taken into account when assessing cryopreservation outcomes.

Progressive stirred freeze concentration: Effect of operative parameters on vital statistics of beer

AbstractFreeze concentration (FC), a low‐cost alternative technology to separate and concentrate high‐value compounds, was applied to three distinct craft ale beer styles—Witbier, Bitter, and Porter—to investigate its impact on vital beer statistics. A central composite design with freezing temperature and ice fraction as factors was employed, with response surface analysis revealing significant effects on the average ice growth rate (), concentration index (CI), and average distribution coefficient () of ethanol, total solids, color, and bitterness in the liquid fraction. Results showed that ice fraction primarily influenced solute concentrations and increased with ice fraction due to water removal. Freezing temperature affected . The type of beer had a significant impact on color and bitterness, reflecting the specific style parameters. Furthermore, response optimization yielded conditions that significantly altered beer statistics, leading to changes in ethanol content, total solids, color, and bitterness, possibly classifying them as new beer styles. The study demonstrates the potential of FC to influence the beer characteristics and broaden the range of beer styles.Practical applicationsInnovations in science and technology, added to the search for new beer styles, promote the development of new products in the beer industry. In this article, a potential use of the freeze concentration technology was identified for the development of new concentrated beer products. The impact of progressive stirred freeze concentration in three craft beers was studied. First, obtaining a concentrated beer from this technique was possible, with a higher concentration of total solids and ethanol. In addition, the vital statistics of beer could be modified using freeze concentration to obtain novel concentrated beer products.

Temperature and salinity in the Bohai Sea landfast ice: Observations and modelling

Temperature and salinity are essential thermodynamic properties of sea ice. A 40-day long field campaign was carried out in winter 2020/2021 in the northern Bohai Sea in the landfast sea ice to investigate the seasonal sea ice temperature and salinity evolution. Ice thickness was measured routinely. A thermistor string was used to measure the ice temperature. Ice samples were collected for salinity by coring (Sco) and crumbing (Scr) methods. The mean vertical values of Sco and Scr were 4.8–5.8 psu and 8.3–13.8 psu, respectively. In cold ice, Sco and Scr were very close to each other. When ice temperature increased to −5 °C, Sco and Scr tended to differ from each other, and the difference was at largest at ice bottom. The brine volume fraction (BVF) ranged between 0.03 and 0.21 for Sco and 0.03 and 0.32 for Scr. The growth of ice reached a maximum of 3.7 cm/day in very cold conditions, while the average growth rate was 0.8 cm/day comparable to other seasonally ice-covered seas. A numerical sea ice thermodynamic model was applied to simulate the ice thickness with particular attention to the effect of Sco and Scr on the ice mass balance. The modeled overall ice growth rate was 0.7 cm/day and agreed well with the observations but during cold periods the simulation was biased down (1.1 cm/day); a possible reason is underestimation of the thermal conductivity in the model. The modeled ice thickness differed by 3 cm when using Sco and Scr as the input salinity profiles indicating that salinity has a minor impact on sea ice mass balance during mid-winter.

Characteristics of the presence and migration patterns of DOM between ice and water in the cold and arid Daihai Lake

Seasonal ice cover plays a crucial role in shaping the physical characteristics of lakes in cold and arid regions. Moreover, the ice significantly affects the level and quality of dissolved organic matter (DOM) in the water column. We utilized spectroscopy and mass spectrometry to analyze the molecular composition and distribution of DOM in ice cores and under-ice water in Daihai Lake. We identified the main environmental factors affecting DOM migration through structural equation modelling (SEM). The freezing process created a repulsive effect on DOM, with water samples demonstrating a greater DOM content than ice. The dominant part of the DOM in the ice cores was mainly comprised of protein-like materials (71.45 %), whereas water consisted of humus-like materials (54.81 %). The average molecular weight of the ice cover DOM (m/z = 396.77) was smaller than in the under-ice water (m/z = 405.42). While low-molecular and low-aromatic protein-like material tended to be trapped in the ice layer during ice formation, large-molecular and highly aromatic humic substances were more easily expelled into the water. Interestingly, condensed aromatic hydrocarbons were found to occur less frequently in the ice phase (11 %) compared to the aqueous phase (13 %). Both the lipid and protein/aliphatic compound structures exhibited slightly higher ratios in the ice (6 % and 8 %, respectively) than in water (1 % and 5 %, respectively). SEM between the ice cover environment and DOM indicated that the ice can influence the distribution pattern of DOM through the regulation of internal solute factors and other chemicals. The nature of the DOM and the rate of ice growth also play critical roles in determining the distribution mechanism of DOM for ice and water. The pollutant distribution characteristics and migration patterns between ice and water are essential for comprehending environmental water pollution and promoting pollution management and protection measures in cold region lakes.

Structure Discovery in Atomic Force Microscopy Imaging of Ice.

The interaction of water with surfaces is crucially important in a wide range of natural and technological settings. In particular, at low temperatures, unveiling the atomistic structure of adsorbed water clusters would provide valuable data for understanding the ice nucleation process. Using high-resolution atomic force microscopy (AFM) and scanning tunneling microscopy, several studies have demonstrated the presence of water pentamers, hexamers, and heptamers (and of their combinations) on a variety of metallic surfaces, as well as the initial stages of 2D ice growth on an insulating surface. However, in all of these cases, the observed structures were completely flat, providing a relatively straightforward path to interpretation. Here, we present high-resolution AFM measurements of several water clusters on Au(111) and Cu(111), whose understanding presents significant challenges due to both their highly 3D configuration and their large size. For each of them, we use a combination of machine learning, atomistic modeling with neural network potentials, and statistical sampling to propose an underlying atomic structure, finally comparing its AFM simulated images to the experimental ones. These results provide insights into the early phases of ice formation, which is a ubiquitous phenomenon ranging from biology to astrophysics.

Cloud-Top Phase Characterization of Extratropical Cyclones over the Northeast and Midwest United States: Results from IMPACTS

Abstract Cloud-top phase (CTP) impacts cloud albedo and pathways for ice particle nucleation, growth, and fallout within extratropical cyclones. This study uses airborne lidar, radar, and Rapid Refresh analysis data to characterize CTP within extratropical cyclones as a function of cloud-top temperature (CTT). During the 2020, 2022, and 2023 Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign deployments, the Earth Resources 2 (ER-2) aircraft flew 26 research flights over the northeast and midwest United States to sample the cloud tops of a variety of extratropical cyclones. A training dataset was developed to create probabilistic phase classifications based on Cloud Physics Lidar measurements of known ice and liquid clouds. These classifications were then used to quantify dominant CTP in the top 150 m of clouds sampled by the Cloud Physics Lidar in storms during IMPACTS. Case studies are presented illustrating examples of supercooled liquid water at cloud top at different CTT ranges (−3° < CTTs < −35°C) within extratropical cyclones. During IMPACTS, 19.2% of clouds had supercooled liquid water present at cloud top. Supercooled liquid was the dominant phase in extratropical cyclone cloud tops when CTTs were >−20°C. Liquid-bearing cloud tops were found at CTTs as cold as −37°C. Significance Statement Identifying supercooled liquid cloud tops’ frequency is crucial for understanding ice nucleation mechanisms at cloud top, cloud radiative effects, and aircraft icing. In this study, airborne lidar, radar, and model temperature data from 26 research flights during the NASA IMPACTS campaign are used to characterize extratropical cyclone cloud-top phase (CTP) as a function of cloud-top temperature (CTT). The results show that liquid was the dominant CTP present in extratropical cyclone cloud tops when CTTs were >−20°C with decreasing supercooled liquid cloud-top frequency at temperatures < −20°C. Nevertheless, liquid was present at CTTs as cold as −37°C.

Observing growth and interfacial dynamics of nanocrystalline ice in thin amorphous ice films

Ice crystals at low temperatures exhibit structural polymorphs including hexagonal ice, cubic ice, or a hetero-crystalline mixture of the two phases. Despite the significant implications of structure-dependent roles of ice, mechanisms behind the growths of each polymorph have been difficult to access quantitatively. Using in-situ cryo-electron microscopy and computational ice-dynamics simulations, we directly observe crystalline ice growth in an amorphous ice film of nanoscale thickness, which exhibits three-dimensional ice nucleation and subsequent two-dimensional ice growth. We reveal that nanoscale ice crystals exhibit polymorph-dependent growth kinetics, while hetero-crystalline ice exhibits anisotropic growth, with accelerated growth occurring at the prismatic planes. Fast-growing facets are associated with low-density interfaces that possess higher surface energy, driving tetrahedral ordering of interfacial H2O molecules and accelerating ice growth. These findings, based on nanoscale observations, improve our understanding on early stages of ice formation and mechanistic roles of the ice interface.

Bubbles dominated the significant spatiotemporal variability and accumulation of methane concentrations in an ice-covered reservoir

Climate-sensitive ice-covered reservoirs are critical components of methane (CH4) release. However, the mechanisms that influence CH4 dynamics during ice-covered periods remain poorly studied. To investigate the effects of bubbles on CH4 dynamics, we conducted intensive field and incubation experiments in an ice-covered reservoir (ice growth, stability, and melt period) in Northeast China. We found that the mean dissolved CH4 concentrations in the ice (625.9 ± 2419.7 nmol L−1) and underlying water (1218.9 ± 2678.9 nmol L−1) were high, making them atmosphere CH4 sources. The visible bubble bands (bubble area) in the riverine zone and the vertical profile of the CH4 concentration in the ice reflect the distribution of trapped bubbles. The mean CH4 concentration in the ice of the bubble area (1674.8 ± 3926.8 nmol L−1) was 2 orders of magnitude higher than that of no-bubble area (53.7 ± 9.2 nmol L−1). Moreover, a large amount of CH4 accumulated under the ice in the bubble area. These findings suggest that bubbles determine the CH4 storage in ice and CH4 accumulation in the underlying water. Ice growth increases CH4 storage in ice and the underlying water because of the entrapment and re-dissolution of CH4 bubbles. However, ice melting releases the CH4 accumulated in the ice and underlying water. A comparison of the field and incubation experiments indicated that the deep-water environment of the reservoir had a CH4 burial effect. Stepwise regression analysis revealed that higher sediment organic matter content, median particle size, and porosity increased the production and release of CH4 bubbles, trapping more CH4 bubbles in ice. Overall, this study improves the mechanistic understanding of CH4 dynamics and predictability of CH4 emissions during ice-covered periods.

Two new multirotor uncrewed aerial vehicles (UAVs) for glaciogenic cloud seeding and aerosol measurements within the CLOUDLAB project

Abstract. Uncrewed aerial vehicles (UAVs) have become widely used in a range of atmospheric science research applications. Because of their small size, flexible range of motion, adaptability, and low cost, multirotor UAVs are especially well-suited for probing the lower atmosphere. However, their use so far has been limited to conditions outside of clouds, first because of the difficulty of flying beyond visual line of sight and second because of the challenge of flying in icing conditions in supercooled clouds. Here, we present two UAVs for cloud microphysical research: one UAV (the measurement UAV) equipped with a Portable Optical Particle Spectrometer (POPS) and meteorological sensors to probe the aerosol and meteorological properties in the boundary layer and one UAV (the seeding UAV) equipped with seeding flares to produce a plume of particles that can nucleate ice in supercooled clouds. A propeller heating mechanism on both UAVs allows for operating in supercooled clouds with icing conditions. These UAVs are an integral part of the CLOUDLAB project in which glaciogenic cloud seeding of supercooled low stratus clouds is utilized for studying aerosol–cloud interactions and ice crystal formation and growth. In this paper, we first show validations of the POPS on board the measurement UAV, demonstrating that the rotor turbulence has a small effect on measured particle number concentrations. We then exemplify the applicability for profiling the planetary boundary layer, as well as for sampling and characterizing aerosol plumes, in this case, the seeding plume. We also present a new method for filtering out high-concentration data to ensure good data quality of POPS. We explain the different flight patterns that are possible for both UAVs, namely horizontal or vertical leg patterns or hovering, with an extensive and flexible parameter space for designing the flight patterns according to our scientific goals. Finally, we show two examples of seeding experiments: first characterizing an out-of-cloud seeding plume with the measurement UAV flying horizontal transects through the plume and, second, characterizing an in-cloud seeding plume with downstream measurements from a POPS and a holographic imager mounted on a tethered balloon. Particle number concentrations and particle number size distributions of the seeding plume from the experiments reveal that we can successfully produce and measure the seeding plume, both in-cloud (with accompanying elevated ice crystal number concentrations) and out-of-cloud. The methods presented here will be useful for probing the lower atmosphere, for characterizing aerosol plumes, and for deepening our cloud microphysical understanding through cloud seeding experiments, all of which have the potential to benefit the atmospheric science community.

Elevated fucose content enhances the cryoprotective performance of anionic polysaccharides

Biological cryopreservation often involves using a cryoprotective agent (CPA) to mitigate lethal physical stressors cells endure during freezing and thawing, but effective CPA concentrations are cytotoxic. Hence, natural polysaccharides have been studied as biocompatible alternatives. Here, a subset of 26 natural polysaccharides of various chemical composition was probed for their potential in enhancing the metabolic post-thaw viability (PTV) of cryopreserved Vero cells. The best performing cryoprotective polysaccharides contained significant fucose amounts, resulting in average PTV 2.8-fold (up to 3.1-fold) compared to 0.8-fold and 2.2-fold for all non-cryoprotective and cryoprotective polysaccharides, respectively, outperforming the optimized commercial CryoStor™ CS5 formulation (2.6-fold). Stoichiometrically, a balance between fucose (18–35.7 mol%), uronic acids (UA) (13.5–26 mol%) and high molecular weight (MW > 1 MDa) generated optimal PTV. Principal component analysis (PCA) revealed that fucose enhances cell survival by a charge-independent, MW-scaling mechanism (PC1), drastically different from the charge-dominated ice growth disruption of UA (PC2). Its neutral nature and unique properties distinguishable from other neutral monomers suggest fucose may play a passive role in conformational adaptability of polysaccharide to ice growth inhibition, or an active role in cell membrane stabilization through binding. Ultimately, fucose-rich anionic polysaccharides may indulge in polymer-ice and polymer-cell interactions that actively disrupt ice and minimize lethal volumetric fluctuations due to a balanced hydrophobic-hydrophilic character. Our research showed the critical role neutral fucose plays in enhancing cellular cryopreservation outcomes, disputing previous assumptions of polyanionicity being the sole governing predictor of cryoprotection.

Snow effects on brash ice and level ice growth

Abstract Brash ice formation and accumulation occur at a faster rate in ship channels, harbours and turning areas compared to the surrounding level ice. Accurate prediction of brash ice thickness plays an important role in addressing operational challenges and optimisation of ice management strategies. This study enhances existing brash ice growth models by considering the effects of snow and accounting for brash ice expulsion towards the sides of ship channels at each passage. To validate the influence of these critical factors on brash ice thickness, three distinct ship channels located in the Bay of Bothnia, Luleå, Sweden, were investigated. For two test channels formed for study purposes, the slower growth rate of brash ice caused by snow insulation was more prominent than the brash ice growth acceleration caused by the snow–slush–snow ice transformation. In the third channel characterised by frequent navigation, the transformation of slush into snow ice played a more substantial role than snow insulation. In both test channels, the brash ice growth model performed optimally, assuming a 10% expulsion of brash ice sideways at each vessel passage. In the third, wider and more frequently navigated channel, a 1.2% brash ice expelling coefficient predicted well the measured brash ice thicknesses.

Characterizing Ice Nucleating Particles Over the Southern Ocean Using Simultaneous Aircraft and Ship Observations

AbstractSupercooled liquid clouds are ubiquitous over the Southern Ocean (SO), even to temperatures below −20°C, and comprise a large fraction of the marine boundary layer (MBL) clouds. Earth system models and reanalysis products have struggled to reproduce the observed cloud phase distribution and occurrence of cloud ice in the region. Recent simulations found the microphysical representation of ice nucleation and growth has a large impact on these properties, however, measurements of SO ice nucleating particles (INPs) to validate simulations are sparse. This study presents measurements of INPs from simultaneous aircraft and ship campaigns conducted over the SO in austral summer 2018, which include the first in situ observations in and above cloud in the region. Our results confirm recent observations that INP concentrations are uniformly lower than measurements made in the late 1960s. While INP concentrations below and above cloud are similar, higher ice nucleation efficiency above cloud supports model simulations that the dominant INP composition varies with height. Model parameterizations based solely on aerosol properties capture the mean relationship between INP concentration and temperature but not the observed variability, which is likely related to the only modest correlations observed between INPs and environmental or aerosol metrics. Including wind speed in addition to activation temperature in a marine INP parameterization reduces bias but does not explain the large range of observed INP concentrations. Direct and indirect inference of marine INP size suggests MBL INPs, at least during Austral summer, are dominated by particles with diameters smaller than 500 nm.