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Sample records for ice nucleation-active bacteria

  1. Application of Ice Nucleation - Active Bacteria to Food

    NASA Astrophysics Data System (ADS)

    Arai, Soichi; Watanabe, Michiko

    Ice nucleation-active bacteria act as nuclei and are able to freeze water without supercooling to a great degree. They are known as a major cause of the frost damage to crops. We have been trying with success to positively apply these bacteria to freeze texturing of food materials, freeze concentration of fresh liquid foods, formation of new physical properties of foods by freezing, and so forth. The most useful species for these applications is Xanthomonas campestris which has recently been designated as a food additive by the Japan Ministry of Health and Welfare and produced on an industrial scale. This paper reviews these topics, with some practical examples quoted primarily from our studies.

  2. Urediospores of rust fungi are ice nucleation active at > -10 °C and harbor ice nucleation active bacteria

    NASA Astrophysics Data System (ADS)

    Morris, C. E.; Sands, D. C.; Glaux, C.; Samsatly, J.; Asaad, S.; Moukahel, A. R.; Gonçalves, F. L. T.; Bigg, E. K.

    2013-04-01

    Various features of the biology of the rust fungi and of the epidemiology of the plant diseases they cause illustrate the important role of rainfall in their life history. Based on this insight we have characterized the ice nucleation activity (INA) of the aerially disseminated spores (urediospores) of this group of fungi. Urediospores of this obligate plant parasite were collected from natural infections of 7 species of weeds in France, from coffee in Brazil and from field and greenhouse-grown wheat in France, the USA, Turkey and Syria. Immersion freezing was used to determine freezing onset temperatures and the abundance of ice nuclei in suspensions of washed spores. Microbiological analyses of spores from France, the USA and Brazil, and subsequent tests of the ice nucleation activity of the bacteria associated with spores were deployed to quantify the contribution of bacteria to the ice nucleation activity of the spores. All samples of spores were ice nucleation active, having freezing onset temperatures as high as -4 °C. Spores in most of the samples carried cells of ice nucleation-active strains of the bacterium Pseudomonas syringae (at rates of less than 1 bacterial cell per 100 urediospores), but bacterial INA accounted for only a small fraction of the INA observed in spore suspensions. Changes in the INA of spore suspensions after treatment with lysozyme suggest that the INA of urediospores involves a polysaccharide. Based on data from the literature, we have estimated the concentrations of urediospores in air at cloud height and in rainfall. These quantities are very similar to those reported for other biological ice nucleators in these same substrates. However, at cloud level convective activity leads to widely varying concentrations of particles of surface origin, so that mean concentrations can underestimate their possible effects on clouds. We propose that spatial and temporal concentrations of biological ice nucleators active at temperatures > -10

  3. Ice nucleation active bacteria in precipitation are genetically diverse and nucleate ice by employing different mechanisms.

    PubMed

    Failor, K C; Schmale, D G; Vinatzer, B A; Monteil, C L

    2017-07-28

    A growing body of circumstantial evidence suggests that ice nucleation active (Ice(+)) bacteria contribute to the initiation of precipitation by heterologous freezing of super-cooled water in clouds. However, little is known about the concentration of Ice(+) bacteria in precipitation, their genetic and phenotypic diversity, and their relationship to air mass trajectories and precipitation chemistry. In this study, 23 precipitation events were collected over 15 months in Virginia, USA. Air mass trajectories and water chemistry were determined and 33 134 isolates were screened for ice nucleation activity (INA) at -8 °C. Of 1144 isolates that tested positive during initial screening, 593 had confirmed INA at -8 °C in repeated tests. Concentrations of Ice(+) strains in precipitation were found to range from 0 to 13 219 colony forming units per liter, with a mean of 384±147. Most Ice(+) bacteria were identified as members of known and unknown Ice(+) species in the Pseudomonadaceae, Enterobacteriaceae and Xanthomonadaceae families, which nucleate ice employing the well-characterized membrane-bound INA protein. Two Ice(+) strains, however, were identified as Lysinibacillus, a Gram-positive genus not previously known to include Ice(+) bacteria. INA of the Lysinibacillus strains is due to a nanometer-sized molecule that is heat resistant, lysozyme and proteinase resistant, and secreted. Ice(+) bacteria and the INA mechanisms they employ are thus more diverse than expected. We discuss to what extent the concentration of culturable Ice(+) bacteria in precipitation and the identification of a new heat-resistant biological INA mechanism support a role for Ice(+) bacteria in the initiation of precipitation.The ISME Journal advance online publication, 28 July 2017; doi:10.1038/ismej.2017.124.

  4. Urediospores of Puccinia spp. and other rusts are warm-temperature ice nucleators and harbor ice nucleation active bacteria

    NASA Astrophysics Data System (ADS)

    Morris, C. E.; Sands, D. C.; Glaux, C.; Samsatly, J.; Asaad, S.; Moukahel, A. R.; Gonçalves, F. L. T.; Bigg, E. K.

    2012-10-01

    In light of various features of the biology of the rust fungi and of the epidemiology of the plant diseases they cause that illustrate the important role of rainfall in their life history, we have characterized the ice nucleation activity (INA) of the aerially disseminated spores (urediospores) of this group of fungi. Urediospores of this obligate plant parasite were collected from natural infections from 7 species of weeds in France, from coffee in Brazil and from field and greenhouse-grown wheat in France, the USA, Turkey and Syria. Immersion freezing was used to determine freezing onset temperatures and the abundance of ice nuclei in suspensions of washed spores. Microbiological analyses of spores and subsequent tests of the ice nucleation activity of the bacteria associated with spores were deployed to quantify the contribution of bacteria to the ice nucleation activity of the spores. All samples of spores were ice nucleation active having freezing onset temperatures as warm as -4 °C. Spores in most of the samples carried cells of ice nucleation-active strains of the bacterium Pseudomonas syringae (at rates of less than 1 bacterial cell per 100 urediospores), but bacterial INA accounted for only a small fraction of the INA observed in spore suspensions. Changes in the INA of spore suspensions after treatment with lysozyme suggest that the INA of urediospores involves a polysaccharide. Based on data from the literature, we have estimated the concentrations of urediospores in air at cloud height and in rainfall. These quantities are very similar to those reported for other biological ice nucleators in these same substrates. We suggest that air sampling techniques have ignored the spatial and temporal variability of atmospheric concentrations that occur under conditions propitious for precipitation that could increase their local abundance intermittently. Nevertheless, we propose that the relative low abundance of warm-temperature biological ice nucleators in the

  5. Significant alterations in anisotropic ice growth rate induced by the ice nucleation-active bacteria Xanthomonas campestris

    NASA Astrophysics Data System (ADS)

    Nada, Hiroki; Zepeda, Salvador; Miura, Hitoshi; Furukawa, Yoshinori

    2010-09-01

    In the present study, we found that the ice nucleation-active bacteria Xanthomonas campestris significantly altered anisotropic ice growth rate. Results of ice growth experiments in the presence of X. campestris showed that this bacterium decreased the ice crystal growth rate in the c-axis, whereas it increased growth rates in directions normal to the c-axis. These results indicate that these alterations in anisotropic growth rate are the result of selective binding of bacterial ice-nucleating proteins along the {0 0 0 1} basal plane.

  6. Measurement of Ice Nucleation-Active Bacteria on Plants and in Precipitation by Quantitative PCR

    PubMed Central

    Moffett, Bruce F.; DeMott, Paul J.; Georgakopoulos, Dimitrios G.; Stump, William L.; Franc, Gary D.

    2014-01-01

    Ice nucleation-active (INA) bacteria may function as high-temperature ice-nucleating particles (INP) in clouds, but their effective contribution to atmospheric processes, i.e., their potential to trigger glaciation and precipitation, remains uncertain. We know little about their abundance on natural vegetation, factors that trigger their release, or persistence of their ice nucleation activity once airborne. To facilitate these investigations, we developed two quantitative PCR (qPCR) tests of the ina gene to directly count INA bacteria in environmental samples. Each of two primer pairs amplified most alleles of the ina gene and, taken together, they should amplify all known alleles. To aid primer design, we collected many new INA isolates. Alignment of their partial ina sequences revealed new and deeply branching clades, including sequences from Pseudomonas syringae pv. atropurpurea, Ps. viridiflava, Pantoea agglomerans, Xanthomonas campestris, and possibly Ps. putida, Ps. auricularis, and Ps. poae. qPCR of leaf washings recorded ∼108 ina genes g−1 fresh weight of foliage on cereals and 105 to 107 g−1 on broadleaf crops. Much lower populations were found on most naturally occurring vegetation. In fresh snow, ina genes from various INA bacteria were detected in about half the samples but at abundances that could have accounted for only a minor proportion of INP at −10°C (assuming one ina gene per INA bacterium). Despite this, an apparent biological source contributed an average of ∼85% of INP active at −10°C in snow samples. In contrast, a thunderstorm hail sample contained 0.3 INA bacteria per INP active at −10°C, suggesting a significant contribution to this sample. PMID:24317082

  7. Measurement of ice nucleation-active bacteria on plants and in precipitation by quantitative PCR.

    PubMed

    Hill, Thomas C J; Moffett, Bruce F; Demott, Paul J; Georgakopoulos, Dimitrios G; Stump, William L; Franc, Gary D

    2014-02-01

    Ice nucleation-active (INA) bacteria may function as high-temperature ice-nucleating particles (INP) in clouds, but their effective contribution to atmospheric processes, i.e., their potential to trigger glaciation and precipitation, remains uncertain. We know little about their abundance on natural vegetation, factors that trigger their release, or persistence of their ice nucleation activity once airborne. To facilitate these investigations, we developed two quantitative PCR (qPCR) tests of the ina gene to directly count INA bacteria in environmental samples. Each of two primer pairs amplified most alleles of the ina gene and, taken together, they should amplify all known alleles. To aid primer design, we collected many new INA isolates. Alignment of their partial ina sequences revealed new and deeply branching clades, including sequences from Pseudomonas syringae pv. atropurpurea, Ps. viridiflava, Pantoea agglomerans, Xanthomonas campestris, and possibly Ps. putida, Ps. auricularis, and Ps. poae. qPCR of leaf washings recorded ∼10(8) ina genes g(-1) fresh weight of foliage on cereals and 10(5) to 10(7) g(-1) on broadleaf crops. Much lower populations were found on most naturally occurring vegetation. In fresh snow, ina genes from various INA bacteria were detected in about half the samples but at abundances that could have accounted for only a minor proportion of INP at -10°C (assuming one ina gene per INA bacterium). Despite this, an apparent biological source contributed an average of ∼85% of INP active at -10°C in snow samples. In contrast, a thunderstorm hail sample contained 0.3 INA bacteria per INP active at -10°C, suggesting a significant contribution to this sample.

  8. Characterization of airborne ice-nucleation-active bacteria and bacterial fragments

    NASA Astrophysics Data System (ADS)

    Šantl-Temkiv, Tina; Sahyoun, Maher; Finster, Kai; Hartmann, Susan; Augustin-Bauditz, Stefanie; Stratmann, Frank; Wex, Heike; Clauss, Tina; Nielsen, Niels Woetmann; Sørensen, Jens Havskov; Korsholm, Ulrik Smith; Wick, Lukas Y.; Karlson, Ulrich Gosewinkel

    2015-05-01

    Some bacteria have the unique capacity of synthesising ice-nucleation-active (INA) proteins and exposing them at their outer membrane surface. As INA bacteria enter the atmosphere, they may impact the formation of clouds and precipitation. We studied members of airborne bacterial communities for their capacity to catalyse ice formation and we report on the excretion of INA proteins by airborne Pseudomonas sp. We also observed for the first time that INA biological fragments <220 nm were present in precipitation samples (199 and 482 INA fragments per L of precipitation), which confirms the presence of submicron INA biological fragments in the atmosphere. During 14 precipitation events, strains affiliated with the genus Pseudomonas, which are known to carry ina genes, were dominant. A screening for INA properties revealed that ∼12% of the cultivable bacteria caused ice formation at ≤-7 °C. They had likely been emitted to the atmosphere from terrestrial surfaces, e.g. by convective transport. We tested the ability of isolated INA strains to produce outer membrane vesicles and found that two isolates could do so. However, only very few INA vesicles were released per INA cell. Thus, the source of the submicron INA proteinaceous particles that we detected in the atmosphere remains to be elucidated.

  9. The ice nucleation activity of extremophilic algae.

    PubMed

    Kviderova, Jana; Hajek, Josef; Worland, Roger M

    2013-01-01

    Differences in the level of cold acclimation and cryoprotection estimated as ice nucleation activity in snow algae (Chlamydomonas cf. nivalis and Chloromonas nivalis), lichen symbiotic algae (Trebouxia asymmetrica, Trebouxia erici and Trebouxia glomerata), and a mesophilic strain (Chlamydomonas reinhardti) were evaluated. Ice nucleation activity was measured using the freezing droplet method. Measurements were performed using suspensions of cells of A750 (absorbance at 750 nm) ~ 1, 0.1, 0.01 and 0.001 dilutions for each strain. The algae had lower ice nucleation activity, with the exception of Chloromonas nivalis contaminated by bacteria. The supercooling points of the snow algae were higher than those of lichen photobionts. The supercooling points of both, mesophilic and snow Chlamydomonas strains were similar. The lower freezing temperatures of the lichen algae may reflect either the more extreme and more variable environmental conditions of the original localities or the different cellular structure of the strains examined.

  10. Direct Quantification of Ice Nucleation Active Bacteria in Aerosols and Precipitation: Their Potential Contribution as Ice Nuclei

    NASA Astrophysics Data System (ADS)

    Hill, T. C.; DeMott, P. J.; Garcia, E.; Moffett, B. F.; Prenni, A. J.; Kreidenweis, S. M.; Franc, G. D.

    2013-12-01

    Ice nucleation active (INA) bacteria are a potentially prodigious source of highly active (≥-12°C) atmospheric ice nuclei, especially from agricultural land. However, we know little about the conditions that promote their release (eg, daily or seasonal cycles, precipitation, harvesting or post-harvest decay of litter) or their typical contribution to the pool of boundary layer ice nucleating particles (INP). To initiate these investigations we developed a quantitative Polymerase Chain Reaction (qPCR) test of the ina gene, the gene that codes for the ice nucleating protein, to directly count INA bacteria in environmental samples. The qPCR test amplifies most forms of the gene and is highly sensitive, able to detect perhaps a single gene copy (ie, a single bacterium) in DNA extracted from precipitation. Direct measurement of the INA bacteria is essential because environmental populations will be a mixture of living, viable-but-not culturable, moribund and dead cells, all of which may retain ice nucleating proteins. Using the qPCR test on leaf washings of plants from three farms in Wyoming, Colorado and Nebraska we found INA bacteria to be abundant on crops, especially on cereals. Mid-summer populations on wheat and barley were ~108/g fresh weigh of foliage. Broadleaf crops, such as corn, alfalfa, sugar beet and potato supported 105-107/g. Unexpectedly, however, in the absence of a significant physical disturbance, such as harvesting, we were unable to detect the ina gene in aerosols sampled above the crops. Likewise, in fresh snow samples taken over two winters, ina genes from a range of INA bacteria were detected in about half the samples but at abundances that equated to INA bacterial numbers that accounted for only a minor proportion of INP active at -10°C. By contrast, in a hail sample from a summer thunderstorm we found 0.3 INA bacteria per INP at -10°C and ~0.5 per hail stone. Although the role of the INA bacteria as warm-temperature INP in these samples

  11. Ice nucleation activity of polysaccharides

    NASA Astrophysics Data System (ADS)

    Bichler, Magdalena; Felgitsch, Laura; Haeusler, Thomas; Seidl-Seiboth, Verena; Grothe, Hinrich

    2015-04-01

    Heterogeneous ice nucleation is an important process in the atmosphere. It shows direct impact on our climate by triggering ice cloud formation and therefore it has much influence on the radiation balance of our planet (Lohmann et al. 2002; Mishchenko et al. 1996). The process itself is not completely understood so far and many questions remain open. Different substances have been found to exhibit ice nucleation activity (INA). Due to their vast differences in chemistry and morphology it is difficult to predict what substance will make good ice nuclei and which will not. Hence simple model substances must be found and be tested regarding INA. Our work aims at gaining to a deeper understanding of heterogeneous ice nucleation. We intend to find some reference standards with defined chemistry, which may explain the mechanisms of heterogeneous ice nucleation. A particular focus lies on biological carbohydrates in regards to their INA. Biological carbohydrates are widely distributed in all kingdoms of life. Mostly they are specific for certain organisms and have well defined purposes, e.g. structural polysaccharides like chitin (in fungi and insects) and pectin (in plants), which has also water-binding properties. Since they are widely distributed throughout our biosphere and mostly safe to use for nutrition purposes, they are well studied and easily accessible, rendering them ideal candidates as proxies. In our experiments we examined various carbohydrates, like the already mentioned chitin and pectin, as well as their chemical modifications. Lohmann U.; A Glaciation Indirect Aerosol Effect Caused by Soot Aerosols; J. Geoph. Res.; Vol. 24 No.4; pp 11-1 - 11-4; 2002 Mishchenko M.I., Rossow W.B., Macke A., Lacis A. A.; Sensitivity of Cirrus Cloud Albedo, Bidirectional Reflectance and Optical Thickness Retrieval Accuracy to Ice Particle Shape, J. Geoph. Res.; Vol. 101, No D12; pp. 16,973 - 16,985; 1996

  12. Molecular Ice Nucleation Activity of Birch Pollen

    NASA Astrophysics Data System (ADS)

    Felgitsch, Laura; Bichler, Magdalena; Häusler, Thomas; Weiss, Victor U.; Marchetti-Deschmann, Martina; Allmaier, Günter; Grothe, Hinrich

    2015-04-01

    Heterogeneous ice nucleation plays a major part in ecosystem and climate. Due to the triggering of ice cloud formation it influences the radiation balance of the earth, but also on the ground it can be found to be important in many processes of nature. So far the process of heterogeneous ice nucleation is not fully understood and many questions remain to be answered. Biological ice nucleation is hereby from great interest, because it shows the highest freezing temperatures. Several bacteria and fungi act as ice nuclei. A famous example is Pseudomonas syringae, a bacterium in commercial use (Snomax®), which increases the freezing from homogeneous freezing temperatures of approx. -40° C (for small volumes as in cloud droplets) to temperatures up to -2° C. In 2001 it was found that birch pollen can trigger ice nucleation (Diehl et al. 2001; Diehl et al. 2002). For a long time it was believed that this is due to macroscopic features of the pollen surface. Recent findings of Bernhard Pummer (2012) show a different picture. The ice nuclei are not attached on the pollen surface directly, but on surface material which can be easily washed off. This shows that not only the surface morphology, but also specific molecules or molecular structures are responsible for the ice nucleation activity of birch pollen. With various analytic methods we work on elucidating the structure of these molecules as well as the mechanism with which they trigger ice nucleation. To solve this we use various instrumental analytic techniques like Nuclear Magnetic Resonance spectroscopy (NMR), Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS), and Gas-phase Electrophoretic Mobility Molecular Analysis (GEMMA). Also standard techniques like various chromatographic separation techniques and solvent extraction are in use. We state here that this feature might be due to the aggregation of small molecules, with agglomerates showing a specific surface structure. Our results

  13. The ice nucleation activity of biological aerosols

    NASA Astrophysics Data System (ADS)

    Grothe, H.; Pummer, B.; Bauer, H.; Bernardi, J.

    2012-04-01

    Primary Biological Aerosol Particles (PBAPs), including bacteria, spores and pollen may be important for several atmospheric processes. Particularly, the ice nucleation caused by PBAPs is a topic of growing interest, since their impact on ice cloud formation and thus on radiative forcing, an important parameter in global climate is not yet fully understood. In laboratory model studies we investigated the ice nucleation activity of selected PBAPs. We studied the immersion mode freezing using water-oil emulsion, which we observed by optical microscopy. We particularly focused on pollen. We show that pollen of different species strongly differ in their ice nucleation behavior. The average freezing temperatures in laboratory experiments range from 240 K to 255 K. As the most efficient nuclei (silver birch, Scots pine and common juniper pollen) have a distribution area up to the Northern timberline, their ice nucleation activity might be a cryoprotective mechanism. For comparison the ice nucleation activity of Snomax, fungal spores, and mushrooms will be discussed as well. In the past, pollen have been rejected as important atmospheric IN, as they are not as abundant in the atmosphere as bacteria or mineral dust and are too heavy to reach higher altitudes. However, in our experiments (Pummer et al. 2011) it turned out that water, which had been in contact with pollen and then been separated from the bodies, nucleates as good as the pollen grains themselves. So the ice nuclei have to be easily-suspendable macromolecules (100-300 kDa) located on the pollen. Once extracted, they can be distributed further through the atmosphere than the heavy pollen grains and so augment the impact of pollen on ice cloud formation even in the upper troposphere. It is widely known, that material from the pollen, like allergens and sugars, can indeed leave the pollen body and be distributed independently. The most probable mechanism is the pollen grain bursting by rain, which releases

  14. Spider silk has an ice nucleation activity.

    PubMed

    Murase, N; Ruike, M; Matsunaga, N; Hayakawa, M; Kaneko, Y; Ono, Y

    2001-03-01

    Several ice nucleating substances have been identified, which exist in vivo or can be extracted from biological materials. Spider silk, which has a strong ability for water condensation, has also been found to possess an ice nucleation activity. The freezing temperature of water droplets was higher in the presence than in the absence of spider silk. Moreover, by means of environmental scanning electron microscopy, it was observed that the activity is not due to foreign matter attached to the silk but to the silk fibroin itself.

  15. Supercooling ability in two populations of the land snail Helix pomatia (Gastropoda: Helicidae) and ice-nucleating activity of gut bacteria.

    PubMed

    Nicolai, Annegret; Vernon, Philippe; Lee, Marcia; Ansart, Armelle; Charrier, Maryvonne

    2005-02-01

    the presence of endogenous ice-nucleating-active bacteria, accounts for fluctuations in their T(c).

  16. Identification of Ice Nucleation Active Sites on Silicate Dust Particles

    NASA Astrophysics Data System (ADS)

    Zolles, Tobias; Burkart, Julia; Häusler, Thomas; Pummer, Bernhard; Hitzenberger, Regina; Grothe, Hinrich

    2015-04-01

    Mineral dusts originating from Earth's crust are known to be important atmospheric ice nuclei. In agreement with earlier studies, feldspar was found as the most active of the tested natural mineral dusts [1-3]. Nevertheless, among those structures K-feldspar showed by far the highest ice nucleation activity. In this study, the reasons for its activity and the difference in the activity of the different feldspars were investigated in closer details. Conclusions are drawn from scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, and oil-immersion freezing experiments. We give a potential explanation of the increased ice nucleation activity of K-feldspar. The ice nucleating sites are very much dependent on the alkali ion present by altering the water structure and the feldspar surface. The higher activity of K-feldspar can be attributed to the presence of potassium ions on the surface and surface bilayer. The alkali-ions have different hydration shells and thus an influence on the ice nucleation activity of feldspar. Chaotropic behavior of Calcium and Sodium ions are lowering the ice nucleation potential of the other feldspars, while kosmotropic Potassium has a neutral or even positive effect. Furthermore we investigated the influence of milling onto the ice nucleation of quartz particles. The ice nucleation activity can be increased by mechanical milling, by introducing more molecular, nucleation active defects to the particle surface. This effect is larger than expected by plane surface increase. [1] Atkinson et al. The Importance of Feldspar for Ice Nucleation by Mineral Dust in Mixed-Phase Clouds. Nature 2013, 498, 355-358. [2] Yakobi-Hancock et al.. Feldspar Minerals as Efficient Deposition Ice Nuclei. Atmos. Chem. Phys. 2013, 13, 11175-11185. [3] Zolles et al. Identification of Ice Nucleation Active Sites on Feldspar Dust Particles. J. Phys. Chem. A 2015 accepted.

  17. Identification and quantification of ice nucleation active microorganisms by digital droplet PCR (ddPCR)

    NASA Astrophysics Data System (ADS)

    Linden, Martin; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

    2015-04-01

    Several bioaerosol types, including bacteria, fungi, pollen and lichen, have been identified as sources of biological ice nucleators (IN) which induce ice formation already at temperatures as high as -10 °C or above. Accordingly, they potentially contribute widely to environmental ice nucleation in the atmosphere and are of great interest in the study of natural heterogenous ice nucleation processes. Ice nucleation active microorganisms have been found and studied among bacteria (Proteobacteria) and fungi (phyla Basidiomycota and Ascomycota). The mechanisms enabling the microorganisms to ice nucleation are subject to ongoing research. While it has been demonstrated that whole cells can act as ice nucleators in the case of bacteria due to the presence of specific membrane proteins, cell-free ice nucleation active particles seem to be responsible for this phenomenon in fungi and lichen. The identification and quantification of these ice nucleation active microorganisms and their IN in atmospheric samples is crucial to understand their contribution to the pool of atmospheric IN. This is not a trivial task since the respective microorganisms are often prevalent in lowest concentrations and a variety of states, be it viable cells, spores or cell debris from dead cells. Molecular biology provides tools to identify and quantify ice nucleation active microorganisms independent of their state by detecting genetic markers specific for the organism of interest. Those methods are not without their drawbacks in terms of sample material concentration required or reliable standardization. Digital Droplet Polymerase Chain Reaction (ddPCR) was chosen for our demands as a more elegant, quick and specific method in the investigation of ice nucleation active microorganisms in atmospheric samples. The advantages of ddPCR lie in the simultaneous detection and quantification of genetic markers and their original copy numbers in a sample. This is facilitated by the fractionation of the

  18. Ice nucleating activity of Pseudomonas syringae and Erwinia herbicola.

    PubMed Central

    Kozloff, L M; Schofield, M A; Lute, M

    1983-01-01

    Chemical and biological properties of the ice nucleating sites of Pseudomonas syringae, strain C-9, and Erwinia herbicola have been characterized. The ice nucleating activity (INA) for both bacteria was unchanged in buffers ranging from pH 5.0 to 9.2, suggesting that there were no essential groups for which a change in charge in this range was critical. The INA of both bacteria was also unaffected by the addition of metal chelating compounds. Borate compounds and certain lectins markedly inhibited the INA of both types of bacterial cells. Butyl borate was not an inhibitor, but borate, phenyl borate, and m-nitrophenyl borate were, in order, increasingly potent inhibitors. These compounds have a similar order of affinity for cis hydroxyls, particularly for those found on sugars. Lentil lectin and fava bean lectin, which have binding sites for mannose or glucose, inhibited the INA of both bacteria. All other lectins examined had no effect. The inhibition of INA by these two types of reagents indicate that sugar-like groups are at or near the ice nucleating site. Sulfhydryl reagents were potent inhibitors of the INA of both bacteria. When treated with N-ethylmaleimide, p-hydroxymercuribenzoate, or iodoacetamide, the INA was irreversibly inhibited by 99%. The kinetics of inactivation with N-ethylmaleimide suggested that E. herbicola cells have at least two separate ice nucleating sites, whereas P. syringae cells have possibly four or more separate sites. The effect of infection with a virulent phage (Erh 1) on the INA of E. herbicola was examined. After multiple infection of a bacterial culture the INA was unchanged until 40 to 45 min, which was midway through the 95-min latent period. At that time, the INA activity began falling and 99% of the INA was lost by 55 min after infection, well before any cells had lysed. This decrease in INA before lysis is attributed to phage-induced changes in the cell wall. PMID:6848483

  19. Biological Ice Nucleation Activity in Cloud Water (Invited)

    NASA Astrophysics Data System (ADS)

    Delort, A.

    2013-12-01

    Ice nucleation active (INA) biological particles, in particular microorganisms, were studied in cloud water. Twelve cloud samples were collected over a period of 16 months from the puy de Dôme summit (1465 m, France) using sterile cloud droplet impactors. The samples were characterized through biological (cultures, cell counts) and physico-chemical measurements (pH, ion concentrations, carbon content...), and biological ice nuclei were investigated by droplet-freezing assays from -3°C to -13°C. The concentration of total INA particles within this temperature range typically varied from ~1 to ~100 per mL of cloud water; the concentrations of biological IN were several orders of magnitude higher than the values previously reported for precipitations. At -12°C, at least 76% of the IN were biological in origin, i.e. they were inactivated by heating at 95°C, and at temperatures above -8°C only biological material could induce ice. By culture, 44 Pseudomonas-like strains of bacteria were isolated from cloud water samples; 16% of them were found INA at the temperature of -8°C and they were identified as Pseudomonas syringae, Xanthomonas sp. and Pseudoxanthomonas sp.. Two strains induced freezing at as warm as -2°C, positioning them among the most active ice nucleators described so far. We estimated that, in average, 0.18% and more than 1%.of the bacterial cells present in clouds (~104 mL-1) are INA at the temperatures of -8°C and -12°C, respectively.

  20. Identification of Ice Nucleation Active Sites on Feldspar Dust Particles

    PubMed Central

    2015-01-01

    Mineral dusts originating from Earth’s crust are known to be important atmospheric ice nuclei. In agreement with earlier studies, feldspar was found as the most active of the tested natural mineral dusts. Here we investigated in closer detail the reasons for its activity and the difference in the activity of the different feldspars. Conclusions are drawn from scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, and oil-immersion freezing experiments. K-feldspar showed by far the highest ice nucleation activity. Finally, we give a potential explanation of this effect, finding alkali-metal ions having different hydration shells and thus an influence on the ice nucleation activity of feldspar surfaces. PMID:25584435

  1. Clustering of ice nucleation protein correlates with ice nucleation activity.

    PubMed

    Mueller, G M; Wolber, P K; Warren, G J

    1990-08-01

    Antibodies raised against a synthetic peptide specifically detect ice nucleation proteins from Pseudomonas species in Western blots. In immunofluorescent staining of whole bacteria, the antibodies reveal the protein in clusters, as indicated by patches of intense fluorescence in Escherichia coli cells heterologously expressing Pseudomonas ice nucleation genes. The abundance, size, and brightness of the clusters vary considerably from cell to cell. Their varying sizes may explain the variability in activity of bacterial ice nuclei. Growth at lower temperatures produces more ice nuclei, and gives brighter and more frequent patches, than growth at 37 degrees C. The observed clustering may thus reflect formation of functional ice nucleation sites in vivo. The presence of ice nucleation protein in clusters is also correlated with alterations in cell morphology.

  2. Rocket effluent: Its ice nucleation activity and related properties

    NASA Technical Reports Server (NTRS)

    Parungo, F. P.; Allee, P. A.

    1978-01-01

    To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions.

  3. The Ice Nucleation Activity of Surface Modified Soot

    NASA Astrophysics Data System (ADS)

    Häusler, Thomas; Witek, Lorenz; Felgitsch, Laura; Hitzenberger, Regina; Grothe, Hinrich

    2017-04-01

    The ice nucleation efficiency of many important atmospheric particles remains poorly understood. Since soot is ubiquitous in the Earth's troposphere, they might have the potential to significantly impact the Earth's climate (Finlayson-Pitts and Pitts, 2000; Seinfeld and Pandis, 1998). Here we present the ice nucleation activity (INA) in immersion freezing mode of different types of soot. Therefor a CAST (combustion aerosol standard) generator was used to produce different kinds of soot samples. The CAST generator combusts a propane-air-mixture and deposits thereby produced soot on a polyvinyl fluoride filter. By varying the propane to air ratio, the amount of organic portion of the soot can be varied from black carbon (BC) with no organic content to brown carbon (BrC) with high organic content. To investigate the impact of functional sites of ice nuclei (IN), the soot samples were exposed to NO2 gas for a certain amount of time (30 to 360 minutes) to chemically modify the surface. Immersion freezing experiments were carried out in a unique reaction gadget. In this device a water-in-oil suspension (with the soot suspended in the aqueous phase) was cooled till the freezing point and was observed through a microscope (Pummer et al., 2012; Zolles et al., 2015) It was found that neither modified nor unmodified BC shows INA. On the contrary, unmodified BrC shows an INA at -32˚ C, which can be increased up to -20˚ C. The INA of BrC depends on the duration of NO2- exposure. To clarify the characteristics of the surface modifications, surface sensitive analysis like infrared spectroscopy and X-ray photoelectron spectroscopy were carried out. Finlayson-Pitts, B. J. and Pitts, J. N. J.: Chemistry of the Upper and Lower Atmosphere, Elsevier, New York, 2000. Pummer, B. G., Bauer, H., Bernardi, J., Bleicher, S., and Grothe, H.: Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen, Atmos Chem Phys, 12, 2541-2550, 2012. Seinfeld, J

  4. Ice Nucleation Activity of Various Agricultural Soil Dust Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Schiebel, Thea; Höhler, Kristina; Funk, Roger; Hill, Thomas C. J.; Levin, Ezra J. T.; Nadolny, Jens; Steinke, Isabelle; Suski, Kaitlyn J.; Ullrich, Romy; Wagner, Robert; Weber, Ines; DeMott, Paul J.; Möhler, Ottmar

    2016-04-01

    detail to gain additional information on the trigger of the enhanced ice nucleation activity of soil dust. References Rogers (1988): Development of a continuous flow thermal gradient diffusion chamber for ice nucleation studies Steinke et al. (In preparation for submission): Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina and Germany

  5. Ice Nucleation Activity in the Widespread Soil Fungus Mortierella alpina

    NASA Astrophysics Data System (ADS)

    Fröhlich-Nowoisky, J.; Hill, T. C. J.; Pummer, B. G.; Franc, G. D.; Pöschl, U.

    2014-08-01

    Biological residues in soil dust are a potentially strong source of atmospheric ice nuclei (IN). So far, however, the abundance, diversity, sources, seasonality, and role of biological - in particular, fungal - IN in soil dust have not been characterized. By analysis of the culturable fungi in topsoils, from a range of different land use and ecosystem types in south-east Wyoming, we found ice nucleation active (INA) fungi to be both widespread and abundant, particularly in soils with recent inputs of decomposable organic matter. Across all investigated soils, 8% of fungal isolates were INA. All INA isolates initiated freezing at -5 to -6 °C, and belonged to a single zygomycotic species, Mortierella alpina (Mortierellales, Mortierellomycotina). By contrast, the handful of fungal species so far reported as INA all belong within the Ascomycota or Basidiomycota phyla. M. alpina is known to be saprobic, widespread in soil and present in air and rain. Sequencing of the ITS region and the gene for γ-linolenic-elongase revealed four distinct clades, affiliated to different soil types. The IN produced by M. alpina seem to be proteinaceous, <300 kDa in size, and can be easily washed off the mycelium. Ice nucleating fungal mycelium will ramify topsoils and probably also release cell-free IN into it. If these IN survive decomposition or are adsorbed onto mineral surfaces, their contribution might accumulate over time, perhaps to be transported with soil dust and influencing its ice nucleating properties.

  6. Ice nucleation activity in the widespread soil fungus Mortierella alpina

    NASA Astrophysics Data System (ADS)

    Fröhlich-Nowoisky, Janine; Hill, Thomas C. J.; Pummer, Bernhard G.; Yordanova, Petya; Franc, Gary D.; Pöschl, Ulrich

    2015-04-01

    Biological residues in soil dust are a potentially strong source of atmospheric ice nucleators (IN). However, the sources and characteristics of biological - in particular, fungal - IN in soil dust have not been characterized. By analysis of the culturable fungi in topsoils, from a range of different land use and ecosystem types in south-east Wyoming, we found ice nucleation active (INA, i.e., inducing ice formation in the probed range of temperature and concentration) fungi to be both widespread and abundant, particularly in soils with recent inputs of decomposable organic matter. For example, in harvested and ploughed sugar beet and potato fields, and in the organic horizon beneath Lodgepole pine forest, their relative abundances and concentrations among the cultivable fungi were 25% (8 x 103 CFU g-1), 17% (4.8 x 103 CFU g-1) and 17% (4 x 103 CFU g-1), respectively. Across all investigated soils, 8% (2.9 x 103 CFU g-1) of fungal isolates were INA. All INA isolates initiated freezing at -5° C to -6° C and all belonged to a single zygomycotic species, Mortierella alpina (Mortierellales, Mortierellomycotina). By contrast, the handful of fungal species so far reported as INA all belong within the Ascomycota or Basidiomycota phyla. Mortierella alpina is known to be saprobic (utilizing non-living organic matter), widespread in soil and present in air and rain. Sequencing of the ITS region and the gene for γ-linolenic elongase revealed four distinct clades, affiliated to different soil types. The IN produced by M. alpina seem to be extracellular proteins of 100-300 kDa in size which are not anchored in the fungal cell wall. Ice nucleating fungal mycelium will ramify topsoils and probably also release cell-free IN into it. If these IN survive decomposition or are adsorbed onto mineral surfaces, these small cell-free IN might contribute to the as yet uncharacterized pool of atmospheric IN released by soils as dusts.

  7. Identification of ice-nucleating active Pseudomonas fluorescens strains for biological control of overwintering Colorado potato beetles (Coleoptera: Chrysomelidae).

    PubMed

    Castrillo, L A; Lee, R E; Lee, M R; Rutherford, S T

    2000-04-01

    Laboratory studies were conducted to identify ice-nucleating active bacterial strains able to elevate the supercooling point, the temperature at which freezing is initiated in body fluids, of Colorado potato beetles, Leptinotarsa decemlineata (Say), and to persist in their gut. Adult beetles fed ice-nucleating active strains of Pseudomonas fluorescens, P. putida, or P. syringae at 10(6) or 10(3) bacterial cells per beetle had significantly elevated supercooling points, from -4.5 to -5.7 degrees C and from -5.2 to -6.6 degrees C, respectively, immediately after ingestion. In contrast, mean supercooling point of untreated control beetles was -9.2 degrees C. When sampled at 2 and 12 wk after ingestion, only beetles fed P. fluorescens F26-4C and 88-335 still had significantly elevated supercooling points, indicating that these strains of bacteria were retained. Furthermore, beetle supercooling points were comparable to those observed immediately after ingestion, suggesting that beetle gut conditions were favorable not only for colonization but also for expression of ice-nucleating activity by these two strains. The results obtained from exposure to a single, low dose of either bacterial strain also show that a minimum amount of inoculum is sufficient for establishment of the bacterium in the gut. Persistence of these bacteria in Colorado potato beetles long after ingestion was also confirmed using a polymerase chain reaction technique that detected ice-nucleating active bacteria by virtue of their ina genes. Application of these ice-nucleating active bacteria to elevate the supercooling point of this freeze-intolerant insect pest could significantly reduce their winter survival, thereby reducing local populations and, consequently, crop damage.

  8. Anti-ice nucleation activity in xylem extracts from trees that contain deep supercooling xylem parenchyma cells.

    PubMed

    Kasuga, Jun; Mizuno, Kaoru; Arakawa, Keita; Fujikawa, Seizo

    2007-12-01

    Boreal hardwood species, including Japanese white birch (Betula platyphylla Sukat. var. japonica Hara), Japanese chestnut (Castanea crenata Sieb. et Zucc.), katsura tree (Cercidiphyllum japonicum Sieb. et Zucc.), Siebold's beech (Fagus crenata Blume), mulberry (Morus bombycis Koidz.), and Japanese rowan (Sorbus commixta Hedl.), had xylem parenchyma cells (XPCs) that adapt to subfreezing temperatures by deep supercooling. Crude extracts from xylem in all these trees were found to have anti-ice nucleation activity that promoted supercooling capability of water as measured by a droplet freezing assay. The magnitude of increase in supercooling capability of water droplets in the presence of ice-nucleation bacteria, Erwinia ananas, was higher in the ranges from 0.1 to 1.7 degrees C on addition of crude xylem extracts than freezing temperature of water droplets on addition of glucose in the same concentration (100 mosmol/kg). Crude xylem extracts from C. japonicum provided the highest supercooling capability of water droplets. Our additional examination showed that crude xylem extracts from C. japonicum exhibited anti-ice nucleation activity toward water droplets containing a variety of heterogeneous ice nucleators, including ice-nucleation bacteria, not only E. ananas but also Pseudomonas syringae (NBRC3310) or Xanthomonas campestris, silver iodide or airborne impurities. However, crude xylem extracts from C. japonicum did not affect homogeneous ice nucleation temperature as analyzed by emulsified micro-water droplets. The possible role of such anti-ice nucleation activity in crude xylem extracts in deep supercooling of XPCs is discussed.

  9. Ice-Nucleating Bacteria

    NASA Astrophysics Data System (ADS)

    Obata, Hitoshi

    Since the discovery of ice-nucleating bacteria in 1974 by Maki et al., a large number of studies on the biological characteristics, ice-nucleating substance, ice nucleation gene and frost damage etc. of the bacteria have been carried out. Ice-nucleating bacteria can cause the freezing of water at relatively warm temperature (-2.3°C). Tween 20 was good substrates for ice-nucleating activity of Pseudomonas fluorescens KUIN-1. Major fatty acids of Isolate (Pseudomonas fluorescens) W-11 grown at 30°C were palmitic, cis-9-hexadecenoic and cis-11-octadecenoic which amounted to 90% of the total fatty acids. Sequence analysis shows that an ice nucleation gene from Pseudomonas fluorescens is related to the gene of Pseudomonas syringae.

  10. Anti-ice nucleating activity of polyphenol compounds against silver iodide.

    PubMed

    Koyama, Toshie; Inada, Takaaki; Kuwabara, Chikako; Arakawa, Keita; Fujikawa, Seizo

    2014-10-01

    Freeze-avoiding organisms survive sub-zero temperatures without freezing in several ways, such as removal of ice nucleating agents (INAs), production of polyols, and dehydration. Another way is production of anti-ice nucleating agents (anti-INAs), such as has been reported for several antifreeze proteins (AFPs) and polyphenols, that inhibit ice nucleation by inactivating INAs. In this study, the anti-ice nucleating activity of five polyphenol compounds, including flavonoid and tannin compounds of both biological and synthetic origin, against silver iodide (AgI) was examined by measuring the ice nucleation temperature in emulsified polyphenol solutions containing AgI particles. The emulsified solutions eliminated the influence of contamination by unidentified INAs, thus enabling examination of the anti-ice nucleating activity of the polyphenols against AgI alone. Results showed that all five polyphenol compounds used here have anti-ice nucleating activities that are unique compared with other known anti-INAs, such as fish AFPs (type I and III) and synthetic polymers (poly(vinyl alcohol), poly(vinylpyrrolidone) and poly(ethylene glycol)). All five polyphenols completely inactivated the ice nucleating activity of AgI even at relatively low temperatures, and the first ice nucleation event was observed at temperatures between -14.1 and -19.4°C, compared with between -8.6 and -11.8°C for the fish AFPs and three synthetic polymers. These anti-ice nucleating activities of the polyphenols at such low temperatures are promising properties for practical applications where freezing should be prevented. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Transgenic ice nucleation-active Enterobacter cloacae reduces cold hardiness of corn borer and cotton bollworm larvae.

    PubMed

    Tang, Chaorong; Sun, Fuzai; Zhang, Xinjian; Zhao, Tingchang; Qi, Jiyan

    2004-12-27

    The ice nucleation (IN) gene iceA of Erwinia ananas 110 was integrated into the chromosomes of two Enterobacter cloacae strains (Enc1.2022 and Enc1.181). These two newly derived transgenic strains, designated Enc2022-I and Enc181-I, respectively, possessed ice nucleation activity at -2.5 degrees C, significantly higher than their parent strains (active at approx -10 degrees C or lower). After ingesting these transgenic bacteria, the mean supercooling points (SCPs) of corn borer and cotton bollworm larvae were -3 to -4 degrees C, significantly higher than those of untreated controls. The SCPs remained significantly elevated over the 9-day period after ingestion, which matched well with the efficient gut colonization of the bacteria during this period. All treated larvae froze and eventually died after exposure for 6 h to a temperature of -7 degrees C, and more than 95% died after 12 h at -5 degrees C. In contrast, few or none of the untreated control larvae froze and died under the same conditions. Furthermore, the growth ability of these transgenic ice nucleation-active (INA) En. cloacae strains on corn leaves was reduced, compared to that of wild-type epiphytic E. ananas, as revealed by pot tests conducted in both greenhouse and outdoor conditions. The stable colonization in insect guts and their lower affinity to plants would make these transgenic INA bacteria useful as a novel tool for biological control of insect pests in agricultural fields.

  12. Soot Aerosol Particles as Cloud Condensation Nuclei: from Ice Nucleation Activity to Ice Crystal Morphology

    NASA Astrophysics Data System (ADS)

    Pirim, Claire; Ikhenazene, Raouf; Ortega, Isamel Kenneth; Carpentier, Yvain; Focsa, Cristian; Chazallon, Bertrand; Ouf, François-Xavier

    2016-04-01

    Emissions of solid-state particles (soot) from engine exhausts due to incomplete fuel combustion is considered to influence ice and liquid water cloud droplet activation [1]. The activity of these aerosols would originate from their ability to be important centers of ice-particle nucleation, as they would promote ice formation above water homogeneous freezing point. Soot particles are reported to be generally worse ice nuclei than mineral dust because they activate nucleation at higher ice-supersaturations for deposition nucleation and at lower temperatures for immersion freezing than ratios usually expected for homogeneous nucleation [2]. In fact, there are still numerous opened questions as to whether and how soot's physico-chemical properties (structure, morphology and chemical composition) can influence their nucleation ability. Therefore, systematic investigations of soot aerosol nucleation activity via one specific nucleation mode, here deposition nucleation, combined with thorough structural and compositional analyzes are needed in order to establish any association between the particles' activity and their physico-chemical properties. In addition, since the morphology of the ice crystals can influence their radiative properties [3], we investigated their morphology as they grow over both soot and pristine substrates at different temperatures and humidity ratios. In the present work, Combustion Aerosol STandart soot samples were produced from propane using various experimental conditions. Their nucleation activity was studied in deposition mode (from water vapor), and monitored using a temperature-controlled reactor in which the sample's relative humidity is precisely measured with a cryo-hygrometer. Formation of water/ice onto the particles is followed both optically and spectroscopically, using a microscope coupled to a Raman spectrometer. Vibrational signatures of hydroxyls (O-H) emerge when the particle becomes hydrated and are used to characterize ice

  13. Ice nucleation active particles are efficiently removed by precipitating clouds

    PubMed Central

    Stopelli, Emiliano; Conen, Franz; Morris, Cindy E.; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine

    2015-01-01

    Ice nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of ice nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ18O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs active at temperatures ≥ −10 °C (INPs−10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs active at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space. PMID:26553559

  14. Ice nucleation active particles are efficiently removed by precipitating clouds.

    PubMed

    Stopelli, Emiliano; Conen, Franz; Morris, Cindy E; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine

    2015-11-10

    Ice nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of ice nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ(18)O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs active at temperatures ≥ -10 °C (INPs-10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs active at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space.

  15. Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina, and Germany

    NASA Astrophysics Data System (ADS)

    Steinke, I.; Funk, R.; Busse, J.; Iturri, A.; Kirchen, S.; Leue, M.; Möhler, O.; Schwartz, T.; Schnaiter, M.; Sierau, B.; Toprak, E.; Ullrich, R.; Ulrich, A.; Hoose, C.; Leisner, T.

    2016-11-01

    Soil dust particles emitted from agricultural areas contain considerable mass fractions of organic material. Also, soil dust particles may act as carriers for potentially ice-active biological particles. In this work, we present ice nucleation experiments conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber. We investigated the ice nucleation efficiency of four types of soil dust from different regions of the world. The results are expressed as ice nucleation active surface site (INAS) densities and presented for the immersion freezing and the deposition nucleation mode. For immersion freezing occurring at 254 K, samples from Argentina, China, and Germany show ice nucleation efficiencies which are by a factor of 10 higher than desert dusts. On average, the difference in ice nucleation efficiencies between agricultural and desert dusts becomes significantly smaller at temperatures below 247 K. In the deposition mode the soil dusts showed higher ice nucleation activity than Arizona Test Dust over a temperature range between 232 and 248 K and humidities RHice up to 125%. INAS densities varied between 109 and 1011 m-2 for these thermodynamic conditions. For one soil dust sample (Argentinian Soil), the effect of treatments with heat was investigated. Heat treatments (383 K) did not affect the ice nucleation efficiency observed at 249 K. This finding presumably excludes proteinaceous ice-nucleating entities as the only source of the increased ice nucleation efficiency.

  16. Diel Variation in Population Size and Ice Nucleation Activity of Pseudomonas syringae on Snap Bean Leaflets.

    PubMed

    Hirano, S S; Upper, C D

    1989-03-01

    The extent to which diel changes in the physical environment affect changes in population size and ice nucleation activity of Pseudomonas syringae on snap bean leaflets was determined under field conditions. To estimate bacterial population size and ice nucleation activity, bean leaflets were harvested at 2-h intervals during each of three 26-h periods. A tube nucleation test was used to assay individual leaflets for ice nuclei. Population sizes of P. syringae were determined by dilution plating of leaflet homogenates. The overall diel changes in P. syringae population sizes differed during each of the 26-h periods. In one 26-h period, there was a continuous increase in the logarithm of P. syringae population size despite intense solar radiation, absence of free moisture on leaf surfaces, and low relative humidity during the day. A mean doubling time of approximately 4.9 h was estimated for the 28-fold increase in P. syringae population size that occurred from 0900 to 0900 h during the 26-h period. However, doubling times of 3.3 and 1.9 h occurred briefly during this period from 1700 to 2300 h and from 0100 to 0700 h, respectively. Thus, growth rates of P. syringae in association with leaves in the field were of the same order of magnitude as optimal rates measured in the laboratory. The frequency with which leaflets bore ice nuclei active at -2.0, -2.2, and -2.5 degrees C varied greatly within each 26-h period. These large diel changes were inversely correlated primarily with the diel changes in air temperature and reflected changes in nucleation frequency rather than changes in population size of P. syringae. Thus, the response of bacterial ice nucleation activity to the physical environment was distinct from the changes in population size of ice nucleation-active P. syringae.

  17. Analysis of supercooling-facilitating (anti-ice nucleation) activity of flavonol glycosides.

    PubMed

    Kasuga, Jun; Fukushi, Yukiharu; Kuwabara, Chikako; Wang, Donghui; Nishioka, Atsushi; Fujikawa, Emiko; Arakawa, Keita; Fujikawa, Seizo

    2010-04-01

    Deep supercooling xylem parenchyma cells (XPCs) of katsura tree (Cercidiphyllum japonicum) contain four kinds of flavonol glycosides with high supercooling-facilitating (anti-ice nucleation) activities. These flavonol glycosides have very similar structures, but their supercooling-facilitating activities are very different. In this study, we analyzed the supercooling-facilitating activities of 12 kinds of flavonol glycosides in order to determine the chemical structures that might affect supercooling-facilitating activity. All of the flavonol glycosides tested showed supercooling-facilitating activity, although the magnitudes of activity differed among the compounds. It was clear that the combination of the position of attachment of the glycosyl moiety, the kind of attached glycosyl moiety and the structure of aglycone determined the magnitude of anti-ice nucleation activity. However, there is still some ambiguity preventing the exact identification of features that affect the magnitude of supercooling-facilitating activity.

  18. Ice nucleation active particles in continental air samples over Mainz, Germany

    NASA Astrophysics Data System (ADS)

    Pummer, Bernhard G.; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

    2016-04-01

    Aerosol particles are of central importance for atmospheric chemistry and physics, climate and public health. Some of these particles possess ice nucleation activity (INA), which is highly relevant for cloud formation and precipitation. In 2010, air filter samples were collected with a high-volume filter sampler separating fine and coarse particles (aerodynamic cut-off diameter 3 μm) in Mainz, Germany. In this study, the INA of the atmospheric particles deposited on these filters was determined. Therefore,they were extracted with ultrapure water, which was then measured in a droplet freezing assay, as described in Fröhlich-Nowoisky et al. (2015). The determined concentration of ice nucleators (INs) was between 0.3 and 2per m³ at 266 K, and between5 and 75 per m³ at 260 K. The INs were further characterized by different treatments, like heating (308 K, 371 K), filtration (0.1 μm, 300 kDa), and digestion with papain (10 mg/ml). We further investigated, which atmospheric conditions (e.g. weather) and distinguished events (e.g. dust storms, volcanic eruptions, and pollen peaks) influenced the number and nature of these INs. Fröhlich-Nowoisky, J., Hill, T. C. J., Pummer, B. G., Yordanova, P., Franc, G. D., and Pöschl, U.: Ice nucleation activity in the widespread soil fungus Mortierella alpina, Biogeosci., 12, 1057-1071, doi:10.5194/bg-12-1057-2015, 2015.

  19. Ice nucleation activity in various tissues of Rhododendron flower buds: their relevance to extraorgan freezing

    PubMed Central

    Ishikawa, Masaya; Ishikawa, Mikiko; Toyomasu, Takayuki; Aoki, Takayuki; Price, William S.

    2015-01-01

    Wintering flower buds of cold hardy Rhododendron japonicum cooled slowly to subfreezing temperatures are known to undergo extraorgan freezing, whose mechanisms remain obscure. We revisited this material to demonstrate why bud scales freeze first in spite of their lower water content, why florets remain deeply supercooled and how seasonal adaptive responses occur in regard to extraorgan freezing in flower buds. We determined ice nucleation activity (INA) of various flower bud tissues using a test tube-based assay. Irrespective of collection sites, outer and inner bud scales that function as ice sinks in extraorgan freezing had high INA levels whilst florets that remain supercooled and act as a water source lacked INA. The INA level of bud scales was not high in late August when flower bud formation was ending, but increased to reach the highest level in late October just before the first autumnal freeze. The results support the following hypothesis: the high INA in bud scales functions as the subfreezing sensor, ensuring the primary freezing in bud scales at warmer subzero temperatures, which likely allows the migration of floret water to the bud scales and accumulation of icicles within the bud scales. The low INA in the florets helps them remain unfrozen by deep supercooling. The INA in the bud scales was resistant to grinding and autoclaving at 121∘C for 15 min, implying the intrinsic nature of the INA rather than of microbial origin, whilst the INA in stem bark was autoclaving-labile. Anti-nucleation activity (ANA) was implicated in the leachate of autoclaved bud scales, which suppresses the INA at millimolar levels of concentration and likely differs from the colligative effects of the solutes. The tissue INA levels likely contribute to the establishment of freezing behaviors by ensuring the order of freezing in the tissues: from the primary freeze to the last tissue remaining unfrozen. PMID:25859249

  20. Effect of an Ice-Nucleating Activity Agent on Subzero Survival of Nematode Juveniles

    PubMed Central

    Wergin, William P.; Yaklich, Robert W.; Carta, Lynn K.; Erbe, Eric F.; Murphy, Charles A.

    2000-01-01

    Juveniles of five species of nematodes, Caenorhabditis elegans, Panagrellus redivivus, Pratylenchus agilis, Pristionchus pacificus, and Distolabrellus veechi, were added to solutions with (treatment) and without (control) a commercial ice-nucleating activity (INA) agent. Ten-microliter droplets of the solutions containing the juveniles were placed on glass microscope slides and transferred to a temperaturecontrolled freeze plate where the temperature was reduced to -6 to -8 °C. At this temperature, the droplets containing the INA agent froze while those without the agent remained liquid. After 2 minutes, the temperature of the plate was raised to 24 °C, and the slides were examined with a light microscope to determine the viability of the juveniles. The results showed that usually most juveniles (43% to 88%, depending on species) in solutions that did not contain the INA agent (controls) were active, indicating that the juveniles were capable of supercooling and were thereby protected from the subzero temperatures. Alternatively, less than 10% of the juveniles that had frozen for 2 minutes in solutions containing the INA agent remained viable, indicating that inoculative freezing of the solution was lethal to the supercooled juveniles. Our results suggest that, in geographical areas where winter temperatures may not be sufficiently low or sustained to freeze soil, the addition of an INA agent may help induce ice nucleation and thereby reduce the populations of nematode species that are unable to survive when the soil solution is frozen. PMID:19270966

  1. Perturbation of bacterial ice nucleation activity by a grass antifreeze protein.

    PubMed

    Tomalty, Heather E; Walker, Virginia K

    2014-09-26

    Certain plant-associating bacteria produce ice nucleation proteins (INPs) which allow the crystallization of water at high subzero temperatures. Many of these microbes are considered plant pathogens since the formed ice can damage tissues, allowing access to nutrients. Intriguingly, certain plants that host these bacteria synthesize antifreeze proteins (AFPs). Once freezing has occurred, plant AFPs likely function to inhibit the growth of large damaging ice crystals. However, we postulated that such AFPs might also serve as defensive mechanisms against bacterial-mediated ice nucleation. Recombinant AFP derived from the perennial ryegrass Lolium perenne (LpAFP) was combined with INP preparations originating from the grass epiphyte, Pseudomonas syringae. The presence of INPs had no effect on AFP activity, including thermal hysteresis and ice recrystallization inhibition. Strikingly, the ice nucleation point of the INP was depressed up to 1.9°C in the presence of LpAFP, but a recombinant fish AFP did not lower the INP-imposed freezing point. Assays with mutant LpAFPs and the visualization of bacterially-displayed fluorescent plant AFP suggest that INP and LpAFP can interact. Thus, we postulate that in addition to controlling ice growth, plant AFPs may also function as a defensive strategy against the damaging effects of ice-nucleating bacteria. Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.

  2. Cellulose and Their Characteristic Ice Nucleation Activity- Freezing on a Chip

    NASA Astrophysics Data System (ADS)

    Häusler, Thomas; Felgitsch, Laura; Grothe, Hinrich

    2016-04-01

    The influence of clouds on the Earth's climate system is well known (IPCC, 2013). Cloud microphysics determines for example cloud lifetime and precipitation properties. Clouds are cooling the climate system by reflecting incoming solar radiation and warm its surface by trapping outgoing infrared radiation (Baker and Peter, 2008). In all these processes, aerosol particles play a crucial role by acting as cloud condensation nuclei (CCN) for liquid droplets and as an ice nucleation particle (INP) for the formation of ice particles. Freezing processes at higher temperatures than -38°C occur heterogeneously (Pruppacher and Klett 1997). Therefore aerosol particles act like a catalyst, which reduces the energy barrier for nucleation. The nucleation mechanisms, especially the theory of functional sites are not entirely understood. It remains unclear which class of compound nucleates ice. Here we present a unique technique to perform drop- freezing experiments in a more efficient way. A self-made freezing- chip will be presented. Measurements done to proof the efficiency of our setup as well as advantages compared with other setups will be discussed. Furthermore we present a proxy for biological INPs, microcrystalline cellulose. Cellulose is the main component of herbal cell walls (about 50 wt%). It is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose can contribute to the diverse spectrum of ice nucleation particles. We present results of the nucleation activity measurements of MCCs as well as the influence of concentration, preparation or chemical modification.

  3. Relationships between cold hardiness, and ice nucleating activity, glycerol and protein contents in the hemolymph of caterpillars, Aporia crataegi L.

    PubMed

    Li, N G

    2012-01-01

    Insects in Siberia must tolerate some of the coldest conditions on earth. The relationship between hemolymph ice nucleating activity, glycerol and total protein concentrations, and cold hardiness was explored in Aporia crataegi L. (Lepidoptera: Pieridae). Cold-hardened overwintering caterpillars were collected at a time of year when temperatures are regularly below -50 degree C, and warm-acclimated at +22 degree C, to see how changes in the physical and chemical properties of the hemolymph influence their cold hardiness potential. Warm acclimation led to a decrease in glycerol and proteins content in the hemolymph, which was associated with the decrease in ice nucleating activity and dramatic loss of cold hardiness potential of the caterpillars. It is suggested that one of the effects of cryoprotection in the freeze tolerant insects, caused by glycerol, might be associated with its ability to form larger aggregates of ice nucleating polypeptides that initiate the ice nucleation at high subzero temperatures. Such ice nucleating structures seem to ensure a high probability of ice nucleation at relatively high temperatures, which may contribute to the extraordinary cold hardiness of A. crataegi caterpillars, which may tolerate temperatures below -85 degree С.

  4. Deep supercooling xylem parenchyma cells of katsura tree (Cercidiphyllum japonicum) contain flavonol glycosides exhibiting high anti-ice nucleation activity.

    PubMed

    Kasuga, Jun; Hashidoko, Yasuyuki; Nishioka, Atsushi; Yoshiba, Megumi; Arakawa, Keita; Fujikawa, Seizo

    2008-09-01

    Xylem parenchyma cells (XPCs) of boreal hardwood species adapt to sub-freezing temperatures by deep supercooling to maintain a liquid state of intracellular water near -40 degrees C. Our previous study found that crude xylem extracts from such tree species exhibited anti-ice nucleation activity to promote supercooling of water. In the present study, thus, we attempted to identify the causative substances of supercooling. Crude xylem extracts from katsura tree (Cercidiphyllum japonicum), of which XPCs exhibited deep supercooling to -40 degrees C, were prepared by methanol extraction. The crude extracts were purified by liquid-liquid extraction and then by silica gel column chromatography. Although all the fractions obtained after each purification step exhibited some levels of anti-ice nucleation activity, only the most active fraction was retained to proceed to the subsequent level of purification. High-performance liquid chromatography (HPLC) analysis of a fraction with the highest level of activity revealed four peaks with high levels of anti-ice nucleation activity in the range of 2.8-9.0 degrees C. Ultraviolet (UV), mass and nuclear magnetic resonance (NMR) spectra revealed that these four peaks corresponded to quercetin-3-O-beta-glucoside (Q3G), kaempferol-7-O-beta-glucoside (K7G), 8-methoxykaempferol-3-O-beta-glucoside (8MK3G) and kaempferol-3-O-beta-glucoside (K3G). Microscopic observations confirmed the presence of flavonoids in cytoplasms of XPCs. These results suggest that diverse kinds of anti-ice nucleation substances, including flavonol glycosides, may have important roles in deep supercooling of XPCs.

  5. Measurements of BC-Containing Aerosol and Ice Nucleation Active Residuals in Colorado.

    NASA Astrophysics Data System (ADS)

    Katich, J. M.

    2015-12-01

    A recent ice nucleation (IN) chamber inter-comparison study (FIN-3) provided an opportunity to deploy two single particle soot photometers (SP2s) to the Stormpeak Laboratory in the mountains of Colorado in September of 2015. Aerosol was sampled from ambient air, as well as from behind both a coarse-mode aerosol concentrator and an ice nucleation chamber providing ice residuals. The SP2s characterized the size and mixing state of refractory black carbon-containing particles. Initial analyses of laboratory and ambient data collected over 3 weeks will be presented, with an emphasis on both coarse mode BC observations and BC contributions to ice residuals. The results will help constrain the role of BC from local and regional sources on heterogeneous ice nucleation.

  6. Spores of many common airborne fungi reveal no ice nucleation activity in oil immersion freezing experiments

    NASA Astrophysics Data System (ADS)

    Pummer, B. G.; Atanasova, L.; Bauer, H.; Bernardi, J.; Druzhinina, I. S.; Fröhlich-Nowoisky, J.; Grothe, H.

    2013-12-01

    Fungal spores are ubiquitous biological aerosols, which are considered to act as ice nuclei. In this study the ice nucleation (IN) activity of spores harvested from 29 fungal strains belonging to 21 different species was tested in the immersion freezing mode by microscopic observation of water-in-oil emulsions. Spores of 8 of these strains were also investigated in a microdroplet freezing array instrument. The focus was laid on species of economical, ecological or sanitary significance. Besides common molds (Ascomycota), some representatives of the widespread group of mushrooms (Basidiomycota) were also investigated. Fusarium avenaceum was the only sample showing IN activity at relatively high temperatures (about 264 K), while the other investigated fungal spores showed no freezing above 248 K. Many of the samples indeed froze at homogeneous ice nucleation temperatures (about 237 K). In combination with other studies, this suggests that only a limited number of species may act as atmospheric ice nuclei. This would be analogous to what is already known for the bacterial ice nuclei. Apart from that, we selected a set of fungal strains from different sites and exposed them to occasional freezing stress during their cultivation. This was in order to test if the exposure to a cold environment encourages the expression of ice nuclei during growth as a way of adaptation. Although the total protein expression was altered by this treatment, it had no significant impact on the IN activity.

  7. Characterization of the ice nucleation activity of an airborne Penicillium species

    NASA Astrophysics Data System (ADS)

    Yordanova, Petya; Hill, Thomas C. J.; Pummer, Bernhard G.; Franc, Gary D.; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

    2016-04-01

    Microorganisms are ubiquitous both on and above the Earth. Several bacterial and fungal spe-cies are the focus of atmospheric studies due to their ability to trigger ice formation at high subzero temperatures. Thus, they have potential to modify cloud albedo, lifetime and precipita-tion, and ultimately the hydrological cycle. Several fungal strains have already been identified as possessing ice nucleation (IN) activity, and recent studies have shown that IN active fungi are present in the cultivable community of air and soil samples [1, 2]. However, the abundance, diversity, and sources of fungal ice nuclei in the atmosphere are still poorly characterized. In this study, fungal colonies obtained from air samples were screened for IN activity in the droplet-freezing assay described in Fröhlich-Nowoisky et al., 2015 [2]. Out of 128 tested iso-lates, two were found to catalyze ice formation at temperatures up to -4°C. By DNA analysis, both isolates were classified as Penicillium spp. The freezing activity of both was further char-acterized after different filtration, heat, and enzymatic treatments in the temperature range from -4°C to -15°C. Preliminary results show that a proteinaceous compound is responsible for the IN activity. Furthermore, ongoing experiments indicate that the activity is associated only with the hyphae. [1] Huffman, et al. (2013): Atmos. Chem. Phys., 13, 6151-6164. [2] Fröhlich-Nowoisky et al. (2015): Biogeosciences, 12: 1057-1071.

  8. Cloud condensation nuclei and ice nucleation activity of hydrophobic and hydrophilic soot particles.

    PubMed

    Koehler, Kirsten A; DeMott, Paul J; Kreidenweis, Sonia M; Popovicheva, Olga B; Petters, Markus D; Carrico, Christian M; Kireeva, Elena D; Khokhlova, Tatiana D; Shonija, Natalia K

    2009-09-28

    Cloud condensation nuclei (CCN) activity and ice nucleation behavior (for temperaturesice nucleation experiments below -40 degrees C, AEC particles nucleated ice near the expected condition for homogeneous freezing of water from aqueous solutions. In

  9. Comments on 'Rocket effluent - Its ice nucleation activity and related properties'

    NASA Technical Reports Server (NTRS)

    Hindman, E. E., II; Lala, G. G.

    1980-01-01

    Parungo and Allee (1978) reported ice nucleus (IN) measurements made from an aircraft in stabilized ground clouds from Titan III launches at KSC. They concluded from the measurements that the SGC contained IN. After an examination of the data the present authors (Hindman and Lala) argue that the filter devices were unable to detect IN in the SGC. In a reply Parungo and Allee attempt to refute this conclusion.

  10. Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

    DOE PAGES

    DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; ...

    2015-01-13

    Data from both laboratory studies and atmospheric measurements are used to develop an empirical parameterization for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RHw) are taken as a measure of the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterizationmore » developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A calibration factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RHw of 105% vs. maximum fractions active at higher RHw. Instrumental factors that affect activation behavior vs. RHw in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this calibration factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization, including calibration

  11. Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

    DOE PAGES

    DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; ...

    2014-06-27

    Data from both laboratory studies and atmospheric measurements are used to develop a simple parametric description for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RHw) are taken to approximate the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterization developedmore » follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A correction factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RHw of 105% vs. maximum fractions active at higher RHw. Instrumental factors that affect activation behavior vs. RHw in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this correction factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization to the immersion

  12. Components of ice nucleation structures of bacteria.

    PubMed Central

    Turner, M A; Arellano, F; Kozloff, L M

    1991-01-01

    Nonprotein components attached to the known protein product of the inaZ gene of Pseudomonas syringae have been identified and shown to be necessary for the most efficient ice nucleation of supercooled H2O. Previous studies have shown that cultures of Ina+ bacteria have cells with three major classes of ice-nucleating structures with readily differentiated activities. Further, some cells in the culture have nucleating activities intermediate between those of the different classes and presumably have structures that are biosynthetic intermediates between those of the different classes. Since these structures cannot be readily isolated and analyzed, their components have been identified by the use of specific enzymes or chemical probes, by direct incorporation of labeled precursors, and by stimulation of the formation of specific classes of freezing structures by selective additions to the growth medium. From these preliminary studies it appears that the most active ice nucleation structure (class A) contains the ice nucleation protein linked to phosphatidylinositol and mannose, probably as a complex mannan, and possibly glucosamine. These nonprotein components are characteristic of those used to anchor external proteins to cell membranes of eucaryotic cells and suggest that a similar but not identical anchoring mechanism is required for efficient ice nucleation structure. The class B structure has been found to contain protein presumably linked to the mannan and glucosamine moieties but definitely not to the phosphatidylinositol. The class C structure, which has the poorest ice nucleation activity, appears to be the ice nucleation protein linked to a few mannose residues and to be partially imbedded in the outer cell membrane. Images FIG. 1 FIG. 2 FIG. 5 FIG. 9 FIG. 15 FIG. 16 PMID:1917876

  13. Spores of most common airborne fungi reveal no ice nucleation activity

    NASA Astrophysics Data System (ADS)

    Pummer, B. G.; Atanasova, L.; Bauer, H.; Bernardi, J.; Druzhinina, I. S.; Grothe, H.

    2013-06-01

    Fungal spores are ubiquitous biological aerosols, which are considered to show ice nucleation (IN) activity. In this study the respective IN activity was tested in oil emulsion in the immersion freezing mode. The focus was laid on species of economical, ecological or sanitary significance. For the first time, not only common moulds, but also edible mushrooms (Basidiomycota, Agaricomycetes) were investigated, as they contribute massively to the total amount of fungal spores in the atmosphere. Only Fusarium avenaceum showed freezing events at low subzero-temperatures, while the other investigated fungal spores showed no significant IN activity. Furthermore, we selected a set of fungal strains from different sites and exposed them to occasional freezing stress during cultivation. Although the total protein expression was altered by this treatment, it had no significant impact on the IN activity.

  14. Study on the ice nucleation activity of fungal spores (Ascomycota and Basidiomycota)

    NASA Astrophysics Data System (ADS)

    Pummer, B. G.; Atanasova, L.; Bauer, H.; Bernardi, J.; Druzhinina, I. S.; Grothe, H.

    2012-04-01

    Biogenic ice nucleation (IN) in the atmosphere is a topic of growing interest, as, according to IPCC, the impact of IN on global climate is crucial to perform reliable climate model calculations. About 20 years ago IN activity of a few lichen and Fusarium species [1,2] was reported, while all other investigated fungi were IN-negative. However, as the fungal kingdom is vast, many abundant species, especially the Basidiomycota (most mushrooms), were not tested before. Furthermore, the focus of the past studies was on the IN activity of the mycelium as a cryoprotective mechanism, and not on the airborne spores. We carried out oil immersion measurements [3] with spores from 17 different fungal species of ecological, economical or sanitary importance. Most of these species have not been investigated before, like exponents of Aspergillus, Trichoderma and Agaricales (most mushrooms). Apart from F. avenaceum, spores of all measured species showed moderate or no IN activity, supporting the hypothesis that significant IN activity is a rather exclusive property of only a few species within the fungal kingdom. [1] Kieft TL and Ruscetti T: J. Bacteriol. 172, 3519-3523, 1990. [2] Pouleur S et al.: Appl. Environ. Microbiol., 58, 2960-2964, 1992. [3] Marcolli C et al.: Atmos. Chem. Phys. 7, 5081-5091, 2007.

  15. Immersion freezing of supermicron mineral dust particles: freezing results, testing different schemes for describing ice nucleation, and ice nucleation active site densities.

    PubMed

    Wheeler, M J; Mason, R H; Steunenberg, K; Wagstaff, M; Chou, C; Bertram, A K

    2015-05-14

    Ice nucleation on mineral dust particles is known to be an important process in the atmosphere. To accurately implement ice nucleation on mineral dust particles in atmospheric simulations, a suitable theory or scheme is desirable to describe laboratory freezing data in atmospheric models. In the following, we investigated ice nucleation by supermicron mineral dust particles [kaolinite and Arizona Test Dust (ATD)] in the immersion mode. The median freezing temperature for ATD was measured to be approximately -30 °C compared with approximately -36 °C for kaolinite. The freezing results were then used to test four different schemes previously used to describe ice nucleation in atmospheric models. In terms of ability to fit the data (quantified by calculating the reduced chi-squared values), the following order was found for ATD (from best to worst): active site, pdf-α, deterministic, single-α. For kaolinite, the following order was found (from best to worst): active site, deterministic, pdf-α, single-α. The variation in the predicted median freezing temperature per decade change in the cooling rate for each of the schemes was also compared with experimental results from other studies. The deterministic model predicts the median freezing temperature to be independent of cooling rate, while experimental results show a weak dependence on cooling rate. The single-α, pdf-α, and active site schemes all agree with the experimental results within roughly a factor of 2. On the basis of our results and previous results where different schemes were tested, the active site scheme is recommended for describing the freezing of ATD and kaolinite particles. We also used our ice nucleation results to determine the ice nucleation active site (INAS) density for the supermicron dust particles tested. Using the data, we show that the INAS densities of supermicron kaolinite and ATD particles studied here are smaller than the INAS densities of submicron kaolinite and ATD particles

  16. Ice nucleation activity of diesel soot particles at cirrus relevant temperature conditions: Effects of hydration, secondary organics coating, soot morphology, and coagulation

    NASA Astrophysics Data System (ADS)

    Kulkarni, Gourihar; China, Swarup; Liu, Shang; Nandasiri, Manjula; Sharma, Noopur; Wilson, Jacqueline; Aiken, Allison C.; Chand, Duli; Laskin, Alexander; Mazzoleni, Claudio; Pekour, Mikhail; Shilling, John; Shutthanandan, Vaithiyalingam; Zelenyuk, Alla; Zaveri, Rahul A.

    2016-04-01

    Ice formation by diesel soot particles was investigated at temperatures ranging from -40 to -50°C. Size-selected soot particles were physically and chemically aged in an environmental chamber, and their ice nucleating properties were determined using a continuous flow diffusion type ice nucleation chamber. Bare (freshly formed), hydrated, and compacted soot particles, as well as α-pinene secondary organic aerosol (SOA)-coated soot particles at high relative humidity conditions, showed ice formation activity at subsaturation conditions with respect to water but below the homogeneous freezing threshold conditions. However, SOA-coated soot particles at dry conditions were observed to freeze at homogeneous freezing threshold conditions. Overall, our results suggest that heterogeneous ice nucleation activity of freshly emitted diesel soot particles are sensitive to some of the aging processes that soot can undergo in the atmosphere.

  17. High ice nucleation activity located in blueberry stem bark is linked to primary freeze initiation and adaptive freezing behaviour of the bark.

    PubMed

    Kishimoto, Tadashi; Yamazaki, Hideyuki; Saruwatari, Atsushi; Murakawa, Hiroki; Sekozawa, Yoshihiko; Kuchitsu, Kazuyuki; Price, William S; Ishikawa, Masaya

    2014-07-31

    Controlled ice nucleation is an important mechanism in cold-hardy plant tissues for avoiding excessive supercooling of the protoplasm, for inducing extracellular freezing and/or for accommodating ice crystals in specific tissues. To understand its nature, it is necessary to characterize the ice nucleation activity (INA), defined as the ability of a tissue to induce heterogeneous ice nucleation. Few studies have addressed the precise localization of INA in wintering plant tissues in respect of its function. For this purpose, we recently revised a test tube INA assay and examined INA in various tissues of over 600 species. Extremely high levels of INA (-1 to -4 °C) in two wintering blueberry cultivars of contrasting freezing tolerance were found. Their INA was much greater than in other cold-hardy species and was found to be evenly distributed along the stems of the current year's growth. Concentrations of active ice nuclei in the stem were estimated from quantitative analyses. Stem INA was localized mainly in the bark while the xylem and pith had much lower INA. Bark INA was located mostly in the cell wall fraction (cell walls and intercellular structural components). Intracellular fractions had much less INA. Some cultivar differences were identified. The results corresponded closely with the intrinsic freezing behaviour (extracellular freezing) of the bark, icicle accumulation in the bark and initial ice nucleation in the stem under dry surface conditions. Stem INA was resistant to various antimicrobial treatments. These properties and specific localization imply that high INA in blueberry stems is of intrinsic origin and contributes to the spontaneous initiation of freezing in extracellular spaces of the bark by acting as a subfreezing temperature sensor. Published by Oxford University Press on behalf of the Annals of Botany Company.

  18. High ice nucleation activity located in blueberry stem bark is linked to primary freeze initiation and adaptive freezing behaviour of the bark

    PubMed Central

    Kishimoto, Tadashi; Yamazaki, Hideyuki; Saruwatari, Atsushi; Murakawa, Hiroki; Sekozawa, Yoshihiko; Kuchitsu, Kazuyuki; Price, William S.; Ishikawa, Masaya

    2014-01-01

    Controlled ice nucleation is an important mechanism in cold-hardy plant tissues for avoiding excessive supercooling of the protoplasm, for inducing extracellular freezing and/or for accommodating ice crystals in specific tissues. To understand its nature, it is necessary to characterize the ice nucleation activity (INA), defined as the ability of a tissue to induce heterogeneous ice nucleation. Few studies have addressed the precise localization of INA in wintering plant tissues in respect of its function. For this purpose, we recently revised a test tube INA assay and examined INA in various tissues of over 600 species. Extremely high levels of INA (−1 to −4 °C) in two wintering blueberry cultivars of contrasting freezing tolerance were found. Their INA was much greater than in other cold-hardy species and was found to be evenly distributed along the stems of the current year's growth. Concentrations of active ice nuclei in the stem were estimated from quantitative analyses. Stem INA was localized mainly in the bark while the xylem and pith had much lower INA. Bark INA was located mostly in the cell wall fraction (cell walls and intercellular structural components). Intracellular fractions had much less INA. Some cultivar differences were identified. The results corresponded closely with the intrinsic freezing behaviour (extracellular freezing) of the bark, icicle accumulation in the bark and initial ice nucleation in the stem under dry surface conditions. Stem INA was resistant to various antimicrobial treatments. These properties and specific localization imply that high INA in blueberry stems is of intrinsic origin and contributes to the spontaneous initiation of freezing in extracellular spaces of the bark by acting as a subfreezing temperature sensor. PMID:25082142

  19. Agar plate freezing assay for the in situ selection of transformed ice nucleating bacteria.

    PubMed

    Anastassopoulos, Elias

    2006-10-01

    An agar plate freezing assay is described based on the incorporation of fluorescein dye in agar medium. Upon addition of fluorescein the medium becomes transparent. This facilitates the monitoring of the ice nucleation event in vivo and the subsequent in situ selection of transformed ice nucleating bacteria. In comparison with known assays for the screening of transformants, the proposed assay is very accurate and reproducible. It may be applied in environmental samples screening for ice nucleating organisms, or in cDNA or genomic libraries for identifying novel ice nucleation genes. It may also prove useful in comparative studies of the ice nucleation activity, e.g. in directed evolution experiments involving ice nucleation genes.

  20. High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments

    NASA Astrophysics Data System (ADS)

    Junge, K.; Swanson, B. D.

    2008-05-01

    Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for ice formation in Arctic clouds (Bigg and Leck, 2001), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium - which for artificial seawater was -42.2±0.3°C. Our results suggest that immersion freezing of these marine psychro-active bacteria and viruses would not be important for heterogeneous ice nucleation processes in polar clouds or to the formation of sea ice. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater.

  1. High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments

    NASA Astrophysics Data System (ADS)

    Junge, K.; Swanson, B. D.

    2007-11-01

    Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for cloud formation in the Arctic (Bigg and Leck, 2001), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium - which for artificial seawater was -42.2±0.3°C. Our results indicated that these marine psychro-active bacteria and viruses are not important for heterogeneous ice nucleation processes in sea ice or polar clouds. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater.

  2. High-Resolution ice Nucleation Spectra of Sea-Ice Bacteria: Implications for Cloud Formation and Life in Frozen Environments

    NASA Astrophysics Data System (ADS)

    Junge, K.; Swanson, B.

    2007-12-01

    Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for cloud formation in the Arctic (Bigg and Leck, 2002), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium -- which for artificial seawater was - 42.2 degC (standdev. 0.3 degC). Our results indicated that these marine psychro-active bacteria and viruses are not important for heterogeneous ice nucleation processes in sea ice or polar clouds. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater (Junge et al., 2006).

  3. Ice nucleation activity of diesel soot particles at Cirrus relevant conditions: Effects of hydration, secondary organics coating, hydration, soot morphology, and coagulation

    SciTech Connect

    Kulkarni, Gourihar R.; China, Swarup; Liu, Shang; Nandasiri, Manjula I.; Sharma, Noopur; Wilson, Jacqueline M.; Aiken, A. C.; Chand, Duli; Laskin, Alexander; Mazzoleni, Claudio; Pekour, Mikhail S.; Shilling, John E.; Shutthanandan, V.; Zelenyuk, Alla; Zaveri, Rahul A.

    2016-04-16

    The role of atmospheric relevant soot particles that are processed in the atmosphere toward ice nucleation at cirrus cloud condition is poorly understood. In this study, the ice nucleating properties of diesel soot particles subjected to various physical and chemical aging treatments were investigated at temperatures ranging from -40 to -50 °C. We show that bare soot particles nucleate ice in deposition mode, but coating with secondary organics suppresses the heterogeneous ice nucleation potential of soot particles requiring homogeneous freezing threshold conditions. However, the ice nucleation efficiency of soot particles coated with an aqueous organic layer was similar to bare soot particles. Hydration of bare soot particles slightly enhanced the ice nucleation efficiency, and the IN abilities of compact soot particles (roundness = ~ 0.6) were similar to bare lacey soot particles (roundness = ~ 0.4). These results indicate that ice nucleation properties are sensitive to the various aging treatments.

  4. Characterization of ice-nucleating bacteria using on-line electron impact ionization aerosol mass spectrometry.

    PubMed

    Wolf, R; Slowik, J G; Schaupp, C; Amato, P; Saathoff, H; Möhler, O; Prévôt, A S H; Baltensperger, U

    2015-04-01

    The mass spectral signatures of airborne bacteria were measured and analyzed in cloud simulation experiments at the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) facility. Suspensions of cultured cells in pure water were sprayed into the aerosol and cloud chambers forming an aerosol which consisted of intact cells, cell fragments and residual particles from the agar medium in which the bacteria were cultured. The aerosol particles were analyzed with a high-resolution time-of-flight aerosol mass spectrometer equipped with a newly developed PM2.5 aerodynamic lens. Positive matrix factorization (PMF) using the multilinear engine (ME-2) source apportionment was applied to deconvolve the bacteria and agar mass spectral signatures. The bacteria mass fraction contributed between 75 and 95% depending on the aerosol generation, with the remaining mass attributed to agar. We present mass spectra of Pseudomonas syringae and Pseudomonas fluorescens bacteria typical for ice-nucleation active bacteria in the atmosphere to facilitate the distinction of airborne bacteria from other constituents in ambient aerosol, e.g. by PMF/ME-2 source apportionment analyses. Nitrogen-containing ions were the most salient feature of the bacteria mass spectra, and a combination of C4 H8 N(+) (m/z 70) and C5 H12 N(+) (m/z 86) may be used as marker ions.

  5. Ice-active characteristics of soil bacteria selected by ice-affinity.

    PubMed

    Wilson, Sandra L; Kelley, Deborah L; Walker, Virginia K

    2006-10-01

    As an initial screen for microorganisms that produce ice-active macromolecules, ice-affinity was used to select microorganisms from soil consortia originating from three temperate regions. Once selected and subsequently purified to single colonies, these microbes were putatively identified by 16S ribosomal RNA sequencing and assayed for various ice-active properties. Ice-affinity selection appeared to select for bacteria with ice-associating activities: inhibition of ice recrystallization; ice nucleation; ice shaping. Although none of these activities were observed in Paenibacillus amyloliticus C8, others such as Chryseobacterium sp. GL8, demonstrated both ice recrystallization inhibition and ice-shaping activities. Pseudomonas borealis DL7 was classified as a type I ice nucleator, Flavobacterium sp. GL7, was identified as a type III ice nucleator and Acinetobacter radioresistens DL5 demonstrated ice recrystallization inhibition. In all, 19 different culturable bacteria were selected from the thousands of microbes in late-summer collected soil samples. Many of the selected microbes have been previously reported in glacial ice cores or polar sea ice, and of five isolates that were further characterized, four showed ice-associating activities. These results indicate the significant potential of ice-affinity selection even with temperate climate soils, suggesting that sampling in more extreme and remote areas is not required for the isolation of ice-active bacteria.

  6. Bacteria beneath the West Antarctic ice sheet.

    PubMed

    Lanoil, Brian; Skidmore, Mark; Priscu, John C; Han, Sukkyun; Foo, Wilson; Vogel, Stefan W; Tulaczyk, Slawek; Engelhardt, Hermann

    2009-03-01

    Subglacial environments, particularly those that lie beneath polar ice sheets, are beginning to be recognized as an important part of Earth's biosphere. However, except for indirect indications of microbial assemblages in subglacial Lake Vostok, Antarctica, no sub-ice sheet environments have been shown to support microbial ecosystems. Here we report 16S rRNA gene and isolate diversity in sediments collected from beneath the Kamb Ice Stream, West Antarctic Ice Sheet and stored for 15 months at 4 degrees C. This is the first report of microbes in samples from the sediment environment beneath the Antarctic Ice Sheet. The cells were abundant ( approximately 10(7) cells g(-1)) but displayed low diversity (only five phylotypes), likely as a result of enrichment during storage. Isolates were cold tolerant and the 16S rRNA gene diversity was a simplified version of that found in subglacial alpine and Arctic sediments and water. Although in situ cell abundance and the extent of wet sediments beneath the Antarctic ice sheet can only be roughly extrapolated on the basis of this sample, it is clear that the subglacial ecosystem contains a significant and previously unrecognized pool of microbial cells and associated organic carbon that could potentially have significant implications for global geochemical processes.

  7. Putting life on ice: bacteria that bind to frozen water.

    PubMed

    Bar Dolev, Maya; Bernheim, Reut; Guo, Shuaiqi; Davies, Peter L; Braslavsky, Ido

    2016-08-01

    Ice-binding proteins (IBPs) are typically small, soluble proteins produced by cold-adapted organisms to help them avoid ice damage by either resisting or tolerating freezing. By contrast, the IBP of the Antarctic bacterium Marinomonas primoryensis is an extremely long, 1.5 MDa protein consisting of five different regions. The fourth region, a 34 kDa domain, is the only part that confers ice binding. Bioinformatic studies suggest that this IBP serves as an adhesin that attaches the bacteria to ice to keep it near the top of the water column, where oxygen and nutrients are available. Using temperature-controlled cells and a microfluidic apparatus, we show that M. primoryensis adheres to ice and is only released when melting occurs. Binding is dependent on the mobility of the bacterium and the functionality of the IBP domain. A polyclonal antibody raised against the IBP region blocks bacterial ice adhesion. This concept may be the basis for blocking biofilm formation in other bacteria, including pathogens. Currently, this IBP is the only known example of an adhesin that has evolved to bind ice. © 2016 The Authors.

  8. Putting life on ice: bacteria that bind to frozen water

    PubMed Central

    Bernheim, Reut; Guo, Shuaiqi; Davies, Peter L.; Braslavsky, Ido

    2016-01-01

    Ice-binding proteins (IBPs) are typically small, soluble proteins produced by cold-adapted organisms to help them avoid ice damage by either resisting or tolerating freezing. By contrast, the IBP of the Antarctic bacterium Marinomonas primoryensis is an extremely long, 1.5 MDa protein consisting of five different regions. The fourth region, a 34 kDa domain, is the only part that confers ice binding. Bioinformatic studies suggest that this IBP serves as an adhesin that attaches the bacteria to ice to keep it near the top of the water column, where oxygen and nutrients are available. Using temperature-controlled cells and a microfluidic apparatus, we show that M. primoryensis adheres to ice and is only released when melting occurs. Binding is dependent on the mobility of the bacterium and the functionality of the IBP domain. A polyclonal antibody raised against the IBP region blocks bacterial ice adhesion. This concept may be the basis for blocking biofilm formation in other bacteria, including pathogens. Currently, this IBP is the only known example of an adhesin that has evolved to bind ice. PMID:27534698

  9. Activity of different proteinaceous ice nucleating particles

    NASA Astrophysics Data System (ADS)

    Hartmann, Susann; Augustin-Bauditz, Stefanie; Grawe, Sarah; Ling, Meilee; Hellner, Lisa; Zapf, Jean-Michel; Šantl-Temkiv, Tina; Pummer, Bernhard; Boesen, Thomas; Wex, Heike; Finster, Kai; Stratmann, Frank

    2017-04-01

    A variety of microorganisms (bacteria, fungi, lichen) from land produce protein structures, which act as a template for ice nucleation [1]. Also marine sources of ice nucleating particles (INPs) came in focus in the recent years. The atmospheric spatio-temporal distribution of INPs from microorganisms is still not well known. However, it is often assumed that the observed onset of atmospheric ice nucleation (T>-20°C) is due to the existence of ice-nucleation active biological particles. In this study we compare the ice nucleation activity of different proteinaceous particles produced by bacteria and fungi. For bacteria we investigate (i) cells and fragments of Pseudomonas syringae from commercially available SnomaxTM and (ii) the Pseudomonas syringae INA protein expressed in living Escherichia coli bacteria. We also analyzed freeze-dried leaves [2] where we assume that proteinaceous particles are responsible for the ice nucleation activity. For fungi the widespread soil fungus Mortierella alpina was investigated which had been extracted from natural soil [3]. Immersion freezing experiments are performed at the cold stage LINA (Leipzig Ice Nucleation Array). We attempt to describe the activity of a single proteinaceous ice nucleating particle [4] in order to achieve direct comparability. Further, the results are compared with complex natural systems e.g. soil dust. The objectives of this study are to clarify potential differences in the ice nucleation potential of proteinaceous particles and to draw conclusions concerning the need to differentiate them for modelling purposes. 1. Szyrmer, W. and I. Zawadzki, Biogenic and anthropogenic sources of ice-forming nuclei: A review, Bull. Amer. Meteorol. Soc., 1997. 2. Schnell, R.C. and G. Vali, Biogenic ice nucleai .1: Terrestrial and marine sources, doi: 10.1175/1520-0469(1976)033<1554:binpit>2.0.co;2, 1976. 3. Froehlich-Nowoisky, J. et al., Ice nucleation activity in the widespread soil fungus Mortierella alpina, doi: 10

  10. Phylogenetic analysis of bacteria preserved in a permafrost ice wedge for 25,000 years.

    PubMed

    Katayama, Taiki; Tanaka, Michiko; Moriizumi, Jun; Nakamura, Toshio; Brouchkov, Anatoli; Douglas, Thomas A; Fukuda, Masami; Tomita, Fusao; Asano, Kozo

    2007-04-01

    Phylogenetic analysis of bacteria preserved within an ice wedge from the Fox permafrost tunnel was undertaken by cultivation and molecular techniques. The radiocarbon age of the ice wedge was determined. Our results suggest that the bacteria in the ice wedge adapted to the frozen conditions have survived for 25,000 years.

  11. Inhibition of bacterial ice nucleators by fish antifreeze glycoproteins.

    PubMed

    Parody-Morreale, A; Murphy, K P; Di Cera, E; Fall, R; DeVries, A L; Gill, S J

    1988-06-23

    Certain bacteria promote the formation of ice in super-cooled water by means of ice nucleators which contain a unique protein associated with the cell membrane. Ice nucleators in general are believed to act by mimicking the structure of an ice crystal surface, thus imposing an ice-like arrangement on the water molecules in contact with the nucleating surface and lowering the energy necessary for the initiation of ice formation. Quantitative investigation of the bacterial ice-nucleating process has recently been made possible by the discovery of certain bacteria that shed stable membrane vesicles with ice nucleating activity. The opposite effect, inhibition of ice formation, has been described for a group of glycoproteins found in different fish and insect species. This group of substances, termed antifreeze glycoproteins (AFGPs), promotes the supercooling of water with no appreciable effect on the equilibrium freezing point or melting temperature. Substantial evidence now indicates that AFGPs act by binding to a growing ice crystal and slowing crystal growth. As the ice-nucleating protein surface is believed to have a structure similar to an embryonic ice crystal, AFGPs might be predicted to interact directly with a bacterial ice-nucleating site. We report here that AFGPs from the antarctic fish Dissostichus mawsoni inhibit the ice-nucleating activity of membrane vesicles from the bacterium Erwinia herbicola. The inhibition effect shows saturation at high concentration of AFGP and conforms to a simple binding reaction between the AFGP and the nucleation centre.

  12. Bioprospecting glacial ice for plant growth promoting bacteria.

    PubMed

    Balcazar, Wilvis; Rondón, Johnma; Rengifo, Marcos; Ball, María M; Melfo, Alejandra; Gómez, Wileidy; Yarzábal, Luis Andrés

    2015-08-01

    Glaciers harbor a wide diversity of microorganisms, metabolically versatile, highly tolerant to multiple environmental stresses and potentially useful for biotechnological purposes. Among these, we hypothesized the presence of bacteria able to exhibit well-known plant growth promoting traits (PGP). These kinds of bacteria have been employed for the development of commercial biofertilizers; unfortunately, these biotechnological products have proven ineffective in colder climates, like the ones prevailing in mountainous ecosystems. In the present work, we prospected glacial ice collected from two small tropical glaciers, located above 4.900 m in the Venezuelan Andes, for cold-active PGP bacteria. The initial screening strategy allowed us to detect the best inorganic-P solubilizers at low temperatures, from a sub-sample of 50 bacterial isolates. Solubilization of tricalcium phosphate, aluminum- and iron-phosphate, occurred in liquid cultures at low temperatures and was dependent on medium acidification by gluconic acid production, when bacteria were supplied with an appropriate source of carbon. Besides, the isolates were psychrophilic and in some cases exhibited a broad range of growth-temperatures, from 4 °C to 30 °C. Additional PGP abilities, including phytohormone- and HCN production, siderophore excretion and inhibition of phytopathogens, were confirmed in vitro. Nucleotidic sequence analysis of 16S rRNA genes allowed us to place the isolates within the Pseudomonas genus. Our results support the possible use of these strains to develop cold-active biofertilizers to be used in mountainous agriculture.

  13. Modeling immersion freezing with aerosol-dependent prognostic ice nuclei in Arctic mixed-phase clouds

    NASA Astrophysics Data System (ADS)

    Paukert, M.; Hoose, C.

    2014-07-01

    While recent laboratory experiments have thoroughly quantified the ice nucleation efficiency of different aerosol species, the resulting ice nucleation parameterizations have not yet been extensively evaluated in models on different scales. Here the implementation of an immersion freezing parameterization based on laboratory measurements of the ice nucleation active surface site density of mineral dust and ice nucleation active bacteria, accounting for nucleation scavenging of ice nuclei, into a cloud-resolving model with two-moment cloud microphysics is presented. We simulated an Arctic mixed-phase stratocumulus cloud observed during Flight 31 of the Indirect and Semi-Direct Aerosol Campaign near Barrow, Alaska. Through different feedback cycles, the persistence of the cloud strongly depends on the ice number concentration. It is attempted to bring the observed cloud properties, assumptions on aerosol concentration, and composition and ice formation parameterized as a function of these aerosol properties into agreement. Depending on the aerosol concentration and on the ice crystal properties, the simulated clouds are classified as growing, dissipating, and quasi-stable. In comparison to the default ice nucleation scheme, the new scheme requires higher aerosol concentrations to maintain a quasi-stable cloud. The simulations suggest that in the temperature range of this specific case, mineral dust can only contribute to a minor part of the ice formation. The importance of ice nucleation active bacteria and possibly other ice formation modes than immersion freezing remains poorly constrained in the considered case, since knowledge on local variations in the emissions of ice nucleation active organic aerosols in the Arctic is scarce.

  14. Ice nucleation properties of agricultural soil dusts

    NASA Astrophysics Data System (ADS)

    Steinke, Isabelle; Funk, Roger; Busse, Jacqueline; Iturri, Antonela; Kirchen, Silke; Leue, Martin; Möhler, Ottmar; Schwartz, Thomas; Sierau, Berko; Toprak, Emre; Ulrich, Andreas; Hoose, Corinna; Leisner, Thomas

    2015-04-01

    Soil dust particles emitted from agricultural areas contain large amounts of organic material such as fungi, bacteria and plant debris. Being carrier for potentially highly ice-active biological particles, agricultural soil dusts are candidates for being very ice-active as well. In this work, we present ice nucleation experiments conducted in the AIDA cloud chamber. We investigated the ice nucleation efficiency of four types of soil dust from different regions of the world. Results are presented for the immersion freezing and the deposition nucleation mode: all soil dusts show higher ice nucleation efficiencies than desert dusts, especially at temperatures above 254 K. For one soil dust sample, the effect of heat treatments was investigated. Heat treatments did not affect the ice nucleation efficiency which presumably excludes primary biological particles as the only source of the increased ice nucleation efficiency. Therefore, organo-mineral complexes or organic compounds may contribute substantially to the high ice nucleation activity of agricultural soil dusts.

  15. Magnesium enriched lactic acid bacteria as a carrier for probiotic ice cream production.

    PubMed

    Góral, Małgorzata; Kozłowicz, Katarzyna; Pankiewicz, Urszula; Góral, Dariusz

    2018-01-15

    The following strains of bacteria: Lactobacillus rhamnosus B 442, Lactobacillus rhamnosus 1937, and Lactococcus lactis JBB 500 were enriched with magnesium ions using Pulsed Electric Fields. The potentially probiotic strains were added to the mixture in the DVS process and applied for the production of ice cream which were then analyzed physicochemically and microbiologically. Results showed that addition of bacteria enriched with magnesium did not change chemical parameters of the ice cream and did not affect the freezing process, meltability, and hardness. No significant differences were noted in colour of the samples. The ice cream with addition of bacteria enriched with magnesium had higher adhesiveness. The results of viability determination showed that the total number of microorganisms in the ice cream was higher than in the starter cultures. Viability of the bacteria enriched with magnesium in the obtained ice cream was lower in comparison to the control samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Diatom assemblages promote ice formation in large lakes.

    PubMed

    D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

    2013-08-01

    We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (T(c)) as high as -3 °C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world.

  17. Diatom assemblages promote ice formation in large lakes

    PubMed Central

    D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

    2013-01-01

    We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (Tc) as high as −3 °C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world. PMID:23552624

  18. Modeling studying on ice formation by bacteria in warm-based convective cloud

    NASA Astrophysics Data System (ADS)

    Sun, J.

    2005-12-01

    Bacteria have been recognized as cloud condensation nuclei (CCN), and certain bacteria, commonly found in plants, have exhibited capacity to act as ice nuclei (IN) at temperatures as warm as -2 °C. These ice nucleating bacteria are readily disseminated into the atmosphere and have been observed in clouds at altitudes of several kilometres. It is noteworthy that over 20 years ago, one assumed the possibility of bacterial transport and their importance into cloud formation process, rain and precipitation, as well as causing disease in plants and animal kingdom. We used a 1-D cumulus cloud model with the CCOPE 19th July 1981 case and the observed field profile of bacterial concentration, to simulate the significance of bacteria as IN through condensation freezing mechanism. In this paper, we will present our results on the role of bacteria as active ice nuclei in the developing stage of cumulus clouds, and their potential significance in atmospheric sciences.

  19. Phylogenetic Analysis of Bacteria Preserved in a Permafrost Ice Wedge for 25,000 Years▿†

    PubMed Central

    Katayama, Taiki; Tanaka, Michiko; Moriizumi, Jun; Nakamura, Toshio; Brouchkov, Anatoli; Douglas, Thomas A.; Fukuda, Masami; Tomita, Fusao; Asano, Kozo

    2007-01-01

    Phylogenetic analysis of bacteria preserved within an ice wedge from the Fox permafrost tunnel was undertaken by cultivation and molecular techniques. The radiocarbon age of the ice wedge was determined. Our results suggest that the bacteria in the ice wedge adapted to the frozen conditions have survived for 25,000 years. PMID:17293514

  20. Enteric bacteria of food ice and their survival in alcoholic beverages and soft drinks.

    PubMed

    Gaglio, Raimondo; Francesca, Nicola; Di Gerlando, Rosalia; Mahony, Jennifer; De Martino, Simone; Stucchi, Carlo; Moschetti, Giancarlo; Settanni, Luca

    2017-10-01

    This study aimed to evaluate the levels of enteric bacteria in ice cubes produced in different environments (home-made, prepared in bars and pubs with ice machines and produced in industrial plants) and to determine their survival in different alcoholic beverages and soft drinks. Members of the Enterobacteriaceae family were found in almost all samples analysed. All industrial and the majority of home-made samples did not contain coliforms. Enterococci were not identified in domestic samples while they were detected in two industrial and three bar/pub samples. The samples collected from bars and pubs were characterized by the highest levels of enteric bacteria. Fourteen strains representing 11 species of eight bacterial genera were identified, some of which are known agents of human infections. The most numerous groups included Enterococcus and Stenotrophomonas. The survival of Enterococcus faecium ICE41, Pantoea conspicua ICE80 and Stenotrophomonas maltophilia ICE272, that were detected at the highest levels (100-400 CFU/100 mL thawed ice) in the ice cubes, was tested in six drinks and beverages characterized by different levels of alcohol, CO2, pH and the presence of antibacterial ingredients. The results showed a species-specific behaviour and, in general, a reduction of the microbiological risks associated with ice after its transfer to alcoholic or carbonated beverages. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Freshwater ice as habitat: partitioning of phytoplankton and bacteria between ice and water in central European reservoirs.

    PubMed

    McKay, Robert M L; Prášil, Ondrej; Pechar, Libor; Lawrenz, Evelyn; Rozmarynowycz, Mark J; Bullerjahn, George S

    2015-12-01

    Abundant phytoplankton and bacteria were identified by high-throughput 16S rRNA tag Illumina sequencing of samples from water and ice phases collected during winter at commercial fish ponds and a sand pit lake within the UNESCO Třeboň Basin Biosphere Reserve, Czech Republic. Bacterial reads were dominated by Proteobacteria and Bacteroidetes. Despite dominance by members of just two phyla, UniFrac principal coordinates analysis of the bacterial community separated the water community of Klec fish pond, as well as the ice-associated community of Klec-Sand Pit from other samples. Both phytoplankton and cyanobacteria were represented with hundreds of sequence reads per sample, a finding corroborated by microscopy. In particular, ice from Klec-Sand Pit contained high contributions from photoautotrophs accounting for 25% of total reads with reads dominated by single operational taxonomic units (OTUs) of the cyanobacterium Planktothrix sp. and two filamentous diatoms. Dominant OTUs recovered from ice were largely absent (< 0.01%) from underlying water suggestive of low floristic similarity of phytoplankton partitioned between these phases. Photosynthetic characterization of phototrophs resident in water and ice analysed by variable chlorophyll a fluorescence showed that communities from both phases were photosynthetically active, thus supporting ice as viable habitat for phytoplankton in freshwater lakes and reservoirs. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  2. Cold-active halophilic bacteria from the ice-sealed Lake Vida, Antarctica.

    PubMed

    Mondino, Lindsay J; Asao, Marie; Madigan, Michael T

    2009-10-01

    Lake Vida is a large, permanently ice-covered lake in the Victoria Valley of the McMurdo Dry Valleys, Antarctica and is unique among Dry Valley lakes because it is ice-sealed, with an ice-cover of nearly 19 m. Enrichment cultures of melt-water from Lake Vida 15.9 m ice yielded five pure cultures of aerobic, heterotrophic bacteria. Of these, one strain grew at -8 degrees C and the four others at -4 degrees C. All isolates were either halotolerant or halophilic, with two strains capable of growth at 15% NaCl. Phylogenetic analysis revealed the Lake Vida isolates to be Gammaproteobacteria, related to species of Psychrobacter and Marinobacter. This is the first report of pure cultures of bacteria from Lake Vida, and the isolates displayed a phenotype consistent with life in a cold hypersaline environment.

  3. Diversity of bacteria in surface ice of Austre Lovénbreen glacier, Svalbard.

    PubMed

    Zeng, Yin-Xin; Yan, Ming; Yu, Yong; Li, Hui-Rong; He, Jian-Feng; Sun, Kun; Zhang, Fang

    2013-05-01

    Two 16S rRNA gene clone libraries Cores 1U and 2U were constructed using two ice core samples collected from Austre Lovénbreen glacier in Svalbard. The two libraries yielded a total of 262 clones belonging to 59 phylotypes. Sequences fell into 10 major lineages of the domain Bacteria, including Proteobacteria (alpha, beta, gamma and delta subdivisions), Bacteroidetes, Actinobacteria, Firmicutes, Acidobacteria, Deinococcus-Thermus, Chloroflexi, Planctomycetes, Cyanobacteria and candidate division TM7. Among them, Bacteroidetes, Actinobacteria, Alphaproteobacteria and Cyanobacteria were most abundant. UniFrac data showed no significant differences in community composition between the two ice cores. A total of nineteen bacterial strains from the genera Pseudoalteromonas and Psychrobacter were isolated from the ice cores. Phylogenetic and phenotypic analyses revealed a close relationship between the ice core isolates and bacteria in marine environments, indicating a wide distribution of some bacterial phylotypes in both terrestrial and marine ecosystems.

  4. New Directions in the Study of Bacteria Inhabiting Very Cold Sea-Ice Formations

    NASA Astrophysics Data System (ADS)

    Deming, J. W.

    2004-12-01

    The development of new techniques for evaluating physical, chemical and microbial aspects of unmelted ice formations has led to a series of revelations about very cold saline ice (Arctic winter sea ice) as a habitat for life. Some of the remarkable features observed microscopically in unmelted ice at temperatures down to at least minus 15 degrees C include the physical connectivity of liquid brine inclusions on a micrometer scale, the extensive presence of complex exopolymers within the fluid inclusions, and the apparent attachment of dividing bacteria to the ice wall of a brine pore. When coupled with studies that involve melting ice but into salt solutions to minimize thermal and osmotic shocks to bacteria located within the brine inclusions, the hypothesis that bacterial activity continues even at the coldest temperature yet tested (minus 20 degrees C) has been supported. I recently worked to extend the study of very cold unmelted and brine-melted sea ice to include an assessment of extracellular enzyme activity (EEA). In other porous but less extreme environments, the detection of EEA (dominated by proteolytic activity) has reflected an important foraging strategy in use by heterotrophic bacteria dependent on acquiring small-sized, nitrogen-rich organic compounds for their livelihood. Taking advantage of facilities aboard the Canadian icebreaker Amundsen, newly renovated for science and frozen into Franklin Bay (Canadian Arctic) during winter 2004, I explored means to test for EEA (particularly leucine amino-peptidase activity), using fluorescently labeled substrate analogs, under in situ ice-brine conditions and over a range of temperatures and salt concentrations. Although methods remain to be fully optimized, preliminary results indicated detectable EEA down to minus 12 degrees C, with thermal optima much lower than previously detected in warmer (summer) sea ice and examples of possible activity at minus 18 degrees C, the lowest temperature tested. Graphical

  5. Isolation of bacteria and 16S rDNAs from Lake Vostok accretion ice.

    PubMed

    Christner, B C; Mosley-Thompson, E; Thompson, L G; Reeve, J N

    2001-09-01

    Lake Vostok, the largest subglacial lake in Antarctica, is separated from the surface by approximately 4 km of glacial ice. It has been isolated from direct surface input for at least 420 000 years, and the possibility of a novel environment and ecosystem therefore exists. Lake Vostok water has not been sampled, but an ice core has been recovered that extends into the ice accreted below glacial ice by freezing of Lake Vostok water. Here, we report the recovery of bacterial isolates belonging to the Brachybacteria, Methylobacterium, Paenibacillus and Sphingomonas lineages from a sample of melt water from this accretion ice that originated 3593 m below the surface. We have also amplified small-subunit ribosomal RNA-encoding DNA molecules (16S rDNAs) directly from this melt water that originated from alpha- and beta-proteobacteria, low- and high-G+C Gram-positive bacteria and a member of the Cytophaga/Flavobacterium/Bacteroides lineage.

  6. Sensory acceptance and survival of probiotic bacteria in ice cream produced with different overrun levels.

    PubMed

    Ferraz, Juliana L; Cruz, Adriano G; Cadena, Rafael S; Freitas, Monica Q; Pinto, Uelinton M; Carvalho, Celio C; Faria, Jose A F; Bolini, Helena M A

    2012-01-01

    The effect of different overrun levels on the sensory acceptance and survival of probiotic bacteria in ice cream was investigated. Vanilla ice creams supplemented with Lactobacillus acidophilus were processed with overruns of 45%, 60%, and 90%. Viable probiotic bacterial counts and sensory acceptance were assessed. All the ice creams presented a minimum count of 6 log CFU/g at the end of 60 d of frozen storage. However, higher overrun levels negatively influenced cell viability, being reported a decrease of 2 log CFU/g for the 90% overrun treatment. In addition, it was not reported an influence about acceptability with respect to appearance, aroma, and taste of the ice creams (P > 0.05). Overall, the results suggest that lower overrun levels should be adopted during the manufacture of ice cream in order to maintain its probiotic status through the shelf life.

  7. Ice-nucleating bacteria control the order and dynamics of interfacial water.

    PubMed

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A; Fischer, Sean A; Pfaendtner, Jim; Backus, Ellen H G; Nagata, Yuki; Fröhlich-Nowoisky, Janine; Schmüser, Lars; Mauri, Sergio; Scheel, Jan F; Knopf, Daniel A; Pöschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-04-01

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice-active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. The freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.

  8. Ice-nucleating bacteria control the order and dynamics of interfacial water

    SciTech Connect

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; Fischer, Sean A.; Pfaendtner, Jim; Backus, Ellen H. G.; Nagata, Yuki; Frohlich-Nowoisky, Janine; Schmuser, Lars; Mauri, Sergio; Scheel, Jan F.; Knopf, Daniel A.; Poschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-04-22

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. Finally, the freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.

  9. Ice-nucleating bacteria control the order and dynamics of interfacial water

    PubMed Central

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; Fischer, Sean A.; Pfaendtner, Jim; Backus, Ellen H. G.; Nagata, Yuki; Fröhlich-Nowoisky, Janine; Schmüser, Lars; Mauri, Sergio; Scheel, Jan F.; Knopf, Daniel A.; Pöschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-01-01

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice-active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. The freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy. PMID:27152346

  10. Ice-nucleating bacteria control the order and dynamics of interfacial water

    DOE PAGES

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; ...

    2016-04-22

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering onmore » the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. Finally, the freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.« less

  11. Culturable bacteria in subglacial sediments and ice from two Southern Hemisphere glaciers.

    PubMed

    Foght, J; Aislabie, J; Turner, S; Brown, C E; Ryburn, J; Saul, D J; Lawson, W

    2004-05-01

    Viable prokaryotes have been detected in basal sediments beneath the few Northern Hemisphere glaciers that have been sampled for microbial communities. However, parallel studies have not previously been conducted in the Southern Hemisphere, and subglacial environments in general are a new and underexplored niche for microbes. Unfrozen subglacial sediments and overlying glacier ice samples collected aseptically from the Fox Glacier and Franz Josef Glacier in the Southern Alps of New Zealand now have been shown to harbor viable microbial populations. Total direct counts of 2-7 x 10(6) cells g(-1) dry weight sediment were observed, whereas culturable aerobic heterotrophs ranged from 6-9 x 10(5) colony-forming units g(-1) dry weight. Viable counts in the glacier ice typically were 3-4 orders of magnitude smaller than in sediment. Nitrate-reducing and ferric iron-reducing bacteria were detected in sediment samples from both glaciers, but were few or below detection limits in the ice samples. Nitrogen-fixing bacteria were detected only in the Fox Glacier sediment. Restriction fragment analysis of 16S rDNA amplified from 37 pure cultures of aerobic heterotrophs capable of growth at 4 degrees C yielded 23 distinct groups, of which 11 were identified as beta-Proteobacteria. 16S rDNA sequences from representatives of these 11 groups were analyzed phylogenetically and shown to cluster with bacteria such as Polaromonas vacuolata and Rhodoferax antarcticus, or with clones obtained from permanently cold environments. Chemical analysis of sediment and ice samples revealed a dilute environment for microbial life. Nevertheless, both the sediment samples and one ice sample demonstrated substantial aerobic mineralization of 14C-acetate at 8 degrees C, indicating that sufficient nutrients and viable psychrotolerant microbes were present to support metabolism. Unfrozen subglacial sediments may represent a significant global reservoir of biological activity with the potential to

  12. Diversity and physiology of culturable bacteria associated with a coastal Antarctic ice core.

    PubMed

    Antony, Runa; Krishnan, K P; Laluraj, C M; Thamban, Meloth; Dhakephalkar, P K; Engineer, Anupama S; Shivaji, S

    2012-06-20

    Microbiological studies of polar ice at different depths may provide important comparisons, as they preserve records of microbial cells and past climate. In this study, we examined bacterial abundance, diversity and glaciochemical composition from three depths of an ice core from coastal Dronning Maud Land, East Antarctica. Higher bacterial abundance corresponded with high in situ sea-salt Na(+) and dust concentration, suggesting that bacteria might have been transported and deposited into ice along with dust particles and marine aerosols. Fourteen bacterial isolates belonging to the genera Methylobacterium, Brevundimonas, Paenibacillus, Bacillus and Micrococcus were retrieved. Frequent isolation of similar bacterial genera from different cold environments suggests that they possess features that enable survival and metabolism for extended periods of time at sub-zero temperatures. The highest number and diversity of recoverable bacteria was obtained from 49 m depth corresponding to 1926 AD and consisted of bacteria from 4 different genera whereas at 11 m (1989 AD) and 33 m (1953 AD) samples only species belonging to the genera Bacillus was recovered. Among the Bacillus species, Bacillus aryabhattai which has been reported only from the upper stratosphere, was isolated and is the first record from the Earth's surface. Methylobacterium was the most dominant genera at 49 m depth and its prevalence is attributable to a combination of high in situ methanesulfonate concentration, specialized metabolism and environmental hardiness of Methylobacterium. Some of the isolated bacteria were found to respire and grow using methanesulfonate, suggesting that they may utilize this substrate to sustain growth in ice. In addition, NO(3)(-) (2.93-3.69 μM), NH(4)(+) (1.45-3.90 μM) and PO(4)(3-) (0.01-0.75 μM) present in the ice could be potential sources fueling bacterial metabolism in this environment. It could be deduced from the study that variation in bacterial abundance and

  13. Observations of Ice Nucleation and Propagation in Plants Using Infrared Video Thermography.

    PubMed Central

    Wisniewski, M.; Lindow, S. E.; Ashworth, E. N.

    1997-01-01

    We evaluated the use of infrared (IR) video thermography to observe directly ice nucleation and propagation in plants. An imaging radiometer with an HgCdTe long-wave (8-12 [mu]m) detector was utilized to image the thermal response of plants during freezing. IR images were analyzed in real time and recorded on videotape. Information on the videotape was subsequently accessed and analyzed utilizing IR image analysis software. Freezing of water droplets as small as 0.5 [mu]L was clearly detectable with the radiometer. Additionally, a comparison of temperature tracking data collected by the radiometer with data collected with thermocouples showed close correspondence. Monitoring of an array of plant species under different freezing conditions revealed that ice nucleation and propagation are readily observable by thermal imaging. In many instances, the ice nucleation-active bacterium Pseudomonas syringae placed on test plants could be seen to initiate freezing of the whole plant. Apparent ice nucleation by intrinsic nucleators, despite the presence of ice nucleation-active bacteria, was also evident in some species. Floral bud tissues of peach (Prunus persica) could be seen to supercool below the temperature of stem tissues, and ice nucleation at the site of insertion of the thermocouple was frequently observed. Rates of propagation of ice in different tissues were also easily measured by thermal imaging. This study demonstrates that IR thermography is an excellent method for studying ice nucleation and propagation in plants. PMID:12223611

  14. Properties and biotechnological applications of ice-binding proteins in bacteria.

    PubMed

    Cid, Fernanda P; Rilling, Joaquín I; Graether, Steffen P; Bravo, Leon A; Mora, María de La Luz; Jorquera, Milko A

    2016-06-01

    Ice-binding proteins (IBPs), such as antifreeze proteins (AFPs) and ice-nucleating proteins (INPs), have been described in diverse cold-adapted organisms, and their potential applications in biotechnology have been recognized in various fields. Currently, both IBPs are being applied to biotechnological processes, primarily in medicine and the food industry. However, our knowledge regarding the diversity of bacterial IBPs is limited; few studies have purified and characterized AFPs and INPs from bacteria. Phenotypically verified IBPs have been described in members belonging to Gammaproteobacteria, Actinobacteria and Flavobacteriia classes, whereas putative IBPs have been found in Gammaproteobacteria, Alphaproteobacteria and Bacilli classes. Thus, the main goal of this minireview is to summarize the current information on bacterial IBPs and their application in biotechnology, emphasizing the potential application in less explored fields such as agriculture. Investigations have suggested the use of INP-producing bacteria antagonists and AFPs-producing bacteria (or their AFPs) as a very attractive strategy to prevent frost damages in crops. UniProt database analyses of reported IBPs (phenotypically verified) and putative IBPs also show the limited information available on bacterial IBPs and indicate that major studies are required.

  15. Comparison of dry medium culture plates for mesophilic aerobic bacteria in milk, ice cream, ham, and codfish fillet products.

    PubMed

    Park, Junghyun; Kim, Myunghee

    2013-12-01

    This study was performed to compare the performance of Sanita-Kun dry medium culture plate with those of traditional culture medium and Petrifilm dry medium culture plate for the enumeration of the mesophilic aerobic bacteria in milk, ice cream, ham, and codfish fillet. Mesophilic aerobic bacteria were comparatively evaluated in milk, ice cream, ham, and codfish fillet using Sanita-Kun aerobic count (SAC), Petrifilm aerobic count (PAC), and traditional plate count agar (PCA) media. According to the results, all methods showed high correlations of 0.989~1.000 and no significant differences were observed for enumerating the mesophilic aerobic bacteria in the tested food products. SAC method was easier to perform and count colonies efficiently as compared to the PCA and PAC methods. Therefore, we concluded that the SAC method offers an acceptable alternative to the PCA and PAC methods for counting the mesophilic aerobic bacteria in milk, ice cream, ham, and codfish fillet products.

  16. Massive regime shifts and high activity of heterotrophic bacteria in an ice-covered lake.

    PubMed

    Bižić-Ionescu, Mina; Amann, Rudolf; Grossart, Hans-Peter

    2014-01-01

    In winter 2009/10, a sudden under-ice bloom of heterotrophic bacteria occurred in the seasonally ice-covered, temperate, deep, oligotrophic Lake Stechlin (Germany). Extraordinarily high bacterial abundance and biomass were fueled by the breakdown of a massive bloom of Aphanizomenon flos-aquae after ice formation. A reduction in light resulting from snow coverage exerted a pronounced physiological stress on the cyanobacteria. Consequently, these were rapidly colonized, leading to a sudden proliferation of attached and subsequently of free-living heterotrophic bacteria. Total bacterial protein production reached 201 µg C L(-1) d(-1), ca. five times higher than spring-peak values that year. Fluorescence in situ hybridization and denaturing gradient gel electrophoresis at high temporal resolution showed pronounced changes in bacterial community structure coinciding with changes in the physiology of the cyanobacteria. Pyrosequencing of 16S rRNA genes revealed that during breakdown of the cyanobacterial population, the diversity of attached and free-living bacterial communities were reduced to a few dominant families. Some of these were not detectable during the early stages of the cyanobacterial bloom indicating that only specific, well adapted bacterial communities can colonize senescent cyanobacteria. Our study suggests that in winter, unlike commonly postulated, carbon rather than temperature is the limiting factor for bacterial growth. Frequent phytoplankton blooms in ice-covered systems highlight the need for year-round studies of aquatic ecosystems including the winter season to correctly understand element and energy cycling through aquatic food webs, particularly the microbial loop. On a global scale, such knowledge is required to determine climate change induced alterations in carbon budgets in polar and temperate aquatic systems.

  17. Massive Regime Shifts and High Activity of Heterotrophic Bacteria in an Ice-Covered Lake

    PubMed Central

    Bižić-Ionescu, Mina; Amann, Rudolf; Grossart, Hans-Peter

    2014-01-01

    In winter 2009/10, a sudden under-ice bloom of heterotrophic bacteria occurred in the seasonally ice-covered, temperate, deep, oligotrophic Lake Stechlin (Germany). Extraordinarily high bacterial abundance and biomass were fueled by the breakdown of a massive bloom of Aphanizomenon flos-aquae after ice formation. A reduction in light resulting from snow coverage exerted a pronounced physiological stress on the cyanobacteria. Consequently, these were rapidly colonized, leading to a sudden proliferation of attached and subsequently of free-living heterotrophic bacteria. Total bacterial protein production reached 201 µg C L−1 d−1, ca. five times higher than spring-peak values that year. Fluorescence in situ hybridization and denaturing gradient gel electrophoresis at high temporal resolution showed pronounced changes in bacterial community structure coinciding with changes in the physiology of the cyanobacteria. Pyrosequencing of 16S rRNA genes revealed that during breakdown of the cyanobacterial population, the diversity of attached and free-living bacterial communities were reduced to a few dominant families. Some of these were not detectable during the early stages of the cyanobacterial bloom indicating that only specific, well adapted bacterial communities can colonize senescent cyanobacteria. Our study suggests that in winter, unlike commonly postulated, carbon rather than temperature is the limiting factor for bacterial growth. Frequent phytoplankton blooms in ice-covered systems highlight the need for year-round studies of aquatic ecosystems including the winter season to correctly understand element and energy cycling through aquatic food webs, particularly the microbial loop. On a global scale, such knowledge is required to determine climate change induced alterations in carbon budgets in polar and temperate aquatic systems. PMID:25419654

  18. Spatial heterogeneity and temporal dynamics of particles, bacteria, and pEPS in Arctic winter sea ice

    NASA Astrophysics Data System (ADS)

    Collins, R. Eric; Carpenter, Shelly D.; Deming, Jody W.

    2008-12-01

    Abundances of particles, total bacteria, and particulate extracellular polymeric substances (pEPS) in Arctic sea ice were tracked through a winter season to examine the impact of combined extremes of low temperature and high salinity on the prokaryotic microbial community. Three horizons, centered at depths of 25, 45, and 65 cm from the ice surface, with mean seasonal temperatures of - 20, - 17, and - 13 °C, respectively, were sampled 16 times over the course of 12 weeks. Microscopic counts of bacteria (stained with DAPI) and particles (stained with acridine orange) reflected the dynamic conditions of the growing ice sheet, with greater abundances and variability in the upper ice horizons compared to the lower. The trend of higher particle and bacterial abundances in the upper ice was corroborated by several full-depth profiles taken during the expedition, which also displayed significantly decreasing cell abundance with depth. Bacterial abundance declined slowly and significantly with time in the upper and middle ice horizons, but not in the lowest, suggesting that much of the prokaryotic microbial community is resilient to extreme environmental conditions. We found that pEPS concentrations increased significantly with time and with decreasing temperatures in all depth horizons, which may lend support to the argument that sea ice bacteria produce EPS in situ as a cryoprotectant.

  19. Cryo-protective effect of an ice-binding protein derived from Antarctic bacteria.

    PubMed

    Mangiagalli, Marco; Bar-Dolev, Maya; Tedesco, Pietro; Natalello, Antonino; Kaleda, Aleksei; Brocca, Stefania; de Pascale, Donatella; Pucciarelli, Sandra; Miceli, Cristina; Bravslavsky, Ido; Lotti, Marina

    2017-01-01

    Cold environments are populated by organisms able to contravene deleterious effects of low temperature by diverse adaptive strategies, including the production of ice binding proteins (IBPs) that inhibit the growth of ice crystals inside and outside cells. We describe the properties of such a protein (EfcIBP) identified in the metagenome of an Antarctic biological consortium composed of the ciliate Euplotes focardii and psychrophilic non-cultured bacteria. Recombinant EfcIBP can resist freezing without any conformational damage and is moderately heat stable, with a midpoint temperature of 66.4 °C. Tested for its effects on ice, EfcIBP shows an unusual combination of properties not reported in other bacterial IBPs. First, it is one of the best-performing IBPs described to date in the inhibition of ice recrystallization, with effective concentrations in the nanomolar range. Moreover, EfcIBP has thermal hysteresis activity (0.53 °C at 50 μm) and it can stop a crystal from growing when held at a constant temperature within the thermal hysteresis gap. EfcIBP protects purified proteins and bacterial cells from freezing damage when exposed to challenging temperatures. EfcIBP also possesses a potential N-terminal signal sequence for protein transport and a DUF3494 domain that is common to secreted IBPs. These features lead us to hypothesize that the protein is either anchored at the outer cell surface or concentrated around cells to provide survival advantage to the whole cell consortium. © 2016 Federation of European Biochemical Societies.

  20. Do ice nucleating agents limit the supercooling ability of the land snail Cornu aspersum?

    PubMed

    Ansart, A; Nicolai, A; Vernon, P; Madec, L

    2010-01-01

    The supercooling ability of adults and eggs of the partially freezing tolerant land snail Cornu aspersum remains limited to high subzero temperatures (ca. -5 degree C) whatever the conditions, suggesting the presence of ice nucleating agents (INAs). In this study, we investigated the nucleation activity of the digestive tract of adult snails, eggs and their direct environment: food, faeces and soil. The mucous ribbon always present in the distal intestine of adults exhibited a heat-sensitive (i.e. organic) nucleation activity, close to that of the entire snails during dormant states (aestivation and hibernation). However, a microbial nature of these INAs could not be established in inactive snails. The food provided to active snails contained ice nucleating bacteria, which followed the digestive tract to be found in the intestine and in the faeces, but with a decreasing concentration along the transit. Eggshells also presented a heat-sensitive nucleation activity, which could be related to its structure. Moreover, eggs are laid directly in the soil which contained both organic and mineral INAs. This study is the first to demonstrate the implication of organic INAs in the cold hardiness of a terrestrial gastropod.

  1. Fecal indicator bacteria persistence under natural conditions in an ice-covered river.

    PubMed Central

    Davenport, C V; Sparrow, E B; Gordon, R C

    1976-01-01

    Total coliform (TC), fecal coliform (FC), and fecal streptococcus (FS) survival characteristics, under natural conditions at 0 degrees C in an ice-covered river, were examined during February and March 1975. The membrane filter (MF) technique was used throughout the study, and the multiple-tube (MPN) method was used in parallel on three preselected days for comparative recovery of these bacteria. Survival was studied at seven sample stations downstream from all domestic pollution sources in a 317-km reach of the river having 7.1 days mean flow time (range of 6.0 to 9.1 days). The mean indicator bacteria densities decreased continuously at successive stations in this reach and, after adjustment for dilution, the most rapid die-off was found to occur during the first 1.9 days, followed by a slower decrease. After 7.1 days, the relative survival was TC less than FC less than FS, with 8.4%, 15.7%, and 32.8% of the initial populations remaining viable, respectively. These rates are higher than previously reported and suggest that the highest survival rates for these bacteria in receiving streams can be expected at 0 degree C under ice cover. Additionally, the FC-FS ratio was greater than 5 at all stations, indicating that this ratio may be useable for determining the source of fecal pollution in receiving streams for greater than 7 days flow time at low water temperatures. The MPN and MF methods gave comparable results for the TC and FS at all seven sample stations, with both the direct and verified MF counts within the 95% confidence limits of the respective MPNs in most samples, but generally lower than the MPN index. Although FC recovery on membrane filters was comparable results at stations near the pollution source. However, the results became more comparable with increasing flow time. The results of this study indicate that heat shock is a major factor in suppression of the FC counts on the membrane filters at 44.5 degree C. Heat shock may be minimized by extended

  2. Diversity and cold-active hydrolytic enzymes of culturable bacteria associated with Arctic sea ice, Spitzbergen.

    PubMed

    Groudieva, Tatiana; Kambourova, Margarita; Yusef, Hoda; Royter, Maryna; Grote, Ralf; Trinks, Hauke; Antranikian, Garabed

    2004-12-01

    The diversity of culturable bacteria associated with sea ice from four permanently cold fjords of Spitzbergen, Arctic Ocean, was investigated. A total of 116 psychrophilic and psychrotolerant strains were isolated under aerobic conditions at 4 degrees C. The isolates were grouped using amplified rDNA restriction analysis fingerprinting and identified by partial sequencing of 16S rRNA gene. The bacterial isolates fell in five phylogenetic groups: subclasses alpha and gamma of Proteobacteria, the Bacillus-Clostridium group, the order Actinomycetales, and the Cytophaga-Flexibacter-Bacteroides (CFB) phylum. Over 70% of the isolates were affiliated with the Proteobacteria gamma subclass. Based on phylogenetic analysis (<98% sequence similarity), over 40% of Arctic isolates represent potentially novel species or genera. Most of the isolates were psychrotolerant and grew optimally between 20 and 25 degrees C. Only a few strains were psychrophilic, with an optimal growth at 10-15 degrees C. The majority of the bacterial strains were able to secrete a broad range of cold-active hydrolytic enzymes into the medium at a cultivation temperature of 4 degrees C. The isolates that are able to degrade proteins (skim milk, casein), lipids (olive oil), and polysaccharides (starch, pectin) account for, respectively, 56, 31, and 21% of sea-ice and seawater strains. The temperature dependences for enzyme production during growth and enzymatic activity were determined for two selected enzymes, alpha-amylase and beta-galactosidase. Interestingly, high levels of enzyme productions were measured at growth temperatures between 4 and 10 degrees C, and almost no production was detected at higher temperatures (20-30 degrees C). Catalytic activity was detected even below the freezing point of water (at -5 degrees C), demonstrating the unique properties of these enzymes.

  3. Marine bacteria in deep Arctic and Antarctic ice cores: a proxy for evolution in oceans over 300 million generations

    NASA Astrophysics Data System (ADS)

    Price, P. B.; Bay, R. C.

    2012-06-01

    Using fluorescence spectrometry to map autofluorescence of chlorophyll (Chl) and tryptophan (Trp) versus depth in polar ice cores in the US National Ice Core Laboratory, we found that the Chl and Trp concentrations often showed an annual modulation of up to 25%, with peaks at depths corresponding to local summers. Using epifluorescence microscopy (EFM) and flow cytometry (FCM) triggered on 670 nm fluorescence (red) to study microbes from unstained melts of the polar ice, we inferred that picocyanobacteria may have been responsible for the red fluorescence in the cores. Micron-size bacteria in all ice melts from 2 Arctic and 6 Antarctic sites showed FCM patterns of scattering and of red vs. orange fluorescence (interpreted as due to Chl vs. phycoerythrin (PE)) that bore similarities to patterns of cultures of unstained picocyanobacteria Prochlorococcus and Synechococcus. Concentrations in ice from all sites were low but measurable at ~1 to ~103 cells cm-3. Calibrations showed that FCM patterns of mineral grains and volcanic ash could be distinguished from microbes with high efficiency by triggering on scattering instead of by red fluorescence. Average Chl and PE autofluorescence intensities showed no decrease per cell with time during up to 150 000 yr of storage in glacial ice. Taking into account the annual modulation of ~25% and seasonal changes of ocean temperatures and winds, we suggest that picocyanobacteria are wind-transported year-round from warmer ocean waters onto polar ice. Ice cores offer the opportunity to study evolution of marine microbes over ~300 million generations by analyzing their genomes vs. depth in glacial ice over the last 700 000 yr as frozen proxies for changes in their genomes in oceans.

  4. Marine bacteria in deep Arctic and Antarctic ice cores: a proxy for evolution in oceans over 300 million generations

    NASA Astrophysics Data System (ADS)

    Price, P. B.; Bay, R. C.

    2012-10-01

    Using fluorescence spectrometry to map autofluorescence of chlorophyll (Chl) and tryptophan (Trp) versus depth in polar ice cores in the US National Ice Core Laboratory, we found that the Chl and Trp concentrations often showed an annual modulation of up to 25%, with peaks at depths corresponding to local summers. Using epifluorescence microscopy (EFM) and flow cytometry (FCM) triggered on red fluorescence at 670 nm to study microbes from unstained melts of the polar ice, we inferred that picocyanobacteria may have been responsible for the red fluorescence in the cores. Micron-size bacteria in all ice melts from Arctic and Antarctic sites showed FCM patterns of scattering and of red vs. orange fluorescence (interpreted as due to Chl vs. phycoerythrin (PE)) that bore similarities to patterns of cultures of unstained picocyanobacteria Prochlorococcus and Synechococcus. Concentrations in ice from all sites were low, but measurable at ~ 1 to ~ 103 cells cm-3. Calibrations showed that FCM patterns of mineral grains and volcanic ash could be distinguished from microbes with high efficiency by triggering on scattering instead of by red fluorescence. Average Chl and PE autofluorescence intensities showed no decrease per cell with time during up to 150 000 yr of storage in glacial ice. Taking into account the annual modulation of ~ 25% and seasonal changes of ocean temperatures and winds, we suggest that picocyanobacteria are wind-transported year-round from warmer ocean waters onto polar ice. Ice cores offer the opportunity to study evolution of marine microbes over ~ 300 million generations by analysing their genomes vs. depth in glacial ice over the last 700 000 yr as frozen proxies for changes in their genomes in oceans.

  5. Ice nucleation by water-soluble macromolecules

    NASA Astrophysics Data System (ADS)

    Pummer, B. G.; Budke, C.; Augustin-Bauditz, S.; Niedermeier, D.; Felgitsch, L.; Kampf, C. J.; Huber, R. G.; Liedl, K. R.; Loerting, T.; Moschen, T.; Schauperl, M.; Tollinger, M.; Morris, C. E.; Wex, H.; Grothe, H.; Pöschl, U.; Koop, T.; Fröhlich-Nowoisky, J.

    2015-04-01

    Cloud glaciation is critically important for the global radiation budget (albedo) and for initiation of precipitation. But the freezing of pure water droplets requires cooling to temperatures as low as 235 K. Freezing at higher temperatures requires the presence of an ice nucleator, which serves as a template for arranging water molecules in an ice-like manner. It is often assumed that these ice nucleators have to be insoluble particles. We point out that also free macromolecules which are dissolved in water can efficiently induce ice nucleation: the size of such ice nucleating macromolecules (INMs) is in the range of nanometers, corresponding to the size of the critical ice embryo. As the latter is temperature-dependent, we see a correlation between the size of INMs and the ice nucleation temperature as predicted by classical nucleation theory. Different types of INMs have been found in a wide range of biological species and comprise a variety of chemical structures including proteins, saccharides, and lipids. Our investigation of the fungal species Acremonium implicatum, Isaria farinosa, and Mortierella alpina shows that their ice nucleation activity is caused by proteinaceous water-soluble INMs. We combine these new results and literature data on INMs from fungi, bacteria, and pollen with theoretical calculations to develop a chemical interpretation of ice nucleation and water-soluble INMs. This has atmospheric implications since many of these INMs can be released by fragmentation of the carrier cell and subsequently may be distributed independently. Up to now, this process has not been accounted for in atmospheric models.

  6. Diversity and characterization of mercury-resistant bacteria in snow, freshwater and sea-ice brine from the High Arctic.

    PubMed

    Møller, Annette K; Barkay, Tamar; Abu Al-Soud, Waleed; Sørensen, Søren J; Skov, Henrik; Kroer, Niels

    2011-03-01

    It is well-established that atmospheric deposition transports mercury from lower latitudes to the Arctic. The role of bacteria in the dynamics of the deposited mercury, however, is unknown. We characterized mercury-resistant bacteria from High Arctic snow, freshwater and sea-ice brine. Bacterial densities were 9.4 × 10(5), 5 × 10(5) and 0.9-3.1 × 10(3) cells mL(-1) in freshwater, brine and snow, respectively. Highest cultivability was observed in snow (11.9%), followed by freshwater (0.3%) and brine (0.03%). In snow, the mercury-resistant bacteria accounted for up to 31% of the culturable bacteria, but <2% in freshwater and brine. The resistant bacteria belonged to the Alpha-, Beta- and Gammaproteobacteria, Firmicutes, Actinobacteria, and Bacteriodetes. Resistance levels of most isolates were not temperature dependent. Of the resistant isolates, 25% reduced Hg(II) to Hg(0). No relation between resistance level, ability to reduce Hg(II) and phylogenetic group was observed. An estimation of the potential bacterial reduction of Hg(II) in snow suggested that it was important in the deeper snow layers where light attenuation inhibited photoreduction. Thus, by reducing Hg(II) to Hg(0), mercury-resistant bacteria may limit the supply of substrate for methylation processes and, hence, contribute to lowering the risk that methylmercury is being incorporated into the Arctic food chains.

  7. Differences in community composition of bacteria in four deep ice sheets in western China

    NASA Astrophysics Data System (ADS)

    An, L.; Chen, Y.; Xiang, S.-R.; Shang, T.-C.; Tian, L.-De

    2010-02-01

    Microbial community patterns vary in glaciers world wide, presenting unique responses to global climatic and environmental changes. Four bacterial clone libraries were established by 16S rRNA gene amplification from four ice layers along the 42-m-long ice core MuztB drilled from the Muztag Ata Glacier. A total of 152 bacterial sequences obtained from the ice core MuztB were phylogenetically compared with the 71 previously reported sequences from three ice cores extracted from ice caps Malan, Dunde, and Puruoganri. The six functional clusters Flavisolibacter, Flexibacter (Bacteroidetes), Acinetobacter, Enterobacter (Gammaproteobacteria), Planococcus/Anoxybacillus (Firmicutes), and Propionibacter/Luteococcus (Actinobacteria) frequently occurred along the Muztag Ata Glacier profile. Sequence analysis showed that most of the sequences from the ice core clustered with those from cold environments, and the sequences from the same glacier formed a distinct cluster. Moreover, bacterial communities from the same location or similarly aged ice formed a cluster, and were clearly separate from those from other geographically isolated glaciers. In a summary, the findings provide preliminary evidence of zone distribution of microbial community, support our hypothesis of the spatial and temporal biogeography of microorganisms in glacial ice.

  8. Evidence for a missing source of efficient ice nuclei

    NASA Astrophysics Data System (ADS)

    Du, Rui; Du, Pengrui; Lu, Zedong; Ren, Weishan; Liang, Zongmin; Qin, Saisai; Li, Ziming; Wang, Yaling; Fu, Pingqing

    2017-01-01

    It has been known for several decades that some bioaerosols, such as ice-nucleation-active (INA) bacteria, especially Pseudomonas syringae strains, may play a critical potential role in the formation of clouds and precipitation. We investigated bacterial and fungal ice nuclei (IN) in rainwater samples collected from the Hulunber temperate grasslands in North China. The median freezing temperatures (T50) for three years’ worth of unprocessed rain samples were greater than ‑10 °C based on immersion freezing testing. The heat and filtration treatments inactivated 7–54% and 2–89%, respectively, of the IN activity at temperatures warmer than ‑10 °C. We also determined the composition of the microbial community. The majority of observed Pseudomonas strains were distantly related to the verified ice-nucleating Pseudomonas strains, as revealed by phylogenetic analysis. Here, we show that there are submicron INA particles <220 nm in rainwater that are not identifiable as the known species of high-INA bacteria and fungi and there may be a new potential type of efficient submicroscale or nanoscale ice nucleator in the regional rainwater samplers. Our results suggest the need for a reinterpretation of the source of high-INA material in the formation of precipitation and contribute to the search for new methods of weather modification.

  9. Evidence for a missing source of efficient ice nuclei

    PubMed Central

    Du, Rui; Du, Pengrui; Lu, Zedong; Ren, Weishan; Liang, Zongmin; Qin, Saisai; Li, Ziming; Wang, Yaling; Fu, Pingqing

    2017-01-01

    It has been known for several decades that some bioaerosols, such as ice-nucleation-active (INA) bacteria, especially Pseudomonas syringae strains, may play a critical potential role in the formation of clouds and precipitation. We investigated bacterial and fungal ice nuclei (IN) in rainwater samples collected from the Hulunber temperate grasslands in North China. The median freezing temperatures (T50) for three years’ worth of unprocessed rain samples were greater than −10 °C based on immersion freezing testing. The heat and filtration treatments inactivated 7–54% and 2–89%, respectively, of the IN activity at temperatures warmer than −10 °C. We also determined the composition of the microbial community. The majority of observed Pseudomonas strains were distantly related to the verified ice-nucleating Pseudomonas strains, as revealed by phylogenetic analysis. Here, we show that there are submicron INA particles <220 nm in rainwater that are not identifiable as the known species of high-INA bacteria and fungi and there may be a new potential type of efficient submicroscale or nanoscale ice nucleator in the regional rainwater samplers. Our results suggest the need for a reinterpretation of the source of high-INA material in the formation of precipitation and contribute to the search for new methods of weather modification. PMID:28045124

  10. Taxon interactions control the distributions of cryoconite bacteria colonizing a High Arctic ice cap.

    PubMed

    Gokul, Jarishma K; Hodson, Andrew J; Saetnan, Eli R; Irvine-Fynn, Tristram D L; Westall, Philippa J; Detheridge, Andrew P; Takeuchi, Nozomu; Bussell, Jennifer; Mur, Luis A J; Edwards, Arwyn

    2016-08-01

    Microbial colonization of glacial ice surfaces incurs feedbacks which affect the melting rate of the ice surface. Ecosystems formed as microbe-mineral aggregates termed cryoconite locally reduce ice surface albedo and represent foci of biodiversity and biogeochemical cycling. Consequently, greater understanding the ecological processes in the formation of functional cryoconite ecosystems upon glacier surfaces is sought. Here, we present the first bacterial biogeography of an ice cap, evaluating the respective roles of dispersal, environmental and biotic filtration occurring at local scales in the assembly of cryoconite microbiota. 16S rRNA gene amplicon semiconductor sequencing of cryoconite colonizing a Svalbard ice cap coupled with digital elevation modelling of physical parameters reveals the bacterial community is dominated by a ubiquitous core of generalist taxa, with evidence for a moderate pairwise distance-decay relationship. While geographic position and melt season duration are prominent among environmental predictors of community structure, the core population of taxa appears highly influential in structuring the bacterial community. Taxon co-occurrence network analysis reveals a highly modular community structured by positive interactions with bottleneck taxa, predominantly Actinobacteria affiliated to isolates from soil humus. In contrast, the filamentous cyanobacterial taxon (assigned to Leptolyngbya/Phormidesmis pristleyi) which dominates the community and binds together granular cryoconite are poorly connected to other taxa. While our study targeted one ice cap, the prominent role of generalist core taxa with close environmental relatives across the global cryosphere indicate discrete roles for cosmopolitan Actinobacteria and Cyanobacteria as respective keystone taxa and ecosystem engineers of cryoconite ecosystems colonizing ice caps. © 2016 John Wiley & Sons Ltd.

  11. Taxonomic characterization and the bio-potential of bacteria isolated from glacier ice cores in the High Arctic.

    PubMed

    Singh, Purnima; Singh, Shiv Mohan; Roy, Utpal

    2016-03-01

    Glacier ice and firn cores have ecological and biotechnological importance. The present study is aimed at characterizing bacteria in crustal ice cores from Svalbard, the Arctic. Counts of viable isolates ranged from 10 to 7000 CFU/ml (mean 803 CFU/ml) while the total bacterial numbers ranged from 7.20 × 10(4) to 2.59 × 10(7)  cells ml(-1) (mean 3.12 × 10(6)  cells ml(-1) ). Based on 16S rDNA sequence data, the identified species belonged to seven species, namely Bacillus barbaricus, Pseudomonas orientalis, Pseudomonas oryzihabitans, Pseudomonas fluorescens, Pseudomonas syncyanea, Sphingomonas dokdonensis, and Sphingomonas phyllosphaerae, with a sequence similarity ranging between 93.5 and 99.9% with taxa present in the database. The isolates exhibited unique phenotypic properties, and three isolates (MLB-2, MLB-5, and MLB-9) are novel species, yet to be described. To the best of our knowledge, this is the first report on characterization of cultured bacterial communities from Svalbard ice cores. We conclude that high lipase, protease, cellulase, amylase, and urease activities expressed by most of the isolates provide a clue to the potential industrial applications of these organisms. These microbes, producing cold-adapted enzymes may provide an opportunity for biotechnological research. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Flavobacterium xueshanense sp. nov. and Flavobacterium urumqiense sp. nov., two psychrophilic bacteria isolated from glacier ice.

    PubMed

    Dong, Kun; Liu, Hongcan; Zhang, Jianli; Zhou, Yuguang; Xin, Yuhua

    2012-05-01

    Two Gram-stain-negative, rod-shaped bacteria, designated strains Sr22(T) and Sr25(T), were isolated from water of melted ice from the China No.1 glacier, Xinjiang Uygur Autonomous Region, China. Cells formed yellow, circular, convex colonies. 16S rRNA gene sequence analysis indicated that strains Sr22(T) and Sr25(T) belong to the genus Flavobacterium, sharing ≤99.1  and ≤99.6 % similarity, respectively, with the type strains of recognized species of the genus. Strain Sr22(T) shared highest 16S rRNA gene sequence similarity with Flavobacterium tiangeerense CGMCC 1.6847(T) (98.6 %), Flavobacterium fryxellicola LMG 22022(T) (98.1 %) and Flavobacterium omnivorum CGMCC 1.2747(T) (99.1 %). Strain Sr25(T) shared highest similarity with Flavobacterium sinopsychrotolerans CGMCC 1.8704(T) (98.5 %), Flavobacterium degerlachei NBRC 102677(T) (98.4 %) and Flavobacterium xinjiangense CGMCC 1.2749(T) (99.5 %). The predominant fatty acids of strain Sr22(T) were iso-C(15 : 1) G (6.01 %), iso-C(15 : 0) (8.93 %), iso-C(16 : 1) H (12.68 %), iso-C(16 : 0) (10.4 %), C(15 : 1)ω6c (8.97 %), C(17 : 1)ω6c (5.96 %), iso-C(16 : 0) 3-OH (11.14 %) and summed feature 3 (comprising C(16 : 1)ω7c and/or C(16 : 1)ω6c, 12.33 %). The major fatty acids of strain Sr25(T) were iso-C(15 : 0) (10.8 %), anteiso-C(15 : 0) (5.23 %), C(15 : 1)ω6c (11.79 %), C(17 : 1)ω6c (5.43 %), iso-C(16 : 0) 3-OH (7.04 %) and summed feature 3 (20.42 %). The genomic DNA G+C contents of strains Sr22(T) and Sr25(T) were 37.2 and 35.1 mol%. On the basis of differential phenotypic and phylogenetic characteristics, these strains are considered to represent two novel species of the genus Flavobacterium, for which the names Flavobacterium xueshanense sp. nov. (type strain Sr22(T)  = CGMCC 1.9227(T)  = NBRC 106479(T)) and Flavobacterium urumqiense sp. nov. (type strain Sr25(T)  = CGMCC 1.9230(T)  = NBRC 106480

  13. Microbial ice-nucleators in cloud water at the puy de Dôme (France)

    NASA Astrophysics Data System (ADS)

    Joly, Muriel; Amato, Pierre; Deguillaume, Laurent; Attard, Eleonore; Sancelme, Martine; Monier, Marie; Morris, Cindy E.; Delort, Anne-Marie

    2013-04-01

    Ice nucleation active (INA) biological particles, in particular microorganisms, were studied in cloud water. Twelve cloud samples were collected over a period of 16 months from the puy de Dôme summit (1465 m, France) using sterile cloud droplet impactors. The samples were characterized through biological (cultures, cell counts) and physico-chemical measurements (pH, ion concentrations, carbon content…), and biological ice nuclei were investigated by droplet-freezing assays from -3°C to -13°C. The concentration of total INA particles within this temperature range typically varied from ~1 to ~100 per mL of cloud water; the concentrations of biological IN were several orders of magnitude higher than the values previously reported for precipitations. At -12°C, at least 76% of the IN were biological in origin, i.e. they were inactivated by heating at 95°C, and at temperatures above -8°C only biological material could induce ice. By culture, 44 Pseudomonas-like strains of bacteria were isolated from cloud water samples; 16% of them were found INA at the temperature of -8°C and they were identified as Pseudomonas syringae, Xanthomonas sp. and Pseudoxanthomonas sp.. Two strains induced freezing at as warm as -2°C, positioning them among the most active ice nucleators described so far. We estimated that, in average, 0.18% and more than 1% of the bacterial cells present in clouds (~104 mL-1) are INA at the temperatures of -8°C and -12°C, respectively. References: Attard E. et al. (2012) Effects of atmospheric conditions on ice nucleation activity of Pseudomonas. Atmospheric Chemistry and Physics Discussion 12, 9491-9516. Joly M. et al. Ice nucleation activity of bacteria isolated from cloud water, accepted in Atmospheric Environment. Vaïtilingom M. et al. (2012) Long-term features of cloud microbiology at the Puy de Dôme (France). Atmospheric Environment 56, 88-100.

  14. Characterization of potential stress responses in ancient Siberian permafrost psychroactive bacteria.

    PubMed

    Ponder, Monica A; Gilmour, Sarah J; Bergholz, Peter W; Mindock, Carol A; Hollingsworth, Rawle; Thomashow, Michael F; Tiedje, James M

    2005-06-01

    Past studies of cold-acclimated bacteria have focused primarily on organisms not capable of sub-zero growth. Siberian permafrost isolates Exiguobacterium sp. 255-15 and Psychrobacter sp. 273-4, which grow at subzero temperatures, were used to study cold-acclimated physiology. Changes in membrane composition and exopolysaccharides were defined as a function of growth at 24, 4 and -2.5 degrees C in the presence and absence of 5% NaCl. As expected, there was a decrease in fatty acid saturation and chain length at the colder temperatures and a further decrease in the degree of saturation at higher osmolarity. A shift in carbon source utilization and antibiotic resistance occurred at 4 versus 24 degrees C growth, perhaps due to changes in the membrane transport. Some carbon substrates were used uniquely at 4 degrees C and, in general, increased antibiotic sensitivity was observed at 4 degrees C. All the permafrost strains tested were resistant to long-term freezing (1 year) and were not particularly unique in their UVC tolerance. Most of the tested isolates had moderate ice nucleation activity, and particularly interesting was the fact that the Gram-positive Exiguobacterium showed some soluble ice nucleation activity. In general the features measured suggest that the Siberian organisms have adapted to the conditions of long-term freezing at least for the temperatures of the Kolyma region which are -10 to -12 degrees C where intracellular water is likely not frozen.

  15. Bioprecipitation: a feedback cycle linking earth history, ecosystem dynamics and land use through biological ice nucleators in the atmosphere.

    PubMed

    Morris, Cindy E; Conen, Franz; Alex Huffman, J; Phillips, Vaughan; Pöschl, Ulrich; Sands, David C

    2014-02-01

    Landscapes influence precipitation via the water vapor and energy fluxes they generate. Biologically active landscapes also generate aerosols containing microorganisms, some being capable of catalyzing ice formation and crystal growth in clouds at temperatures near 0 °C. The resulting precipitation is beneficial for the growth of plants and microorganisms. Mounting evidence from observations and numerical simulations support the plausibility of a bioprecipitation feedback cycle involving vegetated landscapes and the microorganisms they host. Furthermore, the evolutionary history of ice nucleation-active bacteria such as Pseudomonas syringae supports that they have been part of this process on geological time scales since the emergence of land plants. Elucidation of bioprecipitation feedbacks involving landscapes and their microflora could contribute to appraising the impact that modified landscapes have on regional weather and biodiversity, and to avoiding inadvertent, negative consequences of landscape management. © 2013 John Wiley & Sons Ltd.

  16. Three separate classes of bacterial ice nucleation structures.

    PubMed

    Turner, M A; Arellano, F; Kozloff, L M

    1990-05-01

    Studies of the properties of the ice nucleation structure exposed on the surfaces of various bacteria such as Pseudomonas syringae, Erwinia herbicola, or various strains of Ice+ recombinant Escherichia coli have shown that there are clearly three major related but chemically distinct types of structures on these cells. First, the ability of Ice+ cells to nucleate super-cooled D2O has been examined, and it has been found that this ability (relative to the ability of the same cells to nucleate super-cooled H2O) exhibited three characteristic nucleating patterns. The rarest structure, called class A, is found on only a small fraction of cells in a culture, nucleates H2O at temperatures above -4.4 degrees C, and is an effective nucleator of super-cooled D2O. A second class of structure, called class B, is found on a larger portion of the cells, nucleates H2O between -4.8 and -5.7 degrees C, and is a relatively poor nucleator of super-cooled D2O. The class C structure is found on almost all cells and nucleates at -7.6 degrees C or colder. These three classes of structures were also differentiated by their sensitivities to low concentrations of water-miscible organic solvents such as dioxane or dimethyl sulfoxide. Depending on the specific bacterial strain, the addition of these solvents to bacterial suspensions lowered the nucleation activity of the class A structure by 1,000-fold or more. The nucleation activities of class B structures in the same culture were highly resistant to these compounds and were lowered only by 20 to 40%. The class C structures were more sensitive than Class B structures were, and the nucleation activities decreased 70 to 90%. Finally, the pH sensitivity of these three classes of structures was examined. The class A structure was destroyed in buffers at pH 4.5 lower but was stable in buffers at higher pHs. The class B structure was less sensitive to acidic buffers but was destroyed at pH 5.5 or lower and was stable at higher pHs. However, the

  17. Aerosolization of two strains (ice+ and ice-) of Pseudomonas syringae in a Collison nebulizer at different temperatures

    NASA Astrophysics Data System (ADS)

    Pietsch, Renee; David, Ray; Marr, Linsey; Vinatzer, Boris; Schmale, David

    2015-04-01

    The aerosolization of microorganisms from aquatic environments is understudied. In this study, an ice nucleation active (ice+) strain and a non-ice nucleation active (ice-) strain of the bacterium Pseudomonas syringae were aerosolized from aqueous suspensions under artificial laboratory conditions using a Collison nebulizer. The aerosolization of P. syringae was not influenced by water temperatures between 5° and 30°C. In general, the culturability (viability) of P. syringae in aerosols increased with temperature between 5 and 30°C. The ice+ strain was aerosolized in greater numbers than the ice- strain at all temperatures studied, suggesting a possible connection between the ice nucleation phenotype and aerosol production. Together, our results suggest that P. syringae has the potential to be aerosolized from natural aquatic environments, such as streams, rivers, ponds, and lakes; known reservoirs of P. syringae. Future work is needed to elucidate the mechanisms of aerosolization of P. syringae from natural aquatic systems.

  18. Massilia eurypsychrophila sp. nov. a facultatively psychrophilic bacteria isolated from ice core.

    PubMed

    Shen, Liang; Liu, Yongqin; Gu, Zhengquan; Xu, Baiqing; Wang, Ninglian; Jiao, Nianzhi; Liu, Hongcan; Zhou, Yuguang

    2015-07-01

    Strain B528-3(T), a Gram-stain-negative, rod-shaped, aerobic, facultatively psychrophilic bacterium with polar flagella, was isolated from an ice core drilled from Muztagh Glacier, Xinjiang, China. The novel isolate was classified into the genus Massilia. The 16S rRNA gene sequence of the novel isolate shares a pairwise similarity of less than 97% with those of all the type strains of the genus Massilia. The major fatty acids of strain B528-3(T) were summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH) (57.31%), C16:0 (11.46%) and C18:1ω7c (14.72%). The predominant isoprenoid quinone was Q-8. The DNA G + C content was 62.2 mol% (Tm). The major polar lipids of this bacterium were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. From the genotypic and phenotypic data, it is evident that strain B528-3(T) represents a novel species of the genus Massilia, for which the name Massilia eurypsychrophila sp. nov. is proposed. The type strain is B528-3(T) ( = JCM 30074(T) = CGMCC 1.12828(T)).

  19. Subglacial Lake Vostok (Antarctica) Accretion Ice Contains a Diverse Set of Sequences from Aquatic, Marine and Sediment-Inhabiting Bacteria and Eukarya

    PubMed Central

    Edgar, Robyn; Veerapaneni, Ram S.; D’Elia, Tom; Morris, Paul F.; Rogers, Scott O.

    2013-01-01

    Lake Vostok, the 7th largest (by volume) and 4th deepest lake on Earth, is covered by more than 3,700 m of ice, making it the largest subglacial lake known. The combination of cold, heat (from possible hydrothermal activity), pressure (from the overriding glacier), limited nutrients and complete darkness presents extreme challenges to life. Here, we report metagenomic/metatranscriptomic sequence analyses from four accretion ice sections from the Vostok 5G ice core. Two sections accreted in the vicinity of an embayment on the southwestern end of the lake, and the other two represented part of the southern main basin. We obtained 3,507 unique gene sequences from concentrates of 500 ml of 0.22 µm-filtered accretion ice meltwater. Taxonomic classifications (to genus and/or species) were possible for 1,623 of the sequences. Species determinations in combination with mRNA gene sequence results allowed deduction of the metabolic pathways represented in the accretion ice and, by extension, in the lake. Approximately 94% of the sequences were from Bacteria and 6% were from Eukarya. Only two sequences were from Archaea. In general, the taxa were similar to organisms previously described from lakes, brackish water, marine environments, soil, glaciers, ice, lake sediments, deep-sea sediments, deep-sea thermal vents, animals and plants. Sequences from aerobic, anaerobic, psychrophilic, thermophilic, halophilic, alkaliphilic, acidophilic, desiccation-resistant, autotrophic and heterotrophic organisms were present, including a number from multicellular eukaryotes. PMID:23843994

  20. Subglacial Lake Vostok (Antarctica) accretion ice contains a diverse set of sequences from aquatic, marine and sediment-inhabiting bacteria and eukarya.

    PubMed

    Shtarkman, Yury M; Koçer, Zeynep A; Edgar, Robyn; Veerapaneni, Ram S; D'Elia, Tom; Morris, Paul F; Rogers, Scott O

    2013-01-01

    Lake Vostok, the 7(th) largest (by volume) and 4(th) deepest lake on Earth, is covered by more than 3,700 m of ice, making it the largest subglacial lake known. The combination of cold, heat (from possible hydrothermal activity), pressure (from the overriding glacier), limited nutrients and complete darkness presents extreme challenges to life. Here, we report metagenomic/metatranscriptomic sequence analyses from four accretion ice sections from the Vostok 5G ice core. Two sections accreted in the vicinity of an embayment on the southwestern end of the lake, and the other two represented part of the southern main basin. We obtained 3,507 unique gene sequences from concentrates of 500 ml of 0.22 µm-filtered accretion ice meltwater. Taxonomic classifications (to genus and/or species) were possible for 1,623 of the sequences. Species determinations in combination with mRNA gene sequence results allowed deduction of the metabolic pathways represented in the accretion ice and, by extension, in the lake. Approximately 94% of the sequences were from Bacteria and 6% were from Eukarya. Only two sequences were from Archaea. In general, the taxa were similar to organisms previously described from lakes, brackish water, marine environments, soil, glaciers, ice, lake sediments, deep-sea sediments, deep-sea thermal vents, animals and plants. Sequences from aerobic, anaerobic, psychrophilic, thermophilic, halophilic, alkaliphilic, acidophilic, desiccation-resistant, autotrophic and heterotrophic organisms were present, including a number from multicellular eukaryotes.

  1. Role of mineral dust, soot, and bacteria in cloud and precipitation formation processes over Indian subcontinent using an atmospheric general circulation model

    NASA Astrophysics Data System (ADS)

    Hazra, Anupam

    2013-06-01

    An aerosol-type specific heterogeneous nucleation parameterization that based on the classical nucleation theory has been implemented into the atmospheric general circulation model (AGCM), ECHAM5. The microphysical responses in precipitation formation to the variation of ice nuclei (IN) species over Indian subcontinent were analyzed using AGCM, considering the immersion freezing nucleation from mineral dust, dust with ammonium sulfate coating, soot and bacteria species. Immersion freezing by bacteria species is found to be dominating in October-December, whereas dust with ammonium sulfate produces more cloud ice in January-March. There are very little differences in cloud ice formation during April-May and June-September among various IN species. There is also a geographic dependence in the role of different IN species in precipitation formation, like bacteria is important in Southern Peninsula and dust particles play a significant role in central India. In nature the emission of ice nucleating active bacteria and non-biological dust, soot into the atmosphere is important and highly dependent on temperature, and precipitation. So it is the worthy of investigation on the role of different kind of aerosols on the microphysics and precipitation processes, the biosphere-atmosphere interaction and climatic research.

  2. The inhibition of ice nucleators by insect antifreeze proteins is enhanced by glycerol and citrate.

    PubMed

    Duman, J G

    2002-02-01

    Antifreeze proteins depress the freezing point of water while not affecting the melting point, producing a characteristic difference in freezing and melting points termed thermal hysteresis. Larvae of the beetle Dendroides canadensis accumulate potent antifreeze proteins (DAFPs) in their hemolymph and gut, but to achieve high levels of thermal hysteresis requires enhancers, such as glycerol. DAFPs have previously been shown to inhibit the activity of bacterial and hemolymph protein ice nucleators, however, the effect was not large and therefore the effectiveness of the DAFPs in promoting supercooling of the larvae in winter was doubtful. However, this study demonstrates that DAFPs, in combination with the thermal hysteresis enhancers glycerol (1 M) or citrate (0.5 M), eliminated the activity of hemolymph protein ice nucleators and Pseudomonas syringae ice-nucleating active bacteria, and lowered the supercooling points (nucleation temperatures) of aqueous solutions containing these ice nucleators to those of water or buffer alone. This shows that the DAFPs, along with glycerol, play a critical role in promoting hemolymph supercooling in overwintering D. canadensis. Also, DAFPs in combination with enhancers may be useful in applications which require inhibition of ice nucleators.

  3. Laboratory Studies of Ice Nucleation on Volcanic Ash

    NASA Astrophysics Data System (ADS)

    Tolbert, M. A.; Schill, G. P.; Genareau, K. D.

    2014-12-01

    Ice nucleation on volcanic ash controls both ash aggregation and cloud glaciation, which affect human respiratory health, atmospheric transport, and global climate. We have performed laboratory studies of the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman Microscopy coupled to an environmental cell. Ash from the Fuego (Basaltic Ash, Guatemala), Soufriere Hills (Andesetic Ash, Montserrat), and Taupo (Rhyolitic Ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. We find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice at ice saturation ratios of 1.05 ± 0.1. For immersion freezing, however, only the Taupo ash exhibited efficient heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.

  4. Can we define an asymptotic value for the ice active surface site density for heterogeneous ice nucleation?

    NASA Astrophysics Data System (ADS)

    Niedermeier, Dennis; Augustin-Bauditz, Stefanie; Hartmann, Susan; Wex, Heike; Ignatius, Karoliina; Stratmann, Frank

    2015-04-01

    The formation of ice in atmospheric clouds has a substantial influence on the radiative properties of clouds as well as on the formation of precipitation. Therefore much effort has been made to understand and quantify the major ice formation processes in clouds. Immersion freezing has been suggested to be a dominant primary ice formation process in low and mid-level clouds (mixed-phase cloud conditions). It also has been shown that mineral dust particles are the most abundant ice nucleating particles in the atmosphere and thus may play an important role for atmospheric ice nucleation (Murray et al., 2012). Additionally, biological particles like bacteria and pollen are suggested to be potentially involved in atmospheric ice formation, at least on a regional scale (Murray et al., 2012). In recent studies for biological particles (SNOMAX and birch pollen), it has been demonstrated that freezing is induced by ice nucleating macromolecules and that an asymptotic value for the mass density of these ice nucleating macromolecules can be determined (Hartmann et al., 2013; Augustin et al., 2013, Wex et al., 2014). The question arises whether such an asymptotic value can also be determined for the ice active surface site density ns, a parameter which is commonly used to describe the ice nucleation activity of e.g., mineral dust. Such an asymptotic value for ns could be an important input parameter for atmospheric modeling applications. In the presented study, we therefore investigated the immersion freezing behavior of droplets containing size-segregated, monodisperse feldspar particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). For all particle sizes considered in the experiments, we observed a leveling off of the frozen droplet fraction reaching a plateau within the heterogeneous freezing temperature regime (T > -38°C) which was proportional to the particle surface area. Based on these findings, we could determine an asymptotic value for the ice

  5. Ice-active proteins from New Zealand snow tussocks, Chionochloa macra AND C. rigida.

    PubMed

    Wharton, D A; Selvanesan, L; Marshall, C J

    2010-01-01

    The ice active protein profile of New Zealand snow tussocks Chionochloa macra and C. rigida consisted of ice nucleation activity but no antifreeze or recrystallization inhibition activity. The ice nucleation activity was similar in the two species, despite them being collected at different altitudes and at different times. The activity is intrinsic to the plant and is associated with the surface of the leaves. Snow tussocks collect water from fog. Nucleation sites on the surface of their leaves may aid the efficiency of this process.

  6. Bacteria in the Leaf Ecosystem with Emphasis on Pseudomonas syringae—a Pathogen, Ice Nucleus, and Epiphyte

    PubMed Central

    Hirano, Susan S.; Upper, Christen D.

    2000-01-01

    The extremely large number of leaves produced by terrestrial and aquatic plants provide habitats for colonization by a diversity of microorganisms. This review focuses on the bacterial component of leaf microbial communities, with emphasis on Pseudomonas syringae—a species that participates in leaf ecosystems as a pathogen, ice nucleus, and epiphyte. Among the diversity of bacteria that colonize leaves, none has received wider attention than P. syringae, as it gained notoriety for being the first recombinant organism (Ice− P. syringae) to be deliberately introduced into the environment. We focus on P. syringae to illustrate the attractiveness and somewhat unique opportunities provided by leaf ecosystems for addressing fundamental questions of microbial population dynamics and mechanisms of plant-bacterium interactions. Leaf ecosystems are dynamic and ephemeral. The physical environment surrounding phyllosphere microbes changes continuously with daily cycles in temperature, radiation, relative humidity, wind velocity, and leaf wetness. Slightly longer-term changes occur as weather systems pass. Seasonal climatic changes impose still a longer cycle. The physical and physiological characteristics of leaves change as they expand, mature, and senesce and as host phenology changes. Many of these factors influence the development of populations of P. syringae upon populations of leaves. P. syringae was first studied for its ability to cause disease on plants. However, disease causation is but one aspect of its life strategy. The bacterium can be found in association with healthy leaves, growing and surviving for many generations on the surfaces of leaves as an epiphyte. A number of genes and traits have been identified that contribute to the fitness of P. syringae in the phyllosphere. While still in their infancy, such research efforts demonstrate that the P. syringae-leaf ecosystem is a particularly attractive system with which to bridge the gap between what is known

  7. [Phylogenetic diversity and cold-adaptive hydrolytic enzymes of culturable psychrophilic bacteria associated with sea ice from high latitude ocean, Artic].

    PubMed

    Yu, Yong; Li, Hui-Rong; Chen, Bo; Zeng, Yin-Xin; He, Jian-Feng

    2006-04-01

    The phylogenetic diversity of culturable psychrophilic bacteria associated with sea ice from high latitude sea (77 degrees 30'N - 81 degrees 12'N), Canadian Basin and Greenland sea Arctic, was investigated. A total of 37 psychrophilic strains were isolated using three different methods of ( i ) spread plate method: 100 microL of each dilution ice-melt sample was spreaded onto the surface of Marine 2216 agar (DIFCO laboratories, Detroit, MI) and incubated for 2 to 6 weeks at 4 degrees C; ( ii ) bath culture and spread plate method: 1 mL of sample was added to 9mL of NSW (unamended natural seawater, 0.2 microm prefiltered and autoclaved) and incubated for 1 months at - 1 degrees C, then spread plate method was used to isolate bacterial strains from the pre-cultured samples; ( iii ) cold shock, bath culture and spread plate method: samples were exposed to - 20 degrees C for 24h, then bacterial strains isolated by bath culture and spread plate method under aerobic conditions. Nearly half of psychrophilic strains are isolated by using method iii . 16S rDNA nearly full-length sequence analysis reveal that psychrophilic strains fall in two phylogenetic divisions, gamma-proteobacteria (in the genera Colwellia, Marinobacter, Shewanella, Thalassomonas, Glaciecola, Marinomonas and Pseudoalteromonas) and Cytophaga-Flexibacter-Bacteroides (in the genera Flavobacterium and Psychroflexus). Nine of bacterial isolates (BSi20007, BSi20497, BSi20517, BSi20537, BSi20170, BSi20001, BSi20002, BSi20675 and BSi20101) quite likely represent novel species (16S rDNA sequence similarity below 97%). One of strains (BSi20002) from Canadian Basin shows 100% sequence similarity to the Antarctic Weddell sea ice isolate Marinobacter sp. ANT8277, suggesting bacteria may have a bipolar distribution at the species level. AF283859 sequences were submitted to the BLAST search program of the National Center for Biotechnology Information website (NCBI, http://www. ncbi. nlm.nih. gov). Twenty sequences

  8. Biogenic ice nuclei in boundary layer air over two U.S. High Plains agricultural regions

    NASA Astrophysics Data System (ADS)

    Garcia, Elvin; Hill, Thomas C. J.; Prenni, Anthony J.; Demott, Paul J.; Franc, Gary D.; Kreidenweis, Sonia M.

    2012-09-01

    With 18% of the total U.S. landmass devoted to croplands, farmland and farming activities are potentially major sources of biogenic particles to the atmosphere. Farms harbor large populations of microbes both in the soil and on plant surfaces which, if injected into the atmosphere, may serve as nuclei for clouds. In this study, we investigated two farms as potential sources of biological ice nuclei (IN): an organic farm in Colorado and a cornfield in Nebraska. We used a continuous-flow diffusion chamber (CFDC) to obtain real-time measurements of IN at these farm sites. Total aerosol particles were also collected at the sites, and their temperature-dependent ice nucleating activity was determined using the drop freezing method. Quantitative polymerase chain reaction and DNA sequencing of 16S rDNA clone libraries were used to test aerosols and washings of local vegetation for abundance of theinagene in ice nucleation active bacteria (from the well-known group within theγ-Proteobacteria) and to identify airborne primary biological aerosol particles. The vegetation in each of these farms contained 6 × 105 to 2 × 107 ina genes per gram vegetation. In contrast to the vegetation, airborne ina gene concentrations at the organic farm were typically below detectable limits, demonstrating a disconnect between local vegetative sources and the air above them. However, for measurements made during combine harvesting at the Nebraska corn field, ina gene concentrations were 19 L-1, with maximum IN concentrations of 50 L-1 determined from the CFDC at -20°C and above water saturation. At both farms, there was also an apparent biological contribution to the IN population which did not contain the ina gene.

  9. Biofilm, ice recrystallization inhibition and freeze-thaw protection in an epiphyte community.

    PubMed

    Wu, Z; Kan, F W K; She, Y-M; Walker, V K

    2012-01-01

    Microbial communities found on the surface of overwintering plants may be exposed to low temperatures as well as multiple freeze-thaw events. To explore the adaptive mechanisms of these epiphytes, with the objective of identifying products for freeze-protection, enrichment libraries were made from frost-exposed leaves. Of 15 identified bacteria from 60 individual clones, approximately half had ice-association activities, with the great majority showing high freeze-thaw resistance. Isolates with ice nucleation activity and ice recrystallization inhibition activity were recovered. Of the latter, two (Erwinia billingiae J10, and Sphingobacterium kitahiroshimense Y2) showed culture and electron microscopic evidence of motility and/or biofilm production. Mass spectrometric characterization of the E. billingiae extracellular polymeric substance (EPS) identified the major proteins as 35 kDa outer membrane protein A and F, supporting its biofilm character. The addition of the EPS preparation increased the freeze-thaw survival of the more susceptible bacteria 1000-10000 times, and protection was at least partially dependent on the protein component.

  10. Ice Nuclei Emissions From Sea Spray Produced By Realistically Simulated Breaking Waves

    NASA Astrophysics Data System (ADS)

    Sullivan, R. C.; DeMott, P. J.; Ruppel, M. J.; Franc, G.; Hill, T.; Collins, D. B.; Cuadra-Rodriguez, L. A.; Guasco, T.; Kim, M. J.; Ault, A. P.; Grassian, V. H.; Prather, K. A.

    2012-12-01

    Breaking waves were used to generate realistic sea spray aerosol in the laboratory for the first time to study the chemical and cloud nucleation properties of marine-derived particles. Ice nuclei (IN) concentrations were measured online from the large wave channel, and from a smaller wave tank, during the collaborative CAICE experiment at Scripps Institution of Oceanography. These represent the first such measurements of ice nucleation isolated to sea spray aerosol under controlled but realistic laboratory conditions. The wave channel and small wave tank were filled with coarsely filtered sea water pumped from the nearby Pacific Ocean. Various types of bacteria, phytoplankton, and/or algae were added to the tanks to simulate marine biology. In a multiday mesocosm experiment, growth media was also added to stimulate a marine bloom event. Ice nuclei concentrations were strongly dependent on the cloud processing temperature, and required a combination of both online and higher sample volume offline collection methods to successfully characterize IN concentrations at the warmest ice nucleation temperatures. A clear relation between ice nuclei concentrations at lower temperatures below -30 °C and heterotrophic bacteria concentrations in the seawater was found. The IN concentration was also impaired by increasing concentrations of total organic carbon. IN did not correlate with chlorophyll concentrations, though this is the indicator typically used to predict changes in ocean biology and chemistry and the resulting alteration of sea spray aerosol properties. Spectromicroscopic analysis of collected ice crystals was used to investigate what particle compositions were likely responsible for the observed ice nucleation activity. These measurements suggest characteristic ice nuclei activation at lower average temperatures than typically observed for Northern Hemisphere ambient aerosols. The marine bio-particles observed here displayed weaker ice nucleation ability than

  11. Ice Nucleation of Snomax® Particles below Water Vapor Saturation: Immersion Freezing in Concentrated Solution Droplets

    NASA Astrophysics Data System (ADS)

    Kanji, Z. A.; Boose, Y.; Augustin, S.; Wex, H.

    2014-12-01

    Heterogeneous ice nucleation in the atmosphere is important and has received an increasing amount of interest in the past years, as it initiates the ice phase in mixed phase clouds and, to some extent, also in cirrus clouds. The presence of ice influences cloud radiative properties and, for mixed phase clouds, also the formation of precipitation and cloud lifetime. Immersion freezing has been in the focus of ice nucleation research in recent years. Here, we examine ice nucleation activity of biological ice nuclei (IN) derived from bacteria, namely of particles generated from a suspensions of Snomax®, both above and below water vapor saturation. Measurements were done with PINC (Portable Ice Nucleus Counter, Chou et al., 2011) during a measurement campaign at LACIS (Leipzig Aerosol Cloud Interaction Simulator, see e.g. Wex et al., 2014) in Leipzig. Immersion freezing measurements from PINC and LACIS were in agreement in the temperature regime for which both instruments operate reliably. Here, we will show that measurements done below water vapor saturation follow what would be expected for immersion freezing in concentrated solutions, similar to what was suggested for coated kaolinite particles in Wex et al. (2014). Chou, C., O. Stetzer, E. Weingartner, Z. Juranyi, Z. A. Kanji, and U. Lohmann (2011), Ice nuclei properties within a Saharan dust event at the Jungfraujoch in the Swiss Alps, Atmos. Chem. Phys., 11(10), 4725-4738, doi:10.5194/acp-11-4725-2011. Wex, H., P. J. DeMott, Y. Tobo, S. Hartmann, M. Rösch, T. Clauss, L. Tomsche, D. Niedermeier, and F. Stratmann (2014), Kaolinite particles as ice nuclei: learning from the use of different kaolinite samples and different coatings, Atmos. Chem. Phys., 14, doi:10.5194/acp-14-5529-2014.

  12. High saturated fatty acids proportion in Escherichia coli enhances the activity of ice-nucleation protein from Pantoea ananatis.

    PubMed

    Yu, Feifei; Liu, Xiping; Tao, Yong; Zhu, Kun

    2013-08-01

    The ice-nucleation protein (INP) from Pantoea ananatis was expressed in Escherichia coli. INP expression increased the freezing point of the E. coli culture by a few degrees. Deletion of FabH, an important enzyme in fatty acid biosynthesis, significantly inhibited the ice-nucleation activity. Increased unsaturated fatty acids in the fabH mutant cells decreased the ice-nucleation activity. Adding exogenous saturated fatty acids increased both E. coli fatty acid saturation and the ice-nucleation activity. In contrast, adding unsaturated fatty acids exhibited the opposite effects. Furthermore, an E. coli MG1655-fadR strain with high saturated fatty acids content was constructed, in which the INP activity was enhanced by about 17% compared with its activity in the wild-type MG1655 strain.

  13. Oxidation stability of ice nuclei from plants

    NASA Astrophysics Data System (ADS)

    Felgitsch, Laura; Häusler, Thomas; Grothe, Hinrich

    2017-04-01

    Heterogeneous ice nucleation is an important process in cloud formation and therefore has direct influence on the radiation budget of the Earth. Biological ice nuclei (IN) are highly abundant in nature. Many plants have been found to produce IN. These IN are of special interest, since several have been found to be in a nano-particular/macromolecular size range (Pummer et al. 2015, Felgitsch et al. 2016). Particles of such a small size should show a high lifespan in the atmosphere. Further the substances can easily be attached to mineral dusts. Very little is known about the atmospheric fate of plant derived ice nuclei (IN) in case they become airborne. While they inherit the possibility to influence ice cloud formation, this property depends highly on the expected lifespan of the substance and of its ice nucleation activity in the atmosphere. For our experiment we exposed plant IN derived from black currant (berry juice) and birch (pollen washing water) to high concentrations of highly oxidative substances typically present in the atmosphere. The exposure lasted several hours and allowed us to monitor the changes in ice nucleation activity. Our results suggest a high stability towards oxidation leading to a high atmospheric life span of the ice nucleation activity if airborne. Pummer, B.G., Budke, C., Augustin-Bauditz, S., Niedermeier, D., Felgitsch, L., Kampf, C.J., Huber, R.G., Liedl, K.R., Loerting, T., Moschen, T., Schauperl, M., Tollinger, M., Morris, C.E., Wex, H., Grothe, H., Pöschl, U., Koop, T., and Fröhlich-Nowoisky, J.: Ice nucleation by water-soluble macromolecules, Atmos. Chem. Phys., 15, 4077-4091, 2015. Felgitsch , L., Bichler, M., Häusler, T., Hitzenberger, R., and Grothe, H.: Heterogeneous freezing of water triggered by berry juices from perenneal plants, submitted, 2016.

  14. Cloud condensation nucleation activity of secondary organic aerosols formed from the oxidation of alkenes and diiodomethane

    NASA Astrophysics Data System (ADS)

    Petters, M. D.; Faulhaber, A.; Prenni, A. J.; Carrico, C. M.; Sullivan, R. C.; Demott, P. J.; Kreidenweis, S. M.; Ziemann, P. J.

    2009-12-01

    Recent measurements have shown that marine aerosol contains a significant fraction of organic compounds. The sources for these compounds are not yet completely understood, but are thought to be a mix of primary emissions and secondary organic aerosol (SOA) formation. Reactive alkenes with low carbon numbers (C5 and C6) and halogenated hydrocarbons emitted from phytoplankton are commonly suggested precursors. These compounds can contribute to new particle formation events and can lead to subsequent growth into the accumulation mode size range. We conducted measurements of the cloud condensation nuclei (CCN) and ice nuclei activity of SOA that was formed from the oxidation of linear, branched, and cyclic alkenes, as well as from diiodomethane. Aerosol forming reactions were carried out in a PTFE environmental chamber, involving oxidation of the precursors mostly with O3 and, for a select number of precursors, oxidation with OH in the absence of NOx. We also performed experiments on single component aerosols generated from the atomization of aqueous solutions, targeting polyalcohols commonly associated with isoprene oxidation products. Ice nucleation experiments were performed only for the O3 reactions and ice nuclei were not observed in detectable quantities for this subset of systems. From our experiments we found that CCN activity generally decreases with the precursor carbon number. When expressed as hygroscopicity parameter (kappa), CCN activity ranged from kappa ~ 0.15 to kappa 0, spanning the range from moderately CCN active to CCN inactive at atmospherically relevant sizes and supersaturations, respectively.

  15. Progress Towards Identifying and Quantifying the Organic Ice Nucleating Particles in Soils and Aerosols

    NASA Astrophysics Data System (ADS)

    Hill, T. C. J.; DeMott, P. J.; Fröhlich-Nowoisky, J.; Tobo, Y.; Suski, K. J.; Levin, E. J.; Kreidenweis, S. M.; Franc, G. D.

    2014-12-01

    Soil and plant surfaces emit ice nucleating particles (INP) to the atmosphere, especially when disturbed by wind, harvesting, rain or fire. Organic (biogenic) INP are abundant in most soils and dominate the population that nucleate >-15°C. For example, the sandy topsoil of sagebrush shrubland, a widespread ecotype prone to wind erosion after fire, contains ~106 organic INP g-1 at -6°C. The relevance of organic INP may also extend to colder temperatures than previously thought: Particles of soil organic matter (SOM) have been shown to be more important than mineral particles for the ice nucleating ability of agricultural soil dusts to -34°C. While the abundance of ice nucleation active (INA) bacteria on plants has been established, the identity of the organic INP in and emitted by soils remains a 40-year-old mystery. The need to understand their production and release is highlighted by recent findings that INA bacteria (measured with qPCR) account for few, if any, of the warm-temperature organic INP that predominate in boundary layer aerosols and snow; organic INP lofted with soil dusts seem a likely source. The complexity of SOM hinders its investigation. It contains decomposing plant materials, a diverse microbial and microfaunal community, humus, and inert organic matter. All are biochemically complex and all may contain ice nucleating constituents, either by design or by chance. Indeed the smoothness of the INP temperature spectra of soils is indicative of numerous, overlapping distributions of INP. We report recent progress in identifying and quantifying the organic INP in soils and boundary layer aerosols representative of West Central U.S. ecosystems, and how their characteristics may affect their dispersal. Chemical, enzymatic and DNA-based tests were used to assess contributions of INP from plant tissues, INA bacteria, INA fungi, organic crystals, monolayers of aliphatic alcohols, carbohydrates, and humic substances, while heat- and peroxide-based tests

  16. Ice-Active Substances from the Infective Juveniles of the Freeze Tolerant Entomopathogenic Nematode, Steinernema feltiae.

    PubMed

    Ali, Farman; Wharton, David A

    2016-01-01

    Steinernema feltiae is a moderately freezing tolerant nematode, that can withstand intracellular ice formation. We investigated recrystallization inhibition, thermal hysteresis and ice nucleation activities in the infective juveniles of S. feltiae. Both the splat cooling assay and optical recrystallometry indicate the presence of ice active substances that inhibit recrystallization in the nematode extract. The substance is relatively heat stable and largely retains the recrystallization inhibition activity after heating. No thermal hysteresis activity was detected but the extract had a typical hexagonal crystal shape when grown from a single seed crystal and weak ice nucleation activity. An ice active substance is present in a low concentration, which may be involved in the freezing survival of this species by inhibiting ice recrystallization.

  17. Ice-Active Substances from the Infective Juveniles of the Freeze Tolerant Entomopathogenic Nematode, Steinernema feltiae

    PubMed Central

    Ali, Farman; Wharton, David A.

    2016-01-01

    Steinernema feltiae is a moderately freezing tolerant nematode, that can withstand intracellular ice formation. We investigated recrystallization inhibition, thermal hysteresis and ice nucleation activities in the infective juveniles of S. feltiae. Both the splat cooling assay and optical recrystallometry indicate the presence of ice active substances that inhibit recrystallization in the nematode extract. The substance is relatively heat stable and largely retains the recrystallization inhibition activity after heating. No thermal hysteresis activity was detected but the extract had a typical hexagonal crystal shape when grown from a single seed crystal and weak ice nucleation activity. An ice active substance is present in a low concentration, which may be involved in the freezing survival of this species by inhibiting ice recrystallization. PMID:27227961

  18. Modelling the impact of fungal spore ice nuclei on clouds and precipitation

    NASA Astrophysics Data System (ADS)

    Sesartic, Ana; Lohmann, Ulrike; Storelvmo, Trude

    2013-04-01

    Fungal spores are part of the atmospheric bioaerosols such as pollen or bacteria. Interest in bioaerosols is mainly related to their health effects, impacts on agriculture, ice nucleation and cloud droplet activation, as well as atmospheric chemistry (Morris et al. 2011). Spores of some fungal species have been found to be very efficient ice nuclei, e.g. in laboratory studies by Pouleur et al. (1992). Recent field studies by Poehlker et al. (2012) found that fungal spores are important contributors to the development of mist and clouds in rainforest ecosystems. In our study we investigated the impact of fungal spores acting as ice nuclei on clouds and precipitation on a global scale. Fungal spores as a new aerosol species were introduced into the global climate model ECHAM5-HAM (Sesartic et al. 2012) using observational fungal spore data compiled by Sesartic & Dallafior (2011). The addition of fungal spores lead to only minor changes in cloud formation and precipitation on a global level, however, changes in the liquid water path and ice water path as well as stratiform precipitation in the model were observed in the boreal regions where tundra and forests act as sources of fungal spores. This goes hand in hand with a decreased ice crystal number concentration and increased effective radius of ice crystals. An increase in stratiform precipitation and snowfall can be observed in those regions as well. Although fungal spores contribute to heterogeneous freezing, their impact in the model was reduced by their low numbers compared to other heterogeneous ice nuclei. These results for fungal spores are comparable to the ones achieved with bacteria (Sesartic et al. 2012). REFERENCES Morris, C. E. et al. 2011: Microbiology and atmospheric processes: research challenges concerning the impact of airborne micro-organisms on the atmosphere and climate, Biogeosciences, 8, 17-25. Poehlker, C. et al. 2012: Biogenic Potassium Salt Particles as Seeds for Secondary Organic Aerosol

  19. Niche specialization of bacteria in permanently ice-covered lakes of the McMurdo Dry Valleys, Antarctica.

    PubMed

    Kwon, Miye; Kim, Mincheol; Takacs-Vesbach, Cristina; Lee, Jaejin; Hong, Soon Gyu; Kim, Sang Jong; Priscu, John C; Kim, Ok-Sun

    2017-03-09

    Perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica, are chemically stratified with depth and have distinct biological gradients. Despite long-term research on these unique environments, data on the structure of the microbial communities in the water columns of these lakes are scarce. Here, we examined bacterial diversity in five ice-covered Antarctic lakes by 16S rRNA gene-based pyrosequencing. Distinct communities were present in each lake, reflecting the unique biogeochemical characteristics of these environments. Further, certain bacterial lineages were confined exclusively to specific depths within each lake. For example, candidate division WM88 occurred solely at a depth of 15 m in Lake Fryxell, whereas unknown lineages of Chlorobi were found only at a depth of 18 m in Lake Miers, and two distinct classes of Firmicutes inhabited East and West Lobe Bonney at depths of 30 m. Redundancy analysis revealed that community variation of bacterioplankton could be explained by the distinct conditions of each lake and depth; in particular, assemblages from layers beneath the chemocline had biogeochemical associations that differed from those in the upper layers. These patterns of community composition may represent bacterial adaptations to the extreme and unique biogeochemical gradients of ice-covered lakes in the McMurdo Dry Valleys. This article is protected by copyright. All rights reserved.

  20. Microbial production of ice crystals in clouds as a novel atmospheric biosignature

    NASA Astrophysics Data System (ADS)

    Santl-Temkiv, T.; Sahyoun, M.; Kjeldsen, H.; Ling, M.; Boesen, T.; Karlson, U. G.; Finster, K.

    2014-03-01

    A diverse assembly of exoplanets has been discovered during recent decades (Howard 2013), their atmospheres providing some of the most accessible evidence for the presence of biological activity on these planets. Metabolic gases have been commonly proposed as atmospheric biosignatures (Seager et al 2012). However, airborne microbes are also involved in cloud- and precipitation formation on Earth. Thus, meteorological phenomena may serve as alternative atmospheric biosignatures, for which appropriate observational techniques have yet to be developed. The atmospheric part of the Earth's water cycle heavily relies on the presence of nucleating particles, which promote the condensation and freezing of atmospheric water, both potentially leading to precipitation. While cloud condensation nuclei are diverse and relatively common, ice nuclei are poorly understood and comparably rare airborne particles. According to current knowledge, most ice nucleation below ñ15∞C is driven by the presence of inorganic dust particles, which are considered inactive at higher temperatures. Biogenic IN are the only reported particles that promote ice formation above ñ10∞C. Some bacteria, e.g. Pseudomonas syringae, produce Ice Nucleation Active (INA) proteins that are most efficient ice nuclei currently known. These INA bacteria are common in the atmosphere, and may thus be involved in precipitation processes of mixed phase clouds (Möhler et al 2007). We investigate the relevance of bacterial INA proteins for atmospheric processes using three approaches: (i) study of the presence of INA bacteria and their INA proteins in the atmosphere, (ii) a detailed molecular and physical study of isolated INA proteins, and finally (iii) a modeling study of the importance of INA proteins for ice-path in clouds as well as their importance for precipitation. During 14 precipitation events, we observed that 12% of isolated bacteria carried INA genes. INA bacteria had likely been emitted to the

  1. Ice nucleation of Snomax® particles below water vapor saturation: immersion freezing in concentrated solution droplets

    NASA Astrophysics Data System (ADS)

    Wex, Heike; Kanji, Zamin A.; Boose, Yvonne; Beyer, Alexander; Henning, Silvia; Augustin-Bauditz, Stefanie

    2015-04-01

    Heterogeneous ice nucleation has received an increasing amount of interest in the past years, as it initiates the ice phase in mixed phase clouds (MPCs) and, to some extent, also in cirrus clouds. The presence of ice influences cloud radiative properties and, for mixed phase clouds, also the formation of precipitation. Immersion freezing is thought to be the most important mechanism through which ice formation could take place in MPCs. Here, we examine the ice nucleation activity of biological ice nucleating particles (INP) derived from bacteria, namely, particles generated from Snomax® suspensions, both above and below water vapor saturation. During a measurement campaign in Leipzig, ice nucleation measurements were conducted with PINC (Portable Ice Nucleus Counter, Chou et al., 2011) and LACIS (Leipzig Aerosol Cloud Interaction Simulator, see e.g. Wex et al., 2014a). Immersion freezing measurements from PINC and LACIS were in agreement in the temperature regime for which both instruments operate reliably. Here, we will show that measurements done below water vapour saturation and above the deliquescence relative humidity of the Snomax® particles follow what would be expected for immersion freezing in concentrated solutions, similar to what was suggested for coated kaolinite particles in Wex et al. (2014b). Additionally, some measurements reported in the literature that were done in the water vapour sub-saturated regime will be evaluated based on the assumption made above, showing that at least some of the ice nucleation which previously was ascribed to deposition ice nucleation rather follows the behavior of immersion freezing in concentrated solutions. Literature: Chou, C., O. Stetzer, E. Weingartner, Z. Juranyi, Z. A. Kanji, and U. Lohmann (2011), Ice nuclei properties within a Saharan dust event at the Jungfraujoch in the Swiss Alps, Atmos. Chem. Phys., 11(10), 4725-4738, doi:10.5194/acp-11-4725-2011. Wex, H. et al. (2014a) Intercomparing different devices

  2. An ice nucleation reporter gene system: identification of inducible pathogenicity genes in Pseudomonas syringae pv. phaseolicola.

    PubMed Central

    Lindgren, P B; Frederick, R; Govindarajan, A G; Panopoulos, N J; Staskawicz, B J; Lindow, S E

    1989-01-01

    We have constructed derivatives of the transposon Tn3 that allow an ice nucleation gene (inaZ) to be used as 'reporter' of the transcriptional activity of genes into which it is inserted. In these derivatives (Tn3-Ice and Tn3-Spice), the lacZYA sequences of transposon Tn3-HoHo1 were replaced with inaZ lacking its native promoter. The ice nucleation activity of virB::inaZ fusions in the correct transcriptional orientation was inducible by acetosyringone, a plant metabolite which activates the vir operon of Agrobacterium tumefaciens Ti plasmids, while fusions in the opposite orientation were unresponsive to the inducer. Tn3-Spice was also used to investigate the expression of a cluster of genes (hrp) which control pathogenicity and hypersensitivity elicited by Pseudomonas syringae pv. phaseolicola. An inducible region was identified which is expressed at low levels in vitro but becomes activated when the bacteria come into contact with the susceptible host, bean. Activation of this region occurred within 2 h post-inoculation and was nearly complete by the time the bacteria began to multiply in the leaf tissue. The inaZ reporter appears to be at least 10(5)-fold more sensitive than lacZ in P.s.phaseolicola. Thus, the inaZ fusion system provides a sensitive, convenient and inexpensive tool for the study of bacterial gene expression, particularly during plant pathogenesis, and should be generally useful as a reporter gene system in Gram-negative bacteria. PMID:2548841

  3. Heterogeneous ice nucleation on dust particles sourced from nine deserts worldwide - Part 1: Immersion freezing

    NASA Astrophysics Data System (ADS)

    Boose, Yvonne; Welti, André; Atkinson, James; Ramelli, Fabiola; Danielczok, Anja; Bingemer, Heinz G.; Plötze, Michael; Sierau, Berko; Kanji, Zamin A.; Lohmann, Ulrike

    2016-12-01

    Desert dust is one of the most abundant ice nucleating particle types in the atmosphere. Traditionally, clay minerals were assumed to determine the ice nucleation ability of desert dust and constituted the focus of ice nucleation studies over several decades. Recently some feldspar species were identified to be ice active at much higher temperatures than clay minerals, redirecting studies to investigate the contribution of feldspar to ice nucleation on desert dust. However, so far no study has shown the atmospheric relevance of this mineral phase.For this study four dust samples were collected after airborne transport in the troposphere from the Sahara to different locations (Crete, the Peloponnese, Canary Islands, and the Sinai Peninsula). Additionally, 11 dust samples were collected from the surface from nine of the biggest deserts worldwide. The samples were used to study the ice nucleation behavior specific to different desert dusts. Furthermore, we investigated how representative surface-collected dust is for the atmosphere by comparing to the ice nucleation activity of the airborne samples. We used the IMCA-ZINC setup to form droplets on single aerosol particles which were subsequently exposed to temperatures between 233 and 250 K. Dust particles were collected in parallel on filters for offline cold-stage ice nucleation experiments at 253-263 K. To help the interpretation of the ice nucleation experiments the mineralogical composition of the dusts was investigated. We find that a higher ice nucleation activity in a given sample at 253 K can be attributed to the K-feldspar content present in this sample, whereas at temperatures between 238 and 245 K it is attributed to the sum of feldspar and quartz content present. A high clay content, in contrast, is associated with lower ice nucleation activity. This confirms the importance of feldspar above 250 K and the role of quartz and feldspars determining the ice nucleation activities at lower temperatures as found

  4. Characterizing Ice Nucleating Particles Emitted from Agricultural Activities and Natural Landscapes

    NASA Astrophysics Data System (ADS)

    Suski, K. J.; Levin, E. J.; DeMott, P. J.; Kreidenweis, S. M.; Hill, T. C. J.

    2015-12-01

    Soil dust and plant fragment emissions from agricultural harvesting and natural ecosystems are two potentially large, yet unquantified and largely uncharacterized, sources of ice nucleating particles (INPs). Both organic and mineral components have been shown to contribute to the ice-nucleating ability of soil dust, but apart from the likely presence of ice nucleation-active bacteria, little is known about the ice nucleating potential of plant tissues. This work aims to identify and differentiate the organic and inorganic contributions of soil and plant INP sources emitted from harvesting activities and natural landscapes. For this purpose, the CSU Continuous Flow Diffusion Chamber (CFDC) and the Ice Spectrometer (IS) were utilized in a combination of ambient measurements and laboratory studies. Small variability and low INP numbers (< 10 L-1 at -30 °C) characterized measurements made in air over the grazed Pawnee National Grassland in Colorado, while more variable INP over croplands around the DOE-ARM SGP site in Oklahoma appear linked to regional wind, humidity, and rainfall conditions. Harvesting of milo (grain sorghum), soybean, and wheat at an experimental research farm in Kansas resulted in spikes of INPs, with wheat harvesting producing the largest INP concentrations (up to 100 L-1 at -30 °C). In-situ use of heating tubes upstream of the CFDC to deactivate organic INP showed that milo and wheat harvest emissions showed a stronger reduction of INPs at warm temperatures than soybean emissions, suggesting a larger contribution of organics to their INP activity. Further characterization of the sources and organic and inorganic contributions to terrestrially emitted INPs by comparison to laboratory studies on collected soil dust and plant samples will also be presented.

  5. Bacteria and viruses of the ice-free aquatic area of the Barents Sea at the beginning of polar night.

    PubMed

    Shirokolobova, T I; Zhichkin, A P; Venger, M P; Vodopyanova, V V; Moiseev, D V

    2016-07-01

    The most massive components of the microplankton were studied in the open sea waters for the first time at the end of the autumn season. It has been found that abundance of the virio- and bacterioplankton exceeded that observed in winter in the coastal zone. Against the background of a relatively uniform distribution of bacteria, the viral abundance and the lysis-mediated bacterioplankton death rate reached the maximum values in the most cold and salty waters of the northern sea areas.

  6. Variations of ice nuclei concentration induced by rain and snowfall within a local forested site in Japan

    NASA Astrophysics Data System (ADS)

    Hara, Kazutaka; Maki, Teruya; Kobayashi, Fumihisa; Kakikawa, Makiko; Wada, Masashi; Matsuki, Atsushi

    2016-02-01

    Biological ice nuclei (IN) such as certain species of bacteria and fungi are believed to have impacts on ice nucleation in mixed-phase clouds at temperatures warmer than -15 °C. Recent studies have indicated that rain is closely related to increases of biological IN in the near-surface atmosphere. However, variations of IN concentrations during rain and snowfall have not been compared. In the present study, field measurements of atmospheric IN were carried out under fine, cloudy, rain and snow at a local forested site in Japan. IN concentrations at -7 °C in spring were dramatically increased by rain, and concentrations associated with rain (0.86-2.2 m-3) were greater than 2.6 times higher than the mean concentration during fine weather (0.33 m-3). In winter, concentrations associated with rain (1.6 to >5.7 m-3) were also higher than those under cloudy sky (1.1 m-3), but increases were not observed during snowfall (0.21-0.4 m-3). Detectable IN concentrations associated with rain considerably decreased after heat treatment at 90 °C, indicating that IN increased during rain were likely biological substances such as heat-sensitive ice nucleation active proteins. Consequently, different types of precipitation may have varying effects on IN concentration associated with biological substances.

  7. Laboratory studies with cloud-derived Bacterial Cells acting as Ice Nuclei in the Immersion and Deposition Mode

    NASA Astrophysics Data System (ADS)

    Oehm, C.; Chou, C.; Amato, P.; Attard, E.; Delort, A.-M.; Morris, C.; Kiselev, A.; Stetzer, O.; Möhler, O.; Leisner, T.

    2012-04-01

    Atmospheric aerosol particles play an important role in cloud microphysics. Aerosols of biological origin are a subgroup, and some of them are able to act as heterogeneous ice nuclei and thus influence cloud life cycles and the climate. Some bacteria species have been found to act as ice nuclei at relatively high temperatures up to -2 degree Celsius and are therefore of particular importance as "high temperature" ice nuclei. Recently, ice nucleation experiments with bacterial cells from different sources were performed at the aerosol and cloud simulation chamber AIDA at the Karlsruhe Institute of Technology. At the AIDA facility, microphysical cloud processes can be simulated and investigated in laboratory at realistic atmospheric cloud conditions. Different ice nucleation active (INA) bacteria strains were isolated from cloud water, glacier melt water and phyllosphere and examined in AIDA experiments. The living cells were suspended in nanopure or artificial cloud water and injected into the cloud chamber through a dispersion nozzle. The injected droplets evaporated in the chamber and the bacterial cells were transformed into the aerosol phase. After the spraying, the cloud formation was started by expansion cooling. Experiments were performed in the temperature range from -2 down to -20 degree Celsius. Detailed measurements of the number concentration and size distribution of the aerosol particles as well as of the droplets and ice particles were carried out during the AIDA experiments. A minor fraction of the bacteria cells was observed to act as ice nuclei in the immersion nucleation mode at higher temperatures as well as in the deposition nucleation mode at lower temperatures. The ice activity started at -6 degree Celsius. The most efficient INA bacteria species were Pseudomonas syringae 32b74 and Pseudomonas fluorescens Antarctica1. The ice active number fraction with respect to the cells varied from 0,01 to 0,1, and it does not change at different

  8. Sea Ice Ecosystems

    NASA Astrophysics Data System (ADS)

    Arrigo, Kevin R.

    2014-01-01

    Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters.

  9. Sea ice ecosystems.

    PubMed

    Arrigo, Kevin R

    2014-01-01

    Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters.

  10. New species of ice nucleating fungi in soil and air

    NASA Astrophysics Data System (ADS)

    Fröhlich-Nowoisky, Janine; Hill, Thomas C. J.; Pummer, Bernhard G.; Franc, Gray D.; Pöschl, Ulrich

    2014-05-01

    Primary biological aerosol particles (PBAP) are ubiquitous in the atmosphere (1,2). Several types of PBAP have been identified as ice nuclei (IN) that can initiate the formation of ice at relatively high temperatures (3, 4). The best-known biological IN are common plant-associated bacteria. The IN activity of these bacteria is due to a surface protein on the outer cell membrane that catalyses ice formation, for which the corresponding gene has been identified and detected by DNA analysis (3). Fungal spores or hyphae can also act as IN, but the biological structures responsible for their IN activity have not yet been elucidated. Furthermore, the abundance, diversity, sources, seasonality, properties, and effects of fungal IN in the atmosphere have neither been characterized nor quantified. Recent studies have shown that airborne fungi are highly diverse (1), and that atmospheric transport leads to efficient exchange of species among different ecosystems (5, 6). The results presented in Fröhlich-Nowoisky et al. 2012 (7) clearly demonstrate the presence of geographic boundaries in the global distribution of microbial taxa in air, and indicate that regional differences may be important for the effects of microorganisms on climate and public health. DNA analyses of aerosol samples collected during rain events showed higher diversity and frequency of occurrence for fungi belonging to the Sordariomycetes, than samples that were collected under dry conditions (8). Sordariomycetes is the class that comprises known ice nucleation active species (Fusarium spp.). By determination of freezing ability of fungal colonies isolated from air samples two species of ice nucleation active fungi that were not previously known as biological ice nucleators were found. By DNA-analysis they were identified as Isaria farinosa and Acremonium implicatum. Both fungi belong to the phylum Ascomycota, produce fluorescent spores in the range of 1-4 µm in diameter, and induced freezing at -4 and

  11. Bacterial Ice Crystal Controlling Proteins

    PubMed Central

    Lorv, Janet S. H.; Rose, David R.; Glick, Bernard R.

    2014-01-01

    Across the world, many ice active bacteria utilize ice crystal controlling proteins for aid in freezing tolerance at subzero temperatures. Ice crystal controlling proteins include both antifreeze and ice nucleation proteins. Antifreeze proteins minimize freezing damage by inhibiting growth of large ice crystals, while ice nucleation proteins induce formation of embryonic ice crystals. Although both protein classes have differing functions, these proteins use the same ice binding mechanisms. Rather than direct binding, it is probable that these protein classes create an ice surface prior to ice crystal surface adsorption. Function is differentiated by molecular size of the protein. This paper reviews the similar and different aspects of bacterial antifreeze and ice nucleation proteins, the role of these proteins in freezing tolerance, prevalence of these proteins in psychrophiles, and current mechanisms of protein-ice interactions. PMID:24579057

  12. Bacterial ice crystal controlling proteins.

    PubMed

    Lorv, Janet S H; Rose, David R; Glick, Bernard R

    2014-01-01

    Across the world, many ice active bacteria utilize ice crystal controlling proteins for aid in freezing tolerance at subzero temperatures. Ice crystal controlling proteins include both antifreeze and ice nucleation proteins. Antifreeze proteins minimize freezing damage by inhibiting growth of large ice crystals, while ice nucleation proteins induce formation of embryonic ice crystals. Although both protein classes have differing functions, these proteins use the same ice binding mechanisms. Rather than direct binding, it is probable that these protein classes create an ice surface prior to ice crystal surface adsorption. Function is differentiated by molecular size of the protein. This paper reviews the similar and different aspects of bacterial antifreeze and ice nucleation proteins, the role of these proteins in freezing tolerance, prevalence of these proteins in psychrophiles, and current mechanisms of protein-ice interactions.

  13. Sources of organic ice nucleating particles in soils

    NASA Astrophysics Data System (ADS)

    Hill, Tom C. J.; DeMott, Paul J.; Tobo, Yutaka; Fröhlich-Nowoisky, Janine; Moffett, Bruce F.; Franc, Gary D.; Kreidenweis, Sonia M.

    2016-06-01

    Soil organic matter (SOM) may be a significant source of atmospheric ice nucleating particles (INPs), especially of those active > -15 °C. However, due to both a lack of investigations and the complexity of the SOM itself, the identities of these INPs remain unknown. To more comprehensively characterize organic INPs we tested locally representative soils in Wyoming and Colorado for total organic INPs, INPs in the heat-labile fraction, ice nucleating (IN) bacteria, IN fungi, IN fulvic and humic acids, IN plant tissue, and ice nucleation by monolayers of aliphatic alcohols. All soils contained ≈ 106 to ≈ 5 × 107 INPs g-1 dry soil active at -10 °C. Removal of SOM with H2O2 removed ≥ 99 % of INPs active > -18 °C (the limit of testing), while heating of soil suspensions to 105 °C showed that labile INPs increasingly predominated > -12 °C and comprised ≥ 90 % of INPs active > -9 °C. Papain protease, which inactivates IN proteins produced by the fungus Mortierella alpina, common in the region's soils, lowered INPs active at ≥ -11 °C by ≥ 75 % in two arable soils and in sagebrush shrubland soil. By contrast, lysozyme, which digests bacterial cell walls, only reduced INPs active at ≥ -7.5 or ≥ -6 °C, depending on the soil. The known IN bacteria were not detected in any soil, using PCR for the ina gene that codes for the active protein. We directly isolated and photographed two INPs from soil, using repeated cycles of freeze testing and subdivision of droplets of dilute soil suspensions; they were complex and apparently organic entities. Ice nucleation activity was not affected by digestion of Proteinase K-susceptible proteins or the removal of entities composed of fulvic and humic acids, sterols, or aliphatic alcohol monolayers. Organic INPs active colder than -10 to -12 °C were resistant to all investigations other than heat, oxidation with H2O2, and, for some, digestion with papain. They may originate from decomposing plant material, microbial

  14. A next generation sequencing of Arctic bacteria in snow and frost flowers: identification, abundance and freezing nucleation

    NASA Astrophysics Data System (ADS)

    Mortazavi, R.; Attiya, S.; Ariya, P. A.

    2014-12-01

    During the spring of 2009, as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the conventional culture-based PCR identification approach, we deployed a state-of-the-art genomic Next Generation Sequencing (NGS) technique to examine diverse bacterial communities in Arctic samples. 11-18 known phyla or candidate divisions were identified with the great majority of sequences (12.3-83.1%) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Cyanobacteria. At the genus level, 101-245 different genera were detected. The highest number of cultivable bacteria in cultured samples was observed in frost flowers (FF) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU mL-1, respectively; and for cultivable fungi 5 ± 1 CFU mL-1 in windpack (WP) and blowing snow (BS). Complementary morphology and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolate ranged from -20.3 ± 1.5 to -15.7 ± 5.6 °C, and for melted samples from 9.5 ± 1.0 to 18.4 ± 0.1 °C. An isolate belonging to the Bacillus species (96% similarity) had ice nucleation activity of -6.8 ± 0.2 °C. Comparison with Montreal urban snow, revealed a seemingly diverse community of bacteria exists in the Arctic with many originating from distinct ecological environments, and we discuss the potential impact of microbial snow in the freezing and melting process of the snowpack in the Arctic.

  15. SUCCESS Evidence for Cirrus Cloud Ice Nucleation Mechanisms

    NASA Technical Reports Server (NTRS)

    Jensen, Eric; Gore, Warren J. Y. (Technical Monitor)

    1997-01-01

    During the SUCCESS mission, several measurements were made which should improve our understanding of ice nucleation processes in cirrus clouds. Temperature and water vapor concentration were made with a variety of instruments on the NASA DC-8. These observations should provide accurate upper tropospheric humidities. In particular, we will evaluate what humidities are required for ice nucleation. Preliminary results suggest that substantial supersaturations frequently exist in the upper troposphere. The leading-edge region of wave-clouds (where ice nucleation occurs) was sampled extensively at temperatures near -40 and -60C. These observations should give precise information about conditions required for ice nucleation. In addition, we will relate the observed aerosol composition and size distributions to the ice formation observed to evaluate the role of soot or mineral particles on ice nucleation. As an alternative technique for determining what particles act as ice nuclei, numerous samples of aerosols inside ice crystals were taken. In some cases, large numbers of aerosols were detected in each crystal, indicating that efficient scavenging occurred. Analysis of aerosols in ice crystals when only one particle per crystal was detected should help with the ice nucleation issue. Direct measurements of the ice nucleating activity of ambient aerosols drawn into airborne cloud chambers were also made. Finally, measurements of aerosols and ice crystals in contrails should indicate whether aircraft exhaust soot particles are effective ice nuclei.

  16. Biological residues define the ice nucleation properties of soil dust

    NASA Astrophysics Data System (ADS)

    Conen, F.; Morris, C. E.; Leifeld, J.; Yakutin, M. V.; Alewell, C.

    2011-06-01

    Soil dust is a major driver of ice nucleation in clouds leading to precipitation. It consists largely of mineral particles with a small fraction of organic matter constituted mainly of remains of micro-organisms that participated in degrading plant debris before their own decay. Some micro-organisms have been shown to be much better ice nuclei than the most efficient soil mineral. Yet, current aerosol schemes in global climate models do not consider a difference between soil dust and mineral dust in terms of ice nucleation activity. Here, we show that particles from the clay and silt size fraction of four different soils naturally associated with 0.7 to 11.8 % organic carbon (w/w) can have up to four orders of magnitude more ice nuclei per unit mass active in the immersion freezing mode at -12 °C than montmorillonite, the most efficient pure clay mineral. Most of this activity was lost after heat treatment. Removal of biological residues reduced ice nucleation activity to, or below that of montmorillonite. Desert soils, inherently low in organic content, are a large natural source of dust in the atmosphere. In contrast, agricultural land use is concentrated on fertile soils with much larger organic matter contents than found in deserts. It is currently estimated that the contribution of agricultural soils to the global dust burden is less than 20 %. Yet, these disturbed soils can contribute ice nuclei to the atmosphere of a very different and much more potent kind than mineral dusts.

  17. Of Ice and Microbes

    NASA Astrophysics Data System (ADS)

    Deming, Jody

    2006-12-01

    Inuit hunters of the North have long recognized ice as the natural state of water from which life flows on Earth. Although unaware of the microscopic world, they chart changes in properties of ice and water that derive from a succession of microbial inhabitants. Scientific hunters of the West have largely overlooked all but the warmest of ices as dynamic scenes of microbial life, considering the frozen realm to archive life forms instead. Deeply frozen glacial ice on Earth does appear to preserve microbes effectively, but isn't the ocean beneath the geologically dynamic ice of Europa believed too salty? Aren't the subsurface ices of Mars expected to be rich in all manner of mineralogical impurities? Wherever salt and other mineral impurities are sufficiently abundant in Earth ice, the ice contains interior liquid water that can range from nano-layer films on grain surfaces (glacial ice) to a porous network of brine (Arctic winter sea ice down to 20°C). Other recent studies of saline ices have indicated a world of interacting life forms, with viruses infecting bacteria in brines at -12°C (the lowest temperature tested), the domains of Bacteria and Archaea undergoing succession in winter ices (down to -28°C), and evidence that cellular maintenance may go forward incrementally even below the eutectic of seawater (-55°C). Microbes are also known to alter the physical properties of their icy homes by producing exopolymers that further depress the freezing point, either directly or by entraining more salt into the ice. Even the most inhospitable of ices to human hunters may contain interior oases for microbes, in control to some degree of their own space. In considering the habitability of icy worlds beyond Earth, we'd do well to learn more about the evolutionary prowess of microbes in adapting to conditions beyond our warm-blooded imaginations.

  18. Properties of a novel extracellular cell-free ice nuclei from ice-nucleating Pseudomonas antarctica IN-74.

    PubMed

    Muryoi, Naomi; Kawahara, Hidehisa; Obata, Hitoshi

    2003-09-01

    Some ice-nucleating bacterial strains, including Pantoea ananatis (Erwinia uredovora), Pseudomonas fluorescens, and Pseudomonas syringae isolates, were examined for the ability to shed ice nuclei into the growth medium. A novel ice-nucleating bacterium, Pseudomonas antarctica IN-74, was isolated from Ross Island, Antarctica. Cell-free ice nuclei from P. antarctica IN-74 were different from the conventional cell-free ice nuclei and showed a unique characterization. Cell-free ice nuclei were purified by centrifugation, filtration (0.45 microm), ultrafiltration, and gel filtration. In an ice-nucleating medium in 1 liter of cell culture, maximum growth was obtained with the production of 1.9 mg of cell-free ice nuclei. Ice nucleation activity in these cell-free ice nuclei preparations was extremely sensitive to pH. It was demonstrated that the components of cell-free ice nuclei were protein (33%), saccharide (12%), and lipid (55%), indicating that cell-free ice nuclei were lipoglycoproteins. Also, carbohydrate and lipid stains showed that cell-free ice nuclei contained both carbohydrate and lipid moieties.

  19. Arctic microbial and next-generation sequencing approach for bacteria in snow and frost flowers: selected identification, abundance and freezing nucleation

    NASA Astrophysics Data System (ADS)

    Mortazavi, R.; Attiya, S.; Ariya, P. A.

    2015-06-01

    During the spring of 2009, as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population diversity, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the culturing and gene-sequence-based identification approach, we utilized a state-of-the-art genomic next-generation sequencing (NGS) technique to examine the diversity of bacterial communities in Arctic samples. Known phyla or candidate divisions were detected (11-18) with the majority of sequences (12.3-83.1%) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Cyanobacteria. The number of genera detected ranged from, 101-245. The highest number of cultivable bacteria was observed in frost flowers (FFs) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU m L-1, respectively; and for cultivable fungi 5 ± 1 CFU m L-1 in windpack (WP) and blowing snow (BS). Morphology/elemental composition and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy with energy-dispersive X-ray spectroscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolates ranged from -20.3 ± 1.5 to -15.7 ± 5.6 °C, and for melted snow samples from -9.5 ± 1.0 to -18.4 ± 0.1 °C. An isolate belonging to the genus Bacillus (96% similarity) had ice nucleation activity of -6.8 ± 0.2 °C. Comparison with Montreal urban snow, revealed that a seemingly diverse community of bacteria exists in the Arctic with some taxa possibly originating from distinct ecological environments. We discuss the potential impact of snow microorganisms in the freezing and melting process of the snowpack in the Arctic.

  20. Microzoo: assessing diversity of biological ice nuclei in rain and snow

    NASA Astrophysics Data System (ADS)

    Stopelli, Emiliano; Conen, Franz; Baudinot, Corinne; De Bortoli, Samira; Guilbaud, Caroline; Alewell, Christine; Morris, Cindy

    2015-04-01

    Biological ice nuclei (IN) are involved in initiating precipitation at temperatures between 0 and -12°C. More and more species of pollen, fungi and bacteria are being discovered to actively induce ice formation. Nevertheless, several questions remain unanswered: which organisms contribute the most to the IN activity in the atmosphere? What fraction of biological IN activity in precipitation samples is due to living cells, dead organic material or even macromolecules detached from cells? As first approach to tackle these questions, we decided to separate biological IN by size and thermal stability, assessing the cumulative number of IN active at temperatures warmer than -12°C in precipitation samples processed via progressive filtration through different meshes (5 µm, 1.2 µm, 0.22 µm) followed by heating (40°C, 80°C or 100°C). This method was applied on a set of precipitation samples collected at two sites in Switzerland: Basel (260 m a.s.l.) and the High Altitude Research Station of Jungfraujoch (3580 m a.s.l.). Results showed that each sample is characterised by a unique freezing profile and almost all ice nucleation activity in the temperature under study was due to proteinaceous structures (lost after heating at 80°C or 100°C). Interestingly, a significant part of the observed biological activity was always associated with the fraction > 5 µm and lost already after warming to 40°C. This suggests that biological IN activity depends also on easily denaturable molecular structures which can be in form of clusters rather than single floating airborne bacterial cells or molecules, or which are due to organisms that produce particles bigger than 5 µm (fungal spores, for example). Moreover, the storage of a sample can strongly change its freezing spectrum, emphasising the need to do measurements on freshly fallen precipitation.

  1. Ice nucleation by cellulose and its potential contribution to ice formation in clouds

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Möhler, O.; Yamashita, K.; Tajiri, T.; Saito, A.; Kiselev, A.; Hoffmann, N.; Hoose, C.; Jantsch, E.; Koop, T.; Murakami, M.

    2015-04-01

    Ice particles in the atmosphere influence clouds, precipitation and climate, and often form with help from aerosols that serve as ice-nucleating particles. Biological particles, including non-proteinaceous ones, contribute to the diverse spectrum of ice-nucleating particles. However, little is known about their atmospheric abundance and ice nucleation efficiency, and their role in clouds and the climate system is poorly constrained. One biological particle type, cellulose, has been shown to exist in an airborne form that is prevalent throughout the year even at remote and elevated locations. Here we report experiments in a cloud simulation chamber to demonstrate that microcrystalline cellulose particles can act as efficient ice-nucleating particles in simulated supercooled clouds. In six immersion mode freezing experiments, we measured the ice nucleation active surface-site densities of aerosolized cellulose across a range of temperatures. Using these active surface-site densities, we developed parameters describing the ice nucleation ability of these particles and applied them to observed atmospheric cellulose and plant debris concentrations in a global aerosol model. We find that ice nucleation by cellulose becomes significant (>0.1 l-1) below about -21 °C, temperatures relevant to mixed-phase clouds. We conclude that the ability of cellulose to act as ice-nucleating particles requires a revised quantification of their role in cloud formation and precipitation.

  2. Deposition and immersion-mode nucleation of ice by three distinct samples of volcanic ash

    NASA Astrophysics Data System (ADS)

    Schill, G. P.; Genareau, K.; Tolbert, M. A.

    2015-07-01

    Ice nucleation of volcanic ash controls both ash aggregation and cloud glaciation, which affect atmospheric transport and global climate. Previously, it has been suggested that there is one characteristic ice nucleation efficiency for all volcanic ash, regardless of its composition, when accounting for surface area; however, this claim is derived from data from only two volcanic eruptions. In this work, we have studied the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman microscopy coupled to an environmental cell. Ash from the Fuego (basaltic ash, Guatemala), Soufrière Hills (andesitic ash, Montserrat), and Taupo (Oruanui eruption, rhyolitic ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. In the present study, we find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice from 225 to 235 K at ice saturation ratios of 1.05 ± 0.01, comparable to the mineral dust proxy kaolinite. Since depositional ice nucleation will be more important at colder temperatures, fine volcanic ash may represent a global source of cold-cloud ice nuclei. For immersion freezing relevant to mixed-phase clouds, however, only the Oruanui ash exhibited appreciable heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.

  3. Rates of assembly and degradation of bacterial ice nuclei.

    PubMed

    Watanabe, N M; Southworth, M W; Warren, G J; Wolber, P K

    1990-11-01

    The kinetics of ice-nucleus assembly from newly synthesized nucleation protein were observed following induction of nucleation gene expression in the heterologous host Escherichia coli. Assembly was significantly slower for the small proportion of ice nuclei active above -4.4 degrees C; this was consistent with the belief that these nuclei comprise the largest aggregates of nucleation protein. The kinetics of nucleus degradation were followed after inhibiting protein synthesis. Nucleation activity and protein showed a concerted decay, indicating that most of the functional ice nuclei are in equilibrium with a single cellular pool of nucleation protein. A minority of the ice nuclei decayed much more slowly than the majority; presumably their nucleation protein was distinct either by virtue of different structure or different subcellular compartmentalization, or because of its presence in a metabolically distinct subpopulation of cells.

  4. Biological ice nucleation initiates hailstone formation

    NASA Astrophysics Data System (ADS)

    Michaud, Alexander B.; Dore, John E.; Leslie, Deborah; Lyons, W. Berry; Sands, David C.; Priscu, John C.

    2014-11-01

    Cloud condensation and ice nuclei in the troposphere are required precursors to cloud and precipitation formation, both of which influence the radiative balance of Earth. The initial stage of hailstone formation (i.e., the embryo) and the subsequent layered growth allow hail to be used as a model for the study of nucleation processes in precipitation. By virtue of the preserved particle and isotopic record captured by hailstones, they represent a unique form of precipitation that allows direct characterization of the particles present during atmospheric ice nucleation. Despite the ecological and economic consequences of hail storms, the dynamics of hailstone nucleation, and thus their formation, are not well understood. Our experiments show that hailstone embryos from three Rocky Mountain storms contained biological ice nuclei capable of freezing water at warm, subzero (°C) temperatures, indicating that biological particles can act as nucleation sites for hailstone formation. These results are corroborated by analysis of δD and δ18O from melted hailstone embryos, which show that the hailstones formed at similarly warm temperatures in situ. Low densities of ice nucleation active abiotic particles were also present in hailstone embryos, but their low concentration indicates they were not likely to have catalyzed ice formation at the warm temperatures determined from water stable isotope analysis. Our study provides new data on ice nucleation occurring at the bottom of clouds, an atmospheric region whose processes are critical to global climate models but which has challenged instrument-based measurements.

  5. Ice nucleation of bioaerosols - a resumee

    NASA Astrophysics Data System (ADS)

    Pummer, Bernhard G.; Atanasova, Lea; Bauer, Heidi; Bernardi, Johannes; Chazallon, Bertrand; Druzhinina, Irina S.; Grothe, Hinrich

    2013-04-01

    The role of biological particles for ice nucleation (IN) is still debated. Here, we present a summary of investigation and comparison of different ice nuclei. Apart from the bacterial ice nucleation proteins in Snomax, we further investigated a broad spectrum of pollen and fungal spores in the search for ice nucleation activity. Apart from Snomax, only few samples showed vital IN activity, like Fusarium avenaceum spores and Betula pendula pollen. Chemical characterization accentuated the differences between bacterial and pollen ice nuclei. Exposure to natural stresses, like UV and NOx, led to a significant decrease in IN activity. Furthermore, the releasable fraction of the pollen material, which includes the ice nuclei, was extracted with water and dried up. These residues were investigated with Raman spectroscopy and compared with the spectra of whole pollen grains. Measurements clearly demonstrated that the aqueous fraction contained mainly saccharides, lipids and proteins, but no sporopollenin, which is the bulk material of the outer pollen wall. Fungal spores of ecologically, economically or otherwise relevant species were also investigated. Most species showed no significant IN activity at all. A few species showed a slight increase in freezing temperature, but still significantly below the activity of the most active pollen or mineral dusts. Only Fusarium avenaceum showed strong IN activity. Cultivation of Fusarium and Trichoderma (close relatives of Fusarium) at different temperatures showed changes in total protein expression, but no impact on the IN activity.

  6. Ice nucleation efficiency of soot from biomass combustion

    NASA Astrophysics Data System (ADS)

    Umo, N. S.; Murray, B. J.; O'Sullivan, D.; Baeza-Romero, M. T.; Plane, J. C.

    2013-05-01

    Do Soot aerosols in the atmosphere indirectly influence the radiative budget of the Earth by modifying cloud properties, either by acting as cloud condensation nuclei (CCN) or as ice nuclei (IN). The ice nucleation activity of soot remains poorly quantified and there is a need to parameterise its impact for use in cloud-aerosol models. Here, we investigate the ice nucleation activity of eugenol soot in the immersion mode at conditions relevant to mixed-phase clouds. Eugenol is used as a proxy for a biomass combustion source. The efficiency of soot as an IN was quantified using droplet freezing techniques with droplet volumes ranging from nanolitre (˜100 μm diameter) to microliter (˜1 mm diameter). We show that soot nucleates ice in our experiments at temperatures up to -14°C, although the efficiency with which it does so is less than for mineral dust on a per surface area basis. An estimation of the IN number concentration that could result from our eugenol soot showed that, on a global average basis, IN from soot is secondary in importance to mineral dust below about -20°C. However, it may be important as IN in some locations which are deficient in dust, but rich in soot particles. We conclude that its overall impact can be significant considering its relative regional and global abundance.

  7. Biological control of an insect pest by gut-colonizing Enterobacter cloacae transformed with ice nucleation gene.

    PubMed

    Watanabe, K; Abe, K; Sato, M

    2000-01-01

    The ice nucleation (IN) gene inaA of epiphytic Erwinia (Pantoea) ananas IN10 was transformed into Enterobacter cloacae WBMH-3-CMr originated from the faeces of silkworms. The transformant designated as Ent. cloacae WBMH-3-CMr(pICE6S13) exhibited IN activity, unlike the parent strain. The transgenic strain was ingested by mulberry pyralid larvae, fed on detached mulberry leaves, and the supercooling capacity and cold hardiness of these larvae were examined. The mean supercooling point (SCP) of the larvae ingesting the transgenic strain was - 3.3 degrees C, 8 degrees C higher than that of larvae treated with distilled water (control) and 1.5 C higher than an ice nucleation active (INA) strain of Erw. ananas. The SCPs of the larvae were stably maintained over the 9 d after ingestion. The maintenance of these high SCPs was due to transgenic Ent. cloacae having a more stable and efficient gut colonization than Erw. ananas, which is identified by the distribution of a narrower range of SCPs (-2 to -5 degrees C) in larvae treated with the transgenic stain. Furthermore, most of the larvae ingesting the transgenic strain froze and died when they were exposed to cold conditions of -5 degrees C for 18 h, 3 or 7 d after ingestion. In contrast, most of the larvae ingesting no bacterium did not die under similar conditions. On the other hand, the growth ability of Ent. cloacae WBMH-3-CMr on mulberry leaves tended to be lower than that of epiphytic Erw. ananas, as assayed by pot tests. These findings would expand the possibility of biological control using INA bacteria since Ent. cloacae would harbour a broader host (insect) range for gut colonization and a smaller affinity to plants to benefit from prevention of plant frost injury.

  8. Deposition and immersion mode nucleation of ice by three distinct samples of volcanic ash using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Schill, G. P.; Genareau, K.; Tolbert, M. A.

    2015-01-01

    Ice nucleation on volcanic ash controls both ash aggregation and cloud glaciation, which affect atmospheric transport and global climate. Previously, it has been suggested that there is one characteristic ice nucleation efficiency for all volcanic ash, regardless of its composition, when accounting for surface area; however, this claim is derived from data from only two volcanic eruptions. In this work, we have studied the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman Microscopy coupled to an environmental cell. Ash from the Fuego (basaltic ash, Guatemala), Soufrière Hills (andesitic ash, Montserrat), and Taupo (Oruanui euption, rhyolitic ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. In the present study, we find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice from 225-235 K at ice saturation ratios of 1.05 ± 0.01, comparable to the mineral dust proxy kaolinite. Since depositional ice nucleation will be more important at colder temperatures, fine volcanic ash may represent a global source of cold-cloud ice nuclei. For immersion freezing relevant to mixed-phase clouds, however, only the Oruanui ash exhibited heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.

  9. Ice, Ice, Baby!

    NASA Astrophysics Data System (ADS)

    Hamilton, C.

    2008-12-01

    The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an outreach program based on hands-on activities called "Ice, Ice, Baby". These lessons are designed to teach the science principles of displacement, forces of motion, density, and states of matter. These properties are easily taught through the interesting topics of glaciers, icebergs, and sea level rise in K-8 classrooms. The activities are fun, engaging, and simple enough to be used at science fairs and family science nights. Students who have participated in "Ice, Ice, Baby" have successfully taught these to adults and students at informal events. The lessons are based on education standards which are available on our website www.cresis.ku.edu. This presentation will provide information on the activities, survey results from teachers who have used the material, and other suggested material that can be used before and after the activities.

  10. Life in Ice: Implications to Astrobiology

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2009-01-01

    During the 2008 Tawani International Expedition Schirmacher Oasis/Lake Untersee Antarctica Expedition, living and instantly motile bacteria were found in freshly thawed meltwater from ice of the Schirmacher Oasis Lakes, the Anuchin Glacier ice and samples of the that perennial ice sheet above Lake Untersee. This phenomenon of living bacteria encased in ice had previously been observed in the 32,000 year old ice of the Fox Tunnel. The bacteria found in this ice included the strain FTR1T which was isolated and published as valid new species (Carnobacterium pleistocenium) the first validly published living Pleistocene organism still alive today. Living bacteria were also extracted from ancient ice cores from Vostok, Antarctica. The discovery that many strains of bacteria are able to survive and remain alive while frozen in ice sheets for long periods of time may have direct relevance to Astrobiology. The abundance of viable bacteria in the ice sheets of Antarctica suggests that the presence of live bacteria in ice is common, rather than an isolated phenomenon. This paper will discuss the results of recent studies at NSSTC of bacteria cryopreserved in ice. This paper advances the hypothesis that cryopreserved cells, and perhaps even viable bacterial cells, may exist today--frozen in the water-ice of lunar craters, the Polar Caps or craters of Mars; or in the permafrost of Mars; ice and rocks of comets or water bearing asteroids; or in the frozen crusts of the icy moons of Jupiter and Saturn. The existence of bacterial life in ice suggests that it may not be necessary to drill through a thick ice crust to reach liquid water seas deep beneath the icy crusts of Europa, Ganymede and Enceladus. The presence of viable bacteria in the ice of the Earth s Polar Caps suggests that the possibility that cryo-panspermia (i.e., the trans-planetary transfer of microbial life by impact ejection/spallation of bacteria-rich polar ice masses) deserves serious consideration and study as a

  11. Life in Ice: Implications to Astrobiology

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2009-01-01

    During the 2008 Tawani International Expedition Schirmacher Oasis/Lake Untersee Antarctica Expedition, living and instantly motile bacteria were found in freshly thawed meltwater from ice of the Schirmacher Oasis Lakes, the Anuchin Glacier ice and samples of the that perennial ice sheet above Lake Untersee. This phenomenon of living bacteria encased in ice had previously been observed in the 32,000 year old ice of the Fox Tunnel. The bacteria found in this ice included the strain FTR1T which was isolated and published as valid new species (Carnobacterium pleistocenium) the first validly published living Pleistocene organism still alive today. Living bacteria were also extracted from ancient ice cores from Vostok, Antarctica. The discovery that many strains of bacteria are able to survive and remain alive while frozen in ice sheets for long periods of time may have direct relevance to Astrobiology. The abundance of viable bacteria in the ice sheets of Antarctica suggests that the presence of live bacteria in ice is common, rather than an isolated phenomenon. This paper will discuss the results of recent studies at NSSTC of bacteria cryopreserved in ice. This paper advances the hypothesis that cryopreserved cells, and perhaps even viable bacterial cells, may exist today--frozen in the water-ice of lunar craters, the Polar Caps or craters of Mars; or in the permafrost of Mars; ice and rocks of comets or water bearing asteroids; or in the frozen crusts of the icy moons of Jupiter and Saturn. The existence of bacterial life in ice suggests that it may not be necessary to drill through a thick ice crust to reach liquid water seas deep beneath the icy crusts of Europa, Ganymede and Enceladus. The presence of viable bacteria in the ice of the Earth s Polar Caps suggests that the possibility that cryo-panspermia (i.e., the trans-planetary transfer of microbial life by impact ejection/spallation of bacteria-rich polar ice masses) deserves serious consideration and study as a

  12. Characterization and recombinant expression of a divergent ice nucleation protein from 'Pseudomonas borealis'.

    PubMed

    Wu, Zhongqin; Qin, Lei; Walker, Virginia K

    2009-04-01

    Isolates of 'Pseudomonas borealis' were recovered after ice-affinity selection of summer-collected soils. 'P. borealis' DL7 was further characterized and shown to have ice nucleation activity (INA), a property that allows the crystallization of ice at temperatures close to the melting point, effectively preventing the supercooling of water. INA was optimally detected after culturing at temperatures consistent with psychrophilic growth. The sequence encoding the 'P. borealis' ice nucleation protein (INP) was obtained using both PCR and chromosome walking. When expressed in Escherichia coli, the resulting inaPb recombinants had INA. The 'P. borealis' sequence, dubbed inaPb, is clearly related to previously cloned INP genes, but it shows greater divergence. Sequence analysis suggests that there are two opposite flat surfaces, one relatively hydrophobic that likely serves as an ice template, and the other that could function as a complementary face to facilitate interprotein interaction for ice-step formation.

  13. Investigation of Microcrystalline Cellulose as Ice Nucleus in Immersion Freezing Processes

    NASA Astrophysics Data System (ADS)

    Häusler, Thomas; Khaybulkina, Evgeniya; Felgitsch, Laura; Bichler, Magdalena; Grothe, Hinrich

    2015-04-01

    Aerosol-cloud interactions play an important role in earth's radiation balance. Aerosol particles act as cloud condensation nuclei for liquid droplets and/or as ice nuclei for the formation of ice particles. Previous research in our group has been related to biological ice nucleation.1-3 Here, we present a proxy for many biological macromolecular substances, i.e. microcrystalline cellulose. Due to the chemical convenience of cellulose compared to other biological ice nuclei, basic, but still unknown ice nucleation mechanisms can be investigated. Cellulose is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. It is an important structural element of the primary cell wall of green plants, many forms of algae and the oomycetes. Several types of microcrystalline cellulose were analysed and investigated due to their physico-chemical properties. Immersion freezing experiments were carried out in a unique reaction gadget. In this device a water-in-oil suspension (with the cellulose suspended in the aqueous phase) was cooled till the freezing point and was observed through a microscope. The results of the immersion freezing experiments of the different cellulose types showed variable ice nucleation activities depending on their morphology (e.g. particle size) and their concentration. Further analysis methods as scanning electron microscopy (SEM) and small angle X-ray scattering (SAX) were carried out to entirely describe the cellulose and their ice nucleation activity. [1] S.Augustin, H. Wex, D. Niedermeier, B. Pummer, H.Grothe, S. Hartmann, L. Tomsche, T. Clauss, J. Voigtländer, K. Ingatius, and F. Stratmann. Immersion freezing of birch pollen washing water. Atmospheric Chemistry Physics 2013, 13, 10989-11003 [2] B. Pummer, L. Atanasova, H. Bauer, H. Bernardi, I. S. Druzhinina, J. Froehlich-Nowoisky, H. Grothe. Spores of many common airborne fungi reveal no ice nucleation activity in oil immersion

  14. Olivine-respiring bacteria isolated from the rock-ice interface in a lava-tube cave, a Mars analog environment.

    PubMed

    Popa, Radu; Smith, Amy R; Popa, Rodica; Boone, Jane; Fisk, Martin

    2012-01-01

    The boundary between ice and basalt on Earth is an analogue for some near-surface environments of Mars. We investigated neutrophilic iron-oxidizing microorganisms from the basalt-ice interface in a lava tube from the Oregon Cascades with perennial ice. One of the isolates (Pseudomonas sp. HerB) can use ferrous iron Fe(II) from the igneous mineral olivine as an electron donor and O(2) as an electron acceptor. The optimum growth temperature is ∼12-14°C, but growth also occurs at 5°C. Bicarbonate is a facultative source of carbon. Growth of Pseudomonas sp. HerB as a chemolithotrophic iron oxidizer with olivine as the source of energy is favored in low O(2) conditions (e.g., 1.6% O(2)). Most likely, microbial oxidation of olivine near pH 7 requires low O(2) to offset the abiotic oxidation of iron. The metabolic capabilities of this bacterium would allow it to live in near-surface, icy, volcanic environments of Mars in the present or recent geological past and make this type of physiology a prime candidate in the search for life on Mars.

  15. Olivine-Respiring Bacteria Isolated from the Rock-Ice Interface in a Lava-Tube Cave, a Mars Analog Environment

    PubMed Central

    Smith, Amy R.; Popa, Rodica; Boone, Jane; Fisk, Martin

    2012-01-01

    Abstract The boundary between ice and basalt on Earth is an analogue for some near-surface environments of Mars. We investigated neutrophilic iron-oxidizing microorganisms from the basalt-ice interface in a lava tube from the Oregon Cascades with perennial ice. One of the isolates (Pseudomonas sp. HerB) can use ferrous iron Fe(II) from the igneous mineral olivine as an electron donor and O2 as an electron acceptor. The optimum growth temperature is ∼12–14°C, but growth also occurs at 5°C. Bicarbonate is a facultative source of carbon. Growth of Pseudomonas sp. HerB as a chemolithotrophic iron oxidizer with olivine as the source of energy is favored in low O2 conditions (e.g., 1.6% O2). Most likely, microbial oxidation of olivine near pH 7 requires low O2 to offset the abiotic oxidation of iron. The metabolic capabilities of this bacterium would allow it to live in near-surface, icy, volcanic environments of Mars in the present or recent geological past and make this type of physiology a prime candidate in the search for life on Mars. Key Words: Extremophiles—Mars—Olivine—Iron-oxidizing bacteria—Redox. Astrobiology 12, 9–18. PMID:22165996

  16. Life in ice: implications to astrobiology

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.; Pikuta, Elena V.

    2009-08-01

    During previous research expeditions to Siberia, Alaska and Antarctica, it was observed that glaciers and ice wedges contained bacterial cells that became motile as soon as the ice melted. This phenomenon of live bacteria in ice was first documented for microbes in ancient ice cores from Vostok, Antarctica. The first validly published species of Pleistocene bacteria alive on Earth today was Carnobacterium pleistocenium. This extremophile had remained for 32,000 years, encased in ice recently exposed in the Fox Tunnel of Alaska. These frozen bacteria began to swim as soon as the ice was thawed. Dark field microscopy studies revealed that large numbers of bacteria exhibited motility as soon as glacial ice was melted during our recent Expeditions to Alaska and Antarctica led to the conclusion that microbial life in ice was not a rare phenomenon. The ability of bacteria to remain alive while frozen in ice for long periods of time is of great significance to Astrobiology. In this paper, we describe the recent observations and advance the hypothesis that life in ice provides valuable clues to how we can more easily search for evidence of life on the Polar Caps of Mars, comets and other icy bodies of our Solar System. It is suggested that cryopanspermia may have played a far more important role in Origin of Life on Earth and the distribution of Life throughout the Cosmos and than previously thought possible.

  17. Externally mixed aerosol : simulation of ice nucleation in a parcel model

    NASA Astrophysics Data System (ADS)

    Anquetil-Deck, Candy; Hoose, Corinna; Conolly, Paul

    2014-05-01

    The effect of different aerosol (mineral dust, bacteria and soot) acting as immersion ice nuclei is investigated using ACPIM (AerosolCloud Precipitation Interaction Model) [1]. ACPIM is a powerful tool which can be used in two different ways. This box model can be, either, driven by experimental data (experiments carried out at the AIDA cloud chamber facility) or used as an air parcel in order to examine different ice nucleation parameterizations under specific conditions. This adiabatic air parcel model was employed for the simulation of a convective cloud. The study consists here in the investigation of how two externally mixed aerosols interact with one another. The initial study concentrates on mineral dust aerosol and biological aerosol without any background in order to fully understand the interaction between the different types of aerosol. Immersion freezing is described for the mineral dust aerosol by Niemand et al. 's parameterization [2], which was derived from laboratory studies in AIDA and is an extension of surface site density approach suggested by Connolly et al. [1]. Regarding bioaerosol, we introduce Hummel et al. 's parameterization [3] : f(in) = f(max)(1 - exp(- Ap *n(s)(T))) With an empirically fitted ice nucleation active site density n s based on AIDA measurements of Pseudomonas syringae bacteria [4]. This initial study is conducted for different proportion of each aerosol (the total number of aerosol being constant throughout all the simulation runs) at different vertical velocities. We then extented this study with different backgrounds (urban, marine, rural) in order to get a full picture. We found that there is not only a CCN competition but an IN competition as well. References : [1] Connolly, P. J., Möhler O., Field P. R., Saathoff H., Burgess, R., Choularton, T. and Gallagher, M., Atmos. Chem. Phys 9, 2805-2824 (2009). [2] Niemand, M., Möhler, O., Vogel B., Vogel, H., Hoose, C., Connolly, P., Klein, H., Bingemer, H., De

  18. Ice encapsulation protects rather than disturbs the freezing lichen.

    PubMed

    Bjerke, J W

    2009-03-01

    Arctic and alpine terricolous lichens are adapted to harsh environments and are tolerant to extremely low temperatures when metabolically inactive. However, there are reports indicating that freezing can be lethal to metabolically active lichens. With a projected warmer and more unstable climate, winter precipitation at high latitudes will fall more frequently as rain, causing snowmelt and encapsulating terricolous lichens in ice or exposing them to large temperature fluctuations. Lichens are a major winter food source for reindeer in most parts of the circumpolar region. A laboratory experiment tested how three hydrated reindeer forage lichen species covered by snow, encapsulated in ice, or uncovered responded to storage at freezing temperatures and subsequent warming. Photosynthetic performance (maximal fluorescence of dark-adapted samples and net photosynthetic rates) was significantly lower in lichens not insulated by snow or ice, whereas there were few differences between the snow and ice treatments. It is suggested that snow and ice provide sufficiently moist environments to improve extracellular and reduce intracellular ice nucleation activity. Ice encapsulation, which is often lethal to vascular plants, did not have any negative effects on the studied lichens. The results indicate that complete snow and ice melt followed by refreezing can be detrimental to terricolous lichen ecosystems. Reduced lichen biomass will have a negative effect both on reindeer winter survival and the indigenous peoples who herd reindeer.

  19. Immersion freezing of clay minerals and bacterial ice nuclei

    NASA Astrophysics Data System (ADS)

    Hiranuma, Naruki; Möhler, Ottmar; Bingemer, Heinz; Bundke, Ulrich; Cziczo, Daniel J.; Danielczok, Anja; Ebert, Martin; Garimella, Sarvesh; Hoffmann, Nadine; Höhler, Kristina; Kanji, Zamin A.; Kiselev, Alexei; Raddatz, Michael; Stetzer, Olaf

    2013-05-01

    The immersion mode ice nucleation efficiency of clay minerals and biological aerosols has been investigated using the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber. Both monodisperse and polydisperse populations of (1) various clay dust samples as well as (2) Snomax® (a proxy for bacterial ice nucleators) and (3) hematite are examined in the temperature range between -4°C and -35°C. The temperature dependence of ice formation inferred by the INAS (Ice Nucleation Active Surface-Site) density is investigated and discussed as a function of cooling rate and by comparing to predicted nucleation rates (i.e., classical nucleation theory with θ-probability density function nucleation scheme). To date, we observe that maintaining constant AIDA temperature does not trigger any new ice formation during the immersion freezing experiments with clay dust samples and Snomax®, implying strong temperature dependency (and weak time dependency) within our time scales and conditions of experiments. Ice residuals collected through a newly developed PCVI (Pumped ounter-flow Virtual Impactor) with the 50% cut size diameter of 10 to 20 μm have also been examined by electron microscope analyses to seek the chemical and physical identity of ice nuclei in clay minerals. In addition to the AIDA results, complementary measurements with mobile ice nucleation counters are also presented.

  20. Possible Application of Bacterial Condensation Freezing to Artificial Rainfall Enhancement.

    NASA Astrophysics Data System (ADS)

    Levin, Z.; Yankofsky, S. A.; Pardes, D.; Magal, N.

    1987-09-01

    Both gram-positive and gram-negative bacteria become excellent condensation nuclei when lyophilized to dryness. The same freeze-dry procedure does not inactivate the highly effective freezing nuclei produced by ice nucleation active bacteria. Therefore, irrespective of their contact nucleation potential, ice nucleation-active bacteria ought to effect condensation freezing at 10°C of warmer in cloud systems. Output from a numerical cloud model suggests that the condensation freezing capability of ice nucleation-active bacteria at warmer temperatures could be exploited to produce rainfall from clouds too warm to respond positively to inorganic nucleants like silver iodide.

  1. Bacterial biomass and production in pack ice of Antarctic marginal ice edge zones

    NASA Astrophysics Data System (ADS)

    Kottmeier, Steven T.; Sullivan, Cornelius W.

    1990-08-01

    Bacterial biomass and production in pack ice is little known even though the pack accounts for the majority of the 20 million square kilometer Antarctic sea ice habitat. On three cruises in marginal ice edge zones, spring 1983 (AMERIEZ I), autumn 1986 (AMERIEZ II), and late winter 1985 (Wintercruise I), considerable bacterial biomass and production was found throughout ice floes up to 2.22 m thick. We hypothesize that bacteria accumulate in pack ice as a result of both physical and biological processes. During the formation and growth of ice, physical processes act to concentrate and accumulate bacteria within the ice matrix. This is followed by in situ growth along physiochemical gradients found in several sea ice microhabitats. Bacterial biomass and production in ice were equal to that present in several meters of underlying seawater during all seasons. Among microhabitats, highest bacterial production and most rapid rates of growth ( >1 d -1) were found in saline ponds on the surface of floes and porewater in the interior of floes. Bacterial carbon production ranged from 2% of primary production in surface brash to 45-221% of primary production in surface ponds and porewater. Bacterial growth and microalgal photosynthetic metabolism in pack ice appear to be coupled in a fashion similar to that described for fast ice. The presence of substantial numbers of active, feeding protozoans and metazoans in pack ice suggests, albeit indirectly, that bacterial production supports microheterotrophs of the microbial loop, which in turn may support organisms at higher trophic levels. Bacterial growth in pack ice may be important to the potential for primary production. Thus ice bacteria may provide remineralized inorganic nutrients necessary for continued microalgal growth in localized microhabitats within the ice or they may compete with algae for nutrients. Upon release from melting ice, actively growing bacteria also contribute to microbial biomass in seawater. From these

  2. Comparison of ice nuclei from fruit juices and their properties

    NASA Astrophysics Data System (ADS)

    Fiala, Bianca; Felgitsch, Laura; Grothe, Hinrich

    2017-04-01

    Heterogeneous ice nucleation is a crucial process in the atmosphere. Recent findings indicate the importance of biological ice nuclei (IN) in this process. Pratt et al. (2009) sampled ice-crystal residues at approx. 8 km high altitude over Wyoming, U.S.. They found a third of the dry residues to be biological and further that 60% of the highly abundant mineral dusts to be internally mixed with biological or humic substances. Huffman et al. (2013) showed a burst of biological IN over woodlands connected to rain events. Previous investigations in our group (Pummer et al. 2012) showed that pollen and pollen washing water from several plants native to the boreal forests trigger heterogeneous ice nucleation. Recent work from our group (Felgitsch et al. 2016) showed that several juices of berries are ice nucleation active. Based on this research we examined ice nucleation activity (INA) and general properties of five juices: sea buckthorn, black currant, chokeberry, acerola, and elder berry. We elucidated particle size dependency of the ice nucleation activity to differentiate between coarse ice nucleating particles and nanoparticles or macromolecules. Investigations with different solvents and with chaotropic agents were performed in order to further clarify properties concerning chemical polarity of the IN, and the importance of hydrogen bonds and other structure forming polar interactions. The results are compared to known plant originated IN. Our results suggest similarities in terms of nucleation temperature and structure stability between different IN of plant materials. These properties show a clear differentiation to known bacterial and fungal IN. Felgitsch , L., Bichler, M., Häusler, T., Hitzenberger, R., and Grothe, H.: Heterogeneous freezing of water triggered by berry juices from perenneal plants, submitted, 2016. Huffman, J.A., Prenni, A.J., DeMott, P.J., Pöhlker, C., Mason, R.H., Robinson, N.H., Frohlich-Nowoisky, J., Tobo, Y., Després, V.R., Garcia, E

  3. Analysis of Expression of a Phenazine Biosynthesis Locus of Pseudomonas aureofaciens PGS12 on Seeds with a Mutant Carrying a Phenazine Biosynthesis Locus-Ice Nucleation Reporter Gene Fusion

    PubMed Central

    Georgakopoulos, Dimitrios G.; Hendson, Mavis; Panopoulos, Nickolas J.; Schroth, Milton N.

    1994-01-01

    A derivative of Pseudomonas aureofaciens PGS12 expressing a promoterless ice nucleation gene under the control of a phenazine biosynthesis locus was used to study the expression of a phenazine antibiotic locus (Phz) during bacterial seed colonization. Seeds of various plants were inoculated with wild-type PGS12 and a PGS12 ice nucleation-active phz:inaZ marker exchange derivative and planted in soil, and the expression of the reporter gene was monitored at different intervals for 48 h during seed germination. phz gene expression was first detected 12 h after planting, and the expression increased during the next 36-h period. Significant differences in expression of bacterial populations on different seeds were measured at 48 h. The highest expression level was recorded for wheat seeds (one ice nucleus per 4,000 cells), and the lowest expression level was recorded for cotton seeds (one ice nucleus per 12,000,000 cells). These values indicate that a small proportion of bacteria in a seed population expressed phenazine biosynthesis. Reporter gene expression levels and populations on individual seeds in a sample were lognormally distributed. There was greater variability in reporter gene expression than in population size among individual seeds in a sample. Expression on sugar beet and radish seeds was not affected by different inoculum levels or soil matric potentials of -10 and -40 J/kg; only small differences in expression on wheat and sugar beet seeds were detected when the seeds were planted in various soils. It is suggested that the nutrient level in seed exudates is the primary reason for the differences observed among seeds. The lognormal distribution of phenazine expression on seeds and the timing and difference in expression of phenazine biosynthesis on seeds have implications for the potential efficacy of biocontrol microorganisms against plant pathogens. PMID:16349467

  4. Isolation, Characterization, and Ecology of Cold-Active, Chemolithotrophic, Sulfur-Oxidizing Bacteria from Perennially Ice-Covered Lake Fryxell, Antarctica

    PubMed Central

    Sattley, W. Matthew; Madigan, Michael T.

    2006-01-01

    Novel strains of obligately chemolithoautotrophic, sulfur-oxidizing bacteria have been isolated from various depths of Lake Fryxell, Antarctica. Physiological, morphological, and phylogenetic analyses showed these strains to be related to mesophilic Thiobacillus species, such as T. thioparus. However, the psychrotolerant Antarctic isolates showed an adaptation to cold temperatures and thus should be active in the nearly freezing waters of the lake. Enumeration by most-probable-number analysis in an oxic, thiosulfate-containing medium revealed that the sulfur-oxidizing chemolithotroph population peaks precisely at the oxycline (9.5 m), although viable cells exist well into the anoxic, sulfidic waters of the lake. The sulfur-oxidizing bacteria described here likely play a key role in the biogeochemical cycling of carbon and sulfur in Lake Fryxell. PMID:16885310

  5. Isolation, characterization, and ecology of cold-active, chemolithotrophic, sulfur-oxidizing bacteria from perennially ice-covered Lake Fryxell, Antarctica.

    PubMed

    Sattley, W Matthew; Madigan, Michael T

    2006-08-01

    Novel strains of obligately chemolithoautotrophic, sulfur-oxidizing bacteria have been isolated from various depths of Lake Fryxell, Antarctica. Physiological, morphological, and phylogenetic analyses showed these strains to be related to mesophilic Thiobacillus species, such as T. thioparus. However, the psychrotolerant Antarctic isolates showed an adaptation to cold temperatures and thus should be active in the nearly freezing waters of the lake. Enumeration by most-probable-number analysis in an oxic, thiosulfate-containing medium revealed that the sulfur-oxidizing chemolithotroph population peaks precisely at the oxycline (9.5 m), although viable cells exist well into the anoxic, sulfidic waters of the lake. The sulfur-oxidizing bacteria described here likely play a key role in the biogeochemical cycling of carbon and sulfur in Lake Fryxell.

  6. Boreal pollen contain ice-nucleating as well as ice-binding ‘antifreeze’ polysaccharides

    PubMed Central

    Dreischmeier, Katharina; Budke, Carsten; Wiehemeier, Lars; Kottke, Tilman; Koop, Thomas

    2017-01-01

    Ice nucleation and growth is an important and widespread environmental process. Accordingly, nature has developed means to either promote or inhibit ice crystal formation, for example ice-nucleating proteins in bacteria or ice-binding antifreeze proteins in polar fish. Recently, it was found that birch pollen release ice-nucleating macromolecules when suspended in water. Here we show that birch pollen washing water exhibits also ice-binding properties such as ice shaping and ice recrystallization inhibition, similar to antifreeze proteins. We present spectroscopic evidence that both the ice-nucleating as well as the ice-binding molecules are polysaccharides bearing carboxylate groups. The spectra suggest that both polysaccharides consist of very similar chemical moieties, but centrifugal filtration indicates differences in molecular size: ice nucleation occurs only in the supernatant of a 100 kDa filter, while ice shaping is strongly enhanced in the filtrate. This finding may suggest that the larger ice-nucleating polysaccharides consist of clusters of the smaller ice-binding polysaccharides, or that the latter are fragments of the ice-nucleating polysaccharides. Finally, similar polysaccharides released from pine and alder pollen also display both ice-nucleating as well as ice-binding ability, suggesting a common mechanism of interaction with ice among several boreal pollen with implications for atmospheric processes and antifreeze protection. PMID:28157236

  7. Boreal pollen contain ice-nucleating as well as ice-binding ‘antifreeze’ polysaccharides

    NASA Astrophysics Data System (ADS)

    Dreischmeier, Katharina; Budke, Carsten; Wiehemeier, Lars; Kottke, Tilman; Koop, Thomas

    2017-02-01

    Ice nucleation and growth is an important and widespread environmental process. Accordingly, nature has developed means to either promote or inhibit ice crystal formation, for example ice-nucleating proteins in bacteria or ice-binding antifreeze proteins in polar fish. Recently, it was found that birch pollen release ice-nucleating macromolecules when suspended in water. Here we show that birch pollen washing water exhibits also ice-binding properties such as ice shaping and ice recrystallization inhibition, similar to antifreeze proteins. We present spectroscopic evidence that both the ice-nucleating as well as the ice-binding molecules are polysaccharides bearing carboxylate groups. The spectra suggest that both polysaccharides consist of very similar chemical moieties, but centrifugal filtration indicates differences in molecular size: ice nucleation occurs only in the supernatant of a 100 kDa filter, while ice shaping is strongly enhanced in the filtrate. This finding may suggest that the larger ice-nucleating polysaccharides consist of clusters of the smaller ice-binding polysaccharides, or that the latter are fragments of the ice-nucleating polysaccharides. Finally, similar polysaccharides released from pine and alder pollen also display both ice-nucleating as well as ice-binding ability, suggesting a common mechanism of interaction with ice among several boreal pollen with implications for atmospheric processes and antifreeze protection.

  8. Boreal pollen contain ice-nucleating as well as ice-binding 'antifreeze' polysaccharides.

    PubMed

    Dreischmeier, Katharina; Budke, Carsten; Wiehemeier, Lars; Kottke, Tilman; Koop, Thomas

    2017-02-03

    Ice nucleation and growth is an important and widespread environmental process. Accordingly, nature has developed means to either promote or inhibit ice crystal formation, for example ice-nucleating proteins in bacteria or ice-binding antifreeze proteins in polar fish. Recently, it was found that birch pollen release ice-nucleating macromolecules when suspended in water. Here we show that birch pollen washing water exhibits also ice-binding properties such as ice shaping and ice recrystallization inhibition, similar to antifreeze proteins. We present spectroscopic evidence that both the ice-nucleating as well as the ice-binding molecules are polysaccharides bearing carboxylate groups. The spectra suggest that both polysaccharides consist of very similar chemical moieties, but centrifugal filtration indicates differences in molecular size: ice nucleation occurs only in the supernatant of a 100 kDa filter, while ice shaping is strongly enhanced in the filtrate. This finding may suggest that the larger ice-nucleating polysaccharides consist of clusters of the smaller ice-binding polysaccharides, or that the latter are fragments of the ice-nucleating polysaccharides. Finally, similar polysaccharides released from pine and alder pollen also display both ice-nucleating as well as ice-binding ability, suggesting a common mechanism of interaction with ice among several boreal pollen with implications for atmospheric processes and antifreeze protection.

  9. Ice nucleation by soil dust compared to desert dust aerosols

    NASA Astrophysics Data System (ADS)

    Moehler, O.; Steinke, I.; Ullrich, R.; Höhler, K.; Schiebel, T.; Hoose, C.; Funk, R.

    2015-12-01

    A minor fraction of atmospheric aerosol particles, so-called ice-nucleating particles (INPs), initiates the formation of the ice phase in tropospheric clouds and thereby markedly influences the Earth's weather and climate systems. Whether an aerosol particle acts as an INP depends on its size, morphology and chemical compositions. The INP fraction of certain aerosol types also strongly depends on the temperature and the relative humidity. Because both desert dust and soil dust aerosols typically comprise a variety of different particles, it is difficult to assess and predict their contribution to the atmospheric INP abundance. This requires both accurate modelling of the sources and atmospheric distribution of atmospheric dust components and detailed investigations of their ice nucleation activities. The latter can be achieved in laboratory experiments and parameterized for use in weather and climate models as a function of temperature and particle surface area, a parameter called ice-nucleation active site (INAS) density. Concerning ice nucleation activity studies, the soil dust is of particular interest because it contains a significant fraction of organics and biological components, both with the potential for contributing to the atmospheric INP abundance at relatively high temperatures compared to mineral components. First laboratory ice nucleation experiments with a few soil dust samples indicated their INP fraction to be comparable or slightly enhanced to that of desert dust. We have used the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud simulation chamber to study the immersion freezing ability of four different arable soil dusts, sampled in Germany, China and Argentina. For temperatures higher than about -20°C, we found the INP fraction of aerosols generated from these samples by a dry dispersion technique to be significantly higher compared to various desert dust aerosols also investigated in AIDA experiments. In this contribution, we

  10. Dilution-to-extinction culturing of psychrotolerant planktonic bacteria from permanently ice-covered lakes in the McMurdo Dry Valleys, Antarctica.

    PubMed

    Stingl, U; Cho, J-C; Foo, W; Vergin, K L; Lanoil, B; Giovannoni, S J

    2008-04-01

    Lakes in the McMurdo Dry Valleys of Antarctica are characterized by a permanent ice cover and little or no anthropogenic influence. Although bacterial cultures have been obtained from these habitats, recent culture-independent studies indicate that the most abundant microbes in these systems are not yet cultivated. By using dilution-to-extinction cultivation methods with sterilized and nutrient-amended lake water as media, we isolated 148 chemotrophic psychrotolerant bacterial cultures from fresh surface water of Lake Fryxell and the east lobe of Lake Bonney and the hypersaline, suboxic bottom water from the west lobes of Lake Bonney. Screening of the 16S ribosomal ribonucleic acid (rRNA) genes of the cultures by restriction fragment length polymorphism (RFLP) yielded 57 putatively pure psychrotolerant, slow growing cultures grouped into 18 clusters. The sequencing of 16S rRNA genes of randomly selected representatives of each RFLP cluster revealed that the corresponding isolates belong to the Alphaproteobacteria (six RFLP patterns), Betaproteobacteria (six RFLP patterns), Bacteroidetes (four RFLP patterns), and Actinobacteria (two RFLP patterns). Phylogenetic analysis of the sequences showed that the vast majority of the isolates were not closely related to previously described species. Thirteen of 18 RFLP patterns shared a 16S ribosomal deoxyribonucleic acid sequence similarity of 97% or less with the closest described species, and four isolates had a sequence similarity of 93% or less with the nearest described species. Phylogenetic analysis showed that these sequences were representatives of deeply branching organisms in the respective phylum. A comparison of the isolates with 16S rRNA clone libraries prepared from the same environments showed substantial overlap, indicating that dilution-to-extinction culturing in natural lake water media can help isolate some of the most abundant organisms in these perennially ice-covered lakes.

  11. Ice Bridge Antarctic Sea Ice

    NASA Image and Video Library

    2009-10-21

    Sea ice is seen out the window of NASA's DC-8 research aircraft as it flies 2,000 feet above the Bellingshausen Sea in West Antarctica on Wednesday, Oct., 21, 2009. This was the fourth science flight of NASA’s Operation Ice Bridge airborne Earth science mission to study Antarctic ice sheets, sea ice, and ice shelves. Photo Credit: (NASA/Jane Peterson)

  12. Unique nucleation activity of inorganic fullerene-like WS2 nanoparticles in polyphenylene sulfide nanocomposites: isokinetic and isoconversional study of dynamic crystallization kinetics.

    PubMed

    Naffakh, Mohammed; Marco, Carlos; Gómez, Marián A; Jiménez, Ignacio

    2009-05-21

    The dynamic crystallization kinetics of polyphenylene sulfide (PPS) nanocomposites with inorganic fullerene WS2 nanopartices (IF-WS2) content varying from 0.05 to 8 wt % has been studied using differential scanning calorimetry (DSC). The analysis of the crystallization at different cooling rates demonstrates that the completely isokinetic description of the crystallization process is not possible. However, the isoconversional methods in combination with the JMAEK equation provide a better understanding of the kinetics of the dynamic crystallization process. The addition of IF-WS2 influences the crystallization kinetics of PPS but in ways unexpected for polymer nanocomposites. A drastic change from retardation to promotion of crystallization is observed with increasing nanoparticle content. In the same way, the results of the nucleation activity and the effective energy barrier confirmed the unique dependence of the crystallization behavior of PPS on composition. In addition, the morphological data obtained from the polarized optical microscopy (POM) and time-resolved synchrotron X-ray diffraction is consistent with results of the crystallization kinetics of PPS/IF-WS2 nanocomposites.

  13. Advances in heterogeneous ice nucleation research: Theoretical modeling and measurements

    NASA Astrophysics Data System (ADS)

    Beydoun, Hassan

    In the atmosphere, cloud droplets can remain in a supercooled liquid phase at temperatures as low as -40 °C. Above this temperature, cloud droplets freeze via heterogeneous ice nucleation whereby a rare and poorly understood subset of atmospheric particles catalyze the ice phase transition. As the phase state of clouds is critical in determining their radiative properties and lifetime, deficiencies in our understanding of heterogeneous ice nucleation poses a large uncertainty on our efforts to predict human induced global climate change. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established model and parameterizations that accurately predict heterogeneous ice nucleation. Conversely, the sparsity of reliable measurement techniques available struggle to be interpreted by a single consistent theoretical or empirical framework, which results in layers of uncertainty when attempting to extrapolate useful information regarding ice nucleation for use in atmospheric cloud models. In this dissertation a new framework for describing heterogeneous ice nucleation is developed. Starting from classical nucleation theory, the surface of an ice nucleating particle is treated as a continuum of heterogeneous ice nucleating activity and a particle specific distribution of this activity g is derived. It is hypothesized that an individual particle species exhibits a critical surface area. Above this critical area the ice nucleating activity of a particle species can be described by one g distribution, g, while below it g expresses itself expresses externally resulting in particle to particle variability in ice nucleating activity. The framework is supported by cold plate droplet freezing measurements for dust and biological particles in which the total surface area of particle material available is varied. Freezing spectra above a certain surface area

  14. Sea Ice

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.; Cavalieri, Donald J.

    2005-01-01

    Sea ice covers vast areas of the polar oceans, with ice extent in the Northern Hemisphere ranging from approximately 7 x 10(exp 6) sq km in September to approximately 15 x 10(exp 6) sq km in March and ice extent in the Southern Hemisphere ranging from approximately 3 x 10(exp 6) sq km in February to approximately 18 x 10(exp 6) sq km in September. These ice covers have major impacts on the atmosphere, oceans, and ecosystems of the polar regions, and so as changes occur in them there are potential widespread consequences. Satellite data reveal considerable interannual variability in both polar sea ice covers, and many studies suggest possible connections between the ice and various oscillations within the climate system, such as the Arctic Oscillation, North Atlantic Oscillation, and Antarctic Oscillation, or Southern Annular Mode. Nonetheless, statistically significant long-term trends are also apparent, including overall trends of decreased ice coverage in the Arctic and increased ice coverage in the Antarctic from late 1978 through the end of 2003, with the Antarctic ice increases following marked decreases in the Antarctic ice during the 1970s. For a detailed picture of the seasonally varying ice cover at the start of the 21st century, this chapter includes ice concentration maps for each month of 2001 for both the Arctic and the Antarctic, as well as an overview of what the satellite record has revealed about the two polar ice covers from the 1970s through 2003.

  15. Surface structure, crystallographic and ice-nucleating properties of cellulose

    NASA Astrophysics Data System (ADS)

    Hiranuma, Naruki; Möhler, Ottmar; Kiselev, Alexei; Saathoff, Harald; Weidler, Peter; Shutthanandan, Shuttha; Kulkarni, Gourihar; Jantsch, Evelyn; Koop, Thomas

    2015-04-01

    Increasing evidence of the high diversity and efficient freezing ability of biological ice-nucleating particles is driving a reevaluation of their impact upon climate. Despite their potential importance, little is known about their atmospheric abundance and ice nucleation efficiency, especially non-proteinaceous ones, in comparison to non-biological materials (e.g., mineral dust). Recently, microcrystalline cellulose (MCC; non-proteinaceous plant structural polymer) has been identified as a potential biological ice-nucleating particle. However, it is still uncertain if the ice-nucleating activity is specific to the MCC structure or generally relevant to all cellulose materials, such that the results of MCC can be representatively scaled up to the total cellulose content in the atmosphere to address its role in clouds and the climate system. Here we use the helium ion microscopy (HIM) imaging and the X-ray diffraction (XRD) technique to characterize the nanoscale surface structure and crystalline properties of the two different types of cellulose (MCC and fibrous cellulose extracted from natural wood pulp) as model proxies for atmospheric cellulose particles and to assess their potential accessibility for water molecules. To complement these structural characterizations, we also present the results of immersion freezing experiments using the cold stage-based droplet freezing BINARY (Bielefeld Ice Nucleation ARaY) technique. The HIM results suggest that both cellulose types have a complex porous morphology with capillary spaces between the nanoscale fibrils over the microfiber surface. These surface structures may make cellulose accessible to water. The XRD results suggest that the structural properties of both cellulose materials are in agreement (i.e., P21 space group; a=7.96 Å, b=8.35 Å, c=10.28 Å) and comparable to the crystallographic properties of general monoclinic cellulose (i.e., Cellulose Iβ). The results obtained from the BINARY measurements suggest

  16. Anaerobic bacteria

    MedlinePlus

    Anaerobic bacteria are bacteria that do not live or grow when oxygen is present. In humans, these bacteria ... Goldstein EJ. Diseases caused by non-spore forming anaerobic bacteria. In: Goldman L, Schafer AI, eds. Goldman's Cecil ...

  17. Molecular Study of the Effects of Chemical Processing on Heterogeneous Ice Nucleation: Role of Active Sites and Product Formation

    NASA Astrophysics Data System (ADS)

    Sihvonen, S.; Schill, G. P.; Murphy, K. A.; Mueller, K.; Tolbert, M. A.; Freedman, M. A.

    2014-12-01

    Mineral dust aerosol is the largest global source of ice nuclei, but the identity of the active sites for nucleation is unknown. During atmospheric transport, mineral dust aerosol can encounter and react with sulfuric acid, which affects the ice nucleation activity either due to changes to reactive surface sites or product formation. In this study, we reacted two types of clays found in mineral dust, kaolinite and montmorillonite, with sulfuric acid. Variation in the mineral due to acid treatment was separated from product formation through rinsing techniques. The samples were subsequently reacted with a probe molecule, (3,3,3-trifluoropropyl)dimethylchlorosilane, that selectively binds to edge hydroxyl groups that are bonded to a silicon atom with three bridging oxygens. Hydroxyl groups are considered potential active sites, because they can hydrogen bond with water and facilitate ice nucleation. Attachment to these sites was quantified by 19F magic angle spinning nuclear magnetic resonance (MAS NMR) of the 19F atoms on the probe molecule, which provided a direct correlation of the number of hydroxyl groups. Our results indicate that the number of edge-site hydroxyl groups increases with exposure to acid. Ice nucleation measurements indicate that the sulfuric acid-treated mineral is less ice active than the untreated mineral. Surprisingly, no difference between the nucleation activity of the untreated mineral and acid-treated, rinsed mineral is observed. As a result, we hypothesize that once a critical density of active sites is reached for ice nucleation, there is no further change in nucleation activity despite a continued increase in active sites. We additionally propose that the reduced activity of the acid-treated mineral is due to product formation that blocks active sites on the mineral, rather than changes to active sites.

  18. Ice Stars

    NASA Image and Video Library

    2017-09-27

    Ice Stars - August 4th, 2002 Description: Like distant galaxies amid clouds of interstellar dust, chunks of sea ice drift through graceful swirls of grease ice in the frigid waters of Foxe Basin near Baffin Island in the Canadian Arctic. Sea ice often begins as grease ice, a soupy slick of tiny ice crystals on the ocean's surface. As the temperature drops, grease ice thickens and coalesces into slabs of more solid ice. Credit: USGS/NASA/Landsat 7 To learn more about the Landsat satellite go to: landsat.gsfc.nasa.gov/ NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

  19. Over Ice

    NASA Image and Video Library

    All about NASA's IceBridge P-3B plane and its IceBridge retrofit. Upgraded with 21st century "special modifications", the aircraft is less a cold war relic and more like the Space Agency's Millenni...

  20. Heterogeneous nucleation of ice on anthropogenic organic particles collected in Mexico City

    SciTech Connect

    Knopf, D.A.; Wang, B.; Laskin, A.; Moffet, R.C.; Gilles, M.K.

    2010-06-20

    This study reports on heterogeneous ice nucleation activity of predominantly organic (or coated with organic material) anthropogenic particles sampled within and around the polluted environment of Mexico City. The onset of heterogeneous ice nucleation was observed as a function of particle temperature (Tp), relative humidity (RH), nucleation mode, and particle chemical composition which is influenced by photochemical atmospheric aging. Particle analyses included computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). In contrast to most laboratory studies employing proxies of organic aerosol, we show that anthropogenic organic particles collected in Mexico City can potentially induce ice nucleation at experimental conditions relevant to cirrus formation. The results suggest a new precedent for the potential impact of organic particles on ice cloud formation and climate.

  1. Heterogeneous Nucleation of Ice on Anthropogenic Organic Particles Collected in Mexico City

    SciTech Connect

    Knopf, Daniel A.; Wang, BingBing; Laskin, Alexander; Moffet, Ryan C.; Gilles, Marry K.

    2010-06-05

    This study reports on heterogeneous ice nucleation activity of predominantly organic or coated with organic material anthropogenic particles sampled within and around the polluted environment of Mexico City. The onset of heterogeneous ice nucleation was observed as a function of particle temperature (Tp), relative humidity (RH), nucleation mode, and chemical composition of particles influenced by their photochemical atmospheric aging. Particle analyses was conducted using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). In contrast to the majority of laboratory studies employing proxies of organic aerosol, we show that anthropogenic organic particles collected in Mexico City have can potentially induce ice nucleation at experimental conditions relevant to cirrus formation. The reported results suggest a new paradigm for the potential impact of organic particles on ice cloud formation and climate.

  2. Ice-Binding Proteins and Their Function.

    PubMed

    Bar Dolev, Maya; Braslavsky, Ido; Davies, Peter L

    2016-06-02

    Ice-binding proteins (IBPs) are a diverse class of proteins that assist organism survival in the presence of ice in cold climates. They have different origins in many organisms, including bacteria, fungi, algae, diatoms, plants, insects, and fish. This review covers the gamut of IBP structures and functions and the common features they use to bind ice. We discuss mechanisms by which IBPs adsorb to ice and interfere with its growth, evidence for their irreversible association with ice, and methods for enhancing the activity of IBPs. The applications of IBPs in the food industry, in cryopreservation, and in other technologies are vast, and we chart out some possibilities.

  3. The relevance of nanoscale biological fragments for ice nucleation in clouds

    NASA Astrophysics Data System (ADS)

    O‧Sullivan, D.; Murray, B. J.; Ross, J. F.; Whale, T. F.; Price, H. C.; Atkinson, J. D.; Umo, N. S.; Webb, M. E.

    2015-01-01

    Most studies of the role of biological entities as atmospheric ice-nucleating particles have focused on relatively rare supermicron particles such as bacterial cells, fungal spores and pollen grains. However, it is not clear that there are sufficient numbers of these particles in the atmosphere to strongly influence clouds. Here we show that the ice-nucleating activity of a fungus from the ubiquitous genus Fusarium is related to the presence of nanometre-scale particles which are far more numerous, and therefore potentially far more important for cloud glaciation than whole intact spores or hyphae. In addition, we quantify the ice-nucleating activity of nano-ice nucleating particles (nano-INPs) washed off pollen and also show that nano-INPs are present in a soil sample. Based on these results, we suggest that there is a reservoir of biological nano-INPs present in the environment which may, for example, become aerosolised in association with fertile soil dust particles.

  4. The relevance of nanoscale biological fragments for ice nucleation in clouds.

    PubMed

    O'Sullivan, D; Murray, B J; Ross, J F; Whale, T F; Price, H C; Atkinson, J D; Umo, N S; Webb, M E

    2015-01-28

    Most studies of the role of biological entities as atmospheric ice-nucleating particles have focused on relatively rare supermicron particles such as bacterial cells, fungal spores and pollen grains. However, it is not clear that there are sufficient numbers of these particles in the atmosphere to strongly influence clouds. Here we show that the ice-nucleating activity of a fungus from the ubiquitous genus Fusarium is related to the presence of nanometre-scale particles which are far more numerous, and therefore potentially far more important for cloud glaciation than whole intact spores or hyphae. In addition, we quantify the ice-nucleating activity of nano-ice nucleating particles (nano-INPs) washed off pollen and also show that nano-INPs are present in a soil sample. Based on these results, we suggest that there is a reservoir of biological nano-INPs present in the environment which may, for example, become aerosolised in association with fertile soil dust particles.

  5. The relevance of nanoscale biological fragments for ice nucleation in clouds

    PubMed Central

    O′Sullivan, D.; Murray, B. J.; Ross, J. F.; Whale, T. F.; Price, H. C.; Atkinson, J. D.; Umo, N. S.; Webb, M. E.

    2015-01-01

    Most studies of the role of biological entities as atmospheric ice-nucleating particles have focused on relatively rare supermicron particles such as bacterial cells, fungal spores and pollen grains. However, it is not clear that there are sufficient numbers of these particles in the atmosphere to strongly influence clouds. Here we show that the ice-nucleating activity of a fungus from the ubiquitous genus Fusarium is related to the presence of nanometre-scale particles which are far more numerous, and therefore potentially far more important for cloud glaciation than whole intact spores or hyphae. In addition, we quantify the ice-nucleating activity of nano-ice nucleating particles (nano-INPs) washed off pollen and also show that nano-INPs are present in a soil sample. Based on these results, we suggest that there is a reservoir of biological nano-INPs present in the environment which may, for example, become aerosolised in association with fertile soil dust particles. PMID:25626414

  6. Bacterial recovery from ancient glacial ice.

    PubMed

    Christner, Brent C; Mosley-Thompson, Ellen; Thompson, Lonnie G; Reeve, John N

    2003-05-01

    Ice that forms the bottom 18 m of a 308 m ice core drilled from the Guliya ice cap on the Qinghan-Tibetan plateau in Western China is over 750000 years old and is the oldest glacial ice known to date. Fourteen bacterial isolates have been recovered from samples of this ice from approximately 296 m below the surface (mbs). Based on 16S rDNA sequences, these are members of the alpha- and beta-proteobacterial, actinobacterial and low-G + C Gram-positive bacterial lineages. 16S rDNA molecules have also been amplified directly, cloned and sequenced from the ice-core melt water. These originated from Pseudomonas and Acinetobacter gamma-proteobacterial species. These results demonstrate that bacteria can be recovered from water ice that has frozen for time periods relevant to biological survival through terrestrial ice ages or during interplanetary transport.

  7. Ice nucleation by cellulose and its potential impact on clouds and climate

    NASA Astrophysics Data System (ADS)

    Hiranuma, Naruki; Möhler, Ottmar; Yamashita, Katsuya; Tajiri, Takuya; Saito, Atsushi; Kiselev, Alexei; Hoose, Corinna; Murakami, Masataka

    2014-05-01

    Biological aerosol particles have recently been accentuated by their efficient ice nucleating activity as well as potential impact on clouds and global climate. Despite their potential importance, little is known about the abundance of biological particles in the atmosphere and their role compared to non-biological material and, consequently, their potential role in the cloud-hydrology and climate system is also poorly constrained. However, field observations show that the concentration of airborne cellulose, which is one of the most important derivatives of glucose and atmospherically relevant biopolymers, is consistently prevalent (>10 ng per cubic meter) throughout the whole year even at remote- and elevated locations. Here we use a novel cloud simulation chamber in Tsukuba, Japan to demonstrate that airborne cellulose of biological origin can act as efficient ice nucleating particles in super-cooled clouds of the lower and middle troposphere. In specific, we measured the surface-based ice nucleation activity of microcrystalline cellulose particles immersed in cloud droplets, which may add crucial importance to further quantify the role of biological particles as ice nuclei in the troposphere. Our results suggest that the concentration of ice nucleating cellulose to become significant (>0.1 per liter) below about -17 °C and nearly comparable to other known ice nucleating clay mineral particles (e.g., illite rich clay mineral - INUIT comparisons are also presented). An important and unique characteristic of microcrystalline cellulose compared to other particles of biological origin is its high molecular packing density, enhancing resistance to hydrolysis degradation. More in-depth microphysical understandings as well as quantitative observations of ice nucleating cellulose particles in the atmosphere are necessary to allow better estimates of their effects on clouds and the global climate. Acknowledgement: We acknowledge support by German Research Society (Df

  8. Ice Bridge Antarctic Sea Ice

    NASA Image and Video Library

    2009-10-21

    An iceberg is seen out the window of NASA's DC-8 research aircraft as it flies 2,000 feet above the Amundsen Sea in West Antarctica on Wednesday, Oct., 21, 2009. This was the fourth science flight of NASA’s Operation Ice Bridge airborne Earth science mission to study Antarctic ice sheets, sea ice, and ice shelves. Photo Credit: (NASA/Jane Peterson)

  9. The adsorption of fungal ice-nucleating proteins on mineral dusts: a terrestrial reservoir of atmospheric ice-nucleating particles

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Daniel; Murray, Benjamin J.; Ross, James; Webb, Michael E.

    2016-04-01

    The occurrence of ice-nucleating particles (INPs) in our atmosphere has a profound impact on the properties and lifetime of supercooled clouds. However, the identities, sources and abundances of airborne particles capable of efficiently nucleating ice at relatively low supercoolings (T > -15 °C) remain enigmatic. Recently, several studies have suggested that unidentified biogenic residues in soil dusts are likely to be an important source of these efficient atmospheric INPs. While it has been shown that cell-free proteins produced by common soil-borne fungi are exceptional INPs, whether these fungi are a source of ice-nucleating biogenic residues in soils has yet to be shown. In particular, it is unclear whether upon adsorption to soil mineral particles, the activity of fungal ice-nucleating proteins is retained or is reduced, as observed for other soil enzymes. Here we show that proteins from a common soil fungus (Fusarium avenaceum) do in fact preferentially bind to and impart their ice-nucleating properties to the common clay mineral kaolinite. The ice-nucleating activity of the proteinaceous INPs is found to be unaffected by adsorption to the clay, and once bound the proteins do not readily desorb, retaining much of their activity even after multiple washings with pure water. The atmospheric implications of the finding that nanoscale fungal INPs can effectively determine the nucleating abilities of lofted soil dusts are discussed.

  10. The adsorption of fungal ice-nucleating proteins on mineral dusts: a terrestrial reservoir of atmospheric ice-nucleating particles

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Daniel; Murray, Benjamin J.; Ross, James F.; Webb, Michael E.

    2016-06-01

    The occurrence of ice-nucleating particles (INPs) in our atmosphere has a profound impact on the properties and lifetime of supercooled clouds. To date, the identities, sources and abundances of particles capable of nucleating ice at relatively low supercoolings (T > -15 °C) remain enigmatic. While biomolecules such as proteins and carbohydrates have been implicated as important high-temperature INPs, the lack of knowledge on the environmental fates of these species makes it difficult to assess their potential atmospheric impacts. Here we show that such nanoscale ice-nucleating proteins from a common soil-borne fungus (Fusarium avenaceum) preferentially bind to and confer their ice-nucleating properties to kaolinite. The ice-nucleating activity of the proteinaceous INPs is unaffected by adsorption to the clay, and once bound the proteins do not readily desorb, retaining much of the activity even after multiple washings with pure water. The atmospheric implications of the finding that biological residues can confer their ice-nucleating ability to dust particles are discussed.

  11. Investigation of heterogeneous ice nucleation in pollen suspensions and washing water

    NASA Astrophysics Data System (ADS)

    Dreischmeier, Katharina; Budke, Carsten; Koop, Thomas

    2014-05-01

    Biological particles such as pollen often show ice nucleation activity at temperatures higher than -20 °C. Immersion freezing experiments of pollen washing water demonstrate comparable ice nucleation behaviour as water containing the whole pollen bodies (Pummer et al., 2012). It was suggested that polysaccharide molecules leached from the grains are responsible for the ice nucleation. Here, heterogeneous ice nucleation in birch pollen suspensions and their washing water was investigated by two different experimental methods. The optical freezing array BINARY (Bielefeld Ice Nucleation ARraY) allows the direct observation of freezing of microliter-sized droplets. The IN spectra obtained from such experiments with birch pollen suspensions over a large concentration range indicate several different ice nucleation active species, two of which are present also in the washing water. The latter was probed also in differential scanning calorimeter (DSC) experiments of emulsified sub-picoliter droplets. Due to the small droplet size in the emulsion samples and at small concentration of IN in the washing water, such DSC experiments can exhibit the ice nucleation behaviour of a single nucleus. The two heterogeneous freezing signals observed in the DSC thermograms can be assigned to two different kinds of ice nuclei, confirming the observation from the BINARY measurements, and also previous studies on Swedish birch pollen washing water (Augustin et al., 2012). The authors gratefully acknowledge funding by the German Research Foundation (DFG) through the project BIOCLOUDS (KO 2944/1-1) and through the research unit INUIT (FOR 1525) under KO 2944/2-1. We particularly thank our INUIT partners for fruitful collaboration and sharing of ideas and IN samples. S. Augustin, H. Wex, D. Niedermeier, B. Pummer, H. Grothe, S. Hartmann, L. Tomsche, T. Clauss, J. Voigtländer, K. Ignatius, and F. Stratmann, Immersion freezing of birch pollen washing water, Atmos. Chem. Phys., 13, 10989

  12. A detailed study of ice nucleation by feldspar minerals

    NASA Astrophysics Data System (ADS)

    Whale, T. F.; Murray, B. J.; Wilson, T. W.; Carpenter, M. A.; Harrison, A.; Holden, M. A.; Vergara Temprado, J.; Morris, J.; O'Sullivan, D.

    2015-12-01

    Immersion mode heterogeneous ice nucleation plays a crucial role in controlling the composition of mixed phase clouds, which contain both supercooled liquid water and ice particles. The amount of ice in mixed phase clouds can affect cloud particle size, lifetime and extent and so affects radiative properties and precipitation. Feldspar minerals are probably the most important minerals for ice nucleation in mixed phase clouds because they nucleate ice more efficiently than other components of atmospheric mineral dust (Atkinson et al. 2013). The feldspar class of minerals is complex, containing numerous chemical compositions, several crystal polymorphs and wide variations in microscopic structure. Here we present the results of a study into ice nucleation by a wide range of different feldspars. We found that, in general, alkali feldspars nucleate ice more efficiently than plagioclase feldspars. However, we also found that particular alkali feldspars nucleate ice relatively inefficiently, suggesting that chemical composition is not the only important factor that dictates the ice nucleation efficiency of feldspar minerals. Ice nucleation by feldspar is described well by the singular model and is probably site specific in nature. The alkali feldspars that do not nucleate ice efficiently possess relatively homogenous structure on the micrometre scale suggesting that the important sites for nucleation are related to surface topography. Ice nucleation active site densities for the majority of tested alkali feldspars are similar to those found by Atkinson et al (2013), meaning that the validity of global aerosol modelling conducted in that study is not affected. Additionally, we have found that ice nucleation by feldspars is strongly influenced, both positively and negatively, by the solute content of droplets. Most other nucleants we have tested are unaffected by solutes. This provides insight into the mechanism of ice nucleation by feldspars and could be of importance

  13. Sea ice terminology

    SciTech Connect

    Not Available

    1980-09-01

    A group of definitions of terms related to sea ice is presented, as well as a graphic representation of late winter ice zonation of the Beaufort Sea Coast. Terms included in the definition list are belt, bergy bit, bight, brash ice, calving, close pack ice, compacting, compact pack ice, concentration, consolidated pack ice, crack, diffuse ice edge, fast ice, fast-ice boundary, fast-ice edge, first-year ice, flaw, flaw lead, floe, flooded ice, fractured, fractured zone, fracturing, glacier, grey ice, grey-white ice, growler, hummock, iceberg, iceberg tongue, ice blink, ice boundary, ice cake, ice edge, ice foot, ice free, ice island, ice shelf, large fracture, lead, medium fracture, multiyear ice, nilas, old ice, open pack ice, open water, pack ice, polar ice, polynya, puddle, rafted ice, rafting, ram, ridge, rotten ice, second-year ice, shearing, shore lead, shore polynya, small fracture, strip, tabular berg, thaw holes, very close pack ice, very open pack ice, water sky, young coastal ice, and young ice.

  14. Sea Ice

    NASA Technical Reports Server (NTRS)

    Perovich, D.; Gerland, S.; Hendricks, S.; Meier, Walter N.; Nicolaus, M.; Richter-Menge, J.; Tschudi, M.

    2013-01-01

    During 2013, Arctic sea ice extent remained well below normal, but the September 2013 minimum extent was substantially higher than the record-breaking minimum in 2012. Nonetheless, the minimum was still much lower than normal and the long-term trend Arctic September extent is -13.7 per decade relative to the 1981-2010 average. The less extreme conditions this year compared to 2012 were due to cooler temperatures and wind patterns that favored retention of ice through the summer. Sea ice thickness and volume remained near record-low levels, though indications are of slightly thicker ice compared to the record low of 2012.

  15. Antifreeze and ice nucleator proteins in terrestrial arthropods.

    PubMed

    Duman, J G

    2001-01-01

    Terrestrial arthropods survive subzero temperatures by becoming either freeze tolerant (survive body fluid freezing) or freeze avoiding (prevent body fluid freezing). Protein ice nucleators (PINs), which limit supercooling and induce freezing, and antifreeze proteins (AFPs), which function to prevent freezing, can have roles in both freeze tolerance and avoidance. Many freeze-tolerant insects produce hemolymph PINs, which induce freezing at high subzero temperatures thereby inhibiting lethal intracellular freezing. Some freeze-tolerant species have AFPs that function as cryoprotectants to prevent freeze damage. Although the mechanism of this cryoprotection is not known, it may involve recrystallization inhibition and perhaps stabilization of the cell membrane. Freeze-avoiding species must prevent inoculative freezing initiated by external ice across the cuticle and extend supercooling abilities. Some insects remove PINs in the winter to promote supercooling, whereas others have selected against surfaces with ice-nucleating abilities on an evolutionary time scale. However, many freeze-avoiding species do have proteins with ice-nucleating activity, and these proteins must be masked in winter. In the beetle Dendroides canadensis, AFPs in the hemolymph and gut inhibit ice nucleators. Also, hemolymph AFPs and those associated with the layer of epidermal cells under the cuticle inhibit inoculative freezing. Two different insect AFPs have been characterized. One type from the beetles D. canadensis and Tenebrio molitor consists of 12- and 13-mer repeating units with disulfide bridges occurring at least every six residues. The spruce budworm AFP lacks regular repeat units. Both have much higher activities than any known AFPs.

  16. Ice Nuclei from Birch Trees

    NASA Astrophysics Data System (ADS)

    Felgitsch, Laura; Seifried, Teresa; Winkler, Philipp; Schmale, David, III; Grothe, Hinrich

    2017-04-01

    .H., Robinson, N.H., Frohlich-Nowoisky, J., Tobo, Y., Després, V.R., Garcia, E., Gochis, D.J., Harris, E., Müller-Germann, I., Ruzene, C., Schmer, B., Sinha, B., Day, D.A., Andreae, M.O., Jimenez, J.L., Gallagher, M., Kreidenweis, S.M., Bertram, A.K., and Pöschl, U.: High concentrations of biological aerosol particles and ice nuclei during and after rain, Atmos. Chem. Phys., 13, 1651-1664, 2013. Pummer, B.G., Bauer, H., Bernardi, J., Bleicher, S., and Grothe, H.: Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen, Atmos. Chem. Phys., 12, 2541-2550, 2012.

  17. Effects of different temperature treatments on biological ice nuclei in snow samples

    NASA Astrophysics Data System (ADS)

    Hara, Kazutaka; Maki, Teruya; Kakikawa, Makiko; Kobayashi, Fumihisa; Matsuki, Atsushi

    2016-09-01

    The heat tolerance of biological ice nucleation activity (INA) depends on their types. Different temperature treatments may cause varying degrees of inactivation on biological ice nuclei (IN) in precipitation samples. In this study, we measured IN concentration and bacterial INA in snow samples using a drop freezing assay, and compared the results for unheated snow and snow treated at 40 °C and 90 °C. At a measured temperature of -7 °C, the concentration of IN in untreated snow was 100-570 L-1, whereas the concentration in snow treated at 40 °C and 90 °C was 31-270 L-1 and 2.5-14 L-1, respectively. In the present study, heat sensitive IN inactivated by heating at 40 °C were predominant, and ranged 23-78% of IN at -7 °C compared with untreated samples. Ice nucleation active Pseudomonas strains were also isolated from the snow samples, and heating at 40 °C and 90 °C inactivated these microorganisms. Consequently, different temperature treatments induced varying degrees of inactivation on IN in snow samples. Differences in the concentration of IN across a range of treatment temperatures might reflect the abundance of different heat sensitive biological IN components.

  18. Differences in ice nucleation behavior of arable and desert soil dust in deposition nucleation regime

    NASA Astrophysics Data System (ADS)

    Ullrich, Romy; Vogel, Franziska; Möhler, Ottmar; Höhler, Kristina; Schiebel, Thea

    2017-04-01

    Soil dust from arid and semi-arid regions is one of the most abundant aerosol types in the atmosphere with emission rates of about 1600 Tg per year (Andreae et al. (2009)). Therewith, soil dust plays an important role for the atmospheric radiative transfer and also for the formation of clouds. Soil dust refers to dust sampled from agricultural used areas, to dust from bare soil as well as to dust from desert regions. By mass-spectrometric measurements of the chemical composition of ice residuals, mineral dust as component of soil dust was found to be the major heterogeneous ice nucleating particle (INP) type (e.g. Cziczo et al. (2013)), in particular in the upper troposphere. Also in laboratory studies the ice nucleation efficiency of the different soil dusts was investigated. It was shown that desert dusts (Ullrich et al. (2017)) as well as soil dusts from arable regions (O'Sullivan et al. (2014), Tobo et al. (2014)) are efficient INP. However, there is still a lack of data for ice nucleation on soil dusts for temperatures below about 220 K. With the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber, we are able to characterize the ice nucleation efficiency for different aerosol types to temperatures down to 180 K and high ice supersaturations. In order to extend the already existing AIDA data base for deposition nucleation on desert dusts and agricultural soil dusts, new experiments were done in the upper tropospheric temperature regime. This contribution will show the results of the new experiments with desert dust in comparison to existing data for higher temperatures. The first data analysis confirms the temperature dependent trend of the ice nucleation activity as discussed and parameterized in a recent paper by Ullrich et al. (2017). Furthermore, the update and extension of the recently published parameterization of deposition nucleation for desert dust to lower temperatures will be discussed. The experiments with agricultural soil

  19. Ice Surfaces

    NASA Astrophysics Data System (ADS)

    Shultz, Mary Jane

    2017-05-01

    Ice is a fundamental solid with important environmental, biological, geological, and extraterrestrial impact. The stable form of ice at atmospheric pressure is hexagonal ice, Ih. Despite its prevalence, Ih remains an enigmatic solid, in part due to challenges in preparing samples for fundamental studies. Surfaces of ice present even greater challenges. Recently developed methods for preparation of large single-crystal samples make it possible to reproducibly prepare any chosen face to address numerous fundamental questions. This review describes preparation methods along with results that firmly establish the connection between the macroscopic structure (observed in snowflakes, microcrystallites, or etch pits) and the molecular-level configuration (detected with X-ray or electron scattering techniques). Selected results of probing interactions at the ice surface, including growth from the melt, surface vibrations, and characterization of the quasi-liquid layer, are discussed.

  20. Modelling heterogeneous ice nucleation on mineral dust and soot with parameterizations based on laboratory experiments

    NASA Astrophysics Data System (ADS)

    Hoose, C.; Hande, L. B.; Mohler, O.; Niemand, M.; Paukert, M.; Reichardt, I.; Ullrich, R.

    2016-12-01

    Between 0 and -37°C, ice formation in clouds is triggered by aerosol particles acting as heterogeneous ice nuclei. At lower temperatures, heterogeneous ice nucleation on aerosols can occur at lower supersaturations than homogeneous freezing of solutes. In laboratory experiments, the ability of different aerosol species (e.g. desert dusts, soot, biological particles) has been studied in detail and quantified via various theoretical or empirical parameterization approaches. For experiments in the AIDA cloud chamber, we have quantified the ice nucleation efficiency via a temperature- and supersaturation dependent ice nucleation active site density. Here we present a new empirical parameterization scheme for immersion and deposition ice nucleation on desert dust and soot based on these experimental data. The application of this parameterization to the simulation of cirrus clouds, deep convective clouds and orographic clouds will be shown, including the extension of the scheme to the treatment of freezing of rain drops. The results are compared to other heterogeneous ice nucleation schemes. Furthermore, an aerosol-dependent parameterization of contact ice nucleation is presented.

  1. Importance of aerosol composition, mixing state, and morphology for heterogeneous ice nucleation: A combined field and laboratory approach

    NASA Astrophysics Data System (ADS)

    Baustian, Kelly J.; Cziczo, Daniel J.; Wise, Matthew E.; Pratt, Kerri A.; Kulkarni, Gourihar; Hallar, A. Gannet; Tolbert, Margaret A.

    2012-03-01

    In this study chemical compositions of background aerosol and ice nuclei were examined through laboratory investigations using Raman spectroscopy and field measurements by single-particle mass spectrometry. Aerosol sampling took place at Storm Peak Laboratory in Steamboat Springs, Colorado (elevation of 3210 m). A cascade impactor was used to collect coarse-mode aerosol particles for laboratory analysis by Raman spectroscopy; the composition, mixing state, and heterogeneous ice nucleation activity of individual particles were examined. For in situ analysis of fine-mode aerosol, ice nucleation on ambient particles was observed using a compact ice nucleation chamber. Ice crystals were separated from unactivated aerosol using a pumped counterflow virtual impactor, and ice nuclei were analyzed using particle analysis by laser mass spectrometry. For both fine and coarse modes, the ice nucleating particle fractions were enriched in minerals and depleted in sulfates and nitrates, compared to the background aerosol sampled. The vast majority of particles in both the ambient and ice active aerosol fractions contained a detectable amount of organic material. Raman spectroscopy showed that organic material is sometimes present in the form of a coating on the surface of inorganic particles. We find that some organic-containing particles serve as efficient ice nuclei while others do not. For coarse-mode aerosol, organic particles were only observed to initiate ice formation when oxygen signatures were also present in their spectra.

  2. Biological particles capable of triggering ice nucleation in the atmosphere

    NASA Astrophysics Data System (ADS)

    Felgitsch, Laura; Bichler, Magdalena; Vogel, André; Häusler, Thomas; Grothe, Hinrich

    2016-04-01

    Ice-nucleating particles (INPs) have a huge impact on atmospheric processes, since they can trigger ice cloud formation. In general, ice clouds interfere with the radiation balance of planet Earth effectively at high altitudes. Since ambient matter of biological origin tends to have rather large aerodynamic diameters, it exhibits a fast sinking velocity and can only reach limited altitudes. Therefore, research focused on materials found in higher quantities in the upper atmosphere. However, recent findings indicate that the role of biological INPs has been underestimated in the past. In 2012 Pummer and colleagues found that the INPs from birch pollen can be washed off and constitute of macromolecules in the size-range of a few nanometres. With such a small diameter, they show a much longer life span in the upper atmosphere than expected. Further, Huffman and colleagues showed in 2013 a burst of biological INPs over woodlands triggered by rain events, which matches the finding of Pummer et al. well. Plants originating from the northern timberline experience harsh conditions with night frost even during the warm seasons. To prevent frost damages, those plants developed coping mechanisms. Many plant species, which are domestic in cold weather zones, exhibit ice nucleation activity. Therefore, it is important to examine those plants to understand the scale at which biological INPs can be emitted. For the presented results we focus on two types of samples: Berries and tree pollen. Both belong to plants domestic at the northern timberline. With our results we are able to show that INPs are spread vastly throughout different species. Furthermore, all those INPs show certain similarities to each other, most importantly, all of the found INPs seem to be associated to macromolecules in the nano-particulate size range. We examined the INPs from birch pollen more closely. Results indicate that proteins play a major role. Pummer, B., Bauer, H., Bernardi, J., Bleicher, S

  3. Production of functional probiotic, prebiotic, and synbiotic ice creams.

    PubMed

    Di Criscio, T; Fratianni, A; Mignogna, R; Cinquanta, L; Coppola, R; Sorrentino, E; Panfili, G

    2010-10-01

    In this work, 3 types of ice cream were produced: a probiotic ice cream produced by adding potentially probiotic microorganisms such as Lactobacillus casei and Lactobacillus rhamnosus; a prebiotic ice cream produced by adding inulin, a prebiotic substrate; and a synbiotic ice cream produced by adding probiotic microorganisms and inulin in combination. In addition to microbial counts, pH, acidity, and physical and functional properties of the ice creams were evaluated. The experimental ice creams preserved the probiotic bacteria and had counts of viable lactic acid bacteria after frozen storage that met the minimum required to achieve probiotic effects. Moreover, most of the ice creams showed good nutritional and sensory properties, with the best results obtained with Lb. casei and 2.5% inulin.

  4. Principles and biotechnological applications of bacterial ice nucleation.

    PubMed

    Margaritis, A; Bassi, A S

    1991-01-01

    Certain aerobic, Gram-negative bacteria, including the epiphytic plant pathogen, Pseudomonas syringae, possess a membrane protein that enables them to nucleate crystallization in supercooled water. Currently, these ice-nucleating (IN) bacteria are being used in snow making and have potential applications in the production and texturing of frozen foods, and as a replacement of silver iodide in cloud seeding. A negative aspect of these IN bacteria is frost damage to plant surfaces. Thus, of the various types of biological ice nucleators, bacteria have been the subject of most research and also appear relevant to the anticipated practical uses. The intent of this review is to explain the identification and ecology of the ice-nucleating bacteria, as well as to discuss aspects of molecular biology related to ice nucleation and consider existing and potential applications of this unique phenomenon.

  5. Operation IceBridge: Sea Ice Interlude

    NASA Image and Video Library

    Sea ice comes in an array of shapes and sizes and has its own ephemeral beauty. Operation IceBridge studies sea ice at both poles, and also runs across interesting formations en route to other targ...

  6. Ice Waves

    NASA Image and Video Library

    2017-09-27

    Ice Waves - May 21st, 2001 Description: Along the southeastern coast of Greenland, an intricate network of fjords funnels glacial ice to the Atlantic Ocean. During the summer melting season, newly calved icebergs join slabs of sea ice and older, weathered bergs in an offshore slurry that the southward-flowing East Greenland Current sometimes swirls into stunning shapes. Exposed rock of mountain peaks, tinted red in this image, hints at a hidden landscape. Credit: USGS/NASA/Landsat 7 To learn more about the Landsat satellite go to: landsat.gsfc.nasa.gov/ NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

  7. Breakup of Pack Ice, Antarctic Ice Shelf

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Breakup of Pack Ice along the periphery of the Antarctic Ice Shelf (53.5S, 3.0E) produced this mosaic of ice floes off the Antarctic Ice Shelf. Strong offshore winds, probably associated with strong katabatic downdrafts from the interior of the continent, are seen peeling off the edges of the ice shelf into long filamets of sea ice, icebergs, bergy bits and growlers to flow northward into the South Atlantic Ocean. 53.5S, 3.0E

  8. Ecology of southern ocean pack ice.

    PubMed

    Brierley, Andrew S; Thomas, David N

    2002-01-01

    Around Antarctica the annual five-fold growth and decay of sea ice is the most prominent physical process and has a profound impact on marine life there. In winter the pack ice canopy extends to cover almost 20 million square kilometres--some 8% of the southern hemisphere and an area larger than the Antarctic continent itself (13.2 million square kilometres)--and is one of the largest, most dynamic ecosystems on earth. Biological activity is associated with all physical components of the sea-ice system: the sea-ice surface; the internal sea-ice matrix and brine channel system; the underside of sea ice and the waters in the vicinity of sea ice that are modified by the presence of sea ice. Microbial and microalgal communities proliferate on and within sea ice and are grazed by a wide range of proto- and macrozooplankton that inhabit the sea ice in large concentrations. Grazing organisms also exploit biogenic material released from the sea ice at ice break-up or melt. Although rates of primary production in the underlying water column are often low because of shading by sea-ice cover, sea ice itself forms a substratum that provides standing stocks of bacteria, algae and grazers significantly higher than those in ice-free areas. Decay of sea ice in summer releases particulate and dissolved organic matter to the water column, playing a major role in biogeochemical cycling as well as seeding water column phytoplankton blooms. Numerous zooplankton species graze sea-ice algae, benefiting additionally because the overlying sea-ice ceiling provides a refuge from surface predators. Sea ice is an important nursery habitat for Antarctic krill, the pivotal species in the Southern Ocean marine ecosystem. Some deep-water fish migrate to shallow depths beneath sea ice to exploit the elevated concentrations of some zooplankton there. The increased secondary production associated with pack ice and the sea-ice edge is exploited by many higher predators, with seals, seabirds and whales

  9. Microbial ice nucleators scavenged from the atmosphere during simulated rain events

    NASA Astrophysics Data System (ADS)

    Hanlon, Regina; Powers, Craig; Failor, Kevin; Monteil, Caroline L.; Vinatzer, Boris A.; Schmale, David G.

    2017-08-01

    Rain and snow collected at ground level have been found to contain biological ice nucleators. These ice nucleators have been proposed to have originated in clouds, where they may have participated in the formation of precipitation via ice phase nucleation. We conducted a series of field experiments to test the hypothesis that at least some of the microbial ice nucleators (prokaryotes and eukaryotes) present in rain may not originate in clouds but instead be scavenged from the lower atmosphere by rainfall. Thirty-three simulated rain events were conducted over four months off the side of the Smart Road Bridge in Blacksburg, VA, USA. In each event, sterile water was dispensed over the side of the bridge and recovered in sterile containers in an open fallow agricultural field below (a distance of ∼55 m). Microbes scavenged from the simulated rain events were cultured and their ice nucleation activity was examined. Putative microbial ice nucleators were cultured from 94% (31/33) of the simulated rain events, and represented 1.5% (121/8331) of the total colonies assayed. Putative ice nucleators were subjected to additional droplet freezing assays, and those confirmed through these repeated assays represented 0.4% (34/8331) of the total. Mean CFUs scavenged by simulated rain ranged from 2 to 267 CFUs/mL. Scavenged ice nucleators belong to a number of taxa including the bacterial genera Pseudomonas, Pantoea, and Xanthomonas, and the fungal genera Fusarium, Humicola, and Mortierella. An ice-nucleating strain of the fungal genus Penicillium was also recovered from a volumetric air sampler at the study site. This work expands our knowledge of the scavenging properties of rainfall, and suggests that at least some ice nucleators in natural precipitation events may have been scrubbed from the atmosphere during rainfall, and thus are not likely to be involved in precipitation.

  10. Ice Nucleation properties of Air-Plane Soot Surrogates Using Vibrational Micro-spectroscopy: a preliminary study

    NASA Astrophysics Data System (ADS)

    Pirim, Claire; Ikhenazene, Raouf; Ortega, Ismael; Carpentier, Yvain; Focsa, Cristian; Chazallon, Bertrand

    2015-04-01

    Aircraft emissions have been studied extensively since the late 1960s and the interest was mainly driven by their direct and indirect effects on climate and the generation of contrails [1-4]. Emissions of solid-state particles (soots) from engine exhausts due to incomplete fuel combustion are considered to influence ice and liquid water cloud droplet activation [4]. The activity of these aerosols would originate from their ability to be important centers of ice-particle nucleation by promoting ice formation above water homogeneous freezing point. While some experiments focused on ice nucleation on soot particles did not yet reach definitive conclusions, soot are reported to be generally worse ice nuclei than mineral dust, nucleating at higher ice-supersaturations for deposition nucleation and at lower temperatures for immersion freezing. However, there are still numerous opened questions on the ice nucleation properties of soot particles [5], most likely due to the lack of information on the abundance, on the physico-chemical properties (structure and chemical compositions) of these aerosols, competition between different ice nucleation modes and dynamical factors that affect ice nucleation. Furthermore, the soot emitted from aircraft may be associated with soluble components like sulphate that can act as heterogeneous ice nuclei and initiate freezing at supersaturation of only 120-130% [6]. Therefore, more detailed studies of aerosol nucleation activity combined with throughout structural and compositional analyzes are needed in order to establish any association between the particles' hygroscopicity and their physico-chemical properties. In the present preliminary work, nucleation activity of air-plane soot particle surrogates is monitored using a temperature-controlled reactor in which the sample's relative humidity is precisely measured with a cryo-hygrometer. Formation of water/ice onto the particles is followed both optically and spectroscopically, using a

  11. Microbial mercury methylation in Antarctic sea ice.

    PubMed

    Gionfriddo, Caitlin M; Tate, Michael T; Wick, Ryan R; Schultz, Mark B; Zemla, Adam; Thelen, Michael P; Schofield, Robyn; Krabbenhoft, David P; Holt, Kathryn E; Moreau, John W

    2016-08-01

    Atmospheric deposition of mercury onto sea ice and circumpolar sea water provides mercury for microbial methylation, and contributes to the bioaccumulation of the potent neurotoxin methylmercury in the marine food web. Little is known about the abiotic and biotic controls on microbial mercury methylation in polar marine systems. However, mercury methylation is known to occur alongside photochemical and microbial mercury reduction and subsequent volatilization. Here, we combine mercury speciation measurements of total and methylated mercury with metagenomic analysis of whole-community microbial DNA from Antarctic snow, brine, sea ice and sea water to elucidate potential microbially mediated mercury methylation and volatilization pathways in polar marine environments. Our results identify the marine microaerophilic bacterium Nitrospina as a potential mercury methylator within sea ice. Anaerobic bacteria known to methylate mercury were notably absent from sea-ice metagenomes. We propose that Antarctic sea ice can harbour a microbial source of methylmercury in the Southern Ocean.

  12. 7 CFR 58.648 - Microbiological requirements for ice cream.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Service 1 Requirements for Finished Products Bearing Usda Official Identification § 58.648 Microbiological requirements for ice cream. The finished product shall contain not more than 50,000 bacteria per gram...

  13. 7 CFR 58.648 - Microbiological requirements for ice cream.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Service 1 Requirements for Finished Products Bearing Usda Official Identification § 58.648 Microbiological requirements for ice cream. The finished product shall contain not more than 50,000 bacteria per gram...

  14. 7 CFR 58.648 - Microbiological requirements for ice cream.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Service 1 Requirements for Finished Products Bearing Usda Official Identification § 58.648 Microbiological requirements for ice cream. The finished product shall contain not more than 50,000 bacteria per gram...

  15. 7 CFR 58.648 - Microbiological requirements for ice cream.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Service 1 Requirements for Finished Products Bearing Usda Official Identification § 58.648 Microbiological requirements for ice cream. The finished product shall contain not more than 50,000 bacteria per gram...

  16. Biofilm formation in an ice cream plant.

    PubMed

    Gunduz, Gulten Tiryaki; Tuncel, Gunnur

    2006-01-01

    The sites of biofilm formation in an ice cream plant were investigated by sampling both the production line and the environment. Experiments were carried out twice within a 20-day period. First, stainless steel coupons were fixed to surfaces adjacent to food contact surfaces, the floor drains and the doormat. They were taken for the analysis of biofilm at three different production stages. Then, biofilm forming bacteria were enumerated and also presence of Listeria monocytogenes was monitored. Biofilm forming isolates were selected on the basis of colony morphology and Gram's reaction; Gram negative cocci and rod, Gram positive cocci and spore forming isolates were identified. Most of the biofilm formations were seen on the conveyor belt of a packaging machine 8 h after the beginning of the production, 6.5 x 10(3) cfu cm(-2). Most of the Gram negative bacteria identified belong to Enterobacteriaceae family such as Proteus, Enterobacter, Citrobacter, Shigella, Escherichia, Edwardsiella. The other Gram negative microflora included Aeromonas, Plesiomonas, Moraxella, Pseudomonas or Alcaligenes spp. were also isolated. Gram positive microflora of the ice cream plant included Staphyloccus, Bacillus, Listeria and lactic acid bacteria such as Streptococcus, Leuconostoc or Pediococcus spp. The results from this study highlighted the problems of spread of pathogens like Listeria and Shigella and spoilage bacteria. In the development of cleaning and disinfection procedures in ice cream plants, an awareness of these biofilm-forming bacteria is essential for the ice cream plants.

  17. Physiological and ecological significance of biological ice nucleators.

    PubMed

    Lundheim, Rolv

    2002-07-29

    When a pure water sample is cooled it can remain in the liquid state at temperatures well below its melting point (0 degrees C). The initiation of the transition from the liquid state to ice is called nucleation. Substances that facilitate this transition so that it takes place at a relatively high sub-zero temperature are called ice nucleators. Many living organisms produce ice nucleators. In some cases, plausible reasons for their production have been suggested. In bacteria, they could induce frost damage to their hosts, giving the bacteria access to nutrients. In freeze-tolerant animals, it has been suggested that ice nucleators help to control the ice formation so that it is tolerable to the animal. Such ice nucleators can be called adaptive ice nucleators. There are, however, also examples of ice nucleators in living organisms where the adaptive value is difficult to understand. These ice nucleators might be structures with functions other than facilitating ice formation. These structures might be called incidental ice nucleators.

  18. A habitat for psychrophiles in deep Antarctic ice

    PubMed Central

    Price, P. Buford

    2000-01-01

    Microbes, some of which may be viable, have been found in ice cores drilled at Vostok Station at depths down to ≈3,600 m, close to the surface of the huge subglacial Lake Vostok. Two types of ice have been found. The upper 3,500 m comprises glacial ice containing traces of nutrients of aeolian origin including sulfuric acid, nitric acid, methanosulfonic acid (MSA), formic acid, sea salts, and mineral grains. Ice below ≈3,500 m comprises refrozen water from Lake Vostok, accreted to the bottom of the glacial ice. Nutrients in the accretion ice include salts and dissolved organic carbon. There is great interest in searching for living microbes and especially for new species in deepest Antarctic ice. I propose a habitat consisting of interconnected liquid veins along three-grain boundaries in ice in which psychrophilic bacteria can move and obtain energy and carbon from ions in solution. In the accretion ice, with an age of a few 104 years and a temperature a few degrees below freezing, the carbon and energy sources in the veins can maintain significant numbers of cells per cubic centimeter that are metabolizing but not multiplying. In the 4 × 105-year-old colder glacial ice, at least 1 cell per cm3 in acid veins can be maintained. With fluorescence microscopy tuned to detect NADH in live organisms, motile bacteria could be detected by direct scanning of the veins in ice samples. PMID:10655516

  19. The microscopic features of heterogeneous ice nucleation may affect the macroscopic morphology of atmospheric ice crystals.

    PubMed

    Cox, Stephen J; Raza, Zamaan; Kathmann, Shawn M; Slater, Ben; Michaelides, Angelos

    2013-01-01

    It is surprisingly difficult to freeze water. Almost all ice that forms under "mild" conditions (temperatures > -40 degrees C) requires the presence of a nucleating agent--a solid particle that facilitates the freezing process--such as clay mineral dust, soot or bacteria. In a computer simulation, the presence of such ice nucleating agents does not necessarily alleviate the difficulties associated with forming ice on accessible timescales. Nevertheless, in this work we present results from molecular dynamics simulations in which we systematically compare homogeneous and heterogeneous ice nucleation, using the atmospherically important clay mineral kaolinite as our model ice nucleating agent. From our simulations, we do indeed find that kaolinite is an excellent ice nucleating agent but that contrary to conventional thought, non-basal faces of ice can nucleate at the basal face of kaolinite. We see that in the liquid phase, the kaolinite surface has a drastic effect on the density profile of water, with water forming a dense, tightly bound first contact layer. Monitoring the time evolution of the water density reveals that changes away from the interface may play an important role in the nucleation mechanism. The findings from this work suggest that heterogeneous ice nucleating agents may not only enhance the ice nucleation rate, but also alter the macroscopic structure of the ice crystals that form.

  20. 7 CFR 58.648 - Microbiological requirements for ice cream.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Microbiological requirements for ice cream. 58.648 Section 58.648 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING... requirements for ice cream. The finished product shall contain not more than 50,000 bacteria per gram...

  1. A marine biogenic source of atmospherically relevant ice nucleating particles

    NASA Astrophysics Data System (ADS)

    Wilson, Theodore W.; Ladino, Luis A.; Alpert, Peter A.; Chance, Rosie; Whale, Thomas F.; Vergara Temprado, Jesús; Burrows, Susannah M.; Breckels, Mark N.; Kilthau, Wendy P.; Browse, Jo; Bertram, Allan K.; Miller, Lisa A.; Carpenter, Lucy J.; Hamilton, Jacqui F.; Carslaw, Kenneth S.; Brooks, Ian M.; Abbatt, Jonathan P. D.; Aller, Josephine Y.; Knopf, Daniel A.; Murray, Benjamin J.

    2016-04-01

    There are limited observations describing marine sources of ice nucleating particles (INPs), despite sea spray aerosol being one of the dominant sources of atmospheric particles globally. Evidence indicates that some marine aerosol particles act as INPs, but the source of these particles is unclear. The sea surface microlayer is enriched in surface active organic material representative of that found in sub-micron sea-spray aerosol. We show that the sea surface microlayer is enriched in INPs that nucleate ice under conditions pertinent to both high-altitude ice clouds and low to mid-altitude mixed-phase clouds. The INPs pass through 0.2 μm pore filters, are heat sensitive and spectroscopic analysis indicates the presence of material consistent with phytoplankton exudates. Mass spectrometric analysis of solid phase extracted dissolved organic material from microlayer and sub-surface water samples showed that the relative abundance of certain ions correlated with microlayer ice nucleation activity. However, these ions were not themselves directly responsible for ice nucleation. We propose that material associated with phytoplankton exudates is a candidate for the observed activity of the microlayer samples. We show that laboratory produced exudate from a ubiquitous marine diatom contains INPs despite its separation from diatom cells. Finally we use a parameterisation of our field data to estimate the atmospheric INP contribution from primary marine organic emissions using a global model and test the model against existing INP measurements in the remote oceans. We find that biogenic marine INPs can be dominant in remote marine environments, such as the Southern Ocean.

  2. Determination of suspendable ice nuclei from various pollen species

    NASA Astrophysics Data System (ADS)

    Felgitsch, Laura; Pummer, Bernhard; Grothe, Hinrich

    2014-05-01

    Heterogeneous ice nucleation is an important process in cloud glaciation. On the one hand, ice clouds increase the albedo (Mishchenko et al. 1996), leading to a cooling effect, and on the other hand tend to a faster precipitation (Lohmann 2002) and therefore reduce the total cloud albedo, which has a direct influence on the climate and weather. However, many processes involved are still not entirely understood and only poorly described which makes it difficult to forecast these effects for climate modelling. Therefore detailed laboratory studies are inherently necessary. Only recently, Pummer et al. (2012) have shown that pollen emitted from trees originating from the Northern timberline carry active ice nuclei, which are suspendable macromolecules. So far little is known about the structures and functionalities of these molecules. Here we present several analytical strategies we use to separate the responsible species (via solid phase extraction with different columns like C18 and PH) and solve the structure including different forms of mass spectrometry (MS) like the intact cell MS and matrix assisted laser desorption/ionization (MALDI) MS, which give access to the molecules in question. For identification, the surface molecules are compared with those washed out from pores and from pollen that burst due to osmotic pressure. Lohmann U.; 'A Glaciation Indirect Aerosol Effect Caused by Soot Aerosols; J. Geoph. Res.; Vol. 24 No.4; pp 11-1 - 11-4; 2002 Mishchenko M.I., Rossow W.B., Macke A., Lacis A. A.; Sensitivity of Cirrus Cloud Albedo, Bidirectional Reflectance and Optical Thickness Retrieval Accuracy to Ice Particle Shape, J. Geoph. Res.; Vol. 101, No D12; pp. 16,973 - 16,985; 1996 Pummer B., Bauer H., Bernardi J., Bleicher S., Grothe H.; Suspendable Macromolecules are Responsible for Ice Nucleation Activity of Birch and Conifer Pollen; Atmos. Chem. Phys.; 12; pp. 2541 - 2550;

  3. Laboratory studies of immersion and deposition mode ice nucleation of ozone aged mineral dust particles

    NASA Astrophysics Data System (ADS)

    Kanji, Z. A.; Welti, A.; Chou, C.; Stetzer, O.; Lohmann, U.

    2013-09-01

    Ice nucleation in the atmosphere is central to the understanding the microphysical properties of mixed-phase and cirrus clouds. Ambient conditions such as temperature (T) and relative humidity (RH), as well as aerosol properties such as chemical composition and mixing state play an important role in predicting ice formation in the troposphere. Previous field studies have reported the absence of sulfate and organic compounds on mineral dust ice crystal residuals sampled at mountain top stations or aircraft based measurements despite the long-range transport mineral dust is subjected to. We present laboratory studies of ice nucleation for immersion and deposition mode on ozone aged mineral dust particles for 233 < T < 263 K. Heterogeneous ice nucleation of untreated kaolinite (Ka) and Arizona Test Dust (ATD) particles is compared to corresponding aged particles that are subjected to ozone concentrations of 0.4-4.3 ppmv in a stainless steel aerosol tank. The portable ice nucleation counter (PINC) and immersion chamber combined with the Zurich ice nucleation chamber (IMCA-ZINC) are used to conduct deposition and immersion mode measurements, respectively. Ice active fractions as well as ice active surface site densities (ns) are reported and observed to increase as a function of decreasing temperature. We present first results that demonstrate enhancement of the ice nucleation ability of aged mineral dust particles in both the deposition and immersion mode due to ageing. We also present the first results to show a suppression of heterogeneous ice nucleation activity without the condensation of a coating of (in)organic material. In immersion mode, low ozone exposed Ka particles showed enhanced ice activity requiring a median freezing temperature of 1.5 K warmer than that of untreated Ka, whereas high ozone exposed ATD particles showed suppressed ice nucleation requiring a median freezing temperature of 3 K colder than that of untreated ATD. In deposition mode, low

  4. Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

    NASA Astrophysics Data System (ADS)

    Beydoun, Hassan; Polen, Michael; Sullivan, Ryan C.

    2016-10-01

    Heterogeneous ice nucleation remains one of the outstanding problems in cloud physics and atmospheric science. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established parameterization of immersion freezing properties. Here, we formulate an ice active, surface-site-based stochastic model of heterogeneous freezing with the unique feature of invoking a continuum assumption on the ice nucleating activity (contact angle) of an aerosol particle's surface that requires no assumptions about the size or number of active sites. The result is a particle-specific property g that defines a distribution of local ice nucleation rates. Upon integration, this yields a full freezing probability function for an ice nucleating particle. Current cold plate droplet freezing measurements provide a valuable and inexpensive resource for studying the freezing properties of many atmospheric aerosol systems. We apply our g framework to explain the observed dependence of the freezing temperature of droplets in a cold plate on the concentration of the particle species investigated. Normalizing to the total particle mass or surface area present to derive the commonly used ice nuclei active surface (INAS) density (ns) often cannot account for the effects of particle concentration, yet concentration is typically varied to span a wider measurable freezing temperature range. A method based on determining what is denoted an ice nucleating species' specific critical surface area is presented and explains the concentration dependence as a result of increasing the variability in ice nucleating active sites between droplets. By applying this method to experimental droplet freezing data from four different systems, we demonstrate its ability to interpret immersion freezing temperature spectra of droplets containing variable particle concentrations. It is shown that general

  5. Marine sources of ice nucleating particles: results from phytoplankton cultures and samples collected at sea

    NASA Astrophysics Data System (ADS)

    Wilbourn, E.; Thornton, D.; Brooks, S. D.; Graff, J.

    2016-12-01

    The role of marine aerosols as ice nucleating particles is currently poorly understood. Despite growing interest, there are remarkably few ice nucleation measurements on representative marine samples. Here we present results of heterogeneous ice nucleation from laboratory studies and in-situ air and sea water samples collected during NAAMES (North Atlantic Aerosol and Marine Ecosystems Study). Thalassiosira weissflogii (CCMP 1051) was grown under controlled conditions in batch cultures and the ice nucleating activity depended on the growth phase of the cultures. Immersion freezing temperatures of the lab-grown diatoms were determined daily using a custom ice nucleation apparatus cooled at a set rate. Our results show that the age of the culture had a significant impact on ice nucleation temperature, with samples in stationary phase causing nucleation at -19.9 °C, approximately nine degrees warmer than the freezing temperature during exponential growth phase. Field samples gathered during the NAAMES II cruise in May 2016 were also tested for ice nucleating ability. Two types of samples were gathered. Firstly, whole cells were fractionated by size from surface seawater using a BD Biosciences Influx Cell Sorter (BD BS ISD). Secondly, aerosols were generated using the SeaSweep and subsequently size-selected using a PIXE Cascade Impactor. Samples were tested for the presence of ice nucleating particles (INP) using the technique described above. There were significant differences in the freezing temperature of the different samples; of the three sample types the lab-grown cultures tested during stationary phase froze at the warmest temperatures, followed by the SeaSweep samples (-25.6 °C) and the size-fractionated cell samples (-31.3 °C). Differences in ice nucleation ability may be due to size differences between the INP, differences in chemical composition of the sample, or some combination of these two factors. Results will be presented and atmospheric implications

  6. Microbial ice nucleators are scavenged from the atmosphere during artificial rain events

    NASA Astrophysics Data System (ADS)

    Hanlon, Regina; Powers, Craig; Failor, Kevin; Vinatzer, Boris; Schmale, David

    2016-04-01

    Some microorganisms associated with rain may catalyze the nucleation of ice crystals at significantly warmer temperatures than would normally be required for ice formation, suggesting that they may play an important role in the onset of precipitation. Rain samples collected near the surface of the earth contain an array of microbial ice nucleators, but the little is known about their source(s) and life history. We conducted a series of field experiments to test the hypothesis that microbial ice nucleators are scavenged from the atmosphere by rainfall. Thirty three artificial rain events were conducted over four months (Nov 2014, Dec 2014, April 2015, and June 2015) off the side of the Smart Road Bridge in Blacksburg, VA, USA. In each event, sterile water was dispensed over the side of the bridge and recovered in sterile containers following gravitational settling from the bridge to an open fallow agricultural field below (a distance of ~55m). Microbes scavenged from the artificial rain events were cultured on six different types of agar media (R2A, TSA, CA; +/-cycloheximide), and the ice nucleation activity was examined for colonies cultured from the different media types. Mean CFUs scavenged by artificial rain ranged from 2 to 267 CFUs/mL. Microbial ice nucleators were cultured from 94% (31/33) of the simulated rain events, and represented 1.4% (121/8871) of the total number of colonies assayed. This percentage is similar to the percentage of culturable microbial ice nucleators occurring in about half of the natural rain events studied in Blacksburg, VA. Sequence-assisted identification of the repeatable microbial ice nucleators that were scavenged from the atmosphere showed a number of unique prokaryotic and eukaryotic taxa. This work expands our knowledge of the scavenging properties of rainfall, and suggests that at least some ice nucleators in natural precipitation events may have been scrubbed from the atmosphere during rainfall, and thus are not likely to be

  7. Major new sources of biological ice nuclei

    NASA Astrophysics Data System (ADS)

    Moffett, B. F.; Hill, T.; Henderson-Begg, S. K.

    2009-12-01

    Almost all research on biological ice nucleation has focussed on a limited number of bacteria. Here we characterise several major new sources of biogenic ice nuclei. These include mosses, hornworts, liverworts and cyanobacteria. Ice nucleation in the eukaryotic bryophytes appears to be ubiquitous. The temperature at which these organisms nucleate is that at which the difference in vapour pressure over ice and water is at or close to its maximum. At these temperatures (-8 to -18 degrees C) ice will grow at the expense of supercooled water. These organisms are dependent for their water on occult precipitation - fog, dew and cloudwater which by its nature is not collected in conventional rain gauges. Therefore we suggest that these organism produce ice nuclei as a water harvesting mechanism. Since the same mechanism would also drive the Bergeron-Findeisen process, and as moss is known to become airborne, these nuclei may have a role in the initiation of precipitation. The properties of these ice nuclei are very different from the well characterised bacterial nuclei. We will also present DNA sequence data showing that, although related, the proteins responsible are only very distantly related to the classical bacterial ice nuclei.

  8. Magnetic Bacteria.

    ERIC Educational Resources Information Center

    Nelson, Jane Bray; Nelson, Jim

    1992-01-01

    Describes the history of Richard Blakemore's discovery of magnetotaxic organisms. Discusses possible reasons why the magnetic response in bacteria developed. Proposes research experiments integrating biology and physics in which students investigate problems using cultures of magnetotaxic organisms. (MDH)

  9. Meth (Crank, Ice) Facts

    MedlinePlus

    ... Crank, Ice) Facts Meth (Crank, Ice) Facts Listen Methamphetamine—meth for short—is a white, bitter powder. ... names for meth are: Crank Ice Crystal Glass Chalk PDF File: EasyToRead_MethFacts_012017.pdf In This ...

  10. Disappearing Ice

    NASA Technical Reports Server (NTRS)

    2008-01-01

    These images were acquired by NASA's Phoenix Mars Lander's Surface Stereo Imager on the 21st and 25th days of the mission, or Sols 20 and 24 (June 15 and 18, 2008).

    These images show sublimation of ice in the trench informally called 'Dodo-Goldilocks' over the course of four days.

    In the lower left corner, lumps disappear, similar to the process of evaporation.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  11. Disappearing Ice

    NASA Technical Reports Server (NTRS)

    2008-01-01

    These images were acquired by NASA's Phoenix Mars Lander's Surface Stereo Imager on the 21st and 25th days of the mission, or Sols 20 and 24 (June 15 and 18, 2008).

    These images show sublimation of ice in the trench informally called 'Dodo-Goldilocks' over the course of four days.

    In the lower left corner, lumps disappear, similar to the process of evaporation.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  12. Microbiota within the perennial ice cover of Lake Vida, Antarctica.

    PubMed

    Mosier, Annika C; Murray, Alison E; Fritsen, Christian H

    2007-02-01

    Lake Vida, located in the McMurdo Dry Valleys, Antarctica, is an 'ice-sealed' lake with approximately 19 m of ice covering a highly saline water column (approximately 245 ppt). The lower portions of the ice cover and the lake beneath have been isolated from the atmosphere and land for circa 2800 years. Analysis of microbial assemblages within the perennial ice cover of the lake revealed a diverse array of bacteria and eukarya. Bacterial and eukaryal denaturing gradient gel electrophoresis phylotype profile similarities were low (<59%) between all of the depths compared (five depths spanning 11 m of the ice cover), with the greatest differences occurring between surface and deep ice. The majority of bacterial 16S rRNA gene sequences in the surface ice were related to Actinobacteria (42%) while Gammaproteobacteria (52%) dominated the deep ice community. Comparisons of assemblage composition suggest differences in ice habitability and organismal origin in the upper and lower portions of ice cover. Specifically, the upper ice cover microbiota likely reflect the modern day transport and colonization of biota from the terrestrial landscape, whereas assemblages in the deeper ice are more likely to be persistent remnant biota that originated from the ancient liquid water column of the lake that froze.

  13. Sea-ice software: ICEMAN

    NASA Technical Reports Server (NTRS)

    Lee, Meemong

    1988-01-01

    An oceanographer's work bench which provides tools for ice data display, ice type classification, global and local ice motion analysis, and data enhancing is presented. The user interface; ice texture analysis; and ice motion analysis are described.

  14. Ice Front at Venable Ice Shelf

    NASA Image and Video Library

    2013-06-13

    This photo, taken onboard the Chilean Navy P3 aircraft, shows the ice front of Venable Ice Shelf, West Antarctica, in October 2008. It is an example of a small-size ice shelf that is a large melt water producer.

  15. Ice Crystal Icing Research at NASA

    NASA Technical Reports Server (NTRS)

    Flegel, Ashlie B.

    2017-01-01

    Ice crystals found at high altitude near convective clouds are known to cause jet engine power-loss events. These events occur due to ice crystals entering a propulsion systems core flowpath and accreting ice resulting in events such as uncommanded loss of thrust (rollback), engine stall, surge, and damage due to ice shedding. As part of a community with a growing need to understand the underlying physics of ice crystal icing, NASA has been performing experimental efforts aimed at providing datasets that can be used to generate models to predict the ice accretion inside current and future engine designs. Fundamental icing physics studies on particle impacts, accretion on a single airfoil, and ice accretions observed during a rollback event inside a full-scale engine in the Propulsion Systems Laboratory are summarized. Low fidelity code development using the results from the engine tests which identify key parameters for ice accretion risk and the development of high fidelity codes are described. These activities have been conducted internal to NASA and through collaboration efforts with industry, academia, and other government agencies. The details of the research activities and progress made to date in addressing ice crystal icing research challenges are discussed.

  16. Microbiological quality of packaged ice from various sources in Georgia.

    PubMed

    Mako, Stephanie L; Harrison, Mark A; Sharma, Vijendra; Kong, Fanbin

    2014-09-01

    This study determined the microbiological and chemical quality of ice produced and bagged on premises in retail establishments and in free-standing self-service ice vending machines in the state of Georgia and compared the results with that from ice produced by manufacturing companies monitored by the International Packaged Ice Association. Two hundred fifty bags of packaged ice samples were obtained from retail locations and self-service ice vending machines, along with 25 bags of packaged manufactured ice. Ice samples were melted within 24 h of collection and heterotrophic plate count SimPlates were used to detect heterotrophic bacteria present. Colisure and Enterolert assays were used to enumerate coliforms, nonpathogenic Escherichia coli, and enterococci. Membrane filtration coupled with enrichment was used to detect Salmonella and Listeria monocytogenes. Confirmation tests were done for presumptive-positive pathogens. None of the manufactured ice had unacceptable microbial levels. Six percent of the ice samples bagged at retail sites and from ice vending machines contained unsatisfactory levels of heterotrophs compared with the limits set by the International Packaged Ice Association (≥ 500 most probable number [MPN]/100 ml). Thirty-seven percent of these samples contained an unsatisfactory level of coliforms (≥ 1.0 MPN/100 ml), 1% contained nonpathogenic E. coli, and 13% contained enterococci (≥ 1.0 MPN/100 ml). One sample tested positive for the presence of Salmonella and another tested positive for Enterobacter agglomerans. Ninety-five samples of packaged ice from retail establishments and vending machines (38%) had pH levels outside the acceptable range that can affect product flavor. Turbidity of three samples exceeded the acceptable level. No samples had unacceptable nitrate levels. Manufactured ice had better microbiological and chemical quality than ice packaged on the premises of retail locations and from self-serve ice vending machines.

  17. Methanotrophic bacteria.

    PubMed Central

    Hanson, R S; Hanson, T E

    1996-01-01

    Methane-utilizing bacteria (methanotrophs) are a diverse group of gram-negative bacteria that are related to other members of the Proteobacteria. These bacteria are classified into three groups based on the pathways used for assimilation of formaldehyde, the major source of cell carbon, and other physiological and morphological features. The type I and type X methanotrophs are found within the gamma subdivision of the Proteobacteria and employ the ribulose monophosphate pathway for formaldehyde assimilation, whereas type II methanotrophs, which employ the serine pathway for formaldehyde assimilation, form a coherent cluster within the beta subdivision of the Proteobacteria. Methanotrophic bacteria are ubiquitous. The growth of type II bacteria appears to be favored in environments that contain relatively high levels of methane, low levels of dissolved oxygen, and limiting concentrations of combined nitrogen and/or copper. Type I methanotrophs appear to be dominant in environments in which methane is limiting and combined nitrogen and copper levels are relatively high. These bacteria serve as biofilters for the oxidation of methane produced in anaerobic environments, and when oxygen is present in soils, atmospheric methane is oxidized. Their activities in nature are greatly influenced by agricultural practices and other human activities. Recent evidence indicates that naturally occurring, uncultured methanotrophs represent new genera. Methanotrophs that are capable of oxidizing methane at atmospheric levels exhibit methane oxidation kinetics different from those of methanotrophs available in pure cultures. A limited number of methanotrophs have the genetic capacity to synthesize a soluble methane monooxygenase which catalyzes the rapid oxidation of environmental pollutants including trichloroethylene. PMID:8801441

  18. Scrambled Ice

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This complex area on the side of Europa which faces away from Jupiter shows several types of features which are formed by disruptions of Europa's icy crust. North is to the top of the image, taken by NASA's Galileo spacecraft, and the Sun illuminates the surface from the left. The prominent wide, dark bands are up to 20 kilometers (12 miles) wide and over 50 kilometers (30 miles) long. They are believed to have formed when Europa's icy crust fractured, separated and filled in with darker, 'dirtier' ice or slush from below. A relatively rare type of feature on Europa is the 15-kilometer-diameter (9.3-mile) impact crater in the lower left corner. The small number of impact craters on Europa's surface is an indication of its relatively young age. A region of chaotic terrain south of this impact crater contains crustal plates which have broken apart and rafted into new positions. Some of these 'ice rafts' are nearly 1 kilometer (about half a mile) across. Other regions of chaotic terrain are visible and indicate heating and disruption of Europa's icy crust from below. The youngest features in this scene are the long, narrow cracks in the ice which cut across all other features. One of these cracks is about 30 kilometers (18 miles) to the right of the impact crater and extends for hundreds of miles from the top to the bottom of the image.

    The image, centered near 23 degrees south latitude and 179 degrees longitude, covers an area about 240 by 215 kilometers (150 by 130 miles) across. The finest details that can be discerned in this picture are about 460 meters (500 yards) across. The image was taken as Galileo flew by Europa on March 29, 1998. The image was taken by the onboard solid state imaging system camera from an altitude of 23,000 kilometers (14,000 miles).

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech

  19. Scrambled Ice

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This complex area on the side of Europa which faces away from Jupiter shows several types of features which are formed by disruptions of Europa's icy crust. North is to the top of the image, taken by NASA's Galileo spacecraft, and the Sun illuminates the surface from the left. The prominent wide, dark bands are up to 20 kilometers (12 miles) wide and over 50 kilometers (30 miles) long. They are believed to have formed when Europa's icy crust fractured, separated and filled in with darker, 'dirtier' ice or slush from below. A relatively rare type of feature on Europa is the 15-kilometer-diameter (9.3-mile) impact crater in the lower left corner. The small number of impact craters on Europa's surface is an indication of its relatively young age. A region of chaotic terrain south of this impact crater contains crustal plates which have broken apart and rafted into new positions. Some of these 'ice rafts' are nearly 1 kilometer (about half a mile) across. Other regions of chaotic terrain are visible and indicate heating and disruption of Europa's icy crust from below. The youngest features in this scene are the long, narrow cracks in the ice which cut across all other features. One of these cracks is about 30 kilometers (18 miles) to the right of the impact crater and extends for hundreds of miles from the top to the bottom of the image.

    The image, centered near 23 degrees south latitude and 179 degrees longitude, covers an area about 240 by 215 kilometers (150 by 130 miles) across. The finest details that can be discerned in this picture are about 460 meters (500 yards) across. The image was taken as Galileo flew by Europa on March 29, 1998. The image was taken by the onboard solid state imaging system camera from an altitude of 23,000 kilometers (14,000 miles).

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech

  20. A comparison between ice and salt storages on bacteriological quality of Asian seabass (Lates calcarifer).

    PubMed

    Rahman, M M; Nasrun, M; Hossain, M Y; Aa'zamuddin, M

    2012-06-15

    The study compares the bacteriological quality on Asian seabass (Lates calcarifer) between ice and salt storage methods. The main objectives of the study were to identify different bacteria constituents and quantitative bacterial load in Asian seabass when preserved with ice and sea salt. For the purpose of this study, Asian seabass was stored in two different conditions of ice-chilled and salted for 2 days. All fish samples were analyzed by performing bacteriological analysis and the isolated bacteria were identified by using API identification system. In case of the quantity of bacteria in the flesh, Chilling and salting had no significant difference to the quantity of bacteria on fish flesh. As for the skin, salt-preserved fish showed higher quantity of bacteria than ice-preserved fish. Acinetobacter baumannii and Pseudomonas fluorescens had been identified from skin sample of ice-chilled fish. Besides P. fluorescens and A. baumannii other isolates identified include Vibrio and Myxobacteria. All bacteria were cocci-shaped except a few bacilli. In term of bacteria number and morphological characteristics, ice-chilled preserved fish was better than salt preserved fish. Overall, less number of bacteria was observed in both ice-chilled and sea salt preserved fish. The result of this study indicated that the quick preservation is a very important factor to control bacterial load in the preserved fish.

  1. Persistence of bacterial and archaeal communities in sea ice through an Arctic winter

    PubMed Central

    Collins, R Eric; Rocap, Gabrielle; Deming, Jody W

    2010-01-01

    The structure of bacterial communities in first-year spring and summer sea ice differs from that in source seawaters, suggesting selection during ice formation in autumn or taxon-specific mortality in the ice during winter. We tested these hypotheses by weekly sampling (January–March 2004) of first-year winter sea ice (Franklin Bay, Western Arctic) that experienced temperatures from −9°C to −26°C, generating community fingerprints and clone libraries for Bacteria and Archaea. Despite severe conditions and significant decreases in microbial abundance, no significant changes in richness or community structure were detected in the ice. Communities of Bacteria and Archaea in the ice, as in under-ice seawater, were dominated by SAR11 clade Alphaproteobacteria and Marine Group I Crenarchaeota, neither of which is known from later season sea ice. The bacterial ice library contained clones of Gammaproteobacteria from oligotrophic seawater clades (e.g. OM60, OM182) but no clones from gammaproteobacterial genera commonly detected in later season sea ice by similar methods (e.g. Colwellia, Psychrobacter). The only common sea ice bacterial genus detected in winter ice was Polaribacter. Overall, selection during ice formation and mortality during winter appear to play minor roles in the process of microbial succession that leads to distinctive spring and summer sea ice communities. PMID:20192970

  2. Persistence of bacterial and archaeal communities in sea ice through an Arctic winter.

    PubMed

    Collins, R Eric; Rocap, Gabrielle; Deming, Jody W

    2010-07-01

    The structure of bacterial communities in first-year spring and summer sea ice differs from that in source seawaters, suggesting selection during ice formation in autumn or taxon-specific mortality in the ice during winter. We tested these hypotheses by weekly sampling (January-March 2004) of first-year winter sea ice (Franklin Bay, Western Arctic) that experienced temperatures from -9 degrees C to -26 degrees C, generating community fingerprints and clone libraries for Bacteria and Archaea. Despite severe conditions and significant decreases in microbial abundance, no significant changes in richness or community structure were detected in the ice. Communities of Bacteria and Archaea in the ice, as in under-ice seawater, were dominated by SAR11 clade Alphaproteobacteria and Marine Group I Crenarchaeota, neither of which is known from later season sea ice. The bacterial ice library contained clones of Gammaproteobacteria from oligotrophic seawater clades (e.g. OM60, OM182) but no clones from gammaproteobacterial genera commonly detected in later season sea ice by similar methods (e.g. Colwellia, Psychrobacter). The only common sea ice bacterial genus detected in winter ice was Polaribacter. Overall, selection during ice formation and mortality during winter appear to play minor roles in the process of microbial succession that leads to distinctive spring and summer sea ice communities.

  3. Bacterial Microbiota Associated with the Glacier Ice Worm Is Dominated by Both Worm-Specific and Glacier-Derived Facultative Lineages.

    PubMed

    Murakami, Takumi; Segawa, Takahiro; Dial, Roman; Takeuchi, Nozomu; Kohshima, Shiro; Hongoh, Yuichi

    2017-03-31

    The community structure of bacteria associated with the glacier ice worm Mesenchytraeus solifugus was analyzed by amplicon sequencing of 16S rRNA genes and their transcripts. Ice worms were collected from two distinct glaciers in Alaska, Harding Icefield and Byron Glacier, and glacier surfaces were also sampled for comparison. Marked differences were observed in bacterial community structures between the ice worm and glacier surface samples. Several bacterial phylotypes were detected almost exclusively in the ice worms, and these bacteria were phylogenetically affiliated with either animal-associated lineages or, interestingly, clades mostly consisting of glacier-indigenous species. The former included bacteria that belong to Mollicutes, Chlamydiae, Rickettsiales, and Lachnospiraceae, while the latter included Arcicella and Herminiimonas phylotypes. Among these bacteria enriched in ice worm samples, Mollicutes, Arcicella, and Herminiimonas phylotypes were abundantly and consistently detected in the ice worm samples; these phylotypes constituted the core microbiota associated with the ice worm. A fluorescence in situ hybridization analysis showed that Arcicella cells specifically colonized the epidermis of the ice worms. Other bacterial phylotypes detected in the ice worm samples were also abundantly recovered from the respective habitat glaciers; these bacteria may be food for ice worms to digest or temporary residents. Nevertheless, some were overrepresented in the ice worm RNA samples; they may also function as facultative gut bacteria. Our results indicate that the community structure of bacteria associated with ice worms is distinct from that in the associated glacier and includes worm-specific and facultative, glacier-indigenous lineages.

  4. Bacterial Microbiota Associated with the Glacier Ice Worm Is Dominated by Both Worm-Specific and Glacier-Derived Facultative Lineages

    PubMed Central

    Murakami, Takumi; Segawa, Takahiro; Dial, Roman; Takeuchi, Nozomu; Kohshima, Shiro; Hongoh, Yuichi

    2017-01-01

    The community structure of bacteria associated with the glacier ice worm Mesenchytraeus solifugus was analyzed by amplicon sequencing of 16S rRNA genes and their transcripts. Ice worms were collected from two distinct glaciers in Alaska, Harding Icefield and Byron Glacier, and glacier surfaces were also sampled for comparison. Marked differences were observed in bacterial community structures between the ice worm and glacier surface samples. Several bacterial phylotypes were detected almost exclusively in the ice worms, and these bacteria were phylogenetically affiliated with either animal-associated lineages or, interestingly, clades mostly consisting of glacier-indigenous species. The former included bacteria that belong to Mollicutes, Chlamydiae, Rickettsiales, and Lachnospiraceae, while the latter included Arcicella and Herminiimonas phylotypes. Among these bacteria enriched in ice worm samples, Mollicutes, Arcicella, and Herminiimonas phylotypes were abundantly and consistently detected in the ice worm samples; these phylotypes constituted the core microbiota associated with the ice worm. A fluorescence in situ hybridization analysis showed that Arcicella cells specifically colonized the epidermis of the ice worms. Other bacterial phylotypes detected in the ice worm samples were also abundantly recovered from the respective habitat glaciers; these bacteria may be food for ice worms to digest or temporary residents. Nevertheless, some were overrepresented in the ice worm RNA samples; they may also function as facultative gut bacteria. Our results indicate that the community structure of bacteria associated with ice worms is distinct from that in the associated glacier and includes worm-specific and facultative, glacier-indigenous lineages. PMID:28302989

  5. Geographic, seasonal, and precipitation chemistry influence on the abundance and activity of biological ice nucleators in rain and snow

    PubMed Central

    Christner, Brent C.; Cai, Rongman; Morris, Cindy E.; McCarter, Kevin S.; Foreman, Christine M.; Skidmore, Mark L.; Montross, Scott N.; Sands, David C.

    2008-01-01

    Biological ice nucleators (IN) function as catalysts for freezing at relatively warm temperatures (warmer than −10 °C). We examined the concentration (per volume of liquid) and nature of IN in precipitation collected from Montana and Louisiana, the Alps and Pyrenees (France), Ross Island (Antarctica), and Yukon (Canada). The temperature of detectable ice-nucleating activity for more than half of the samples was ≥ −5 °C based on immersion freezing testing. Digestion of the samples with lysozyme (i.e., to hydrolyze bacterial cell walls) led to reductions in the frequency of freezing (0–100%); heat treatment greatly reduced (95% average) or completely eliminated ice nucleation at the measured conditions in every sample. These behaviors were consistent with the activity being bacterial and/or proteinaceous in origin. Statistical analysis revealed seasonal similarities between warm-temperature ice-nucleating activities in snow samples collected over 7 months in Montana. Multiple regression was used to construct models with biogeochemical data [major ions, total organic carbon (TOC), particle, and cell concentration] that were accurate in predicting the concentration of microbial cells and biological IN in precipitation based on the concentration of TOC, Ca2+, and NH4+, or TOC, cells, Ca2+, NH4+, K+, PO43−, SO42−, Cl−, and HCO3−. Our results indicate that biological IN are ubiquitous in precipitation and that for some geographic locations the activity and concentration of these particles is related to the season and precipitation chemistry. Thus, our research suggests that biological IN are widespread in the atmosphere and may affect meteorological processes that lead to precipitation. PMID:19028877

  6. Ice sheet margins and ice shelves

    NASA Technical Reports Server (NTRS)

    Thomas, R. H.

    1984-01-01

    The effect of climate warming on the size of ice sheet margins in polar regions is considered. Particular attention is given to the possibility of a rapid response to warming on the order of tens to hundreds of years. It is found that the early response of the polar regions to climate warming would be an increase in the area of summer melt on the ice sheets and ice shelves. For sufficiently large warming (5-10C) the delayed effects would include the breakup of the ice shelves by an increase in ice drainage rates, particularly from the ice sheets. On the basis of published data for periodic changes in the thickness and melting rates of the marine ice sheets and fjord glaciers in Greenland and Antarctica, it is shown that the rate of retreat (or advance) of an ice sheet is primarily determined by: bedrock topography; the basal conditions of the grounded ice sheet; and the ice shelf condition downstream of the grounding line. A program of satellite and ground measurements to monitor the state of ice sheet equilibrium is recommended.

  7. Brash Ice Behavior.

    DTIC Science & Technology

    1981-05-01

    34 cannonball " brash ice should not be confused is slush ice or mush ice. Slush is defined as accumulation of snow in water, but either of these terms...that " cannonball ice" consists of perfect spheres, but rather that the pieces are relatively spherical, their three dimensions being comparable

  8. Modern Airfoil Ice Accretions

    NASA Technical Reports Server (NTRS)

    Addy, Harold E., Jr.; Potapczuk, Mark G.; Sheldon, David W.

    1997-01-01

    This report presents results from the first icing tests performed in the Modem Airfoils program. Two airfoils have been subjected to icing tests in the NASA Lewis Icing Research Tunnel (IRT). Both airfoils were two dimensional airfoils; one was representative of a commercial transport airfoil while the other was representative of a business jet airfoil. The icing test conditions were selected from the FAR Appendix C envelopes. Effects on aerodynamic performance are presented including the effects of varying amounts of glaze ice as well as the effects of approximately the same amounts of glaze, mixed, and rime ice. Actual ice shapes obtained in these tests are also presented for these cases. In addition, comparisons are shown between ice shapes from the tests and ice shapes predicted by the computer code, LEWICE for similar conditions. Significant results from the tests are that relatively small amounts of ice can have nearly as much effect on airfoil lift coefficient as much greater amounts of ice and that glaze ice usually has a more detrimental effect than either rime or mixed ice. LEWICE predictions of ice shapes, in general, compared reasonably well with ice shapes obtained in the IRT, although differences in details of the ice shapes were observed.

  9. Icing: Accretion, Detection, Protection

    NASA Technical Reports Server (NTRS)

    Reinmann, John J.

    1994-01-01

    The global aircraft industry and its regulatory agencies are currently involved in three major icing efforts: ground icing; advanced technologies for in-flight icing; and tailplane icing. These three major icing topics correspondingly support the three major segments of any aircraft flight profile: takeoff; cruise and hold; and approach and land. This lecture addressess these three topics in the same sequence as they appear in flight, starting with ground deicing, followed by advanced technologies for in-flight ice protection, and ending with tailplane icing.

  10. Wilkins Ice Shelf

    NASA Image and Video Library

    2009-04-20

    The Wilkins Ice Shelf, as seen by NASA Terra spacecraft, on the western side of the Antarctic Peninsula, experienced multiple disintegration events in 2008. By the beginning of 2009, a narrow ice bridge was all that remained to connect the ice shelf to ice fragments fringing nearby Charcot Island. That bridge gave way in early April 2009. Days after the ice bridge rupture, on April 12, 2009, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite acquired this image of the southern base of the ice bridge, where it connected with the remnant ice shelf. Although the ice bridge has played a role in stabilizing the ice fragments in the region, its rupture doesn't guarantee the ice will immediately move away. http://photojournal.jpl.nasa.gov/catalog/PIA11991

  11. The competition between mineral dust and soot ice nuclei in mixed-phase clouds (Invited)

    NASA Astrophysics Data System (ADS)

    Murray, B. J.; Atkinson, J.; Umo, N.; Browse, J.; Woodhouse, M. T.; Whale, T.; Baustian, K. J.; Carslaw, K. S.; Dobbie, S.; O'Sullivan, D.; Malkin, T. L.

    2013-12-01

    The amount of ice present in mixed-phase clouds, which contain both supercooled liquid water droplets and ice particles, affects cloud extent, lifetime, particle size and radiative properties. The freezing of cloud droplets can be catalysed by the presence of aerosol particles known as ice nuclei. In this talk our recent laboratory and global aerosol modelling work on mineral dust and soot ice nuclei will be presented. We have performed immersion mode experiments to quantify ice nucleation by the individual minerals which make up desert mineral dusts and have shown that the feldspar component, rather than the clay component, is most important for ice nucleation (Atkinson et al. 2013). Experiments with well-characterised soot generated with eugenol, an intermediate in biomass burning, and n-decane show soot has a significant ice nucleation activity in mixed-phase cloud conditions. Our results for soot are in good agreement with previous results for acetylene soot (DeMott, 1990), but extend the efficiency to much higher temperatures. We then use a global aerosol model (GLOMAP) to map the distribution of soot and feldspar particles on a global basis. We show that below about -15oC that dust and soot together can explain most observed ice nuclei in the Earth's atmosphere, while at warmer temperatures other ice nuclei types are needed. We show that in some regions soot is the most important ice nuclei (below -15oC), while in others feldspar dust dominates. Our results suggest that there is a strong anthropogenic contribution to the ice nuclei population, since a large proportion of soot aerosol in the atmosphere results from human activities. Atkinson, J. D., Murray, B. J., Woodhouse, M. T., Carslaw, K. S., Whale, T. F., Baustian, K. J., Dobbie, S., O'Sullivan, D., and Malkin, T. L.: The importance of feldspar for ice nucleation by mineral dust in mixed-phase clouds, Nature, 10.1038/nature12278, (2013). Demott, P. J. 1990. An Exploratory-Study of Ice Nucleation by Soot

  12. Biological aerosol particles as a key determinant of ice nuclei populations in a forest ecosystem

    NASA Astrophysics Data System (ADS)

    Tobo, Yutaka; Prenni, Anthony J.; DeMott, Paul J.; Huffman, J. Alex; McCluskey, Christina S.; Tian, Guoxun; Pöhlker, Christopher; Pöschl, Ulrich; Kreidenweis, Sonia M.

    2013-09-01

    primary biological aerosol particles (PBAPs) are known to have very high ice nucleating ability under mixed-phase cloud conditions. However, since the abundances of ice nucleation active PBAPs in the atmosphere are generally thought to be extremely small, their importance has remained uncertain. Here we present evidence for the role of PBAPs as atmospheric ice nuclei (IN) active at temperatures ranging from about -34°C to -9°C in a midlatitude ponderosa pine forest ecosystem in summertime. Our measurements show that the number concentrations of IN active at these temperatures were positively correlated with number concentrations of ambient fluorescent biological aerosol particles (FBAPs). Notably, the number concentrations of IN active at warmer temperatures increased quite rapidly in response to increases in the number concentrations of FBAPs. Moreover, we show that a newly-proposed parameterization related to the number concentrations of FBAPs can better reproduce the number concentrations of IN active over the entire temperature range examined, as compared with parameterizations related solely to the number concentrations of total aerosol particles with diameters larger than 0.5 µm as proposed previously. These results suggest that certain PBAPs released from forest biota can indeed play a key role in determining atmospheric IN populations in this ecosystem, especially at warmer temperatures, potentially leading to ice initiation in nearby mixed-phase clouds.

  13. Frazil Ice Dynamics,

    DTIC Science & Technology

    1984-04-01

    necessary nd Identify by block number) Crystal growth Ice prevention Crystallization Mathematical analysis Frazil ice Ice *O Ice formation 120. ABSTRACT... growth - and nucleation of new crystals are the major parameters in these equations. Expressions tor the growth rate ot frazil ice N. V, crystals are...described. The growth rate along the major axis is controlled by heat transfer. The heat transfer coefficient * O is a function of crystal size, the fluid

  14. Antarctic Sea Ice-a Habitat for Extremophiles

    NASA Astrophysics Data System (ADS)

    Thomas, D. N.; Dieckmann, G. S.

    2002-01-01

    The pack ice of Earth's polar oceans appears to be frozen white desert, devoid of life. However, beneath the snow lies a unique habitat for a group of bacteria and microscopic plants and animals that are encased in an ice matrix at low temperatures and light levels, with the only liquid being pockets of concentrated brines. Survival in these conditions requires a complex suite of physiological and metabolic adaptations, but sea-ice organisms thrive in the ice, and their prolific growth ensures they play a fundamental role in polar ecosystems. Apart from their ecological importance, the bacterial and algae species found in sea ice have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on ice-covered extraterrestrial bodies.

  15. Antarctic Sea ice--a habitat for extremophiles.

    PubMed

    Thomas, D N; Dieckmann, G S

    2002-01-25

    The pack ice of Earth's polar oceans appears to be frozen white desert, devoid of life. However, beneath the snow lies a unique habitat for a group of bacteria and microscopic plants and animals that are encased in an ice matrix at low temperatures and light levels, with the only liquid being pockets of concentrated brines. Survival in these conditions requires a complex suite of physiological and metabolic adaptations, but sea-ice organisms thrive in the ice, and their prolific growth ensures they play a fundamental role in polar ecosystems. Apart from their ecological importance, the bacterial and algae species found in sea ice have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on ice-covered extraterrestrial bodies.

  16. Scavenging of ice-nucleating microorganisms from the atmosphere by artificial rain events

    NASA Astrophysics Data System (ADS)

    Hanlon, Regina; Powers, Craig; Failor, Kevin; Vinatzer, Boris; Schmale, David

    2015-04-01

    Little is known about how microorganisms are scavenged from the atmosphere during rainfall. Microorganisms are abundant and diverse in rain (precipitation) collected near the surface of the earth. Some of these rain-associated microorganisms produce proteins that catalyze the nucleation of ice crystals at significantly warmer temperatures than would normally be required for ice formation, suggesting that they may play important roles in weather, including the onset of precipitation. We conducted a series of field experiments to test the hypothesis that ice-nucleating microorganisms are scavenged from the atmosphere by rainfall. Thirteen artificial rain events were conducted off the side of the Smart Road Bridge in Blacksburg, VA, USA. In each event, sterile water was dispensed over the side of the bridge (simulated rainfall), and recovered in sterile containers following gravitational settling from the side of the bridge to an open fallow agricultural field below (a distance of ~55m from the release site to the collection site). Microbes scavenged from the artificial rain events were cultured on six different types of agar media (R2A, TSA, CA; +/- cycloheximide) and the ice nucleation activity was examined for colonies cultured from the different media types. Mean CFUs scavenged by artificial rain ranged from 83 to 196 CFUs/mL across all six media types. Ice-nucleating microorganisms were recovered from 85% (11/13) of the simulated rain events, and represented about 1% of the total number of colonies assayed from each event. Strikingly, this percentage is nearly identical to the percentage of culturable ice-nucleating microorganisms occurring in about half of the natural rain events studied to date in Blacksburg, Virginia. This work expands our knowledge of the scavenging properties of rain, and suggests that at least some ice nucleators in natural precipitation events may have been stripped from the atmosphere during rainfall, thus negating their potential role in

  17. Bacteria Counter

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Science Applications, Inc.'s ATP Photometer makes a rapid and accurate count of the bacteria in a body fluid sample. Instrument provides information on the presence and quantity of bacteria by measuring the amount of light emitted by the reaction between two substances. Substances are ATP adenosine triphosphate and luciferase. The reactants are applied to a human body sample and the ATP Photometer observes the intensity of the light emitted displaying its findings in a numerical output. Total time lapse is usually less than 10 minutes, which represents a significant time savings in comparison of other techniques. Other applications are measuring organisms in fresh and ocean waters, determining bacterial contamination of foodstuffs, biological process control in the beverage industry, and in assay of activated sewage sludge.

  18. Ice Clouds

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Heavy water ice clouds almost completely obscure the surface in Vastitas Borealis.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude 69.5, Longitude 283.6 East (76.4 West). 19 meter/pixel resolution.

  19. Arctic ice islands

    SciTech Connect

    Sackinger, W.M.; Jeffries, M.O.; Lu, M.C.; Li, F.C.

    1988-01-01

    The development of offshore oil and gas resources in the Arctic waters of Alaska requires offshore structures which successfully resist the lateral forces due to moving, drifting ice. Ice islands are floating, a tabular icebergs, up to 60 meters thick, of solid ice throughout their thickness. The ice islands are thus regarded as the strongest ice features in the Arctic; fixed offshore structures which can directly withstand the impact of ice islands are possible but in some locations may be so expensive as to make oilfield development uneconomic. The resolution of the ice island problem requires two research steps: (1) calculation of the probability of interaction between an ice island and an offshore structure in a given region; and (2) if the probability if sufficiently large, then the study of possible interactions between ice island and structure, to discover mitigative measures to deal with the moving ice island. The ice island research conducted during the 1983-1988 interval, which is summarized in this report, was concerned with the first step. Monte Carlo simulations of ice island generation and movement suggest that ice island lifetimes range from 0 to 70 years, and that 85% of the lifetimes are less then 35 years. The simulation shows a mean value of 18 ice islands present at any time in the Arctic Ocean, with a 90% probability of less than 30 ice islands. At this time, approximately 34 ice islands are known, from observations, to exist in the Arctic Ocean, not including the 10-meter thick class of ice islands. Return interval plots from the simulation show that coastal zones of the Beaufort and Chukchi Seas, already leased for oil development, have ice island recurrences of 10 to 100 years. This implies that the ice island hazard must be considered thoroughly, and appropriate safety measures adopted, when offshore oil production plans are formulated for the Alaskan Arctic offshore. 132 refs., 161 figs., 17 tabs.

  20. Not all feldspars are equal: a survey of ice nucleating properties across the feldspar group of minerals

    NASA Astrophysics Data System (ADS)

    Harrison, Alexander D.; Whale, Thomas F.; Carpenter, Michael A.; Holden, Mark A.; Neve, Lesley; O'Sullivan, Daniel; Vergara Temprado, Jesus; Murray, Benjamin J.

    2016-09-01

    Mineral dust particles from wind-blown soils are known to act as effective ice nucleating particles in the atmosphere and are thought to play an important role in the glaciation of mixed phase clouds. Recent work suggests that feldspars are the most efficient nucleators of the minerals commonly present in atmospheric mineral dust. However, the feldspar group of minerals is complex, encompassing a range of chemical compositions and crystal structures. To further investigate the ice-nucleating properties of the feldspar group we measured the ice nucleation activities of 15 characterized feldspar samples. We show that alkali feldspars, in particular the potassium feldspars, generally nucleate ice more efficiently than feldspars in the plagioclase series which contain significant amounts of calcium. We also find that there is variability in ice nucleating ability within these groups. While five out of six potassium-rich feldspars have a similar ice nucleating ability, one potassium rich feldspar sample and one sodium-rich feldspar sample were significantly more active. The hyper-active Na-feldspar was found to lose activity with time suspended in water with a decrease in mean freezing temperature of about 16 °C over 16 months; the mean freezing temperature of the hyper-active K-feldspar decreased by 2 °C over 16 months, whereas the "standard" K-feldspar did not change activity within the uncertainty of the experiment. These results, in combination with a review of the available literature data, are consistent with the previous findings that potassium feldspars are important components of arid or fertile soil dusts for ice nucleation. However, we also show that there is the possibility that some alkali feldspars may have enhanced ice nucleating abilities, which could have implications for prediction of ice nucleating particle concentrations in the atmosphere.

  1. Stochastic ice stream dynamics

    PubMed Central

    Bertagni, Matteo Bernard; Ridolfi, Luca

    2016-01-01

    Ice streams are narrow corridors of fast-flowing ice that constitute the arterial drainage network of ice sheets. Therefore, changes in ice stream flow are key to understanding paleoclimate, sea level changes, and rapid disintegration of ice sheets during deglaciation. The dynamics of ice flow are tightly coupled to the climate system through atmospheric temperature and snow recharge, which are known exhibit stochastic variability. Here we focus on the interplay between stochastic climate forcing and ice stream temporal dynamics. Our work demonstrates that realistic climate fluctuations are able to (i) induce the coexistence of dynamic behaviors that would be incompatible in a purely deterministic system and (ii) drive ice stream flow away from the regime expected in a steady climate. We conclude that environmental noise appears to be crucial to interpreting the past behavior of ice sheets, as well as to predicting their future evolution. PMID:27457960

  2. Stochastic ice stream dynamics.

    PubMed

    Mantelli, Elisa; Bertagni, Matteo Bernard; Ridolfi, Luca

    2016-08-09

    Ice streams are narrow corridors of fast-flowing ice that constitute the arterial drainage network of ice sheets. Therefore, changes in ice stream flow are key to understanding paleoclimate, sea level changes, and rapid disintegration of ice sheets during deglaciation. The dynamics of ice flow are tightly coupled to the climate system through atmospheric temperature and snow recharge, which are known exhibit stochastic variability. Here we focus on the interplay between stochastic climate forcing and ice stream temporal dynamics. Our work demonstrates that realistic climate fluctuations are able to (i) induce the coexistence of dynamic behaviors that would be incompatible in a purely deterministic system and (ii) drive ice stream flow away from the regime expected in a steady climate. We conclude that environmental noise appears to be crucial to interpreting the past behavior of ice sheets, as well as to predicting their future evolution.

  3. Stochastic ice stream dynamics

    NASA Astrophysics Data System (ADS)

    Mantelli, Elisa; Bertagni, Matteo Bernard; Ridolfi, Luca

    2016-08-01

    Ice streams are narrow corridors of fast-flowing ice that constitute the arterial drainage network of ice sheets. Therefore, changes in ice stream flow are key to understanding paleoclimate, sea level changes, and rapid disintegration of ice sheets during deglaciation. The dynamics of ice flow are tightly coupled to the climate system through atmospheric temperature and snow recharge, which are known exhibit stochastic variability. Here we focus on the interplay between stochastic climate forcing and ice stream temporal dynamics. Our work demonstrates that realistic climate fluctuations are able to (i) induce the coexistence of dynamic behaviors that would be incompatible in a purely deterministic system and (ii) drive ice stream flow away from the regime expected in a steady climate. We conclude that environmental noise appears to be crucial to interpreting the past behavior of ice sheets, as well as to predicting their future evolution.

  4. Iced-airfoil aerodynamics

    NASA Astrophysics Data System (ADS)

    Bragg, M. B.; Broeren, A. P.; Blumenthal, L. A.

    2005-07-01

    Past research on airfoil aerodynamics in icing are reviewed. This review emphasizes the time period after the 1978 NASA Lewis workshop that initiated the modern icing research program at NASA and the current period after the 1994 ATR accident where aerodynamics research has been more aircraft safety focused. Research pre-1978 is also briefly reviewed. Following this review, our current knowledge of iced airfoil aerodynamics is presented from a flowfield-physics perspective. This article identifies four classes of ice accretions: roughness, horn ice, streamwise ice, and spanwise-ridge ice. For each class, the key flowfield features such as flowfield separation and reattachment are discussed and how these contribute to the known aerodynamic effects of these ice shapes. Finally Reynolds number and Mach number effects on iced-airfoil aerodynamics are summarized.

  5. Top Sounder Ice Penetration

    NASA Astrophysics Data System (ADS)

    Porter, D. L.; Goemmer, S. A.; Sweeney, J. H.

    2014-12-01

    Ice draft measurements are made as part of normal operations for all US Navy submarines operating in the Arctic Ocean. The submarine ice draft data are unique in providing high resolution measurements over long transects of the ice covered ocean. The data has been used to document a multidecadal drop in ice thickness, and for validating and improving numerical sea-ice models. A submarine upward-looking sonar draft measurement is made by a sonar transducer mounted in the sail or deck of the submarine. An acoustic beam is transmitted upward through the water column, reflecting off the bottom of the sea ice and returning to the transducer. Ice thickness is estimated as the difference between the ship's depth (measured by pressure) and the acoustic range to the bottom of the ice estimated from the travel time of the sonar pulse. Digital recording systems can provide the return off the water-ice interface as well as returns that have penetrated the ice. Typically, only the first return from the ice hull is analyzed. Information regarding ice flow interstitial layers provides ice age information and may possibly be derived with the entire return signal. The approach being investigated is similar to that used in measuring bottom sediment layers and will involve measuring the echo level from the first interface, solving the reflection loss from that transmission, and employing reflection loss versus impedance mismatch to ascertain ice structure information.

  6. Breakup of Pack Ice, Antarctic Ice Shelf

    NASA Image and Video Library

    1991-09-18

    STS048-152-007 (12-18 Sept 1991) --- The periphery of the Antarctic ice shelf and the Antarctic Peninsula were photographed by the STS 48 crew members. Strong offshore winds, probably associated with katabatic winds from the interior of the continent, are peeling off the edges of the ice shelf into ribbons of sea ice, icebergs, bergy bits and growlers into the cold waters of the circum-Antarctic southern ocean.

  7. Ross Ice Shelf, Antarctic Ice and Clouds

    NASA Technical Reports Server (NTRS)

    1991-01-01

    In this view of Antarctic ice and clouds, (56.5S, 152.0W), the Ross Ice Shelf of Antarctica is almost totally clear, showing stress cracks in the ice surface caused by wind and tidal drift. Clouds on the eastern edge of the picture are associated with an Antarctic cyclone. Winds stirred up these storms have been known to reach hurricane force.

  8. Influence of Aerosol Chemical Composition on Heterogeneous Ice Formation under Mid-Upper Troposphere Conditions

    NASA Astrophysics Data System (ADS)

    Kanji, Z. A.; Niemand, M.; Saathoff, H.; Möhler, O.; Chou, C.; Abbatt, J.; Stetzer, O.

    2011-12-01

    T and lowest RH required for ice formation. The particles investigated were classified into three categories, mineral dust aerosols, hygroscopic and non-hygroscopic particles which included organic and inorganic salts and/or coatings. In addition results ice formation results from ozone aged mineral particles will be presented. It is observed that changing functional groups on the surface of the particles can inhibit ice formation in the deposition mode. The ice forming efficiency of mineral aerosols was observed to be the highest, requiring RH with respect to ice as low as 105% at 233 K. Hydrophobic particles were comparatively weaker at forming ice and required RH close to or above water saturation for ice formation via deposition/condensation mode freezing. The high ice nucleation activity of mineral aerosols suggest that they could play an important role in ice forming and therefore precipitation processes in the troposphere and may have in impact on global and regional climate.

  9. Acclimation of Antarctic Chlamydomonas to the sea-ice environment: a transcriptomic analysis.

    PubMed

    Liu, Chenlin; Wang, Xiuliang; Wang, Xingna; Sun, Chengjun

    2016-07-01

    The Antarctic green alga Chlamydomonas sp. ICE-L was isolated from sea ice. As a psychrophilic microalga, it can tolerate the environmental stress in the sea-ice brine, such as freezing temperature and high salinity. We performed a transcriptome analysis to identify freezing stress responding genes and explore the extreme environmental acclimation-related strategies. Here, we show that many genes in ICE-L transcriptome that encoding PUFA synthesis enzymes, molecular chaperon proteins, and cell membrane transport proteins have high similarity to the gens from Antarctic bacteria. These ICE-L genes are supposed to be acquired through horizontal gene transfer from its symbiotic microbes in the sea-ice brine. The presence of these genes in both sea-ice microalgae and bacteria indicated the biological processes they involved in are possibly contributing to ICE-L success in sea ice. In addition, the biological pathways were compared between ICE-L and its closely related sister species, Chlamydomonas reinhardtii and Volvox carteri. In ICE-L transcripome, many sequences homologous to the plant or bacteria proteins in the post-transcriptional, post-translational modification, and signal-transduction KEGG pathways, are absent in the nonpsychrophilic green algae. These complex structural components might imply enhanced stress adaptation capacity. At last, differential gene expression analysis at the transcriptome level of ICE-L indicated that genes that associated with post-translational modification, lipid metabolism, and nitrogen metabolism are responding to the freezing treatment. In conclusion, the transcriptome of Chlamydomonas sp. ICE-L is very useful for exploring the mutualistic interaction between microalgae and bacteria in sea ice; and discovering the specific genes and metabolism pathways responding to the freezing acclimation in psychrophilic microalgae.

  10. An active bacterial community linked to high chl-a concentrations in Antarctic winter-pack ice and evidence for the development of an anaerobic sea-ice bacterial community.

    PubMed

    Eronen-Rasimus, Eeva; Luhtanen, Anne-Mari; Rintala, Janne-Markus; Delille, Bruno; Dieckmann, Gerhard; Karkman, Antti; Tison, Jean-Louis

    2017-10-01

    Antarctic sea-ice bacterial community composition and dynamics in various developmental stages were investigated during the austral winter in 2013. Thick snow cover likely insulated the ice, leading to high (<4 μg l(-1)) chlorophyll-a (chl-a) concentrations and consequent bacterial production. Typical sea-ice bacterial genera, for example, Octadecabacter, Polaribacter and Glaciecola, often abundant in spring and summer during the sea-ice algal bloom, predominated in the communities. The variability in bacterial community composition in the different ice types was mainly explained by the chl-a concentrations, suggesting that as in spring and summer sea ice, the sea-ice bacteria and algae may also be coupled during the Antarctic winter. Coupling between the bacterial community and sea-ice algae was further supported by significant correlations between bacterial abundance and production with chl-a. In addition, sulphate-reducing bacteria (for example, Desulforhopalus) together with odour of H2S were observed in thick, apparently anoxic ice, suggesting that the development of the anaerobic bacterial community may occur in sea ice under suitable conditions. In all, the results show that bacterial community in Antarctic sea ice can stay active throughout the winter period and thus possible future warming of sea ice and consequent increase in bacterial production may lead to changes in bacteria-mediated processes in the Antarctic sea-ice zone.

  11. Comparative ICE genomics: insights into the evolution of the SXT/R391 family of ICEs.

    PubMed

    Wozniak, Rachel A F; Fouts, Derrick E; Spagnoletti, Matteo; Colombo, Mauro M; Ceccarelli, Daniela; Garriss, Geneviève; Déry, Christine; Burrus, Vincent; Waldor, Matthew K

    2009-12-01

    Integrating and conjugative elements (ICEs) are one of the three principal types of self-transmissible mobile genetic elements in bacteria. ICEs, like plasmids, transfer via conjugation; but unlike plasmids and similar to many phages, these elements integrate into and replicate along with the host chromosome. Members of the SXT/R391 family of ICEs have been isolated from several species of gram-negative bacteria, including Vibrio cholerae, the cause of cholera, where they have been important vectors for disseminating genes conferring resistance to antibiotics. Here we developed a plasmid-based system to capture and isolate SXT/R391 ICEs for sequencing. Comparative analyses of the genomes of 13 SXT/R391 ICEs derived from diverse hosts and locations revealed that they contain 52 perfectly syntenic and nearly identical core genes that serve as a scaffold capable of mobilizing an array of variable DNA. Furthermore, selection pressure to maintain ICE mobility appears to have restricted insertions of variable DNA into intergenic sites that do not interrupt core functions. The variable genes confer diverse element-specific phenotypes, such as resistance to antibiotics. Functional analysis of a set of deletion mutants revealed that less than half of the conserved core genes are required for ICE mobility; the functions of most of the dispensable core genes are unknown. Several lines of evidence suggest that there has been extensive recombination between SXT/R391 ICEs, resulting in re-assortment of their respective variable gene content. Furthermore, our analyses suggest that there may be a network of phylogenetic relationships among sequences found in all types of mobile genetic elements.

  12. Genetic diversity of the causative agent of ice-ice disease of the seaweed Kappaphycus alvarezii from Karimunjawa island, Indonesia

    NASA Astrophysics Data System (ADS)

    Syafitri, E.; Prayitno, S. B.; Ma'ruf, W. F.; Radjasa, O. K.

    2017-02-01

    An essential step in investigating the bacterial role in the occurrence of diseases in Kappaphycus alvarezii is the characterization of bacteria associated with this seaweed. A molecular characterization was conducted on the genetic diversity of the causative agents of ice-ice disease associated with K. alvarezii widely known as the main source of kappa carrageenan. K. alvrezii infected with ice-ice were collected from the Karimunjawa island, North Java Sea, Indonesia. Using Zobell 2216E marine agar medium, nine bacterial species were isolated from the infected seaweed. The molecular characterizations revealed that the isolated bacteria causing ice-ice disease were closely related to the genera of Alteromonas, Bacillus, Pseudomonas, Pseudoalteromonas, Glaciecola, Aurantimonas, and Rhodococcus. In order to identify the symptoms causative organisms, the isolated bacterial species were cultured and were evaluated for their pathogenity. Out of 9 species, only 3 isolates were able to cause the ice-ice symptoms and consisted of Alteromonas macleodii, Pseudoalteromonas issachenkonii and Aurantimonas coralicida. A. macleodii showed the highest pathogenity.

  13. Ice nucleation, shape, and composition of aerosol particles in one of the most polluted cities in the world: Ulaanbaatar, Mongolia

    NASA Astrophysics Data System (ADS)

    Hasenkopf, Christa A.; Veghte, Daniel P.; Schill, Gregory P.; Lodoysamba, Sereeter; Freedman, Miriam Arak; Tolbert, Margaret A.

    2016-08-01

    Air pollution is attributable to 7 million deaths per year, or one out of every eight deaths globally. In particular, high concentrations of particulate matter (PM), a major air pollutant, have significant impacts on health and regional climate in urban centers. Many of the most polluted places, largely in developing countries, go severely understudied. Additionally, high particulate matter levels can have an impact on the microphysical properties of clouds, impacting precipitation and regional climate. Semi-arid regions can be especially affected by small changes in precipitation. Here we characterize the physical and chemical properties of PM in one of the most PM-polluted cities in the world: Ulaanbaatar, Mongolia, a semi-arid region in central Asia. Twice monthly aerosol samples were collected over 10 months from a central location and analyzed for composition and ice nucleation activity. Almost all particles collected were inhalable, consisting primarily of mineral dust, soot, and sulfate-organic. In winter, all classes of PM increase in concentration, with increased sulfur concentrations, and the particles are less active towards heterogeneous ice nucleation. In addition, concurrent monthly average PM10, SO2, NOx, and O3 levels and meteorological data at a nearby location are reported and made publicly available. These measurements provide an unprecedented seasonal characterization of the size, shape, chemical structure, and ice nucleating activity of PM data from Ulaanbaatar. This 10-month field study, exploring a variety of aerosol properties in Ulaanbaatar, Mongolia, is one of very few such studies conducted in the region or in such a highly polluted environment. The results of this study may inform work done in other similarly situated and polluted cities in Asia and elsewhere.

  14. Dibble Ice Shelf

    NASA Image and Video Library

    2013-06-13

    This photo, aken onboard a National Science Foundation/NASA chartered Twin Otter aircraft, shows the ice front of Dibble Ice Shelf, East Antarctica, a significant melt water producer from the Wilkes Land region, East Antarctica.

  15. Greenland Ice Flow

    NASA Image and Video Library

    Greenland looks like a big pile of snow seen from space using a regular camera. But satellite radar interferometry helps us detect the motion of ice beneath the snow. Ice starts flowing from the fl...

  16. Looking for Ice

    NASA Image and Video Library

    2016-03-23

    This image was targeted for NASA Mars Reconnaissance Orbiter spacecraft to look at a candidate new crater on a lobate apron. Such aprons are often ice-rich, but the crater shows no bright material that would indicate ice.

  17. Alteration of Heterogeneous Ice Nucleation Properties Induced by Particle Aging

    NASA Astrophysics Data System (ADS)

    Sullivan, R. C.; Polen, M.; Beydoun, H.; Lawlis, E.; Ahern, A.; Jahn, L.; Hill, T. C. J.

    2015-12-01

    Aerosol particles that can serve as ice nuclei frequently experience rapid and extensive chemical aging during atmospheric transport. This is known to significantly alter some ice nucleation modes of the few types of ice nucleation particle systems where aging effects have been simulated, such as for mineral dust. Yet much of our understanding of atmospheric particle freezing properties is derived from measurements of fresh or unaged particles. We know almost nothing regarding how atmospheric aging might alter the freezing properties of biomass burning aerosol or biological particle nucleants. We have investigated the effects of simulated aging using a chamber reactor on the heterogeneous ice nucleation properties of biomass burning aerosol (BBA) and ice-active bacteria particles. Some types of aging were found to enhance the freezing ability of BBA, exhibited as a shift in a portion of the droplet freezing curve to warmer temperatures by a few °C. Ice-active bacteria were found to consistently loose their most ice-active nucleants after repeated aging cycles. The bacterial systems always retained significantly efficient ice active sites that still allowed them to induce freezing at mild/warm temperatures, despite this decrease in freezing ability. A comprehensive series of online single-particle mass spectrometry and offline spectromicroscopic analysis of individual particles was used to determine how the aging altered the aerosol's composition, and gain mechanistic insights into how this in turn altered the freezing properties. Our new ice nucleation framework that uses a continuous distribution of ice active site ability (contact angle) was used to interpret the droplet freezing spectra and understand how aging alters the internal and external variability, and rigidity, of the ice active sites.

  18. Cold adaptation of zinc metalloproteases in the thermolysin family from deep sea and arctic sea ice bacteria revealed by catalytic and structural properties and molecular dynamics: new insights into relationship between conformational flexibility and hydrogen bonding.

    PubMed

    Xie, Bin-Bin; Bian, Fei; Chen, Xiu-Lan; He, Hai-Lun; Guo, Jun; Gao, Xiang; Zeng, Yin-Xin; Chen, Bo; Zhou, Bai-Cheng; Zhang, Yu-Zhong

    2009-04-03

    Increased conformational flexibility is the prevailing explanation for the high catalytic efficiency of cold-adapted enzymes at low temperatures. However, less is known about the structural determinants of flexibility. We reported two novel cold-adapted zinc metalloproteases in the thermolysin family, vibriolysin MCP-02 from a deep sea bacterium and vibriolysin E495 from an Arctic sea ice bacterium, and compared them with their mesophilic homolog, pseudolysin from a terrestrial bacterium. Their catalytic efficiencies, k(cat)/K(m) (10-40 degrees C), followed the order pseudolysin < MCP-02 < E495 with a ratio of approximately 1:2:4. MCP-02 and E495 have the same optimal temperature (T(opt), 57 degrees C, 5 degrees C lower than pseudolysin) and apparent melting temperature (T(m) = 64 degrees C, approximately 10 degrees C lower than pseudolysin). Structural analysis showed that the slightly lower stabilities resulted from a decrease in the number of salt bridges. Fluorescence quenching experiments and molecular dynamics simulations showed that the flexibilities of the proteins were pseudolysin < MCP-02 < E495, suggesting that optimization of flexibility is a strategy for cold adaptation. Molecular dynamics results showed that the ordinal increase in flexibility from pseudolysin to MCP-02 and E495, especially the increase from MCP-02 to E495, mainly resulted from the decrease of hydrogen-bond stability in the dynamic structure, which was due to the increase in asparagine, serine, and threonine residues. Finally, a model for the cold adaptation of MCP-02 and E495 was proposed. This is the first report of the optimization of hydrogen-bonding dynamics as a strategy for cold adaptation and provides new insights into the structural basis underlying conformational flexibility.

  19. Ice electrode electrolytic cell

    DOEpatents

    Glenn, David F.; Suciu, Dan F.; Harris, Taryl L.; Ingram, Jani C.

    1993-01-01

    This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an ice layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the ice. The metal is then easily removed after melting the ice. In a second embodiment, the same ice-covered electrode can be employed to form powdered metals.

  20. Ice electrode electrolytic cell

    DOEpatents

    Glenn, D.F.; Suciu, D.F.; Harris, T.L.; Ingram, J.C.

    1993-04-06

    This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an ice layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the ice. The metal is then easily removed after melting the ice. In a second embodiment, the same ice-covered electrode can be employed to form powdered metals.

  1. Ice electrode electrolytic cell

    SciTech Connect

    Glenn, D.F.; Suciu, D.F.; Harris, T.L.; Ingram, J.C.

    1992-12-31

    This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an ice layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the ice. The metal is then easily removed after melting the ice. In a second embodiment, the same ice-covered electrode can be employed to form powdered metals.

  2. Glaciers and ice sheets as a biome.

    PubMed

    Anesio, Alexandre M; Laybourn-Parry, Johanna

    2012-04-01

    The tundra is the coldest biome described in typical geography and biology textbooks. Within the cryosphere, there are large expanses of ice in the Antarctic, Arctic and alpine regions that are not regarded as being part of any biome. During the summer, there is significant melt on the surface of glaciers, ice caps and ice shelves, at which point microbial communities become active and play an important role in the cycling of carbon and other elements within the cryosphere. In this review, we suggest that it is time to recognise the cryosphere as one of the biomes of Earth. The cryospheric biome encompasses extreme environments and is typified by truncated food webs dominated by viruses, bacteria, protozoa and algae with distinct biogeographical structures.

  3. Ice Formation on Wings

    NASA Technical Reports Server (NTRS)

    Ritz, L

    1939-01-01

    This report makes use of the results obtained in the Gottingen ice tunnel in which the atmospheric conditions are simulated and the process of ice formation photographed. The effect of ice formation is threefold: 1) added weight to the airplane; 2) a change in the lift and drag forces; 3) a change in the stability characteristics.

  4. Aircraft icing: Introduction

    NASA Technical Reports Server (NTRS)

    Enders, J. H.

    1979-01-01

    The objectives of the Workshop were as follows: (1) to assess the current understanding of fixed wing and rotorcraft operational icing environments and problems (2) to evaluate facilities requirements for R&D and certification purposes (3) to examine means of improving icing forecasts (4) to identify shortcomings in aeronautical icing knowledge which can be alleviated by new research and instrumentation development.

  5. Ice Cream Headaches

    MedlinePlus

    Diseases and Conditions Ice cream headaches By Mayo Clinic Staff Ice cream headaches are brief, stabbing headaches that can happen when you eat, drink or inhale something cold. Digging into an ice cream cone is a common trigger, but eating or ...

  6. The Antarctic Ice.

    ERIC Educational Resources Information Center

    Radok, Uwe

    1985-01-01

    The International Antarctic Glaciological Project has collected information on the East Antarctic ice sheet since 1969. Analysis of ice cores revealed climatic history, and radar soundings helped map bedrock of the continent. Computer models of the ice sheet and its changes over time will aid in predicting the future. (DH)

  7. Ice Versus Rock

    ERIC Educational Resources Information Center

    Rule, Audrey C.; Olson, Eric A.; Dehm, Janet

    2005-01-01

    During a snow bank exploration, students noticed "ice caves," or pockets, in some of the larger snow banks, usually below darker layers. Most of these caves had many icicles hanging inside. Students offered reasonable explanations of ice cave formation--squirrels, kids, snow blowers--and a few students came close to the true ice cave-formation…

  8. Ice Versus Rock

    ERIC Educational Resources Information Center

    Rule, Audrey C.; Olson, Eric A.; Dehm, Janet

    2005-01-01

    During a snow bank exploration, students noticed "ice caves," or pockets, in some of the larger snow banks, usually below darker layers. Most of these caves had many icicles hanging inside. Students offered reasonable explanations of ice cave formation--squirrels, kids, snow blowers--and a few students came close to the true ice cave-formation…

  9. Experiments in Ice Physics.

    ERIC Educational Resources Information Center

    Martin, P. F.; And Others

    1978-01-01

    Describes experiments in ice physics that demonstrate the behavior and properties of ice. Show that ice behaves as an ionic conductor in which charge is transferred by the movement of protons, its electrical conductivity is highly temperature-dependent, and its dielectric properties show dramatic variation in the kilohertz range. (Author/GA)

  10. The Antarctic Ice.

    ERIC Educational Resources Information Center

    Radok, Uwe

    1985-01-01

    The International Antarctic Glaciological Project has collected information on the East Antarctic ice sheet since 1969. Analysis of ice cores revealed climatic history, and radar soundings helped map bedrock of the continent. Computer models of the ice sheet and its changes over time will aid in predicting the future. (DH)

  11. Technology for Ice Rinks

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Ron Urban's International Ice Shows set up portable ice rinks for touring troupes performing on temporary rinks at amusement parks, sports arenas, dinner theaters, shopping malls and civic centers. Key to enhanced rink portability, fast freezing and maintaining ice consistency is a mat of flexible tubing called ICEMAT, an offshoot of a solar heating system developed by Calmac, Mfg. under contract with Marshall.

  12. Experiments in Ice Physics.

    ERIC Educational Resources Information Center

    Martin, P. F.; And Others

    1978-01-01

    Describes experiments in ice physics that demonstrate the behavior and properties of ice. Show that ice behaves as an ionic conductor in which charge is transferred by the movement of protons, its electrical conductivity is highly temperature-dependent, and its dielectric properties show dramatic variation in the kilohertz range. (Author/GA)

  13. Ice Formation Potential of Field-Collected Marine Biogenic Particles

    NASA Astrophysics Data System (ADS)

    Carrion-Matta, A.; Alpert, P. A.; Radway, J.; Kilthau, W.; Bothe, D.; Knopf, D. A.; Aller, J. Y.

    2013-12-01

    Marine biogenic particles composed mainly of sea salt and organic material aerosolized from a mesocosm in laboratory experiments have recently been found to act as ice nuclei. How these particles relate to those collected from sea spray under ambient conditions in the field is unknown. This study reports on the heterogeneous ice nucleation potential of particles collected during the marine aerosol characterization experiment (MACE) on the south shore of Long Island, New York. Ambient aerosol size distributions were measured and particles were collected on hydrophobically coated substrates and subsequently used for ice nucleation experiments using an ice nucleation cell coupled to an optical microscope. This technique allows detection of ice formation for temperatures between 200 and 273 K and for relative humidity with respect to ice (RHice) from 100% up to water saturation. Individual ice nucleating particles were identified for subsequent chemical and physical characterization using both X-ray and electron micro-spectroscopic techniques. Concentrations of bacteria, viruses, and transparent exopolymer particles (TEP) in the bulk seawater, sea-surface microlayer (SML), and in sea spray were determined using established methods and related to airborne sea spray particles and their ice nucleation potential. Onshore aerosol size distribution measurements taken at 5 m height and 10 m away from the breaking waves, revealed a peak maximum at 100 nm and Ntot = 6.8 x 10^2 cm^-3. Bacterial, viral, and TEP were found to be enriched in the SML. Ambient particles collected during MACE were found to nucleate ice efficiently, e. g. at 215 K, ice nucleation occurred on average at 125% RHice. Results of aerosol size distributions and ice nucleation efficiencies are compared to laboratory bubble bursting experiments in which natural seawater was used. The goal of this study is to understand the connection between sea spray aerosolization and atmospheric ice cloud formation and to

  14. Composition, Diversity, and Stability of Microbial Assemblages in Seasonal Lake Ice, Miquelon Lake, Central Alberta

    PubMed Central

    Bramucci, Anna; Han, Sukkyun; Beckers, Justin; Haas, Christian; Lanoil, Brian

    2013-01-01

    The most familiar icy environments, seasonal lake and stream ice, have received little microbiological study. Bacteria and Eukarya dominated the microbial assemblage within the seasonal ice of Miquelon Lake, a shallow saline lake in Alberta, Canada. The bacterial assemblages were moderately diverse and did not vary with either ice depth or time. The closest relatives of the bacterial sequences from the ice included Actinobacteria, Bacteroidetes, Proteobacteria, Verrucomicrobia, and Cyanobacteria. The eukaryotic assemblages were less conserved and had very low diversity. Green algae relatives dominated the eukaryotic gene sequences; however, a copepod and cercozoan were also identified, possibly indicating the presence of complete microbial loop. The persistence of a chlorophyll a peak at 25–30 cm below the ice surface, despite ice migration and brine flushing, indicated possible biological activity within the ice. This is the first study of the composition, diversity, and stability of seasonal lake ice. PMID:24832796

  15. Engineering functional nanothin multilayers on food packaging: ice-nucleating polyethylene films.

    PubMed

    Gezgin, Zafer; Lee, Tung-Ching; Huang, Qingrong

    2013-05-29

    Polyethylene is the most prevalent plastic and is commonly used as a packaging material. Despite its common use, there are not many studies on imparting functionalities to those films which can make them more desirable for frozen food packaging. Here, commercial low-density polyethylene (LDPE) films were oxidized by UV-ozone (UVO) treatment to obtain a negatively charged hydrophilic surface to allow fabrication of functional multilayers. An increase in hydrophilicity was observed when films were exposed to UVO for 4 min and longer. Thin multilayers were formed by dipping the UVO-treated films into biopolymer solutions, and extracellular ice nucleators (ECINs) were immobilized onto the film surface to form a functional top layer. Polyelectrolyte adsorption was studied and confirmed on silicon wafers by measuring the water contact angles of the layers and investigating the surface morphology via atomic force microscopy. An up to 4-5 °C increase in ice nucleation temperatures and an up to 10 min decrease in freezing times were observed with high-purity deionized water samples frozen in ECIN-coated LDPE films. Films retained their ice nucleation activity up to 50 freeze-thaw cycles. Our results demonstrate the potential of using ECIN-coated polymer films for frozen food application.

  16. Prospecting for ice association: characterization of freeze-thaw selected enrichment cultures from latitudinally distant soils.

    PubMed

    Wilson, Sandra L; Grogan, Paul; Walker, Virginia K

    2012-04-01

    Freeze-thaw stress has previously been shown to alter soil community structure and function. We sought to further investigate this stress on enriched microbial consortia with the aim of identifying microbes with ice-associating adaptations that facilitate survival. Enrichments were established to obtain culturable psychrotolerant microbes from soil samples from the latitudinal extremes of the Canadian Shield plateau. The resulting consortia were subjected to consecutive freeze-thaw cycles, and survivors were putatively identified by their 16S rRNA gene sequences. Even though the northerly site was exposed to longer, colder winters and large spring-time temperature fluctuations, the selective regime similarly affected both enriched consortia. Quantitative PCR and metagenomic sequencing were used to determine the frequency of a subset of the resistant microbes in the original enrichments. The metagenomes showed 22 initial genera, only 6 survived and these were not dominant prior to selection. When survivors were assayed for ice recrystallization inhibition and ice nucleation activities, over 60% had at least one of these properties. These phenotypes were not more prevalent in the northern enrichment, indicating that regarding these adaptations, the enrichment strategy yielded seemingly functionally similar consortia from each site.

  17. The importance of vertical resolution in sea ice algae production models

    NASA Astrophysics Data System (ADS)

    Duarte, Pedro; Assmy, Philipp; Hop, Haakon; Spreen, Gunnar; Gerland, Sebastian; Hudson, Stephen R.

    2015-05-01

    In this study an ice-algal mathematical model is used to resolve the vertical fine structure of sea ice with ice algae, and results are compared to simulations with ice algae located only at the bottom ice layer and to those where ice algae are distributed homogeneously across part of the ice column. Ice algae are reported to contribute 4-26% of overall Arctic Ocean primary production and are an important food source for the ice-associated ecosystem. Thus, it is important to estimate the future impacts of global warming on the contribution of ice algae to Arctic primary production. Primary production models, describing the relationships between ice-algal physiology and population dynamics, with environmental forcing and trophic interactions involving bacteria and grazers, can be applied to quantify such impacts. One important aspect in these models is how to represent the vertical distribution of ice algae in sea ice. In most models, only the bottom ice layer is considered where most of the algal biomass tends to be concentrated. However, since ice algae are also present along the entire ice column, this may lead to underestimation of ice-algal production. Some empirical data and model results suggest that ice algae located in the surface and interior layers may be kept at lower concentrations, in spite of high growth rates, due to grazing by micro- and meiofauna. Results obtained in this study show the importance of resolving vertically the distribution of ice algae to avoid bias in primary production estimates, well in line with empirical studies.

  18. On the Rocks: Microbiological Quality and Microbial Diversity of Packaged Ice in Southern California.

    PubMed

    Lee, Kun Ho; Ab Samad, Liana S; Lwin, Phillip M; Riedel, Stefan F; Magin, Ashley; Bashir, Mina; Vaishampayan, Parag A; Lin, Wei-Jen

    2017-06-01

    Ice is defined as a food and is frequently used in direct contact with food and beverages. Packaged ice is commercially produced and can be easily found in grocery and convenience stores. However, the quality and safety of packaged ice products is not consistent. The Packaged Ice Quality Control Standards manual (PIQCS) published by the International Packaged Ice Association provides the quality and processing standards for packaged ice produced by its members. Packaged ice produced on the premise of stores (on-site packaged ice) is not required to be in compliance with these standards. In this study, packaged ice produced by manufacturing plants or by in-store bagger (ISB) machines and on-site packaged ice were compared for their microbiological quality and microbial diversity. Our results revealed that 19% of the 120 on-site packaged ice samples did not meet the PIQCS microbial limit of 500 CFU/mL (or g) and also the absence of coliforms and Escherichia coli . Staphylococci were found in 34% of the on-site packaged ice samples, most likely through contamination from the packaging workers. None of the ISB and manufactured packaged ice samples had unacceptable microbial levels, and all were devoid of staphylococci. Salmonella was absent in all samples analyzed in this study. Microbial community analysis of ice based on 16S/18S rRNA targeted sequencing revealed a much higher microbial diversity and abundance in the on-site packaged ice than in the ISB ice. Proteobacteria, especially Alphaproteobacteria and Betaproteobacteria, were the dominant bacterial groups in all samples tested. Most of these bacteria were oligotrophic; however, a few opportunistic or potential pathogens were found at low levels in the on-site packaged ice but not in the ISB packaged ice. The types of microbes identified may provide information needed to investigate potential sources of contamination. Our data also suggest a need for enforcement of processing standards during the on

  19. Alaska marine ice atlas

    SciTech Connect

    LaBelle, J.C.; Wise, J.L.; Voelker, R.P.; Schulze, R.H.; Wohl, G.M.

    1982-01-01

    A comprehensive Atlas of Alaska marine ice is presented. It includes information on pack and landfast sea ice and calving tidewater glacier ice. It also gives information on ice and related environmental conditions collected over several years time and indicates the normal and extreme conditions that might be expected in Alaska coastal waters. Much of the information on ice conditions in Alaska coastal waters has emanated from research activities in outer continental shelf regions under assessment for oil and gas exploration and development potential. (DMC)

  20. Ice Observation Handbook, 1984

    DTIC Science & Technology

    1984-01-01

    which is navigable by surface vessels. Flaw polynya : A polynya between drift ice and fast ice. Floating ice: Any form of ice found floating in water...10 to 6/10 with many leads and polynyas , and the floes are generally not in contact with one another. Open water: A large area of freely navigable...the surface; its appearance may rapidly cover wide areas of water. 9l 2-9 7-7 Polynya : Any non-linear shaped opening enclosed in ice. Polynyas may

  1. Seasat and floating ice

    NASA Technical Reports Server (NTRS)

    Weeks, W. F.

    1974-01-01

    Data collected by SEASAT would be useful in developing predictive physical models for the drift and deformation of sea ice, for estimating the heat budget of the polar seas, for the optimum routing of shipping through pack ice areas, for the design of both offshore structures and shipping capable of surviving in heavy pack ice, and for the tracking of large icebergs and ice islands. The instrument package for SEASAT-A is particularly useful for studying sea ice in that the Coherent Imaging Radar (CIR), the Scanning Multifrequency Microwave Radiometer (SMMR) and the Compressed Pulse Radar Altimeter (CPRA) are not limited by the presence of clouds.

  2. Arctic ice management

    NASA Astrophysics Data System (ADS)

    Desch, Steven J.; Smith, Nathan; Groppi, Christopher; Vargas, Perry; Jackson, Rebecca; Kalyaan, Anusha; Nguyen, Peter; Probst, Luke; Rubin, Mark E.; Singleton, Heather; Spacek, Alexander; Truitt, Amanda; Zaw, Pye Pye; Hartnett, Hilairy E.

    2017-01-01

    As the Earth's climate has changed, Arctic sea ice extent has decreased drastically. It is likely that the late-summer Arctic will be ice-free as soon as the 2030s. This loss of sea ice represents one of the most severe positive feedbacks in the climate system, as sunlight that would otherwise be reflected by sea ice is absorbed by open ocean. It is unlikely that CO2 levels and mean temperatures can be decreased in time to prevent this loss, so restoring sea ice artificially is an imperative. Here we investigate a means for enhancing Arctic sea ice production by using wind power during the Arctic winter to pump water to the surface, where it will freeze more rapidly. We show that where appropriate devices are employed, it is possible to increase ice thickness above natural levels, by about 1 m over the course of the winter. We examine the effects this has in the Arctic climate, concluding that deployment over 10% of the Arctic, especially where ice survival is marginal, could more than reverse current trends of ice loss in the Arctic, using existing industrial capacity. We propose that winter ice thickening by wind-powered pumps be considered and assessed as part of a multipronged strategy for restoring sea ice and arresting the strongest feedbacks in the climate system.

  3. ICE SLURRY APPLICATIONS

    PubMed Central

    Kauffeld, M.; WANG, M. J.; Goldstein, V.; Kasza, K. E.

    2011-01-01

    The role of secondary refrigerants is expected to grow as the focus on the reduction of greenhouse gas emissions increases. The effectiveness of secondary refrigerants can be improved when phase changing media are introduced in place of single phase media. Operating at temperatures below the freezing point of water, ice slurry facilitates several efficiency improvements such as reductions in pumping energy consumption as well as lowering the required temperature difference in heat exchangers due to the beneficial thermo-physical properties of ice slurry. Research has shown that ice slurry can be engineered to have ideal ice particle characteristics so that it can be easily stored in tanks without agglomeration and then be extractable for pumping at very high ice fraction without plugging. In addition ice slurry can be used in many direct contact food and medical protective cooling applications. This paper provides an overview of the latest developments in ice slurry technology. PMID:21528014

  4. Arctic landfast sea ice

    NASA Astrophysics Data System (ADS)

    Konig, Christof S.

    Landfast ice is sea ice which forms and remains fixed along a coast, where it is attached either to the shore, or held between shoals or grounded icebergs. Landfast ice fundamentally modifies the momentum exchange between atmosphere and ocean, as compared to pack ice. It thus affects the heat and freshwater exchange between air and ocean and impacts on the location of ocean upwelling and downwelling zones. Further, the landfast ice edge is essential for numerous Arctic mammals and Inupiat who depend on them for their subsistence. The current generation of sea ice models is not capable of reproducing certain aspects of landfast ice formation, maintenance, and disintegration even when the spatial resolution would be sufficient to resolve such features. In my work I develop a new ice model that permits the existence of landfast sea ice even in the presence of offshore winds, as is observed in mature. Based on viscous-plastic as well as elastic-viscous-plastic ice dynamics I add tensile strength to the ice rheology and re-derive the equations as well as numerical methods to solve them. Through numerical experiments on simplified domains, the effects of those changes are demonstrated. It is found that the modifications enable landfast ice modeling, as desired. The elastic-viscous-plastic rheology leads to initial velocity fluctuations within the landfast ice that weaken the ice sheet and break it up much faster than theoretically predicted. Solving the viscous-plastic rheology using an implicit numerical method avoids those waves and comes much closer to theoretical predictions. Improvements in landfast ice modeling can only verified in comparison to observed data. I have extracted landfast sea ice data of several decades from several sources to create a landfast sea ice climatology that can be used for that purpose. Statistical analysis of the data shows several factors that significantly influence landfast ice distribution: distance from the coastline, ocean depth, as

  5. Bacterial communities from Arctic seasonal sea ice are more compositionally variable than those from multi-year sea ice.

    PubMed

    Hatam, Ido; Lange, Benjamin; Beckers, Justin; Haas, Christian; Lanoil, Brian

    2016-10-01

    Arctic sea ice can be classified into two types: seasonal ice (first-year ice, FYI) and multi-year ice (MYI). Despite striking differences in the physical and chemical characteristics of FYI and MYI, and the key role sea ice bacteria play in biogeochemical cycles of the Arctic Ocean, there are a limited number of studies comparing the bacterial communities from these two ice types. Here, we compare the membership and composition of bacterial communities from FYI and MYI sampled north of Ellesmere Island, Canada. Our results show that communities from both ice types were dominated by similar class-level phylogenetic groups. However, at the operational taxonomic unit (OTU) level, communities from MYI and FYI differed in both membership and composition. Communities from MYI sites had consistent structure, with similar membership (presence/absence) and composition (OTU abundance) independent of location and year of sample. By contrast, communities from FYI were more variable. Although FYI bacterial communities from different locations and different years shared similar membership, they varied significantly in composition. Should these findings apply to sea ice across the Arctic, we predict increased compositional variability in sea ice bacterial communities resulting from the ongoing transition from predominantly MYI to FYI, which may impact nutrient dynamics in the Arctic Ocean.

  6. Microbial Contamination of Ice Machines Is Mediated by Activated Charcoal Filtration Systems in a City Hospital.

    PubMed

    Yorioka, Katsuhiro; Oie, Shigeharu; Hayashi, Koji; Kimoto, Hiroo; Furukawa, Hiroyuki

    2016-06-01

    Although microbial contamination of ice machines has been reported, no previous study has addressed microbial contamination of ice produced by machines equipped with activated charcoal (AC) filters in hospitals. The aim of this study was to provide clinical data for evaluating AC filters to prevent microbial contamination of ice. We compared microbial contamination in ice samples produced by machines with (n = 20) and without an AC filter (n = 40) in Shunan City Shinnanyo Municipal Hospital. All samples from the ice machine equipped with an AC filter contained 10-116 CFUs/g of glucose nonfermenting gram-negative bacteria such as Pseudomonas aeruginosa and Chryseobacterium meningosepticum. No microorganisms were detected in samples from ice machines without AC filters. After the AC filter was removed from the ice machine that tested positive for Gram-negative bacteria, the ice was resampled (n = 20). Analysis found no contaminants. Ice machines equipped with AC filters pose a serious risk factor for ice contamination. New filter-use guidelines and regulations on bacterial detection limits to prevent contamination of ice in healthcare facilities are necessary.

  7. Biological Ice Nuclei: They are Everywhere, What are Their Roles? (Invited)

    NASA Astrophysics Data System (ADS)

    Schnell, R. C.

    2009-12-01

    Biological ice nuclei active at temperatures warmer than -2C were first observed in the late 1960s associated with decaying grass and tree leaves; discovered more by accident than in a planned experiment. The active component of the decaying leaves was subsequently found to be produced by a few living bacteria, the two most ubiquitous being strains of P. syringae and E. herbicola. The active bacterial ice nuclei are easily deactivated by anaerobic, chemical and heat stresses. The same grass and tree leaves, when well decayed, generally contain less active ice nuclei (threshold temperatures of -5C to - 6C) in the 0.1 micron diameter range compared to the larger (1 micron) bacteria associated ice nuclei. The well decayed leaf litter ice nuclei are stable over a wide range of stresses and time; some samples of leaf derived nuclei stored at room temperature have exhibited the same ice nucleus concentration for over 30 years. Fungi also have active ice nuclei that are stable over many decades. Active ice nuclei are found in marine waters associated with plankton, and are produced by at least one marine dinoflagellate (Heterocapsa niei) that expresses ice nucleus activity almost as warm as terrestrial bacteria ice nuclei. Living ice nucleus bacteria have been found in marine fogs far at sea, in precipitation in Antarctica as well as over many continental areas, in air in the high Arctic, on vegetation around the world, on remote ice bound islands, and growing on and inside water storing vegetation on isolated tropical mountain peaks. But why? What is the evolutionary advantage for the ice nucleus gene to be expressed in such a wide range of environments, by greatly different species? There is an energy cost for bacteria and fungi to support the ice gene, so it probably is not a genetic anomaly. Possibly the ice nuclei play many roles? These could include damaging plants to acquire a food source, an aid in survival and dispersal in clouds, initiation of precipitation to

  8. Preparing and Analyzing Iced Airfoils

    NASA Technical Reports Server (NTRS)

    Vickerman, Mary B.; Baez, Marivell; Braun, Donald C.; Cotton, Barbara J.; Choo, Yung K.; Coroneos, Rula M.; Pennline, James A.; Hackenberg, Anthony W.; Schilling, Herbert W.; Slater, John W.; hide

    2004-01-01

    SmaggIce version 1.2 is a computer program for preparing and analyzing iced airfoils. It includes interactive tools for (1) measuring ice-shape characteristics, (2) controlled smoothing of ice shapes, (3) curve discretization, (4) generation of artificial ice shapes, and (5) detection and correction of input errors. Measurements of ice shapes are essential for establishing relationships between characteristics of ice and effects of ice on airfoil performance. The shape-smoothing tool helps prepare ice shapes for use with already available grid-generation and computational-fluid-dynamics software for studying the aerodynamic effects of smoothed ice on airfoils. The artificial ice-shape generation tool supports parametric studies since ice-shape parameters can easily be controlled with the artificial ice. In such studies, artificial shapes generated by this program can supplement simulated ice obtained from icing research tunnels and real ice obtained from flight test under icing weather condition. SmaggIce also automatically detects geometry errors such as tangles or duplicate points in the boundary which may be introduced by digitization and provides tools to correct these. By use of interactive tools included in SmaggIce version 1.2, one can easily characterize ice shapes and prepare iced airfoils for grid generation and flow simulations.

  9. Ice flow of the Antarctica Ice Sheet

    NASA Astrophysics Data System (ADS)

    Mouginot, J.; Scheuchl, B.; Rignot, E. J.

    2011-12-01

    Ice velocity is fundamental characteristic of the dynamics of ice sheets and is essential to know for calculating the mass budget of ice sheet and for controlling ice sheet numerical models with realistic boundary conditions. Until recently, data were mostly available on a discrete basis over small areas with variable precision. Here, we report on our results of processing ice velocity from the interferometric synthetic-aperture radar data acquired by ALOS PALSAR in 2006 to 2010 by the Japan Aerospace Exploration Agency (JAXA), by ENVISAT ASAR in 2007 to 2009, by RADARSAT-2 in 2009 and 2011, by RADARSAT-1 in 1997 and 2000 and by ERS-1 & -2 in 1996 in the framework of the International Polar Year 2007-2009. The result is the most comprehensive and precise high-resolution digital map of ice motion ever produced on the Antarctic continent. While important surprises are found along the coastline, it is in the interior that this map is revealing the most interesting features. The data reveal widespread, patterned, enhanced flow with tributary glaciers reaching hundreds to thousands of kilometers inland, over the entire continent. We show that the ice motion along these flow features has a strong basal slip component. This has far reaching implications for the modeling of ice sheet flow and evolution. In addition, our multi-year coverage of the coastal sectors reveal the beginning of an acceleration on Thwaites glacier and a wave of accelerated flow propagating inland rapidly on Pine Island Glacier between 2006 and 2010. This work was conducted at the Department of Earth System Science, University of California Irvine under a contract with the National Aeronautics and Space Administration's MEaSUREs program.

  10. Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover

    DTIC Science & Technology

    2013-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Sunlight, Sea Ice, and the Ice Albedo Feedback in a...ice age, and iv) onset dates of melt and freezeup. 4. Assess the magnitude of the contribution from ice- albedo feedback to the observed decrease of...COVERED 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover 5a

  11. Consider an Ice Stream.

    NASA Astrophysics Data System (ADS)

    Bindschadler, R.

    2002-12-01

    Forty years ago, John Nye was one of the leaders who introduced the rigors of classical physics to glaciology. His elegant treatments frequently took advantage of the then recent discovery that ice could be approximated as a plastic material. With this viewpoint, Nye was able to explain the shape of ice sheets and glaciers, to predict the expected pattern of stress and velocity within a glacier, and to derive the advance and retreat of a glacier from the record of accumulation and ablation. These advances have given generations of glaciologists tools to interpret the excellent observational record of glacier behavior and variation. In the 1980s, glaciologist, weaned on these works of Nye and of other similarly adept colleagues, carried their lessons to West Antarctica to study ice streams, the vast conveyor belts of ice that discharged nearly as much Antarctic ice as the much larger East Antarctic ice sheet. Ice streams were a glaciological conundrum. Despite the gently sloping surface, these broad features roared along, moving fastest when the gravitational impetus was least. After two decades of research, ice streams still have not given up all their secrets, yet much is now known. Internal deformation is negligible. Basal friction is frequently nil leaving the shattered margins as the primary means to avoid rapid wastage of the ice sheet. Within the margins, the resistive force results from a delicate balance of heat and evolving ice fabrics. Nevertheless, the bed beneath an ice stream cannot be ignored. It is ultimately the state of the underlying marine sediment that determines whether the ice stream can slide at all. There too, the heat balance is critical with an influx of water required to keep the bed wet enough to let the streams glide along. Ice stream research has been the portal through which glaciologists have seen and identified the complexities of West Antarctic ice sheet dynamics. Remarkably, nearly all time scales seem important. Ice stream

  12. Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Stroeve, J. C.; Fetterer, F.; Knowles, K.; Meier, W.; Serreze, M.; Arbetter, T.

    2004-12-01

    Of all the recent observed changes in the Arctic environment, the reduction of sea ice cover stands out most prominantly. Several independent analysis have established a trend in Arctic ice extent of -3% per decade from the late 1970s to the late 1990s, with a more pronounced trend in summer. The overall downward trend in ice cover is characterized by strong interannual variability, with a low September ice extent in one year typically followed by recovery the next September. Having two extreme minimum years, such as what was observed in 2002 and 2003 is unusual. 2004 marks the third year in a row of substantially below normal sea ice cover in the Arctic. Early summer 2004 appeared unusual in terms of ice extent, with May a record low for the satellite period (1979-present) and June also exhibiting below normal ice extent. August 2004 extent is below that of 2003 and large reductions in ice cover are observed once again off the coasts of Siberia and Alaska and the Greenland Sea. Neither the 2002 or 2003 anomaly appeared to be strongly linked to the positive phase of the Arctic Oscillation (AO) during the preceding winter. Similarly, the AO was negative during winter 2003/2004. In the previous AO framework of Rigor et al (2002), a positive winter AO implied preconditioning of the ice cover to extensive summer decay. In this hypothesis, the AO does not explain all aspects of the recent decline in Arctic ice cover, such as the extreme minima of 2002, 2003 and 2004. New analysis by Rigor and Wallace (2004) suggest that the very positive AO state from 1989-1995 can explain the recent sea ice minima in terms of changes in the Arctic surface wind field associated with the previous high AO state. However, it is also reasonable to expect that a general decrease in ice thickness accompanying warming would manifest itself as greater sensitivity of the ice pack to wind forcings and albedo feedbacks. The decrease in multiyear ice and attendant changes in ice thickness

  13. Sea Ice and Oceanographic Conditions.

    ERIC Educational Resources Information Center

    Oceanus, 1986

    1986-01-01

    The coastal waters of the Beaufort Sea are covered with ice three-fourths of the year. These waters (during winter) are discussed by considering: consolidation of coastal ice; under-ice water; brine circulation; biological energy; life under the ice (including kelp and larger animals); food chains; and ice break-up. (JN)

  14. Sea Ice and Oceanographic Conditions.

    ERIC Educational Resources Information Center

    Oceanus, 1986

    1986-01-01

    The coastal waters of the Beaufort Sea are covered with ice three-fourths of the year. These waters (during winter) are discussed by considering: consolidation of coastal ice; under-ice water; brine circulation; biological energy; life under the ice (including kelp and larger animals); food chains; and ice break-up. (JN)

  15. Prospecting for Martian Ice

    NASA Technical Reports Server (NTRS)

    McBride, S. A.; Allen, C. C.; Bell, M. S.

    2005-01-01

    During high Martian obliquity, ice is stable to lower latitudes than predicted by models of present conditions and observed by the Gamma Ray Spectrometer (approx. 60 deg N). An ice-rich layer deposited at mid-latitudes could persist to the present day; ablation of the top 1 m of ice leaving a thin insulating cover could account for lack of its detection by GRS. The presence of an ice-layer in the mid-latitudes is suggested by a network of polygons, interpreted as ice-wedge cracks. This study focuses on an exceptional concentration of polygons in Western Utopia (section of Casius quadrangle, roughly 40 deg - 50 deg N, 255 deg - 300 deg W). We attempt to determine the thickness and age of this ice layer through crater-polygons relations.

  16. Subsurface Ice Probe

    NASA Technical Reports Server (NTRS)

    Hecht, Michael; Carsey, Frank

    2005-01-01

    The subsurface ice probe (SIPR) is a proposed apparatus that would bore into ice to depths as great as hundreds of meters by melting the ice and pumping the samples of meltwater to the surface. Originally intended for use in exploration of subsurface ice on Mars and other remote planets, the SIPR could also be used on Earth as an alternative to coring, drilling, and melting apparatuses heretofore used to sample Arctic and Antarctic ice sheets. The SIPR would include an assembly of instrumentation and electronic control equipment at the surface, connected via a tether to a compact assembly of boring, sampling, and sensor equipment in the borehole (see figure). Placing as much equipment as possible at the surface would help to attain primary objectives of minimizing power consumption, sampling with high depth resolution, and unobstructed imaging of the borehole wall. To the degree to which these requirements would be satisfied, the SIPR would offer advantages over the aforementioned ice-probing systems.

  17. Producing desired ice faces

    PubMed Central

    Shultz, Mary Jane; Brumberg, Alexandra; Bisson, Patrick J.; Shultz, Ryan

    2015-01-01

    The ability to prepare single-crystal faces has become central to developing and testing models for chemistry at interfaces, spectacularly demonstrated by heterogeneous catalysis and nanoscience. This ability has been hampered for hexagonal ice, Ih––a fundamental hydrogen-bonded surface––due to two characteristics of ice: ice does not readily cleave along a crystal lattice plane and properties of ice grown on a substrate can differ significantly from those of neat ice. This work describes laboratory-based methods both to determine the Ih crystal lattice orientation relative to a surface and to use that orientation to prepare any desired face. The work builds on previous results attaining nearly 100% yield of high-quality, single-crystal boules. With these methods, researchers can prepare authentic, single-crystal ice surfaces for numerous studies including uptake measurements, surface reactivity, and catalytic activity of this ubiquitous, fundamental solid. PMID:26512102

  18. The Fifth International Ice Nucleation Workshop Activities FIN-1 and FIN-2: Overview and Selected Results

    NASA Astrophysics Data System (ADS)

    Moehler, O.; Cziczo, D. J.; DeMott, P. J.; Hiranuma, N.; Petters, M. D.

    2015-12-01

    The role of aerosol particles for ice formation in clouds is one of the largest uncertainties in understanding the Earth's weather and climate systems, which is related to the poor knowledge of ice nucleation microphysics or of the nature and atmospheric abundance of ice nucleating particles (INPs). During the recent years, new mobile instruments were developed for measuring the concentration, size and chemical composition of INPs, which were tested during the three-part Fifth International Ice Nucleation (FIN) workshop. The FIN activities addressed not only instrument issues, but also important science topics like the nature of atmospheric INP and cloud ice residuals, the ice nucleation activity of relevant atmospheric aerosols, or the parameterization of ice formation in atmospheric weather and climate models. The first activity FIN-1 was conducted during November 2014 at the AIDA cloud chamber. It involved co-locating nine single particle mass spectrometers to evaluate how well they resolve the INP and ice residual composition and how spectra from different instruments compare for relevant atmospheric aerosols. We conducted about 90 experiments with mineral, carbonaceous and biological aerosol types, some also coated with organic and inorganic compounds. The second activity FIN-2 was conducted during March 2015 at the AIDA facility. A total of nine mobile INP instruments directly sampled from the AIDA aerosol chambers. Wet suspension and filter samples were also taken for offline INP processing. A refereed blind intercomparison was conducted during two days of the FIN-2 activity. The third activity FIN-3 will take place at the Desert Research Institute's Storm Peak Laboratory (SPL) in order to test the instruments' performance in the field. This contribution will introduce the FIN activities, summarize first results from the formal part of FIN-2, and discuss selected results, mainly from FIN-1 for the effect of coating on the ice nucleation (IN) by mineral

  19. Back To Bacteria.

    ERIC Educational Resources Information Center

    Flannery, Maura C.

    1997-01-01

    Explores new research about bacteria. Discusses bacterial genomes, archaea, unusual environments, evolution, pathogens, bacterial movement, biofilms, bacteria in the body, and a bacterial obsession. Contains 29 references. (JRH)

  20. Back To Bacteria.

    ERIC Educational Resources Information Center

    Flannery, Maura C.

    1997-01-01

    Explores new research about bacteria. Discusses bacterial genomes, archaea, unusual environments, evolution, pathogens, bacterial movement, biofilms, bacteria in the body, and a bacterial obsession. Contains 29 references. (JRH)

  1. Ice nucleation efficiency of natural dust samples in the immersion mode

    NASA Astrophysics Data System (ADS)

    Kaufmann, Lukas; Marcolli, Claudia; Hofer, Julian; Pinti, Valeria; Hoyle, Christopher R.; Peter, Thomas

    2016-09-01

    A total of 12 natural surface dust samples, which were surface-collected on four continents, most of them in dust source regions, were investigated with respect to their ice nucleation activity. Dust collection sites were distributed across Africa, South America, the Middle East, and Antarctica. Mineralogical composition has been determined by means of X-ray diffraction. All samples proved to be mixtures of minerals, with major contributions from quartz, calcite, clay minerals, K-feldspars, and (Na, Ca)-feldspars. Reference samples of these minerals were investigated with the same methods as the natural dust samples. Furthermore, Arizona test dust (ATD) was re-evaluated as a benchmark. Immersion freezing of emulsion and bulk samples was investigated by differential scanning calorimetry. For emulsion measurements, water droplets with a size distribution peaking at about 2 µm, containing different amounts of dust between 0.5 and 50 wt % were cooled until all droplets were frozen. These measurements characterize the average freezing behaviour of particles, as they are sensitive to the average active sites present in a dust sample. In addition, bulk measurements were conducted with one single 2 mg droplet consisting of a 5 wt % aqueous suspension of the dusts/minerals. These measurements allow the investigation of the best ice-nucleating particles/sites available in a dust sample. All natural dusts, except for the Antarctica and ATD samples, froze in a remarkably narrow temperature range with the heterogeneously frozen fraction reaching 10 % between 244 and 250 K, 25 % between 242 and 246 K, and 50 % between 239 and 244 K. Bulk freezing occurred between 255 and 265 K. In contrast to the natural dusts, the reference minerals revealed ice nucleation temperatures with 2-3 times larger scatter. Calcite, dolomite, dolostone, and muscovite can be considered ice nucleation inactive. For microcline samples, a 50 % heterogeneously frozen fraction occurred above 245 K for all

  2. Isolation and identification of an ice-nucleating bacterium from the gills of the intertidal bivalve mollusc Geukensia demissa.

    PubMed

    Loomis, S H.; Zinser, M

    2001-07-01

    In the fall, freeze tolerant intertidal invertebrates usually produce ice-nucleating proteins that are secreted into the hemolymph. These proteins help protect against freeze damage by insuring that ice formation is limited to extracellular spaces. Geukensia demissa, a freeze tolerant, salt marsh bivalve mollusc was examined for the presence of ice nucleating proteins. The ice-nucleating temperature (INT) of the hemolymph was not significantly different from artificial seawater of the same salinity indicating the lack of an ice nucleating protein in the hemolymph. The palial fluid did have an elevated INT, indicating the presence of an ice nucleator. The INT of the palial fluid was significantly reduced by boiling and filtration through a 0.45-&mgr;m filter. High INT was also observed in the seawater associated with the bivalves, and was demonstrated in water samples collected from salt marshes but not sand and pebble beaches. Moreover, the INT of water samples collected from a salt marsh decreased in the summer. All of these data suggest that the ice-nucleating agents in the hemolymph and the seawater are ice-nucleating bacteria. One species of ice-nucleating bacteria, Pseudomonas fulva was isolated from the gills of Geukensia. These bacteria could perform the same function as hemolymph ice-nucleating proteins by limiting ice formation to extracellular compartments.

  3. Triangular ice crystals

    NASA Astrophysics Data System (ADS)

    Murray, Benjamin; Salzmann, Christoph; Heymsfield, Andrew; Neely, Ryan

    2014-05-01

    We are all familiar with the hexagonal form of snow crystals and it is well established that this shape is derived from the arrangement of water molecules in the crystal lattice. However, crystals with a triangular form are often found in the Earth's atmosphere and the reason for this non-hexagonal shape has remained elusive. Recent laboratory work has shed light on why ice crystals should take on this triangular or three-fold scalene habit. Studies of the crystal structure of ice have shown that ice which initially crystallises can be made of up of hexagonal layers which are interlaced with cubic layers to produce a 'stacking disordered ice'. The degree of stacking disorder can vary from crystals which are dominantly hexagonal with a few cubic stacking faults, through to ice where the cubic and hexagonal sequences are fully randomised. The introduction of stacking disorder to ice crystals reduces the symmetry of the crystal from 6-fold (hexagonal) to 3-fold (triangular); this offers an explanation for the long standing problem of why some atmospheric ice crystals have a triangular habit. We discuss the implications of triangular crystals for halos, radiative properties, and also discuss the implications for our understanding of the nucleation and early stages of ice crystal growth for ice crystals in the atmosphere.

  4. Ice barrier construction

    SciTech Connect

    Finucane, R. G.; Jahns, H. O.

    1985-06-18

    A method is provided for constructing spray ice barriers to protect offshore structures in a frigid body of water from mobile ice, waves and currents. Water is withdrawn from the body of water and is sprayed through ambient air which is below the freezing temperature of the water so that a substantial amount of the water freezes as it passes through the air. The sprayed water is directed to build up a mass of ice having a size and shape adapted to protect the offshore structure. Spray ice barriers can also be constructed for the containment of pollutant spills.

  5. Ice age paleotopography.

    PubMed

    Peltier, W R

    1994-07-08

    A gravitationally self-consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the Last Glacial Maximum (LGM). The results show that LGM ice volume was approximately 35 percent lower than suggested by the CLIMAP reconstruction and the maximum heights of the main Laurentian and Fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level. Use of these Ice Age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the CLIMAP data set.

  6. Ice age paleotopography

    SciTech Connect

    Peltier, W.R. )

    1994-07-08

    A gravitationally self-consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the Last Glacial Maximum (LGM). The results show that LGM ice volume was approximately 35 percent lower than suggested by the CLIMAP reconstruction and the maximum heights of the main Laurentian and Fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level. Use of these Ice Age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the CLIMAP data set.

  7. An ice lithography instrument.

    PubMed

    Han, Anpan; Chervinsky, John; Branton, Daniel; Golovchenko, J A

    2011-06-01

    We describe the design of an instrument that can fully implement a new nanopatterning method called ice lithography, where ice is used as the resist. Water vapor is introduced into a scanning electron microscope (SEM) vacuum chamber above a sample cooled down to 110 K. The vapor condenses, covering the sample with an amorphous layer of ice. To form a lift-off mask, ice is removed by the SEM electron beam (e-beam) guided by an e-beam lithography system. Without breaking vacuum, the sample with the ice mask is then transferred into a metal deposition chamber where metals are deposited by sputtering. The cold sample is then unloaded from the vacuum system and immersed in isopropanol at room temperature. As the ice melts, metal deposited on the ice disperses while the metals deposited on the sample where the ice had been removed by the e-beam remains. The instrument combines a high beam-current thermal field emission SEM fitted with an e-beam lithography system, cryogenic systems, and a high vacuum metal deposition system in a design that optimizes ice lithography for high throughput nanodevice fabrication. The nanoscale capability of the instrument is demonstrated with the fabrication of nanoscale metal lines.

  8. An ice lithography instrument

    SciTech Connect

    Han, Anpan; Chervinsky, John; Branton, Daniel; Golovchenko, J. A.

    2011-06-15

    We describe the design of an instrument that can fully implement a new nanopatterning method called ice lithography, where ice is used as the resist. Water vapor is introduced into a scanning electron microscope (SEM) vacuum chamber above a sample cooled down to 110 K. The vapor condenses, covering the sample with an amorphous layer of ice. To form a lift-off mask, ice is removed by the SEM electron beam (e-beam) guided by an e-beam lithography system. Without breaking vacuum, the sample with the ice mask is then transferred into a metal deposition chamber where metals are deposited by sputtering. The cold sample is then unloaded from the vacuum system and immersed in isopropanol at room temperature. As the ice melts, metal deposited on the ice disperses while the metals deposited on the sample where the ice had been removed by the e-beam remains. The instrument combines a high beam-current thermal field emission SEM fitted with an e-beam lithography system, cryogenic systems, and a high vacuum metal deposition system in a design that optimizes ice lithography for high throughput nanodevice fabrication. The nanoscale capability of the instrument is demonstrated with the fabrication of nanoscale metal lines.

  9. Electrical Properties of Ice

    DTIC Science & Technology

    1993-08-01

    Back in 1957 Decroly et al. (1957) carried out an experiment that was for a long time considered to be decisive in proving the proton nature of ice...be discussed in detail in the Charge Exchange at Ice/Metal Interfaces section). That is why Decroly et al. used layers of fro- zen IIF between ice...conductivity can be made only with respect to ice surfaces from the experiments of Decroly et al. Unfortunately, even this inference couldn’t be drawn from

  10. Sunlight off the ice

    NASA Image and Video Library

    2017-09-27

    Sunlight reflecting off of ice in the Bellingshausen Sea on Oct. 19, 2012. Credit: NASA / George Hale NASA's Operation IceBridge is an airborne science mission to study Earth's polar ice. For more information about IceBridge, visit: www.nasa.gov/icebridge NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  11. Wave-ice Interaction and the Marginal Ice Zone

    DTIC Science & Technology

    2015-09-30

    concentrations at the time. Any ice present appeared to be fragments of deformed ice (ridges), as most of the level ice had melted . Figure 1: Final...the buoys had approached the edge of the melting pack ice , from late August, when the vast floes had already fragmented due to dynamics and...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Wave- ice interaction and the Marginal Ice Zone Prof

  12. Ice as a reservoir for pathogenic human viruses: specifically, caliciviruses, influenza viruses, and enteroviruses.

    PubMed

    Smith, Alvin W; Skilling, Douglas E; Castello, John D; Rogers, Scott O

    2004-01-01

    Hundreds of isolates of viable bacteria and fungi have been recovered from ancient ice and permafrost. Evidence supports the hypothesis that viral pathogens also are preserved in ice repositories, such as glaciers, ice sheets, and lake ice. Proof may depend upon narrowing the search by applying specific criteria, which would target candidate viruses. Such criteria include viral pathogens likely to occur in great abundance, likely to be readily transported into ice, and then participate in ongoing disease cycles suggestive of their having been deposited in and subsequently released from ice. Caliciviruses, influenza A, and some enteroviruses appear to satisfy all three criteria. Environmental ice appears to be an important abiotic reservoir for pathogenic microbes. World health and eradication of specific pathogens could be affected by this huge reservoir. Copyright 2004 Elsevier Ltd.

  13. Ice-on-ice impact experiments.

    NASA Astrophysics Data System (ADS)

    Kato, Manabu; Iijima, Yu-Ichi; Arakawa, Masahiko; Okimura, Yasuyuki; Fujimura, Akio; Maeno, Norikazu; Mizutani, Hitoshi

    1995-02-01

    Impact experiments, cratering and fragmentation, on water ice were performed in order to test the scaling laws previously constructed on rocks and sands for studying the collision process in the planetary history. The installation of a vertical gas gun in a cold room at -18°C (255 K) made it possible to use a projectile of water ice and to get the detailed mass distribution of ice fragments. Experimental results indicated the necessity for large modification of those scaling laws. Material dependence was investigated by using projectiles of ice, aluminum, and polycarbonate. Differences were observed in the morphology and efficiencies of cratering and in the energies required to initiate the fragmentation. Moreover, an abrupt increase of cratering efficiency, suggesting a change of excavation mechanism, was found at a critical diameter of spalled crater. The mass (size) distribution of small ice fragments obeyed a power law with an exponent significantly larger than that in rocks. The exponent was the same as that in Saturn's ring particles estimated from the data by the microwave occultation, which indicates a collisional disruption ring origin.

  14. Small Airframe Manufacturer's Icing Perspective

    NASA Technical Reports Server (NTRS)

    Hoppins, Jim

    2009-01-01

    This viewgraph presentation describes the icing effects, risk mitigation practices, and icing certifications for various Cessna small aircraft models. NASA's role in the development of simulation tools for icing certifications is also discussed.

  15. Arctic Sea Ice Maximum 2011

    NASA Image and Video Library

    AMSR-E Arctic Sea Ice: September 2010 to March 2011: Scientists tracking the annual maximum extent of Arctic sea ice said that 2011 was among the lowest ice extents measured since satellites began ...

  16. [Tail Plane Icing

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Aviation Safety Program initiated by NASA in 1997 has put greater emphasis in safety related research activities. Ice-contaminated-tailplane stall (ICTS) has been identified by the NASA Lewis Icing Technology Branch as an important activity for aircraft safety related research. The ICTS phenomenon is characterized as a sudden, often uncontrollable aircraft nose- down pitching moment, which occurs due to increased angle-of-attack of the horizontal tailplane resulting in tailplane stall. Typically, this phenomenon occurs when lowering the flaps during final approach while operating in or recently departing from icing conditions. Ice formation on the tailplane leading edge can reduce tailplane angle-of-attack range and cause flow separation resulting in a significant reduction or complete loss of aircraft pitch control. In 1993, the Federal Aviation Authority (FAA) and NASA embarked upon a four-year research program to address the problem of tailplane stall and to quantify the effect of tailplane ice accretion on aircraft performance and handling characteristics. The goals of this program, which was completed in March 1998, were to collect aerodynamic data for an aircraft tail with and without ice contamination and to develop analytical methods for predicting the effects of tailplane ice contamination. Extensive dry air and icing tunnel tests which resulted in a database of the aerodynamic effects associated with tailplane ice contamination. Although the FAA/NASA tailplane icing program generated some answers regarding ice-contaminated-tailplane stall (ICTS) phenomena, NASA researchers have found many open questions that warrant further investigation into ICTS. In addition, several aircraft manufacturers have expressed interest in a second research program to expand the database to other tail configurations and to develop experimental and computational methodologies for evaluating the ICTS phenomenon. In 1998, the icing branch at NASA Lewis initiated a second

  17. Possible Role of Horizontal Gene Transfer in the Colonization of Sea Ice by Algae

    PubMed Central

    Raymond, James A.; Kim, Hak Jun

    2012-01-01

    Diatoms and other algae not only survive, but thrive in sea ice. Among sea ice diatoms, all species examined so far produce ice-binding proteins (IBPs), whereas no such proteins are found in non-ice-associated diatoms, which strongly suggests that IBPs are essential for survival in ice. The restricted occurrence also raises the question of how the IBP genes were acquired. Proteins with similar sequences and ice-binding activities are produced by ice-associated bacteria, and so it has previously been speculated that the genes were acquired by horizontal transfer (HGT) from bacteria. Here we report several new IBP sequences from three types of ice algae, which together with previously determined sequences reveal a phylogeny that is completely incongruent with algal phylogeny, and that can be most easily explained by HGT. HGT is also supported by the finding that the closest matches to the algal IBP genes are all bacterial genes and that the algal IBP genes lack introns. We also describe a highly freeze-tolerant bacterium from the bottom layer of Antarctic sea ice that produces an IBP with 47% amino acid identity to a diatom IBP from the same layer, demonstrating at least an opportunity for gene transfer. Together, these results suggest that the success of diatoms and other algae in sea ice can be at least partly attributed to their acquisition of prokaryotic IBP genes. PMID:22567121

  18. Modelled and measured dynamics of viruses in Arctic winter sea-ice brines.

    PubMed

    Wells, Llyd E; Deming, Jody W

    2006-06-01

    We describe a model based on diffusion theory and the temperature-dependent mechanism of brine concentration in sea ice to argue that, if viruses partition with bacteria into sea-ice brine inclusions, contact rates between the two can be higher in winter sea ice than in seawater, increasing the probability of infection and possible virus production. To examine this hypothesis, we determined viral and bacterial concentrations in select winter sea-ice horizons using epifluorescence microscopy. Viral concentrations ranged from 1.6 to 82 x 10(6) ml(-1) of brine volume of the ice, with highest values in brines from coldest (-24 to -31 degrees C) ice horizons. Calculated virus-bacteria contact rates in underlying -1 degrees C seawater were similar to those in brines of -11 degrees C ice but up to 600 times lower than those in ice brines at or below -24 degrees C. We then incubated native bacterial and viral assemblages from winter sea ice for 8 days in brine at a temperature (-12 degrees C) and salinity ( approximately 160 psu) near expected in situ values, monitoring their concentrations microscopically. While different cores yielded different results, consistent with known spatial heterogeneity in sea ice, these experiments provided unambiguous evidence for viral persistence and production, as well as for bacterial growth, in -12 degrees C brine.

  19. Commercial aviation icing research requirements

    NASA Technical Reports Server (NTRS)

    Koegeboehn, L. P.

    1981-01-01

    A short range and long range icing research program was proposed. A survey was made to various industry and goverment agencies to obtain their views of needs for commercial aviation ice protection. Through these responsed, other additional data, and Douglas Aircraft icing expertise; an assessment of the state-of-the-art of aircraft icing data and ice protection systems was made. The information was then used to formulate the icing research programs.

  20. Endogenous and exogenous ice-nucleating agents constrain supercooling in the hatchling painted turtle.

    PubMed

    Costanzo, Jon P; Baker, Patrick J; Dinkelacker, Stephen A; Lee, Richard E

    2003-02-01

    Hatchlings of the painted turtle (Chrysemys picta) commonly hibernate in their shallow, natal nests. Survival at temperatures below the limit of freeze tolerance (approximately -4 degrees C) apparently depends on their ability to remain supercooled, and, whereas previous studies have reported that supercooling capacity improves markedly with cold acclimation, the mechanistic basis for this change is incompletely understood. We report that the crystallization temperature (T(c)) of recently hatched (summer) turtles acclimated to 22 degrees C and reared on a substratum of vermiculite or nesting soil was approximately 5 degrees C higher than the T(c) determined for turtles acclimated to 4 degrees C and tested in winter. This increase in supercooling capacity coincided with elimination of substratum (and, in fewer cases, eggshell) that the hatchlings had ingested; however, this association was not necessarily causal because turtles reared on a paper-covered substratum did not ingest exogenous matter but nevertheless showed a similar increase in supercooling capacity. Our results for turtles reared on paper revealed that seasonal development of supercooling capacity fundamentally requires elimination of ice-nucleating agents (INA) of endogenous origin: summer turtles, but not winter turtles, produced feces (perhaps derived from residual yolk) that expressed ice-nucleating activity. Ingestion of vermiculite or eggshell, which had modest ice-nucleating activity, had no effect on the T(c), whereas ingestion of nesting soil, which contained two classes of potent INA, markedly reduced the supercooling capacity of summer turtles. This effect persisted long after the turtles had purged their guts of soil particles, because the T(c) of winter turtles reared on nesting soil (mean +/- S.E.M.=-11.6+/-1.4 degrees C) was approximately 6 degrees C higher than the T(c) of winter turtles reared on vermiculite or paper. Experiments in which winter turtles were fed INA commonly found in

  1. Overview of LIMEX'87 ice observations

    NASA Technical Reports Server (NTRS)

    Carsey, Frank D.; Holt, Benjamin; Argus, Susan A. Digby; Collins, Michael J.; Livingstone, Charles E.

    1989-01-01

    Ice observations, results, and conclusions are summarized for the March 1987 Labrador Ice Margin Experiment (LIMEX'87), an international oceanographic study conducted in the pack ice of the Grand Banks area off the coast of Newfoundland. Included are the ice extent, floe size and thickness, ice kinematics and rheology, ice microwave properties, oceanic properties under the ice, and penetration of swell into the ice.

  2. Artic ice and drilling structures

    SciTech Connect

    Sodhl, D.S.

    1985-04-01

    The sea ice in the southern Beaufort Sea is examined and subdivided into three zones: the fast ice zone, the seasonal pack-ice zone, an the polar pack ice zone. Each zone requires its own type of system. Existing floating drilling systems include ice-strengthened drill ships, conical drilling systems, and floating ice platforms in deep-water land-fast ice. The development of hydrocarbon resources in the Arctic presents great challenges to engineers, since the structures are required to operate safely under various conditions. Significant progress has yet to be made in understanding the behavior of ice.

  3. Spectroscopic signature for ferroelectric ice

    NASA Astrophysics Data System (ADS)

    Wójcik, Marek J.; Gług, Maciej; Boczar, Marek; Boda, Łukasz

    2014-09-01

    Various forms of ice exist within our galaxy. Particularly intriguing type of ice - ‘ferroelectric ice' was discovered experimentally and is stable in temperatures below 72 K. This form of ice can generate enormous electric fields and can play an important role in planetary formation. In this letter we present Car-Parrinello simulation of infrared spectra of ferroelectric ice and compare them with spectra of hexagonal ice. Librational region of the spectra can be treated as spectroscopic signature of ice XI and can be of help to identify ferroelectric ice in the Universe.

  4. Larsen B Ice Shelf

    Atmospheric Science Data Center

    2013-04-16

    ... ice shelf and the rough crevasses of glaciers appear orange. In contrast to the spectral composite, which provides information on ... surfaces appear brighter on their illuminated faces, the orange color in the multi-angle composite suggests a macroscopically rough ice ...

  5. Turning into Ice

    ERIC Educational Resources Information Center

    Pietsch, Renée B.; Hanlon, Regina; Bohland, Cynthia; Schmale, David G., III

    2016-01-01

    This article describes an interdisciplinary unit in which students explore biological "ice nucleation"--by particles that cause water to freeze at temperatures above -38°C--through the lens of the microbial ice nucleator "Pseudomonas syringae." Such This activity, which aligns with the "Next Generation Science…

  6. Making an Ice Core.

    ERIC Educational Resources Information Center

    Kopaska-Merkel, David C.

    1995-01-01

    Explains an activity in which students construct a simulated ice core. Materials required include only a freezer, food coloring, a bottle, and water. This hands-on exercise demonstrates how a glacier is formed, how ice cores are studied, and the nature of precision and accuracy in measurement. Suitable for grades three through eight. (Author/PVD)

  7. Ice Core Investigations

    ERIC Educational Resources Information Center

    Krim, Jessica; Brody, Michael

    2008-01-01

    What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air…

  8. Ross Ice Shelf

    Atmospheric Science Data Center

    2013-04-16

    ... to hatch their young this year due to a combination of huge icebergs grounded near Ross Island and an unprecedented amount of sea ice in the Ross Sea. The grounded icebergs and sea ice have increased the distance between the penguins' feeding ...

  9. Academic Airframe Icing Perspective

    NASA Technical Reports Server (NTRS)

    Bragg, Mike; Rothmayer, Alric; Thompson, David

    2009-01-01

    2-D ice accretion and aerodynamics reasonably well understood for engineering applications To significantly improve our current capabilities we need to understand 3-D: a) Important ice accretion physics and modeling not well understood in 3-D; and b) Aerodynamics unsteady and 3-D especially near stall. Larger systems issues important and require multidisciplinary team approach

  10. Snow and Ice.

    ERIC Educational Resources Information Center

    Minneapolis Independent School District 275, Minn.

    This experimental edition provides a number of activities useful for investigating snow and ice with elementary school children. Commencing with games with ice cubes, the activities lead through studies of snowflakes, snowdrifts, effects of wind and obstacles on the shape and formation of drifts, to a study of animals living under snow. The…

  11. Fire beneath the ice

    SciTech Connect

    Monastersky, R.

    1993-02-13

    A volcano discovered six years ago by researchers Blankenship and Bell under Antarctica poses questions about a potential climatic catastrophe. The researchers claim that the volcano is still active, erupting occasionally and growing. A circular depression on the surface of the ice sheet has ice flowing into it and is used to provide a portrait of the heat source. The volcano is on a critical transition zone within West Antarctica with fast flowing ice streams directly downhill. Work by Blankenship shows that a soft layer of water-logged sediments called till provide the lubricating layer on the underside of the ice streams. Volcanos may provide the source of this till. The ice streams buffer the thick interior ice from the ocean and no one know what will happen if the ice streams continue to shorten. These researchers believe their results indicate that the stability of West Antarctica ultimately depends less on the current climate than on the location of heat and sediments under the ice and the legacy of past climatic changes.

  12. Ice Core Investigations

    ERIC Educational Resources Information Center

    Krim, Jessica; Brody, Michael

    2008-01-01

    What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air…

  13. Rheology of glacier ice

    NASA Technical Reports Server (NTRS)

    Jezek, K. C.; Alley, R. B.; Thomas, R. H.

    1985-01-01

    A new method for calculating the stress field in bounded ice shelves is used to compare strain rate and deviatoric stress on the Ross Ice Shelf, Antarctica. The analysis shows that strain rate (per second) increases as the third power of deviatoric stress (in newtons/sq meter), with a constant of proportionality equal to 2.3 x 10 to the -25th.

  14. Rheology of glacier ice

    NASA Technical Reports Server (NTRS)

    Jezek, K. C.; Alley, R. B.; Thomas, R. H.

    1985-01-01

    A new method for calculating the stress field in bounded ice shelves is used to compare strain rate and deviatoric stress on the Ross Ice Shelf, Antarctica. The analysis shows that strain rate (per second) increases as the third power of deviatoric stress (in newtons/sq meter), with a constant of proportionality equal to 2.3 x 10 to the -25th.

  15. Making an Ice Core.

    ERIC Educational Resources Information Center

    Kopaska-Merkel, David C.

    1995-01-01

    Explains an activity in which students construct a simulated ice core. Materials required include only a freezer, food coloring, a bottle, and water. This hands-on exercise demonstrates how a glacier is formed, how ice cores are studied, and the nature of precision and accuracy in measurement. Suitable for grades three through eight. (Author/PVD)

  16. Ice forming experiment

    NASA Technical Reports Server (NTRS)

    Vali, G.

    1982-01-01

    A low gravity experiment to assess the effect of the presence of supercooled cloud droplets on the diffusional growth rate of ice crystals is described. The theoretical work and the feasibility studies are summarized. The nucleation of ice crystals in supercooled clouds is also discussed.

  17. Turning into Ice

    ERIC Educational Resources Information Center

    Pietsch, Renée B.; Hanlon, Regina; Bohland, Cynthia; Schmale, David G., III

    2016-01-01

    This article describes an interdisciplinary unit in which students explore biological "ice nucleation"--by particles that cause water to freeze at temperatures above -38°C--through the lens of the microbial ice nucleator "Pseudomonas syringae." Such This activity, which aligns with the "Next Generation Science…

  18. Rotating ice blocks

    NASA Astrophysics Data System (ADS)

    Dorbolo, Stephane; Adami, Nicolas; Grasp Team

    2014-11-01

    The motion of ice discs released at the surface of a thermalized bath was investigated. As observed in some rare events in the Nature, the discs start spinning spontaneously. The motor of this motion is the cooling of the water close to the ice disc. As the density of water is maximum at 4°C, a downwards flow is generated from the surface of the ice block to the bottom. This flow generates the rotation of the disc. The speed of rotation depends on the mass of the ice disc and on the temperature of the bath. A model has been constructed to study the influence of the temperature of the bath. Finally, ice discs were put on a metallic plate. Again, a spontaneous rotation was observed. FNRS is thanked for financial support.

  19. Polarimetric road ice detection

    NASA Astrophysics Data System (ADS)

    Drummond, Krista

    This thesis investigated the science behind polarimetric road ice detection systems. Laboratory Mueller matrix measurements of a simulated road under differing surface conditions were collected searching for a discriminatory polarization property. These Mueller matrices were decomposed into depolarization, diattenuation, and retardance. Individual sample surface polarization properties were then calculated from these three unique matrices and compared. Specular and off-specular reflection responses of each sample were collected. Four polarization properties stood out for having high separation between dry and iced measurements: Depolarization Index, Linear Diattenuation, Linear Polarizance, and Linear Retardance. Through our investigation polarimetric ice detection is possible. Continued research of the polarization properties of road ice can result in the development of a road ice detection system. Proposed deployment methods of such a system have been outlined following the analysis of the data collected in this experiment.

  20. Quantum Ice : Experimental Signatures

    NASA Astrophysics Data System (ADS)

    Shannon, Nic; Benton, Owen; Sikora, Olga; Penc, Karlo; McClarty, Paul; Pollmann, Frank; Moessner, Roderich; Fulde, Peter

    2012-02-01

    ``Quantum Spin Ice'' materials have attracted considerable attention as three-dimensional examples of quantum spin liquids. Recently, we have used zero-temperature Quantum Monte Carlo simulation to explore one possible scenario for these materials, confirming the possibility of a ``quantum ice'' state driven by quantum tunnelling between an extensive number of different spin-ice configurations [1]. Here we address the simple question : what would such a quantum ice look like in experiment ? We focus in particular on the fate of ``pinch point'' singularities seen in neutron scattering experiments on spin ice materials, showing how these are suppressed and ultimately eliminated as the system is cooled to its ground state [1,2]. [4pt] [1] N. Shannon et al., arXiv:1105.4196[0pt] [2] O. Benton et al., in preparation.

  1. Coating Reduces Ice Adhesion

    NASA Technical Reports Server (NTRS)

    Smith, Trent; Prince, Michael; DwWeese, Charles; Curtis, Leslie

    2008-01-01

    The Shuttle Ice Liberation Coating (SILC) has been developed to reduce the adhesion of ice to surfaces on the space shuttle. SILC, when coated on a surface (foam, metal, epoxy primer, polymer surfaces), will reduce the adhesion of ice by as much as 90 percent as compared to the corresponding uncoated surface. This innovation is a durable coating that can withstand several cycles of ice growth and removal without loss of anti-adhesion properties. SILC is made of a binder composed of varying weight percents of siloxane(s), ethyl alcohol, ethyl sulfate, isopropyl alcohol, and of fine-particle polytetrafluoroethylene (PTFE). The combination of these components produces a coating with significantly improved weathering characteristics over the siloxane system alone. In some cases, the coating will delay ice formation and can reduce the amount of ice formed. SILC is not an ice prevention coating, but the very high water contact angle (greater than 140 ) causes water to readily run off the surface. This coating was designed for use at temperatures near -170 F (-112 C). Ice adhesion tests performed at temperatures from -170 to 20 F (-112 to -7 C) show that SILC is a very effective ice release coating. SILC can be left as applied (opaque) or buffed off until the surface appears clear. Energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS) data show that the coating is still present after buffing to transparency. This means SILC can be used to prevent ice adhesion even when coating windows or other objects, or items that require transmission of optical light. Car windshields are kept cleaner and SILC effectively mitigates rain and snow under driving conditions.

  2. Life Beneath Glacial Ice - Earth(!) Mars(?) Europa(?)

    NASA Technical Reports Server (NTRS)

    Allen, Carlton C.; Grasby, Stephen E.; Longazo, Teresa G.; Lisle, John T.; Beauchamp, Benoit

    2002-01-01

    We are investigating a set of cold springs that deposit sulfur and carbonate minerals on the surface of a Canadian arctic glacier. The spring waters and mineral deposits contain microorganisms, as well as clear evidence that biological processes mediate subglacial chemistry, mineralogy, and isotope fractionation . The formation of native sulphur and associated deposits are related to bacterially mediated reduction and oxidation of sulphur below the glacier. A non-volcanic, topography driven geothermal system, harboring a microbiological community, operates in an extremely cold environment and discharges through solid ice. Microbial life can thus exist in isolated geothermal refuges despite long-term subfreezing surface conditions. Earth history includes several periods of essentially total glaciation. lee in the near subsurface of Mars may have discharged liquid water in the recent past Cracks in the ice crust of Europa have apparently allowed the release of water to the surface. Chemolithotrophic bacteria, such as those in the Canadian springs, could have survived beneath the ice of "Snowball Earth", and life forms with similar characteristics might exist beneath the ice of Mars or Europa. Discharges of water from such refuges may have brought to the surface living microbes, as well as longlasting chemical, mineralogical, and isotopic indications of subsurface life.

  3. Tensile properties of impact ices

    NASA Technical Reports Server (NTRS)

    Chu, M. L.; Scavuzzo, R. J.; Kellackey, C. J.

    1992-01-01

    A special test apparatus was developed to measure the tensile strength of impact ices perpendicular to the direction of growth. The apparatus consists of a split tube carefully machined to minimize the effect of the joint on impact ice strength. The tube is supported in the wind tunnel by two carefully aligned bearings. During accretion the tube is turned slowly in the icing cloud to form a uniform coating of ice on the split tube specimen. The two halves of the split tube are secured firmly by a longitudinal bolt to prevent relative motion between the two halves during ice accretion and handling. Tensile test strength results for a variety of icing conditions were obtained. Both glaze and rime ice conditions were investigated. In general, the tensile strength of impact ice was significantly less than refrigerator ice. Based on the limited data taken, the median strength of rime ice was less than glaze ice. However, the mean values were similar.

  4. Proton ordering in cubic ice and hexagonal ice; a potential new ice phase--XIc.

    PubMed

    Raza, Zamaan; Alfè, Dario; Salzmann, Christoph G; Klimeš, Jiří; Michaelides, Angelos; Slater, Ben

    2011-11-28

    Ordinary water ice forms under ambient conditions and has two polytypes, hexagonal ice (Ih) and cubic ice (Ic). From a careful comparison of proton ordering arrangements in Ih and Ic using periodic density functional theory (DFT) and diffusion Monte Carlo (DMC) approaches, we find that the most stable arrangement of water molecules in cubic ice is isoenergetic with that of the proton ordered form of hexagonal ice (known as ice XI). We denote this potential new polytype of ice XI as XIc and discuss a possible route for preparing ice XIc.

  5. Stacking disorder in ice I.

    PubMed

    Malkin, Tamsin L; Murray, Benjamin J; Salzmann, Christoph G; Molinero, Valeria; Pickering, Steven J; Whale, Thomas F

    2015-01-07

    Traditionally, ice I was considered to exist in two well-defined crystalline forms at ambient pressure: stable hexagonal ice (ice Ih) and metastable cubic ice (ice Ic). However, it is becoming increasingly evident that what has been called cubic ice in the past does not have a structure consistent with the cubic crystal system. Instead, it is a stacking-disordered material containing cubic sequences interlaced with hexagonal sequences, which is termed stacking-disordered ice (ice Isd). In this article, we summarise previous work on ice with stacking disorder including ice that was called cubic ice in the past. We also present new experimental data which shows that ice which crystallises after heterogeneous nucleation in water droplets containing solid inclusions also contains stacking disorder even at freezing temperatures of around -15 °C. This supports the results from molecular simulations, that the structure of ice that crystallises initially from supercooled water is always stacking-disordered and that this metastable ice can transform to the stable hexagonal phase subject to the kinetics of recrystallization. We also show that stacking disorder in ice which forms from water droplets is quantitatively distinct from ice made via other routes. The emerging picture of ice I is that of a very complex material which frequently contains stacking disorder and this stacking disorder can vary in complexity depending on the route of formation and thermal history.

  6. A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: a comparison of 17 ice nucleation measurement techniques

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Augustin-Bauditz, S.; Bingemer, H.; Budke, C.; Curtius, J.; Danielczok, A.; Diehl, K.; Dreischmeier, K.; Ebert, M.; Frank, F.; Hoffmann, N.; Kandler, K.; Kiselev, A.; Koop, T.; Leisner, T.; Möhler, O.; Nillius, B.; Peckhaus, A.; Rose, D.; Weinbruch, S.; Wex, H.; Boose, Y.; DeMott, P. J.; Hader, J. D.; Hill, T. C. J.; Kanji, Z. A.; Kulkarni, G.; Levin, E. J. T.; McCluskey, C. S.; Murakami, M.; Murray, B. J.; Niedermeier, D.; Petters, M. D.; O'Sullivan, D.; Saito, A.; Schill, G. P.; Tajiri, T.; Tolbert, M. A.; Welti, A.; Whale, T. F.; Wright, T. P.; Yamashita, K.

    2015-03-01

    Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice-nucleating particles. However, an intercomparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental parameters associated with these techniques. Within the framework of INUIT (Ice Nuclei Research Unit), we distributed an illite-rich sample (illite NX) as a representative surrogate for atmospheric mineral dust particles to investigators to perform immersion freezing experiments using different IN measurement methods and to obtain IN data as a function of particle concentration, temperature (T), cooling rate and nucleation time. A total of 17 measurement methods were involved in the data intercomparison. Experiments with seven instruments started with the test sample pre-suspended in water before cooling, while 10 other instruments employed water vapor condensation onto dry-dispersed particles followed by immersion freezing. The resulting comprehensive immersion freezing data set was evaluated using the ice nucleation active surface-site density, ns, to develop a representative ns(T) spectrum that spans a wide temperature range (-37 °C < T < -11 °C) and covers 9 orders of magnitude in ns. In general, the 17 immersion freezing measurement techniques deviate, within a range of about 8 °C in terms of temperature, by 3 orders of magnitude with respect to ns. In addition, we show evidence that the immersion freezing efficiency expressed in ns of illite NX particles is relatively

  7. A comprehensive laboratory study on the immersion freezing behavior of illite NX particles. A comparison of 17 ice nucleation measurement techniques

    DOE PAGES

    Hiranuma, Naruki; Augustin-Bauditz, Stefanie; Bingemer, Heinz; ...

    2015-03-06

    Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice-nucleating particles. However, an intercomparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental parameters associated with these techniques.more » Within the framework of INUIT (Ice Nuclei Research Unit), we distributed an illite-rich sample (illite NX) as a representative surrogate for atmospheric mineral dust particles to investigators to perform immersion freezing experiments using different IN measurement methods and to obtain IN data as a function of particle concentration, temperature (T), cooling rate and nucleation time. A total of 17 measurement methods were involved in the data intercomparison. Experiments with seven instruments started with the test sample pre-suspended in water before cooling, while 10 other instruments employed water vapor condensation onto dry-dispersed particles followed by immersion freezing. The resulting comprehensive immersion freezing data set was evaluated using the ice nucleation active surface-site density, ns, to develop a representative ns(T) spectrum that spans a wide temperature range (-37 °C < T < -11 °C) and covers 9 orders of magnitude in ns. In general, the 17 immersion freezing measurement techniques deviate, within a range of about 8 °C in terms of temperature, by 3 orders of magnitude with respect to ns. In addition, we show evidence that the immersion freezing efficiency expressed in ns of illite NX particles is relatively

  8. Icing Cloud Calibration of the NASA Glenn Icing Research Tunnel

    NASA Technical Reports Server (NTRS)

    Ide, Robert F.; Oldenburg, John R.

    2001-01-01

    The icing research tunnel at the NASA Glenn Research Center underwent a major rehabilitation in 1999, necessitating recalibration of the icing clouds. This report describes the methods used in the recalibration, including the procedure used to establish a uniform icing cloud and the use of a standard icing blade technique for measurement of liquid water content. The instruments and methods used to perform the droplet size calibration are also described. The liquid water content/droplet size operating envelopes of the icing tunnel are shown for a range of airspeeds and compared to the FAA icing certification criteria. The capabilities of the IRT to produce large droplet icing clouds is also detailed.

  9. Ice sheets and nitrogen.

    PubMed

    Wolff, Eric W

    2013-07-05

    Snow and ice play their most important role in the nitrogen cycle as a barrier to land-atmosphere and ocean-atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately 260 Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades. Nitrous oxide concentrations have risen about 20 per cent in the last 200 years and are now almost certainly higher than at any time in the last 800 000 years. Nitrate concentrations recorded in Greenland ice rose by a factor of 2-3, particularly between the 1950s and 1980s, reflecting a major change in NOx emissions reaching the background atmosphere. Increases in ice cores drilled at lower latitudes can be used to validate or constrain regional emission inventories. Background ammonium concentrations in Greenland ice show no significant recent trend, although the record is very noisy, being dominated by spikes of input from biomass burning events. Neither nitrate nor ammonium shows significant recent trends in Antarctica, although their natural variations are of biogeochemical and atmospheric chemical interest. Finally, it has been found that photolysis of nitrate in the snowpack leads to significant re-emissions of NOx that can strongly impact the regional atmosphere in snow-covered areas.

  10. Micromechanics of ice friction

    NASA Astrophysics Data System (ADS)

    Sammonds, P. R.; Bailey, E.; Lishman, B.; Scourfield, S.

    2015-12-01

    Frictional mechanics are controlled by the ice micro-structure - surface asperities and flaws - but also the ice fabric and permeability network structure of the contacting blocks. Ice properties are dependent upon the temperature of the bulk ice, on the normal stress and on the sliding velocity and acceleration. This means the shear stress required for sliding is likewise dependent on sliding velocity, acceleration, and temperature. We aim to describe the micro-physics of the contacting surface. We review micro-mechanical models of friction: the elastic and ductile deformation of asperities under normal loads and their shear failure by ductile flow, brittle fracture, or melting and hydrodynamic lubrication. Combinations of these give a total of six rheological models of friction. We present experimental results in ice mechanics and physics from laboratory experiments to understand the mechanical models. We then examine the scaling relations of the slip of ice, to examine how the micro-mechanics of ice friction can be captured simple reduced-parameter models, describing the mechanical state and slip rate of the floes. We aim to capture key elements that they may be incorporated into mid and ocean-basin scale modelling.

  11. Ice sheets and nitrogen

    PubMed Central

    Wolff, Eric W.

    2013-01-01

    Snow and ice play their most important role in the nitrogen cycle as a barrier to land–atmosphere and ocean–atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately 260 Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades. Nitrous oxide concentrations have risen about 20 per cent in the last 200 years and are now almost certainly higher than at any time in the last 800 000 years. Nitrate concentrations recorded in Greenland ice rose by a factor of 2–3, particularly between the 1950s and 1980s, reflecting a major change in NOx emissions reaching the background atmosphere. Increases in ice cores drilled at lower latitudes can be used to validate or constrain regional emission inventories. Background ammonium concentrations in Greenland ice show no significant recent trend, although the record is very noisy, being dominated by spikes of input from biomass burning events. Neither nitrate nor ammonium shows significant recent trends in Antarctica, although their natural variations are of biogeochemical and atmospheric chemical interest. Finally, it has been found that photolysis of nitrate in the snowpack leads to significant re-emissions of NOx that can strongly impact the regional atmosphere in snow-covered areas. PMID:23713125

  12. Skylab floating ice experiment

    NASA Technical Reports Server (NTRS)

    Campbell, W. J. (Principal Investigator); Ramseier, R. O.; Weaver, R. J.; Weeks, W. F.

    1975-01-01

    The author has identified the following significant results. Coupling of the aircraft data with the ground truth observations proved to be highly successful with interesting results being obtained with IR and SLAR passive microwave techniques, and standard photography. Of particular interest were the results of the PMIS system which operated at 10.69 GHz with both vertical and horizontal polarizations. This was the first time that dual polarized images were obtained from floating ice. In both sea and lake ice, it was possible to distinguish a wide variety of thin ice types because of their large differences in brightness temperatures. It was found that the higher brightness temperature was invariably obtained in the vertically polarized mode, and as the age of the ice increases the brightness temperature increases in both polarizations. Associated with this change in age, the difference in temperature was observed as the different polarizations decreased. It appears that the horizontally polarized data is the most sensitive to variations in ice type for both fresh water and sea ice. The study also showed the great amount of information on ice surface roughness and deformation patterns that can be obtained from X-band SLAR observations.

  13. Pyroelectricity of water ice.

    PubMed

    Wang, Hanfu; Bell, Richard C; Iedema, Martin J; Schenter, Gregory K; Wu, Kai; Cowin, James P

    2008-05-22

    Water ice usually is thought to have zero pyroelectricity by symmetry. However, biasing it with ions breaks the symmetry because of the induced partial dipole alignment. This unmasks a large pyroelectricity. Ions were soft-landed upon 1 mum films of water ice at temperatures greater than 160 K. When cooled below 140-150 K, the dipole alignment locks in. Work function measurements of these films then show high and reversible pyroelectric activity from 30 to 150 K. For an initial approximately 10 V induced by the deposited ions at 160 K, the observed bias below 150 K varies approximately as 10 Vx(T/150 K)2. This implies that water has pyroelectric coefficients as large as that of many commercial pyroelectrics, such as lead zirconate titanate (PZT). The pyroelectricity of water ice, not previously reported, is in reasonable agreement with that predicted using harmonic analysis of a model system of SPC ice. The pyroelectricity is observed in crystalline and compact amorphous ice, deuterated or not. This implies that for water ice between 0 and 150 K (such as astrophysical ices), temperature changes can induce strong electric fields (approximately 10 MV/m) that can influence their chemistry, ion trajectories, or binding.

  14. Water Ice on Pluto

    NASA Image and Video Library

    2015-10-16

    The Ralph instrument on NASA's New Horizons spacecraft detected water ice on Pluto's surface, picking up on the ice's near-infrared spectral characteristics. (See featured image from Oct. 8, 2015.) The middle panel shows a region west of Pluto's "heart" feature -- which the mission team calls Tombaugh Regio -- about 280 miles (450 kilometers) across. It combines visible imagery from Ralph's Multispectral Visible Imaging Camera (MVIC) with infrared spectroscopy from the Linear Etalon Imaging Spectral Array (LEISA). Areas with the strongest water ice spectral signature are highlighted in blue. Major outcrops of water ice occur in regions informally called Viking Terra, along Virgil Fossa west of Elliot crater, and in Baré Montes. Numerous smaller outcrops are associated with impact craters and valleys between mountains. In the lower left panel, LEISA spectra are shown for two regions indicated by cyan and magenta boxes. The white curve is a water ice model spectrum, showing similar features to the cyan spectrum. The magenta spectrum is dominated by methane ice absorptions. The lower right panel shows an MVIC enhanced color view of the region in the white box, with MVIC's blue, red and near-infrared filters displayed in blue, green and red channels, respectively. The regions showing the strongest water ice signature are associated with terrains that are actually a lighter shade of red. http://photojournal.jpl.nasa.gov/catalog/PIA20030

  15. High Speed Ice Friction

    NASA Astrophysics Data System (ADS)

    Seymour-Pierce, Alexandra; Sammonds, Peter; Lishman, Ben

    2014-05-01

    Many different tribological experiments have been run to determine the frictional behaviour of ice at high speeds, ostensibly with the intention of applying results to everyday fields such as winter tyres and sports. However, experiments have only been conducted up to linear speeds of several metres a second, with few additional subject specific studies reaching speeds comparable to these applications. Experiments were conducted in the cold rooms of the Rock and Ice Physics Laboratory, UCL, on a custom built rotational tribometer based on previous literature designs. Preliminary results from experiments run at 2m/s for ice temperatures of 271 and 263K indicate that colder ice has a higher coefficient of friction, in accordance with the literature. These results will be presented, along with data from further experiments conducted at temperatures between 259-273K (in order to cover a wide range of the temperature dependent behaviour of ice) and speeds of 2-15m/s to produce a temperature-velocity-friction map for ice. The effect of temperature, speed and slider geometry on the deformation of ice will also be investigated. These speeds are approaching those exhibited by sports such as the luge (where athletes slide downhill on an icy track), placing the tribological work in context.

  16. The influence of organic-containing soil dust on ice nucleation and cloud properties

    NASA Astrophysics Data System (ADS)

    Hummel, Matthias; Grini, Alf; Berntsen, Terje K.; Ekman, Annica

    2017-04-01

    Natural mineral dust from desert regions is known to be the most important contributor to atmospheric ice-nucleating particles (INP) which induce heterogeneous ice nucleation in mixed-phase clouds. Its ability to nucleate ice effectively is shown by various laboratory (Hoose and Möhler 2012) and field results (DeMott et al. 2015) and its abundance in ice crystal residuals has also been shown (Cziczo et al. 2013). Thus it is an important player when representing mixed-phase clouds in climate models. MODIS satellite data indicate that 1 /4 of the global dust emission originates from semi-arid areas rather than from arid deserts (Ginoux et al. 2012). Here, organic components can mix with minerals within the soil and get into the atmosphere. These so-called 'soil dust' particles are ice-nucleating active at high sub-zero temperatures, i.e. at higher temperatures than pure desert dust (Steinke et al. 2016). In this study, soil dust is incorporated into the Norwegian Earth System Model (NorESM, Bentsen et al. 2013) and applied to a modified ice nucleation parameterization (Steinke et al. 2016). Its influence on the cloud ice phase is evaluated by comparing a control run, where only pure desert dust is considered, and a sensitivity experiment, where a fraction of the dust emissions are classified as soil dust. Both simulations are nudged to ERA-interim meteorology and they have the same loading of dust emissions. NorESM gives a lower annual soil dust emission flux compared to Ginoux et al. (2012), but the desert dust flux is similar to the MODIS-retrieved data. Although soil dust concentrations are much lower than desert dust, the NorESM simulations indicate that the annual INP concentrations from soil dust are on average lower by a just a factor of 4 than INP concentrations from pure desert dust. The highest soil dust INP concentrations occur at a lower height than for desert dust, i.e at warmer temperatures inside mixed-phase clouds. Furthermore, soil dust INP

  17. Cyclic steps on ice

    NASA Astrophysics Data System (ADS)

    Yokokawa, M.; Izumi, N.; Naito, K.; Parker, G.; Yamada, T.; Greve, R.

    2016-05-01

    Boundary waves often form at the interface between ice and fluid flowing adjacent to it, such as ripples under river ice covers, and steps on the bed of supraglacial meltwater channels. They may also be formed by wind, such as the megadunes on the Antarctic ice sheet. Spiral troughs on the polar ice caps of Mars have been interpreted to be cyclic steps formed by katabatic wind blowing over ice. Cyclic steps are relatives of upstream-migrating antidunes. Cyclic step formation on ice is not only a mechanical but also a thermodynamic process. There have been very few studies on the formation of either cyclic steps or upstream-migrating antidunes on ice. In this study, we performed flume experiments to reproduce cyclic steps on ice by flowing water, and found that trains of steps form when the Froude number is larger than unity. The features of those steps allow them to be identified as ice-bed analogs of cyclic steps in alluvial and bedrock rivers. We performed a linear stability analysis and obtained a physical explanation of the formation of upstream-migrating antidunes, i.e., precursors of cyclic steps. We compared the results of experiments with the predictions of the analysis and found the observed steps fall in the range where the analysis predicts interfacial instability. We also found that short antidune-like undulations formed as a precursor to the appearance of well-defined steps. This fact suggests that such antidune-like undulations correspond to the instability predicted by the analysis and are precursors of cyclic steps.

  18. The seeding of ice algal blooms in Arctic pack ice: The multiyear ice seed repository hypothesis

    NASA Astrophysics Data System (ADS)

    Olsen, Lasse M.; Laney, Samuel R.; Duarte, Pedro; Kauko, Hanna M.; Fernández-Méndez, Mar; Mundy, Christopher J.; Rösel, Anja; Meyer, Amelie; Itkin, Polona; Cohen, Lana; Peeken, Ilka; Tatarek, Agnieszka; Róźańska-Pluta, Magdalena; Wiktor, Józef; Taskjelle, Torbjørn; Pavlov, Alexey K.; Hudson, Stephen R.; Granskog, Mats A.; Hop, Haakon; Assmy, Philipp

    2017-07-01

    During the Norwegian young sea ICE expedition (N-ICE2015) from January to June 2015 the pack ice in the Arctic Ocean north of Svalbard was studied during four drifts between 83° and 80°N. This pack ice consisted of a mix of second year, first year, and young ice. The physical properties and ice algal community composition was investigated in the three different ice types during the winter-spring-summer transition. Our results indicate that algae remaining in sea ice that survived the summer melt season are subsequently trapped in the upper layers of the ice column during winter and may function as an algal seed repository. Once the connectivity in the entire ice column is established, as a result of temperature-driven increase in ice porosity during spring, algae in the upper parts of the ice are able to migrate toward the bottom and initiate the ice algal spring bloom. Furthermore, this algal repository might seed the bloom in younger ice formed in adjacent leads. This mechanism was studied in detail for the dominant ice diatom Nitzschia frigida. The proposed seeding mechanism may be compromised due to the disappearance of older ice in the anticipated regime shift toward a seasonally ice-free Arctic Ocean.

  19. Frost flowers on young Arctic sea ice: The climatic, chemical, and microbial significance of an emerging ice type

    NASA Astrophysics Data System (ADS)

    Barber, D. G.; Ehn, J. K.; Pućko, M.; Rysgaard, S.; Deming, J. W.; Bowman, J. S.; Papakyriakou, T.; Galley, R. J.; Søgaard, D. H.

    2014-10-01

    Ongoing changes in Arctic sea ice are increasing the spatial and temporal range of young sea ice types over which frost flowers can occur, yet the significance of frost flowers to ocean-sea ice-atmosphere exchange processes remains poorly understood. Frost flowers form when moisture from seawater becomes available to a cold atmosphere and surface winds are low, allowing for supersaturation of the near-surface boundary layer. Ice grown in a pond cut in young ice at the mouth of Young Sound, NE Greenland, in March 2012, showed that expanding frost flower clusters began forming as soon as the ice formed. The new ice and frost flowers dramatically changed the radiative and thermal environment. The frost flowers were about 5°C colder than the brine surface, with an approximately linear temperature gradient from their base to their upper tips. Salinity and δ18O values indicated that frost flowers primarily originated from the surface brine skim. Ikaite crystals were observed to form within an hour in both frost flowers and the thin pond ice. Average ikaite concentrations were 1013 µmol kg-1 in frost flowers and 1061 µmol kg-1 in the surface slush layer. Chamber flux measurements confirmed an efflux of CO2 at the brine-wetted sea ice surface, in line with expectations from the brine chemistry. Bacteria concentrations generally increased with salinity in frost flowers and the surface slush layer. Bacterial densities and taxa indicated that a selective process occurred at the ice surface and confirmed the general pattern of primary oceanic origin versus negligible atmospheric deposition.

  20. An ice shelf breakup

    SciTech Connect

    Fahnestock, M.

    1996-02-09

    Glaciers and ice sheets are controlled by the climate and must change if the conditions that led to their current configurations are changing. These ice masses exist at the interface between the atmosphere, which provides sustaining snowfall and thermal regulation, and the land, which provides a stable base and in many cases the elevation required to reach suitably cold conditions. Ice sheets and glaciers are distributed around the globe and can serve as potential indicators of past climate variability and current climatic trends. 9 refs.

  1. Ice caps on venus?

    PubMed

    Libby, W F

    1968-03-08

    The data on Venus obtained by Mariner V and Venera 4 are interpreted as evidence of giant polar ice caps holding the water that must have come out of the volcanoes with the observed carbon dioxide, on the assumption that Earth and Venus are of similar composition and volcanic history. The measurements by Venera 4 of the equatorial surface temperature indicate that the microwave readings were high, so that the polar ice caps may be allowed to exist in the face of the 10-centimeter readings of polar temperature. Life seems to be distinctly possible at the edges of the ice sheets.

  2. Ice Jam Data Collection

    DTIC Science & Technology

    1994-03-01

    Sweden, p. 301- LITERATURE CITED 317. Pomerleau, R.T. (1992a) Field ice measurements Beltaos , S . (1978) Field investigations of river ice for...9, LuleA, Sweden, p. 355-371. Proceedings of the 16th Annual Conference of the Beltaos , S ., R. Gerard, S . Petryk and T.D. Association of State...AD- A280 067 Ice Jam Data Collection Kathleen D. White and Jon E. ZufelT March 1994 DTIC S EECTEa @8199M411 aF FI 1,0 Tis EWE’~t a, pm. DTIC QUALFPy

  3. Climate Data Records (CDRs) for Ice Motion and Ice Age

    NASA Astrophysics Data System (ADS)

    Tschudi, M. A.; Fowler, C.; Maslanik, J. A.; Stroeve, J. C.

    2011-12-01

    Climate Data Records (CDRs) for remotely-sensed Arctic sea ice motion and sea ice age are under development by our group at the University of Colorado, Boulder. The ice motion product, archived at NSIDC, has a considerable history of use, while sea ice age is a relatively new product. Our technique to estimate sea ice motion utilizes images from SSM/I, as well as SMMR and the series of AVHRR sensors to estimate the daily motion of ice parcels. This method is augmented by incorporating ice motion observations from the network of drifting buoys deployed as part of the International Arctic Buoy Program. Our technique to calculate ice age relies on following the actual age of the ice for each ice parcel, categorizing the parcel as first-year ice, second-year, ice, etc. based on how many summer melt seasons the ice parcel survives. Both of these research-grade products have been interpolated onto 25x25 km grid points spanning the entire Arctic Ocean using the Equal-Area Scalable Earth (EASE) grid. Datasets generated from this program have shown that the Arctic ice cover has experienced a significant (> 70%) decline in multiyear ice over the last 20 years, leaving a younger ice cover in 2011. By comparing ice age derived by the Lagrangian tracking method to ice thickness estimated by Ice, Cloud and land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) data, it is observed that ice age is linearly related to ice thickness, up to an age of 10 years. Therefore, the shift in dominance of multiyear ice to first-year ice relates to a significant thinning of the ice. This thinning is estimated to correspond to a 40% reduction in ice volume in the last 20 years. An ancillary dataset (APP-X) produced by the University of Wisconsin, Madison has been combined with the ice motion product to monitor the properties of the sea ice parcels tracked by the ice motion product. This dataset includes ice surface and 2-meter air temperature, albedo, downwelling shortwave

  4. Advances in ice mechanics - 1987

    SciTech Connect

    Chung, J.S.; Hallam, S.D.; Maatanen, M.; Sinha, N.K.; Sodhi, D.S.

    1987-01-01

    This book presents the papers given at a symposium on the interaction of icebergs with offshore platforms. Topics considered at the symposium included advances in ice mechanics in the United Kingdom, ice mechanics in Finland, recent advances in ice mechanics in Canada, advances in sea ice mechanics in the USA, foundations, monitoring, hazards, risk assessment, and deformation.

  5. Creep of ice: Further studies

    NASA Technical Reports Server (NTRS)

    Heard, H. C.; Durham, W. B.; Kirby, S. H.

    1987-01-01

    Detailed studies have been done of ice creep as related to the icy satellites, Ganymede and Callisto. Included were: (1) the flow of high-pressure water ices II, III, and V, and (2) frictional sliding of ice I sub h. Work was also begun on the study of the effects of impurities on the flow of ice. Test results are summarized.

  6. Arctic Sea ice model sensitivities.

    SciTech Connect

    Peterson, Kara J.; Bochev, Pavel Blagoveston; Paskaleva, Biliana Stefanova

    2010-12-01

    Arctic sea ice is an important component of the global climate system and, due to feedback effects, the Arctic ice cover is changing rapidly. Predictive mathematical models are of paramount importance for accurate estimates of the future ice trajectory. However, the sea ice components of Global Climate Models (GCMs) vary significantly in their prediction of the future state of Arctic sea ice and have generally underestimated the rate of decline in minimum sea ice extent seen over the past thirty years. One of the contributing factors to this variability is the sensitivity of the sea ice state to internal model parameters. A new sea ice model that holds some promise for improving sea ice predictions incorporates an anisotropic elastic-decohesive rheology and dynamics solved using the material-point method (MPM), which combines Lagrangian particles for advection with a background grid for gradient computations. We evaluate the variability of this MPM sea ice code and compare it with the Los Alamos National Laboratory CICE code for a single year simulation of the Arctic basin using consistent ocean and atmospheric forcing. Sensitivities of ice volume, ice area, ice extent, root mean square (RMS) ice speed, central Arctic ice thickness,and central Arctic ice speed with respect to ten different dynamic and thermodynamic parameters are evaluated both individually and in combination using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). We find similar responses for the two codes and some interesting seasonal variability in the strength of the parameters on the solution.

  7. Bacteria isolated from amoebae/bacteria consortium

    DOEpatents

    Tyndall, R.L.

    1995-05-30

    New protozoan derived microbial consortia and method for their isolation are provided. Consortia and bacteria isolated therefrom are useful for treating wastes such as trichloroethylene and trinitrotoluene. Consortia, bacteria isolated therefrom, and dispersants isolated therefrom are useful for dispersing hydrocarbons such as oil, creosote, wax, and grease.

  8. Bacteria isolated from amoebae/bacteria consortium

    DOEpatents

    Tyndall, Richard L.

    1995-01-01

    New protozoan derived microbial consortia and method for their isolation are provided. Consortia and bacteria isolated therefrom are useful for treating wastes such as trichloroethylene and trinitrotoluene. Consortia, bacteria isolated therefrom, and dispersants isolated therefrom are useful for dispersing hydrocarbons such as oil, creosote, wax, and grease.

  9. Microorganisms Trapped Within Permafrost Ice In The Fox Permafrost Tunnel, Alaska

    NASA Astrophysics Data System (ADS)

    Katayama, T.; Tanaka, M.; Douglas, T. A.; Cai, Y.; Tomita, F.; Asano, K.; Fukuda, M.

    2008-12-01

    Several different types of massive ice are common in permafrost. Ice wedges are easily recognized by their shape and foliated structure. They grow syngenetically or epigenetically as a result of repeated cycles of frost cracking followed by the infiltration of snow, melt water, soil or other material into the open frost cracks. Material incorporated into ice wedges becomes frozen and preserved. Pool ice, another massive ice type, is formed by the freezing of water resting on top of frozen thermokarst sediment or melting wedges and is not foliated. The Fox Permafrost Tunnel in Fairbanks was excavated within the discontinuous permafrost zone of central Alaska and it contains permafrost, ice wedges, and pool ice preserved at roughly -3°C. We collected samples from five ice wedges and three pool ice structures in the Fox Permafrost Tunnel. If the microorganisms were incorporated into the ice during its formation, a community analysis of the microorganisms could elucidate the environment in which the ice was formed. Organic material from sediments in the tunnel was radiocarbon-dated between 14,000 and 30,000 years BP. However, it is still not clear when the ice wedges were formed or subsequently deformed because they are only partially exposed and their upper surfaces are above the tunnel walls. The objectives of our study were to determine the biogeochemical conditions during massive ice formation and to analyze the microbial community within the ices by incubation-based and DNA-based analyses. The geochemical profile and the PCR-DGGE band patterns of bacteria among five ice wedge and 3 portions of pool ice samples were markedly different. The DGGE band patterns of fungi were simple with a few bands of fungi or yeast. The dominant bands of ice wedge and pool ice samples were affiliated with the genus Geomyces and Doratomyces, respectively. Phylogenetic analysis using rRNA gene ITS regions indicated isolates of Geomyces spp. from different ice wedges were affiliated

  10. Broad-scale predictability of carbohydrates and exopolymers in Antarctic and Arctic sea ice.

    PubMed

    Underwood, Graham J C; Aslam, Shazia N; Michel, Christine; Niemi, Andrea; Norman, Louiza; Meiners, Klaus M; Laybourn-Parry, Johanna; Paterson, Harriet; Thomas, David N

    2013-09-24

    Sea ice can contain high concentrations of dissolved organic carbon (DOC), much of which is carbohydrate-rich extracellular polymeric substances (EPS) produced by microalgae and bacteria inhabiting the ice. Here we report the concentrations of dissolved carbohydrates (dCHO) and dissolved EPS (dEPS) in relation to algal standing stock [estimated by chlorophyll (Chl) a concentrations] in sea ice from six locations in the Southern and Arctic Oceans. Concentrations varied substantially within and between sampling sites, reflecting local ice conditions and biological content. However, combining all data revealed robust statistical relationships between dCHO concentrations and the concentrations of different dEPS fractions, Chl a, and DOC. These relationships were true for whole ice cores, bottom ice (biomass rich) sections, and colder surface ice. The distribution of dEPS was strongly correlated to algal biomass, with the highest concentrations of both dEPS and non-EPS carbohydrates in the bottom horizons of the ice. Complex EPS was more prevalent in colder surface sea ice horizons. Predictive models (validated against independent data) were derived to enable the estimation of dCHO concentrations from data on ice thickness, salinity, and vertical position in core. When Chl a data were included a higher level of prediction was obtained. The consistent patterns reflected in these relationships provide a strong basis for including estimates of regional and seasonal carbohydrate and dEPS carbon budgets in coupled physical-biogeochemical models, across different types of sea ice from both polar regions.

  11. Survivability of bacteria ejected from icy surfaces after hypervelocity impact.

    PubMed

    Burchell, Mark J; Galloway, James A; Bunch, Alan W; Brandão, Pedro F B

    2003-02-01

    Both the Saturnian and Jovian systems contain satellites with icy surfaces. If life exists on any of these icy bodies (in putative subsurface oceans for example) then the possibility exists for transfer of life from icy body to icy body. This is an application of the idea of Panspermia, wherein life migrates naturally through space. A possible mechanism would be that life, here taken as bacteria, could become frozen in the icy surface of one body. If a high-speed impact occurred on that surface, ejecta containing the bacteria could be thrown into space. It could then migrate around the local region of space until it arrived at a second icy body in another high-speed impact. In this paper we consider some of the necessary steps for such a process to occur, concentrating on the ejection of ice bearing bacteria in the initial impact, and on what happens when bacteria laden projectiles hit an icy surface. Laboratory experiments using high-speed impacts with a light gas gun show that obtaining icy ejecta with viable bacterial loads is straightforward. In addition to demonstrating the viability of the bacteria carried on the ejecta, we have also measured the angular and size distribution of the ejecta produced in hypervelocity impacts on ice. We have however been unsuccessful at transferring viable bacteria to icy surfaces from bacteria laden projectiles impacting at hypervelocities.

  12. Ice interaction with offshore structures

    SciTech Connect

    Cammaert, A.B.; Muggeridge, D.B.

    1988-01-01

    Oil platforms and other offshore structures being built in the arctic regions must be able to withstand icebergs, ice islands, and pack ice. This reference explain the effect ice has on offshore structures and demonstrates design and construction methods that allow such structures to survive in harsh, ice-ridden environments. It analyzes the characteristics of sea ice as well as dynamic ice forces on structures. Techniques for ice modeling and field testing facilitate the design and construction of sturdy, offshore constructions. Computer programs included.

  13. Vortex ice in nanostructured superconductors

    SciTech Connect

    Reichhardt, Charles; Reichhardt, Cynthia J; Libal, Andras J

    2008-01-01

    We demonstrate using numerical simulations of nanostructured superconductors that it is possible to realize vortex ice states that are analogous to square and kagome ice. The system can be brought into a state that obeys either global or local ice rules by applying an external current according to an annealing protocol. We explore the breakdown of the ice rules due to disorder in the nanostructure array and show that in square ice, topological defects appear along grain boundaries, while in kagome ice, individual defects appear. We argue that the vortex system offers significant advantages over other artificial ice systems.

  14. Ubiquity of biological ice nucleators in snowfall.

    PubMed

    Christner, Brent C; Morris, Cindy E; Foreman, Christine M; Cai, Rongman; Sands, David C

    2008-02-29

    Despite the integral role of ice nucleators (IN) in atmospheric processes leading to precipitation, their sources and distributions have not been well established. We examined IN in snowfall from mid- and high-latitude locations and found that the most active were biological in origin. Of the IN larger than 0.2 micrometer that were active at temperatures warmer than -7 degrees C, 69 to 100% were biological, and a substantial fraction were bacteria. Our results indicate that the biosphere is a source of highly active IN and suggest that these biological particles may affect the precipitation cycle and/or their own precipitation during atmospheric transport.

  15. The Antartic Ice Borehole Probe

    NASA Technical Reports Server (NTRS)

    Behar, A.; Carsey, F.; Lane, A.; Engelhardt, H.

    2000-01-01

    The Antartic Ice Borehole Probe mission is a glaciological investigation, scheduled for November 2000-2001, that will place a probe in a hot-water drilled hole in the West Antartic ice sheet. The objectives of the probe are to observe ice-bed interactions with a downward looking camera, and ice inclusions and structure, including hypothesized ice accretion, with a side-looking camera.

  16. Waves on Ice

    Atmospheric Science Data Center

    2013-04-16

    ... a wavy pattern on the ice surface. One of MISR's cloud classification products, the Angular Signature Cloud Mask (ASCM), correctly ... NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Science Mission Directorate, Washington, D.C. The Terra spacecraft is managed ...

  17. Veil of Ice

    NASA Image and Video Library

    2007-01-12

    The Cassini spacecraft stares toward Saturn through its gauzy veil of rings. The great ice-particle screen acts like a filter here, attenuating the glare from the planet and making its high altitude haze easy to see

  18. Global ice sheet modeling

    SciTech Connect

    Hughes, T.J.; Fastook, J.L.

    1994-05-01

    The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed.

  19. Ice Cream Stick Math.

    ERIC Educational Resources Information Center

    Paddock, Cynthia

    1992-01-01

    Described is a teaching technique which uses the collection of ice cream sticks as a means of increasing awareness of quantity in a self-contained elementary special class for students with learning disabilities and mild mental retardation. (DB)

  20. Ice age terminations.

    PubMed

    Cheng, Hai; Edwards, R Lawrence; Broecker, Wallace S; Denton, George H; Kong, Xinggong; Wang, Yongjin; Zhang, Rong; Wang, Xianfeng

    2009-10-09

    230Th-dated oxygen isotope records of stalagmites from Sanbao Cave, China, characterize Asian Monsoon (AM) precipitation through the ends of the third- and fourthmost recent ice ages. As a result, AM records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments, establishing the timing and sequence of major events. In all four cases, observations are consistent with a classic Northern Hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets. Meltwater and icebergs entering the North Atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon, causing increases in atmospheric CO2 and Antarctic temperatures that drive the termination in the Southern Hemisphere. Increasing CO2 and summer insolation drive recession of northern ice sheets, with probable positive feedbacks between sea level and CO2.

  1. Ice Cream Stick Math.

    ERIC Educational Resources Information Center

    Paddock, Cynthia

    1992-01-01

    Described is a teaching technique which uses the collection of ice cream sticks as a means of increasing awareness of quantity in a self-contained elementary special class for students with learning disabilities and mild mental retardation. (DB)

  2. Antarctic stratospheric ice crystals

    NASA Technical Reports Server (NTRS)

    Goodman, J.; Toon, O. B.; Pueschel, R. F.; Snetsinger, K. G.; Verma, S.

    1989-01-01

    Ice crystals were replicated over the Palmer Peninsula at approximately 72 deg S on six occasions during the 1987 Airboirne Antarctic Ozone Experiment. The sampling altitude was between 12.5 and 18.5 km (45-65 thousand ft pressure altitude) with the temperature between 190 and 201 K. The atmosphere was subsaturated with respect to ice in all cases. The collected crystals were predominantly solid and hollow columns. The largest crystals were sampled at lower altitudes where the potential temperature was below 400 K. While the crystals were larger than anticipated, their low concentration results in a total surface area that is less than one tenth of the total aerosol surface area. The large ice crystals may play an important role in the observed stratospheric dehydration processes through sedimentation. Evidence of scavenging of submicron particles further suggests that the ice crystals may be effective in the removal of stratospheric chemicals.

  3. Photoplastic effect on ice

    SciTech Connect

    Khusnatdinov, N.N.; Petrenko, V.F.

    1995-09-01

    The study of photoplastic effect (PPE) on ice is essential for both fundamental and applied reasons. It is important for an understanding of dislocation motion as well as the flow of glaciers in cold regions that occurs under intensive solar radiation. It was found that the illumination of ice with UV light ({lambda}<300 nm) leads to its irreversible hardening. A prolonged irradiation with a total light exposure of about 8{center_dot}10{sup {minus}5} J/cm{sup 2} at {lambda} = 260 nm can change the creep rate up to 60 percent. Even more pronounced PPE was found in HCl-doped ice with the concentration, n = 10{sup 18} cm{sup {minus}3}. It is suggested that PPE is caused by the excitation of ``autoionization`` reaction which was found responsible for the photoconductivity of ice.

  4. Record Sea Ice Minimum

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Arctic sea ice reached a record low in September 2007, below the previous record set in 2005 and substantially below the long-term average. This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA's Aqua satellite on September 16, 2007. In this image, blue indicates open water, white indicates high sea ice concentration, and turquoise indicates loosely packed sea ice. The black circle at the North Pole results from an absence of data as the satellite does not make observations that far north. Three contour lines appear on this image. The red line is the 2007 minimum, as of September 15, about the same time the record low was reached, and it almost exactly fits the sea ice observed by AMSR-E. The green line indicates the 2005 minimum, the previous record low. The yellow line indicates the median minimum from 1979 to 2000.

  5. ION COMPOSITION ELUCIDATION (ICE)

    EPA Science Inventory



    Ion Composition Elucidation (ICE) utilizes selected ion recording with a double focusing mass spectrometer to simultaneously determine exact masses and relative isotopic abundances from mass peak profiles. These can be determined more accurately and at higher sensitivity ...

  6. Ice reconnaissance by satellite

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Strome, W. M.

    1976-01-01

    The paper describes the significant milestones in the use of satellites for snow and ice monitoring. The feasibility of such monitoring was demonstrated by the Tiros 2 satellite in 1961. Nimbus 1 showed that breaks in the sea ice can be easily monitored during continuous nighttime conditions; Nimbus 3 showed the practicality of delineating regions of active melting of ice and snow in temperate areas. Landsat data have been found to be particularly useful for monitoring and studying glaciers and their attendant surface features. Ice concentration can be determined with reasonable accuracy from a sequence of electronically scanned microwave radiomenter images made aboard Nimbus 5. In the future we can expect improved sensors and spacecraft systems with longer operating lives.

  7. Sea Ice Minimum 2016

    NASA Image and Video Library

    This animation shows the evolution of the Arctic sea ice cover from its wintertime maximum extent, which was reached on Mar. 24, 2016, and was the lowest on record for the second year in a row, to ...

  8. Web life: Ice Flows

    NASA Astrophysics Data System (ADS)

    2016-11-01

    Computer and video gamers of a certain vintage will have fond memories of Lemmings, a game in which players must shepherd pixelated, suicidal rodents around a series of obstacles to reach safety. At first glance, Ice Flows is strikingly similar.

  9. 2011 Sea Ice Minimum

    NASA Image and Video Library

    This video shows Arctic sea ice from March 7, 2011, to Sept. 9, 2011, ending with a comparison of the 30-year average minimum extent, shown in yellow, and the Northwest Passage, in red. (no audio) ...

  10. Record Sea Ice Minimum

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Arctic sea ice reached a record low in September 2007, below the previous record set in 2005 and substantially below the long-term average. This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA's Aqua satellite on September 16, 2007. In this image, blue indicates open water, white indicates high sea ice concentration, and turquoise indicates loosely packed sea ice. The black circle at the North Pole results from an absence of data as the satellite does not make observations that far north. Three contour lines appear on this image. The red line is the 2007 minimum, as of September 15, about the same time the record low was reached, and it almost exactly fits the sea ice observed by AMSR-E. The green line indicates the 2005 minimum, the previous record low. The yellow line indicates the median minimum from 1979 to 2000.

  11. Developing a new parameterization framework for the heterogeneous ice nucleation of atmospheric aerosol particles

    NASA Astrophysics Data System (ADS)

    Ullrich, Romy; Hiranuma, Naruki; Hoose, Corinna; Möhler, Ottmar; Niemand, Monika; Steinke, Isabelle; Wagner, Robert

    2014-05-01

    Developing a new parameterization framework for the heterogeneous ice nucleation of atmospheric aerosol particles Ullrich, R., Hiranuma, N., Hoose, C., Möhler, O., Niemand, M., Steinke, I., Wagner, R. Aerosols of different nature induce microphysical processes of importance for the Earth's atmosphere. They affect not only directly the radiative budget, more importantly they essentially influence the formation and life cycles of clouds. Hence, aerosols and their ice nucleating ability are a fundamental input parameter for weather and climate models. During the previous years, the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber was used to extensively measure, under nearly realistic conditions, the ice nucleating properties of different aerosols. Numerous experiments were performed with a broad variety of aerosol types and under different freezing conditions. A reanalysis of these experiments offers the opportunity to develop a uniform parameterization framework of ice formation for many atmospherically relevant aerosols in a broad temperature and humidity range. The analysis includes both deposition nucleation and immersion freezing. The aim of this study is to develop this comprehensive parameterization for heterogeneous ice formation mainly by using the ice nucleation active site (INAS) approach. Niemand et al. (2012) already developed a temperature dependent parameterization for the INAS- density for immersion freezing on desert dust particles. In addition to a reanalysis of the ice nucleation behaviour of desert dust (Niemand et al. (2012)), volcanic ash (Steinke et al. (2010)) and organic particles (Wagner et al. (2010,2011)) this contribution will also show new results for the immersion freezing and deposition nucleation of soot aerosols. The next step will be the implementation of the parameterizations into the COSMO- ART model in order to test and demonstrate the usability of the framework. Hoose, C. and Möhler, O. (2012) Atmos

  12. Altimeter Sea Ice Workshop

    DTIC Science & Technology

    1990-09-01

    Science Fax- 164513 Chalmers University of TechnologyI S-41296 Goteborg, Sweden 5 Altimeter Sea Ice Workshop Presentation Summary Hawkins: Present U.S...into the ground. A large tent slides over the top of the pond for solar shading and inclement weather protection. A mobile gantry, which spans the width...tracks can covering the pond to protect the growing ice from weather when necessary. A walkway mounted on the tracks serves as a mobile base on which the

  13. Bacteria Inactivation During Lithotripsy

    NASA Astrophysics Data System (ADS)

    del Sol Quintero, María; Mora, Ulises; Gutiérrez, Jorge; Mues, Enrique; Castaño, Eduardo; Fernández, Francisco; Loske, Achim M.

    2006-09-01

    The influence of extracorporeal and intracorporeal lithotripsy on the viability of bacteria contained inside artificial kidney stones was investigated in vitro. Two different bacteria were exposed to the action of one extracorporeal shock wave generator and four intracorporeal lithotripters.

  14. Bleach vs. Bacteria

    MedlinePlus

    ... Articles | Inside Life Science Home Page Bleach vs. Bacteria By Sharon Reynolds Posted April 2, 2014 Your ... hypochlorous acid to help kill invading microbes, including bacteria. Researchers funded by the National Institutes of Health ...

  15. Water Ice on Triton

    NASA Astrophysics Data System (ADS)

    Cruikshank, Dale P.; Schmitt, Bernard; Roush, Ted L.; Owen, Tobias C.; Quirico, Eric; Geballe, Thomas R.; de Bergh, Catherine; Bartholomew, Mary Jane; Dalle Ore, Cristina M.; Douté, Sylvain; Meier, Roland

    2000-09-01

    We discuss the spectroscopic detection of H 2O ice on Triton, evidenced by the broad absorption bands in the near infrared at 1.55 and 2.04 μm. The detection of water ice on Triton reconfirms earlier preliminary studies (D. P. Cruikshank et al. 1984, Icarus58, 293-305). Although crystalline H 2O ice has a distinctive spectral band at 1.65 μm, and our new models slightly favor the presence of this phase, we cannot unambiguously determine whether Triton's water ice is crystalline or amorphous. Both phases might be present, and special conditions in the surface microstructure may affect the spectroscopic signature of water ice in such a way that crystalline ice is present and its 1.65 μm spectral band is masked. Our spectra (1.87-2.5 μm) taken at an interval of nearly 3.5 years do not show any significant changes that might relate to reports of changes in Triton's spectral reflectance (B. Buratti et al. 1999, Nature397, 219), or in Triton's surface pressure (J. L. Elliot et al. 1998, Nature393, 765-767).

  16. Modelling sea ice dynamics

    NASA Astrophysics Data System (ADS)

    Murawski, Jens; Kleine, Eckhard

    2017-04-01

    Sea ice remains one of the frontiers of ocean modelling and is of vital importance for the correct forecasts of the northern oceans. At large scale, it is commonly considered a continuous medium whose dynamics is modelled in terms of continuum mechanics. Its specifics are a matter of constitutive behaviour which may be characterised as rigid-plastic. The new developed sea ice dynamic module bases on general principles and follows a systematic approach to the problem. Both drift field and stress field are modelled by a variational property. Rigidity is treated by Lagrangian relaxation. Thus one is led to a sensible numerical method. Modelling fast ice remains to be a challenge. It is understood that ridging and the formation of grounded ice keels plays a role in the process. The ice dynamic model includes a parameterisation of the stress associated with grounded ice keels. Shear against the grounded bottom contact might lead to plastic deformation and the loss of integrity. The numerical scheme involves a potentially large system of linear equations which is solved by pre-conditioned iteration. The entire algorithm consists of several components which result from decomposing the problem. The algorithm has been implemented and tested in practice.

  17. Ice-Borehole Probe

    NASA Technical Reports Server (NTRS)

    Behar, Alberto; Carsey, Frank; Lane, Arthur; Engelhardt, Herman

    2006-01-01

    An instrumentation system has been developed for studying interactions between a glacier or ice sheet and the underlying rock and/or soil. Prior borehole imaging systems have been used in well-drilling and mineral-exploration applications and for studying relatively thin valley glaciers, but have not been used for studying thick ice sheets like those of Antarctica. The system includes a cylindrical imaging probe that is lowered into a hole that has been bored through the ice to the ice/bedrock interface by use of an established hot-water-jet technique. The images acquired by the cameras yield information on the movement of the ice relative to the bedrock and on visible features of the lower structure of the ice sheet, including ice layers formed at different times, bubbles, and mineralogical inclusions. At the time of reporting the information for this article, the system was just deployed in two boreholes on the Amery ice shelf in East Antarctica and after successful 2000 2001 deployments in 4 boreholes at Ice Stream C, West Antarctica, and in 2002 at Black Rapids Glacier, Alaska. The probe is designed to operate at temperatures from 40 to +40 C and to withstand the cold, wet, high-pressure [130-atm (13.20-MPa)] environment at the bottom of a water-filled borehole in ice as deep as 1.6 km. A current version is being outfitted to service 2.4-km-deep boreholes at the Rutford Ice Stream in West Antarctica. The probe (see figure) contains a sidelooking charge-coupled-device (CCD) camera that generates both a real-time analog video signal and a sequence of still-image data, and contains a digital videotape recorder. The probe also contains a downward-looking CCD analog video camera, plus halogen lamps to illuminate the fields of view of both cameras. The analog video outputs of the cameras are converted to optical signals that are transmitted to a surface station via optical fibers in a cable. Electric power is supplied to the probe through wires in the cable at a

  18. Ice sheets. Volume loss from Antarctic ice shelves is accelerating.

    PubMed

    Paolo, Fernando S; Fricker, Helen A; Padman, Laurie

    2015-04-17

    The floating ice shelves surrounding the Antarctic Ice Sheet restrain the grounded ice-sheet flow. Thinning of an ice shelf reduces this effect, leading to an increase in ice discharge to the ocean. Using 18 years of continuous satellite radar altimeter observations, we have computed decadal-scale changes in ice-shelf thickness around the Antarctic continent. Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 cubic kilometers per year for 1994-2003 to rapid loss of 310 ± 74 cubic kilometers per year for 2003-2012. West Antarctic losses increased by ~70% in the past decade, and earlier volume gain by East Antarctic ice shelves ceased. In the Amundsen and Bellingshausen regions, some ice shelves have lost up to 18% of their thickness in less than two decades.

  19. Ice recrystallization inhibition in ice cream by propylene glycol monostearate.

    PubMed

    Aleong, J M; Frochot, S; Goff, H D

    2008-11-01

    The effectiveness of propylene glycol monostearate (PGMS) to inhibit ice recrystallization was evaluated in ice cream and frozen sucrose solutions. PGMS (0.3%) dramatically reduced ice crystal sizes in ice cream and in sucrose solutions frozen in a scraped-surface freezer before and after heat shock, but had no effect in quiescently frozen solutions. PGMS showed limited emulsifier properties by promoting smaller fat globule size distributions and enhanced partial coalescence in the mix and ice cream, respectively, but at a much lower level compared to conventional ice cream emulsifier. Low temperature scanning electron microscopy revealed highly irregular crystal morphology in both ice cream and sucrose solutions frozen in a scraped-surface freezer. There was strong evidence to suggest that PGMS directly interacts with ice crystals and interferes with normal surface propagation. Shear during freezing may be required for its distribution around the ice and sufficient surface coverage.

  20. Interaction of ice binding proteins with ice, water and ions.

    PubMed

    Oude Vrielink, Anneloes S; Aloi, Antonio; Olijve, Luuk L C; Voets, Ilja K

    2016-03-19

    Ice binding proteins (IBPs) are produced by various cold-adapted organisms to protect their body tissues against freeze damage. First discovered in Antarctic fish living in shallow waters, IBPs were later found in insects, microorganisms, and plants. Despite great structural diversity, all IBPs adhere to growing ice crystals, which is essential for their extensive repertoire of biological functions. Some IBPs maintain liquid inclusions within ice or inhibit recrystallization of ice, while other types suppress freezing by blocking further ice growth. In contrast, ice nucleating proteins stimulate ice nucleation just below 0 °C. Despite huge commercial interest and major scientific breakthroughs, the precise working mechanism of IBPs has not yet been unraveled. In this review, the authors outline the state-of-the-art in experimental and theoretical IBP research and discuss future scientific challenges. The interaction of IBPs with ice, water and ions is examined, focusing in particular on ice growth inhibition mechanisms.

  1. Ice Flow in the North East Greenland Ice Stream

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Kwok, Ron; Fahnestock, M.; MacAyeal, Doug

    1999-01-01

    Early observations with ERS-1 SAR image data revealed a large ice stream in North East Greenland (Fahnestock 1993). The ice stream has a number of the characteristics of the more closely studied ice streams in Antarctica, including its large size and gross geometry. The onset of rapid flow close to the ice divide and the evolution of its flow pattern, however, make this ice stream unique. These features can be seen in the balance velocities for the ice stream (Joughin 1997) and its outlets. The ice stream is identifiable for more than 700 km, making it much longer than any other flow feature in Greenland. Our research goals are to gain a greater understanding of the ice flow in the northeast Greenland ice stream and its outlet glaciers in order to assess their impact on the past, present, and future mass balance of the ice sheet. We will accomplish these goals using a combination of remotely sensed data and ice sheet models. We are using satellite radar interferometry data to produce a complete maps of velocity and topography over the entire ice stream. We are in the process of developing methods to use these data in conjunction with existing ice sheet models similar to those that have been used to improve understanding of the mechanics of flow in Antarctic ice streams.

  2. Ice Flow in the North East Greenland Ice Stream

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Kwok, Ron; Fahnestock, M.; MacAyeal, Doug

    1999-01-01

    Early observations with ERS-1 SAR image data revealed a large ice stream in North East Greenland (Fahnestock 1993). The ice stream has a number of the characteristics of the more closely studied ice streams in Antarctica, including its large size and gross geometry. The onset of rapid flow close to the ice divide and the evolution of its flow pattern, however, make this ice stream unique. These features can be seen in the balance velocities for the ice stream (Joughin 1997) and its outlets. The ice stream is identifiable for more than 700 km, making it much longer than any other flow feature in Greenland. Our research goals are to gain a greater understanding of the ice flow in the northeast Greenland ice stream and its outlet glaciers in order to assess their impact on the past, present, and future mass balance of the ice sheet. We will accomplish these goals using a combination of remotely sensed data and ice sheet models. We are using satellite radar interferometry data to produce a complete maps of velocity and topography over the entire ice stream. We are in the process of developing methods to use these data in conjunction with existing ice sheet models similar to those that have been used to improve understanding of the mechanics of flow in Antarctic ice streams.

  3. Enhanced Sea Ice Concentration and Ice Temperature Algorithms for AMSR

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.; Manning, Will; Gersten, Robert

    1998-01-01

    Accurate quantification of sea ice concentration and ice temperature from satellite passive microwave data is important because they provide the only long term, spatially detailed and consistent data set needed to study the climatology of the polar regions. Sea ice concentration data are used to derive large-scale daily ice extents that are utilized in trend analysis of the global sea ice cover. They are also used to quantify the amount of open water and thin ice in polynya and divergence regions which together with ice temperatures are in turn needed to estimate vertical heat and salinity fluxes in these regions. Sea ice concentrations have been derived from the NASA Team and Bootstrap algorithms while a separate technique for deriving ice temperature has been reported. An integrated technique that will utilizes most of the channels of AMSR (Advanced Microwave Scanning Radiometer) has been developed. The technique uses data from the 6 GHz and 37 GHz channels at vertical polarization obtain an initial estimate of sea ice concentration and ice temperature. The derived ice temperature is then utilized to estimate the emissivities for the corresponding observations at all the other channels. A procedure for calculating the ice concentration similar to the Bootstrap technique is then used but with variables being emissivities instead of brightness temperatures to minimizes errors associated with spatial changes in ice temperatures within the ice pack. Comparative studies of ice concentration results with those from other algorithms, including the original Bootstrap algorithm and those from high resolution satellite visible and infrared data will be presented. Also, results from a simulation study that demonstrates the effectiveness of the technique in correcting for spatial variations in ice temperatures will be shown. The ice temperature results are likewise compared with satellite infrared and buoy data with the latter adjusted to account for the effects of the snow

  4. Sea Ice Friction: The Effect of Ice Rubble

    NASA Astrophysics Data System (ADS)

    Scourfield, S.; Sammonds, P. R.; Lishman, B.; Riska, K.; Marchenko, A. V.

    2015-12-01

    Ice deformation processes in the Arctic often generate ice rubble, and situations arise where ice fragments of varying size separate sea ice floes. While the shear forces between sea ice floes in direct contact with each other are controlled by ice-ice friction, what is not known is how the slip of the floes is affected by the presence of rubble between the sliding surfaces. We present the result of field experiments undertaken on fjord ice in Svea, Svalbard, which investigated the velocity and hold time dependence of sea ice friction involving ice gouge. Average air temperature for the duration of time in which experiments were run was -12.4°C, and the thickness of the level fjord ice was 70 cm. A double-direct-shear experiment was done on floating sea ice in the field, with the addition of rubble ice between the sliding surfaces. This was achieved by moving a floating ice block through a channel of open water whilst subjected to normal loading, which was transferred through regions of ice rubble on both sides of the mobile block. The ice rubble regions were 30 cm deep and 50 cm wide. The displacement of the block and the force needed to move the block were measured. The rate dependence of friction was investigated for speeds of 10-3 to 10-2 ms-1. To investigate the state dependence of friction, slide-hold-slide (SHS) tests were conducted for hold times ranging from 1 second to 18 hours. When comparing the results from these experiments with a model for ice friction presented by Schulson and Fortt (2013), similar behaviour is seen at low hold times, where the peak coefficient of friction has a linear relationship with the logarithm of hold time. This is not the case for long hold times, however, and we attribute this to thermal consolidation of the ice rubble region.

  5. Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover

    DTIC Science & Technology

    2015-09-30

    and iv) onset dates of melt and freeze up. 4. Assess the magnitude of the contribution from ice -albedo feedback to the observed decrease of sea ice ...in the Chukchi and Beaufort Seas. 5. Relate solar heat input to the ice and ocean to surface, bottom, lateral, and internal melting of the ice ...concentration and melt and freeze up onset dates by i) examining the impact of the shift from multiyear to seasonal ice ; ii) determining heat absorbed in

  6. Wave-Ice and Air-Ice-Ocean Interaction During the Chukchi Sea Ice Edge Advance

    DTIC Science & Technology

    2015-09-30

    Ocean Heat: In the new Arctic summer ice regime, with extended open water periods in areas previously covered with sea ice, ocean heat, received...during these summer ice-free periods, may be either confined to the surface mixed layer or enter deeper ocean waters . Our goal is to determine the...remains in the ocean and has residual effects on ice growth during winter and spring. Sea State Regime: Large expanses of ice-free water in the

  7. Onset of atmospheric ice formation in natural conditions

    NASA Astrophysics Data System (ADS)

    Conen, Franz; Zimmermann, Lukas

    2015-04-01

    Bacteria growing on plants are the particles with the warmest freezing temperature known for natural particles (-2 oC). Their onset of freezing is known to be conditioned by themperature, growth and nutrient status, and probably other factors that can not be assessed in situ, but are also not likely to be conserved when taking airborne bacteria to the laboratory. Whether such bacteria play a role in initiating the ice phase in clouds is therefore best studied directly in a cooling air mass in the natural environment. Investigations directly at cloud tops would be desirable. A more amenable place is the bottom of a valley where a cold air pool forms during clear nights and when radiation fog is likely to form. When shallow, such fog may resemble an inverted cloud with its top on the land surface and warmer air above it. The temperature of bacteria and other particles suspended in air under a clear sky around the onset of fog formation is probably several degrees below that of the surrounding air because of radiative cooling, which will affect the particle's activation as a cloud condensation nucleus and as an ice nucleus. Hence, ice particles probably form earlier than expected at a particular air temperature, grow rapidly and parachute to the surface, where their descent can be recorded by traps charged with supercooled water. We present, and would like to discuss, this kind of observation in principle and show some first results (subject to suitable weather conditions before the presentation).

  8. Arctic Summer Ice Processes

    NASA Technical Reports Server (NTRS)

    Holt, Benjamin

    1999-01-01

    The primary objective of this study is to estimate the flux of heat and freshwater resulting from sea ice melt in the polar seas. The approach taken is to examine the decay of sea ice in the summer months primarily through the use of spaceborne Synthetic Aperture Radar (SAR) imagery. The improved understanding of the dynamics of the melt process can be usefully combined with ice thermodynamic and upper ocean models to form more complete models of ice melt. Models indicate that more heat is absorbed in the upper ocean when the ice cover is composed of smaller rather than larger floes and when there is more open water. Over the course of the summer, floes disintegrate by physical forcing and heating, melting into smaller and smaller sizes. By measuring the change in distribution of floes together with open water over a summer period, we can make estimates of the amount of heating by region and time. In a climatic sense, these studies are intended to improve the understanding of the Arctic heat budget which can then be eventually incorporated into improved global climate models. This work has two focus areas. The first is examining the detailed effect of storms on floe size and open water. A strong Arctic low pressure storm has been shown to loosen up the pack ice, increase the open water concentration well into the pack ice, and change the distribution of floes toward fewer and smaller floes. This suggests episodic melting and the increased importance of horizontal (lateral) melt during storms. The second focus area is related to an extensive ship-based experiment that recently took place in the Arctic called Surface Heat Budget of the Arctic (SHEBA). An icebreaker was placed purposely into the older pack ice north of Alaska in September 1997. The ship served as the base for experimenters who deployed extensive instrumentation to measure the atmosphere, ocean, and ice during a one-year period. My experiment will be to derive similar measurements (floe size, open

  9. Arctic Summer Ice Processes

    NASA Technical Reports Server (NTRS)

    Holt, Benjamin

    1999-01-01

    The primary objective of this study is to estimate the flux of heat and freshwater resulting from sea ice melt in the polar seas. The approach taken is to examine the decay of sea ice in the summer months primarily through the use of spaceborne Synthetic Aperture Radar (SAR) imagery. The improved understanding of the dynamics of the melt process can be usefully combined with ice thermodynamic and upper ocean models to form more complete models of ice melt. Models indicate that more heat is absorbed in the upper ocean when the ice cover is composed of smaller rather than larger floes and when there is more open water. Over the course of the summer, floes disintegrate by physical forcing and heating, melting into smaller and smaller sizes. By measuring the change in distribution of floes together with open water over a summer period, we can make estimates of the amount of heating by region and time. In a climatic sense, these studies are intended to improve the understanding of the Arctic heat budget which can then be eventually incorporated into improved global climate models. This work has two focus areas. The first is examining the detailed effect of storms on floe size and open water. A strong Arctic low pressure storm has been shown to loosen up the pack ice, increase the open water concentration well into the pack ice, and change the distribution of floes toward fewer and smaller floes. This suggests episodic melting and the increased importance of horizontal (lateral) melt during storms. The second focus area is related to an extensive ship-based experiment that recently took place in the Arctic called Surface Heat Budget of the Arctic (SHEBA). An icebreaker was placed purposely into the older pack ice north of Alaska in September 1997. The ship served as the base for experimenters who deployed extensive instrumentation to measure the atmosphere, ocean, and ice during a one-year period. My experiment will be to derive similar measurements (floe size, open

  10. Isolation and characterization of phage-host systems from the Baltic Sea ice.

    PubMed

    Luhtanen, Anne-Mari; Eronen-Rasimus, Eeva; Kaartokallio, Hermanni; Rintala, Janne-Markus; Autio, Riitta; Roine, Elina

    2014-01-01

    In search for sea ice bacteria and their phages from the Baltic Sea ice, two ice samples were collected from land-fast ice in a south-west Finland coastal site in February and March 2011. Bacteria were isolated from the melted sea ice samples and phages were screened from the same samples for 43 purified isolates. Plaque-producing phages were found for 15 bacterial isolates at 3 °C. Ten phage isolates were successfully plaque purified and eight of them were chosen for particle purification to analyze their morphology and structural proteins. Phage 1/32 infecting an isolate affiliated to phylum Bacteroidetes (Flavobacterium sp.) is a siphovirus and six phages infecting isolates affiliated to γ-Proteobacteria (Shewanella sp.) hosts were myoviruses. Cross titrations between the hosts showed that all studied phages are host specific. Phage solutions, host growth and phage infection were tested in different temperatures revealing phage temperature tolerance up to 45 °C, whereas phage infection was in most of the cases retarded above 15 °C. This study is the first to report isolation and cultivation of ice bacteria and cold-active phages from the Baltic Sea ice.

  11. Study on Supercooling Release in Encapsulated Ice System

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Yooko; Hasagawa, Hiromi; Iwatsubo, Tetsushiro

    As regards the super cooling phenomena which is important matter in encapsulated ice system, the system efficient suffering from the super cooling release of water was estimated and the performance of release reagent was determined. The following conclusions were reached. (1) It was clear that the COP of heat storing of the system fell by 3% with decreasing release temperature by 1 degree centigrade. (2) As a result of determinations about release reagents, Xanthomonas campestris (ice nuclei bacteria) was very effective in release the super cooling state, and the performance was maintained in continuous application of freezing and melting.

  12. Ice crystal and ice nucleus measurements in cap clouds

    NASA Technical Reports Server (NTRS)

    Vali, G.; Rogers, D. C.; Deshler, T. L.

    1982-01-01

    Ice nucleation in cap clouds over a mountain in Wyoming was examined with airborne instrumentation. Crosswind and wind parallel passes were made through the clouds, with data being taken on the ice crystal concentrations and sizes. A total of 141 penetrations of 26 separate days in temperatures ranging from -7 to -24 C were performed. Subsequent measurements were also made 100 km away from the mountain. The ice crystal concentrations measured showed good correlation with the ice nucleus content in winter time, midcontinental air masses in Wyoming. Further studies are recommended to determine if the variations in the ice nucleus population are the cause of the variability if ice crystal content.

  13. Satellite remote sensing over ice

    NASA Technical Reports Server (NTRS)

    Thomas, R. H.

    1984-01-01

    Satellite remote sensing provides unique opportunities for observing ice-covered terrain. Passive-microwave data give information on snow extent on land, sea-ice extent and type, and zones of summer melting on the polar ice sheets, with the potential for estimating snow-accumulation rates on these ice sheets. All weather, high-resolution imagery of sea ice is obtained using synthetic aperture radars, and ice-movement vectors can be deduced by comparing sequential images of the same region. Radar-altimetry data provide highly detailed information on ice-sheet topography, with the potential for deducing thickening/thinning rates from repeat surveys. The coastline of Antarctica can be mapped accurately using altimetry data, and the size and spatial distribution of icebergs can be monitored. Altimetry data also distinguish open ocean from pack ice and they give an indication of sea-ice characteristics.

  14. Nucleation of Ice

    NASA Astrophysics Data System (ADS)

    Molinero, Valeria

    2009-03-01

    The freezing of water into ice is a ubiquitous transformation in nature, yet the microscopic mechanism of homogeneous nucleation of ice has not yet been elucidated. One of the reasons is that nucleation happens in time scales that are too fast for an experimental characterization and two slow for a systematic study with atomistic simulations. In this work we use coarse-grained molecular dynamics simulations with the monatomic model of water mW[1] to shed light into the mechanism of homogeneous nucleation of ice and its relationship to the thermodynamics of supercooled water. Cooling of bulk water produces either crystalline ice or low- density amorphous ice (LDA) depending on the quenching rate. We find that ice crystallization occurs faster at temperatures close to the liquid-liquid transition, defined as the point of maximum inflection of the density with respect to the temperature. At the liquid-liquid transition, the time scale of nucleation becomes comparable to the time scale of relaxation within the liquid phase, determining --effectively- the end of the metastable liquid state. Our results imply that no ultraviscous liquid water can exist at temperatures just above the much disputed glass transition of water. We discuss how the scenario is changed when water is in confinement, and the relationship of the mechanism of ice nucleation to that of other liquids that present the same phase behavior, silicon [2] and germanium [3]. [4pt] [1] Molinero, V. & Moore, E. B. Water modeled as an intermediate element between carbon and silicon. Journal of Physical Chemistry B (2008). Online at http://pubs.acs.org/cgi- bin/abstract.cgi/jpcbfk/asap/abs/jp805227c.html [0pt] [2] Molinero, V., Sastry, S. & Angell, C. A. Tuning of tetrahedrality in a silicon potential yields a series of monatomic (metal-like) glass formers of very high fragility. Physical Review Letters 97, 075701 (2006).

  15. Ice stream activity scaled to ice sheet volume during Laurentide Ice Sheet deglaciation.

    PubMed

    Stokes, C R; Margold, M; Clark, C D; Tarasov, L

    2016-02-18

    The contribution of the Greenland and West Antarctic ice sheets to sea level has increased in recent decades, largely owing to the thinning and retreat of outlet glaciers and ice streams. This dynamic loss is a serious concern, with some modelling studies suggesting that the collapse of a major ice sheet could be imminent or potentially underway in West Antarctica, but others predicting a more limited response. A major problem is that observations used to initialize and calibrate models typically span only a few decades, and, at the ice-sheet scale, it is unclear how the entire drainage network of ice streams evolves over longer timescales. This represents one of the largest sources of uncertainty when predicting the contributions of ice sheets to sea-level rise. A key question is whether ice streams might increase and sustain rates of mass loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. Here we reconstruct the activity of 117 ice streams that operated at various times during deglaciation of the Laurentide Ice Sheet (from about 22,000 to 7,000 years ago) and show that as they activated and deactivated in different locations, their overall number decreased, they occupied a progressively smaller percentage of the ice sheet perimeter and their total discharge decreased. The underlying geology and topography clearly influenced ice stream activity, but--at the ice-sheet scale--their drainage network adjusted and was linked to changes in ice sheet volume. It is unclear whether these findings can be directly translated to modern ice sheets. However, contrary to the view that sees ice streams as unstable entities that can accelerate ice-sheet deglaciation, we conclude that ice streams exerted progressively less influence on ice sheet mass balance during the retreat of the Laurentide Ice Sheet.

  16. Comparisons of cubed ice, crushed ice, and wetted ice on intramuscular and surface temperature changes.

    PubMed

    Dykstra, Joseph H; Hill, Holly M; Miller, Michael G; Cheatham, Christopher C; Michael, Timothy J; Baker, Robert J

    2009-01-01

    Many researchers have investigated the effectiveness of different types of cold application, including cold whirlpools, ice packs, and chemical packs. However, few have investigated the effectiveness of different types of ice used in ice packs, even though ice is one of the most common forms of cold application. To evaluate and compare the cooling effectiveness of ice packs made with cubed, crushed, and wetted ice on intramuscular and skin surface temperatures. Repeated-measures counterbalanced design. Human performance research laboratory. Twelve healthy participants (6 men, 6 women) with no history of musculoskeletal disease and no known preexisting inflammatory conditions or recent orthopaedic injuries to the lower extremities. Ice packs made with cubed, crushed, or wetted ice were applied to a standardized area on the posterior aspect of the right gastrocnemius for 20 minutes. Each participant was given separate ice pack treatments, with at least 4 days between treatment sessions. Cutaneous and intramuscular (2 cm plus one-half skinfold measurement) temperatures of the right gastrocnemius were measured every 30 seconds during a 20-minute baseline period, a 20-minute treatment period, and a 120-minute recovery period. Differences were observed among all treatments. Compared with the crushed-ice treatment, the cubed-ice and wetted-ice treatments produced lower surface and intramuscular temperatures. Wetted ice produced the greatest overall temperature change during treatment and recovery, and crushed ice produced the smallest change. As administered in our protocol, wetted ice was superior to cubed or crushed ice at reducing surface temperatures, whereas both cubed ice and wetted ice were superior to crushed ice at reducing intramuscular temperatures.

  17. Comparisons of Cubed Ice, Crushed Ice, and Wetted Ice on Intramuscular and Surface Temperature Changes

    PubMed Central

    Dykstra, Joseph H; Hill, Holly M; Miller, Michael G; Cheatham, Christopher C; Michael, Timothy J; Baker, Robert J

    2009-01-01

    Context: Many researchers have investigated the effectiveness of different types of cold application, including cold whirlpools, ice packs, and chemical packs. However, few have investigated the effectiveness of different types of ice used in ice packs, even though ice is one of the most common forms of cold application. Objective: To evaluate and compare the cooling effectiveness of ice packs made with cubed, crushed, and wetted ice on intramuscular and skin surface temperatures. Design: Repeated-measures counterbalanced design. Setting: Human performance research laboratory. Patients or Other Participants: Twelve healthy participants (6 men, 6 women) with no history of musculoskeletal disease and no known preexisting inflammatory conditions or recent orthopaedic injuries to the lower extremities. Intervention(s): Ice packs made with cubed, crushed, or wetted ice were applied to a standardized area on the posterior aspect of the right gastrocnemius for 20 minutes. Each participant was given separate ice pack treatments, with at least 4 days between treatment sessions. Main Outcome Measure(s): Cutaneous and intramuscular (2 cm plus one-half skinfold measurement) temperatures of the right gastrocnemius were measured every 30 seconds during a 20-minute baseline period, a 20-minute treatment period, and a 120-minute recovery period. Results: Differences were observed among all treatments. Compared with the crushed-ice treatment, the cubed-ice and wetted-ice treatments produced lower surface and intramuscular temperatures. Wetted ice produced the greatest overall temperature change during treatment and recovery, and crushed ice produced the smallest change. Conclusions: As administered in our protocol, wetted ice was superior to cubed or crushed ice at reducing surface temperatures, whereas both cubed ice and wetted ice were superior to crushed ice at reducing intramuscular temperatures. PMID:19295957

  18. Ice stream activity scaled to ice sheet volume during Laurentide Ice Sheet deglaciation

    NASA Astrophysics Data System (ADS)

    Stokes, C. R.; Margold, M.; Clark, C. D.; Tarasov, L.

    2016-02-01

    The contribution of the Greenland and West Antarctic ice sheets to sea level has increased in recent decades, largely owing to the thinning and retreat of outlet glaciers and ice streams. This dynamic loss is a serious concern, with some modelling studies suggesting that the collapse of a major ice sheet could be imminent or potentially underway in West Antarctica, but others predicting a more limited response. A major problem is that observations used to initialize and calibrate models typically span only a few decades, and, at the ice-sheet scale, it is unclear how the entire drainage network of ice streams evolves over longer timescales. This represents one of the largest sources of uncertainty when predicting the contributions of ice sheets to sea-level rise. A key question is whether ice streams might increase and sustain rates of mass loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. Here we reconstruct the activity of 117 ice streams that operated at various times during deglaciation of the Laurentide Ice Sheet (from about 22,000 to 7,000 years ago) and show that as they activated and deactivated in different locations, their overall number decreased, they occupied a progressively smaller percentage of the ice sheet perimeter and their total discharge decreased. The underlying geology and topography clearly influenced ice stream activity, but—at the ice-sheet scale—their drainage network adjusted and was linked to changes in ice sheet volume. It is unclear whether these findings can be directly translated to modern ice sheets. However, contrary to the view that sees ice streams as unstable entities that can accelerate ice-sheet deglaciation, we conclude that ice streams exerted progressively less influence on ice sheet mass balance during the retreat of the Laurentide Ice Sheet.

  19. Quantification of Ice Accretions for Icing Scaling Evaluations

    NASA Technical Reports Server (NTRS)

    Ruff, Gary A.; Anderson, David N.

    2003-01-01

    The comparison of ice accretion characteristics is an integral part of aircraft icing research. It is often necessary to compare an ice accretion obtained from a flight test or numerical simulation to one produced in an icing wind tunnel or for validation of an icing scaling method. Traditionally, this has been accomplished by overlaying two-dimensional tracings of ice accretion shapes. This paper addresses the basic question of how to compare ice accretions using more quantitative methods. For simplicity, geometric characteristics of the ice accretions are used for the comparison. One method evaluated is a direct comparison of the percent differences of the geometric measurements. The second method inputs these measurements into a fuzzy inference system to obtain a single measure of the goodness of the comparison. The procedures are demonstrated by comparing ice shapes obtained in the Icing Research Tunnel at NASA Glenn Research Center during recent icing scaling tests. The results demonstrate that this type of analysis is useful in quantifying the similarity of ice accretion shapes and that the procedures should be further developed by expanding the analysis to additional icing data sets.

  20. Modeling Commercial Turbofan Engine Icing Risk With Ice Crystal Ingestion

    NASA Technical Reports Server (NTRS)

    Jorgenson, Philip C. E.; Veres, Joseph P.

    2013-01-01

    The occurrence of ice accretion within commercial high bypass aircraft turbine engines has been reported under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that have been attributed to ice crystal ingestion, partially melting, and ice accretion on the compression system components. The result was degraded engine performance, and one or more of the following: loss of thrust control (roll back), compressor surge or stall, and flameout of the combustor. As ice crystals are ingested into the fan and low pressure compression system, the increase in air temperature causes a portion of the ice crystals to melt. It is hypothesized that this allows the ice-water mixture to cover the metal surfaces of the compressor stationary components which leads to ice accretion through evaporative cooling. Ice accretion causes a blockage which subsequently results in the deterioration in performance of the compressor and engine. The focus of this research is to apply an engine icing computational tool to simulate the flow through a turbofan engine and assess the risk of ice accretion. The tool is comprised of an engine system thermodynamic cycle code, a compressor flow analysis code, and an ice particle melt code that has the capability of determining the rate of sublimation, melting, and evaporation through the compressor flow path, without modeling the actual ice accretion. A commercial turbofan engine which has previously experienced icing events during operation in a high altitude ice crystal environment has been tested in the Propulsion Systems Laboratory (PSL) altitude test facility at NASA Glenn Research Center. The PSL has the capability to produce a continuous ice cloud which are ingested by the engine during operation over a range of altitude conditions. The PSL test results confirmed that there was ice accretion in the engine due to ice crystal ingestion, at the same simulated altitude operating conditions as experienced previously in

  1. Light driven microflow in ice

    SciTech Connect

    Weinert, Franz M.; Wuehr, Max; Braun, Dieter

    2009-03-16

    We optically pump water through micrometer thin ice sheets. The ice is locally moved with speeds exceeding 5 cm/s by repetitive melting and freezing, which occurs around a moving infrared laser spot. The minimal channel width is 10 {mu}m. The diffusion limitation of ice allows for fast spatial biomolecule control without predefined channels, valves, or external pumps. Dye molecules are pumped across an ice-ice interface, showing the possibility of microfluidic applications. Pumping in ice is three orders of magnitude faster than the previously shown for thermoviscous pumping in water.

  2. Physicochemical control of bacterial and protist community composition and diversity in Antarctic sea ice.

    PubMed

    Torstensson, Anders; Dinasquet, Julie; Chierici, Melissa; Fransson, Agneta; Riemann, Lasse; Wulff, Angela

    2015-10-01

    Due to climate change, sea ice experiences changes in terms of extent and physical properties. In order to understand how sea ice microbial communities are affected by changes in physicochemical properties of the ice, we used 454-sequencing of 16S and 18S rRNA genes to examine environmental control of microbial diversity and composition in Antarctic sea ice. We observed a high diversity and richness of bacteria, which were strongly negatively correlated with temperature and positively with brine salinity. We suggest that bacterial diversity in sea ice is mainly controlled by physicochemical properties of the ice, such as temperature and salinity, and that sea ice bacterial communities are sensitive to seasonal and environmental changes. For the first time in Antarctic interior sea ice, we observed a strong eukaryotic dominance of the dinoflagellate phylotype SL163A10, comprising 63% of the total sequences. This phylotype is known to be kleptoplastic and could be a significant primary producer in sea ice. We conclude that mixotrophic flagellates may play a greater role in the sea ice microbial ecosystem than previously believed, and not only during the polar night but also during summer when potential food sources are abundant.

  3. Transposase-Mediated Excision, Conjugative Transfer, and Diversity of ICE6013 Elements in Staphylococcus aureus.

    PubMed

    Sansevere, Emily A; Luo, Xiao; Park, Joo Youn; Yoon, Sunghyun; Seo, Keun Seok; Robinson, D Ashley

    2017-04-15

    ICE6013 represents one of two families of integrative conjugative elements (ICEs) identified in the pan-genome of the human and animal pathogen Staphylococcus aureus Here we investigated the excision and conjugation functions of ICE6013 and further characterized the diversity of this element. ICE6013 excision was not significantly affected by growth, temperature, pH, or UV exposure and did not depend on recA The IS30-like DDE transposase (Tpase; encoded by orf1 and orf2) of ICE6013 must be uninterrupted for excision to occur, whereas disrupting three of the other open reading frames (ORFs) on the element significantly affects the level of excision. We demonstrate that ICE6013 conjugatively transfers to different S. aureus backgrounds at frequencies approaching that of the conjugative plasmid pGO1. We found that excision is required for conjugation, that not all S. aureus backgrounds are successful recipients, and that transconjugants acquire the ability to transfer ICE6013 Sequencing of chromosomal integration sites in serially passaged transconjugants revealed a significant integration site preference for a 15-bp AT-rich palindromic consensus sequence, which surrounds the 3-bp target site that is duplicated upon integration. A sequence analysis of ICE6013 from different host strains of S. aureus and from eight other species of staphylococci identified seven divergent subfamilies of ICE6013 that include sequences previously classified as a transposon, a plasmid, and various ICEs. In summary, these results indicate that the IS30-like Tpase functions as the ICE6013 recombinase and that ICE6013 represents a diverse family of mobile genetic elements that mediate conjugation in staphylococci.IMPORTANCE Integrative conjugative elements (ICEs) encode the abilities to integrate into and excise from bacterial chromosomes and plasmids and mediate conjugation between bacteria. As agents of horizontal gene transfer, ICEs may affect bacterial evolution. ICE6013 represents one

  4. Protein Stability in Ice

    PubMed Central

    Strambini, Giovanni B.; Gonnelli, Margherita

    2007-01-01

    This study presents an experimental approach, based on the change of Trp fluorescence between native and denatured states of proteins, which permits to monitor unfolding equilibria and the thermodynamic stability (ΔG°) of these macromolecules in frozen aqueous solutions. The results obtained by guanidinium chloride denaturation of the azurin mutant C112S from Pseudomonas aeruginosa, in the temperature range from −8 to −16°C, demonstrate that the stability of the native fold may be significantly perturbed in ice depending mainly on the size of the liquid water pool (VL) in equilibrium with the solid phase. The data establish a threshold, around VL = 1.5%, below which in ice ΔG° decreases progressively relative to liquid state, up to 3 kcal/mole for VL = 0.285%. The sharp dependence of ΔG° on VL is consistent with a mechanism based on adsorption of the protein to the ice surface. The reduction in ΔG° is accompanied by a corresponding decrease in m-value indicating that protein-ice interactions increase the solvent accessible surface area of the native fold or reduce that of the denatured state, or both. The method opens the possibility for examining in a more quantitative fashion the influence of various experimental conditions on the ice perturbation and in particular to test the effectiveness of numerous additives used in formulations to preserve labile pharmaco proteins. PMID:17189314

  5. Mysteries at Ice Interfaces

    NASA Astrophysics Data System (ADS)

    Fain, Samuel C., Jr.

    1996-03-01

    Michael Faraday noted that ``two pieces of thawing ice, if put together, adhere and become one...the effect will take place in air, or in water, or in vacuo." Why? He proposed that ``a particle of water, which could retain the liquid state whilst touching ice only on one side, could not retain the liquid state if it were touched by ice on both sides."footnote M. Faraday, Proc. Roy. Soc. London 10, 440 (1860) The existence of special properties at interfaces of ice is generally agreed and has important environmental consequences.(J. G. Dash, H. Fu, and J. S. Wettlaufer, Rep. Prog. Phys. 58), 115 (1995) Why do different experiments infer different properties for this layer? Impurities and electric fields at the interfaces may be responsible for some of the variations in experimental results.footnote V. F. Petrenko, U. S. Army Cold Regions Research and Engineering Laboratory Report 94-22 (1994) Some background on the physical properties of ice will be discussed, including recent force microscopy measurements done at the University of Washington.footnote C.R. Slaughterbeck, E.W. Kukes, B. Pittenger, D.J. Cook, P.C. Williams, V.L. Eden, S.C. Fain, Jr., J. Vac. Sci. Technol. (in press) Supported by NSF Grant DMR-91-19701.

  6. Data archaeology at ICES

    NASA Technical Reports Server (NTRS)

    Dooley, Harry D.

    1992-01-01

    This paper provides a brief overview of the function of the International Council for the Exploration of the Sea (ICES), both past and present, in particular in the context of its interest in compiling oceanographic data sets. Details are provided of the procedures it adopted to ensure adequate internationally collaborative marine investigations during the first part of the century, such as how it provided a forum for action by its member states, how it coordinated and published the results of scientific programs, and how it provided a foundation, through scientists employed in the ICES Office, for the establishment of the original oceanographic marine databases and associated products, and the scientific interpretation of the results. The growth and expansion of this area of ICES activity is then traced, taking into account the changing conditions for oceanographic data management resulting from the establishment of the National Data Centres, as well as the World Data Centres for Oceanography, which were created to meet the needs of the International Geophysical Year (IGY). Finally, there is a discussion of the way in which the very existence of ICES has proved to be a valuable source of old data, some of which have not yet been digitized, but which can be readily retrieved because they have been very carefully documented throughout the years. Lessons from this activity are noted, and suggestions are made on how the past experiences of ICES can be utilized to ensure the availability of marine data to present and future generations of scientists.

  7. Inception of ice accretion by ice crystal impact

    NASA Astrophysics Data System (ADS)

    Löwe, Jens; Kintea, Daniel; Baumert, Arne; Bansmer, Stephan; Roisman, Ilia V.; Tropea, Cameron

    2016-09-01

    In this experimental and theoretical study the ice accretion phenomena on a heated cylinder in Braunschweig Icing Wind Tunnel are investigated. The ice crystal size, velocity, the liquid-to-total mass ratio are accurately controlled. The evolution of the cylinder temperature, the time required for the inception of the ice accretion, and the ice accretion rate are measured for various operating conditions. The surface temperature of the solid target is determined by balancing the heating power in the wall and the cooling effect of the stream of ice particles. We have discovered that the inception of the ice crystal accretion is determined by the instant when the surface temperature of the heated target reduces to the freezing temperature. This result will help to model the phenomena of ice crystal accretion.

  8. Ice nucleation by plant structural materials and its potential contribution to glaciation in clouds

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Hoose, C.; Järvinen, E.; Kiselev, A. A.; Moehler, O.; Schnaiter, M.; Ullrich, R.; Cziczo, D. J.; Felgitsch, L.; Gourihar, K.; Grothe, H.; Reicher, N.; Rudich, Y.; Tobo, Y.; Zawadowicz, M. A.

    2015-12-01

    Glaciation of supercooled clouds through immersion freezing is an important atmospheric process affecting the formation of precipitation and the Earth's energy budget. Currently, the climatic impact of ice-nucleating particles (INPs) is being reassessed due to increasing evidence of their diversity and abundance in the atmosphere as well as their ability to influence cloud properties. Recently, it has been found that microcrystalline cellulose (MCC; extracted from natural wood pulp) can act as an efficient INP and may add crucial importance to quantify the role of primary biological INP (BINP) in the troposphere. However, it is still unclear if the laboratory results of MCC can be representatively scaled up to the total cellulose content in the atmosphere to assess the overall role of BINPs in clouds and the climate system. Here, we use the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud simulation chamber in Karlsruhe, Germany to demonstrate that several important plant constituents as well as natural plant debris can act as BINPs in simulated super-cooled clouds of the lower and middle troposphere. More specifically, we measured the surface-scaled ice nucleation activity of a total 16 plant structural materials (i.e., celluloses, lignins, lipids and carbohydrates), which were dispersed and immersed in cloud droplets in the chamber, and compared to that of dried leaf powder as a model proxy for atmospheric BINPs. Using these surface-based activities, we developed parameters describing the ice nucleation ability of these particles. Subsequently, we applied them to observed airborne plant debris concentrations and compared to the background INP simulated in a global aerosol model. Our results suggest that cellulose is the most active BINPs amongst the 16 materials and the concentration of ice nucleating cellulose and plant debris to become significant (>0.1 L-1) below about -20 ˚C. Overall, our findings support the view that MCC may be a good proxy

  9. On the ice nucleation spectrum

    NASA Astrophysics Data System (ADS)

    Barahona, D.

    2012-04-01

    This work presents a novel formulation of the ice nucleation spectrum, i.e. the function relating the ice crystal concentration to cloud formation conditions and aerosol properties. The new formulation is physically-based and explicitly accounts for the dependency of the ice crystal concentration on temperature, supersaturation, cooling rate, and particle size, surface area and composition. This is achieved by introducing the concepts of ice nucleation coefficient (the number of ice germs present in a particle) and nucleation probability dispersion function (the distribution of ice nucleation coefficients within the aerosol population). The new formulation is used to generate ice nucleation parameterizations for the homogeneous freezing of cloud droplets and the heterogeneous deposition ice nucleation on dust and soot ice nuclei. For homogeneous freezing, it was found that by increasing the dispersion in the droplet volume distribution the fraction of supercooled droplets in the population increases. For heterogeneous ice nucleation the new formulation consistently describes singular and stochastic behavior within a single framework. Using a fundamentally stochastic approach, both cooling rate independence and constancy of the ice nucleation fraction over time, features typically associated with singular behavior, were reproduced. Analysis of the temporal dependency of the ice nucleation spectrum suggested that experimental methods that measure the ice nucleation fraction over few seconds would tend to underestimate the ice nuclei concentration. It is shown that inferring the aerosol heterogeneous ice nucleation properties from measurements of the onset supersaturation and temperature may carry significant error as the variability in ice nucleation properties within the aerosol population is not accounted for. This work provides a simple and rigorous ice nucleation framework where theoretical predictions, laboratory measurements and field campaign data can be

  10. On the Ice Nucleation Spectrum

    NASA Technical Reports Server (NTRS)

    Barahona, D.

    2012-01-01

    This work presents a novel formulation of the ice nucleation spectrum, i.e. the function relating the ice crystal concentration to cloud formation conditions and aerosol properties. The new formulation is physically-based and explicitly accounts for the dependency of the ice crystal concentration on temperature, supersaturation, cooling rate, and particle size, surface area and composition. This is achieved by introducing the concepts of ice nucleation coefficient (the number of ice germs present in a particle) and nucleation probability dispersion function (the distribution of ice nucleation coefficients within the aerosol population). The new formulation is used to generate ice nucleation parameterizations for the homogeneous freezing of cloud droplets and the heterogeneous deposition ice nucleation on dust and soot ice nuclei. For homogeneous freezing, it was found that by increasing the dispersion in the droplet volume distribution the fraction of supercooled droplets in the population increases. For heterogeneous ice nucleation the new formulation consistently describes singular and stochastic behavior within a single framework. Using a fundamentally stochastic approach, both cooling rate independence and constancy of the ice nucleation fraction over time, features typically associated with singular behavior, were reproduced. Analysis of the temporal dependency of the ice nucleation spectrum suggested that experimental methods that measure the ice nucleation fraction over few seconds would tend to underestimate the ice nuclei concentration. It is shown that inferring the aerosol heterogeneous ice nucleation properties from measurements of the onset supersaturation and temperature may carry significant error as the variability in ice nucleation properties within the aerosol population is not accounted for. This work provides a simple and rigorous ice nucleation framework where theoretical predictions, laboratory measurements and field campaign data can be

  11. Seafloor Control on Sea Ice

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Clemente-Colon, P.; Rigor, I. G.; Hall, D. K.; Neumann, G.

    2011-01-01

    The seafloor has a profound role in Arctic sea ice formation and seasonal evolution. Ocean bathymetry controls the distribution and mixing of warm and cold waters, which may originate from different sources, thereby dictating the pattern of sea ice on the ocean surface. Sea ice dynamics, forced by surface winds, are also guided by seafloor features in preferential directions. Here, satellite mapping of sea ice together with buoy measurements are used to reveal the bathymetric control on sea ice growth and dynamics. Bathymetric effects on sea ice formation are clearly observed in the conformation between sea ice patterns and bathymetric characteristics in the peripheral seas. Beyond local features, bathymetric control appears over extensive ice-prone regions across the Arctic Ocean. The large-scale conformation between bathymetry and patterns of different synoptic sea ice classes, including seasonal and perennial sea ice, is identified. An implication of the bathymetric influence is that the maximum extent of the total sea ice cover is relatively stable, as observed by scatterometer data in the decade of the 2000s, while the minimum ice extent has decreased drastically. Because of the geologic control, the sea ice cover can expand only as far as it reaches the seashore, the continental shelf break, or other pronounced bathymetric features in the peripheral seas. Since the seafloor does not change significantly for decades or centuries, sea ice patterns can be recurrent around certain bathymetric features, which, once identified, may h