Ice Abundance Research Articles

Investigations of internal structure and transformational processes from firn to ice in a perennial snow patch

To investigate the internal structure and transformational processes from firn to ice of the Hisago snow patch on Daisetsu Mountain, Hokkaido, Japan, many drillings were made during the ablation period in 1986 and 1987. The ice cores were analyzed for stratigraphy, density and free water content. The internal structure of the snow patch was characterized by a wet firn layer with abundant ice layers and ice glands overlying a 4.3 m-thick ice body. The thickness of the firn layer varied from 12.7 m in June to 1.3 m in October. A water-saturated firn layer about 1 m thick existed just above the firn-ice transition. The annual layers were identified by dirt layers which showed that 1–2 m of ice was formed each year when the mass budget was positive. Although the densification of the water-saturated firn layer proceeded rapidly, the transformation from firn to ice could not be recognized during the ablation period. It was concluded that the formation mechanism of the ice body comprised three processes: the formation of superimposed ice, the densification of a water-saturated firn layer and the freezing of wet and/or water-saturated firn by cold wave penetration.

Investigations of internal structure and transformational processes from firn to ice in a perennial snow patch

To investigate the internal structure and transformational processes from firn to ice of the Hisago snow patch on Daisetsu Mountain, Hokkaido, Japan, many drillings were made during the ablation period in 1986 and 1987. The ice cores were analyzed for stratigraphy, density and free water content. The internal structure of the snow patch was characterized by a wet firn layer with abundant ice layers and ice glands overlying a 4.3 m-thick ice body. The thickness of the firn layer varied from 12.7 m in June to 1.3 m in October. A water-saturated firn layer about 1 m thick existed just above the firn-ice transition. The annual layers were identified by dirt layers which showed that 1–2 m of ice was formed each year when the mass budget was positive. Although the densification of the water-saturated firn layer proceeded rapidly, the transformation from firn to ice could not be recognized during the ablation period. It was concluded that the formation mechanism of the ice body comprised three processes: the formation of superimposed ice, the densification of a water-saturated firn layer and the freezing of wet and/or water-saturated firn by cold wave penetration.

On the Possible Detection of Solid O2 in Interstellar Grains

In various models of the chemistry of interstellar grains, solid O2 is formed by accretion as well as by surface reactions. In dense molecular cloud models, at a later stage of evolution of an interstellar grain, solid O2 becomes a major grain mantle constituent at the expense of water ice abundance. If molecular oxygen is embedded in a “dirty” ice” matrix, the forbidden fundamental vibration of O2 at 1550 cm−1 may become observable.

Ice sublimation and rheology: Implications for the Martian polar layered deposits

It has been suggested that the Martian polar layered deposits are composed largely of water ice. If true, then sublimation and deformation creep of the ice are important processes. Simple models indicate that sublimation will occur at a rate inconsistent with current estimates of the deposit's age and Viking observations of the atmospheric water abundance, suggesting that when considering the formation, evolution, and structure of the deposits, one must include a mechanism by which sublimation is inhibited. A surface layer of dust seems the most likely possibility. Additionally, over the age of the deposits, flows of at least 1 km are expected. At Viking resolution (⩾150 m) no obvious flow features are observed. Assuming that Martian features would be similar to those that occur on the Earth, this limits the maximum flow rates possible and suggest the deposits need to be more than 90% ice or less than about 40% ice by volume. The Mars Observer spacecraft will be able to constrain the ice abundance further by both searching for flow features and clarifying the nature of the deposit's surface and near surface.

Trophic relationships of the sea ice meiofauna in Frobisher Bay, Arctic Canada

A distinct fauna consisting mainly of nematodes, harpacticoid and cyclopoid copepods, rotifers, turbellarians and polychaete larvae, inhabits the lower levels of the sea ice in Frobisher Bay. Similar faunas are found throughout circumpolar regions. Thirteen taxa of the Frobisher Bay ice fauna were entirely herbivorous. Their food consisted of 26 genera of algae dominated by Chlamydomonas, Nitzschia, Navicula and Chaetoceros. There was a clear tendency to feed on the most abundant ice algae, hence little evidence of selective feeding. High algal food concentrations in the ice (estimated at 5000 μg C/l) were in sharp contrast with the scant nourishment available from phytoplankton under the ice (8 μg C/l) from mid-winter until the start of the summer bloom. Algal stocks and estimated productivity rates indicate that ice meiofaunal food requirements may be met by the ice algae. All the major ice meiofaunal species are well adapted to feeding within the ice. All are small enough to enter brine channels and secure particulate prey from surfaces within confined spaces. The ice meiofaunal species are major consumers of the ice algae and therefore important links in the transfer of energy from the ice to pelagic and benthic predators, including fishes, birds and mammals.

Pluto's atmosphere near perihelion

A recent stellar occultation has confirmed predictions that Pluto has an atmosphere which is sufficiently thick to uniformly envelope the planet and to extend far above the surface. Pluto's atmosphere consists of methane and perhaps other volatile gases at temperatures below their freezing points; it should regulate the surface temperature of its volatile ices to a globally uniform value. As Pluto approaches and passes through perihelion, a seasonal maximum in the atmospheric bulk and a corresponding minimum in the exposed volatile ice abundance is expected to occur. The lag in maximum atmospheric bulk relative to perihelion will be diagnostic of the surface thermal properties. An estimate of Pluto's atmospheric bulk may result if a global darkening (resulting from the disappearance of the seasonally deposited frosts) occurs before the time of maximum atmospheric bulk. The ice deposited shortly after perihelion may be diagnostic of the composition of Pluto's volatile reservoir.

Dendroecological evidence of lake-level changes during the last three centuries in subarctic Québec

Dendroecological analysis of black spruces ( Picea mariana (Mill.) BSP.) near the shore of Clearwater Lake in the eastern Canadian subarctic yielded information on water level over the past three centuries. Tree positions, growth froms, layering, tree ring patterns, and ice scars provide direct evidence of a major rise in lake level. From the 17th century to the present, trees on the lake shore were progressively submerged by the increasing water level, which reached a maximum in this century. Higher levels began around the mid-18th century when shoreline spruce trees started to lean because extensive wave erosion caused landward shore displacement. High mortality of leaning spruce and abundant ice scar formation occurred during this century. The rise in water level in inferred to have been caused by snowier winters occurring parallel to climatic warming.

Observations of sea ice influence on the littoral sediment exchange, North Zealand, Denmark

Nielsen, Niels: Observations of sea ice influence on the littoral sediment exchange, North Zealand, Denmark. Geografisk Tidsskrift 88:61–67. Copenhagen. 1988. In 1985 and 1986 monthly surveys of sediment volumes were carried out on a sandy beach and its nearshore platform at the north coast of Zealand. Both winters in the research period had temperatures below average, and consequently abundant sea ice formations. ‘Ice winters’ in open Danish waters occur statistically about 1/3 of the winters. The appearance of sea ice resulted in marked loss of sediment from the whole littoral zone, but by far the largest net erosion could be detected on the nearshore plane. An important factor is assumed to be the interaction of waves with the icefoot and ice pile-ups. For the beach itself, ice-glazing of the beach surface and interstitial frost in the foreshore sediments caused wave erosion within and just off the swash zone due to variations of the percolation parameter. This dynamic was observed during both the free...

Icy Galilean satellite reflectance spectra: Less ice on Ganymede and Callisto?

Recent interpretations of the reflectance spectra of the icy Galilean satellites (Europa, Ganymede, and Callisto) have implied very ice-rich surfaces, as high as 90 wt% ice even on the dark surface of Callisto. A reevaluation of the spectra, taking into account the depth of the 3-μm fundamental water ice absorption feature as well as the shorter wavelength bands, suggests that the spectra of at least Ganymede and Callisto may also be consistent with much lower ice abundances if the ice is segregated from the nonicy material. Reasonable fits to all band depths (including the shallow 1.04- and 1.25-μm bands) are obtained with around 50% areal coverage of ice on Ganymede and 10% on Callisto, the rest of the surface being occupied by carbonaceous chondrite-like material which has a strong 3-μm absorption due to bound water. Europa's spectrum probably indicates a homogeneous icy surface. The darkness beyond 3 μm, and lack of a 3.6-μm peak, for all three objects may be consistent with the presence of small quantities of sulfuric acid on the satellite surfaces.

Diatom flux in McMurdo Sound, Antarctica

Quantitative floral analyses have been performed on sea ice, sediment trap, and surface sediment samples collected from six sites in McMurdo Sound, Antarctica. Although diatom abundances in the sea ice reach 10 8–10 9 cells m −2, maximum diatom fluxes between October–December, 1984, as measured in the sediment trap samples, are only 10 5–10 7 individuals m −2 day −1. The cumulative flux of diatoms for this three month period is approximately 10 7–10 9 individuals m −2, possibly an order of magnitude less than the sea ice abundances, implying that diatom and opal flux must significantly increase when the sea ice melts and releases those particles previously trapped in the ice. Five species dominate the sea ice assemblage - Amphiprora sp., Pleurosigma sp., Nitzschia stellata, Pinnularia quadratarea, and Nitzschia curta. These species are also common in the water column, along with Thalassiosira spp., a genus rarely found within the sea ice. Within the upper 250 m of the water column, at a site in Granite Harbor, diatom flux decreases between 47–79% from 34 to 220 m. Opal flux, however, decreases by only 13–40% over this same interval, indicating that dissolution of thinly silicified diatom frustules has occurred. At mid-water depths, increases in absolute diatom flux of two species in particular, Nitzschia curta and Thalassiosira spp., may indicate their transport from other areas. At all sites, the greatest increase in diatom flux occurs just above the sea floor. Resuspension of diatom tests and/or lateral advection creates a near-bottom nepheloid layer in which significant modification of the diatom assemblage occurs. A combination of preferential dissolution of those forms which dominate the sea ice and dilution of the assemblage with resuspended and/or advected diatoms representative of many year averages of the flora may be responsible for the production of a sediment assemblage primarily made up of Thalassiosira spp., Nitzschia curta, and other robust forms of Nitzschia.

Ice-lubricated gravity spreading of the Olympus Mons aureole deposits

Gravity sliding and spreading at low strain rates can account for the general morphology and structure of the aureoles and basal scarp of Olympus Mons. Detachment sliding could have occurred around the volcano if either pore-fluid pressures were exceptionally high (greater than 90%) or the rocks had very low resistance to shear (about 1 × 10 5 Pa or 1 bar). Because of the vast areal extent and probable shallow depth of the detachment zone, development of ubiquitous, high pore-fluid pressures beneath aureole-forming material was unlikely. However, a zone of sufficiently weak material consisting of about 10% interstitial or interbedded ice could have been present. If so, a simple rheologic model for the aureole deposits can be applied that consists of a thin ductile layer overlain by a thicker brittle layer. According to this model, extensional deformation would have occurred near the shield and compressional deformation in its distal parts. Proximal grabens and distal corrugations on aureole surfaces support this model. A submarine slide at Kitimat Arm, British Columbia, is a valid qualitative analogy for the observed features and inferred emplacement style of the aureole deposits. Ground-ice processes have been considered the cause of many geologic features on Mars; a 3% average concentration of ground ice in the regolith is predicted by theoretical models for the ice budget and cryosphere. Ice may have been deposited in higher concentrations below the aureole-forming material; the source of the ice could have been juvenile water circulated hydrothermally by Olympus Mons volcanism. The basal scarp of Olympus Mons apparently demarcates the transition between the upper, stable part of the shield and its lower part that decoupled and formed the aureole deposits. This transition may reflect a change in the bulk shear strength of the shield, caused either by a radial dependence in the abundance of ice or fluid in the shield materials or by the concentration of intrusive dikes within the volcano. Other Martian volcanoes exhibit virtually no evidence of similar large-scale gravity spreading and basal scarps. Perhaps such evidence, if it existed, has been buried by lava flows, or perhaps the smaller size of other volcanoes did not permit the development of these features.

The Sea Ice Fauna of Frobisher Bay Arctic Canada

The fauna of the lower few centimetres of the sea ice in Frobisher Bay, Arctic Canada, consists mainly of meroplanktonic young of benthic adults and holoplanktonic representatives of generally benthic groups. The major arctic zooplankton species are not included. The ice fauna comprises nematodes, harpacticoid copepods, polychaete larvae, ciliates, various benethic larvae, young gammaridean amphipods, and others. Some species occur in the ice as young animals only, others in all stages of development. Adaptation to the ice is shown best by the copepods, some of which occur there in all stages from egg to adult. The most abundant ice inhabitants reach high concentrations in the ice (nematodes more than 100 000, Cyclopina nearly 10 000/sq m). Others appear to show only accidental presence in the ice, and are found in small numbers only, often at times when great numbers of the same species are present in the water below the ice. Probable feeding of the ice fauna and the food chain linking the ice flora to vertebrate predators are discussed.Key words: arctic waters, sea ice, ice fauna, food chain, zooplankton

Spectral properties of ice‐particulate mixtures and implications for remote sensing: 1. Intimate mixtures

The spectral properties of water ice‐particulate mixtures are studied for the purpose of deriving the ice and particulate abundances from remotely obtained spectra (particulates referring to nonicy materials in the form of grains). Reflectance levels and ice absorption band depths are a complex function of the single scattering albedo of the particulates embedded in the ice. The ice absorption band depths are related to the mean optical path length of photons in ice through Beers law, Fresnel reflection from the ice‐crystal faces on the surface, and ice absorption coefficient as a function of wavelength. Laboratory spectra of many ice‐particulate mixtures are studied with high‐, medium‐, and low‐albedo particulates. From the laboratory spectra the band depth, the continuum reflectance, and the ratio of band depth to continuum reflectance are derived for each particulate albedo as a function of the logarithm of the particulate weight fraction in the sample. Ice band depths are dependent on the particulate albedo and increase with smaller weight fractions of particulates until the bands saturate and their depths decrease. The continuum reflectance is a complex function of the particulate albedo and wavelength of light, while the band depth to continuum reflectance ratio appear independent of particulate albedo such that, for a given grain size of particulate, a calibration curve to abundance of ice and particulates is derived. The derived abundance calibrations are accurate if the source of scattering is dominated by particulates and not ice‐vacuum (air) interfaces. If ice‐vacuum interfaces are dominant, then the derived particulate abundance is an upper limit. Theoretically produced frost spectra show similar curves of growth of band depth, continuum reflectance, and corresponding ratio versus the photon mean optical path length similar to that for intimate mixtures of ice and high‐albedo particulates. In all scattering cases the ice absorption coefficients determine the path length needed to produce a given band depth; thus different absorptions are sensitive to different amounts of particulates, with the 3‐μm fundamental being the most sensitive to the presence of ice (very low ice abundance) and the 1.04‐μm overtone being the most sensitive to the presence of particulates (very high ice abundance).

The Moons of Saturn

Knowledge gained of the 17 Saturn moons with observations by the Voyager spacecraft are reviewed. Titan was found to have the only atmosphere, which is opaque and precludes geologic inferences. Synchronous rotation is experienced by the 14 inner moons, with a constant inner face turned toward the planet. Phoebe is too far away from the planet to lose its spin to planetary tidal forces, and has an orbit inclined 150 deg from the equatorial plane, while Iapetus is inclined 14.7 deg in its orbit. The abundance of ice on the moons is accepted as evidence of condensation formation of the moons at very low temperatures. Newly discovered moons of Saturn, including both the shepherd moons, which are suspected to maintain the rings in place, and the moons discovered by earth-based astronomy, are discussed. Finally, photographs of all the moons are examined for definitive details.

The eruptive evolution of the Galilean satellites: Implications for the ancient magnetic field of Jupiter

The hypothesis considering the Jupiter-Sun system as a limiting case of a close binary star implies the initial relative ice abundances in all the Galilean satellites to be essentially equal. The satellites move in the Jovian magnetosphere; thus the unipolar current flowing through their bodies subjected their ices to volumetric electrolysis. Explosions of the electrolysis products resulted in a loss of ices. While Callisto did not explode at all, Ganymede exploded once, Europa twice, and Io two or three times.

On the excitation of interstellar ammonia in the Kleinmann-Low nebula

view Abstract Citations (61) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the excitation of interstellar ammonia in the Kleinmann-Low nebula. Sweitzer, J. S. Abstract Investigations of the region in which NH3 lines are formed in the direction of the Kleinmann-Low nebula are reported. A non-LTE model, including the transfer of both the line radiation and the dust-generated continuum radiation, was constructed to study the excitation of the lowest 31 levels of NH3. Agreement between the model and the observations is excellent. The model implies relatively high densities (of the order of 1 million H2 molecules/cu cm) and temperatures (about 70 K) for the line formation region. These results further imply that the lines come from a small (about 16 arcsec) core with an optical depth of approximately 0.02 in the dust continuum at 250 microns. The problem of the NH3 line shapes is also studied, and a relative NH3 abundance of approximately 5 ten-millionths is derived, which is a factor of about 1000 higher than ion-molecule predictions. This abundance is, however, consistent with the abundance of NH3 ice on grains seen toward the BN object if the interpretation of the 3-micron feature as H2O and NH3 ices is correct. It is suggested that the extreme NH3 clumping implied by the 16-arcsec core may be due to evaporation of NH3 from grains in the Kleinmann-Low nebula. Publication: The Astrophysical Journal Pub Date: October 1978 DOI: 10.1086/156473 Bibcode: 1978ApJ...225..116S Keywords: Ammonia; Interstellar Gas; Molecular Excitation; Nebulae; Abundance; Astronomical Models; Collision Rates; Energy Levels; Hyperfine Structure; Iterative Solution; Line Shape; Thermodynamic Equilibrium; Astrophysics; Ammonia:Interstellar Matter; Ammonia:Kleinmann-Low Nebula full text sources ADS |

Aerosols and Polar Temperature Changes

Calculations indicate that aerosols are not directly responsible for the present increase in ice abundance in the Northern Hemisphere. Indeed it appears that aerosols cause heating of the atmosphere near the poles. The present background aerosol density at 85 degrees S latitude causes a temperature increase of approximately 0.2 degrees K, while that at 85 degrees N causes an increase of approximately 0.05 degrees K.

THE WORLD OF UNDERGROUND ICE

ABSTRACT Underground ice is restricted to permafrost areas where its distribution is sporadic and often unpredictable. A knowledge of the distribution and abundance of underground ice is essential to northern development, because a variety of man induced disturbances can cause underground ice to thaw, often with serious consequences. The criteria for a classification of the principal types of underground ice are the source of the water prior to freezing and the processes which transfer water to the freezing plane. The origin of massive icy bodies in the Western Arctic of North America is explained by a water expulsion theory. The excess water now found in the icy bodies is attributed to water expelled from coarse textured sediments by the downward growth of permafrost. The suggested mechanism is illustrated by three pingos which have grown since 1950. The role of glaciation in the formation of relic offshore permafrost in relatively shallow Arctic coastal areas is examined. The evidence suggests that offs...

Isotope Effects in the 77°K γ Irradiation of Ice

The radiation yields of H2, D2, and HD obtained by the 77°K γ irradiation of solute-free mixed H2O and D2O ice mixtures have been determined by use of mass spectroscopy. The total gas yields have been determined, too, both by use of a calibrated mass spectrometer and by manometric methods. Significant isotope effects were observed over a wide range of the isotopic compositions studied (i.e., the deuterium content varied from ∼0.016% to 99.8%). The separation factor αG=(H/D)gas(H/D)icevaried from about 70 for the high D content ice to about 1.0 for natural isotopic abundance ice. At (H/D)ice=1.0, αG is 1.7. Values of αG were obtained for 99.80% D2O over a temperature range of 4.2° to 196°K. The separation factor was found to be inversely proportional to temperature. The results of this study are compared with those in a previously published EPR study of stabilized H and D atoms after irradiation at 4.2°K. The observed effects are discussed briefly in terms of several models of selective energy absorption.

Airglow of Venus: a re-examination

Rhea is the second largest icy satellites of Saturn and it is mainly composed of water ice. Its surface is characterized by a leading hemisphere slightly brighter than the trailing side. The main goal of this work is to identify homogeneous compositional units on Rhea by applying the Spectral Angle Mapper (SAM) classification technique to Rhea’s hyperspectral images acquired by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini Orbiter in the infrared range (0.88–5.12 μm). The first step of the classification is dedicated to the identification of Rhea’s spectral endmembers by applying the k-means unsupervised clustering technique to four hyperspectral images representative of a limited portion of the surface, imaged at relatively high spatial resolution. We then identified eight spectral endmembers, corresponding to as many terrain units, which mostly distinguish for water ice abundance and ice grain size. In the second step, endmembers are used as reference spectra in SAM classification method to achieve a comprehensive classification of the entire surface. From our analysis of the infrared spectra returned by VIMS, it clearly emerges that Rhea’ surface units shows differences in terms of water ice bands depths, average ice grain size, and concentration of contaminants, particularly CO2 and hydrocarbons. The spectral units that classify optically dark terrains are those showing suppressed water ice bands, a finer ice grain size and a higher concentration of carbon dioxide. Conversely, spectral units labeling brighter regions have deeper water ice absorption bands, higher albedo and a smaller concentration of contaminants. All these variations reflect surface’s morphological and geological structures. Finally, we performed a comparison between Rhea and Dione, to highlight different magnitudes of space weathering effects in the icy satellites as a function of the distance from Saturn.