bluuebunny/crossref_metadata_2025 huggingface dataset:
OPERACIONES DEL EJÉRCITO MEXICANO CONTRA EL TRÁFICO DE DROGAS:REVISIÓN Y ACTUALIDAD
Authors: Mendoza Cortés Paloma
Published: September 2017

Las políticas gubernamentales de las que se desprenden las operaciones del Ejército mexicano contra el tráfico de drogas han variado en su magnitud, recursos y facultades jurídicas a  través  del  espacio  y  tiempo,  con  sus  respectivas  responsabilidades  el impacto.  El  presente  documento  se  deriva de la tesis de maestría:“Transformaciones estructural - organizacionales de la Secretaría de la Defensa Nacional:1937 - 2010” que bajo un análisis descriptivo propone llevar a cabo una revisión de las intensificación de las operaciones militares a partir de la identificación del tráfico de drogas como amenaza a la seguridad nacional de México, que se traducen  a  las fecha  en  el  despliegue  nacional  de  las  operaciones  militares  bajo  un  esquema  altamente punitivo  a  falta  de  instituciones civiles  de  seguridad  sólidas  e  incorruptibles, razón por la cual se incentivó la militarización de la seguridad interior  con  consecuencias  negativas  en  las  relaciones  civil militares.
ALGUNAS APROXIMACIONES A LA AGENDA DE LA SEGURIDAD INTERNACIONAL CONTEMPORÁNEA Y LA INFLUENCIA TEÓRICA EN SUS CONTENIDOS
Authors: Bartolomé Mariano César
Published: September 2017

RESUMEN La  Seguridad  Internacional  es  un  campo  específico  de  las  Relaciones  Internacionales  que  en  la  actualidad  muestra  una  sólida  vigencia,  aunque  sus  perfiles  y  límites  son  objeto  de  debate  académico.  En  este  debate  confrontan  visiones  ortodoxas,  fuertemente  apegadas  a  los  modelos  que  emergieron  a  mediados  del  siglo  XVII  con  la  llamada  Paz  de  Westfalia,  con  otras  más  flexibles  surgidas  en  las  últimas  cuatro  décadas.  Las  primeras  abordan  al  tablero  mundial  en  clave  únicamente  estatal,  observando  vinculaciones  interestatales  con  claro  predominio  del  poder  militar;  las  segundas,  alegando  un  mayor  respaldo  empírico,  admiten  diversos  tipos  de  actores,  dinámicas  y  temas.  Con  ese  contexto,  los  objetivos  del  presente  trabajo  consisten  en  describir  algunos  de  los  aspectos  más  representativos  del  mencionado  contrapunto  entre  las  visiones  clásicas  y  las  lecturas  heterodoxas  que  no  se  ciñen  a  los  esquemas  westfalianos,  como  así  también  repasar  algunas  aristas  de  la  agenda  contemporánea  de  la  Seguridad  Internacional,  indicando  el  sustento  teórico  de  los  heterogéneos  contenidos  que  ha  venido  incorporando  en  los  últimos  tiempos.  A  tal  efecto,  en  primer  lugar  describiremos  cómo  ha  mutado  la  fisonomía  y  se  han  ampliado  los  límites  de  esa  agenda,  para  luego  consignar  algunos  efectos  de  ese  proceso,  finalizando  con  unas  breves  conclusiones  y  tendencias.  Desde  un  punto  de vista metodológico, el presente trabajo propone un abordaje  de  tipo  deductivo  al  objeto  de  estudio,  evolucionando  desde  enfoques  generales  hacia  planos  de  mayor  especificidad;  el análisis alternará entre los niveles descriptivo y explicativo, con  empleo de fuentes secundarias y datos cualitativos.
Editorial
Authors: Soto Silva Julio
Published: September 2017

Iniciando el segundo semestre del año, el mundo sigue con atención los problemas que se han originado en Europa derivado de las olas de migraciones masivas que llegan a ese continente provenientes del Cercano Oriente y del norte de África, que han llevado a tomar diferentes medidas para enfrentar esta llamada “amenaza multidimensional”, la que junto con una cadena de atentados terroristas en las principales capitales y otras ciudades europeas, hace crecer la incertidumbre en la población y, a los Gobiernos, diseñar estrategias de seguridad que permitan controlar, prevenir y finalmente mitigar los efectos de estas acciones, dirigidas fundamentalmente a la población, tendientes a infundir caos y terror, también quizás demostrar la incapacidad de los Estados para prevenir estas acciones y crear un ambiente de inseguridad.Por otra parte, los efectos del cambio climático se hacen sentir sobre diferentes regiones del globo, consecuencias de las cuales en nuestro caso no hemos estado ajenos y que han motivado crecientes preocupaciones a nivel global.Las situaciones que existen en el ámbito regional, en un mundo marcado por las ya mencionadas amenazas multidimensionales, nos llevan a visualizar que cada vez es más difícil establecer una línea separatoria entre las materias propias de la seguridad y aquellas de la defensa, tema que centra el debate sobre cómo enfrentar estas nuevas situaciones y si es necesario cambiar los roles que tienen las fuerzas armadas en las actuales circunstancias, aspecto no menor y no exento de polémicas, así como la función que tiene el Estado al momento de preservar el bien común y la protección de la población y recursos que posee.
¿EXISTEN ESTRATEGIAS PARA COMBATIR LAS AMENAZAS MULTIDIMENSIONALES EN LA REGIÓN?
Authors: BANEGAS ALFARO ARACELY
Published: September 2017

Las amenazas multidimensionales, para el Hemisferio Occidental, con especial énfasis, una de ellas, el Crimen Organizado Transnacional, se han convertido en una de las más graves que atentan contra la Seguridad Pública de los Estados, no obstante, no solo es un problema de Seguridad Pública, para algunos países de la Región es un problema de Gobernabilidad. Este artículo desarrolla una aproximación de estudio a la implementación de las estrategias, concertadas por el hemisferio occidental en el marco de la Organización de los Estados Americanos (OEA), para el combate al Crimen Organizado Transnacional y sobre la efectividad de las mismas, teniendo en cuenta las particularidades de sus países miembros, los cuales son asimétricos y desiguales. Así mismo, en el marco de la transición que significó para los países miembros de la OEA, migrar hacia la Seguridad Multidimensional y Cooperativa, se evidencia el consenso sobre los valores compartidos y enfoques comunes, como ser la concepción de la Seguridad de alcance multidimensional, sin embargo, este trabajo, también visibiliza los retos de los países para hacer frente a sus disensos en cuanto a las distintas prioridades y perspectivas nacionales de Seguridad, lo que a veces dificulta el diseño y ejecución de estrategias comunes contra estos  flagelos.
First outbreak of Zika virus in the continental United States: a modelling analysis
Authors: Marini Giovanni , Guzzetta Giorgio , Rosà Roberto , Merler Stefano
Published: September 2017

Since 2015, Zika virus (ZIKV) has spread throughout Latin and Central America. This emerging infectious disease has been causing considerable public health concern because of severe neurological complications, especially in newborns after congenital infections. In July 2016, the first outbreak in the continental United States was identified in the Wynwood neighbourhood of Miami-Dade County, Florida. In this work, we investigated transmission dynamics using a mathematical model calibrated to observed data on mosquito abundance and symptomatic human infections. We found that, although ZIKV transmission was detected in July 2016, the first importation may have occurred between March and mid-April. The estimated highest value for R0was 2.73 (95% confidence interval (CI): 1.65–4.17); the attack rate was 14% (95% CI: 5.6–27.4%), with 15 (95% CI: 6–29) pregnant women involved and a 12% probability of infected blood donations. Vector control avoided 60% of potential infections. According to our results, it is likely that further ZIKV outbreaks identified in other areas of Miami-Dade County were seeded by commuters to Wynwood rather than by additional importation from international travellers. Our study can help prepare future outbreak-related interventions in European areas where competent mosquitoes for ZIKV transmission are already established.
Rethinking the Use of Tests: A Meta-Analysis of Practice Testing
Authors: Adesope Olusola O. , Trevisan Dominic A. , Sundararajan Narayankripa
Published: September 2017

The testing effect is a well-known concept referring to gains in learning and retention that can occur when students take a practice test on studied material before taking a final test on the same material. Research demonstrates that students who take practice tests often outperform students in nontesting learning conditions such as restudying, practice, filler activities, or no presentation of the material. However, evidence-based meta-analysis is needed to develop a comprehensive understanding of the conditions under which practice tests enhance or inhibit learning. This meta-analysis fills this gap by examining the effects of practice tests versus nontesting learning conditions. Results reveal that practice tests are more beneficial for learning than restudying and all other comparison conditions. Mean effect sizes were moderated by the features of practice tests, participant and study characteristics, outcome constructs, and methodological features of the studies. Findings may guide the use of practice tests to advance student learning, and inform students, teachers, researchers, and policymakers. This article concludes with the theoretical and practical implications of the meta-analysis.
Reading on Paper and Digitally: What the Past Decades of Empirical Research Reveal
Authors: Singer Lauren M. , Alexander Patricia A.
Published: September 2017

This systematic literature review was undertaken primarily to examine the role that print and digitally mediums play in text comprehension. Overall, results suggest that medium plays an influential role under certain text or task conditions or for certain readers. Additional goals were to identify how researchers defined and measured comprehension, and the various trends that have emerged over the past 25 years, since Dillon’s review. Analysis showed that relatively few researchers defined either reading or digital reading, and that the majority of studies relied on researcher-developed measures. Three types of trends were identified in this body of work: incremental (significant increase; e.g., number of studies conducted, variety of digital devices used), stationary (relative stability; e.g., research setting, chose of participants), and iterative (wide fluctuation; e.g., text length, text manipulations). The review concludes by considering the significance of these findings for future empirical research on reading in print or digital mediums.
Educational Impacts and Cost-Effectiveness of Conditional Cash Transfer Programs in Developing Countries: A Meta-Analysis
Authors: García Sandra , Saavedra Juan E.
Published: September 2017

We meta-analyze for impact and cost-effectiveness 94 studies from 47 conditional cash transfer programs in low- and middle-income countries worldwide, focusing on educational outcomes that include enrollment, attendance, dropout, and school completion. To conceptually guide and interpret the empirical findings of our meta-analysis, we present a simple economic framework on household decision making that generates predictions, all else constant, for the association between certain program context and design characteristics and impact estimates. We also present a simple model for the analysis of program costs, using it to compute cost-effectiveness estimates for a subsample of programs. For all schooling outcomes, we find strong support for heterogeneity in impact, transfer-effectiveness, and cost-effectiveness estimates. Our meta-analytic results of impact and transfer-effectiveness estimates provide support to some—but not all—of the predictions from the household decision-making model.
Flow Behavior of Basal Ice as Related to Modeling Considerations
Authors: Shoji Hitoshi , Langway Chester C.
Published: September 2017

Simple shear tests on the bottom 17 m of basal ice from Camp Century, Greenland, were carried out in order to study the flow behavior near the bottom of an ice sheet and its implications for ice-sheet modeling. The ice core was recovered in 1966. Our experimental results show that the basal ice tested, (which contained alternating bands of dirty and clean ice) has the highest strain-rate ever reported for polycrystalline ice under simple shear. The enhancement factors obtained are interpreted in terms of fabric, ageing, and impurity. Horizontal velocity profiles are calculated using data reported previously for Camp Century and Dye 3 stations. Various depth-age relationships are compared with these data. The higher than expected shear strain-rates measured on samples of near-bottom ice from Camp Century may very well exist at other locations. If such high shear strain-rates are more prevalent than presently thought, they could have an important bearing on ages calculated by physical or mathematical models of ice sheets.
Lake Sediments as Continental δ18O Records from the Glacial/Post-Glacial Transition
Authors: Siegenthaler U. , Eicher U. , Oeschger H. , Dansgaard W.
Published: September 2017

As in polar ice, 18O variations of precipitation are recorded in carbonate sediments formed in lakes (lake marl). We have analyzed many late-glacial profiles from Europe, There are strong l8O variations which coincide with well-known pollen zone boundaries and which indicate that abrupt, drastic climatic changes occurred in the late glacial period. These events are a major warming around 13 ka BP (pollen zone boundary Oldest Dryas/Bölling) and a marked cold phase between about 10.8 and 10 ka BP (Younger Dryas). Comparison of the δ18O records of European lake sediments and of Greenland ice cores reveal a striking similarity which indicates that climatic changes in the late glacial and early postglacial were parallel in Greenland and in Europe. First results from North American lake-sediment profiles do not exhibit similar δ18O variations. This pattern of climatic changes was probably caused by retreating and readvancing polar water in the high-latitude North Atlantic Ocean, as discussed by Ruddiman and McIntyre (1981).
Transient Temperature Changes Due to Increasing CO2 Using Simple Models
Authors: Siegenthaler U. , Oeschger H.
Published: September 2017

The effect of the oceanic heat capacity on global temperature response to external forcing is studied by considering a CO2-induced warming. The heat flux into the ocean is calculated using a box-diffusion model, earlier established for simulating the global carbon cycle. The calculated transient warming due to CO2 produced by fossil fuel until 1980 is 0.20 to 0. 26K, or about 50% of the value for radiative equilibrium, corresponding to a delay of 16 to 24 years. Analyses of CO2 in ice cores suggest a lower pre-industrial concentration, e.g. 265 ppm, than previously assumed (c. 290 ppm). The transient temperature increase until 1980 calculated for this case is about twice that for a case which starts from 297 ppm. Comparison with observations since 1880 shows that a long-term warming trend might be due to CO2, but the residual scatter unexplained by CO2 is still large. Finally the different thermal behaviour of oceans and continents is accounted for in a schematic way, considering heat exchange between them. The results indicate stronger temperature variations over the continents than over the sea.
Glacier Flexure and the Position of Grounding Lines: Measurements By Tiltmeter on Rutford Ice Stream, Antarctica
Authors: Stephenson S. N.
Published: September 2017

Two methods were used to locate the grounding line on the Rutford Ice Stream. The first method determined where the glacier was floating in hydrostatic equilibrium, while the second method measured the flexing close to the grounding line due to ocean tides. The ratio of surface elevation to ice thickness of the glacier goes through the hydrostatic equilibrium value 1 to 2 km downstream of where tidal flexing was recorded. This behaviour can be explained if the upward pressure of the sea at the base of the ice is augmented by a vertical shear-stress gradient within the glacier to overcome its weight. Simple el as tie-beam theory matches the flexure profile data if a modified elastic modulus and effective thickness are used. Tiltmeters can he used to monitor the position of the grounding line if the geometry of the flexing region can be defined.
Ice-Sheet Modeling
Authors: Weertman J. , Birchfield G. E.
Published: September 2017

This paper presents a review of the ice-sheet mechanics behind the modeling work of Pleistocene ice sheets driven by astronomical (Milankovitch) forcing.
Ice Flow Leading to the Deep Core Hole at Dye 3, Greenland
Authors: Whillans I. M. , Jezek K. C. , Drew A. R. , Gundestrup N.
Published: September 2017

Detailed studies of the last 20 km of the flow-line leading to the core hole at Dye 3 Greenland, provide a description of ice flow over and around basal hills. The surface pattern is very simple. Velocity vectors are nearly parallel to one another and the largest variations in velocity are speed changes along the direction of flow. The surface elevation is stepped and the speed is faster than average where the surface slope is steepest. These positions correspond to basal highs, and the surface velocity increases as expected, based on the decrease in ice thickness, which indicates that most of the ice thickness must vary in velocity as does surface ice. Further support for this comes from the form of an internal radio-reflecting layer, which, in general, has the same shape as the bed but with much reduced relief. The damping of the relief is the same both along and across the flowline, suggesting that lateral velocity fluctuations are not important and that flow around and between obstacles is not well developed at the surface or at depth. At two sites, however, the internal layer does not match the bed and at one of these there must be important third-dimensional flow at depth.
Rheology of an Ice-Floe Field
Authors: Bratchie Iain
Published: September 2017

The aim of the paper is (1) to develop theory to describe sea ice as a collection of finite-sized floes and (2) to construct a rheology based on this description.

Successful sea-ice models have considered the ice to be a two-dimensional continuum with a nonlinear plastic rheology, a two-dimensional yield curve being used to determine the internal ice stresses as functions of the strain-rate (Hibler 1979). In this paper, the shape but not the size of such a yield curve is derived from an idealized picture of floes as moving discs, randomly distributed in a plane. The expected collision rate, which determines the energy loss, is calculated in terms of the average floe size, the areal floe-number density, and the strain-rate. For the case in which the ice strength is low, the dependence of the energy loss upon the strain-rate implies a lens-shaped yield curve, the curved portions being parts of a sine wave. This compares with circular, tear drop-shaped and elliptical yield curves that have been used in sea-ice models to date (Coon 1974, Colony 1976, Hibler 1979). The applicability of the derived yield curve to cases where the ice strength is not low and significant ridging takes place, such as in a continuous ice cover is discussed.
Cryospheric Impacts of Soviet River Diversion Schemes
Authors: Holt T. , Kelly P. M. , Cherry B. S. G.
Published: September 2017

Soviet plans to divert water from rivers flowing into the Arctic Ocean have led to research into the impact of a reduction in discharge on Arctic sea ice. We consider the mechanisms by which discharge reductions might affect sea-ice cover and then test various hypotheses related to these mechanisms. We find several large areas over which sea-ice concentration correlates significantly with variations in river discharge, supporting two particular hypotheses. The first hypothesis concerns the area where the initial impacts are likely to which is the Kara Sea. Reduced riverflow is associated occur, with decreased sea-ice concentration in October, at the time of ice formation. This is believed to be the result of decreased freshening of the surface layer. The second hypothesis concerns possible effects on the large-scale current system of the Arctic Ocean and, in particular, on the inflow of Atlantic and Pacific water. These effects occur as a result of changes in the strength of northward-flowing gradient currents associated with variations in river discharge. Although it is still not certain that substantial transfers of riverflow will take place, it is concluded that the possibility of significant cryospheric effects and, hence, large-scale climate impact should not be neglected.
Sensitivity of Late-Glacial and Holocene Climates to the Combined Effects of Orbital Parameter Changes and Lower Boundary Condition Changes: “Snapshot” Simulations with A General Circulation Model for 18, 9, AND 6 ka BP
Authors: Kutzbach John E. , Guetter P. J.
Published: September 2017

Sensitivity experiments can be used to illustrate the response of the general circulation to prescribed changes in lower boundary conditions (such as ocean temperature) or external forcing conditions (such as solar radiation). The climatic record from the late-glacial and the Holocene provides examples for both types of prescribed change experiments. A number of general circulation model experiments have been carried out. These are reviewed.

At 18 ka 8P, orbital parameter values were very much like those of today, but the lower boundary conditions (ocean temperature, ice-sheet extent, etc.) were very different. The change in ocean temperature, and ice-sheet extent and thickness, were prescribed from the results of the Climate: Long-range Investigation Mapping and Prediction (CLIMAP) project.

At 9 ka BP, orbital parameter values were very different from present, leading to increased radiation in July and decreased radiation in January (compared to present). The North American ice sheet still covered a significant area, so that lower boundary conditions also differed from the present ones. The combined and individual effects of these prescribed changes on the general circulation are reviewed, particularly in the context of changes of the monsoon circulation.

At 6 ka BP, the solar radiation distribution differed from that of today in much the same fashion as at 9 ka BP, although the magnitude of the change was reduced. Lower boundary conditions were probably very similar to those of today.

A series of experimental results from 18, 9, and 6 ka BP are presented as “snapshot” estimates of the paleoclimate of those times. The results are based upon simulations with the community climate model of the National Center for Atmospheric Research.
On The Internal Melting Phenomenon (Puddle Formation) in Fast Sea Ice. East Antarctica
Authors: Ishikawa Nobuyoshi , Kobayashi Shun’Ichi
Published: September 2017

Extensive internal melting (puddle formation) was observed on the sheet of fast sea ice near Ongle Island, East Antarctica in 1980. In late November that year, when surface melting was not seen, puddles did not form beneath snow cover with a hig albedo (0.7 to 0.8) but were present in bare sea ice with low albedo (0.2 to 0.3). Electro-conductivities of puddle water ranged from 3.3-6.6 mS/cm; these were higher than for drinking water from an iceberg or snow drift (below 0.9 mS/cm), but lower than for sea water (30-42 mS/cm). Puddle water is therefore considered to originate from the internal melting of sea ice, as a result of the internal absorption of solar radiation from the surface down to a certain depth. The mechanism of puddle formation is explained by numerical analysis of a differential equation of heat conduction, which includes the amount of heat evolved by the absorbed solar radiation.
Energy Balance Calculations for the Ablation Period 1982 at Vernagtferner. Oetztal Alps
Authors: Escher-Vetter Heidi
Published: September 2017

In this paper, some features of energy balance terms will be discussed in respect to the melting capacity available at the surface of Vernagtferner in the Oetztal Alps. The climatic pattern of summer 1982 is described, then the method of calculating individual terms (shortwave and longwave radiation balance, sensible and latent heat flux) from records of radiation, air temperature, humidity and wind. The results of these calculations are discussed for ice, firn and snow areas of the glacier. In particular the relationship between the four terms is shown for 15 July 1982, the day with highest meltwater production in 1982. These values are then compared with the maximum values of the individual terms, showing that the highest meltwater production is caused by the combination of quite high values of the individual terms, but not of the absolutely highest ones. The importance of sensible heat flux for meltwater production in 1982 is discussed: comparison between meltwater production for the whole summer and measured runoff shows reasonable accordance.
Ice Front Fluctuations in the Eastern and Southern Weddell Sea
Authors: Lange Manfred A. , Kohnen Heinz
Published: September 2017

We report new data on the position of ice edges in the eastern and southern Weddell Sea for the years 1983 and 1984. The data are derived from ship-borne radar measurements of individual points along the ice edge together with ship’s positions obtained by a satellite navigation system. They are accurate within 0.23 to 0.4 nm (426 - 741 m). Comparisons of ice shelf margins for the years 1980, 1983 and 1984 allow estimates of apparent ice advance rates during this period. Together with quantitative ice edge velocity estimates first conclusions about net changes along the ice front and the ablation along the margin of ice shelves in the eastern and southern Weddell Sea are derived.
Meteorological Conditions that Initiate Slushflows in the Central Brooks Range, Alaska
Authors: Onesti Lawrence J.
Published: September 2017

Over 30 individual slushflows were documented and observations were made of both high and low flow rates during 1979, 1980 and 1981 at Atigun Pass, central Brooks Range. Air temperature, precipitation and global radiation were recorded in 1980 and 1981 during the slushflow season. Meteorological conditions that exist in this arctic alpine environment at the time of break-up apparently are factors that encourage flow activity. Persistent low temperature prior to break-up allows the snowpack to remain intact until late spring. An influx of warm air from the interior of Alaska and long hours of radiation input produce an accelerated rate of snow-melt that plays a major role in slushflow occurrence.
Effects of Drifting Snow on Surface Radiation Budget in the Katabatic Wind Zone, Antarctica
Authors: Yamanouchi Takashi , Kawaguchi Sadao
Published: September 2017

Effects of drifting snow are examined from measurements of radiation fluxes at Mizuho Station in the katabatic wind zone, Antarctica. A good correlation is found between the difference of downward longwave fluxes measured at two heights and wind speed used as an index of drifting snow. The wind increases the downward flux at a rate of 2 W m-2/m s-2 when wind speed is higher than 13 m/s. Drifting snow suppresses the net longwave cooling at the surface. Direct solar radiation is depleted greatly by the drifting snow; however, the global flux decreases only slightly, compensated by the large increase of the diffuse flux, at a rate of about 1% for each 1 m/s increase in wind speed. At Mizuho Station, the effect on longwave radiation prevails throughout the year. The relation between snow drift content and wind speed is obtained from shortwave optical depth measurements as a function of wind speed. A simple parameterization of radiative properties is given.
A Calorimeter for Measuring Free Water Content of Wet Snow
Authors: Akitaya Eizi
Published: September 2017

A new calorimeter was designed for measuring the free water content of wet snow, aiming at simplicity in mechanism and handling as well as high accuracy and speed in measurements. The mass of hot water to melt the sample and the mass of the mixture (snow sample and hot water) are measurable indoors with sufficient accuracy; therefore, in the field we need only two measurements of temperature (T and T ); this calorimeter reduces the time of measurement of one snow sample to four or five minutes. Using artificially made wet snow, having a known value of free water content, 121 tests were conducted. Standard deviation of the error was 0.82%
Ice Avalanche Activity and Mass Balance of a High-Altitude Hanging Glacier in the Swiss Alps
Authors: Alean Jürg
Published: September 2017

An estimation of average mass balance of a high hanging glacier in the Swiss Alps was made by measuring volumes of ice avalanches originating from this glacier. Ice avalanches are this glacier’s predominant form of ablation. Since the volume of the glacier has not noticeably changed over the past few years, the annual ice loss due to ice avalanches can be taken as an indication of average total net acumulation above the ice cliff where the avalanches originate. The mass balance value, as determined by recording ice avalanches, compares well with values obtained by independent methods (measurements of firn stratigraphy in the cliff, direct accumulation measurements in the vicinity). No seasonal variation in the frequency of ice avalanche occurence was detected.
Transition in Preferred Orientation of Polycrystalline Ice from Repeated Recrystallization
Authors: Maohuan Huang , Ohtomo M. , Wakahama G.
Published: September 2017

A repeated compression and annealing experiment was conducted using polycrystalline ice samples. The sample was compressed in steps of 10% at a constant low deformation rate at 272 K., and annealed at the same temperature, thus allowing the sample to recrystallize. As a result, the ice gradually changed to a fabric pattern of the 4-maximum or 3-maximum type. The result indicates that repetitive recrystallization plays an important role in forming the preferred orientation of ice in glaciers.
Movement of Grain Boundary in Sea Ice
Authors: Kawamura Toshiyuki
Published: September 2017

An experimental study on the preferred growth of grains in sea ice was performed. As a seed an artificial bi-crystal was prepared by welding two single crystals; the c-axis of one grain was in a horizontal plane, that of the other made an angle of α with the horizontal plane, and they intersected at right angles. An angle between a resulting grain boundary and the vertical line, Θ, was measured on thin sections of sea ice after it grew about 10 cm downward in sea water. The relation between a and ? was given by ? = 0.4α + 6, when a was varied from -25º to 25º. When α = 0º , that is c-axes of both the grains are at right angles on a horizontal plane, encroachment still occurs, which is contrary to the earlier studies. These results can be explained by the difference in the horizontal component of growth rate between neighbouring grains at the grain boundary groove.
Melting and Heat Exchange at the Bottom of a Snow Cover
Authors: Kojima Kenji , Motoyama Hideaki
Published: September 2017

The melting rate of the bottom of a snow cover during the winter and its variation with time were studied in relation to heat exchange at the ground-snow interface. Continuous observations were made of bottom-melt, using a lysimeter, during the past four winters beginning December 1980, at our test field in Moshiri, Hokkaido, which is known for severe coldness and deep snow.

During the four months in this area the amount of bottom-melt ranged from 45 - 70 mm in total and from 0.4 - 0.6 mm per day on average. In winters with much snow the daily amount of bottom-melt decreased gradually from a maximum of about 1.5 mm.d-1 in early December, reached its minimum of 0.2 - 0.3 mm d-1 day in February, and then increased again. In a winter with a smaller amount of snow it varied greatly with time during the early period of the winter and became zero temporarily. Such variations of the melting rate could be explained by conductive heat fluxes observed in the ground and snow. The daily average of the former was about 5 W.m-2 at a depth of 0.1 m in early December and decreased to about 2.5 W.m-2 in early April.
Development of an Automatic Ice Fabric Analyser
Authors: Mori Y. , Hondoh T. , Higashi A.
Published: September 2017

An automatic ice fabric analyser has been developed which precisely determines both c- and a-axes of the individual grains in a thin polycrystalline ice specimen by the use of X-ray Laue method (eg Cullity 1956). The method of analysis is computer-aided indexing of the zone-axes in X-ray Laue patterns. Crystal orientations can be automatically determined by the analyser with an error of approximately 0.6_. Time for analysing one specimen containing 100 grains is approximately three hours at present.
Measurement of Settlement Forces on Horizontal Beams Buried in Snow Cover
Authors: Nakamura Hideomi , Abe Osamu
Published: September 2017

Settlement force of a snow cover acting on horizontal beams O.8 m high on the ground has been measured using electric force gauges since winter 1974/75, to understand mechanisms of settlement force generation. Shapes of cross-sections of the beams were rectangular, square, equilateral triangle and triangular with a 37_ vertical angle. From the measurements, it was found that the magnitude of the settlement force acting on a beam did not depend upon the shape of cross-section when snow depth was smaller than 1.3 m, but in deeper snow it was smaller on the triangular than on the rectangular beam. When the surface of the snow cover turned into a crust, the settlement force increased from about 0.3 kN m-1 to 1.1 kN m-1. Physical properties of snow cover are important for quantitative estimation of the settlement force on a beam.
Comparison of Mechanical Tests on the Dye-3, Greenland Ice Core and Artificial Laboratory Ice
Authors: Shoji H. , Langway C. C.
Published: September 2017

The horizontal velocity of a thick ice sheet is maximum at the surface and decreases with increasing depth. The horizontal velocity profile at a given location differs from another location depending upon the in situ stress and temperature conditions and the changing but distinctive physical and chemical character of the ice profile. The main property changes that influence the behavior of horizontal ice flow include chemical impurity concentration levels (both solid and dissolved components) and c-axis orientation. Shoji and Langway (1984) calculated the velocity profiles for both the Camp Century and Dye-3 Greeland location by taking into consideration possible enhancement factor variations over the profiles. This analysis was compared with the theoretical and experimental strain rate data obtained for laboratory ice at the same stress and temperature levels. This study indicated that the largest horizontal velocity component is the result of a highly enhanced shear deformation zone, a few hundred meters thick existing at the base of the ice sheet.
Sensing of Snowpack Melting by an Active Microwave System with Fixed Frequency
Authors: Suzuki Masahiro , Matsumoto Tadashi , Kuroiwa Daisuke , Fujino Kazuo , Wakahama Gorow
Published: September 2017

Using continuous microwave systems at fixed frequencies in the X- and R-band, surface depression of a snowpack was obtained from interference between the emitted wave, at normal incidence to the snowpack surface, and the reflected wave from the snow surface. The microwave system worked as a simple interferometer in air with respect to the snow surface. The values of the depression could be obtained from the numbers of cycles of the fluctuation and the wavelength of the microwave used.
Ablation Rates on the Ceiling of a Snow Tunnel Over a Stream
Authors: Uematsu Takahiko
Published: September 2017

A snow tunnel is often formed between the water surface of a small stream and the base of a snow cover in snowy areas. Observations made in northern Japan revealed that the amount of snow ablated at the ceiling of the snow tunnel ranged widely from 1.3 - 50 kg/m2d. This amount was calculated using heat transfer method; assuming that the ceiling was ablated only by the flux of heat from stream water, the amounts observed and calculated were found consistent.
Mass Balance Study of a Glacier System from Hydrological Observations in Langtang Valley, Nepal Himalaya
Authors: Yamaha Tomom , Motoyama Hideako , Thapa Kadcha Bdr.
Published: September 2017

Hydrological and meteorological observations of river runoff, precipitation and air temperature were conducted 27 August to 26 October 1982, in Langtang Valley, Nepal Himalaya, whereby the mass balance of the glacier system there was estimated. Observed values suggest that (1) all glacier ablation and rainwater in the subwatershed of Langtang Valley drain into the river with the runoff coefficient of 1; (2) ablation of the glacier system can be estimated simply using a degree-day factor of 10 mm/degree-day; and (3) precipitation is considered uniform over the whole watershed. Assuming that the suggested phenomena persist throughout the year, records of monthly precipitation and monthly mean temperature in this valley, indicate that annual accumulation and ablation in the glacier system amount to 2000 ± 200 mm, respectively.
Modelling a Snowdrift by Means of Activated Clay Particles
Authors: Anno Yutaka
Published: September 2017

This paper presents a small scale modelling of a snowdrift using activated clay particles.

Characteristic properties of activated clay particles, which are different from model snow particles proposed previously by other investigators, are fineness, high angle of repose and wide range of cohesion. Such properties may provide a similitude of a snowdrift and the phenomena caused by wet snow particles in a small scale model.

Experimental results presented in this paper show that activated clay particles are the most suitable substitute for natural snow particles in modelling, and indicate also the possibility of using them to model wet snow particles.
Design Criteria and Location of Snow Fences
Authors: Norem Harald
Published: September 2017

The paper describes experience gained in Norway regarding the design criteria and use in practice of snow fences. The paper is based on theoretical studies on drifting snow, model experiments and experience accumulated through practical consulting work.

Snow fence design is a compromise between the storage capacity and minimization of dimensioning forces. Design considerations include fence height H, total snow fence density, and the gap between ground and fence. A gap of 0.15H - 0.2H and a total density of 45% are usually recommended. On ridge crests the gap can be reduced to 0.1H and in areas where snow depths exceed 2.0 m, it can be increased to 0.3H. In such cases the fence density should be varied such that the total density, including the gap, will remain near 45%. The height of the snow fences should be kept within 3.5 -4.5 m and the snow fences should be erected on the windward side of obstacles that create snowdrifts. The minimum distance from fence to road should not be less than 15H; in certain circumstances in coastal climate, this can be reduced to 10H.
Energy flux density estimation over sea ice based on satellite passive microwave measurements
Authors: Steffen Konrad
Published: September 2017

This paper discusses in detail the energy flux density estimation at the ice/atmosphere interface over the entire North Water region, based on the ice-type distribution during the winter (1978/79 to 1985/86). The analysis is based on passive microwave measurements of the scanning multichannel microwave radiometer (SMMR) onboard the Nimbus 7 satellite. Based on the relation of increasing polarization ratio (18 or 37 GHz) with decreasing ice thickness, a threshold technique was applied to classify the different young ice types. The polarization ratio method seems feasible for climatological applications, such as energy flux density estimations, over large areas with homogeneous young ice. More than 20% young ice (<0.3m) was found in the North Water area (100,000 km2) throughout most winters, with maximal values of 60% and more, and only a few percent of open water were classified. In general, the young ice cover in the North Water was decreasing towards the end of the winter. The mean energy loss for the entire North Water region was found to be 77 W m−2 for the months of November to March. Considering an energy supply by refreezing of 38 W m−2, the remaining 39 W m−2 must be withdrawn from the enthalpy in the sea water.
Image analysis of sea-ice thin sections: a step towards automated texture classification
Authors: Eicken Hajo , Lange Manfred A.
Published: September 2017

The texture of a material is closely connected to both its development and its properties. Aided by fully automated image-processing techniques developed for a simple PC-based system, we extract textural information from sea-ice thin sections. As a quantifier of mean size and orientation of grains, the “contrast gradient” has been defined. The skewness of the chord-size distribution aptly describes the grain-size distribution. Through a combination of these two parameters, granular and columnar textures can be distinguished. Samples of mixed columnar/granular texture may be further specified through their fractal properties. Fully automated techniques may be of use due to their objective scrutiny and their ability to draw information from large databases. In addition, they allow for highly specific descriptions of texture and may further the understanding of its development.
Notch-acuity effects on the fracture toughness of saline ice
Authors: Defranco S.J , Wei Y. , Dempsey J. P. D.
Published: September 2017

Dynamic ocean-induced loading of ice has recently prompted interest in the fatigue strength of ice and, consequently, aspects of the fracture testing of ice need to be examined. One aspect in fracture testing, the effects of notch acuity on the apparent fracture toughness (KQ) of saline ice, was investigated in this study using four groups of single-edge notched-bend specimens with different crack-(or notch-) root radii, fabricated by four different methods; namely, drilling a small hole of two different radii at the crack tip, cutting a crack with a band saw and using a hand-held razor blade to scribe a sharp crack. For this study, tests were performed on saline ice using one crack length and orientation, constant thickness and constant temperature (−25°C). The mean values and the standard deviations of the apparent fracture toughness of the specimens with blunt notches were higher than those with sharp cracks. The results presented in a plot of fracture toughness versus where ρ is the crack-tip radius, provide a preliminary estimate of the required notch acuity for fracture-toughness testing of saline ice.
An Antarctic field study of the rheology and movement of a sea-ice floe aggregate
Authors: Jacka T.H. , Thwaites R. , Wilson J.C
Published: September 2017

M.V. Nella Dan was beset in ice near 66°S, 51°Ε from 27 October to 15 December 1985. The scientific investigations planned for the voyage into the sea-ice zone included ice thickness, concentration and extent measurements, aerial photography of the ice, a core drilling project and meteorological observations. Once beset, the programme was expanded to include repeat measurements of a small strain grid and measurements of the sea-ice drift rate. Strongly convergent local conditions had led to the initial besetment of the ship. Analysis of measurements of the strain grid area over an 11 d period shows that, although there is some indication that the ice field may have been divergent, opening by approximately 3.4% over this period, there are large errors in the measurements and some doubt must be placed on the reliability of this estimate. The drift speed and direction were found to be highly dependent on wind speed and direction, the drift rate being approximately 2.7% of the wind speed at an angle of about 29° to the left of the wind direction.
Seasonal Arctic sea-ice simulations with a prognostic ice-ocean model
Authors: Ranelli Peter H. , Hibler William D.
Published: September 2017

A prognostic ice-ocean model of the Arctic, Greenland and Norwegian seas with daily wind and atmospheric forcing is integrated for 30 years to quasi-equilibrium. Three simulations are carried out to investigate the role played by ice deformation and transport in baroclinic adjustment of the Arctic Ocean: a standard run with precipitation and ice transport, a simulation without precipitation and a “thermodynamics only” simulation without ice transport but including precipitation. A diagnostic model is integrated for five years to serve as a comparative control run. Comparison of the vertically integrated stream-function of each of the model runs indicates that the vertical density stratification needed to maintain the circulation of the Arctic Ocean is reduced excessively when precipitation is neglected and artificially enhanced if ice transport out of the basin is ignored. This effect is even more noticeable in the surface currents and is also apparent in a comparison of simulated and observed drifting-buoy tracks. An analysis of the salt budget of the Arctic Ocean indicates that the three main components, salt transport by the ocean, salt flux from the annual cycle of ice, and a fresh-water flux from precipitation and river runoff are approximately of the same magnitude. The main circulation deficiency identified in the simulations is an inadequate flow of Atlantic water into the Arctic Basin through the Fram Strait.
On the ridging of a thin sheet of lead ice
Authors: Hopkins M. A. , Hibler W. D.
Published: September 2017

A two-dimensional particle simulation model of the sea-ice ridging process is developed. In this model, ridges are formed from an intact layer of newly frozen lead ice colliding with a thick multi-year floe. Blocks broken from the leading edge of the lead ice collect above and beneath the multi-year floe to form the characteristic ridge structure seen in the central Arctic. The total energy consumed in ridging ice, which is converted into the potential energy of the ridge structure and dissipated by the frictional and inelastic contacts between blocks of ice, is calculated explicitly. The results of preliminary numerical experiments using this model indicate that the amount of energy required to ridge ice may be much larger than previous estimates.
A one-dimensional model for wave-induced ice-floe collisions
Authors: Shen Hayley H. , Ackley Stephen F.
Published: September 2017

In this study, the collision of ice floes under the action of a monotonic wave is quantified. The lateral motion of an ice floe caused by the wave is modeled as the sliding of an object under gravity. In this case, the gravity component in the direction of motion varies with time and space as the wave progresses by the floe. Drag and added mass effects are included in the model. Two floes located at different positions are shown to have a net difference in their drift (caused only be repeated wave passages). In most cases, this differential drift eventually causes floe collision. When two floes collide, a spring and dash-pot model is adopted to calculate the contact force. A one-dimensional wave passing through a one-dimensional array of disc-shaped floes is examined. Two phenomena are apparent from the analysis. First, waves have a herding effect that forms bands of floes with the width equal to the wavelength. Secondly, the frequency of collision is sensitive to the elastic properties of the floes and the wave amplitude. With sufficient values of the damping constant, which operates when two floes collide, the floes stay in contact for prolonged periods, indicating the potential to freeze together and form composite floes, as was observed in the field studies.