bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the relationship between local stresses and strains in Arctic pack ice
Authors: Tucker W. B. , Perovich D. K. , Hopkins M. A. , Hibler W. D. 
Published: September 2017

Local ice strains and in situ ice stresses were simultaneously measured on the Coordinated Eastern Arctic Experiment (CEAREX). The experiment took place in the fall of 1988 and was centered about an ice-strengthened ship moored to a multi-year floe in the pack ice northeast of Spitsbergen. During the period of data collection, which extended from early October to late November, the ship and the ice surrounding it drifted from 82°40′N, 32°32′E to 78°54′N, 31°27′E.As soon as ice temperatures were low enough to permit installation, stress sensors were placed at four sites, two sites on each of two adjacent multi-year floes. Principal stress components and the principal stress direction were determined at each sensor. At the same time, microwave transponders, capable of measuring ice deformation to accuracies better than 1 m, were positioned within 1 km of the stress sensors and provided an approximation of the local strain field.What makes this joint dataset particularly interesting is that it includes some large ridging events and a particularly large event which terminated the experiment when the multi-year floes in the local area were broken into small fragments. A wide range of ice stresses was measured during the period. The largest compressive stresses, about 250 kPa, were measured by the near-surface sensors. Although sensors in different locations responded differently to ice movement, the large events were common to all shallow sensors.
Progress and prospect for research on mountain glaciers in China
Authors: Zichu Xie 
Published: September 2017

In the past decade the interest of many scientists worldwide has been attracted to the central Asian area of China. A number of gaps in scientific knowledge have been closed, and many significant discoveries have been made.The most important achievement is the ice-core research by the Sino-American Joint Expedition to the Dunde Ice Cap, Qilian mountains, that established a record of ten thousand years of climatic and environmental change. In addition, in cooperation with scientists from Japan, Switzerland and the Soviet Union, studies have been carried out focusing on glacier mass balance, heat balance, the mechanism and formation of glacial runoff, and high mountain climates. This work has been done in the Tien Shan, west Kunlun, Tanggula, Nyaingentanglha and Gongga mountains.In addition, through joint efforts of scientists from China, Nepal and Canada, important advances have also been made in studies of glacier lake outburst floods and debris flows in the Karakoram and the Himalayas, and in mountainous areas in southeastern Tibet.The glaciers in central Asia will continue to be an important research area for glaciologists from all over the world in the coming decade.
Sediment-mass exchange between turbid meltwater streams and proglacial deposits of storglaciären, northern Sweden
Authors: Holmlund Per , Burman Helene , Rost Torbjörn 
Published: September 2017

Detailed changes in surface elevation of a recently deglaciated area have been mapped using a high-resolution photogrammetric method, with a view to estimating the contribution of debris from the proglacial area to the meltwater streams draining Storglaciären, northern Sweden, over the period 1980-90. The net contribution of sediments originating from the deglaciated area immediately in front of the glacier was of the order of 50% of the suspended silt load transported by meltwater at the flume Rännan downstream from the glacier, but at the same time, a similar amount of sediment accumulated along the streams. Though there is a significant exchange of mass, the net change is close to zero. Moreover, the survey provides detailed information about morphological changes in the landscape. Different processes, such as melting of permafrost, fluvial erosion and sedimentation, have been active.Erosion and sedimentation rates were calculated from the difference between digital terrain models based on aerial photographs taken in 1980 and 1990. The result shows erosion in the central part of the proglacial area and accumulation of coarser sediments along the braided streams. In places, the ground is sinking, possibly due to melting of permafrost.Where the ice is thinner, in the marginal zone, the thermal regime of ice in the tongue of Storglaciären corresponds well with the proglacial geomorphology. At present, the glacier has a 30-40 m thick cold surface layer which at the thinner marginal zone corresponds to a 100-200 m wide frozen rim. The temperature distribution within the ice was mapped using high-resolution radar.
Snow-creep forces on masts
Authors: Larsen Jan Otto 
Published: September 2017

Since 1975, the Norwegian Geotechnical Institute has performed field investigations of snow-creep forces on masts at the research site in Grasdalen, Stryn mountains in Norway. Two poles, with diameters of 419 and 219 mm, respectively, were erected at the site together with a retaining structure. On both poles, strain gauges were mounted in pairs every 0.5 m to find the axial stresses and the moments in different sections. In the middle section of the retaining structure, the beams and supporters were instrumented to obtain measurements of the strains and stresses. Snow glide was controlled by glide shoes mounted at the rock surface above the structures.During the winter, snow profiles were made systematically; these included measurements of snow depth, density and temperature, and observations of snow type and moisture content. By relating the measured stresses and moments in the structures to the snow depth, it was possible to find the snow-pressure distribution. A comparison of the snow pressures with the “Body force index” (product of snow depth h, density ρ and acceleration due to gravity g), show a close relationship for the wall element. For the pole elements, the snow temperature during the winter is an added factor of high importance and the highest pressures on these elements occur in winters with long periods of 0°C isothermal snowpack.
Statistical prediction of maximum avalanche run-out distances from topographic data in the western Catalan Pyrenees (northeast Spain)
Authors: Furdada Glòria , Vilaplana Joan Manuel 
Published: September 2017

We present regression models to estimate maximum avalanche run-out distances in the western Catalan Pyrenees (northeast Spain). The regression equations have been calculated from topographic parameters of 216 well-known avalanche paths, mapped on avalanche location maps at a scale of 1: 50 000. Historical information about avalanche maximum run-out zones has been available for some avalanche paths hut most of them have been delimited by vegetation and geomorphological indices.The avalanche profiles, which are representative of avalanche paths, have been classified on the basis of avalanche run-out zone morphology, because this has a considerable influence on avalanche behaviour and run-out. Three classes have been defined and regression equations obtained for each class and also for the total. Finally, some examples have been calculated in order to appreciate the applicability of the models to improving avalanche mapping.
Atmospheric and hydrological boundary conditions for slushflow initiation due to snowmelt
Authors: Scherer Dieter , Gude Martin , Gempeler Markus , Parlow Eberhard 
Published: September 2017

Slush-flows of a large variety of magnitudes were observed during three field campaigns to Liefdefjorden, northwestern Spitsbergen, and one campaign to Kärke-vagge, northern Sweden. In the latter campaign, the release and movement of a slush torrent was documented on video and in photographs. Meteorological and snow-hydrological measurements carried out during these campaigns were analysed with respect to slushflow initiation due to snow-melt.Since slushflows are quite common in polar and sub-polar drainage basins (although they are not restricted to these regions), specific atmospheric and hydrological boundary condittons must be fulfilled for slushflow initiation due to snowmelt. Radiative fluxes, air temperatures and wind velocities are the most important atmospheric variables, while snow depth, depth of the water-saturated layer, hydraulic conductivity and snow structure are the primary snow variables of interest.It has been shown that slushflows can be released due to energy input in the snow cover by net radiation and sensible heat within the ordinary range of the high-latitudinal snow melt period. Slush torrent initiation is intensified by a superpositton of both energy fluxes. Infiltration losses were not significant even when permafrost was not present. Crucial for slushflow initiation due to snowmelt is the timing of energy input and meltwater flow through the snowpack.
Snowmelt and slushflows: hydrological and hazard implications
Authors: Gude Martin , Scherer Dieter 
Published: September 2017

In many high-latitude areas, slushflows occur frequently during the snowmelt period but information on the initiation mechanism is rare. Field observations and measurements of slushflows in northwestern Spitsbergen and in northern Sweden demonstrate the role of meltwater accumulation and the hydraulic pressure gradient in the release process. Snow metamorphism is revealed to be of minor importance in the observed events. The monitoring of water-pressure development in a saturated snow cover demonstrates that preferred release areas are within low-gradient valley sections, where meltwater inflow is higher than outflow.Slushflows consist of mudflow-like flowage of water-saturated snow along stream courses. They represent transitional processes between fluvial floods and avalanches. On the other hand, they possess unique characteristics concerning release and movement. The comparative evaluation of definition items for fluvial floods, slushflows and avalanches offers hasic data suitable for a risk assessment.
Accumulation-rate variations around Summit, Greenland
Authors: Bolzan John F. , Strobel Michael 
Published: September 2017

AbstractShallow cores to about 17 m depth were recovered at nine sites distributed on a 150 km × 150 km survey grid centered Summit in central Greenland. Measurements of the stable oxygen-isotope ratio and the gross β activity as a function of depth enable annual summer horizons to be identified and dated. From these data, average accumulation rates were computed with an uncertainty of about 5–8%. The contours of constant accumulation rate in the region suggest a primary moisture flux from the southwest of the grid. Similarly, contours of the average oxygen-isotope ratio are consistent with the progressive isotopic depletion of a precipitating air mass moving from the southwest, and automatic weather-station data indicate that the moisture flux tends to be largest from the southwest quadrant. The annual variation in the total accumulation over the grid shows no persistent trend over the interval 1964–87 common to all cores.
Distribution of stable isotopes in surface snow along the route of the 1990 International Trans-Antarctica Expedition
Authors: Dahe Qin , Petit J.R. , Jouzel J. , Stievenard M. 
Published: September 2017

AbstractThis paper presents the distribution of average δD andδ18O values for the top 1 m of surface snow for a large area of Antarctica. The samples were collected on the 1990 International Trans-Antarctica Expedition which crossed the continent from the northern tip of the Antarctic Peninsula to Mirny Station. The empirical relationships between the isotopes, temperature and elevation are computed. The slopes of δD with respect to the surface temperature for the segments west (Patriot Hills-Vostok) and east of Vostok (Komsomolskaya-Mirny) are not significantly different to that observed between Dumont d’Urville and Dome C (Lorius and Merlivat, 1977) which are often used to interpret deep ice-core isotopic profiles. There is, however, a noticeable shift between the two regression lines with, for a given temperature, higher isotopic values west of Vostok. The deuterium excess values increase sharply at 3000 m.a.s.l. on the plateau, confirming the results of Petit and others (1991).
Internal melt figures in ice by rapid adiabatic compression
Authors: Gagnon R.E. , Tulk C. , Kiefte H. 
Published: September 2017

AbstractSingle crystals and bicrystals of water ice have been adiabatically pressurized to produce, and clearly illustrate, two types of internal melt figures: (1) dendritic figures that grow from nucleation imperfections on the specimen’s surface, or from air bubbles at grain boundaries, into the ice as pressure is elevated; and (2) compression melt fractures, flat liquid-filled disks, that nucleate at imperfections in the crystal and grow with the application of pressure eventually to sprout dendritic fingers at the periphery. The transparency of the ice permitted visualization of the growth and behavior of the figures, and this could be an important tool in understanding the role of phase transformations in deep-focus earthquakes. Correlation between figure size and pressure is noted for the first time.
A Finite-element Model of Antarctica: sensitivity test for meteorological mass-balance relationship
Authors: Fastook James L. , Mike Prentice 
Published: September 2017

AbstractA finite-element solution of the time-dependent mass-continuity equation for column-averaged ice-sheet flow and sliding is applied to the Antarctic ice sheet. First, a calibration of the model to the steady-state present ice-sheet configuration is presented. With fitted values of the parameters describing the regions of sliding, the degree of bed coupling and the ice hardness, a change in the mean annual sea-level temperature is used to simulate variation of the climatic conditions over Antarctica for both warming and cooling of the climate. Paradoxically, a climate warming of up to 9 deg leads to an increase in ice volume, while cooling leads to decreasing ice volume as long as the present margins of Antarctica are maintained. Some extreme simulations of the Antarctic ice sheet for “maximum over-riding” and “minimum warm climate” are shown for situations where the present bed conditions are altered. Finally, a time-dependent simulation shows the response of the ice-sheet system to cyclical variations in the simulated climate, demonstrating the lag of the ice-sheet response to be approximately 2700 years.
Unusual flood events from an Alpine glacier: observations and deductions on generating mechanisms
Authors: Warburton J. , Fenn C R. 
Published: September 2017

AbstractObservations are presented on a particularly unusual sequence of flood events witnessed at Bas Glacier d’Arolla, Switzerland, in July 1987. The sequence was triggered by heavy rain storms, and involved a supraglacial “overflow event” (water cascading from moulins over the snout of the glacier) succeeded, following a series of “mini-floods”, by a subglacial “outburst event”. Available hydrological and geomorphological data are used to assess the significance of the floods and to deduce likely explanations for each phase of the flood-event sequence. Bottom-up surcharging of a poorly developed subglacial drainage system is the preferred explanation for the overflow event. The subglacial outburst is explained as an extreme “spring event”. Hydraulic jacking is implicated, but not proven, during both events. Whilst the flood sequence was triggered by an intense storm, englacially stored waters are believed to have contributed most of the flood waters.
Observations of a rift in the Ronne Ice Shelf, Antarctica
Authors: King E.C. 
Published: September 2017

AbstractDuring seismic profiling on the northwest Ronne Ice Shelf Antarctica, a rift in the ice shelf was encountered. The rift trends southeast to northwest and is located approximately 30 km inland from the present-day ice front The rift is 340 m wide and the surface elevation of the ice shelf drops by 14.65 m over the axis of the rift. The rift has an asymmetrical base with a near-vertical ice-water interface on its northeast flank and a more gently dipping ice-water interface forming its southeastern flank. The ice shelf thins from a thickness of 350 m away from the rift to a thickness of 225 m at the rift axis. The rift is the probable location of a future major calving event on this section of the Ronne Ice Shelf, an event which would release an iceberg of up to 30 km by 180 km into the Weddell Sea.
On the Formulation of Basal Debris Drag for the Case of Sparse Debris
Authors: Snoemaker E.M. 
Published: September 2017

AbstractTwo models are presented for the formulation of abrasion and basal drag due to rock–rock friction (debris drag) for the case of sparse debris entrained in the basal layers of a temperate glacier resting on a bedrock bed. The first model is formulated in terms of average basal melting rate, va, and the concentration, C, of basal debris fragments which make intermittent bed contact. The second model is formulated in terms of vn the component of ice velocity normal to the bed flowing around rock fragments contacting the bed, and Cc, the concentration of debris actually in contact with the bed. The relationship between the two models is given for the case of a sinusoidal bed. Generalizations are discussed as well as potentially important physical processes which remain to be investigated.
Composition, Internal Structures, and an Hypothesis of Formation for Drumlins, Waukesha County, Wisconsin, U.S.A.
Authors: Richard Whittecar G. , Mickelson David M. 
Published: September 2017

AbstractLate Wisconsin-age drumlins west of Milwaukee are clustered atop uplands bounded by discrete scarps. Gravel operations within the uplands have exposed drumlin cores of undeformed till and outwash beds which are truncated at the sides of the drumlin. In a few areas, clastic dikes, faults, overturned bedding and shear folds disturb the original layering. The drumlin shapes are blanketed with a basal till 1–3 m thick (“retreat” till) which truncates all internal structures. This till covering cannot be distinguished from the youngest truncated till (“advance” till).Truncation of all of these structures shows that these drumlins are erosional forms carved from pre-existing drift. Apparently, during erosion under compressive flow, some beds became unstable and initiated large-scale movements of material into the drumlin from beneath the drumlin form. Failure and mobilization of the finer-grained beds may have been due to increased pore pressures, differing stages of dilatancy, or differing bulk densities. A growth relationship for drumlins may exist that is based upon the rates of material moving into the drumlin from below and rates of erosion of the drumlin form.
Mercury-in-Glass Thermometers for Precise Temperature Measurements Near 0°C
Authors: Osterkamp T. E. 
Published: September 2017

AbstractExperience with the calibration and field use of mercury-in-glass calorimeter thermometers provides an indication of the accuracy attainable and the necessary corrections to obtain that accuracy. Secular changes as large as 57 mK have been observed during the first three years of thermometer use. Light physical tapping is found to reduce the thermometer readings by 3–6 mK. Corrections for variations in the external and internal bulb pressure and care to avoid parallax are necessary to obtain the best accuracy in field measurements. The best accuracy obtainable with these thermometers for temperature measurements near 0°C is approximately ±4 mK for laboratory measurements and ±5 mK for field measurements.
Structural characteristics of congelation and platelet ice and their role in the development of antarctic land-fast sea ice
Authors: Jeffries M. O. , Weeks W. F. , Shaw R. , Morris K. 
Published: September 2017

AbstractIce cores were obtained in January 1990 from the land-fast ice in McMurdo Sound for a study of variations in texture, fabric, sub-structure, composition and development. Two primary ice types were observed, congelation and platelet, with a minor amount of frazil ice. Congelation ice growth precedes platelet-ice accretion. Congelation-ice fabrics show frequent moderate to strong alignments, a phenomenon believed to be due to water-current control of selective ice-crystal growth. Platelet ice originates at the base of the congelation ice, initially as a porous latticework of tabular ice crystals which subsequently consolidate by congelation of the interstitial water. Interstitial congelation-ice fabrics generally have little or no alignment, indicating the reduced effect of currents within the platelet latticework prior to solidification. Platelet-crystal textures range from small, wavy-edged forms to large, blade-like forms. Platelet-crystal fabrics indicate that, in addition to being randomly oriented, the platelet latticeworks commonly include many crystals with their flat (0001) faces oriented both parallel and normal to the base of the overlying ice. Plate-width data suggest that the interstitial congelation ice-growth rates remain similar to those of the overlying congelation ice. This effective increase in growth rates probably happens because the latticework of accumulating platelets ahead of the freezing interface ensures that the water within the platelet layer is at the freezing point and less heat has to be removed from platelet-rich water than from platelet-free water for a given thickness of congelation ice to grow. The negative oceanic heat flux associated with platelet-ice formation in McMurdo Sound explains why McMurdo Sound fast ice is thicker than Ross Sea pack ice, and also why it reaches a greater thickness than Arctic fast ice grown in a similar polar marine climate. Plate widths in the McMurdo Sound congelation ice suggest, however, that it grows no faster than Arctic congelation ice.
Airborne particles in snow
Authors: Heintzenberg Jost , Rummukainen Markku 
Published: September 2017

AbstractIn a pilot experiment, airborne particles were shown to exist in snow. In newly deposited snow they could be traced down to 17 cm below the surface. With our particle sensor, the snow was ventilated on the level of expected natural ventilation velocities. We show with a simple deposition model that air/snow exchange of airborne particles must be considered in the interpretation of impurities in snow and glacier ice. However, the relative magnitude of ventilation velocity compared to dry-deposition velocities at the surface is of crucial importance for determining total deposition. In particular, in ice sheets with high ventilation velocities, seasonal variations in atmospheric concentrations can be dampened and age distributions of deposited particles need to be considered similarly to the occlusion of gases.
High-resolution dielectric profiling of ice cores
Authors: Moore J. C. 
Published: September 2017

AbstractA new method for high-resolution (3 mm) dielectric profiling of ice cores is described. The method measures the capacitance and conductance of the ice at a single frequency (chosen to be 50 kHz in this case). The technique requires only a few minutes per metre of core, and no sophisticated data analysis. The system is designed to operate on ice cores that have been cut longitudinally, providing one flat and one curved surface. The 50 kHz conductance is dependent on the acid and neutral-salt concentrations in the ice. The new method was tested successfully on the GRIP core from Summit, Greenland, in 1991. It is useful for detecting seasonal variations in impurities in both acidic Holocene ice and in normally alkaline Wisconsin ice.