bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glacial and lake fluctuations in the area of the west Kunlun mountains during the last 45 000 years
Authors: Chaohai Liu , Shijie Li , Yafeng Shi 
Published: February 2017

There appear to have been several important glacial advances on the southern slope of the west Kunlun mountains, Tibetan Plateau, since 45 000 a BP. Based on the record of alternating till and lacustrine sediments and 14C determinations, these advances are dated to 23 000–16 000, 8500–8000, and 4000–2500 a BP, and to the 16th–19th century AD, with regional variations occurring during each of the advances. The glaciation of 23 000–16 000 a BP is equivalent to the last glacial maximum (LGM) and its scope and scale were much larger than any of the others.
Lake changes are a response to both tectonic uplift of the plateau and global climatic change. With regard to the latter, both changes in precipitation and changes in the extent of glaciation can affect lake levels. High lake levels occurred during interstadial conditions between 40 000 and 30 000 a BP, when the area experienced a relatively warm and humid climate, and during the LGM, between 21 000 and 15 000 a BP. During the Holocene, lakes have been shrinking gradually, coincident with the dry climate of this period of time.
Water Temperature Measurements in Turbulent Streams During Periods of Frazil-Ice Formation
Authors: Osterkamp T. E. , Gilfilian R. E. , Gosink J. P. , Benson C. S. 
Published: February 2017

Field measurements of water temperatures in two turbulent streams in interior Alaska have been made during periods of frazil-ice production. The measured equilibrium temperature of the water Te-0.005°C agrees with the value calculated from the electrical conductivity of the water. Average cooling rates of the streams during the summer-to-fall stream cooling period were on the order of several tenths of a degree per day with average surface heat losses of -5 to -18 W m−2. Just prior to a frazil-ice event, the water-cooling rates were -1 to -3 mK min−1with surface heat losses of -47 to -140 M m−2Supercooling at the water surface of a stream prior to and during frazil-ice production does not exceed 0.2°C as shown by measurements of air-water temperature profiles and by radiometer measurements. Mater supercooling at the time of frazil-ice nucleation was &lt;10 mK. These measurements show that frazil-ice nuclei in streams must be other ice particles, cold organic materials, cold soil particles, or a combination of these, that may be introduced into the stream by mass exchange processes at the air-water interface.The maximum observed supercooling was ΔTm40 mK. Two measured values for the residual supercooling were 3 and 9 mK. Frazil growth rates calculated from the observed values of supercooling show that, unless the period of residual supercooling is very long, most of the frazil-ice production during one night of supercooling occurred in the transient thermal period from the time of nucleation to the time that the water became residually supercooled.
Density-Depth Profile Determined by Seismic-Refraction Studies: Ice Stream B. West Antarctica (Abstract)
Authors: Anandakrishnan S. 
Published: February 2017

Detailed seismic short-refraction profiling was conducted on Ice Stream Β (UpB) during the 1983–84 austral summer. A new high-resolution data logger, developed at the University of Wisconsin, recorded both compressional- and shear-wave arrivals. We report here on P-wave and S-wave profiles recorded along a line parallel to the axis of the ice stream. Source-receiver separations up to 720 m yielded seismic velocity-depth curves to below the firn-ice transition zone (slightly greater than 30 m at UpB).
For the compressional-wave profile, geophones were separated by 2.5 m, which yielded a velocity-depth curve with a granularity of ∼1 m. The corresponding density-depth curve agrees well with direct density measurements obtained from a core extracted nearby (Alley and Bentley 1988, this volume). Discontinuities in the velocity gradient do not appear at the “critical densities” as they did at Byrd Station, Antarctica, and elsewhere (Kohnen and Bentley 1973
, Robertson and Bentley 1975).
Two shear-wave profiles were recorded, both with geophone spacings of 5 m, one with longitudinal polarization (SV) and the other with transverse polarization (SH). There is a marked difference in velocity between the SH and SV waves, particularly in the shallow firn. We suggest that a strong vertical shape-and-bonding fabric in the shallow firn, as observed in cores collected at UpB, would account for this disparity.
Ice Loss in the Ablation Area of a Himalayan Glacier; Studies on Miar Glacier, Karakoram Mountains, Pakistan
Authors: Young G.J. , Schmok J.P. 
Published: February 2017

One of the main aims of the Snow and Ice Hydrology Project, a joint Canada-Pakistan endeavour, is to estimate ice loss in the ablation areas of glaciers in order to predict with greater confidence stream flow in the headwaters of the Indus River. To this end, Miar Glacier, located in the central Karakoram Range, north of Gilgit, was intensively studied during the summers of 1986 and 1987.
Measurements of glacier mass balance by the monitoring of accumulation and ablation at stake locations is very difficult in the Himalyan environment. It is usually almost impossible to reach elevations above the equilibrium line without major effort, and always very difficult once there to make meaningful measurements; the ablation areas are often heavily crevassed and/or debris-covered, and this poses difficult sampling problems.
The method used in this study was to monitor annual surface movement on a cross-profile as near as possible to the equilibrium line. The measurements, obtained in conjunction with depth soundings made on the same profile, allow the annual ice flux through the cross-profile to be calculated. If an approximately steady-state glacier is assumed, it would be expected that this flux would be roughly equivalent to the rate of ice loss below the profile.
The movements of wooden stakes drilled into the glacier were monitored throughout each of the summers and, since two of the stakes survived the intervening winter, this allowed calculation of annual movement. Distances between the crests of ogives were also surveyed, providing an independent assessment of glacier movement. Depth measurements by radio-echo sounder were successfully made in the summer of 1987, showing maximum ice depths of 550 m. The annual ice flux through the transverse profile was estimated as 5.67 × 107 m3, which corresponds to a mean annual ice loss from the glacier surface below the profile of 8.10 m of ice.
Parameterization of the Annual Surface Temperature and Mass Balance of Antarctica
Authors: Fortuin J.P.F. , Oerlemans J. 
Published: February 2017

This study entails the parameterization, by means of a linear multiple-regression analysis, of the annual surface temperature and mass balance of Antarctica. The analysis was performed for the entire ice cap as well as for three separate regions: ice shelves (elevation less than 200 m), the interior (elevation above 1500 m), and the escarpment region in between. It was found that temperature can be parameterized very well in terms of elevation and latitude. The latitudinal gradient on the ice shelves can be explained by the super-adiabatic lapse rate along the surface and latitudinal temperature gradient in the interior, assuming adiabatic descent of air in the inversion layer from the interior region towards the coast and an axisymmetric spreading over the ice shelves. The surface mass balance can be parameterized reliably only in the interior, where it has a strong positive correlation with the saturation vapour pressure of the free atmosphere, and a significant correlation with the shape of the dome. The convex shape of the dome contributes to the mass balance by inducing subsidence of the relatively moist air of the free atmosphere into the inversion layer. This results in precipitation, as radiative cooling in the inversion exceeds adiabatic warming. An estimate is made of the annual horizontal and vertical advective velocities in the free atmosphere above the interior, based on regression results and a physical analysis of the precipitation processes in this region.
A temperature sensitivity analysis was performed for the current mass-balance distribution. For a 1 K. rise in surface temperature, the regression estimate of the increase in accumulation on the grounded ice sheet is equivalent to a rate of sea-level lowering of 0.2 mm a−1. This is about 30% less than estimates based on the current mass balance perturbated by the increase in saturation vapour pressure of the free atmosphere.
The Mass Balance Of Blue Glacier, Washington, U.S.A. 1956–1986
Authors: L. Armstrong Richard 
Published: February 2017

Mass-balance data for Blue Glacier are presented for the 31-year period 1956–86. The glacier location is strongly maritime with annual precipitation of 3500 to 5000 mm, most of which falls as winter snow. The low elevation of the glacier results in large amounts of summer ablation and thus significant annual mass exchange. Blue Glacier has been in approximate equilibrium with recent climate during the past 30 years with a slightly positive mean annual net balance of 0.3 m and a terminus advance of 150 m. Comparison with other glaciers in western North America indicates that this pattern of mass increase in response to recent climate is not typical but may be specific to a maritime location.
Due to heavy amounts of winter snowfall, an accumulation area ratio of only 0.5 is sufficient to maintain a zero balance on Blue Glacier. A strong gradient of increasing snowfall with elevation contributes to a linear relationship between net balance and elevation throughout the total altitude range of the glacier. This relationship is consistent over the period of record and is not dependent on an overall net positive balance, as the pattern persists even during periods of strongly negative mass balance. A relationship between measured mass balance and equilibrium-line altitude provides a reasonable method to compute mass balance.
Annually-Averaged Polar Sea-Ice Extents During 1978–1987: Northern Extent Decrease and Southern Extent Oscillation
Authors: Gloersen Per , J. Campbell William 
Published: February 2017

Recently reported observations of a nine-year decrease in global sea-ice extent, obtained from the Scanning Multichannel Microwave Radiometer onboard the Nimbus-7 satellite during 1978–87 and averaged with an annual running mean, have been separated into Arctic and Antarctic components. The annually-averaged global extent decrease was 2.5%. Here it is shown that the greater part of this decrease occurred in the Arctic where there was a decline of 3.5% with a goodness of fit of 0.54.
Superimposed on this decline was a small oscillation with a period of about four years and an amplitude of about 1%. A significantly smaller and statistically insignificant decrease of 1.2% with a goodness of fit of 0.03 is observed in the annually averaged Antarctic sea-ice extent. However, three large oscillations with amplitudes of about 4% and periods of about three years occurred in phase with three El Niño events.
Climatic Warming, Glaciers and Sea Level
Authors: Koerner R.M , Fisher D.A. 
Published: February 2017

The modern concensus outside of the glaciological community is that “greenhouse” gases, released by human activity, will cause an unprecedented temperature rise over the next 100 years and thereby cause a socially-threatening rise of sea level. With respect to ice the concept is simple: warmer means less. The relationship between glaciers and climate is much more complex than this. Warmer also means more vapour transport and there is ample evidence from both theory and ice-core data that snow accumulation rates in both Greenland and Antarctica were lower during the last glacial period. The problem is whether the increased accumulation rates will be exceeded by increased melting of ice in the ablation areas. Antarctica could play a dominant role because of its size and very low temperatures. Only a small percent of Antarctica will increase its meltwater run-off into the ocean. Furthermore, its dynamic response time is so large that the calving rate will not change over a 200-year period. Most of the increased melt will be absorbed in the firn and the question is how much the snow accumulation rate will increase over the major part of the continent.
In the northern hemisphere one has to consider the way in which the warming will manifest itself seasonally. Most of the “forecasts” indicate that most of the warming will occur in the winter rather than the summer. In this case one has to consider the balance between greatly increased winter snowfall rates and only slightly increased summer melt rates. In this respect a review of the snow accumulation and ice melt rates from different glaciers and ice caps in the Canadian Arctic Islands is pertinent. Over the past 20 to 30 years we see no sign of a trend of either side of the balance equation (accumulation, melt). Is this the effect of high noise levels or is there simply no trend?
Finally, we review the ground-ice potential in terms of sea-level change. Ground ice may not form a large part of the world's ice reserves but it covers a large area. Both increased snowfall rates in winter, and summer warming will move to increase the thickness of the active layer. This will result in run-off to the oceans.
Global circulation models might be modified to determine a “best guess” of future sea-level change. To do this they must incorporate all of the parameters considered in this paper.
26-Year High Resolution Profile Of Major Anions In Snow From Coats Land, Antarctica
Authors: Mulvaney R. , Peel D.A. , Reid A.P. 
Published: February 2017

In January 1987, an 7.8 m core, with an age at the bottom of 26 years, was collected from a site approximately 150 km inland from Halley Station (77°02.2′S, 22°32′W; altitude 1862 m a.s.l.); 10 m temperature ≈ −30°C; accumulation rate ≈ 14 g cm−2 a−1). The site lies some 140 km from the coast of the Weddell Sea and within the area bounded in winter by the polar vortex.
The core has been analysed at a frequency of ≈28 samples per accumulation year for sulphate, nitrate and chloride, and has been dated stratigraphically from the clear seasonal cycles in non sea salt sulphate (Mulvaney and Peel, 1988). With this resolution it is possible to examine the seasonal pattern of deposition of chemical species and their phase relationships.
Of particular interest is the possibility that ice cores may preserve evidence for disturbances in tropospheric chemistry, associated with the recent spring-time depletion of stratospheric ozone. It has been proposed that this is accompanied by a denitrification of the stratosphere during the winter months, implying enhanced levels of NOX in the late winter/spring troposphere and in precipitation. Our data reveal a strong seasonal signal in nitrate deposition, apparently peaking in spring. Similar behaviour has been reported by Wagenbach and others (1988) for nitrate in the atmospheric aerosol, in a 3-year sequence (1983–86) from Georg von Neumayer Station (70°S, 8°W). There does not appear to be any evidence in our data of an increase in spring-time nitrate deposition since the appearance of the Antarctic ozone hole in 1978.
Can Milankovitch Variations Initiate The Growth Of Ice Sheets In A Global Circulation Model?
Authors: Rind David 
Published: February 2017

The GISS climate model is used to investigate whether the growth of ice sheets could have been initiated by solar insolation variations. Three different orbital configurations are used, corresponding to 116 000 yr B.P., 106 000 yr B.P., and a modified insolation field with greater reductions in summer insolation at high northern latitudes. The time periods chosen are those in which geophysical evidence implies that ice sheets were growing rapidly.
The results show that the model fails to maintain snow cover through the summer at locations of suspected initiation of the major ice sheets, despite the reduced summer insolation. When 10 m-thick ice was inserted in all locations where continental ice sheets existed during the last glacial maximum, the model failed to maintain it as well: the ice would melt away in less than five years. Only cooling the ocean to its full ice-age value allowed the model to keep any of the additional ice, and then only in a very restricted region in northern Baffin Island.
The experiments indicate there is a wide discrepancy between the model’s response to Milankovitch variations and the geophysical evidence of ice sheet initiation. As the model failed to grow or sustain low-elevation ice during the time of high latitude maximum solar radiation reduction (120 000–100 000 yr B.P.), it is unlikely it could have done so at any time within the last several hundred thousand years. Either the model is not nearly sensitive enough, or we do not understand the connection between Milankovitch variations and the growth of ice sheets.
Impurity Distributions In Ice Under Different Environmental Conditions
Authors: Wolff Eric , Mulvaney Robert 
Published: February 2017

We have shown previously (Mulvaney and others, 1988; Wolff and others, 1988) that some of the impurities in ice are localised. For samples from Dolleman Island in the Antarctic Peninsula, sulphuric acid was found at very high concentrations at the triple junctions (where three grains meet). No such localisation was found for sea salt elements, which are the other major soluble impurity. We believe that the acid is sufficiently concentrated at ice-sheet temperatures to remain liquid, forming a network of sub-micron veins through the ice.
We used a scanning electron microscope (SEM) fitted with an X-ray microanalysis system and a cold stage that holds samples below −160°C. Located at the University of Lancaster, the instrument allows frozen samples to be investigated with elemental analysis carried out at a resolution of the order of 1 micron.
Further experiments have yielded similar results for other samples from the same ice core. However, we have not yet found a method of cutting and cooling the samples that gives quantitatively reproducible data, so that it is too early to say what proportion of the acid in the sample is at the triple junctions.
Nonetheless, we have now also seen S at several triple junctions in ice from Site G in central Greenland. The sample includes part of the material from the 1783 Laki volcanic eruption. We have still to look at samples from other sites, but are reassured that the positive result is not confined to one ice core.
This work, still at a formative stage, has posed some important questions:
(1) For us there is the technical question of how we obtain reproducible quantitative results.
(2) How widespread is the phenomenon, and how much of the acid is at triple junctions? This is the next phase of studies at Lancaster, and is likely to include a study of older ice, and of temperate ice.
(3) Why is the acid at triple junctions, and why is sea salt not found there? This must be due to processes in the atmosphere or snowpack, and is likely to be related to the eutectic temperatures of impurity/water mixtures. Thus the distribution may influenced by changes in climate or chemistry. For instance, Wisconsin-age ice in Greenland is neutral, any acid having reacted with alkali dusts. How did this affect the impurity distribution?
(4) If the distribution does change as a result of a changed environment, does this affect the physical properties of the ice itself? In particular, is the presence or absence of liquid at the junctions a contributory factor to the changes in rheology between Wisconsin and Holocene ice? We are far into the realms of speculation here, but this does have the potential to be an interesting long-timescale feedback to climatic and environmental changes.
Measurement of Avalanche Speeds and Forces: Instrumentation and Preliminary Results of the Ryggfonn Project
Authors: Norem H. , Kvisterøy T. , Evensen B. D. 
Published: February 2017

The Ryggfonn project is a Full scale experiment carried out to investigate the impact of avalanches on structures and the effects of a retaining dam in the avalanche path. The vertical drop of the avalanche path is 910 m and the volume of the avalanches is 20 - 100 000 m3.The experimental set-up consists of: a 15 m high retaining dam in the runout zone, instrumented with strain gauges on a 6.5 m steel mast and a load cell on a 1.0 m mast, plus a 4.5 m high concrete structure instrumented with three 0.72 m2load cells, and three transmission line conductors strung across the avalanche path. The recorded analogue signals are digitized using Pulse-Code-Modulation (PCM) and recorded on a magnetic tape recorder.Up to May 1984, speed data from five avalanches have been analysed, and impact pressures have been recorded from three of them. The maximum speeds vary between 38 m/s and 60 m/s. The maximum recorded impact pressure was 541 kPa, and averaged 220 kPa over a 15 second interval. A maximum pressure of 83 kPa was measured on a load cell buried under snow at the base of the concrete structure.
Friction of melting ice
Authors: Jones Stephen J. , Kitagawa H. , Izumiyama K. , Shimoda H. 
Published: February 2017

The friction of pure ice against various materials was studied at the melting point by pulling plates of the materials of known roughness under a melting ice sample, which was loaded from above, and by maintaining a surrounding air temperature of +2°C (±1°C). Speed was varied over a wide range from 0.05 to 400 mm s−1.
Results for an aluminium sheet of roughness Ra
= 0.84 μm, showed a maximum in friction coefficient of 0.04 at a speed of 16 mm s−1. Below this speed the friction coefficient dropped to 0.002 at 0.2 mm s −1 and results from different ice samples were very reproducible. Above 16 mm s−1, the friction coefficient initially dropped to about 0.002 at 100 mm s−1, and then increased again to 0.037 at 400 mm s−1. Results at speeds above 16 mm s−1 were much less reproducible than those at lower speeds. Results are given also for the friction of ice on Formica, acrylic, and copper plates.
The amount of meltwater produced during a test was measured by weighing an absorbent tissue before and after mopping-up the meltwater. The amount of meltwater was significantly more for aluminium than for Formica or acrylic, showing that the thermal conductivity of the slider was controlling the amount of meltwater. The amount was also a strong function of velocity.
The dynamic friction characteristics of a rapidly sheared granular material applied to the motion of snow avalanches
Authors: Dent J.D. 
Published: February 2017

A numerical simulation of simple two-dimensional shear of round uniform grains is used to investigate the dynamic friction characteristics of the layer of snow at the base of an avalanche. For steady, uniform flow on a uniform flat surface, the dynamic friction coefficient transmitted through the shear array is found as it varies with the shear speed and normal force applied to the top of the shear layer, and the properties of the particles in the shear layer.
For this simple model, the flow in the shear layer is found to be independent of the total number of layers in the shear flow. A slip plane is formed along which most of the shearing motion takes places, so that the shear is confined to just two layers of particles which slide over one another. In the absence of gravity this slip plane jumps up and down randomly within the shear layer, which is otherwise composed of agitated semi-dispersed particles.