bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative Importance of Lateral and Vertical Shear on Rutford Ice Stream, Antarctica
Authors: Frolich R. M. , Doake C. S. M.
Published: February 2017

Survey data from three transverse profiles across Rutford Ice Stream show that most of the shear deformation occurs in boundary layers about 10 km wide on both sides of the glacier. There is a central part, also about 10 km wide, where lateral shear-stress gradients are not significantly different from zero. This implies that friction from the side walls does not impede the flow in the middle of the glacier. Instead, a basal shear stress of around 40 kPa is required in order to provide the necessary restraint. Even then, only a small proportion of the forward movement will be caused by internal deformation of the ice and the remainder must arise from sliding or rapid deformation at or near the base of the glacier. Although the present analysis does not consider in detail the variation with depth in stresses and strain-rates, the formulation of the problem suggests that a self-consistent solution can be found for the distribution of basal and vertical shear stresses.
Floods Caused by a Glacier-Dammed Lake at the Folgefonni Ice Cap, Norway
Authors: Tvede Arve M.
Published: February 2017

The River Londalselva drains a part of the Søndre Folgefonni ice cap. On maps showing the topography of the basin, two potentially glacier-dammed lakes can be identified, the lakes of Blomsterskardvatn and Sauavatn. Four large floods occurred in the late summer or early autumn periods of the years 1938, 1944, 1948, and 1962, resulting in great damage to the farms in the settlement of Mosnes. After each of the earlier floods, river-protection work was carried out, but after the 1962 flood further protection efforts were considered too expensive and so the settlement was abandoned by its farmers in the mid-1960s. Originally, the floods were believed to result from the emptying of Blomsterskardvatn. However, field studies have revealed that in fact the floods actually orginated in Sauavatn. This paper suggests a possible flood-prevention measure, based on the construction of a 400 m long tunnel from Sauavatn, which would keep water levels low. The cost is estimated at approximately 5 million Norwegian kroner (NOK.) based on an exchange rate of 6.9 NOK = 1 $US in September 1988. The paper also stresses the importance of making proper hydrological investigations in other cases of flood.
Interpreting the Field Evidence of Past Ice Sheets: Structural Stability and Genericity
Authors: Nye J.F.
Published: February 2017

Ice sheets are always advancing or retreating, and these processes are not uniform along the ice edge. The result is that lines of maximum and minimum extent are envelopes of successive instantaneous ice edges. Generically, the envelopes can possess only two kinds of special points: crossings and cusps. These will often be arranged in characteristic patterns (unfoldings of higher mathematical singularities). The recognition of these features makes possible a novel approach to the interpretation of field evidence. It is shown, for example, how separate families of parallel erosional and depositional features seen at an interior site are related by coming together in lines of cusps at the envelopes, which may be marked by terminal moraines.
A Laboratory Study of Heat Flux Through Coastal Polynyas During Frazil-Ice Production
Authors: Ushio Shuki , Wakatsuchi Masaaki
Published: February 2017

We carried out laboratory experiments with a test tank in a cold room to estimate heat flux through coastal polynyas, which have great effects on climate in the polar regions. The estimation of heat flux from water to air was made with measurements of cooling rate of water temperature and of the rate of ice production as a function of wind speed and water salinity. Both rates increased with increasing wind speed and water salinity. The major factor that governs heat flux is the size of the open water area. In an open water area continuously maintained by a strong cold wind, rapid production of frazil ice and its downwind transport occur simultaneously; so the open water serves as an efficient ice factory. In the case of NaCl solution, supercooled water with salinity greater than 23.1‰ is denser than water at its freezing point. Therefore, the formation and sinking of the supercooled water occur in the persistent open water; this results in great lowering of water temperature and underwater-ice production. Strong wind and high salinity enhance the supercooling effect.
Relationship between tidewater glacier calving velocity and water depth at the calving front
Authors: Pelto Mauri S. , Warren Charles R.
Published: February 2017

An analysis of the relationship between iceberg calving rates and water depth has been completed for 22 tidewater glaciers. A linear relationship provides reasonable accuracy, with a correlation coefficient of 0.85, for all tidewater glaciers examined, whether they be polar or temperate. The polar glaciers have a slightly lower calving rate for a given water depth. This relationship indicates a lower calving rate for water depths over 50 m than determined by Brown and others (1982). It is based only on glaciers or ice streams and cannot be applied to ice shelves.
Ice Front Fluctuations in the Eastern and Southern Weddell Sea
Authors: Lange Manfred A. , Kohnen Heinz
Published: February 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.
Evaluation of the snow-removal options in an urban area based on the preferences of inhabitants
Authors: Miyakoshi Kazuhiro , Matsumoto Shoji
Published: February 2017

Basically there are three kinds of snow removal: mechanical snow removal (MSR), snow-thawing pipe systems (STP) and snow-conveying open channels (SCOC). This paper identifies inhabitants’ attitudes toward snow-removal options and quantitatively evaluates their preferences by applying the Analytical Hierarchy Process (ΑΗΡ) method. A hierarchy is specified separately for the road in front of a house and the site of a house. A case study carried out for citizens living in the city of Ojiya in Niigata reveals that the space available for walking is an important factor, and hence STP scores considerably higher than SCOC and MSR. For the evaluation of a house site, the frequency per season of removing snow from a roof is the most important factor. House designs for overcoming snow accumulation are also evaluated.
Changes in areal extent, elevation and volume of Athabasca Glacier, Alberta, Canada, as estimated from a series of maps produced between 1919 and 1979
Authors: Reynolds J. R. , Young G. J.
Published: February 2017

Changes in planimetric area, elevation and volume were calculated for Athabasca Glacier, Alberta, Canada, below 2400 m elevation for the period 1919–79 from maps produced using aerial or terrestrial photogrammetry. Map contours were digitized and converted into raster digital elevation models (DEMs). Comparison of the models allowed changes in volume and elevation to be estimated. In the time of record, the glacier lost 2.344 × 108 m3 of volume and downwasted significantly.

There are several sources of error associated with DEM generation and construction: source maps have spatially variable uncertainty in vertical estimation, associated with the photogrammetric process used; small errors are introduced in the creation of raster DEMs as a result of fitting surfaces to digitized contours; errors of registration, leading to errors in estimation of vertical change over time, can be of significance, especially when comparing maps produced by different photogrammetric techniques.

These errors are quantified and displayed in transect and map form. Especially with maps only 2 years apart in time, errors are often greater than actual changes in surface elevation. The magnitude of the errors involved in the comparison of maps made with a 2 year interval would suggest that 5 or 10 years between successive mappings might have been more scientifically justifiable and more cost effective.
Snow and ice applications of AVHRR in polar regions: report of a workshop held in Boulder, Colorado, 20 May 1992
Authors: Steffen K. , Bindschadler R. , Casassa G. , Comiso J. , Eppler D. , Fetterer F. , Hawkins J. , Key J. , Rothrock D. , Thomas R. , Weaver R. , Welch R.
Published: February 2017

The third symposium on Remote Sensing of Snow and Ice, organized by the International Glaciological Society, took place in Boulder, Colorado, 17–22 May 1992. As part of this meeting a total of 21 papers was presented on snow and ice applications of Advanced Very High Resolution Radiometer (AVHRR) satellite data in polar regions. Also during this meeting a NASA sponsored Workshop was held to review the status of polar surface measurements from AVHRR. In the following we have summarized the ideas and recommendations from the workshop, and the conclusions of relevant papers given during the regular symposium sessions. The seven topics discussed include cloud masking, ice surface temperature, narrow-band albedo, ice concentration, lead statistics, sea-ice motion and ice-sheet studies with specifics on applications, algorithms and accuracy, following recommendations for future improvements. In general, we can affirm the strong potential of AVHRR for studying sea ice and snow covered surfaces, and we highly recommend this satellite data set for long-term monitoring of polar process studies. However, progress is needed to reduce the uncertainty of the retrieved parameters for all of the above mentioned topics to make this data set useful for direct climate applications such as heat balance studies and others. Further, the acquisition and processing of polar AVHRR data must become better coordinated between receiving stations, data centers and funding agencies to guarantee a long-term commitment to the collection and distribution of high quality data.
Description of a program for SAR investigation of the Greenland ice sheet and an example of margin change detection using SAR
Authors: Fahnestock Mark A. , Bindschadler Robert A.
Published: February 2017

In order to interpret changes in the Greenland ice sheet as indications of climatic variation, it is necessary to place observations of local changes in a regional context. This requires a comprehensive monitoring effort which addresses both the inland ice and changes in the ice margin. This paper describes the design of a program for regional investigation of the Greenland ice sheet using synthetic aperture radar (SAR), and discusses the utility of SAR data for detection of change in the ice sheet margin.

Comprehensive coverage of the Greenland ice sheet by ERS-1 SAR will allow us to map the boundaries of snow facies on the ice sheet and investigate recent changes in the ice margin. We will use geo-referenced images to map the current boundaries of snow facies, providing a baseline which can be used to detect future change.

We demonstrate the utility of SAR for detecting recent changes in the ice margin. SAR images clearly show the ice edge, moraines, and ice marginal lakes. These features can be compared with published maps and earlier images in order to document changes in the margin of the ice sheet. We show evidence for recession of a section of the western margin of the ice sheet. The recession, which occurred between 1938 and 1978, ranges from a few hundred meters at high elevations to several kilometers at calving faces in both ice marginal lakes and fjords.

ERS-1 SAR will provide the first opportunity to pursue a comprehensive investigation of the state of the Greenland ice sheet. The ability to address conditions on the ice and to look at margin changes in a systematic way will allow us to develop a stronger framework for interpreting changes in the ice sheet in terms of climatic variation.
Characteristics of the water balance of the moshiri experimental watershed, Japan
Authors: Ishikawa N. , Takeuchi Y. , Ishii Y. , Kodama Y.
Published: February 2017

Seasonal variations of water-balance components at an experimental watershed were measured for three hydrologic years. Snowfall accounts for 47% of the annual precipitation, and snowmelt runoff comprises 45% of the total runoff. Evaporation changed markedly during the season; it increased during May to August, decreased in September and October, and was negligibly small during the period of snow cover in winter. Losses due to evaporation reached half of the precipitation during summer, and total loss is about 26 % of the annual precipitation.
Modeling the Antarctic ice sheet
Authors: Verbitsky Mikhail , Saltzman Barry
Published: February 2017

A three-dimensional (3-D), high-resolution, non-linearly viscous, non-isothermal ice-sheet model is employed to calculate the “present-day” equilibrium regime of the Antarctic ice sheet and its evolution during the last glacial cycle. The model is augmented by an approximate formula for ice-sheet basal temperature, based on a scaling of the thermodynamic equation for the ice flow. Steady-state solutions for both the shape and extent of the areas of basal melting (or freezing) are shown to be in good agreement with those obtained from the solution of the full 3-D thermodynamic equation. The solution for the basal temperature field of the West Antaretie Siple Coast produces areas at the pressure-melting point separated by strips of frozen-to-bed ice, the structure of which is reminiscent of Ice Streams A–E. This configuration appears to be robust, preserving its features in spite of climatic changes during the last glacial cycle. Ice Stream C seems to be more vulnerable to stagnation, switching to a passive mode at least once during the penultimate interglacial. We conjecture that the peculiarities of local topography determine the unique behavior of Ice Stream C: reduced basal stress and, consequently, relatively weak warming due to internal friction and basal sliding is not able to counteract the advective cooling during the periods of increased snowfall rate.
The interaction between drifting snow and atmospheric turbulence
Authors: Bintanja Richard
Published: February 2017

This paper presents a modelling study of the influence of suspended snow on turbulence in the atmospheric surface layer. Turbulence is diminished in drifting and blowing snow, since part of the turbulent energy is used to keep the particles in suspension. This decrease in turbulence directly affects the vertical turbulent fluxes of momentum and snow particles (and other scalars), and can effectively be simulated by introducing an appropriate Richardson number to account for the stability effects of the stably stratified air-snow mixture. We use a one-dimensional model of the atmospheric surface layer in which the Reynolds stress and turbulent suspended snow flux are parameterized in terms of their mean vertical gradients (first-order closure). The model calculates steady-state vertical profiles of mean wind speed, suspended snow mass in 16 size classes and stability parameters. Using the model, the influence of snowdrifting on the wind-speed profile is quantified for various values of the initial friction Velocity (which determines the steepness of the initial wind-speed profile). It will be demonstrated why the roughness length appears to increase when snowdrifting occurs. Finally, we present a parameterization of the effects of snowdrifting on atmospheric stability which can be used in data analyses as a first-order approximation.
Antarctic moisture flux and net accumulation from global atmospheric analyses
Authors: Budd W.F. , Reid P. A. , Minty L.J.
Published: February 2017

Previous attempts to derive the Antarctic surface net accumulation distribution from atmospheric-moisture fluxes, in reasonable agreement with the observed distribution, have encountered many difficulties. The present analysis uses the Australian Bureau of Meteorology Global Atmospheric Assimilation and Prediction Scheme (GASP), which has been operational since 1989, to derive the net air-mass and moisture fluxes over the Antarctic. It is shown that the annual mean net surface accumulation closely resembles the glaciologically observed distribution and provides a physical basis for the observed pattern, through the moisture transports. The variations with latitude and elevation and through the annual cycle are also well reproduced. Although some mass-closure errors still exist, they are expected to become insignificant with the new generation of improved analysis schemes. Consequently the atmospheric analyses can provide a sound basis for both assessing the performance of global climate models in simulating Antarctic accumulation rates and monitoring long-term changes which may occur with global warming.
The influence of the albedo-temperature feed-back on climate sensitivity
Authors: Bintanja Richard , Oerlemans Johannes
Published: February 2017

A vertically integrated, zonally averaged energy-balance climate model coupled to a two-dimensional ocean model with prescribed overturning pattern is employed to assess the seasonally and latitudinally varying response of the climate system to changes in radiative forcing. Since the sensitivity of the climate system depends on its actual state, considerable attention is given to the correct simulation of the important features of the present-day climate (such as surface air temperature, sea-ice and snow amount and meridional energy transport). The climate variability induced by the various elements of the albedo-temperature (e.g. sea-ice and snow) feed-back is quantified. It appears that the variability caused by sea-ice variations is approximately twice as large as for snow variations.
Temporal variations of microwave brightness temperatures over Antarctica
Authors: Sherjal I. , Fily M.
Published: February 2017

Passive microwave brightness temperatures from the Special Sensor Microwave Imager (SSMI) are studied together with surface air temperatures from two Automatic Weather Stations (AWS) for the year 1989. One station is located on the East Antarctic plateau (Dome C) and the other on the Ross lee Shelf (Lettau).The satellite data for frequencies 19, 22 and 37 GHz with vertical polarization,centered on the two AWS stations, are studied. A simple thermodynamic model and asimple radiative-transfer model, that takes into account the snow temperature profile and assumes a constant annual emissivity, are proposed. The combination of these two models enables us to compute extinction coefficients, penetration depths and toretrieve the measured brightness temperature variations from the AWS surface temperatures. Afterwards, this model is reversed in order to retrieve the snow-surface temperatures from the satellite data. Results are promising but strong approximationsand a priori knowledge of the extinction coefficient are still needed at this point.
Recent advance of the grounding line of Lambert Glacier, Antarctica, deduced from satellite-radar altimetry
Authors: Herzfeld Ute C. , Lingle Craig S. , Lee Li-Her
Published: February 2017

Satellite radar-altimeter data from Seasat (1978) and the Geosat Exact Repeat Mission (1987–89) are evaluated to investigate the question of advance or retreat of Lambert Glacier, Amery Ice Shelf, East Antarctica. New maps based on a fine-scale 3 km grid arc calculated using ordinary kriging. The break in slope at the 100 m elevation contour, relative to the WGS 1984 ellipsoid, is taken as a proxy for the grounding line. Measurements indicate that the irregular grounding line, which includes shoals, advanced approximately 10km between 1978 and 1987‐89, corresponding to a mean advance rate of about 1000 m year-1.
A digital elevation model of the Antarctic ice sheet derived from ERS-1 altimeter data and comparison with terrestrial measurements
Authors: Bamber Jonathan L.
Published: February 2017

The launch of ERS-1 provides coverage, by satellite altimetry, of 80% of the Antarctic ice sheet, allowing topographic mapping of areas which previously had a dearth of accurate elevation data. Four 35 d repeat cycles of fastdelivery altimeter data were used in this study, comprising a total of approximately 1000000 height estimates. About 40% of these were rejected during a careful filtering procedure designed to remove erroneous values caused by poor tracking or complete loss of the returned echo. The OSU-91A geopotential model was used to convert ellipsoidal elevations to geoidal values. Corrections for surface slope were applied and a Digital Elevation Model (DEM) was produced with a grid spacing of 20km.

The precision of the data was assessed from an analysis of crossing points of ascending and descending tracks. For 43864 cross-overs, the standard deviation was 6.8m. Regional biases associated with geoid, orbit and topography-induced errors reduce the accuracy of the height measurements. This was assessed by a comparison with ground-survey data. The DEM was compared with a 700km levelling survey, with an accuracy ranging from 1 to 5m, from the Lambert Glacier basin region (≈73° S, 55° E). The mean difference was found to be-1.6m with a standard deviation of 14m. A similar result was obtained for a 600km traverse line in Wilkes Land (75° S,≈1l0° E).

The DEM was then compared with a digitized version of the Scott Polar Research Institute (SPRI) Antarctic folio map. This map was derived from orthometric measurements of surface elevation, primarily from pressure altimetry. Differences in excess of 300 m were observed between the two data sets. Only 37% of the region covered showed agreement to better than 50m, and a significant proportion ofthis was composed of the Ross and Filchner-Ronne Ice Shelves. The largest discrepancies occurred in marginal areas where there is poor coverage by both satellite altimetry and terrestrial data. Inland, significant differences were also found.
Morphology and late Cenozoic (<5 Ma) glacial history of the area between David and Mawson Glaciers, Victoria Land, Antarctica
Authors: Verbers Anja L.L.M. , Damm Volkmar
Published: February 2017

Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and Mawson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak clusters dissected by glaciated valleys with ice thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accelerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. When the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial Maximum the ice surface has lowered by about 100 m.
Small-Scale variability of physical properties and structural characteristics of Antarctic fast ice
Authors: Veazey A.L. , Jeffries M.O. , Morris K.
Published: February 2017

The small-scale variability of physical properties and structural characteristics of multiple pairs of fast-ice cores obtained during the austral summer of 1991-92 at two Antarctic sites, McMurdo Sound (MCM) and Pine Island Bay (PIB), are examined and discussed with respect to the growth and decay of the sea ice. The ice at the MCM site was thicker than that at the PIB site and was covered by a somewhat thinner snowpack. While mean salinity and temperature of the ice at the two sites were similar, small-scale variations in both salinity and temperature were greater at PIB than at MCM. The ice sheet at MCM was a two-layer medium consisting of congelation ice overlying platelet ice. The ice from the PIB site, however, was composed of mainly frazil ice and layers of congelation ice with occasional thin layers of snow-ice at the surface of the cores. Crystal sub-structure measurements, c-axis orientation and brine-layer spacing from the MCM cores revealed that the congelation ice had moderately aligned, horizontally oriented c axes, suggesting that east-west currents off the southwest tip of Hut Point Peninsula control crystal-growth orientation.d others: Variability of physical and structural characteristics of Antarctic fast ice
A two-dimensional finite-element study of flow in the transition zone between an ice sheet and an ice shelf
Authors: Lestringant Renaud
Published: February 2017

A numerical study has been carried out on the flow of ice in the transition zone between an ice sheet and an ice shelf. The study was motivated by the need for global ice-sheet-ice-shelf modelling to determine the characteristics of the transition zone. The problem is dealt with from an academic viewpoint, and the study especially focuses on two-dimensional vertical sharp transition zones. Stokes equations are solved using a finite-element method. Conclusions include: (1) in ice-sheet-ice-shelf modelling, each of the two components can be computed separately then linked by a jump-boundary condition [or the horizontal velocity; (2) as shown by studies on the response of an ice shelf to tidal forcing, the surface elevation/thickness ratio passes through the hydrostatic equilibrium value.
Effects of temperature and pressure on the transformation rate from air bubbles to air-hydrate crystals in ice sheets
Authors: Uchida Tsutomu , Hondoh Takeo , Mae Shinji , Duval Paul , Lipenkov Volodya Ya
Published: February 2017

Experimental investigations on the formation and growth processes of air-hydrate crystals were carried out to determine the transformation process of air bubbles into air-hydrate crystals in deep ice sheets. The microscopic observations revealed that the transformation began at the boundary between a bubble and ice. Faster transformation occurred along the boundary and, subsequently, the transformation progressed towards the center of the bubble at a lower rate. Each transformation rate increased with pressure and also with temperature. The activation energy of the transformation was about 0.52 eV for the primary transformation process and about 0.90 eV for subsequent processes. These results indicate that the rate determining the process of transformation is mainly supplementation of water molecules to the transformation site. An estimation of the transformation period of an air bubble into an air-hydrate crystal in a deep ice sheet reveals that it is about one thousandth of the time period of the transition zone, where both air-hydrates and air bubbles exist
c axes from radar depolarization experiments at Upstream B Camp, Antarctica, in 1991–92
Authors: Liu C. , Bentley C. R. , Lord N. E.
Published: February 2017

Thirty-nine 50 MHz radar polarization experiments were performedin 1991–92 near Upstream B Camp, Antarctica, along two lines perpendicular to flow,1.4 and 2 km long and 900 m apart. For each of the experiments, which were at 100m intervals, the receiving antenna was held fixed, alternately parallel and perpendicular to flow, while the transmitting antenna was rotated in 15°increments through a full circle twice, once for each orientation of the receiving antenna. The data consist ofecho-amplitude measurements from the bottom of the ice. Assuming a model of the ice sheet as a crystalline medium with axial symmetry, the azimuths of the symmetry axis and the cosines of the phase shifts between extraordinary and ordinary waves can beestimated from the variations in amplitude with orientation of the transmitting antenna. The results from bottom echoes show an abrupt change in the axis of symmetry in a distance of only 100m. This suggests that the experimental lines crossthe boundary between two blocks of ice with different stress histories.
Ice Stream C, Antarctica, sticky spots detected by microearthquake monitoring
Authors: Anandakrishnan S. , Alley R. B.
Published: February 2017

Microearthquakes at the base of slow-moving Ice Stream C occur many times more frequently than at the base of fast-moving Ice Stream B. We suggest that the microearthquake source sites are so-called “sticky spots”, defined as limited zones of stronger Subglacial material interspersed within a weaker matrix. The fault-plane area of the microearthquakes (O(102m2)) is therefore a measure of the size of the sticky spots. The spatial density of the microearthquakes (O(10 km-2)) is a measure of the distribution of sticky spots.

The average stress drop associated with these microearthquakes is consistent with an ice-stream bed model of weak subglacial till interspersed with stronger zones that support much or all of the basal shear stress. We infer a weak inter-sticky-spot material by the large distances (O(103m)), relative to fault radius, to which the microearthquake stress change is transmitted.
Seasonal variations of major ionic concentration levels in drifting-snow samples obtained from east Dronning Maud Land, East Antarctica
Authors: Osada Kazuo
Published: February 2017

Drifting-snow samples were collected at Mizuho Station (74°42' S, 44°20' E, 2230 m a.s.1.) from February to October 1986 and along traverse routes in east Dronning Maud Land (1800-3000 m a.s.1.), East Antarctica, from October 1986 to January 1987. The typical sampling interval was about once a week but two sets of intensive sampling were made at the end of February and November at between 2 h and 1 d intervals

Measurements for CI-, NO3,SO42and Na+ were made on the drifting-snow samples by ion chromatography. Oxygen-isotope ratios were .also measured .on the samples. Concentrations levels ofNO3-and SO4-show distinctive seasonal variations: high in summer (4.6 neq g-1 for NO3and 3.3 neq g1 for SO42) and low in winter during mid-March to mid-November(1.0 neq g1 for NO3 and 0.5 neq g1 for SO42). Results obtained at Mizuho Station show that the transition from the summer high values to winter low values takes about 20 d for NO3 and SO42-.The variations in Cl and Na+ concentration levels are small in both autumn and spring (averages are about 1 neq g-l) with greater variability throughout the rest of the year. The intensive sampling data set shows that there is considerable variability within a day with NO3 and SO42-concentration levels up to about a factor of 4 associated with a 10%0 change in 3180 ratios.
Evaluation of strain rates on Ice Stream B, Antarctica, obtained using GPS phase measurements
Authors: Christina L. Hulbe
Published: February 2017

The “stop-and-go” kinematic Global Positioning System (GPS) technique was used to survey 270 stations twice within a 25 km by 10 km strain grid on the surface of Ice Stream B. One or two geodetic quality receivers operated as reference pivots, while two similar receivers traveled to grid stations. Each station was occupied for 25s. The method is rapid and reliable. Each survey was completed within 2 weeks. Calculated horizontal strain rates are accurate to 1%. Relative vertical velocities are accurate to 20 mm km1a-1. Maps of the four horizontal velocity gradients, relative vertical velocity and surface elevation are presented. The vertical velocity pattern is used to identify the part of the topography that forms stationary waves and that which is migrating. No strong quantitative link is found between the pattern in horizontal strain rate and surface topography. In particular, there is no evidence that the topography is relaxing toward isostasy. None of the “weir-type” sticky spots, which are commonly observed with other glaciers, is found but there could be two of the “submerged-boulder type”, which cause lateral flow diversion. Evidence for “hot stripes” and zones of preferred crystal orientation is not found.
Modelling the Antarctic ice-sheet changes through time
Authors: Budd W.F. , Jenssen D. , Coutts B.
Published: February 2017

A new assessment is made of the possible range of responses of the Antarctic ice sheet to future global warming by performing a series of sensitivity tests to prescribed climatic forcing with an ice-sheet model. The model includes thermodynamics; it is three-dimensional, with 20 km horizontal grid spacing and 30 points in the vertical, and it treats the ice shelves explicitly. To obtain an appropriate initial present state for the ice sheet, it has been necessary to perform a series of simulations through the last glacial cycle with prescribed forcing including accumulation, sea level are less importantly climatic temperature. For the future climatic forcing, General Circulation Model simulations have been used with particular concern for the changes in the sea-ice cover and ocean warming. Effects of progressive changes have been examined with increases of basal-melt rates up to 10 m a1, surface annual mean temperatures by up to 7°C and surface-accumulation rates to double the present values. Without additional accumulation, the increased basal melt of 10 m a-1would greatly reduce the ice shelves and contribute to sea-level rise of 0.3 m in 100 years and over 0.6 m by 500 years. The additional accumulation counteracts this to dive about zero change by 100 years and -1.2 m by 500 years.
Development of enhanced ice flow at the southern margin of Ice Stream D, Antarctica
Authors: Scambos Ted A. , Echelmeyer Keith A. , Fahnestock Mark A. , Bindschadler Robert A.
Published: February 2017

A combination of image-based velocity mapping techniques and finite-element modeling has been used to study a part of the southern shear margin of Ice Stream D, Antarctica. The study area is a region over which the margin shows considerable development morphologically, where a new southern margin is forming in response to an abrupt increase in ice-stream width just upstream of the study area. A series of ice-speed profiles perpendicular to the margin was determined by semiautomated displacement measurements of small ice features in sequential Landsat TM images. Transverse speed gradients ∂u/∂y of these profiles were determined by calculating the slope of a high-order polynomial fit to the speed profiles. Maximum ice speed and ∂u/∂y increase dramatically as the margin develops in the downstream direction, from 420 to 670 mal,and from 0.02 to 0.16 a, respectively. Finite-element modeling of the upstream and downstream profiles suggests that a considerable change occurs in the stiffness of the ice in the marginal zone between the two profiles, and in the stiHness or amount of sliding in the basal layer underlying the margin. Ice in the downstream profile appears to have marginal zones of softer ice in which shear strain is concentrated and uniformly low resistance to deformation in the bed. For the upstream profile, modeling suggests that the ice is not softened near the margin and that the bed is stiffer near the margin. Model-based calculations suggest that the bed shear is responsible for 69% of the resistance to flow in the upstream margin area;this value is 51 % in the downstream area.
A numerical model of blowing snow around an Antarctic building
Authors: Moore I. , Mobbs S.D. , Ingham D.B. , King J.C.
Published: February 2017

The accumulation of drifting snow around buildings in regions of severe climate has important implications on their design and location. This paper studies one such building, at a station run by the British Antarctic Survey and located on the Brunt Ice Shelf at the edge of the Antarctic continent. Four previous stations have been built in the area, the buildings of which were designed to become covered in snow and all have been crushed within a few years. The current station, Halley V, consists of three buildings which are all raised from the ice shelf by means of legs. They were designed in such a way that the action of the wind blowing underneath the buildings would keep them-clear of snow.

This paper describes a model which predicts the shape and position of drift formation, and then compares the results with those observed at Halley. This model is a first attempt to address the problem and as such the paper can be considered to be a progress report; improvements arc currently being made as part of continuing research. It is found that there is some qualitative agreement and possible reasons for a few quantitative discrepancies are discussed. Both the model and the true data show clearly that the new design is very effective in prolonging the useful life of the buildings.
Validating and improving elevation data of a satellite-image map of Filchner,Ronne Ice Shelf, Antarctica, with Results from ERS-1
Authors: Sievers J. , Doake C.S.M. , Ihde J. , Mantripp D.R. , Pozdeev V.S. , Ritter B. , Schenke H.W. , Thyssen F. , Vaughan D.G.
Published: February 2017

A satellite-image map with surface-elevation contours of Filchner Ronne Ice Shelf has been published previously as a topographic map. The image map was constructed from a mosaic of 69 Landsat Multispectral Scanner (MSS) images and NOAA AVHRR data. The standard deviation in position in the central part of the mosaic is ±125m. Topographic-glaciologic features were taken from Landsat scenes and represent the best coastline of this region. Surface elevations have been calculated from airborne and ground measurements of either ice thickness (by assuming hydrostatic equilibrium) or barometric pressure. Accuracies vary from ±2 to ±7 m, Oversnow trigonometric levelling in the northeastern part of the ice shelf, tied to sea level at the ice front, has given accuracies of ± 1m. Accuracies reduce to about ±20 m in the grounded ice areas,

ERS-I radar-altimeter data over the ice shelf have been processed to give ellipsoidal heights elevation above the ellipsoid), Geoidal reductions have been used to convert these to orthometric heights (elevation above sea level). No tidal corrections have been applied. The overall accuracy of the radar-altimeter-derived elevations is estimated to be better than ±5m. There are noticeable differences from the topographic map in the central part where the radar data indicate a lower surface. However, the maps agree to within the stated error figures.
Investigating tidal flexure on an ice shelf using kinematic GPS
Authors: Vaughan David G.
Published: February 2017

The positions of ice-stream grounding zones are uniquely sensitive to changes in the mass balance of the ice sheet. Present methods for locating groundingzone features are either imprecise or require considerable effort in interpretation and so are of little value for change studies. We present a new method which uses the kinematic GPS technique to locate the position of the limit of tidal flexure. The method involves the collection of at least two surface-elevation profiles along the same track through the grounding zone, at different times during the tidal cycle. The elevation profiles obtained coincide upstream of the: limit of flexure but diverge downstream of the limit of flexure. Subtracting the profiles produces a tidal-def1ection profile which shows directly the response of the ice shelf to the tidal forcing.

We present two examples of the use of this method, both on Rutford Ice Stream. Antarctica. The first is across the grounding zone and shows that the method is capable of measuring grounding positions to around 200 m precision. The second, taken across an active shear margin, shows a tidal-deflection profile, with an absence of steps that would indicate the presence of fracture planes penetrating from the ice base to sea level.
Temperature investigation and modeling on the Filchner-Ronne Ice Shelf, Antarctica
Authors: Grosfeld K. , Thyssen F.
Published: February 2017

During the German Antarctic Expedition field season 1989–90. hotwater drilling was undertaken on the Filchner-Ronne Ice Shelf (FRIS) at 77° S 52°c W to investigate the temperature-depth profile and the bottom-melting rate, which arc significant parameters for mass- and energy-balance studies of the ice shelf. Remeasurements of installed chains in 1991-92 yie1ded reliable results.

Taking glaciological, geodetic and geophysical data on a flowline through the central part of FRIS. we developed a two-dimensional thermal model to reconstruct the measurernents from a steady-state temperature depth profile about 550 km upstream on Möllereisstrom. Considering mass and energy conservation, a basal layer of 350 m of marine ice was calculated with thermal properties, depending on salinity and temperature. In areas with strong basal freezing, almost isothermal depth profiles in the marine ice layer are derived. Further downstream, in areas of basal melting, a nearly cubic temperarure-depth profile is observed.
Holocene temperature variations inferred from Antarctic ice cores
Authors: Ciais P. , Jouzel J. , Petit J. R. , Lipenkov V. , White J. W. C.
Published: February 2017

We have reconstructed temperature changes over the past 15 000 years from ice-core data in Antarctica. We used measurements of the D/H isotope ratio in ice as a proxy of temperature for central sites (Vostok, Dome C and Komsomolskaya; as well as coastal sites (D47, D15 and D10). First, we examined the dating of each core and built up a common temporal framework for the ensemble of the data. Secondly, we addressed the problem of inferring small-amplitude temperature fluctuations from the isotope data, in the light of noise-generating mechanisms involved in snow deposition. Temperature was reconstructed so as to minimize distortion created by the sampling of ice cores in the field. The seven ice cores studied yield an average temperature curve which can be put in perspective with nearby paleoclimatic records. The early Holocene experienced climates warmer than today by 1-2°C. The late Holocene period shows more discernible, shorter-duration, temperature fluctuations, superimposed on a fairly stable "base-line" temperature.
Homo Pedagogicus:The evolutionary nature of second language teaching
Authors: Atkinson Dwight
Published: February 2017

Second language (SL) teacher educators tirelessly teach others how to teach. But how often do we actuallydefineteaching? Without explicit definitional activity on this fundamental concept in second language teaching (SLT), it remains implicit and intuitive – the opposite of clear, productive understanding.

I therefore explore the question, ‘What is teaching?’ in this paper. First, I establish the claim that the SLT literature rarely defines teaching explicitly, in part because of its technical ‘how-to’ focus. Second, I offer a heuristic definition of teaching asevolutionarily adaptive behavior(TEAB) – as existing in humans because it enables adaptation to varied and complex ecosocial circumstances. In contrast, animals have quite modest adaptive powers, so it may come as a surprise that TEAB is not uniquely human. Therefore, third, I review research comparing animal and human teaching in order to help us understand the latter better. Fourth, I describe teaching as studied by anthropologists – as it varies across human groups. Formal teaching is relatively rare from an anthropological perspective, and relatively recent at that. Fifth, I employ the results of this definitional exercise to exploratorily examine what happens in SLT classrooms. Finally, I discuss implications and future directions for the ideas presented here and conclude.
Reduplication facilitates early word segmentation
Authors: OTA MITSUHIKO , SKARABELA BARBORA
Published: February 2017

This study explores the possibility that early word segmentation is aided by infants’ tendency to segment words with repeated syllables (‘reduplication’). Twenty-four nine-month-olds were familiarized with passages containing one novel reduplicated word and one novel non-reduplicated word. Their central fixation times in response to these as well as new reduplicated and non-reduplicated words introduced at test showed that familiarized reduplicated words were segmented better than familiarized non-reduplicated words. These results demonstrate that infants are predisposed to segment words with repeated phonological elements, and suggest that register-specific words in infant-directed speech may have evolved in response to this learning bias.
Facilitating Public Service Provision: The Emerging Role of Municipal Television News in China
Authors: Chen Dan
Published: February 2017

Despite strict state controls, negative news about local officials is reported in China. Faced with political constraints and the incentive and pressure to earn profits, municipal television news programmes have developed and adopted the life news model (minsheng xinwen), which aims to help citizens solve problems. The production process of this news model has transformed the political role of the broadcast media at the local level. Many life news reports focus on disputes between citizens and local officials. Thus, addressing citizen grievances essentially facilitates public service provision. Based on an ethnographic case study of a municipal television news programme, this article finds that the production process of life news reports can facilitate public service provision by correcting local officials’ behaviour, regardless of whether the news reports are eventually broadcast. This unintended role is a result of the power negotiation between local officials and journalists who face immense commercial pressure.
The Role of Tunqin Guanxi in Building Rural Resilience in North China: A Case from Qinggang
Authors: Gao Yan , Fennell Shailaja
Published: February 2017

This paper explores the role of guanxi, particularly in its special form of tunqin, in building rural resilience in a poverty-stricken county in north China. The emphasis of this paper is placed on the nature and function of such guanxi. By presenting how guanxi is maintained, this paper also analyses the impact and effectiveness of local guanxi as a strategy to cope with poverty. Whereas tunqin guanxi appears to have built rural resilience in order to cushion villagers against life's upheavals, the maintenance of rural guanxi diminishes this resilience as scarce resources are spent on the exchange of cash gifts, thus aggravating local poverty.
A Simple Approximation for Plate Deflection Problems
Authors: Kaul R. K. , Cadambe V.
Published: February 2017

The problem of bending of thin elastic plates has interested mathematicians and engineers for many years. Various methods have been put forward for determining the approximate solutions among which the variational method of Ritz is most common. This procedure leads to a system of linear simultaneous equations, the solution of which is often quite tedious, although generally by taking a few rows and columns quite accurate results are obtained. The purpose of this note is to show that by using bar eigen-functions for plates which are either clamped, or when some edges are freely supported, certain simplifications can be made in the process and the difficulty of solving simultaneous equations can be avoided; and that the deflection surface of the plate can be derived directly in a series form.