bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calcareous foraminifers from the Bashkirian stratotype (Middle Carboniferous, south Urals) and their significance for intercontinental correlations and the evolution of the Fusulinidae
Authors: Groves John R. 
Published: February 2017

The stratotype for the Bashkirian Stage of the Soviet Middle Carboniferous is located on the Askyn River in Gornaya Bashkiria (western slope of south Urals). Twenty-four rock samples, mostly from the lower part of the section, yielded abundant and diverse assemblages of calcareous foraminifers which are systematically described and illustrated here for the first time.The foraminiferal assemblage from the Siuransky Horizon at the base of the Bashkirian is essentially identical to that from the top of the underlying Lower Carboniferous Serpukhovian Stage. Thus, foraminifers do not provide a basis for identifying the Soviet Lower–Middle Carboniferous boundary. This notwithstanding, the presence of the foraminiferGlobivalvulina bulloides(Brady) (=G. moderataReitlinger) and the conodontIdiognathodus parvus(Dunn) in both the upper Serpukhovian and Bashkirian indicates that the base of the Bashkirian can be no older than medial to late Morrowan of the North American succession. The primitive fusulinidPseudostaffella(Pseudostaffella) appears at the bases of the lower Bashkirian Akavassky Horizon and the North American Atokan Series. The base of the Akavassky is interpreted to be somewhat older than early Atokan, however, becausePs.(Pseudostaffella) appeared in the Urals in phylogenetic continuity with its immediate ancestor, whereas in most of North America it was an immigrant.The type Bashkirian succession contains a seemingly complete phylogeny from advanced eostaffellids to primitive fusulinids.Plectostaffella jakhensis, immediate ancestor to the fusulinids, arose from a member of theEostaffella postmosquensisplexus in the late Serpukhovian.Plectostaffella jakhensis, in turn, gave rise toPs.(Semistaffella)variabilisin the early Bashkirian (late Siuransky), from which evolvedPs.(Ps.)antiquashortly thereafter (earliest Akavassky). An as yet unidentified but advanced species ofPs.(Pseudostaffella) is the most likely ancestor to late BashkirianNeostaffella ivanovi. The evolutionary series leading from theE. postmosquensisplexus to primitiveNeostaffellaapparently developed exclusively in the Eurasian–Arctic faunal realm, asPl. jakhensis, Ps.(Semistaffella)variabilis, andPs.(Ps.)antiquaare unknown in the Midcontinent–Andean region. DiversePs.(Pseudostaffella) spp. appeared in the latter area pursuant to an adaptive radiation aided by periodic interchange between faunal realms.
Impact of deep brain stimulation of the ventral anterior limb of the internal capsule on cognition in depression
Authors: Bergfeld I. O. , Mantione M. , Hoogendoorn M. L. C. , Ruhé H. G. , Horst F. , Notten P. , van Laarhoven J. , van den Munckhof P. , Beute G. , Schuurman P. R. , Denys D. 
Published: February 2017

BackgroundPreliminary studies report no negative and a possible positive impact of deep brain stimulation (DBS) on cognition of patients with treatment-resistant depression (TRD). However, these studies neither controlled for practice effects nor compared active with sham stimulation.MethodTo address these limitations, we compared 25 TRD patients, who underwent DBS of the ventral anterior limb of the internal capsule (vALIC), with 21 healthy controls (HCs) matched on gender, age and education level. Both groups did subtests of the Cambridge Neuropsychological Test Automated Battery assessing verbal and visuospatial memory, attention, cognitive flexibility, psychomotor functioning, planning and object naming. TRD patients were tested 3 weeks prior to DBS surgery (baseline), 3 weeks following surgery (T1) and following 52 weeks of DBS optimization (T2). HCs were tested at baseline, 6 weeks following baseline (T1) and 20–24 weeks following baseline (T2). Subsequently, TRD patients entered a randomized, double-blind crossover phase, in which they were tested in an active and a sham stimulation phase.ResultsTRD patients did not improve on a test of immediate verbal recognition from baseline to T1, whereas HCs did (group x time: p = 0.001). Both TRD patients and HCs improved over sessions on tests measuring delayed verbal recall, visuospatial memory, planning and object naming (all p < 0.01). Active and sham stimulation did not have an impact on any of the tests differentially.ConclusionsvALIC DBS neither has a lasting positive nor negative impact on cognition in TRD patients. DBS surgery might have a temporary negative effect on verbal memory.
Analysis and Simulation of Altimeter Performance for the Production of Ice Sheet Topographic Maps
Authors: Partington K.C. , Rapley C.G. 
Published: February 2017

Satellite-borne, radar altimeters have already demonstrated an ability to produce high-precision, topographic maps of the ice sheets. Seasat operated in a tracking mode, designed for use over oceans, but successfully tracked much of the flatter regions of the ice sheet to ± 72° latitude. ERS-1 will extend coverage to ± 82° latitude and will be equipped with an ocean mode similar to that of Seasat and an ice mode designed to permit tracking of the steeper, peripheral regions. The ocean mode will be used over the flatter regions, because of its greater precision.
Altimeter performance over the ice sheets has been investigated through a study of Seasat tracking behaviour and the use of an altimeter performance simulator, with a view to assessing the likely performance of ERS-1 and the design of improved tracking systems. Analysis of Seasat data shows that lock was frequently lost, as a result of possessing a non-linear height error signal over the width of the range window. Having lost lock, the tracker frequently failed to transfer rapidly and effectively to track mode. Use of the altimeter performance simulator confirms many of the findings from Seasat data and it is being used to facilitate data interpretation and mapping, through the modelling of waveform sequence.
Snow Stratigraphic Studies At Dome C, East Antarctica: An Investigation Of Depositional and Diagenetic Processes
Authors: Palais J. M. , Whillans I. M. , Bull C. 
Published: February 2017

The increased interest in past climatic changes, as revealed by studies of long ice cores from polar ice sheets, has stressed the need for a better understanding of the development of the stratigraphic record preserved in these cores. This paper presents some results of surface investigations at Dome C (74°30'S, 123°10'E), East Antarctica, carried out in austral summers 1978-79 and 1979-80. An explanation is presented of the snow stratigraphy, in terms of depositional and post-depositional processes, that is supported by detailed accumulation measurements at stakes and by snow-pit studies. Temporal and areal variability of snow accumulation are investigated to determine how representative the results interpreted from a single core might be for the Dome C region. Finally, the reliability of several stratigraphic methods for defining annual layers is assessed.
Snow-pit studies show that major depositional features are preserved with depth. Visible annual strata at Dome C are composed of thin, hard crusts overlying thicker layers of soft to medium-hard snow. Low density depth-hoar layers, when they occur, are usually found below the thin, hard crusts. Depth profiles of gross 8-radioactivity and of microparticles concentration exhibit annual cyclicity which, together with the detailed visible stratigraphy, can be used to assign dates to the layers.
Radio Echo-Sounding Of Shirase Glacier And The Yamato Mountains Area
Authors: Wada Makoto , Yamanouchi Takashi , Mae Shinji 
Published: February 2017

In 1979, the National Institute of Polar Research (NIPR) developed a 179 MHz airborne radio echo-sounder (NIPR-A), and installed it in a Pilatus Porter PC-6 aircraft. The peak power of the sounder is about lkW and the pulse width is 0.3 ys. Soundings were carried out in Antarctica on Shirase Glacier and the Yamato Mountains in January 1980. The total flight distance over the Shirase Glacier was about 500 km in six flights, while, on the Yamato Mountains area, about 80 km long, two north-south flights and three eastwest flights were carried out.
In spite of poor wave penetration, the presence of many sub-glacial uplands (1 000 to 2 000 m a.s.l.) near the Yamato Mountains area was revealed. Discussion is concentrated on the bedrock and surface topography of the bare ice area near Motoi Nunatak in the southeast Yamato Mountains, because the previous traverse party covered this area and many meteorites have been discovered here.
A high sub-ice ridge with three peaks extends east of Motoi Nunatak, and from 22 to 28 km east of Motoi Nunatak there is a short ridge with two peaks. From 12 to 20 km up-glacier from Motoi Nunatak, a long but comparatively low ridge surrounds Motoi Nunatak ridge like an arc. Finally, the sub-ice flow lines near Motoi Nunatak are deduced from new and earlier data.
Absolute Movements, Mass Balance, and Snow Temperatures of the Riiser-Larsenisen (Abstract only)
Authors: Gjessing Yngvar , Wold Bjørn 
Published: February 2017

During the Norwegian Antarctic Research Expeditions 1967–77 and 1978–79 a land party worked on Riiser-Larsenisen, an ice shelf 120 km wide on the coast of Dronning Maud Land (15° to 20°W). In February 1977 three patterns of six stakes each were laid out over areas of about 4 km2 as part of a combined investigation into absolute movements and strain-rates. Eight stakes for absolute movement were also laid out. The stakes were also used for determination of mean snow accumulation together with a stake line across the ice shelf. The positions of the stakes were determined by theodolite observations from the stake points and from trigonometric stations located on land and on an ice rise near the ice front.
In February 1979 all these measurements were repeated, and absolute movement, deformation, and mean accumulation were calculated. The absolute velocity of the ice shelf varied from 30 m a−1 near the grounding line to 130 m a−1 near the ice front. The mean annual accumulation was 510 mm water equivalent on the outer part of the ice shelf and 580 mm at the grounding line. Based on these measurements, together with snow-density measurements down to 16 m and measurements of the height of the ice shelf, the mass balance of the ice shelf was studied.
The stake pattern across the grounding line showed considerable expansion. This is interpreted as a result of water freezing in bottom crevasses made by the tides.
In 1979 snow temperatures were measured in eight bore holes down to 10 m depth. The snow temperatures at 10 m depth were used as a measure of the annual mean air temperature. The annual mean air temperature ranged from -16.8°C near the ice front to -19.2°C at the grounding line. Snow temperatures in bore holes on the slope of the ice rise and inland indicate a mean atmospheric temperature inversion of 0.28°C 100 m−1 for a 440 m layer near the grounding line, and 0.30°C 100 m−1 for a 160 m layer near the ice front. Here a mean inversion of 2.8°C 100 m−1 was found for the lowest 40 m layer of the atmosphere.
Temperate Ice Beneath the “Polar” Taylor Glacier, Victoria Land, Antarctica (Abstract only)
Authors: Robinson P.H. 
Published: February 2017

Two interdependent lines of evidence contribute to an understanding of basal ice conditions within Taylor Glacier, from the thermal regime and from features of the englacial and basal debris. The thermal regime of the basal ice in Taylor Glacier suggests mechanisms for the entrainment and transportation of debris near the glacier sole.
Assuming steady-state conditions, basal temperatures over the ablation area of Taylor Glacier were calculated from the geothermal heat in flux, the nearsurface ice temperatures, ice velocities, and the ice thickness. In over 50% of the lower ablation area the basal ice may be melting.
The englacial and basal debris is incorporated by processes operating at the glacier sole. Englacial debris is incorporated by particle regelation; basal debris is incorporated by freezing block regelation. Both processes occur close to the glacier margin, where inner warm basal ice is in contact with marginal cold ice. The debris frozen to the sole here remains relatively unmodified during transport to the margin.
Both lines of evidence indicate that Taylor Glacier is, and has been, capable of erosion and entrainment of debris by temperate ice at the glacier sole. Debris deposited along the margin i s similar to drift deposited beyond the glacier, implying that any recent climatic changes have had little effect on basal ice conditions within Taylor Glacier.
Rheology of an Ice-Floe Field
Authors: Bratchie Iain 
Published: February 2017

The aim of the paper is (1) to develop theory to describe sea ice as a collection of finite-sized floes and (2) to construct a rheology based on this description.Successful sea-ice models have considered the ice to be a two-dimensional continuum with a nonlinear plastic rheology, a two-dimensional yield curve being used to determine the internal ice stresses as functions of the strain-rate (Hibler 1979). In this paper, the shape but not the size of such a yield curve is derived from an idealized picture of floes as moving discs, randomly distributed in a plane. The expected collision rate, which determines the energy loss, is calculated in terms of the average floe size, the areal floe-number density, and the strain-rate. For the case in which the ice strength is low, the dependence of the energy loss upon the strain-rate implies a lens-shaped yield curve, the curved portions being parts of a sine wave. This compares with circular, tear drop-shaped and elliptical yield curves that have been used in sea-ice models to date (Coon 1974, Colony 1976, Hibler 1979). The applicability of the derived yield curve to cases where the ice strength is not low and significant ridging takes place, such as in a continuous ice cover is discussed.
A 1000 Year Glaciochemical Study at the South Pole
Authors: Kirchner Severine , Delmas Robert J. 
Published: February 2017

Major soluble chemical impurities have been measured along a 130 m firn core from the Amundsen–Scott Station in order to assess Southern Hemisphere environmental variability over the last millennium. Particular attention is given to the possible impact of the Little Ice Age, a well-known climatic disturbance which occurred in the Northern Hemisphere between about A.D. 1500 and 1900.
Na+, K+, NH4
+, Cl+, SO4
2− and NO3
− concentrations were carefully determined in forty-two 40 cm firn sections. Stringent precautions were taken to ensure the analytical reliability of the data set obtained. The average concentrations are (in ng g−1): 11.0 ± 2.5, 0.7 ± 0.4, 0.5 ± 0.2, 31 ± 5.6, 58 ± 11.6 and 103 ± 11.6 respectively (the scatter represents the standard deviation).
No definite trend is detected which could be linked to the Little Ice Age disturbance.
Climatic Interpretation of a Continuous Deuterium Profile Obtained from the Vostok Ice Core, Antarctica (160 000 Years) (Abstract)
Authors: Jouzel J. , Lorius C. , Petit J.R. , Genthon C. , Barkov N.I. , Korotkevitch Ye.S. , Kotlyakov V.M. 
Published: February 2017

Oceanic studies have convincingly demonstrated that there is a link between the Pleistocene ice ages and the variations in the elements of the Earth’s orbit (Imbrie and others 1984). In contrast, the climatic conditions which prevailed over continental areas have been far less well documented and then rarely on a quantitative basis.
In this context, the 2083 m ice core recovered by the Soviet Antarctic Expeditions at Vostok (East Antarctica) is of fundamental importance because it covers fully the last glacial-interglacial cycle, back to the ice age which preceded the last interglacial (∽160 ka B.P.). Potentially it allows access to many climatic and climate-related parameters as illustrated by the oxygen-18 data we have recently published (Lorius and others 1985), from 10Be measurements (Yiou and others 1985, Raisbeck and others 1987), from aerosol concentration (De Angelis and others 1987) and from CO2 measurement (Barnola and others 1988, this volume).
Our first isotopic data set was largely discontinuous over the last 100 ka (only about 7% of the core was analyzed), but continuous beyond that time. Sampling of the ice was completed later, in the field, and we now have continuous deuterium data for the whole core (total ice recovery is about 85%), combining the data of the 2083 m core below 138 m and a complementary data set above. The core chronology was established using a two-dimensional ice-flow model and, for snow accumulation, taking into account change with time (Lorius and others 1985).
There is a general correspondence between this curve and the previously published δ18O record (Lorius and others 1985). However, there is obviously far more information in this continuous δD record, which we will examine from the deduced temperature record.
Implications of the Time Required for Minimum and Tertiary Creep Rates for Ice Mining and Tunnel Closure (Abstract only)
Authors: Jacka T. H. , Budd W. F. 
Published: February 2017

For the calculation of rates of closure of tunnels or bore holes in ice, the use of a flow law relation based on secondary or minimum creep rates necessarily underestimates closure rates, particularly for large strains where much higher tertiary creep rates develop. Long-term laboratory studies have shown that the change in strain-rate from primary to secondary or minimum and to an approximately constant tertiary stage is associated with recrystallization and the development of strong crystal-orientation fabrics which are dependent on the stress configuration, but not appreciably on crystal size. For bore holes, tunnels or cavities constructed in ice, initial rates of closure decrease, in primary creep, to a minimum value (at about 1% strain) dependent on stress and temperature. From this time, increasing strain-rates occur, analogous to the results obtained from the laboratory studies.
A 25-year record of closure of a tunnel at about 30 in depth at site S2 on Law Dome, Antarctica, illustrates the application of the laboratory-derived relations. Comparison between the results of deformation from bore holes, tunnels and laboratory tests, comprising various stress configurations, under similar conditions of stress and temperature, indicates that the strain-rates are compatible when considered as a function of total strain.
Snow-Collection Mechanisms and the Capacities of Snow Fences
Authors: Takeuchi Masao 
Published: February 2017

The shapes of equilibrium lee drifts formed by snow fences are scaled in proportion to height of snow fences independent of the snow and weather conditions, even in small-scale models, but those of up-wind drifts are not.
Field studies have been made of the snow-collection mechanisms of a snow fence. It has been observed that particles of saltated snow piled up to windward, and that it was the previously suspended particles that were heaped up in the lee drift. It can be shown that the shapes of up-wind drifts vary in different snow and weather conditions because threshold shear stress and drift-snow saltation depend on the physical properties of the surface snow.
Equilibrium lee drifts are scaled in proportion to fence height, because snow and weather conditions have less effect on threshold wind speed for suspension, and the sheltering effect of a fence is scaled in proportion to the height of the fence.
The dimensions of the equilibrium drifts at snow fences were measured, and maximum snow-retention capacity and lee-drift length presented as a function of fence height, fence density, and depth of snow cover.
Changes In Glacier Length Induced By Climate Changes
Authors: Raymond C.F. , Waddington E.D. , Jøhannesson Tómas 
Published: February 2017

Time scales for adjustment in the length of a glacier to changing climate may be described in terms of a relatively short time scale, T
S and a longer memory time, T
m. The memory Tm
represents the time scale needed for asymptotic approach of the glacier to a steady state following a climate change event. Tm is determined by simple continuity considerations concerning the total volume change that must occur to reach steady state and the balance rate that drives the change. We show that T
m is relatively independent of the size of the climate change or to details of how ice flow is related to the geometry of the glacier. The time scale T
S represents the time between a climate event and the occurrence of substantial changes in the glacier length. We show that, in contrast to T
m, T
s is highly dependent on the size of the climate change and on details of ice dynamics. This dependence is investigated by several ice-flow models including a simple one in which ice transport is determined by local thickness and slope, as in the analysis of kinematic waves, and a finite element representation that fully includes longitudinal stress gradients. The ice-flow models are subjected to mass-balance perturbations of varying size — from small, for which linearization approximations are valid, to large, for which linearization breaks down.
The following behavior may be identified. Increasing the size of a mass-balance rate change causes a more rapid initial response of a glacier terminus, which tends to shorten T
s. Longitudinal stress gradients damp local variations in velocity and thereby slow the propagation and diffusion of kinematic waves and retard the response of the terminus, which tends to lengthen T
s. Longitudinal stress gradients transmit forces to the terminus region and influence the terminus motion without the necessity of redistributing mass from the glacier length into the terminus zone, which tends to shorten T
s. These various results indicate that accurate modeling of the short term responses of glaciers to climate change requires fairly sophisticated ice-flow models, However, for purposes of tracking glacier lengths (or areas) over time scales considerably great than T
s, fairly simple ice-flow models may suffice.
Annual Salt and Energy Budget Beneath an Antarctic Fast Ice Cover
Authors: Allison Ian , Tivendale C. M. , Copson G. R. 
Published: February 2017

Water temperature and salinity profiles were measured to a depth of 300 m below a fast ice cover near Mawson, Antarctica over a full annual cycle. Together with measurements of ice thickness and salinity, they are used to determine the heat and salt balance of the ice/ocean system at this site. The energy balance of the ocean is related to measured energy fluxes at the surface.Throughout the winter there is a net advection of salty water to the site which enhances the salinity increase in the water due to brine ejected from ice. After the ice reaches its maximum thickness there is considerable advection of warmer water which both raises the water temperature at the site and provides heat for the large oceanic heat flux previously reported for Mawson. The rate of this heat advection increases as the ice extent around Antarctica decreases. The ice partially meltsin situand breaks out in mid January. This effective removal of fresh water is balanced by a large influx of melt water from the continental ice sheet. The fresh water, initially near the surface, becomes well mixed to depths of greater than 200 m by strong storms in the ice free period from mid January to early April.