bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Debris-Rich Ice in Flow Near the Margins of Glaciers (Abstract)
Authors: Baker R.W. 
Published: February 2017

The margins of many ice sheets and ice caps are marked by the presence of alternating layers of debris-laden and clean ice. The role of this ice in flow and sediment transport near the margins of glaciers has been the subject of considerable controversy between glacial geologists and glaciologists for over three decades.
Glacial geologists (Goldthwait, 1951, 1960, 1971, 1975; Bishop, 1957; Souchez, 1967, Boulton, 1970, 1972; Hambrey, 1976) commonly refer to the debris-bearing ice bands as “thrust planes” or “shear planes”, apparently seeing them as reverse faults which transport rock debris from the glacier bed to the surface in a “conveyor-belt-like” manner (Goldthwait, 1975, p. 192). As supporting evidence for the shear-plane mechanism, glacial geologists have offered only qualitative observations and none seem to have actually observed it in action. Glaciologists on the other hand, particularly Weertman (1961), Hooke (1968; 1973), and Hooke and Hudleston (1978), have objected to this concept on physical grounds and have presented convincing arguments for doubting that it is mechanically sound. In spite of the controversy surrounding it, the shear-plane mechanism has gained wide acceptance among geologists and physical geographers and has been perpetuated in recent years through a number of popular introductory geology and physical geography textbooks (e.g. Embleton and King, 1975; Judson, Deffeyes, and Hargraves, 1976; Leet, Judson, and Kauffman, 1978; Press and Siever, 1982; Hamblin; 1982).
New Frontiers of Seismic Surveying in Antarctica: The Mapping of A Thin Layer at the Base of Ice Stream B (Abstract)
Authors: Blankenship Donald D. 
Published: February 2017

The recent availability of high resolution (greater than 250 Hz) seismic recording equipment in the Antarctic field environment has allowed the acoustical mapping of a previously unobserved subglacial phenomenon. This phenomenon is a thin (less than 10 m), yet continuous, layer at the base of Ice Stream B in West Antarctica. Discovery of this layer came during the 1983–84 austral summer in a seismic reflection survey that covered approximately 10 km2 near the Upstream B field camp (83°31’S, 138°05’W). Although analysis of the seismic data is at a preliminary stage, there is the possibility that this feature could be a basal “lubricating” layer; some sort of lubrication is of course necessary to explain the very large horizontal velocities of these ice streams.
During the seismic reflection survey on Ice Stream B, a new digital seismic recording system, developed by the Geophysical and Polar Research Center, was used for the first time under field conditions. Resolution of such a thin layer was possible only because of the very large bandwidth (0–600 Hz) and dynamic range (84 dB) of this device; this bandwidth is about twice that possessed by commercially available seismic recorders. In addition, a new level of portability (i.e. a weight of 40 kg and a power requirement of 90 watts), which should make this device usable in virtually any Antarctic field situation, has been achieved by the application of advanced recording technologies. The portability of this digital seismic recorder, when combined with its large bandwidth and dynamic range, should result in the resolution of a whole new class of intra- and subglacial phenomena, of which the thin basal layer of Ice Stream B is the first example.
Strain Rates On Rutford Ice Stream, Antarctica (Abstract)
Authors: Stephenson N. , Doake C.S.M. 
Published: February 2017

In a study of the Rutford Ice Stream, strain rates were measured on a transverse section. Magnitudes ranged up to 40 × 10−3 a−1 but were typically in the order of 3 × 10−3 a−1 with an error of 0.1 χ 10−3 a−1. Variations in the strain rate between adjacent stakes of 0.2 χ 10−3 a−1 to 2 × 10−3 a−1 were matched to the thickness variations on the glacier.
For each set of three adjacent stakes, the velocity gradient components of the surface strain rate tensor were calculated by assuming that the gradients were linear over the distance between adjacent stakes. When plotted against distance across the ice stream, each strain rate component revealed different aspects of the flow field. The longitudinal strain rate was compressive, with an almost constant magnitude of 10−3 a−1. The lateral strain rate is extensive, with an average value of 1.1 × 10−3 a−1 which agreed with the angle between the divergent flow lines observed on a Landsat image. Peaks in the lateral strain rate, corresponding to longitudinal bands of thicker ice, showed that these thicker bands were spreading more rapidly at the expense of thinner areas. The two velocity gradient components of the shear rate tensor also reflected differences in ice thickness.
Seasonal Variations In The Surface Energy Exchanges Over Antarctic Sea Ice and Coastal Waters
Authors: Allison I. , Tivendale C.M. , Akerman G.J. , Tann J.M. , Wills R.H. 
Published: February 2017

Seasonal variations in radiative and turbulent fluxes at the surface of, and in the heat transfer within, sea ice are discussed from results of energy balance studies at a site of annual ice cover near Mawson, Antarctica. In mid-summer, the open water gains heat mostly by radiation but by early February the ocean is cooling predominantly by strong turbulent losses, with some radiative heat loss occurring also by March. When an ice cover forms, turbulent fluxes decrease from several 100 W m−2over open water to only 40 w m−2over ice less than 0.2 m thick and even less over thicker ice.Net radiative losses over mature ice in mid-winter are balanced mostly by conduction through the ice cover but with some turbulent heat gain at the surface. By mid-spring, there is a net radiative gain, the turbulent fluxes are again outgoing, and there is little total heat transfer through the ice. At break-out, the albedo increase from ice to open water causes a large increase in the net radiative gain.At the lower boundary of the ice, the oceanic heat flux provides an important contribution. A net advection of heat into the region is shown from temperature profiles in the water under the ice. Salinity changes in the water during the period of ice melt are also discussed.
On Modeling the Weddell Sea Pack Ice
Authors: Hibler W.D. , Ackley S.F. 
Published: February 2017

Some results from a dynamic-thermodynamic simulation of the seasonal cycle of the Weddell Sea pack ice are described. The model used for the study is similar to that developed by Hibler (1979) for a numerical investigation of the Arctic ice cover. It employs a plastic ice rheology coupled to a two-level ice-thickness distribution. The thickness characteristics evolve in response to ice dynamics, and to ice growth and decay rates dictated by surface heat-budget calculations and by heat storage in a fixed depth oceanic boundary layer. Observed time-varying wind, temperature, and humidity fields based on the 1979 Australian analysis are used together with empirical radiation fields and fixed ocean currents to drive the model. Employing these fields, the model is integrated over two seasonal cycles. The second-year results are compared to observed ice-drift data obtained by Ackley (1981[b]) and to ice-edge characteristics determined from satellite imagery. In analyzing the results, particular attention is paid to ascertaining the relative roles of ice dynamics and thermodynamics in determining the ice-edge characteristics. A sensitivity analysis of the effect of a different parameterization of the atmospheric temperature and humidity fields is also carried out.Overall, the results suggest that (1) ice dynamics are essential in describing the seasonal cycle, and (2) a feedback between the atmospheric temperature and the presence of ice may be a major cause of the rapid decay of the Antarctic ice cover during the spring-summer period.
Landsat Images and Mosaics of Antarctica for Mapping and Glaciological Studies
Authors: Williams Richard S. , Ferrigno Jane G. , Kent Tina M. , Schoonmaker James W. 
Published: February 2017

The preparation of a US Geological Survey Professional Paper, “Satellite image atlas of glaciers”, has produced a 1:5 000 000 scale “Landsat index map of Antarctica”, in which each of the 2 470 Landsat nominal scene centers is represented by a symbol showing the suitability of available Landsat images for the preparation of planimetric image maps and for glaciological studies. Landsat has the potential for imaging about 79% of the area of Antarctica, and 70% of the Landsat imaging area, or about 55% of the continent, was found to have excellent or good (less than 10% cloud cover) coverage.Australia, Japan, New Zealand, the United Kingdom, and the United States of America have published Landsat image maps, either as single Landsat scenes or as mosaics of two or more images. The Federal Republic of Germany and the Republic of South Africa also plan to publish Landsat image maps in the near future.Available Landsat images could be used, in combination with Doppler satellite technology for geodetic control, to triple the area of Antarctica presently mapped at scales of 1:250 000 or larger. Landsat-3 RBV images can also be used to prepare 1:100 000 scale image maps.In addition to eventually using Landsat images to compile an accurate coastline of Antarctica, Landsat images have been successfully used for glaciological studies. Recent measurements of successive images of Pine Island Glacier, Walgreen Coast, West Antarctica, showed an average speed of flow of the terminus of 6 m d−1over 750 d.
Radar Studies of Internal Layers and Bottom Topography at Dome C, East Antarctica (Abstract only)
Authors: Jezek Kenneth C. , Shabtaie Sion , Bentley Charles R. 
Published: February 2017

Extensive and detailed radar surveys at Dome C were conducted during the 1978–79 and 1979–80 austral field seasons by groups from the University of Wisconsin. Measurements were conducted within a 10 × 10 km grid centered approximately on the Dome C camp (some additional studies were carried out as far as 20 km from the camp) and involved profiling of internal layers and bottom topography. In addition, a new digital recording system for the radar was used during the first season and has yielded interesting results on internal layers near the French bore hole.
Analysis of these data has produced a local map of bottom topography showing generally rough terrain. In particular, there is a rapid deepening of the bottom topography (about 500 m over 2 km) just grid south-west of the camp. Internal layers were found to be discontinuous on a scale of tens of meters. The deepest internal layers were detected at depths of about 2 500 m although a set of remarkable layer-like returns were observed about 50 to 100 m above the interpreted base of the ice. (It is not yet clear whether these returns represent reflections from layers internal to the ice or whether they are reflections and diffractions associated with the rough terrain.) In addition the processed digital records show an abrupt decrease in the reflection strength of internal layers at about 1 700 m. Because the digitally recorded data were collected at only one site, we reserve concluding that this observation is characteristic of the entire Dome C area until more of the photographically recorded data can be reduced.
The East Antarctic Ice Sheet: The Problem of Palaeoglaciological Reconstruction (Abstract only)
Authors: Bardin V.I. 
Published: February 2017

Palaeoglaciological studies, including glaciogeomorphological observations and comprehensive studies of the composition of glacial deposits, undertaken by scientists of a number of countries, enable the major stages in the evolution of glaciation of some regions of East Antarctica to be outlined.
In this report, palaeoglaciological reconstructions for certain key territories: Queen Maud Land, Mac. Robertson Land, and Victoria Land are considered. The completeness and reliability of such reconstructions are also discussed.
The region of Prince Charles Mountains (Mac. Robertson Land) turned out to be one of the most significant for palaeoglaciology. In this region, the author has discovered and studied glacial deposits of at least six age stages, their formation having taken place during approximately 20 Ma.
An attempt is made to compare the results of regional studies and to present the evolution of the development of the whole East Antarctic ice sheet in space and time.
Different examples of palaeoglaciological reconstructions of the ice sheet of East Antarctica are presented, the possibilities of different approaches are evaluated practically, and schematic maps of the change in glaciation of East Antarctic regions at different evolutional stages, compiled by the author, are presented for discussion.
Glacier Fluctuations in George VI Sound Area, West Antarctica (Abstract only)
Authors: Clapperton C.M. , Sugden D.E. 
Published: February 2017

George VI Sound lies between Alexander Island and the Antarctic Peninsula and is over 20 km wide and 500 km long. At present an ice shelf fills the sound and is nourished largely by ice from the Antarctic Peninsula which flows across the sound to ground against the coast of Alexander Island. Ice-free areas, comprising small nunataks and larger massifs, fringe both sides of the sound and contain evidence of the former glacial history of the area. This paper describes the field evidence in detail and uses geomorphological and sedimentary analyses to put forward a relative glacial chronology, constrained by two absolute dates.
The chronology distinguishes:

(1) a maximum state during which all ice-free areas were submerged by ice flowing into George VI Sound from both the Antarctic Peninsula and Alexander Island and thence along the sound as an ice stream. This occurred in the late Wisconsin and followed an interstadial or interglacial when George VI Sound was free of an ice shelf.

(2) a valley-based stadial during overall deglaciation represented by pronounced marginal moraines on Alexander Island.

(3) deglaciation to a stage where there was less landbased ice on Alexander Island than today. At this stage isostatic recovery was incomplete, relative sealevel was higher, and George VI Ice Shelf penetrated further into embayments on Alexander Island than at present.

(4) probable disappearance of George VI Ice Shelf by 6.5 14C ka BP.

(5) neoglacial readvance of local glaciers on Alexander Island to form three closely spaced terminal moraines and the growth of a new George VI Ice Shelf which was again more extensive than at present.

(6) subsequent oscillations of both smaller Alexander Island glaciers and George VI Ice Shelf probably during the Little Ice Age. These fluctuations are similar to those in other sub-Antarctic Islands in the Scotia Sea and also in southern Chile.
Control Exerted by Sea-Ice Extent Over Oxygen Isotope Ratios In Coastal Antarctic Precipitation (Abstract only)
Authors: Weaver Clark , Bromwich David H. 
Published: February 2017

The observations of the stable oxygen isotope composition δ of precipitation at the coastal Syowa station for 1974, which are reported and analyzed by Kato (1977, 1978), are reassessed on a monthly time scale. The relationship between oxygen isotope ratio and temperature is examined in detail. The mean temperature of the preceding month, rather than the temperature at the time of sample collection, has the best association with monthly averaged δ. This one-month lagged relationship suggests the strong influence of sea ice which is related to the average temperature in the same fashion. Linear regression analyses, using monthly variations of Antarctic seaice extent for 1974, as reported by Zwally and others (1979), reveal the following interrelationships which provide good support for the contention that sea-ice extent is a dominant factor for δ values in coastal Antarctic precipitation:

For August 1974 the δ values are persistently less than those predicted by sea-ice area. Over the Southern Ocean, the zonal circulation in August was weak in comparison to the 1972–79 average. It is hypothesized that this anomalous circulation resulted in the source region of moisture precipitated at Syowa being located substantially farther north.
This paper will be published in full elsewhere.
Photogrammetric Investigation of Byrd Glacier Surface Lowering (Abstract only)
Authors: Brecher Henry H. 
Published: February 2017

While carrying out photogrammetric measurements to provide surface velocities and elevations for use in studies of the equilibrium and dynamics of Byrd Glacier, I noted that comparison of elevations obtained by ground surveys in 1978-79 with US Geological Survey topographic maps made from 1960-62 aerial photography indicated a very large apparent lowering of the glacier surface in this short timeinterval. The apparent lowering varied between 50 and 150 m along a 60 km section of the glacier for which data were available (Brecher 1980).
The ground measurements were estimated to be in error by no more than 3 in but the accuracy of elevations on the maps was unknown. Because these are reconnaissance maps, however, substantial errors would not be unexpected. It was therefore necessary to obtain more accurate glacier surface elevations for 1960–62 in order to determine whether the lowering is real. Photogrammetric strip triangulations of three individual strips of photography, two taken in November 1960 and the third in February 1963, which cover the region of the greatest apparent lowering, have now been completed. The old strips were oriented to fixed points on the two “banks” of the glacier derived for this purpose from the 1978–79 photogrammetric work, thus bringing the measurements from the old and new photography into a common coordinate system.
The glacier surface elevations for 1960–62 are the same as those obtained from the 1978–79 ground survey and photogrammetry. While it is difficult to give measures of accuracy of the results since no independent data are available for comparison, internal evidence indicates that precision higher than the expected 10 m has been achieved in the measurements. It can thus be stated unambiguously that no detectable surface lowering has occurred on any of the parts of the glacier which have been investigated.
An Atmospherically Driven Sea-Ice Drift Model for the Bering Sea
Authors: Pease C. H. , Overland J. E. 
Published: February 2017

A free-drift sea-ice model for advection is described which includes an interactive wind-driven ocean for closure. A reduced system of equations is solved economically by a simple iteration on the water stress. The performance of the model is examined through a sensitivity study considering ice thickness, Ekman-layer scaling, wind speed, and drag coefficients. A case study is also presented where the model is driven by measured winds and the resulting drift rate compared to measured ice-drift rate for a three-day period during March 1981 at about 80 km inside the boundary of the open pack ice in the Bering Sea.
The advective model is shown to be sensitive to certain assumptions. Increasing the scaling parameter A for the Ekman depth in the ocean model from 0.3 to 0.4 causes a 10 to 15% reduction in ice speed but only a slight decrease in rotation angle (α) with respect to the wind. Modeled α is strongly a function of ice thickness, while speed is not very sensitive to thickness. Ice speed is sensitive to assumptions about drag coefficients for the upper (CA) and lower (CW) surfaces of the ice. Specifying CA and the ratio of CA to CW are important to the calculations.
Atmospheric CO2 Concentration During the Last Glaciation
Authors: Stauffer B. , Hofer H. , Oeschger H. , Schwander J. , Siegenthaler U. 
Published: February 2017

Analyses of atmospheric air extracted from air bubbles in polar glacier ice provide a measure of past CO2concentrations and their temporal variations. Earlier measurements have shown that the atmospheric CO2concentration was significantly lower during the late Wisconsin stage and that the change from low to high CO2concentration occurred in a relatively short time period.We measured the CO2concentration of ice samples from the deep ice core recently drilled at Dye 3 (south Greenland). The core section investigated represents ice from about 40 to 30 ka BP. The air extracted from the ice samples shows large variations of CO2concentration which are correlated with δ18O values of the ice samples. A probable explanation of the results is that corresponding changes of the atmospheric CO2concentration occurred during that glacial period. These changes could have had a significant influence on the climate. Possible reasons for the variations of the atmospheric CO2concentration are discussed.
Glaciological Investigations in the Crête Area, Central Greenland: A Search for a new Deep-Drilling Site
Authors: Clausen H.B. , Gundestrup N.S. , Johnsen S.J. , Bindschadler R. , Zwally J. 
Published: February 2017

The results of the 1984-85 post-GISP campaigns in central Greenland are presented. Eight ice cores were obtained, some spanning up to 360 years. We present:

I.
Geographical positions and elevations at the drill sites,

II.
Density and temperature in the bore holes,

III.
Filtered δ18O profiles and accumulation-rate variations along the ice cores.

The δ18O and accumulation profiles, along with those from the 400 m Crête ice core obtained in 1974, are compared.
The accumulation-rate series over a large region have a very high coherence. This indicates that a single bore hole in this region would give a representative accumulation time series over a long period. Further, it appears that for this region there is a linear relation between the measured annual accumulation rate and the mean annual δ18O values. Thus the area between Crête and Summit, just west of the ice divide, seems to be favorable for a deep-drilling operation.
Trace Elements in Simultaneously Sampled Aerosol and Snow from the Antarctic Peninsula (Abstract)
Authors: Dick Alan L. 
Published: February 2017

Ultra-clean techniques have been used to collect a series of fresh surface-snow samples on Gipps Ice Rise, Larsen Ice Shelf (68°48′S, 60°54′W) between 21 December 1984 and 12 February 1985. Aerosol samples were collected simultaneously on to pre-cleaned membrane filters to allow the direct comparison of trace-element levels in air and snow. Samples have been analysed by various techniques for cadmium, copper, lead, zinc, aluminium, calcium, potassium and sodium. For all elements, cross-sample concentration profiles have been obtained to support the data for snow samples.
The heavy-metal concentrations found in the surface snow were similar to those measured previously near Gomez Nunatak in the Antarctic Peninsula. The mean aerosol concentrations found at Gipps Ice Rise were Cd: 0.06 pg m−3, Cu: 1.0 pg m−3, Pb; 4.7 pg m−3, Zn: 6.1 pg m−3. These are the lowest concentrations measured so far in Antarctic aerosol.
The ratio of the snow concentration (pg g−1) to air concentration (ng m−3), known as the washout factor, has been calculated for each element and sampling period. The data show that, for the Antarctic Peninsula, the marine aerosol is more efficiently removed to the snow-pack than is the crustal aerosol. Heavy metals are least efficiently removed. This result suggests that the measurement of concentrations in snow and ice alone may lead to misinterpretation of atmospheric source strengths.