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).

The spatial and temporal variability of surface, cloud and radiative properties of sea ice are examined using new satellite-derived products. Downwelling short- and longwave fluxes exhibit temporal correlation over about 180 days, but cloud optical depth and cloud fraction show almost no correlation over time. The spatial variance of surface properties is shown to increase much less rapidly than that of cloud properties. The effect of small-scale inhomogeneity in surface and cloud properties on the calculation of radiative fluxes at ice- and climate-model gridscales is also investigated. Annual mean differences between gridcell fluxes computed from average surface and cloud properties and averages of pixel-by-pixel fluxes are 9.46% for the downwelling shortwave flux and −7.04% for the longwave flux. Therefore, using mean surface and cloud properties to compute surface radiative fluxes in a gridcell results in an overestimate of the shortwave flux and an underestimate of the longwave flux. Model sensitivity studies show that such biases may result in substantial errors in modeled ice thickness. Clearly, the sub-gridscale inhomogeneity of surface and atmospheric properties must be considered when estimating aggregate-area fluxes in sea-ice and climate models.

The inventory of Glacier National Park, B.C., has provided an opportunity to test a number of new procedures which might be applied to future Canadian glacier inventories. The objectives of this particular study were to complete a tripartite inventory based on available map and photo sources and develop an automated system of data acquisition and processing. The conjunction of the two has permitted an analysis of the evolution of the glaciers in this area during the last 100 years. The techniques used and a summary of the results are reported.

The relationship between ice fabric and the internal radio-echo reflections was investigated using observation data collected at Mizuho Station, Antarctica. The data were obtained by 179 MHz radio-echo sounding and the ice fabric was measured from 700 m Mizuho ice core. The dielectric permittivity tensor at given depths in the ice sheet was calculated from the ice fabric.

The calculated dielectric permittivity tensor showed that the ice sheet at Mizuho Station is a uniaxially birefringent medium. The symmetrical axis of rotation was the same as the flow line. In such a medium, theory predicts that the electric field vectors are allowed only in the two directions parallel and perpendicular to the flow line. The prediction coincided well with the observation: a strong signal was observed only when the transmitting antenna and the receiving antenna, kept parallel to one another, were oriented parallel or perpendicular to the flow line. However, the observed signal strength in these two directions differed from one another at each depth.

It is also shown that the power reflection coefficient due to the variation of ice fabric with depth is of approximately the same order as that due to the density change and is large enough to produce the predominant internal radio-echo reflections.

Relationships between stable isotopes (δD–δ18O), ice facies and glacier structures have hitherto gone untested in the mid-latitude maritime glaciers of the Southern Hemisphere. Here, we present δD–δ18O values as part of a broader study of the structural glaciology of Fox Glacier, New Zealand. We analyzed 94 samples of δD–δ18O from a range of ice facies to investigate whether isotopes have potential for structural glaciological studies of a rapidly deforming glacier. The δD–δ18O measurements were aided by structural mapping and imagery from terminus time-lapse cameras. The current retreat phase was preceded by an advance of 1 km between 1984 and 2009, with the isotopic sampling and analysis undertaken at the end of that advance (2010/11). Stable isotopes from debris-bearing shear planes near the terminus, interpreted as thrust faults, are isotopically enriched compared with the surrounding ice. When plotted on co-isotopic diagrams (δD–δ18O), ice sampled from the shear planes appears to show a subtle, but distinctive isotopic signal compared with the surrounding clean ice on the lower glacier. Hence, stable isotopes (δD–δ18O) have potential within the structural glaciology field, but larger sample numbers than reported here may be required to establish isotopic contrasts between a broad range of ice facies and glacier structures.

The salinity and isotope (18O, 3H) content of multi-year landfast sea-ice (MLSI) cores from northern Ellesmere Island, Canada, are examined. Salinity ranges from 0.01‰ to 4.54‰, and δ18O ranges from −23.8‰ to +0.7‰. Salinity and δ18O are linearly related, and tritium values generally exceed natural background levels. The results are evidence of ice growth associated with fresh-water / sea-water stratification below the ice. Salinity variations are cyclic and indicate a mean annual bottom accretion rate of 0.33–0.5 m a−1. Rather than signifying downward percolation of melt water from the surface, the ice δ values are a proxy measure of variations in salinity and 18O content of the water below the ice. Annual salinity layers are preserved in the absence of significant brine movement and ice deformation. The fast-ice environment appears to favour the maintenance of water stratification and growth of annual layers. It is suggested that ice growth in this environment is somewhat independent of thermodynamic sea-ice growth models; instead, ice growth by a double-diffusion process might account for the growth of MLSI beyond thicknesses normally encountered in undeformed multi-year pack-ice floes.

During the operational lifetime of the Seasat altimeter from 3 July to 10 October 1978, more than 450 overflights were made over East Antarctica inland to latitude 72°S. An analysis of selected passes over a variety of ice features demonstrates that the oceanographic altimeter performed surprisingly well over the ice sheet and ice shelves, acquiring useful measurements during approximately 70% of each pass. The altimeter's onboard tracking system dampened out the ice-surface elevations, but post-flight retracking of the stored return waveforms reveals excellent ice-surface details. After waveform retracking, the altimeter repeatability is better than ±1 m.

Velocity measurements were made for two time intervals on the Smith Glacier ice tongue (1973–88 and 1988–90) and three on the Dotson Ice Shelf (1972–88, 1973–88 and 1988–90). The Smith Glacier ice tongue velocities for the two intervals are similar near the grounding line but show a progressive increase toward the terminus in the late 1980s. The Dotson Ice Shelf velocities remained virtually constant during all three time intervals. The increased velocities of the Smith Glacier ice tongue may be attributed to a general loss of densely packed icebergs that buttressed the terminus during the 1970s but drifted out to sea during the late 1980s. The Smith Glacier ice tongue receded as much as 10 km between 1973 and 1988, the Dotson lee Shelf 5–7 km in the same time period. Similar observations of drifting and ca1ving were made for the adjacent Thwaites Glacier ice tongue. The cause of the loss of ice in the region is unknown but it may have been a change in winds or a warming of the air or water during the late 1980s.

A three-dimensional, numerical simulation model for snow transport and drift formation is proposed in which saltation as well as suspension are considered as dynamic behavioral factors of moving snow particles. The procedure for simulation is as follows: (1) Air flow field is simulated solving the Reynolds equations and the continuity equation. (2) Using the result of the air field flow simulation, the blown-snow density field is simulated using the diffusion equations in which the fall velocity of blown snow particles is considered. In the boundary conditions, the particle movement of saltation is taken into consideration. (3) Finally, the snowdrift rate is computed based on the amount of snow particles not transported by saltation. This model was quantitatively tested for the phenomenon of snowdrift development. The computed results showed good agreement with observations.

There are relatively few comparisons between synthetic aperture radar (SAR) observations and glacier mass-balance measurements. More typically, SAR has been deployed to identify changes in the end-of-summer snowline and other facies boundaries. In this paper, we analyze the geophysical processes affecting SAR amplitude data over two Arctic glacier systems in northern Scandinavia to assess the potential of SAR observations for the retrieval of surface balance parameters. Using a backscatter model and in situ data, we identify the controls on SAR imagery in terms of mass-balance measurement and discuss the glaciological parameters which can reasonably be derived from multi-temporal SAR data. Our results show that amplitude SAR imagery, in the absence of in situ measurements, is not capable of providing meaningful mass-balance data. We show that backscatter from temperate glaciers is affected primarily by snow grain-size and density, and therefore processes such as firnification or depth-hoar formation can complicate the analysis of imagery. We conclude that SAR imagery over temperate glaciers can provide valuable proxy information but not direct mass-balance terms.

The shift of the equilibrium line in response to climatic disturbances is calculated for the International Glaciological Greenland Expedition (EGIG) profile of the Greenland Ice Cap. Data of heat balance studies carried out during EGIG 1959 and EGIG 1967 are used according to Kuhn’s algorithm. The following parameters are applied; the heat transfer coefficient of the sensible heat flux; the effective emissivity of the atmosphere for long wave downward radiation; a factor relating net radiation to cloudiness; the duration of the ablation season; the altitudinal temperature gradient; the altitudinal accumulation gradient.

The altitudinal shift of the equilibrium line results for the EGIG profile + 77m/°C and -4 m per 1/10 cloudiness with 35d of ablation. Changes in heat balance by formation of superimposed ice are taken into account.

The Glacial Geomorphological Map (1:200 000) of Mt, Tomur Region, Tianshan, covers 78°33′ – 81°10′E and 41° 08′ – 42° 44′N, with high mountains, deep valleys and many snow peaks, the highest being Mt. Tomur (7435.3 a.s.l.). There are many glaciers in this region with a total area of 4553.69 km2. The melt water from glaciers irrigates the large oasis of Aksu, in the piedmont region in southern Xingjiang and waters the valley plain of Teks River in the Yili area. From piedmont plain to highest mountain summit, the vertical zonality of geomorphology is quite clear, rich in various geomorphological types, representing alpine geomorphology of the arid desert in Central Asia.

The author joined the glacial/geomorphological expedition to the Mt. Tomur Region in 1963, 1973 and 1974, and, in the process of mapping, cooperated closely with mapping engineers. This involved extensive use of aerial photographs, satellite images, large-scale topographic maps, geological maps, geomorphological maps and other data, and comprehensive analyses, comparisons, and judgements of data.

Special emphasis was placed on existing glaciers and the geomorphology of Quaternary glaciers, according to form, composition and relative chronological periods. The geomorphology was divided into five great systems, i.e. glacial, fluvio-glacial, fluvial, arid and artificial. Twenty-four geomorphic types were defined as the basic elements of the geomorphological map and shown in different colours and by various marks, while old and Neozoic faults were shown by black line marks. There are representative heights on all geomorphological zones. Colour brush-shading added much to the stereo effect.

Below the main map, the longitudinal and cross sections of Quaternary geology and geomorphology of the Tialan valley, the stratigraphical columnar profile of West Zamtia and the fluvial/lacustrine deposit profile of the Loska basin were attached, showing the stratigraphical relation between the glacial and non-glacial deposit and the basis for the divisions of the glacial and inter-glacial periods.

Results of measurements performed on and around an Antarctic blue-ice field are presented in this paper. The measurements were carried out in a valley of Heimefrontfjella, Dronning Maud Land, during a 2 month field season in the austral summer of 1992–93. A simple model is used to evaluate the surface-energy balance from measured meteorological quantities. The large differences in the surface-energy-balance values between snow and blue ice are mainly caused by differences inalbedo, surface roughness, thermal conductivity and short-wave radiation extinction coefficient. Taking into account uncertainties in the calculations, it appears that the calculated sublimation rates over ice and snow do not differ much.

Furthermore, typical circulation patterns are described. The large continental-scale katabatic flow is forced by radiative cooling of the surface (night-time) and the mesoscale horizontal temperature gradient (daytime). The latter penetrates to the surface due to enhanced mixing in an unstable stratified boundary layer. At night, shallow katabatic layers form along local fall lines. On some occasions the large-scale katabatic winds decrease through the presence of a high-pressure system in the weddell Sea and a local circulation can develop inside the valley.

Bolshoi Lyakhov is one of the group of the New Siberian Islands in the Laptev Sea. The permafrost of the island is of an extremely low temperature regime, polygonal wedge ice being the most specific feature. The geomorphological level considered is a so-called edoma, presumably of late-Quaternary origin: polygonal ice wedges are more than 10 m wide and up to 25 m deep on this level, and about 1 m × 1.5 m on the peat bogs of Holocene age. Sixty-six samples of underground ice were taken on both surfaces. The macro-ion content was analyzed, i.e. Ca, Mg, Na, K, HCO3, Cl, SO4. A significant difference in ion content was found between the older and the younger ice. The late-Quaternary wedge ice is characterized by the predominance of Ca and HCO3, while the Holocene ice contains considerably higher proportions of Na and Cl. This may be attributed to different environmental conditions during wedge-ice growth: more continental in the late Quaternary and more maritime in the Holocene.

A method for calculating the impulse response of a layered dielectric is used to investigate the effect of near-surface density stratification on the interpretation of radar-altimetry data collected over ice sheets. Results are computed for a model consisting of a measured density profile that is artificially interrupted by an ice layer inserted at successively greater depths. The incident radar signal is modeled by a 20 ns long pulse modulated at 1 GHz. Analysis using a simple scheme for estimating the one-way travel time of the wave indicates as much as a 2 ns (equivalent to 60 cm in range) apparent time delay for a density profile that has been modified by inclusion of an ice layer relative to the ice-layer-free case. This suggests that layering may be a factor in interpreting repeated altimeter measurements of the ice sheets in terms of net growth or decay.

Significant salinity anomalies have been observed in the Arctic Ocean surface layer during the last decade. Our study is based on an extensive gridded dataset of winter salinity in the upper 50 m layer of the Arctic Ocean for the periods 1950–1993 and 2007–2012, obtained from ~20 000 profiles. We investigate the interannual variability of the salinity fields, identify predominant patterns of anomalous behavior and leading modes of variability, and develop a statistical model for the prediction of surface-layer salinity. The statistical model is based on linear regression equations linking the principal components of surface-layer salinity obtained through empirical orthogonal function decomposition with environmental factors, such as atmospheric circulation, river runoff, ice processes and water exchange with neighboring oceans. Using this model, we obtain prognostic fields of the surface-layer salinity for the winter period 2013–2014. The prognostic fields generated by the model show tendencies of surface-layer salinification, which were also observed in previous years. Although the used data are proprietary and have gaps, they provide the most spatiotemporally detailed observational resource for studying multidecadal variations in basin-wide Arctic salinity. Thus, there is community value in the identification, dissemination and modeling of the principal modes of variability in this salinity record.

To identify the regional characteristics of mountain snowpacks related to avalanches in the central mountains of Japan, snow-pit observations were carried out over a period of between two and five winters at six study sites in three major mountain ranges: the north, central and south alps. The relationship between snowpack characteristics and meteorological properties was then examined to suggest indicators that could determine the snowpack characteristics in the region using meteorological data. On the basis of the dominant type of persistent weakness found within snowpacks, the study sites were divided into three regions: (1) the mountains on the Sea of Japan side - the persistent weakness was caused mainly by the presence of melt-freeze crust (MFcr) layers; (2) the inland mountains - the persistent weakness was caused mainly by the presence of weak layers consisting of near-surface faceted crystals (FCsf); and (3) the mountains on the Pacific Ocean side - the persistent weakness was caused mainly by the formation of thick weak layers consisting of depth hoar (DH) near the ground. The results also suggest that certain meteorological elements are useful indicators of the tendency of a persistent weakness to form within the snowpack: (1) DH layers: TG (°C m−1) = |average air temperature |/average snow depth (notable weakness in DH layers is found in areas where the TG exceeds 10°C m−1, but in such areas rainfall prevents the development of DH layers); (2) FCsf layers: FCsf index (CC m) = average diurnal range of air temperature × snow depth (notable weakness in FCsf layers is found in areas where the FCsf index is ∼10°C m); (3) MFcr layers: MFcr index (day m) = number of days that exceed 0°C × snow depth (notable weakness in MFcr layers is found in areas where the MFcr index exceeds 40 day m).

A survey of ice-front changes since 1910–13 shows that the Koettlitz Ice Tongue, located along the western shore of McMurdo Sound, Antarctica, has undergone significant retreat during the past 80 years. The ice front in 1910–13 was located 5 km in front of the Dailey Islands. Today, only two of the six Dailey Islands remain connected to the Koettlitz Ice Tongue. The most recent break-out of ice is believed to have occurred in 1979 or 1980, resulting in an estimated loss of 80 km2 of ice. Based on the current position of the ice front, it is estimated that a minimum of 300 km of ice has called off the Koettlitz Ice Tongue during the 80 year period that has elapsed since the ice front was first mapped in 1910–13.

The efforts to develop damage models for ice cannot be disconnected from a better knowledge of the undamaged ice behaviour. In this respect the transient behaviour of polycrystalline ice still needs to be investigated. The present paper is a contribution to the development of rheological models which can be used in varying load situations. The deformation processes which should be the foundation of the models are described. The models of Le Gac and Duval (1980) and of Sunder and Wu (1989a) are tested against two uniaxial compression tests on isotropic granular ice under varying load. They fail to describe both primary creep and the response to increments/decrements of the applied load. A new model, based on a decomposition of the viscoplastic strain into two components which account separately for kinematic and isotropic hardening, is shown to give better results.

Stauffer and others (1984) observed in the Greenland ice core from Dye 3 CO2 variations between low values in the range of 180-200 ppm volume and higher values in the range of 240-260 ppm volume, over a period tentatively dated to 30 000-40 000 years B.P. The low values are observed in samples with low δ18O, high particle and chemical impurity contents, representing precipitation from periods of cold climate; the higher CO2 concentrations are measured in samples which reflect warm climatic conditions because of their high δ18O and low impurity contents. The change from one climatic state to the other seems to occur within less than a century. This unexpected observation has received considerable attention from the scientific community. First, the question was posed whether the rapid CO2 variations do indeed reflect atmospheric CO2-concentration changes or whether they are caused by the interaction of gases with chemical constituents in the ice matrix. Secondly, carbon-cycle modellers searched for a mechanism in the carbon system which could produce such rapid changes in atmospheric CO2. Here we try to answer the first question.

Arguments in favour of an atmospheric origin of the CO2 variations are: CO2 measurements on an ice core from Siple Station, Antarctica, show a monotonous increase over the past 250 years, from values around 280 ppm volume to values overlapping closely with the direct atmospheric data which have been obtained since 1958 (Neftel and others 1985). Thus a consistent picture of the anthropogenic CO2 increase has been obtained which is compatible with estimates of the man-made CO2 emissions and with the carbon-cycle calculations of the airborne fraction of these emissions.

In addition, convincing CO2-concentration data have been obtained, from two ice cores from Greenland and four ice cores from Antarctica, for the transition from low (180-200 ppm volume) late-Wisconsin values to the higher (260-300 ppm volume) Holocene values. In spite of considerable differences in temperature, fabrics and chemical properties, the Wisconsin CO2-concentration values for ice cores from different locations lie in a narrow band. The Holocene values show a greater scatter; in particular, the values obtained for the Dye 3 core are significantly higher than those for the other cores. This can be explained by a relatively high temperature, which leads to melting in summer. In refrozen melt layers, CO2 is enriched in comparison with the other air gases. On the basis of these observations we conclude that melt layers are the main factor which can lead to considerable deviations in the CO2 concentration of the air occluded in ice cores from that of the atmosphere at ice formation.

To test if the melt-layer effect was the cause of the rapid changes in CO2 concentration which were observed in the Dye 3 core, increments of the Camp Century core from north Greenland were measured for CO2; they show similarly rapid Wisconsin δ18O and CO2 changes, though they are less abrupt than in the Dye 3 core. At Camp Century the present mean annual temperature is 4.5 °C lower than at Dye 3, and during the Wisconsin the temperature difference was even greater, as indicated by the δ18O values. Because even for Holocene ice in the Camp Century core the melt-layer effect on the CO2 concentration is relatively small, we exclude any similar significant effect on the Wisconsin ice. On the basis of the Greenland ice-core information alone, therefore, we have no indication that the rapid Wisconsin CO2 variations do not represent an atmospheric phenomenon.

Arguments against an atmospheric origin for the rapid CO2 variations stem from detailed analyses of the ice core from Byrd Station, Antarctica. Observation of the increase in anthropogenic atmospheric CO2 in both hemispheres indicates that within a few years CO2 becomes well mixed throughout the atmosphere. Thus the CO2 variations observed in the Greenland core should also appear in the Antarctic core increments which represent corresponding periods. A thorough CO2 study was performed on a Byrd Station core fraction which, according to a tentative time-scale (personal communication from C.U. Hammer, 1987), corresponds to the time interval 5000-55 000 years B.P. (Fig. 1). In what follows, we briefly discuss the data in the 25 000–55 000 years B.P. time interval. A first look reveals that all the data lie in a band between 180 and 220 ppm volume; no values are observed in the 240 and 260 ppm volume band. There are periods showing trends, e.g. from c. 210 ppm volume around 40 000 years B.P. to c. 185 ppm volume around 32 000 years B.P., and periods of strong scattering of the data, e.g. between 41 000 and 44 000 years B.P., with values in the 185-215 ppm volume band. At Byrd Station the annual accumulation is 0.16 m of water equivalent, compared to 0.50 m of water equivalent at Dye 3. This means that at Byrd Station, both the difference between the age of the surrounding ice and the mean age of the air, and the width of the age distribution of the gases, are larger than at Dye 3. In addition, the Byrd Station core does not show the rapid δ18O changes which indicate warm periods with relatively high accumulation. Thus one might argue that in the Byrd Station core the CO2 changes are dampened, due to a significantly wider age distribution of the gases in the ice.

This effect was modelled by Neftel and others (in press). They applied a deconvolution procedure in order to reinstall the range of possible atmospheric CO2 concentrations (see Fig. 2). This procedure results in a somewhat wider band of possible CO2 concentrations; in some periods it is 170-230 ppm volume. But it does not produce the possible high values in the range observed in the Greenland ice cores. All this new information leads to the following ambiguous conclusions:

The new CO2 data for the Camp Century ice core show rapid Wisconsin CO2 changes similar to those in the Dye 3 data, in spite of the differences in the temperatures and the physical and chemical properties of the two ice cores. However, similar CO2 changes do not appear in the Byrd Station ice core (from Antarctica) in the core fraction thought to represent the corresponding time interval.

There are three possible ways to resolve the apparent discrepancy:

(1) In the Wisconsin warm-period ice, CO2 is artificially enriched, due to a process which has not yet been identified.

(2) In the Byrd Station core, the CO2 changes during the Wisconsin are attenuated to a much higher degree than was assumed in the model calculations by Neftel and others (in press).

(3) The increments in both the Greenland and Byrd Station cores which have been investigated do not represent overlapping time intervals, perhaps due to rheological irregularities in the Greenland ice sheet close to bedrock (Staffelbach and others 1988, this volume).

With the existing core material it is difficult to resolve this important problem. The dilemma of the rapid Wisconsin CO2, variations is one of the many important arguments for the recovery of new deep cores both in Greenland and in Antarctica.