The purpose of this Study is to propose a new constitutive law for pack ice, which is not only capable of Simulating the in-plane Shear and out-of-plane uniaxial compression, but also capable of avoiding overestimating divergence during Shear. The pack ice is treated as a two-dimensional granular plastic, obeying Coulomb’s friction law with a maximum principal Stress limit. During the out-of-plane uniaxial compression process the flow rule is normal, while during the in-plane Shear process the flow rule is coaxial with a linearly varying dilatancy angle describing the divergence. The Strength parameterizations are based on thickness and compactness of the pack ice; weakening or hardening can be achieved through advection and redistribution.

Trends in climate affecting the West Antarctic ice sheet may be detected first in the Antarctic Peninsula region. Although the area contains the most comprehensive weather records for any part of Antarctica, reliable snow-accumulation data are lacking.

Mainly as a result of the large snow-accumulation rate in the region (typically in the range 4.0–10.0 kg m−2 a−1), stratigraphie evidence of climate derived from ice cores can be resolved in much greater detail than is possible over most of the continent. Ice cores have been drilled at two sites, representing the extremes of climate type encountered in the region. A 133 m core has been obtained from Dolleman Island (70°35.2′S, 60°55.5′W) to represent the continental-type climate of the Weddell coast region, and an 87 m core has been obtained from the Palmer Land plateau (74°01′S, 70°38′W) to represent the more maritime regime of the west coast and central areas. Replicated cores were obtained at both sites in order to assess the contribution of local noise factors to the climatic signal preserved in the cores. Climatic trends during the period 1938–86 have been assessed on the basis of stable-isotope analysis of the top 47 m of the Palmer Land core and of the top 32 m of the Dolleman Island core.

A statistical analysis of derived profiles of mean annual δ18O and accumulation rate indicates that the local noise factors at these sites are sufficiently small that data averaged over periods as short as 5 years should reveal climatic shifts at the level of 0.2% and 5% respectively. These changes are much smaller than trends that have actually occurred during the past 50 years.

The most notable trend over the past 30 years is an increase of more than 30% in the snow-accumulation rate that has occurred in parallel with an overall temperature increase of 0.06°C/a during the same period. Increases of similar magnitude can be inferred from studies in East Antarctica, and may be related to a significant increase in precipitation rate that has been documented recently at mid-to high-latitude stations in the Northern Hemisphere. The finding may have relevance to studies of the possible consequences of a CO2-induced climate change. More extensive accumulation time series are now required from Antarctica, if satisfactory models of the long-term balance of the ice sheet are to be derived.

Bias-corrected suspended sediment rating equations are developed for the data from six separate ablation seasons in the Glacier de Tsidjiore Nouve basin. These equations differ significantly from one another. Suspended loads as predicted by equations used beyond their year of origin fall in the range of 34-278% of the true load. Mean absolute-percentage errors (MAPE) based on forecasts computed from each year’s model applied to the other 5 years of data range from 35 to 81%, with a mean of 52%. The equivalent MAPE for a lumped multi-year model is 38%, for an autocorrelation-correcting generalized least-squares (GLS) regression model, is 15%, and for a transfer function (TF) developed from a single 25 d period, only 5%. Simple structure-transfer functions appear to be more robust to temporal transfer than the usual type of rating equation, and offer the possibility of greatly improving upon the poor performance of OLS rating equations in providing estimates of suspended loads for periods beyond frames of origin.

A technique for analyzing sea-ice concentration and floe-size distribution by means of image processing is proposed. The sea ice was photographed by video camera from the ship. The technique proposed for analyzing sea-ice images can be applied on line or off line. In on-line analysis, sea-ice images photographed by a video camera are digitized in real time. Ice concentration is calculated by summing ice pixels of each row of a digital image and ice shape can be obtained roughly by a composition of each row. In off-line analysis, sea-ice images recorded to a video recorder are processed. Both ice shape and ice concentration can be obtained accurately by analyzing predetermined square regions of an image. Although the off-line method requires more time to calculate, it is useful for detailed analysis of regional ice properties. Computations of ice concentration and floe-size distribution are performed using images obtained between Breid Bay and Syowa Station in 1988.

In the period from 1982 to 1984, the Silesian University Expeditions investigated the annual cycle of the Hans Glacier velocity and front fluctuations. They also analysed the factors influencing these processes (J.Jania, L.Kolondra, E. Bukowska-Jania 1983).

Surrounding the Hans Glacier frontal zone, permanent tripods had been installed (by cementation in monolithic rocks) for the photo-theodolite, to establish three stereo-photogrammetric bases. While two of the three bases were used for surveying the fluctuations of the glacier front along the entire width (ca. 2.5 km), the remaining one was installed to record the velocity of the glacier by the time-parallactic method. Photogrammetric pictures were reiterated approximately every 10 days during August in 1982, 1983 and 1984. During the polar winters of 1982/83 and 1983/84, the oscillations of the glacier front were recorded at one base only. Pictures were taken once a month (also by moonlight). Using a Gornik-type seismograph, natural micro-tremors coming from the glacier were recorded continually, The seismograph works at the nearby Polish Polar Station, which operates a meteorological station.

The application of permanent metal tripods with an auto-centering disc made it possible to take successive pictures at the same external orientation of the camera on one hand, while, on the other hand, improving the convergent photographs (a similar approach was reported by U. Voigt 1966). On the glacier surface, ground points of control were signalled with a Maltese cross. The investigators made use of natural reference points, i.e. some characteristic features of the glacier surface. Maximum errors of the photogrammetric survey were mxy = ±0.3 m, mz = ±0.1 m.

The results of glacier tongue velocity measurements (ca 50 ma−1), as well as the results of measuring the fluctuations of the glacier front position enabled the rate of calving to be calculated. Thus, the calving velocity amounts to ca 100 ma−1 and the mass loss at the contact with sea water approaches ca 20% of the annual mass loss due to ablation.

The calving speed and the velocity of the glacier undergo variations in different periods of the year and the maxima of the processes do not overlap. While the glacier velocity reaches its maximum value at the beginning of the summer season (July), maximum calving speed is recorded in autumn (September-October). However, there may appear a shift in the time at which these maxima occur. It depends on the meteorological conditions and the thermal state of the sea in the given year. The effect produced by the two “antagonistic” glacial processes is the change in position of the glacier front in the sea. Its maximum and minimum extension appears by the end of July and in October, respectively. The amplitude of the Hans Glacier front fluctuations, measured for the period of August, 1982 to August, 1983, amounted to 60 ma−1 on the centre line. The results of photogrammetric surveying by C. Lipert, from 1957 to 1959, have shown that the maximum changes in the extension of the glacier front amount to 250 ma−1. These fluctuations display regularities similar to those reported for the Columbia Glacier, Alaska by C.S. Brown, M.F. Meier and A. Post (1982).

Analyses of micro-tremors coming from the glacier involved their variability in scale and frequency from one day to the next and throughout the year, as well as photogrammetric survey. Attempts were also made to find the englacial source of those micro-tremors. Source location was attempted in the summer of 1980, by using three geophones situated in the frontal part of the glacier. Thus, the majority of the micro-tremors owe their origin to the zone situated at a distance of 200 to 300 m from the front line and not to the ice cliff, as had been expected (A. Cichowicz, personal communication). It is worth noting that there exists an overlap of the annual distribution of the frequency of micro-tremor occurrence with the curve of glacier velocity variations. This enabled the investigator to determine the glacier dynamics by tremor recording.

A coupled ice-ocean model is used to study the sensitivity of the Beaufort Sea climatology to representation of sub-grid-scale eddies; to hypothetically not present and double Mackenzie River discharge; and to approximate climate warming specified through a surface air-temperature increase of 3° C. The eddy effect is considered in two ways: as eddy interaction with sea-floor topography yielding a driving force ("neptune" parameterization) and as eddy diffusion and viscosity. The model with neptune parameterization reproduces surface layer circulation, as well as the bathymetrically steered Beaufort Undercurrent, while the model with usual damping does not simulate the Beaufort Undercurrent. The absence of the strong boundary Beaufort Undercurrent affects the thermohaline structure of the Beaufort Sea which becomes less consistent with observational data. The increase of the Mackenzie River discharge causes more northward transport of sea ice, resulting in sea-ice thinning in Mackenzie Bay, while the absence of the Mackenzie River discharge induces southward sea-ice drift and sea-ice thickening in Mackenzie Bay. The sensitivity study of surface air-temperature warming shows a shrinkage of sea ice by 6% in area and 15% in volume, causing the freshening and warming of the surface ocean layer. The sensitivity studies of river discharge and surface air temperature use the neptune parameterization.

A new deep drill has been developed within the framework of the European Programme for Ice Coring in Antarctica (EPICA). Several versions of the EPICA drill exist. The version used at Dome Concordia (75˚06'1" S, 123˚23'71" E) was operated with a new electronic control system developed by the Ente per le Nuove tecnologie, l’Energia e l’Ambiente (ENEA) Research Center in Brasimone, Italy. This electronic control system was used for the first time during the 1997/98 Antarctic summer season.

Formation mechanisms of bent icicles and thin spikes were studied by observations of natural icicles and by artificially growing icicles in a cold laboratory, and the results are discussed with reference to the general growth process of icicles. It is shown that icicles can be bent by the displacement of their roots, change in water supply rates, and wind. Spikes were observed to grow by the freezing of a water column captured at the centre of icicles after their length and diameter growth stopped.

A numerical simulation of simple two-dimensional shear of round uniform grains is used to investigate the dynamic friction characteristics of the layer of snow at the base of an avalanche. For steady, uniform flow on a uniform flat surface, the dynamic friction coefficient transmitted through the shear array is found as it varies with the shear speed and normal force applied to the top of the shear layer, and the properties of the particles in the shear layer.

For this simple model, the flow in the shear layer is found to be independent of the total number of layers in the shear flow. A slip plane is formed along which most of the shearing motion takes places, so that the shear is confined to just two layers of particles which slide over one another. In the absence of gravity this slip plane jumps up and down randomly within the shear layer, which is otherwise composed of agitated semi-dispersed particles.

We review successes and challenges from five recent subglacial bedrock drilling campaigns intended to find evidence for Antarctic Ice Sheet retreat during warm periods in the geologic past. Insights into times when the polar ice sheets were smaller than present serve as guiding information for modeling efforts that aim to predict the rate and magnitude of future sea level rise that would accompany major retreat of the Antarctic Ice Sheet. One method to provide direct evidence for the timing of deglaciations and minimum extent of prior ice sheets is to extract subglacial bedrock cores for cosmogenic nuclide analysis from beneath the modern ice sheet surface. Here we summarize the lessons learned from five field seasons tasked with obtaining bedrock cores from shallow depths (<120 m beneath ice surface) across West Antarctica since 2016. We focus our findings on drilling efforts and technology and geophysical surveys with ground-penetrating radar. Shallow subglacial drilling provides a high risk, high reward means to test for past instabilities of the Antarctic Ice Sheet, and we highlight key challenges and solutions to increase the likelihood of success for future subglacial drilling efforts in polar regions.

Due to the nonlinear nature of the ice interaction, sea-ice build-up against coasts and structures is a complex process. This build-up signifycantly affects mesoscale (10 to 100 km) ice motions over typical forecast time scales of several days. To examine the ramifications of assuming a non-linear ice interaction in ice forecast models, we have carried out a series of idealized simulations employing a viscous plastic sea-ice rheology (Hibler 1979). These simulations employ constant wind fields at a grid resolution of 18.5 km and allow the ice to build up and strengthen. With the plastic ice interaction the ice build-up is found to take place by means of a ridging front. Depending on the nature of the strength-thickness coupling, this build-up is accompanied by kinematic wave propagation effects. The nonlinear interaction can also result in fluctuating velocities in certain locations, even though the forcing is fixed. The build-up results are found to be consistent with the analytic solution of a one-dimensional rigid plastic model.

Topographic sketch mapping of the whole ablation area of the Khumbu Glacier, East Nepal Himalaya, is performed, using a simple, stereo-photogrammetric method. This map shows that the surface morphology can be classified into 11 morphologic characteristics. Depending on their distribution and combination, the ablation area can be divided into four morphologic areas. Detailed maps, on a scale of 1:1000–2500, of these four areas indicate that the distribution and combination of these 11 morphologic characteristics result from thickness of the debris cover, supraglacial streams and ponds, and glacier dynamics. The irregularity in the ablation area of the Khumbu Glacier can be considered to be a consequence of the mass balance between rate of ice charge from upstream and irregular distribution of ablation rate, depending on debris-cover characteristics in situ.

Dynamic ice-sheet models are used to assess the contribution of mass loss from the Greenland ice sheet to sea-level rise. Mass transfer from ice sheet to ocean is in a large part through outlet glaciers. Bed topography plays an important role in ice dynamics, since the acceleration from the slow-moving inland ice to an ice stream is in many cases caused by the existence of a subglacial trough or trough system. Problems are that most subglacial troughs are features of a scale not resolved in most ice-sheet models and that radar measurements of subglacial topography do not always reach the bottoms of narrow troughs. The trough-system algorithm introduced here employs mathematical morphology and algebraic topology to correctly represent subscale features in a topographic generalization, so the effects of troughs on ice flow are retained in ice-dynamic models. The algorithm is applied to derive a spatial elevation model of Greenland subglacial topography, integrating recently collected radar measurements (CReSIS data) of the Jakobshavn Isbræ, Helheim, Kangerdlussuaq and Petermann glacier regions. The resultant JakHelKanPet digital elevation model has been applied in dynamic ice-sheet modeling and sea-level-rise assessment.

We report on changes to the snowpack of Ürümqi glacier No. 1, eastern Tien Shan, China, resulting from climate change between 1961 and 2005. Data from more than 120 snow pits were used to investigate temporal changes in the snow stratigraphy for three periods 1961–62, 1980–83 and 2002–05. Both the thickness and structure of the snow were found to be significantly altered by climatic warming. The proportion of coarse-grained firn, which is usually formed by infiltration water, was found to have increased from 40% to 65% over the period 1961–2005, and the distribution of the glacier zones also changed significantly, with all boundaries moving up-slope. The recrystallization–infiltration zone disappeared in 1989. The mean ablation rate over the melt season increased by ~26% from 1962 to 1980 at the west branch site and by ~75% from 1980 to 2004 at the east branch site.

Oceanographic, meteorological and sea-ice data were obtained from the northern Bering Sea and Chukchi Sea during the autumns of 1987 and 1988. Ice-edge location was observed from ships and via AVHRR satellite data, and ice-drift information was obtained from ARGOS-tracked drift buoys. Meteorological data were obtained from ships, from an ARGOS-tracked meteorological station and from synoptic charts. The ice edge was significantly farther south in 1988 than during other years and impacted the Alaskan coastline. In 1987, the ice edge was, conversely, anomalously far north. Ice melt-back in certain regions, such as along the Alaskan coast and in Herald Canyon, was due to input from warm ocean currents. The larger-scale interannual differences in ice extent were, however, due to interannual differences in the regional winds. In particular, the anomalous and extreme southward extent of the ice edge during 1988 was due to northerly to northwesterly winds, which held the summer pack ice against the the beach. Meltwater from this ice salt-stratified the upper water column, so that the ice eventually became effectively insulated against vertical flux of heat from the underlying warm water in the coastal current.

Laboratory results are presented concerning ice creep at minimum creep rate (at ~1% strain) for fine-grained, initially isotropic, polycrystalline samples. The effect on the creep rate of ice density, sample shape (aspect ratio) and size, grain-size and ratio of grain-size to sample size is examined. Provided sample density is above ~0.83 Mg m−3 (i.e. the close-off density), there is no effect of density on ice-creep rate. Results provide no evidence of a creep rate dependence on test sample length for cylindrical samples. Sample diameter, however, does affect creep rate. Over the range of sample diameters studied (16.2 to 90 mm) creep rate decreases monotonically by a factor of ~4. This effect is independent of sample aspect ratio. Experiments examining size effects in simple shear indicate no dependence of minimum flow rate on shape or size in this stress configuration. Two grain-sizes were represented within the samples tested for the effect of sample size. As expected from earlier work, no grain-size effect on minimum creep rate is evident. In addition, there was no evidence of an effect on creep rate of the ratio of grain-size to sample size.

In the 1979–80 field season, a site survey was carried out in the southern Weddell Sea for the construction of a wintering station. The survey comprised glaciological investigations on the Filchner and Ronne ice shelves, such as ice movement, deformation, ice thickness, calving, accumulation, and snow temperature measurements which are relevant to mass-balance studies. Along with the investigations on the ice, oceanographical and bathymetrical observations were carried out along the ice front. The field data and observations lead to assumptions about the advance of the ice shelf as well as about the mass loss at the frontal zone due to calving and bottom melting. The ice-front velocity at 50°W is about 1 070 m a−1 and the bottom melting is estimated to be 3.2 m a−1 at 20 km south-west of the ice front.

Blue Glacier was subject to 5 to 10% increase in thickness during the period 1958 to 1978. A surface velocity increase of 15 to 50% has accompanied this change in ice thickness. A non-uniform distribution of thickening over the glacier produced a general decrease in surface slope. The flow law parameters in a power-law relation for ice can be obtained from the resulting increase in velocity.

In 1957–58 the surface velocities and surface elevation along several transverse profiles were determined by others. During the period 1977 to 1980 similar measurements were made of surface velocity, elevation, and ice thickness along profiles spatially equivalent to those of the 1957–58 survey. Using these results a detailed study of the flow response has been made. Preliminary results indicate that the controlling surface slope a is one that is averaged over approximately ten times the glacier thickness and also indicate a relatively high stress exponent n = 4 to 5.

Blue Glacier flows in a complex channel and any detailed interpretation of the flow response requires the inclusion of this geometry in a model. For this reason multi-dimensional finite-element methods using a non-linear constitutive relation were employed. Various degrees of model sophistication allowed for the specification of different parameters governing the flow of the glacier. Variations in the flow law parameters and the curvature of the channel were found to have significant effects on the velocity and stress fields, as well as on the characteristics of the flow response to the thickness perturbation. Fully three-dimensional models of the flow of Blue Glacier and its response to the thickness increase were developed. Important effects such as those arising from longitudinal thickness and surface slope variations were included in three-dimensional modeling. The three-dimensional effects were seen to play an important role in flow of a rheologically non-linear fluid such as ice.

A method of determining the temporally varying “state” of the ice cover (the concentrations of three surface types: open water, first-year ice, and multi-year ice) is presented. The methodology is that of Kalman smoothing: a physical model and a measurement model are used to blend satellite passive microwave data and buoy data to give an optimal estimate of the ice state. The estimates are optimal only to the degree that model parameter values are known and assumptions about variances are met. Uncertainty about these values and assumptions, and lack of independent data with which to compare results,leaves self-consistency as the most important test of results. A four-year record (1979-82) of the estimated Arctic Ocean ice balance is presented and shown to be self-consistent. Results are discussed in terms of the Arctic multi-year ice balance, which may be an important factor in the interaction ofocean, sea ice and climate because of its relationship to the minimum summer ice extent. The estimated area of multi-year ice decreases each year, but the decrease is small and insignificant based on four years of results. Furthermore, the observed decrease may be due to instrument drift or changes in the multi-year ice signature.