Annual glacier mass balances are reconstructed for 96% of the Austrian glacier-covered area (451 of 470 km2) between 1969 and 1998. The volume change derived from two complete glacier inventories (1969 and 1998) serves as the boundary condition that is aimed to be reproduced. ERA-40 reanalysis data as well as a gridded precipitation dataset (HISTALP) are used to drive a positive degree-day (PDD) model. The results are verified with four independent long-term mass-balance series. The spatial and vertical distribution of the tuning parameters is altered in order to reproduce the measured mean annual surface mass balances of selected glaciers, and a strong correlation is found between the median elevation of a glacier and the degree-day factor (DDF) at this elevation. This result implies that the lower a glacier’s median elevation is, the less melt occurs at a given elevation and temperature. We attribute this to the fact that lower-altitude glaciers are generally those with more accumulation, which leads to later exposure of bare ice and a longer period of high-albedo snow cover. A further improvement of the model was achieved by making DDF a function of time as well as space. The results indicate that mean DDFs generally increase for a given date over a sequence of consecutive negative mass-balance years, which probably reflects the reduction in albedo related to that. Finally, the major drivers of the observed mass-balance evolution are investigated: summer PDD sums correlate significantly better with the observed mass-balance changes than annual PDD sums or precipitation do. This implies that annual mass balances in the study area are governed by summer temperatures.

Detailed measurements of sediment flux in meltwaters draining from the portal of Gornergletscher, Valais, Switzerland, each ablation season between 1987 and 1990 indicate the nature of interactions between the developing basal drainage system and sediment stored at the glacier subsole. Sediment-flux maxima, which were generally smaller and less frequent later in a season, occurred at times of rising discharge. Overall, sediment flux first increased then decreased during a season. A simple conceptually based model is proposed for the subglacial interaction between flowing meltwater and sediment derived from glacial abrasion. The model was developed in order to allow investigation of relationships between suspended-sediment flux and discharge in meltwaters draining from temperate glaciers, In the model, water spreads out over a grid-square bed such that the area of subsole integrated with flow is a function of discharge. Sediment is abraded from the bed at a uniform rate in cells not covered by water. In winter, sediment accumulates over almost all the bed. Periods of rising flow at the start of the ablation season lead to drainage net expansion, much entrainment of stored sediment and large flux events in portal meltwaters. The model allows redistribution and deformation of stored sediment in two directions. Sediment squeezed to the margins of the wetted area throughout summer provides the background level of sediment flux between events. Reduction in total channel-margin length with progressive changes in drainage-network topology explains declining background flux later in summer. The model replicates well the timing, but not the absolute and relative magnitudes, of sediment-flux maxima in portal meltwaters draining from Gornergletscher.

The cryosphere is represented in some hydrological models by the areal extent of snow cover, a variable that has been operationally available in recent years through remote sensing. In particular, the snowmelt–runoff model (SRM) requires the remotely sensed snow-cover extent as a major input variable. The SRM is well-suited for simulating the hydrological response of a basin to hypothetical climate change because it is a non-calibrated model. In order to run the SRM in a climate-change mode, the response of the areal snow cover to a change in climate is critical, and must be calculated as a function of elevation, precipitation, temperature, and snow-water equivalent. For the snowmelt-runoff season, the effect of climate change on conditions in the winter months has a major influence. In a warmer climate, winter may experience more rain vs snow events, and more periods of winter snowmelt that reduce the snow water equivalent present in the basin at the beginning of spring snowmelt. As a result, the spring snowmelt runoff under conditions of climate warming will be affected not only by different temperatures and precipitation, but also by a different snow cover with a changed depletion rate. A new radiation-based version of the SRM is under development that will also take changes in cloudiness and humidity into account, making climate-change studies of the cryosphere even more physically based.

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

Measurements of the bore-hole diameter were made with three-contact-point calipers from the shallow layer to a depth of 700 m at Mizuho Station, East Antarctica, in 1984–86. The minimum strain-rate (i.e. secondary creep rate) of the bore-hole closure was estimated from the observed creep curve at each depth. A relation between stress and strain-rate was deduced for a temperature of −35°C and a stress range from 0.8 to 1.65 MN m−2, as

where is the effective strain-rate (s−1) and τ is the effective shear stress (MN m−2). This result shows that, for comparable overburden stresses and temperature, the bore-hole closure rates at Mizuho Station are higher than those measured in bore holes at Byrd Station and in the Northern Hemisphere ice caps (Paterson 1977).

The two-dimensional wavelet transform is a highly efficient band-pass filter, which can be used to track features in satellite images from sequential paths. Wavelet analysis of NASA scatterometer and Special Sensor Microwave/Imager data has been used to obtain daily sea-ice drift information for the Arctic region. Comparison with ice motion derived from ocean buoys shows good quantitive agreement. Furthermore, the scatterometer results definitely complement passive-microwave radiometer results when there are cloud or surface effects. This outcome allows three sets of sea-ice-drift daily results from scatterometer, radiometer and buoy data to be merged as a composite map by data-fusion techniques. Based on the composite maps, the ice-flow streamlines are highly correlated with surface air-pressure contours. In order to quantify the wind effects on ice motion, empirical orthogonal functions are used in the principal-component analysis to isolate generalized patterns inherent in 6 months (fall/winter) of daily sea-ice motion data. It is found that 30% of sea-ice motion is highly correlated with 50% of the pressure field in modes 1 and 2. For the higher modes, sea-ice motion is also affected by ocean current, bathymetry and coastal boundary and therefore is not highly correlated with the wind field.

A large scale study on the dependence of time lag of runoff on snow depth and stratigraphy was carried out in a watershed. The time lag in peak runoff was found to be increased by 1.5 - 4 h per I m increment in snow depth. Although the data were widely scattered, it was found that the time lag series converged in a line every year and that discrete layers in the snow cover composed in a warm winter, accelerated meltwater flow.

Subtracting the time of propagation through a snowcover from the total time lag, the effect of size of a watershed on a delay in runoff was rearranged, as follows: where Tf is the time lag in min after discharge from a snow cover, A the area of a watershed in km2, Re the effective snowmelt in mm/hr. The time lag Tf increases only by 1.5 times when an area of a watershed is increased by a factor of ten.

Atmospheric general circulation models are believed to be appropriate tools for studying airborne impurity cycles in order to supplement observations and to improve our knowledge of gaseous and particulate pollutant cycles in the atmosphere. The main aspects of the modelling of tracer cycles are reviewed and illustrated by two particular examples: desert dust particles in the 1 μm range and water isotope species HDO and H218O. Some results from a first simulation including desert dust and water isotope cycles using the model developed at the Laboratoire de Météorologie Dynamique (LMD) are presented and compared to observations, with particular emphasis on ice-sheet data. The relatively good agreement with observations obtained so far is encouraging and should stimulate further applications to other types of tracers.

The influence of advective and eddy transport of atmospheric moisture on the 18O content of atmospheric vapour and precipitation is discussed. Measurements of the 18O content of atmospheric vapour and precipitation have been carried out since July 1981 in Uppsala, Sweden. The removal of water from atmospheric vapour is accomplished by freezing it out of a stream of air passed at the rate of 60 1 h−1 through cooling traps maintained at a temperature of −60°C. The method is practically non-fractionating. The observed slopes of the regression equations defining the linear relationship between weighted monthly δ18O of precipitation and mean monthly temperatures at the ground level agree fairly well with the predicted slopes assuming that the transport of atmospheric moisture is due to eddy motion. Similarly the slope of the linear relationship between δ18O in atmospheric vapour and vapour density at ground level is also closely predicted by the eddy transport model. However, if it is assumed that the transport of atmospheric moisture is advective, the predicted slopes are nearly double those observed.

It was also observed that precipitation and atmospheric vapour are in isotopic equilibrium during summer, but not during winter. Results obtained confirm the strong large-scale eddy diffusive nature of the transport of atmospheric moisture.

Glacier-bed characteristics that are poorly known and modeled are important in projected sea-level rise from ice-sheet changes under strong warming, especially in the Thwaites Glacier drainage of West Antarctica. Ocean warming may induce ice-shelf thinning or loss, or thinning of ice in estuarine zones, reducing backstress on grounded ice. Models indicate that, in response, more-nearly-plastic beds favor faster ice loss by causing larger flow acceleration, but more-nearly-viscous beds favor localized near-coastal thinning that could speed grounding-zone retreat into interior basins where marine-ice-sheet instability or cliff instability could develop and cause very rapid ice loss. Interpretation of available data indicates that the bed is spatially mosaicked, with both viscous and plastic regions. Flow against bedrock topography removes plastic lubricating tills, exposing bedrock that is eroded on up-glacier sides of obstacles to form moats with exposed bedrock tails extending downglacier adjacent to lee-side soft-till bedforms. Flow against topography also generates high-ice-pressure zones that prevent inflow of lubricating water over distances that scale with the obstacle size. Extending existing observations to sufficiently large regions, and developing models assimilating such data at the appropriate scale, present large, important research challenges that must be met to reliably project future forced sea-level rise.

To increase inclusivity, diversity, equity and accessibility in Antarctic science, we must build more positive and inclusive Antarctic field work environments. The International Thwaites Glacier Collaboration (ITGC) has engaged in efforts to contribute to that goal through a variety of activities since 2018, including creating an open-access ‘Field and Ship Best Practices’ guide, engaging in pre-field season team dynamics meetings, and surveying post-field season reflections and experiences. We report specific actions taken by ITGC and their outcomes. We found that strong and supported early career researchers brought new and important perspectives regarding strategies for transforming culture. We discovered that engaged and involved senior leadership was also critical for expanding participation and securing funding to support efforts. Pre-field discussions involving all field team members were particularly helpful for setting expectations, improving sense of belonging, describing field work best practices, and co-creating a positive work culture.

This paper presents a review of the ice-sheet mechanics behind the modeling work of Pleistocene ice sheets driven by astronomical (Milankovitch) forcing.

Antarctic iceberg observations provide two types of climatic information: (1) the rate of iceberg calving gives the main negative term in the mass balance of Antarctica; (2) the distribution of icebergs in the Southern Ocean is related to various factors including sea-ice extent and ocean conditions. This paper discusses climatic information obtained both from modern iceberg observations, and from historical data.

The main modern data source is the international iceberg observation programme, initiated in 1981. This has generated a database which now contains observations of size and position of 150 000 icebergs in the Southern Ocean. Other recent data sources include observations from 1974 of icebergs of over 22 km length by the Navy/NOAA Joint Ice Center (which now total nearly 100 bergs). Historical sources include both scientific and commercial (whaling) expeditions.

Three conclusions can be drawn from the recent iceberg data.

• (1) For the past seven years annual calving rates of icebergs less than 22 km in length have been approximately constant both in numbers and total mass, and have exceeded the annual mean mass of bergs over 22 km calved during the same period.

• (2) The annually-calved mass of gigantic icebergs of length over 22 km, has varied more than two orders of magnitude during the past two decades. The mass of calved gigantic icebergs alone exceeded continental snow accumulation in 1967, 1986 and 1987.

• (3) Mean iceberg calving rate exceeds continental snow accumulation rate.

These results are discussed in relation to Antarctic mass balance and sea level.

Historical observations of iceberg distributions in the Southern Ocean differ from recent observations by showing: (i) higher frequencies of bergs at lower latitudes, (ii) a larger proportion of large bergs, and (iii) a more uniform iceberg distribution throughout the region. Comparisons between past and present distribution patterns indicate that there must be errors, including exaggerations and selective reporting, in the historical data. Such observations should therefore not be used uncritically to make climatic conclusions.

Bearing in mind the potential flaws in historical data there still appears to be real variations with time in iceberg distribution. These include higher frequencies of bergs at lower latitudes during the past century and the first decades of this century, than at present. Expanded northern range of the bergs would occur if one or more of the following conditions then applied: (1) calved icebergs were larger; (2) sea ice was more extensive in time and space; (3) ocean temperatures were lower; (4) ocean (wind) conditions were such that northward advection rates were higher. The importance of each of these conditions is discussed.

Passive-microwave sea ice concentration (SIC) algorithms employ different frequencies and polarisations in their operational implementations. Commonly, these algorithms utilise combinations such as 19/37 GHz, yielding reduced measurement uncertainties but at a coarse spatial resolution. Alternatively, these algorithms can solely use 89 GHz, producing a higher spatial resolution but with increased measurement uncertainties. This study evaluates the application of a resolution-enhancing SIC algorithm (reSICCI3LF), initially developed for the coarser Special Sensor Microwave Imager / Sounder, on the Advanced Microwave Scanning Radiometer. By applying reSICCI3LF, we aim to produce a 5 km SIC for 2013–2020 in the Fram Strait and the Barents and Kara Sea region that gains the benefits of both types of algorithms, high spatial resolution and low measurement uncertainty.

We present the algorithm tuning, spectral analysis of spatial resolutions, and validation against the Round Robin Data Package of 0% and 100% SIC points and SIC derived from Landsat-8. The findings demonstrate that the reSICCI3LF algorithm produces a SIC field with fine details, achieving a balance between high spatial resolution and lower measurement uncertainties compared to a 89 GHz based SIC. Consequently, this resolution-enhanced SIC technique can potentially initialise higher-resolution coupled ocean and sea ice forecasting systems through data assimilation.

Long-term ice records (1823-1994) from six sites in different parts of the Laurentian Great Lakes region were used to show the type and general timing of climatic changes throughout the region. The general timing of both freeze-up and ice loss varies and is driven by local air temperatures, adjacent water bodies and mixing, and site morphometry. Grand Traverse Bay and Buffalo Harbor represent deeper-water environments affected by mixing of off-shore waters; Chequamegon Bay, Menominee, Lake Mendota, and Toronto Harbor represent relatively shallow-water, protected environments. Freeze-up dates gradually became later and ice-loss dates gradually earlier from the start of records to the 1890s in both environments, marking the end of the “Little lce Age”. After this, freeze-up dates remained relatively constant, suggesting little change in early-winter air temperatures during the 20th century. Ice-loss dates at Grand Traverse Bay and Baffalo Harbor but not at the other sites became earlier during the 1940s and 1970s and became later during the 1960s. The global warming of the 1980s was marked by a trend toward earlier ice-loss dates in both environments.

The distribution of mean net accumulation rate over a large sector (90°E to 150°E) of the IAGP (International Antarctic Glaciological Project) area in Antarctica is presented in map form. The basic data have been compiled from direct measurements of accumulation at stake networks, and by dating horizons in the snow pack by gross β-activity measurements, on four long traverse routes. The spatial variability can be high, over 40%, for a single year, and typically about 20% for multiyear averages. Local surface topography in the form of undulations of several kilometres wavelength can account for about 35% of the variance. Averaging over Intervals of 50 km or more will give the smooth large-scale distribution pattern. But the resultant values can still deviate from the long-term average accumulation by 25% or more due to temporal variability over time scales of years to decades.

A very high correlation (r = 0.97) was found for the relationship a = 1414 exp (0.060 θ10) between accumulation, a kg m−2 a−1, and 10 m depth snow temperature, θ10°C, when the data set was limited to a single large drainage basin in Wilkes Land.

The seasonal ice-free period in the Hudson Bay Complex (HBC) has grown longer in recent decades in response to warming, both from progressively earlier sea-ice retreat in summer and later sea-ice advance in fall. Such changes disrupt the HBC ecosystem and ice-based human activities. In this study, we compare 102 simulations from 37 models participating in phase 6 of the Coupled Model Intercomparison Project to the satellite passive microwave record and atmospheric reanalyses. We show that, throughout the HBC, models simulate an ice-free period that averages 30 d longer than in satellite observations. This occurs because seasonal sea-ice advance is unrealistically late and seasonal sea-ice retreat is unrealistically early. We find that much of the ice-season bias can be linked to a warm bias in the atmosphere that is associated with a southerly wind bias, especially in summer. Many models also exhibit an easterly wind bias during winter and spring, which reduces sea-ice convergence on the east side of Hudson Bay and impacts the spatial patterns of summer sea-ice retreat. These results suggest that, for many models, more realistic simulation of atmospheric circulation would improve their simulation of HBC sea ice.

We drilled an 81.2-m-long ice core in the accumulation area (5860 m a.s.l.) of Trambau Glacier in the Rolwaling region during October–November 2019. The drilling operation was conducted with a lightweight electro-mechanical drill system after two reconnaissance fieldworks in 2017 and 2018, during which two shallow firn cores were drilled with a hand auger. The drill system and ice core samples were transported by helicopters at a high elevation of 6000 m a.s.l. A further challenging issue was the ice core transportation between Nepal and Japan, as no regular commercial flight was available for the frozen samples. The addition of dry ice imported from India immediately prior to leaving Nepal allowed the ice core samples to be successfully transported to a cold room in Japan, and remain in a frozen state. Stratigraphic observations during the drilling operation suggest the drill site has been affected by melting and refreezing.

Recently, innovations in ice drilling have yielded considerable improvements to existing drilling techniques, as well as innovative drilling technologies that can be used in new types of applications. However, some specific challenges have to be addressed for improving existing drilling methods and developing new ones: (1) combination and unification of different drilling systems; (2) facilitating ice core breaking; (3) improving existing systems and developing new rapid-access ice drilling systems; (4) reliable elimination of ice hydraulic fracturing problems; (5) developing new environment-friendly methods of drilling in the sub-glacial lake sediments; and (6) design of unconventional ice drilling systems. Possible solutions to these problems are presented herein.

The paper discusses the verification of a previously developed structural dry-snow model based on the regular packing of isometric grains connected by rigid bonds. Using this model, we consider the probable snow-compaction mechanisms at different snow-density ranges (from new to dense snow), limited by critical densities corresponding to the real values of the structural indices of the model: texture looseness, bond rigidity and coordination number. We also obtain the analytic expression for longitudinal wive velocity and for bulk compressibility of snow as functions of density and structural indices. The calculation enables us for the first time to show the whole range of possible values of these important characteristics and to deduce the most probable configuration of the ice matrix in snow of various densities corresponding to the experimental data available on the snow-texture peculiarities and elastic-wave velocities. The model can be used to comprehend the changes in snow mechanical properties during compaction, as well as the steps by which it proceeds.