This paper summarizes the 37 year history of net accumulation measurements at the geographic South Pole obtained by numerous investigators using a variety of techniques. These data lead to the conclusion that annual net snow accumulation has increased in the vicinity of South Pole Station (SPS) since 1955. The records were examined for evidence of a “station effect” and it is concluded that not all of the observed increase can be attributed to snow drift associated with the presence of the station. Furthermore, the accumulation increase at the South Pole appears consistent with increases observed at other locations on the East Antarctic Plateau, and in the Peninsula region as well. These data suggest that the recent accumulation increase at SPS may be regionally extensive over the East Antarctic Plateau.

Shallow ice cores from an Antarctic blue-ice area at Scharffenbergbotnen were l4C-analyzed using a dry-extraction technique and accelerator mass spectrometry. The in situ production was determined from the 14CO component and used to deduce the natural 14CO2 component. The ages were measured at 10 000 ± 3000 BP. The accumulation and ablation rates determined from the in situ production are 7–20 and 10 cm a−1. respectively, showing agreement with field observations. The derived ages and air-yield data show a nearby origin for the surface ice.

A simple steady-state energy and mass-balance model of the Antarctic ice sheet is developed. Basically it is a set of two equations with two unknowns of steady-state height h and potential basal temperature Tb. Tb determines whether, and to what extent, there is liquid water at the base of the ice which in turn affects the values of h and Tb. Simultaneous changes of sea-level temperature and precipitation (changes related to each other as might be expected from global climate models) indicate a maximum in the field of possible steady-state ice volumes which may not be far from the presently observed conditions. The possibility of cyclical variation in ground heat flux associated with convection of water and heat in the continental crust is discussed. The mechanism might be capable of generating cycles of ice-sheet volume with relatively short periods similar to those of Milankovitch forcing.

Previous attempts to derive the Antarctic surface net accumulation distribution from atmospheric-moisture fluxes, in reasonable agreement with the observed distribution, have encountered many difficulties. The present analysis uses the Australian Bureau of Meteorology Global Atmospheric Assimilation and Prediction Scheme (GASP), which has been operational since 1989, to derive the net air-mass and moisture fluxes over the Antarctic. It is shown that the annual mean net surface accumulation closely resembles the glaciologically observed distribution and provides a physical basis for the observed pattern, through the moisture transports. The variations with latitude and elevation and through the annual cycle are also well reproduced. Although some mass-closure errors still exist, they are expected to become insignificant with the new generation of improved analysis schemes. Consequently the atmospheric analyses can provide a sound basis for both assessing the performance of global climate models in simulating Antarctic accumulation rates and monitoring long-term changes which may occur with global warming.

On time-scales of less than about 100 years, when the ice topography can be considered stationary, the extent of Antarctic blue-ice areas is governed mainly by the surface mass balance. In and near high-elevation blue-ice areas, ablation is due entirely to sublimation. An estimate of the mass-balance profile ranging from a blue-ice area to the adjacent snow surface is presented. By considering changes in sublimation induced by variations in local climate, the deviation from the mass-balance profile is evaluated. It is concluded that even for considerable changes in local climate these deviations remain relatively small and have only little effect on the extent of a blue-ice area. This can be attributed mainly to the steep mass-balance profile.

During the Norwegian Antarctic Research Expedition 1993/94, field studies were conducted on a blue-ice field in Jutulgryta, Dronning Maud Land. Measurements of sub-surface temperatures revealed that temperatures in blue ice were about 6°C higher than in the adjacent snow. Despite the predominantly negative air temperatures, a sub-surface melt layer was discovered within the uppermost metre of the blue ice. Here the temperature maximum was consistent throughout the entire month of observations, and resulted in both internal melt and water transport. The melting is a consequence of solar radiative penetration and absorption within the ice, i.e. the “solid-state greenhouse”. Sensitivity experiments using a non-stationary combined radiative and thermodynamic model reveal that the physical properties (here extinction coefficient, radiation transmittance and albedo) strongly control the formation and vertical extent of the melt layer. The persistence of the sub-surface melt layer increases the runoff volume from blue-ice fields, which otherwise might be restricted to a few yearly events when air temperatures reach or exceed the freezing point. The conditions required for melting activity are marginal in Jutulgryta. Hence, this phenomenon may serve as an indicator of climate fluctuations in the area.

Detailed records of methanesulphonic acid (MSA) and non-sea-salt sulphate (nss SO42−) have been obtained from ice cores drilled on Dolleman Island on the east coast of the Antarctic Peninsula (70°35.2′S, 60°55.5′W). Annual average concentrations of MSA are presented for the period 1652–1992. Over this time span, the mean annual concentration of MSA is 0.69 μeq l−1 (σ = 0.33, n = 340), the range is 0.13–2.35μeq l−1, and the MSA/nss-SO42− ratio is 0.22. The high MSA concentration reflects the proximity of the Weddell Sea, believed to be a region of high marine phytoplankton production. The overall mean nss-SO42− concentration is about 66% of the total sulphate deposited in the snowfall. Low-frequency variations of MSA and oxygen-isotope signals correlate closely, indicating that they may be modulated by similar atmospheric processes. Positive correlations are observed between the oxygen-isotope signature and both MSA (r = 0.41) and nss SO42− (r = 0.50), significant at the 99% level. A small negative correlation can be seen between both species and the annual duration of sea ice at Scotia Bay, Laurie Island in the South Orkneys, since 1902 (MSA r= –0.23, and nss SO42–r = –0.29; significant at 95% confidence). No significant link between high MSA concentrations and El Niño events is observed at this location.

In 1992, an American-Chinese expedition successfully recovered three ice cores (308.6, 93.2 and 34.5m) from the Guliya ice cap (summit 6710 m a.s.l) in the far western Kunlun on the Qinghai–Tibetan Plateau, China. Guliya resembles a “polar” icecap with 10 m, 200 m and basal temperatures of –15.6°, –5.9° and –2.1°C, respectively. The 308.6 m core to bedrock is the longest ice core retrieved from an elevation greater than 4000 m a.s.l. and provides the first ice-core history from the western side of the Qinghai Plateau. The Plateau experiences a pronounced annual precipitation cycle during which 70–80% of annual total precipitation falls in the summer monsoon season. This leads to a marked visible stratigraphy in the glaciers which allows accurate dating of the ice cores and reconstruction of the net mass accumulation.

This paper presents (1) the results of the geophysical program to determine ice thickness, ice flow and surface topography, (2) an assessment of net accumulation from stake measurements, snow pits and shallow core samples, and (3) the analyses of the upper 100 m of the 308.6 m core which provide a 1000 year history, including the ‘“Little Ice Age”, which is compared with Chinese historical records. Extended periods of positive accumulation on Guliya are closely contemporaneous with dry periods in eastern China. A trans-Pacific teleconnection is suggested by the strong temporal coherence between extended wet and dry phases on Guliya and on the Quelccaya ice cap, Peru.

Detailed ionic analyses of Dyer Plateau snow show that major soluble impurities in snow consist of sodium (Na+), chloride (Cl−), nitrate (NO3−), sulfate (SO42−), and acidity (H+). The ratios of Na+ to Cl− concentrations are close to that of sea water, indicating little or no fractionation of sea-salt aerosols. The analyses of core sections from three sites along a 10 km transect show that local spatial variation of snow chemistry in this area is minimal and that temporal (decadal, inter-annual and sub-annual) variations in snow chemistry are very well preserved.

Anion analyses of the upper 181 m section of two 235 m ice cores yield a data set of 485 years (1505-1989) of annual snow accumulation and fluxes of Cl−, NO3−, and non-sea-salt (nss) SO42−. No significant long-term trends are observed in any of the anion fluxes. This is consistent with other Antarctic ice-core records showing no significant anthropogenic atmospheric pollution in the high southern latitudes. Linear regression analysis shows that Cl− flux is independent of snow-accumulation rate. Significant positive correlations are found between accumulation rate and both NO3− flux and background nss-SO42− flux. These results suggest that dry deposition is primarily responsible for air-to-ground Cl− flux while wet deposition dominates the NO3− and nss-SO42− flux (≥90% and ≥75%, respectively). The nss-S042− fluxes provide a chronology of explosive volcanic emissions reaching the Antarctic region for the past 485 years.

Since 1987, ice cores have been drilled from the Dunde and Guliya ice caps on the Tibetan Plateau, western China. Here, the oxygen isotopic (δ18O) records for the last 1000 years from both these cores are compiled and compared. Using surface temperature observations since the mid-1960s from meteorological stations on the plateau and δ18O measured on precipitation collected contemporaneously, the empirical relationship: δ18O = 0.6 Ts – 12 is established. δ18O appears to serve as a reasonable proxy for regional surface temperatures and a reasonable basis for reconstructing 1000a proxy temperature records from Dunde and Guliya. The reconstructed temperature histories for Dunde (on the eastern Tibetan Plateau) and Guliya (on the western Tibetan Plateau) show some centennial-scale similarities, but reveal quite different histories for higher-frequency variability over the last millennium. The ice-core δ18O histories from Dunde and Guliya are compared with a tree-ring index from western China and the dust-fall record from eastern China, but show no consistent relationship. The most prominent similarity between the reconstructed temperature histories for Dunde and Guliya is the marked warming of the last few decades. From the 1000a perspective provided be these ice-core records, the recent warming on Dunde is unique in its strength and persistence; however, the warming on Guliya (inferred from 18O enrichment) is more recent (since 1985) and not unprecedented. This recent warming over the Tibetan Plateau is evident in the limited meteorological records.

Oxygen-isotope ratios (δ18O) measured on ice cores on the Qinghai-Tibetan Plateau, China, increased by 1.2-2.2‰ from the 1960s to the 1990s. Measurements of the δ18O content of precipitation and the simultaneous air temperatures needed to compute the temperature increase corresponding to the increase in δ18O are currently made at the Delingha Meteorological Station, but the amount of data is not yet sufficient to obtain a reliable result.

The spatial extrapolation of data from ice cores depends on the complexity of the glacier system where the drilling site is located. The correlation between net mass balance, bn, of a specific point and of the whole glacier is different for each point. Analysis of net mass balance of Tuyuksu glacier in the Tien Shan, central Asia, confirms that the distribution of mass balance with height is more-or-less constant from year to year except in years with extreme values bn. Two types of “similarity” are described, additive and multiplicative. The “similarity” changes gradually from additive at the peripheral parts of the Tien Shan to multiplicative in the most continental central and eastern parts. Glacier mass-balance fluctuations of the frontal ridges are connected to the oscillations of accumulation and consequently to precipitation. Where the climate is more continental the mass-balance variability depends much more on the melting conditions than on accumulation. For the spatial interpretation of ice-core drilling results, a special analysis of “similarity type” is necessary. It allows the fixing of the spatial borders of the glacier system for which the dhilling site is representative.

A parameterization scheme using simple algorithms for unmeasured glaciers is being applied to glacier inventory data to estimate the basic glaciological characteristics of the inventoried ice bodies and simulate potential climate-change effects on mountain glaciers. For past and potential climate scenarios, glacier changes for assumed mass-balance changes are calculated as step functions between steady-state conditions for time intervals that approximately correspond to the characteristic dynamic response time (a few decades) of the glaciers. In order to test the procedure, a pilot study was carried out in the European Alps where detailed glacier inventories had been compiled around the mid-1970s. Total glacier volume in the Alps is estimated at about 130 km3 for the mid-1970s; strongly negative mass balances are likely to have caused a loss of about 10–20% of this total volume during the decade 1980–90. Backward calculation of glacier-length changes using a mean annual mass balance of 0.25m w.e.a−1 since the end of the “Little Ice Age” around 1850 AD gives considerable scatter but satisfactory overall results as compared with long-term observations. The total loss of Alpine surface ice mass since 1850 can be estimated at about half the original value. An acceleration of this development, with annual mass losses of around 1 m a−1 or more as anticipated from IPCC scenario A for the coming century, could eliminate major parts of the presently existing Alpine ice volume within decades.

A 2.2 m deep pit and the top 42.5 m of an ice core recovered at Snøfjellafonna, northwestern Spitsbergen, were continuously analyzed for Na+, Cl−, NO3−, SO42− and pH. Seasonal variations in ionic concentrations seem to have remained in the pit and the core, in spite of the relatively severe summer melting. We dated the core by counting annual peaks of Na+ and made an adjustment with the use of a tritium peak in 1963 as a reference horizon. It turned out that the depth of 42.5 m went back to the early 1930s or late 1920s. The 60–70 year record of snow chemistry showed that the concentrations of both NO3− and SO42− had increased in the 1950s and had decreased in the late 1970s and the 1980s. The increase would be explained in terms of anthropogenic inputs from the industrial areas. The later decrease of the same ions may have been caused by a combination of the reduction of the atmospheric precursors due to pollution controls and the meltwater-associated processes.

A simple model tests the effect on ice-core impurity concentrations of climate-induced changes in the physical conditions of the atmosphere influencing transport and deposition processes, while keeping source areas and production rates constant. The model results show that the increased glacial concentrations observed for most impurities can be explained entirely by changes in transport and deposition. No increase in source emission is necessary, however possible, to explain the ten-fold increase in impurity concentrations during the Last Glacial Maximum. This shows that the effect of dynamic changes in the atmosphere can be large and has to be taken into account before translating deposition records into emission records. The total impurity content in the global atmosphere during the glacial period was higher if dynamic changes in the atmosphere rather than source-emission changes were responsible for the variations observed in polar areas. This implies that a climate-forcing mechanism is to be found in the dynamics of the atmosphere, since the radiative properties of the atmosphere depend on the total content of impurities in the atmosphere. The effect on the climate can probably be compared with, although opposite in sign to, the present-day anthropogenic greenhouse forcing.

Ice cores recently drilled to bedrock on the col of Huascarán (9°06′ S, 77°36′ W, 6047 m a.s.l.) offer the potential for a long, annually resolved climate record from tropical South America. This paper presents the record from 1950 to 1993 preserved in microparticle and nitrate concentrations and oxygen-isotopic ratios. Average monthly temperatures from a satellite-linked automatic weather station installed on nearby Hualcán in 1991 are presented. Annual temperatures from local high-altitude meteorological stations, along with the annual Huascarán isotopic record, show a warming trend over the last two decades. The marked preservation of the climate record in oxygen-isotopic ratios on Huascarán is absent at lower-elevation sites, which have been affected by the recent warming. This paper demonstrates the establishment of a time-scale for the Huascarán core, the preservation of the climatic signal with depth and the linkage of the ice-core “proxy-climate” parameters with measured climatic variations.

Detailed surveys of McCall Glacier in the Alaskan Arctic reveal changes from 1972 to 1993. The ice surface dropped everywhere, by amounts ranging from about 3 m in the highest cirques tq more than 42 m near the present terminus. The total volume loss was 3.5+ 0.2 x 10' m(, resulting in an average mass balance of 0.33 + 0.01 in a . l he terminus has retreated by about 285 m at a rale of 12_.5 ma \ Results from photogrammetry for an earlier period, 1958-71, were I.16x 10'm3 and 0.13 ma for volume change and mass balance, respectively; the mean terminus retreat rate was then 5.7 m a . The changes have to be seen in the context of McCall Glacier’s low mass-exchange rate; annual accumulation and ablation, averaged over the years 1969 72 were only +0.16 and 0.3 m a '. Cross-profiles in the ablation area, surveyed at intervals of a few years, show an increased drop rate since the late 1970s. 7 he volume-ehange data suggest a climate warming in the early 1970s. Enhanced thinning of the lower ablation region and accelerated terminus retreat seem to lag this climate change by not more than 10 years, This indicates a reaction time of McCall Glacier that is considerably shorter than its theoretic response time of about 50 70 years.

Lichenometry was used to date “Little Ice Age” moraines in the Kamchatka peninsula, northeastern Russia. The Rhizocarpon geographicum growth-rate curve was based on seven data points from lava flows and moraines, dated using historical records or tephrochronology (15–300 BP). No reduction in growth rate due to decreasing lichen age was observed, so a linear approximation was used. Accuracy test results yield differences between real and calculated dates up to, but not exceeding, five years. From eight “Little Ice Age” (LIA) moraines it was established that Kamchatka glaciers advanced in the 1690s, 1850–70 and 1910–20. Only one moraine clearly corresponded to the 1690s advance. The maximum stage of the LIA was during the mid- to late 19th century when glacier fronts were generally 100–200 m lower than at present. Glacier termini with ash and moraine layers, covered by lichens and vascular plants, have been preserved for 150–300 years, judging by the lichen sizes.

Data from twice-daily radiosonde flights are used to estimate spatial and temporal variations of air temperature, atmospheric transmissivity, wind speed and humidity at Blue Glacier, western Washington. U. S.A. Results indicate that the free-air conditions (interpolated in altitude and in time from radiosondes) provide a much better estimate of conditions on the glacier than do measurements from low-altitude stations. Data from the radiosondes are used to model the hourly exchange of mass and energy at the surface of Blue Glacier. In the absence of explicit information about clouds, temperature and humidity profiles from the radiosonde are used to estimate the atmospheric transmissivity needed for the calculation of short-wave radiation. Topographical influences (altitude, shading, slope angle and orientation) and surface albedo are parameterized explicitly to model the absorbed solar flux at specific sites on the glacier, Other energy fluxes (long-wave radiation, sensible-heat and latent-heat exchange) are estimated using established physical models. Hourly estimates of ablation are integrated to obtain the seasonal ablation. Modeled ablation and stake measurements made over 30 a at two sites on Blue Glacier agree within 16%, which is within the error associated with stake measurements of ablation.

Fluctuations in the position and surface altitude of Leverett Glacier, a small outlet glacier at the western margin of the Greenland ice sheet, are determined from a photogrammetric analysis. During the Greenland Ice-Margin Experiment (GIMEX) 1992 expedition, six control points were measured on the exposed rock surrounding Leverett Glacier, using a distancemeter (AGA 220 Geodimeter) and theodolite (Wild T2). Photogrammetric measurements were carried out on an analytical plotter (Zeiss Planicomp C100). The altitude of points could be photogrammetrically measured with a maximum error of 0.86 m.

The data on the altitude changes of Leverett Glacier presented here are the first in West Greenland that span a time period of nearly 50 years. During the period 1943–68 the rate of altitude change was –0.6 m w.e.a−1. The thickening rate during the period 1968–85 was + 1.2 m w.e.a−1. Thickening continued dining the period 1985–92 at a rate of + 0.4 m w.e.a−1. This recent thickening is significant when compared to year-to-year variation in ablation. Trends in air temperature from the nearby climate station at Kangerlussuaq are consistent with the possibility that observed changes in the altitude of the glacier surface are the result of local changes in meteorological conditions determining ablation rates.