Ice-core and snow samples collected on Belukha glacier, Russian Altai mountains, were analyzed for n-alkanes by gas chromatography. On the basis of the total concentrations (T-HCs), carbon preference index (CPI) values and the plant wax contributions (WaxCn), it is suggested that mountain glaciers on the Asian continent received higher loading of n-alkanes from natural and anthropogenic sources than the Greenland ice sheet. It appears that the loading and variation of n-alkanes on glaciers in the Altai are approximately the same as those of the mountain in general, because the concentrations, CPI values and WaxCn percentages of n-alkanes in Sofiyskiy glacier, also in the Russian Altai, are at the same levels as or slightly greater than those in ice-core and snow samples from Belukha glacier. It seems that the n-alkanes on Belukha glacier are derived mainly from higher plant wax and petroleum exhaust other than from diesel engines. Vertical profiles of T-HCs and CPI values of n-alkanes show that the non-WaxCn portions and T-HCs have recently increased with a decrease in CPI values on Belukha glacier. A similar trend of n-alkanes was reported for Sofiyskiy glacier, indicating that the influence of human activities has gradually increased around the Altai.

Snow algae in a shallow ice core (6.98 m long) from Yala glacier in the Langtang region of Nepal were examined for potential use as environmental markers in ice-core analysis. The ice core, taken at 5350m a.s.l. in 1994, was estimated to contain 11 annual layers from 1984 to 1994 from the profile of algal biomass. Algal biomass in each annual layer was noted to be correlated with air temperature, and the following two environmental indices which were calculated from air temperature and precipitation at Kyangjing (3920m a.s.l.), the village nearest to Yala glacier: estimated mean snow-cover thickness (MST) and estimated summer mass balance (SMB). Both parameters reflect snow-cover thickness on algal layers, which would be a major determinant of the light available for algal growth on the glacier. Snow algal biomass in the ice core appears to be a good environmental marker for indicating air temperature and accumulation during summer, which is important for understanding the mass balance of summer-accumulation-type glaciers in this region.

Al, Mn, Rb, Sr, Ba, Cs, Bi and Sb were measured at various depth intervals of a 41.6 m firn/ ice core drilled at an elevation of 7010 m near the top of Muztagh Ata glacier, east Pamirs (38˚17’ N, 75˚06’ E), central Asia. These data, spanning the mid-1950s to 2000, were obtained by analyzing 101 sections using a sector-field double-focusing inductively coupled plasma mass spectrometer (ICP-MS) instrument. This study provides the first time series for these metals from central Asia. Concentrations are 11.7–329 ng mL−1 for Al, 0.33–42.7 ng mL−1 for Mn, 0.42–17.8 ng mL−1 for Sr, 0.04–1.4 ng mL−1 for Rb, 0.18–10.4 ng mL−1 for Ba, 2–167 pg mL−1 for Cs, 2–51 pg mL−1 for Sb and 1–31 pg mL−1 for Bi. Large variations in metal concentrations were found during the study period. Pronounced increases in concentrations were observed for Sb and Bi from the mid-1960s to the beginning of the 1990s, suggesting increased anthropogenic sources of Sb and Bi in central Asia during the same period. However, the decrease of Sb and Bi concentrations during the mid- to late 1990s reflects a reduction in anthropogenic activities in central Asia.

The bacterial DNA structures at different depths in the Puruogangri (Tibetan Plateau) ice core (83.45m) were investigated by the denaturing gradient gel electrophoresis (DGGE) DNA fingerprinting technique. DGGE profiles indicated that the bacterial species diversity in glacial ice is high, and indigenous species represented by common bands in all samples may grow on the glacial surface. Bacterial diversity, as estimated by Shannon indices (mean 2.91; SD 0.25; n = 13), was comparable to that of soil habitats and had a positive correlation with Ca2+ concentration (R = 0.71; P< 0.01), a good proxy of dust. This suggested that the soil ecosystem was the main source of bacteria in this glacier. The low similarity indices (0–43%) were found between the ice-core samples, which corresponded to the episodic deposition under defined climatic conditions and low activity of microorganisms in glacial ice. The profiles of bacterial species composition in glacial ice may be a bio-indicator of climatic changes or dating.

This study examines a new method for reconstructing mean summer temperature variations by using an ice core from a wet-snow zone on a summer-accumulation-type glacier. In July 2001, a 25.1 m deep ice core was recovered from the accumulation area of Sofiyskiy glacier (49°47’ N, 87°43’ E; 3435m a.s.l.), located in the southern Chuyskiy range of the Russian Altai mountains, and a 4.5 m deep pit was excavated about 5 0m northwest of the drill site. The observation site has a positive balance even during summer when melting occurs. The summer balance for each year from 1990 to 2000 was estimated from Pinaceae and Artemisia pollen peaks in these samples. Pinaceae pollen marks spring, whereas Artemisia pollen marks autumn. Moreover, meltwater intrusion did not reach the previous year’s accumulation. Thus, the ice between these pollen peaks in the same year was used to estimate a summer balance. The reconstructed summer balance variations were negatively correlated with mean summer temperature variations (r = –0.72, P< 0.05). This study shows that, for summer-accumulation-type glaciers such as Sofiyskiy glacier, the most important climate factor controlling the glacier’s surface mass balance is mean summer temperature. Therefore, the summer layer thickness in an ice core can be used as a proxy for reconstructing mean summer temperature variations.

Stable oxygen isotope ratios (δ18O) of three shallow ice cores (extending back to 1963) from Urümqi glacier No. 1 at the headwater of Urümqi river, Tien Shan, northwest China, were used to test the relationship between δ18O and contemporaneous surface air temperature (Ta). The ice cores were dated using the seasonal stable-isotopic signals, and seven insoluble particulate β-activity horizons associated with known nuclear tests. Although a strong positive relationship exists between δ18O in precipitation and Ta at our study site, this relationship is not preserved between the annually averaged ice-core δ18O records and the local temperature due to post-depositional modification. These results indicate that the processes forming the ice-core chemical records in areas of high melt must be understood before the δ18O record can be confidently interpreted as a climatic indicator.

Three ice cores were recovered on or near Mount Logan, Yukon, Canada, at 3017, 4135 and 5340 ma.s.l. in 2002. Prior to ice-core drilling, we collected snow-pit and shallow core samples from Mount Logan in 2001 to study seasonal and spatial variations of snow chemistry. We dug snow pits at six sites between 2420 and 5340 m a.s.l. before the beginning of the melt season, with the exception of a pit at 3180 m a.s.l., where the melt season had just started but had affected only the near-surface stratigraphy. Three of the pits were extended deeper with a shallow core. The snow-pit and core samples were analyzed for ion chemistry and δ18O. A series of depth profiles of ions and δ18O shows spatial variations, though characteristic peaks can usually be traced across all the profiles. Concentrations and deposition fluxes of Na+ and Cl−, which are mainly of sea-salt origin, decrease with altitude. On the other hand, deposition fluxes of NO3−, SO42–, Ca2+ and NH4+ show a weak positive relationship with elevation below the summit plateau. Stable isotopes (δ18O) decrease with altitude, with a distinctive jump between 3200 and 4500 m a.s.l., as was reported previously. Stable isotopes (δ18O), Cl−, CH3SO3− (MSA), Na+ and Ca2+ show clear seasonal variations, which would enable us to date the cores by annual-layer counting.

The present research focuses on glacier changes in the southeast of the Qinghai–Xizang (Tibetan) Plateau, where most of the temperate glaciers in China are located. Our results show that the 102 measured glaciers in the region have all retreated between 1915 and 1980, with total area and volume decreases of 47.9 km2 and 6.95 km3, respectively. The extrapolated mass loss of all glaciers in the Gangrigabu mountains amounted to 27 km3, 9.8% of the ice mass in 1915. Between 1980 and 2001, glaciers in the region have also experienced a general retreat; however, up to 40% of the glaciers were advancing. Our analysis demonstrates that precipitation in the studied area has increased substantially since the mid-1980s. This precipitation increase is likely to bring about a positive mass balance for glaciers in the region, so that the retreat of retreating glaciers might slow down or even turn into advance. Considering the sensitivity of the temperate glaciers in the region and the uncertainty in climate projections, more attention must be paid to glacier changes in the southeast Tibetan Plateau region.

As a consequence of ongoing atmospheric temperature rise, tropical glaciers belong to the unique and threatened ecosystems on Earth, as defined by the Intergovernmental Panel on Climate Change (Houghton and others, 2001). Worldwide glacier monitoring, especially as part of the Global Climate Observing System (GCOS), includes the systematic collection of data on such perennial surface ice masses. Several peaks in the sierras of Colombia have lost their glacier cover during recent decades. Today, high-altitude glaciers still exist in Sierra Nevada de Santa Marta, in Sierra Nevada del Cocuy and on the volcanoes of Nevados del Ruiz, de Santa Isabel, del Tolima and del Huila. Comparison of reconstructions of maximum glacier area extent during the Little Ice Age with more recent information from aerial photographs and satellite images clearly documents a fast-shrinking tendency and potential disappearance of the remaining glaciers within the next few decades. In the past 50 years, Colombian glaciers have lost 5 0% or more of their area. Glacier shrinkage has continued to be strong in the last 15 years, with a loss of 10−50% of the glacier area. The relationship between fast glacier retreat and local, regional and global climate change is now being investigated. Preliminary analyses indicate that the temperature rise of roughly 1°C in the last 30 years recorded at high-altitude meteorological stations exerts a primary control on glacier retreat. The investigations on the Colombian glaciers thus corroborate earlier findings concerning the high sensitivity of glaciers in the wet inner tropics to temperature rise. To improve understanding of fast glacier retreat in Colombia, a modern monitoring network has been established according to the multilevel strategy of the Global Terrestrial Network for Glaciers (GTN-G) within GCOS. The observations are also contributions to continued assessments of hazards from the glacier-covered volcanoes and to integrated global change research in mountain biosphere reserves.

This research presents a precise evaluation of the recession of Akshiirak and Ala Archa glaciers, Tien Shan, central Asia, based on data of geodetic surveys from 1861–69, aerial photographs from 1943, 1963, 1977 and 1981, 1:25000 scale topographic maps and SRTM and ASTER data from 2000–03. The Akshiirak glacierized massif in the central Tien Shan contains 178 glaciers covering 371.6 km2, and the Ala Archa glacier basin in the northern Tien Shan contains 48 glaciers covering 36.31 km2. The Tien Shan glaciers retreated as much as 3 km from the 1860s to 2003. Area shrinkage of Akshiirak and Ala Archa was 4.2% and 5.1%, respectively, from 1943 to 1977, and 8.7% and 10.6%, respectively, from 1977 to 2003. The volume of the Akshiirak glaciers was reduced by 3.566 km3 from 1943 to 1977 and 6.145 km3 from 1977 to 2000. The total reduction of the Tien Shan glaciers is 14.2% during the last 60 years (1943–2003). The northern and central Tien Shan have not experienced a significant precipitation increase during the last 100 years, but they have experienced an increase in summer air temperatures, especially observable since the 1970s, which accelerated the recession of the Tien Shan glaciers.

Observations of Ürümqi glacier No. 1 at the headwaters of the Ürümqi river, Tien Shan, show remarkable changes between 1959 and 2003. The cumulative mass balance of the glacier is –10 032 mm, equivalent to 11.1 m of glacier ice, or 20% of the glacier volume, showing particular sensitivity to temperature change. The speed of glacier flow has gradually declined, especially since the 1980s. From 1980 to 2003, the flow speed of the east and west branches of the glacier decreased by about 21% and 43%, respectively. The glacier continuously retreated from 1962 to 2003. Its length has decreased by about 180 m (7.5%) and its area has diminished by 0.23 km2 (11.8%). Analyses show that summer precipitation is negatively correlated with mass balance and positively associated with runoff. These relationships are reasonable, as higher precipitation leads to higher runoff and lower glacier melt. On the other hand, summer temperature is negatively correlated with mass balance and positively associated with runoff, as higher temperatures lead to higher glacier melt and thus higher runoff, with summer temperatures controlling mass-balance variation. Over the past 45 years the negative mass balance, caused by higher ablation than accumulation, is associated with precipitation increase and temperature warming over the study area.

Glacier variation is one of many indicators of climate change. Repeat measurements of the glacier terminus positions for selected glaciers in the central Himalaya document that they have been in a state of continuous retreat over the past few decades. Since the 1960s the average retreat rate on the north slope of Qomolangma (Mount Everest) is 5.5–9.5ma-1 and on Xixiabangma it is 4.0–5.2ma-1. Many glaciers on the south slope of the central Himalaya have been in retreat, and recently their retreat rate has accelerated. Ice-core studies show that the annual accumulation on these glaciers has fluctuated, but over the last century it has declined. It decreased rapidly in the 1960s and has remained consistently below the long-term mean thereafter. Meteorological station records indicate that the annual mean temperature in the region has slowly increased, particularly during the summer months. The strongest warming has occurred in the last 30 years. These data suggest that the current glacier retreat is due to the combined effect of reduced precipitation and warmer temperatures, and, if these conditions continue, the glaciers in the region will continue to shrink.

Corona images from 1971 and a Landsat image from 2002 are used to assess glacier variations in the last 30 years in the western Terskey-Alatoo range (a part of the Tien Shan), in the northeast of the Kyrgyz Republic. The glaciers have shrunk during this period. The 269 mountain glaciers measured in the study area had an original combined area of 245 km2, which has decreased 18.4 km2, representing a loss of 8% of the original glacier coverage in 1971. Individual glaciers covering <1km2 account for 28% of the combined glacial coverage, but loss from these small glaciers represents 38% of the total decrease in area. The relative change of area is larger for small-scale glaciers, and its contribution to shrinkage of glacier area is high. This shrinkage has been linked to climate changes as recorded at local stations. Many small-scale glaciers are distributed around Issyk-Kul lake, and rapid glacier reduction is expected in this area in the future.

Samples collected from four snow pits at Eclipse Icefield, Yukon, Canada, were analyzed for stable isotopes and major ions to assess seasonal and spatial variability in snow chemistry. Accumulation since the end of the 2001 summer season over the 0.1 km2 area sampled ranges from 0.77 to 1.16mw.e. Snow-pit stratigraphy and chemical records demonstrate that the low accumulation at pit 3 is due to an under-representation of winter snow accumulation at that site. For all major-ion species, chemical concentrations are independent of snow accumulation rate. Seasonal variations are evident in the major-ion records and can be divided between sea-salt species (Na+, Cl−) that peak in late fall to winter, and dust (Ca2+, Mg2+, K+) and other species (NH4+, NO3−, SO42–, C2O22–) that peak in late spring to summer. The signal common to all four snow pits identified by empirical orthogonal function analysis ranges from 49% of the total variance for Na+ and Cl− to as high as 80% of the total variance for SO42–. There is greater spatial variability in species associated with coarse-mode particles (Na+, Cl−, Ca2+, Mg2+) than in species present mainly in accumulation-mode aerosols (SO42–, NH4+) or in the gas phase (NO3−).

In order to investigate the relationship between atmospheric nitrate and nitrate records in glacial snow and firn, nitrate was investigated in atmospheric aerosol, surface snow and the snow–firn pack on Ürümqi glacier No. 1 , eastern Tien Shan, China, from September 2002 to September 2004. The study found that vertical nitrate stratigraphy in the upper snowpack is formed during the winter by dry deposition and compaction and sublimation of the snowpack. During the summer the snowpack nitrate is redistributed through the percolation of meltwater. Nitrate was found to be highly mobile in the snowpack relative to magnesium.

The processes involved in the evolution of vertical profiles of Mg2+, Ca2+ and microparticle concentrations, as well as their seasonal variation in surface snow, were studied by weekly sampling from September 2003 to September 2004 of a snow pit on Ürümqi glacier No. 1, eastern Tien Shan, China. The development of the microparticle and Mg2+ and Ca2+ stratigraphy in the snow pit is closely related to the physical development of the snow–firn pack. The sampling site is located at 4130 ma.s.l. in the percolation zone of the glacier, and in addition to the effects of sublimation and wind erosion, melting plays a crucial role in both the physical and chemical evolution processes. During the winter, soluble aerosol concentrations in the surface layers are altered slightly by sublimation and wind erosion, and the concentrations are further modified as the wet season begins in late April. In contrast, soluble aerosol stratigraphy in the deeper layers remains relatively unchanged through the winter. In early summer, as melting occurs in the upper part of the snow–firn pack, meltwater carries chemical species to different depths in the underlying snow–firn layers, such that at the end of the ablation season, all of the surface cations might be leached out from the upper layers. In addition, the possible source of calcium and magnesium is discussed in this paper.

To investigate the effects of both non-meltwater and meltwater-related post-depositional processes on chemical species within the snow–firn pack, a research program, the Program for Glacier Processes Investigation, was initiated in July 2002 by the Tien Shan Glaciological Station, Chinese Academy of Sciences. The seasonal variability of the ionic concentrations in surface snow samples and ion elution behavior in the snow–firn pack were assessed from surface samples collected year-round and 1011 samples collected from a snow pit at weekly intervals from September 2003 through September 2004. The results indicate that elevated ionic concentrations in spring and summer result from Asian dust-storm-derived aerosol input and other aerosols entrained in precipitation. Potential sources of these chemical species are explored using correlation and factor analyses. The elution sequence through the snow–firn pack was determined to be SO42– >Ca2+> Na+>NO3− >Cl−>K+> Mg2+ >NH4+. The elution of ions at the sampling site was found to be driven primarily by air temperature and became evident when a diurnal mean temperature of –3.6˚C was attained. At 0.3˚C all of the year-round new ionic input was leached from the snow.

In this study, an optimized two-step heating-gas chromatography system is used to measure elemental carbon (EC) and organic carbon (OC) content in snow and ice, with the ability to quantify the elemental and organic carbon species in a snow or ice sample of 60−80 g. In this system, OC and EC are transformed into CO2 in a stream of oxygen at 340°C and 650°C, respectively. The resulting CO2 is accumulated in two molecular-sieve traps, and then put into a gas chromatograph equipped with a flame ionization detector by heating the traps to 200°C in a helium stream. Background contamination (mainly caused by impurities in the oxygen stream) and accuracy are dominated by the variability of the blank loads on the pre-cleaned filters, which are 0.50 ± 0.04 (1σ) μgC for OC, and 0.38 ± 0.04 (1σ) μgC for EC. The system is suitable for snow and ice sample measurements, with the same precision as shown for the blank tests. EC and OC concentrations have been measured in snow samples collected from different glaciers on the Tibetan Plateau. The results allow quantification for the first time of the different carbonaceous particle contents on the Tibetan Plateau and other regions. The concentrations of EC and OC particles in snow show a clearly decreasing trend from east to west and from north to south on the plateau, excluding the Pamirs region. The highest mean EC content, 79.2 ngg-1, was found in the northeast region, and the lowest, 4.3 ngg-1, was found in the western Himalaya. We note that even slight surface melting results in fresh snow getting dirtier, especially in regions with higher pollution such as seen on a glacier in the Qilian Shan. Here, the EC and OC concentrations in the fresh snow average 6.6 and 87.5 ngg-1, but after 2 days of surface melting they increased to 52.6 and 195.5 ngg-1. This suggests that surface snow melting can reduce snow albedo due to the accumulation of carbonaceous particles.

This study examines precipitation samples collected at the Yushu meteorological station on the eastern Tibetan Plateau from November 2000 to November 2002. Results show that air-temperature effects control δ18O in precipitation in this area. Values of δ18O in precipitation positively correlate with air temperature, especially for monthly averages. Our data also show δ18O values in precipitation positively correlate with dew point and surface pressure in the Yushu region. Similar to other stations (Tuotuohe, Nagqu, Gaize and Shiquanhe) lying in the transition zone between the regions in the south dominated by the monsoon and those in the north dominated by the westerlies, because of the effect of monsoon precipitation, precipitation rates are high, and heavy isotopes are more depleted in summer at the Yushu station. Accordingly, values of δ18O in precipitation correlate more strongly with air temperature and dew point before the monsoon onset and after the monsoon retreat than during the monsoon period. That is, intense monsoon activities weaken the correlations between δ18O and air temperature and dew point. Clearly, dew point, surface pressure and the monsoon intensity contribute to controlling the δ18O values in precipitation at the Yushu station.

In order to improve understanding of spatial and temporal variations of stable isotopes in atmospheric precipitation, snow cover and glacier meltwater in different regions of China, samples were collected for isotopic analysis in four areas: Yulong mountain, Yunnan Himalaya (temperate-glacier area); Samdain Kangsang mountain, Nyainqêntanglha Shan (subpolar-glacier area); the headwater area of the Ürümqi river, Tien Shan (subpolar-glacier area); and Muztag mountain, Pamirs (polar-glacier area). Sampling was undertaken in both summer and winter between 2000 and 2003. The δ18O values show a ‘temperature–altitude effect’ in new winter snow on Yulong mountain, reflecting the condensation and fractionation processes associated with the winter monsoon, but a different, more complex pattern in residual snow deposited during the summer monsoon; this old snow is influenced by the ‘precipitation amount effect’, solar radiation and evaporation, and the water content of the snowpack. The summer precipitation at Samdain Kangsang mountain is associated with the summer monsoon. There is a marked precipitation amount effect during the long passage of the southwest/India monsoon from the distant moisture source to Samdain Kangsang mountain, and the summer precipitation is strongly depleted of the heavy isotope. Above 6000 m, the high radiation flux causes much evaporation from the snow surface. The associated 1 8O enrichment of the snow is reflected in a ‘reverse altitude effect’. The δ18O values in the summer snowpack of the Tien Shan and Muztag mountain decrease with increasing altitude and decreasing air temperature, indicating a temperature–altitude effect. Post-depositional processes cause isotopic changes during the transformation of snow/firn/ice to meltwater; the effects are much stronger at temperate than at polar glaciers. Moreover, changes in the isotopic signal at both temperate and polar glaciers can result from evaporation, sublimation, ablation and drifting.