bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model simulation of the effects of climate variability and change on lake ice in central Alaska, USA
Authors: Morris Kim , Jeffries Martin , Duguay Claude 
Published: November 2007

AbstractThe Canadian Lake Ice Model (CLIMo) is used to simulate the effects of climate variability and change on lake ice phenology (freeze-up (FU), break-up (BU), ice-cover duration) and total thickness and composition (snow ice, congelation ice) in central Alaska, USA. The model results suggest that, due to the Pacific Decadal Oscillation shift that occurred in 1976, the ice-cover duration is shorter (4 days) due to earlier BU in spring, and thinner (0.05 m) due to a reduction in the formation of snow ice. Sensitivity tests indicate that air-temperature changes cause the duration change, and snow-depth changes cause the total ice-thickness and composition change. The role of annual and monthly air-temperature and snow-depth changes is examined further in a series of experiments designed to elucidate the possible effects of future climate change. Air temperature is varied in 1˚C increments between –4 and +4˚C, and snow depth is varied in 25% increments between –100% and +100% of the long-term averages for 1952–75 and 1977–2000. The FU and BU dates (ice duration) are most affected by annual air-temperature change. Total ice thickness and composition are most affected by annual and monthly snow-depth change. A key finding is that snow-depth increases cause total ice thickness to increase as a consequence of increased snow-ice formation on top of the ice cover at the expense of congelation-ice formation at the bottom of the ice cover.
Determination of basal hydraulic systems based on subglacial high-pressure pump experiments
Authors: Lappegard Gaute , Kohler Jack 
Published: November 2007

AbstractWe have conducted short-term pump experiments with pump pressures exceeding ice overburden to study the seasonality of the subglacial hydraulic system of Engabreen, Norway. Data were collected from load cells installed flush with the ice–bedrock interface and pressure transducers installed in boreholes leading from bedrock tunnels underneath the glacier to the ice–bedrock interface. The water-pressure recordings, seen in relation with the load-cell record, show the existence of hydraulically connected vs unconnected bed areas. Monitored boreholes have been used to inject water at high pressures. Each experiment led to the growth of a high-pressure water cavity whose spatial extent could be inferred from load-cell and pressure transducer records. Post-pump pressures were low after summer pump tests and close to ice-overburden level after winter pump experiments. We conclude that drainage takes place in a fast-flow, low-pressure, channel-based drainage system during summer, and a low-flow, high-pressure, linked-cavity drainage system during winter.
Calving processes and lake evolution at Miage glacier, Mont Blanc, Italian Alps
Authors: Diolaiuti G. , Kirkbride M.P. , Smiraglia C. , Benn D.I. , D’Agata C. , Nicholson L. 
Published: November 2007

AbstractA marginal ice-contact lake at Miage glacier, Mont Blanc, Italian Alps, has been studied to reconstruct changes in lake area. Historical sources, comprising sketches, maps, photographs and scientific surveys, have been supplemented by recent field surveys. These include surveys of glacier surface velocity (which varied along the glacier tongue from 70 ma–1 in the upper part to about 6 ma–1 close to the snout, consistent with data in the literature, showing that velocity rates have remained constant during the last 40 years), volumetric ice-cliff loss (–92 000±180m3 in 2002–03), lake temperature and bathymetry, and qualitative observation of calving events, crevassing, and meltwater production. Results indicate that the lake has been stable for the last half-century following a period of enlargement due to ice-marginal retreat. The lake hydrology is complex, with possible reversals of englacial water flow causing infrequent emptying episodes. The debris cover on the glacier and ice-cliff surfaces seems to have played an important role in the ice-cliff evolution and the calving phenomena; calving is driven by undercutting at the water-line aided by the opening of water- and debris-filled crevasses in the glacier surface.
Impact of subglacial hydrology on the release of water from temporary storage in an Alpine glacier
Authors: Rutter Nick J. 
Published: November 2007

AbstractPeriods of storage and release of surface runoff that is routed englacially and subglacially are identified from a time series of cumulative water balance between 31 July and 11 September 1999 at Findelengletscher, Switzerland. The influence of subglacial hydrology on water routing within the glacier, and therefore on trends of water storage and release, is determined through comparisons of phase relationships between daily maxima, daily minima and diurnal ranges of borehole water levels, supraglacial runoff and proglacial discharge. Variations of water levels in 21 boreholes in the ablation zone suggest that although subglacial drainage is spatially dynamic, hydrologically efficient tunnel–conduit-style drainage dominates diurnal cycles of water transfer through the glacier. Over longer periods, however, storage and release of subglacially routed water is greatly influenced by the coexistence of, and temporary interconnections between, hydrologically inefficient distributed drainage and the tunnel–conduit network. Water levels in three boreholes indicate that after water storage increases in distributed drainage, hydraulic gradients between the different drainage systems may increase sufficiently to cause connections that initiate release of water when: (1) low maximum daily surface runoff causes low water pressures in the tunnel–conduit system; or (2) reorganization within distributed drainage causes spatially localized increases in water pressure.
The influence of river ice on spring runoff in the Lena river, Siberia
Authors: Ma Xieyao , Yasunari Tetsuzo , Ohata Tetsuo , Fukushima Yoshihiro 
Published: November 2007

AbstractThe Lena river is one of the four largest rivers flowing into the Arctic Ocean. It has a complicated hydrological system that is affected not only by the amount of precipitation but also by the timing of ice break-up. To determine the mechanisms of runoff formation, a numerical analysis based on modeling was carried out for the period 1986–2000. The results show that (1) the timing of flood rise and peak can be modeled at Tabaga, which represents the upper and central portions of the Lena river; (2) river-freeze processes delay the spring, snowmelt-dominated flood by about 23 days; and (3) the difference between the break-up dates at Tabaga and Kirensk has ranged from several days to >2 months, and a maximum value of 69 days was recorded in spring 1998.
Observations of englacial water passages:a fracture-dominated system
Authors: Fountain Andrew G. , Schlichting Robert B. , Jansson Peter , Jacobel Robert W. 
Published: November 2007

AbstractTo test models of the hydraulics and geometry of englacial conduits, 48 holes (3900m of ice) were drilled into Storglaciaren, Sweden, in search of conduits. About 79% of the holes intersected a hydraulically connected englacial feature. A video camera was used to examine the features and measure local water-flow rates. Because of the extremely clear ice that surrounded most features, their geometry could not be discerned. Of the remaining features, 80% (36) were fracture-like, 16%(6) were of complex geometry, and 4%(2) exhibited a conduit-like geometry. The fracture-like features exhibited steep plunges (∼70˚), narrow openings (∼40mm) and slow water-flow speeds (∼10mms–1). We argue that these fracture-like features are indeed englacial fractures of unknown origin. The depth to fractures intersection varied from near the glacier surface to 96% of local ice depth, with a maximum depth of 131 m. Few hydraulically connected fractures exhibited water motion, indicating some preferential flow pathways exist. We found one ‘traditional’ englacial conduit after an intentional search in a field of moulins. These results suggest that englacial water flow is conveyed through a ubiquitous network of fractures and that conduits are relatively rare.
Record of glacier variations during the last glacial in the Turkestan range of the Pamir-Alay, Kyrgyz Republic
Authors: Narama Chiyuki , Okuno Mitsuru 
Published: November 2007

AbstractMoraines in five valleys of the Turkestan range of the Pamir-Alay, Kyrgyz Republic, were analyzed based on their geographical position and elevation, morphology and ecological characteristics. The moraines represent four glacial advances: Turkestan Stage I, during the last glacial; Stage II, during the late Holocene; Stage III, during the Little Ice Age (AD 1400−1900); and Stage IV, during the 20th century. In Turkestan Stage I, the glaciers expanded to about 5−10 km from their present termini during marine isotope stage (MIS) 2. Radiocarbon ages for several soil layers buried in a lateral moraine of the Asan-Usin glacier frontal area indicate that glaciers shrank or stagnated between at least ∼48 and 42 kyr BP, during the warm climate of mid-MIS 3. These findings suggest that the glacier expansion in mid-MIS 3 was relatively small compared to the glacier expansion of MIS 2 during the last glacial.
Spatial and temporal variations of oxygen isotopes in snowpacks and glacial runoff in different types of glacial area in western China
Authors: He Yuanqing , Pang Hongxi , Theakstone W.H. , Zhang Dian , Lu Aigang , Song Bo , Yuan Lingling , Ning Baoying 
Published: November 2007

AbstractIn 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.
Observed degree-day factors and their spatial variation on glaciers in western China
Authors: Zhang Yong , Liu Shiyin , Ding Yongjian 
Published: November 2007

AbstractThe degree-day factor (DDF) is an important parameter for the degree-day model, which is a widely used method for ice- and snowmelt computation. Spatial variations of the DDF greatly affect the accuracy of snow- and ice-melt modelling. This study analyzes the spatial variability of DDFs obtained from observed glaciers in different regions of western China. The results clearly show that the DDF for a single glacier is subject to significant small-scale variations, and the factor for maritime glaciers is higher than that for subcontinental and extremely continental glaciers. In western China the factors increase gradually from northwest to southeast. In general, the regional patterns of DDFs are detectable on the glaciers due to the unique climatic environment and heat budget of the Tibetan Plateau and surrounding regions. Low DDFs can be expected for cold-dry areas, whereas high DDFs can be expected for warm-wet areas in western China. Depending on spatial variation of the characteristics of DDFs and the meteorological data, we can provide gridded degree-day models for non-monitored glaciers to reconstruct gridded historical glacier mass-balance series in western China.
Height dependence of the tendency for reduction in seasonal snow cover in the Himalaya and the Tibetan Plateau region, 1966–2001
Authors: Rikiishi Kunio , Nakasato Haruka 
Published: November 2007

AbstractThe dataset of Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent for the period October 1966-July 2001 is analyzed to examine the height dependence of declining tendencies of seasonal snow cover in the Himalaya and the Tibetan Plateau region (25−45˚ N, 70−110˚E). It is found that the annual mean snow-covered area is decreasing in the Himalaya/Tibet region at a rate of ∼ 1 % a−1, implying that the mean snow-covered area has decreased by one-third from 1966 to 2001. The rate of decrease is largest (1.6%) at the lowest elevations (0−500 m). On the other hand, the length of the snow-cover season is declining at all elevations, with the greatest rate of decline in the 4000−6000 m height range. On the Tibetan Plateau (∼4000−6000 m a.s.l.), the length of the snow-cover season has decreased by 23 days, and the end date for snow cover has advanced by 41 days over this 35 year period. These rates might be somewhat overestimated by the binary definition of snow cover on satellite images. It is likely that the reduction of the snow surface albedo by deposition of Asian dust and anthropogenic aerosols may be at least partly responsible for earlier snowmelt.
Glacier variations in the Naimona’nyi region, western Himalaya, in the last three decades
Authors: Ye Qinghua , Yao Tandong , Kang Shichang , Chen Feng , Wang Jinghua 
Published: November 2007

AbstractThis work quantifies glacier variations in the Naimona’nyi area of the western Himalaya by integrating glacier spatial data from ASTER and the Landsat series of satellite imagery at four different times: 1976, 1990, 1999 and 2003. Comparison of the results from individual images with those from the integrated method indicates that the integrated approach provides a better result. Glacier variations were mapped and analyzed; discrepancies between images could be detected and removed from the integrated data using remap tables in Arc/Info grid both graphically and numerically. Our results show that glaciers in the region both retreated and advanced during the last 28 years; however, retreat dominates. The variation of glaciers in the western Himalayan region is dramatic compared with other regions in high Asia. From 1976 to 2003, glacier area decreased from 84.41 km2 to 77.29 km2. Sequential images show that glacier areas shrank by 0.17, 0.19 and 0.77 km2 a−1, on average, during the periods 1976–90, 1990–99 and 1999–2003, respectively, suggesting that glacier retreat has accelerated.
Seasonal evolution of aerosol stratigraphy in Ürümqi glacier No. 1 percolation zone, eastern Tien Shan, China
Authors: Wang Feiteng , Li Zhongqin , You Xiaoni , Li Chuanjin , Li Huilin , Li Xiangying , Zhu Yuman 
Published: November 2007

AbstractThe 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.
Modeling the response of glacier systems to climate warming in China
Authors: Xie Zi-Chu , Wang Xin , Feng Qing-Hua , Kang Er’si , Liu Chao-Hai , Li Qiao-Yuan 
Published: November 2007

AbstractA glacier system is regarded as the ensemble of many glaciers sharing the same region, influenced by a similar climate and organized by certain intrinsic laws. It can be either ‘sensitive’ or ‘steady’. On the basis of the structure of the glacier system and the nature of the equilibrium-line altitudes at the steady state, functional models of a glacier system responding to climate warming were established, using the Kotlyakov–Krenke equation relating annual glacier ablation and mean summer temperature and the glacier system’s median size. The modeling results under the climatic scenarios with a rate of temperature increase of 0.01, 0.03 and 0.05 K a-1 indicate that by the end of this century the glacial area of China will be reduced by –14%, –40%and –60% respectively. However, model results show distinct differences between the sensitive glacier system and the steady glacier system.
Elemental and organic carbon measurements with a two-step heating-gas chromatography system in snow samples from the Tibetan Plateau
Authors: Xu Baiqing , Yao Tandong , Liu Xianqin , Wang Ninglian 
Published: November 2007

AbstractIn 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.
Recent changes of atmospheric heavy metals in a high-elevation ice core from Muztagh Ata, east Pamirs: initial results
Authors: Li Yuefang , Yao Tandong , Wang Ninglian , Li Zhen , Tian Lide , Xu Baiqing , Wu Guangjian 
Published: November 2007

AbstractAl, 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.
Recent changes of glacier coverage in the western Terskey-Alatoo range, Kyrgyz Republic, using Corona and Landsat
Authors: Narama Chiyuki , Shimamura Yuichi , Nakayama Daichi , Abdrakhmatov Kanatbek 
Published: November 2007

AbstractCorona 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.
Influence of air temperature on a glacier’s active-layer temperature
Authors: Zagorodnov V. , Nagornov O. , Thompson L.G. 
Published: November 2007

AbstractSeasonal temperature variations occur in the glacier layer about 15–20 m below the surface, while at greater depths the glacier temperature depends on the long-term surface conditions. It is generally accepted that for glaciers without surface melting the temperature at 10 m depth (T10) is close to the mean annual air temperature at standard screen level (Ta), i.e. T10 =Ta. We found that this relationship is not valid for Ta above –17˚C and below –55˚C. The goal of our investigation is to find a better temperature transfer function (TTF) between Ta and temperature at the boundary of the active layer in accumulation areas of polar and tropical glaciers. Low-precision T10 temperatures from boreholes, obtained at 41 sites, are compared with air temperatures (Ta) measured in the vicinity of these sites for at least a 1 year period. We determine that when Ta falls into the temperature range –60 to –7˚C, empirical values can be approximated as T10 = 1:2Ta + 6:7. Analysis of these data suggests that high T10 occurs in the areas of the glacier that collect meltwater.