bluuebunny/crossref_metadata_2025_split huggingface dataset:
The chemical composition of runoff from Canada Glacier, Antarctica: implications for glacier hydrology duringa cool summer
Authors: Tranter Martyn , Fountain Andrew G. , Lyons W. Berry , Nylen Thomas H. , Welch Kathy A. 
Published: November 2007

AbstractVariations in the chemical composition of subsurface runoff within Canada Glacier, Antarctica, are used to identify the main source waters, which are vertical surfaces, and melt from solar-heated debris within channels, cryoconite holes and pools. The main flow paths are subsurface connections between cryoconite holes, pools and riffles. The latter may become partially disconnected during hard freeze. The chemical composition of runoff at the outlet of Canada Glacier during January 2000 was dominated by Ca2+, HCO3– and sea salt (Na+ and Cl–), and became depleted in sea-salt and non-sea-salt (*) SO42– as the subsurface drainage system in a frozen pool-and-riffle system was flushed and the melting ice surface became depleted of overwinter dry deposited salts. Only during 2 days of hard freeze did sea salt and *SO42– increase in concentration together. Otherwise, sea salt and *SO42– declined while *Ca2+ and HCO3– increased. The latter ions are derived from the chemical weathering of sediment in frozen-topped pools, channels and cryoconite holes. It is inferred that the hydrochemical processes which occur in the vestigial, subsurface drainage system are the elution of ions from ice melt, dilution of these ions downstream by ice melt from vertical surfaces and the dissolution of dust, in subsurface pools, channels and/or cryoconite holes.
Conditions for the reversal of ice/air surface slope on ice streams and shelves: a model study
Authors: Dupont Todd K. , Alley Richard B. 
Published: November 2007

AbstractReversals in the ice/air surface slope are important in geomorphic and glaciological contexts, thus motivating consideration of the conditions under which they form. Surface slope reversals are seen in numerous places, such as ice rumples on ice shelves, as surficial lakes, and at the down-glacier end of Vostok lake, Antarctica. Such slope reversals can reduce or reverse the subglacial hydrological gradient, thereby rerouting subglacial water transport and possibly leading to the creation of subglacial lakes. Supraglacial lakes produced by slope reversals in ablation zones may aid in driving water-filled cracks that allow surface water access to the bed. Surface slope reversals, in the absence of a concomitant reversal in ice flow, indicate a local violation of the so-called ‘shallow-ice’ approximation, and in this circumstance the longitudinal deviatoric stress becomes critical in the stress equilibrium. Using a simple numerical model, we have explored the conditions under which surface slope reversals form for certain simple scenarios. The results indicate that ice which initially possesses a normal slope will tend toward a reversed slope if the ice is thinned, the bed is strengthened or the downstream buttressing is increased.
Diurnal water-pressure fluctuations: timing and pattern of termination below Bench Glacier, Alaska, USA
Authors: Fudge T. J. , Harper Joel T. , Humphrey Neil F. , Pfeffer W. Tad 
Published: November 2007

AbstractObservations from basal water-pressure sensors along the length of Bench Glacier, Alaska, USA, show that diurnal fluctuations of water pressure are seasonal and restricted to summer. Most notable about these fluctuations is their disappearance in the late summer and early autumn, long before the seasonal end of diurnal meltwater input. Here we present data documenting the end of diurnal water-pressure fluctuations during the 2002 and 2003 melt seasons. The end of diurnal fluctuations occurred abruptly in multiple boreholes spaced meters to kilometers apart. There was no obvious spatial progression of termination events, and a clear correlation with meteorological forcing or discharge in the outlet stream was not apparent. After diurnal pressure fluctuations ended, basal water pressure returned to a high, generally steady, value either in an irregular pattern or by a distinct increase. This high water pressure was interrupted by episodic, acyclic events throughout the autumn before becoming stable and high in winter.
Lake ice growth and decay in central Alaska, USA: observations and computer simulations compared
Authors: Jeffries Martin O. , Morris Kim , Duguay Claude R. 
Published: November 2007

AbstractThe Canadian Lake Ice Model (CLIMo), a one-dimensional, thermodynamic model with unsteady heat conduction and penetrating solar radiation, is used to simulate ice growth and decay on shallow ponds in and near Fairbanks, central Alaska, USA. Simulations are compared with observations of ice thickness and composition (snow ice, congelation ice), freeze-up, break-up and duration. Simulations run using US National Weather Service meteorological data as input variables do not agree well with ice-thickness measurements. The simulations improve significantly when the model is run with more representative, locally measured data for air temperature and depth of snow on the ice. The causes of some discrepancies between simulations and observations are discussed and some suggestions for model improvements are made.
Trends in spring snowpack over a half-century of climate warming in California, USA
Authors: Howat Ian M. , Tulaczyk Slawek 
Published: November 2007

AbstractLinear trends in 1 April snow water equivalent (SWE) in California, USA, are determined from a dense network of observations over the period 1950–2002. These trends are compared to concurrent time series of precipitation and temperature and Pacific Ocean climate indices. We find increased winter temperatures have accompanied both decreasing and increasing SWE trends, resulting in a weak overall negative trend in spring SWE. The spatial distribution of SWE trend is dependent on both latitude and elevation. Increases in both precipitation and temperature have led to increases in SWE at high elevations in southern Sierra Nevada and decreases at lower elevations. Increased temperature and decreased precipitation are associated with SWE loss in northern California. Trends in SWE can partially be attributed to shifts in Pacific Ocean climate indices.
Temperature variations in lake ice in central Alaska, USA
Authors: Gould Marc , Jeffries Martin 
Published: November 2007

AbstractIn winter 2002/03 and 2003/04, thermistors were installed in the ice on two shallow ponds in central Alaska, USA, in order to obtain data on ice temperatures and their response to increasing and decreasing air temperatures, and flooding and snow-ice formation. Snow depth and density, and ice thickness were also measured in order to understand how they affected and were affected by ice temperature variability. The lowest ice temperature (–15.5˚C) and steepest temperature gradient (–39.8˚Cm–1) occurred during a 9week period in autumn 2002/03 when there was no snow on the ice. With snow on the ice, temperature gradients were more typically in the range –20 to –5˚Cm–1. Average ice temperatures were lower during the warmer, first winter, and higher during the cooler, second winter because of differences in the depth and duration of the snow cover. Isothermal ice near the freezing point resulted from flooding and snow-ice formation, and brief episodes of warm weather with freezing rain. Under these circumstances, congelation-ice growth at the bottom of the ice cover was interrupted, even reversed. It is suggested that the patterns in temperatures brought about by the snow-ice formation and rain events may become more prevalent due to the increase in frequency of these events in central Alaska if temperature and precipitation change as predicted by Arctic climate models.
Stable isotopes and electrical conductivity as keys to understanding water pathways and storage in South Cascade Glacier, Washington, USA
Authors: Vaughn Bruce H. , Fountain Andrew G. 
Published: November 2007

AbstractMeasurements of electrical conductivity (EC) and deuterium isotopes in glacier run-off provide the basis for the application of simple mixing models that separate hydrographs into four constitutive components: subglacial, englacial, melt and rainfall-derived waters. Volumes of these components are determined from the models in two adjacent drainage basins within the glacier. Peak arrival times of both EC and isotopes during discharge events on short-term time-scales (days to weeks) differ in each terminus stream by as much as a factor of 5. Englacial water storage determined from the model varied greatly (98%) between neighboring basins within the glacier. Estimates of basal water volumes expressed as a layer thickness at the bed of the glacier differed by 50% (5 and 10mm each). Other results suggest that a greater percentage of water is stored at the glacier bed during rainfall events, and exceeds the storage capacity found within the seasonal snow and englacial zones combined.
Mass balance and recession of Ürümqi glacier No. 1, Tien Shan, China, over the last 45 years
Authors: Jing Zhefan , Jiao Keqin , Yao Tandong , Wang Ninglian , Li Zhongqin 
Published: November 2007

AbstractObservations 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.
Ice ablation and meteorological conditions on the debris-covered area of Baltoro glacier, Karakoram, Pakistan
Authors: Mihalcea Claudia , Mayer Christoph , Diolaiuti Guglielmina , Lambrecht Astrid , Smiraglia Claudio , Tartari Gianni 
Published: November 2007

AbstractDuring the recent Italian expedition ‘K2 2004 – 50 years later’ (June–July 2004) on Baltoro glacier, Karakoram, Pakistan, glaciological field experiments were carried out on the debris-covered area of this high-elevation glacier. The aim was to investigate the ice ablation and its relations with debris thermal properties and meteorological conditions. Ablation measurements along the glacier up to about 5000 m and within a dedicated test field were combined with meteorological data from two automatic weather stations located at Urdukas (4022 ma.s.l.) and at K2 Base Camp (5033 m a.s.l.). In addition, temperature measurements of the debris cover at different depth levels along the glacier allowed the calculation of debris surface temperature and of the debris thermal resistance (R). Using the air temperature, the local mean lapse rate (0.0075˚C m−1) and the measured ablation, the degree-day factors (K) at different locations on the glacier were calculated. The ice ablation rates were related to debris thickness and elevation. They are typically on the order of 4 cm d−1 during the observation period. However, it was found that the surface topography (slope, aspect) has an influence on the total ablation similar to that of the debris thickness. Thermal resistance of the debris cover and its distribution over the glacier were estimated. Finally, a best-guess estimate of the total meltwater production was calculated from available climate data.
Accumulation variability and mass budgets of the Lambert Glacier-Amery Ice Shelf system, East Antarctica, at high elevations
Authors: Wen Jiahong , Jezek Kenneth C. , Monaghan Andrew J. , Sun Bo , Ren Jiawen , Huybrechts Philippe 
Published: November 2007

AbstractThe temporal and spatial variability of the annual accumulation rate and the mass budgets of five sub-basins of the Lambert Glacier-Amery Ice Shelf system (LAS), East Antarctica, at high elevations are assessed using a variety of datasets derived from field measurements and modeling. The annual temporal variations of the accumulation rate for four cores from the west and east sides of the LAS are around ±34%. Decadal fluctuation of the accumulation from the DT001 firn core drops to ±10%, and the 30 year fluctuation to ±5%, which is assumed to contain the information about the regional and long-term trend in accumulation. The 15-point running mean of the annual accumulation rate derived from stake measurements can remove most of the high-frequency spatial variation so as to better represent the local accumulation. Model simulations show that the spatial variability of erosion/ deposition of snow by the wind has a noticeable impact on the surface mass balance at the higher parts of the LAS. Mass-budget estimates at high-elevation sub-basins of the LAS suggest drainage 9 has a negative imbalance of −0.7 ± 0.4 Gta-1, Lambert and Mellor Glaciers have a positive imbalance of 3.9 ± 2.1 and 2.1 ±2.4 Gta-1 respectively, and Fisher Glacier and drainage 11 are approximately in balance. The higher-elevation region as a whole has a positive mass imbalance of 4.4 ± 6.3 Gta-1, which is consistent with the most recent radar altimetry assessment that shows an overall thickening over this region.
Response of meltwater runoff to air-temperature fluctuations on Keqikaer glacier, south slope of Tuomuer mountain, western China
Authors: Xie Changwei , Ding Yongjian , Liu Shiyin , Chen Caiping 
Published: November 2007

AbstractFlow records of meltwater runoff provide information about the movement of water through the ice and about glacial ablation. This study indicates that the lag time required for a maximum correlation between daily discharge and air temperature, and the sensitivity of meltwater response to air temperature, changes during the ablation period for different proportions of the base flow. To examine how glaciers respond to climatic changes and the hydrological characteristics of the large glaciers in the Tuomuer mountain area, western China, observations have been undertaken in this region since June 2003. By means of correlation and cross-spectral analysis, the relationship between air temperature and meltwater runoff in different months of the ablation period (May–September) on Keqikaer glacier in 2004 has been evaluated. Data have been selected from the 1st to the 30th for every month, and the calculated hourly discharges of the meltwater runoff for each day were utilized. From these data we conclude that for Keqikaer glacier the meltwater runoff has a greater sensitivity to air temperature in May, July and August than in June and September; however, the lag time is shorter in June, July and August than it is in May and September.
Use of ice cores from glaciers with melting for reconstructing mean summer temperature variations
Authors: Nakazawa Fumio , Fujita Koji 
Published: November 2007

AbstractThis 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.
Spatial patterns and seasonal variation of snowpack sulphate isotopes of the Prince of Wales Icefield, Ellesmere Island, Canada
Authors: Wasiuta Vivian , Norman Ann-Lise , Marshall Shawn 
Published: November 2007

AbstractIon-chemistry and sulphate-isotope values for snow samples from the Prince of Wales Icefield, Ellesmere Island, Canada, show distinct seasonal trends and spatial patterns. Sixteen surface snow samples from two transects, and 30 samples from five depth profiles, representing fall 2003 to spring 2004 accumulation, have been analyzed. Surface snow samples show decreasing SO42– and Na+ concentrations along with decreasing δ34S values with distance inland and increased elevation. These trends follow an expected pattern of decreasing sea-salt aerosol impact with greater vertical and horizontal distance from sea-water sources. Depth-profile total sulphate and non-sea-salt sulphate increase in concentration with height in the snowpack, and these results, combined with δ34S values that are more positive in fall snow, are consistent with increased amounts of anthropogenic sulphate in surface spring snow. Sulphate apportionment was performed on surface snow assuming an isotopically light sulphate source (anthropogenic plus volcanic) mixed with isotopically heavier sulphate from dimethylsulphide (DMS) oxidation and sea water. Isotopically light sulphate in surface snow was apparent at all elevations at a reasonably uniform concentration. DMS sulphate, however, decreased exponentially with altitude, reflecting an ocean level source with oxidation occurring during transport and deposition. The significance to multi-year deposition studies is that sulphate from DMS oxidation may be related to sea-ice conditions in the region.
Application of a degree-day model for the determination of contributions to glacier meltwater and runoff near Keqicar Baqi glacier, southwestern Tien Shan
Authors: Zhang Yong , Liu Shiyin , Xie Changwei , Ding Yongjian 
Published: November 2007

AbstractA so-called ‘warm and wet transition’ of climate has occurred in the arid part of northwestern China since the late 1980s. A result of this climatic transition is an increase in runoff in Xinjiang and neighboring regions. In a warming and wetting change-of-climate scenario, we attempt to evaluate the impact of glacier meltwater and precipitation on the increase in outlet discharge (runoff) from Keqicar Baqi glacier, southwestern Tien Shan, China. In our research we have applied a degree-day model which is one of the most widely used methods of ice- and snowmelt computations for a multitude of purposes such as hydrological modeling, ice-dynamic modeling and climate sensitivity studies. It is concluded that under the warming and wetting scenario, the primary supply for the runoff in this catchment is glacier meltwater, with precipitation being the dominant secondary source; 84% and 8% of total runoff, respectively.
Strong negative correlation between dust event frequency and air temperature over the northern Tibetan Plateau reflected by the Malan ice-core record
Authors: Wang Ninglian , Yao Tandong , Thompson L.G. , Davis M.E. 
Published: November 2007

AbstractIn this paper, the ratio of dust layer thickness to ice thickness, i.e. the dust ratio, is used as a proxy for dust event frequency in the Malan ice core from the northern Tibetan Plateau. We reconstructed a ∼900 year record that reveals that the 1770s–1880s was a prolonged period of high dust ratios, which indicates that dust events occurred frequently from the late 18th century through the 19th century. Statistical analysis of the variations in the dust ratios and δ18O (which is a good proxy for air temperature) in the Malan ice core shows that there is a strong negative correlation between them. This suggests that dust events occur more frequently in cold periods than in warm periods.
Glacier changes during the past century in the Gangrigabu mountains, southeast Qinghai–Xizang (Tibetan) Plateau, China
Authors: Liu Shiyin , Shangguan Donghui , Ding Yongjian , Han Haidong , Xie Changwei , Zhang Yong , Li Jing , Wang Jian , Li Gang 
Published: November 2007

AbstractThe 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.
Holocene climate variability archived in the Puruogangri ice cap on the central Tibetan Plateau
Authors: Thompson Lonnie G. , Tandong Yao , Davis Mary E. , Mosley-Thompson Ellen , Mashiotta Tracy A. , Lin Ping-Nan , Mikhalenko Vladimir N. , Zagorodnov Victor S. 
Published: November 2007

AbstractTwo ice cores (118.4 and 214.7 m in length) were collected in 2000 from the Puruogangri ice cap in the center of the Tibetan Plateau (TP) in a joint US-Chinese collaborative project. These cores yield paleoclimatic and environmental records extending through the Middle Holocene, and complement previous ice-core histories from the Dunde and Guliya ice caps in northeast and northwest Tibet, respectively, and Dasuopu glacier in the Himalaya. The high-resolution Puruogangri climate record since AD 1600 details regional temperature and moisture variability. The post-1920 period is characterized by above-average annual net balance, contemporaneous with the greatest 18O enrichment of the last 400 years, consistent with the isotopically inferred warming observed in other TP ice-core records. On longer timescales the aerosol history reveals large and abrupt events, one of which is dated ∼4.7 kyr BP and occurs close to the time of a drought that extended throughout the tropics and may have been associated with centuries-long weakening of the Asian/Indian/African monsoon system. The Puruogangri climate history, combined with the other TP ice-core records, has the potential to provide valuable information on variations in the strength of the monsoon across the TP during the Holocene.