bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensitivity of Greenland ice sheet simulation to the numerical procedure employed for ice-sheet dynamics
Authors: Saito Fuyuki , Abe-Ouchi Ayako 
Published: November 2007

AbstractThe response of the Greenland ice sheet to global warming is simulated by two different numerical approaches, in order to evaluate the sensitivity of the analysis to the numerical structure employed. It is found that the thickness near the margin differs appreciably in these two simulations under identical conditions of modest warming, primarily due to a significant increase in the warming effect by an elevation–ablation feedback mechanism in one of the simulations. The change in ice-sheet volume differs by as much as a factor of two under strong climate-change forcing, demonstrating the need for care in interpreting the results of such climate-change analysis.
Modelling the impact of superimposed ice on the mass balance of an Arctic glacier under scenarios of future climate change
Authors: Wright Andrew , Wadham Jemma , Siegert Martin , Luckman Adrian , Kohler Jack 
Published: November 2007

AbstractA surface-energy/mass-balance model with an explicit calculation of meltwater refreezing and superimposed ice formation is applied to midre Lovénbreen, Spitsbergen, Svalbard. The model is run with meteorological measurements to represent the present climate, and run with scenarios taken from global climate model predictions based on the IS92a emissions scenario to represent future climates. Model results indicate that superimposed ice accounts for on average 37% of the total net accumulation under present conditions. The model is found to be highly sensitive to changes in the mean annual air temperature and much less sensitive to changes in the total annual precipitation. A 0.5˚C decade–1 temperature increase is predicted to cause an average mass-balance change of –0.43 ma–1, while a 2% decade–1 increase in precipitation will result in only a +0.02 ma–1 change in mass balance. An increase in temperature results in a significant decrease in the size of the accumulation area at midre Lovénbreen and hence a similar decrease in the net volume of superimposed ice. The model predicts, however, that the relative importance of superimposed ice will increase to account for >50% of the total accumulation by 2050. The results show that the refreezing of meltwater and in particular the formation of superimposed ice make an important positive contribution to the mass balance of midre Lovénbreen under present conditions and will play a vital future role in slowing down the response of glacier mass balance to climate change.
Mass balance of glaciers in the Queen Elizabeth Islands, Nunavut, Canada
Authors: Koerner Roy M. 
Published: November 2007

AbstractMass-balance measurements began in the Canadian High Arctic in 1959. This paper considers the >40 years of measurements made since then, principally on two stagnant ice caps (on Meighen and Melville Islands), parts of two ice caps (the northeast section of Agassiz Ice Cap on northern Ellesmere Island and the northwest part of Devon Ice Cap on Devon Island) and two glaciers (White and Baby Glaciers, Axel Heiberg Island). The results show continuing negative balances. All the glaciers and ice caps except Meighen Ice Cap show weak but significant trends with time towards increasingly negative balances. Meighen Ice Cap may owe its lack of a trend to a cooling feedback from the increasingly open Arctic Ocean nearby (Johannessen and others, 1995). Feedback from this ocean has been shown to be the main cause of this ice cap’s growth and persistence at such a low elevation of <300 ma.s.l. (Alt, 1979). There may be a similar feedback in the lower elevations on Sverdrup Glacier which drains the northwest sector of Devon Ice Cap. The ablation rates there have not increased to the same extent as they have at higher elevations on the same glacier. Although evidence from the meteorological stations in the area shows that the eastern Arctic has either been cooling or has shown no change on an annual basis between 1950 and 1998, the same records show that the summers are showing a slight warming (Zhang and others, 2000). The summer warming, although slight (<1.0˚C over 48 years), is the cause of the weak trend to increasingly negative balances. This is because the mass-balance variability is dominated by the year-to-year variations in the summer balance; there is a very low variability, and no trend over time even within sections of the time series, of the winter balance of the various ice caps and glaciers. Repeat laser altimetry of ice caps by NASA for the period 1995–2000 over most of the ice caps in the Canadian Arctic Archipelago (Abdalati and others, 2004) has shown that the ablation zones are thinning while the accumulation zones show either a slight thickening or very little elevation change. Laser altimetry is revealing similar patterns of change in Greenland (Krabill and others, 2000) and Svalbard (Bamber and others, 2004). The thickening of the accumulation zones in the Canadian case may be due to higher accumulation rates, not just between the two years of laser measurements, but over a period substantially longer than the >40 years of ground-based measurements.
Temporal variations in flow velocity at Finsterwalderbreen, a Svalbard surge-type glacier
Authors: Nuttall Anne-Marie , Hodgkins Richard 
Published: November 2007

AbstractInter- and intra-annual velocity variations are well known on alpine glaciers, but their importance for Arctic glaciers has only been recognized more recently. This paper presents flow velocity data from Finsterwalderbreen, a 35 km2 polythermal surge-type glacier in southern Svalbard that is presently ∼100 years into its quiescent phase. Field measurements of glacier surface velocities are available from 1950-52 and 1994-97, and mean velocities for the last decade are estimated for the lower glacier using cables drilled to the glacier bed. These velocities show substantial seasonal variations indicating that basal sliding is an important component of surface velocities and interannual fluctuations of up to 75%, possibly indicating variations in subglacial water storage. Several lines of evidence indicate that this glacier has an extensive subglacial hydrological system, generally considered to be a prerequisite for surge-type glaciers, which is at least partly pressurized. Information on surface morphology from 1898 onwards shows that the glacier has experienced continuous retreat since the last surge in about 1910, and has now retreated ∼1.5 km further back than its previous pre-surge position in 1898. Tracking of moraine loops on terrestrial and aerial photographs acquired over a 100 year period indicates that the surge period of Finsterwalderbreen may be lengthening in response to climate changes.
Seasonal cycles of Antarctic surface energy balance from automatic weather stations
Authors: Van Den Broeke Michiel , Reijmer Carleen , Van As Dirk , Van de Wal Roderik , Oerlemans J. 
Published: November 2007

AbstractWe present the seasonal cycle of the Antarctic surface energy balance (SEB) using 4 years (1998–2001) of automatic weather station (AWS) data. The four AWSs are situated on an ice shelf, in the coastal and inland katabatic wind zone and the interior plateau of Dronning Maud Land. To calculate surface temperature we use a SEB closure assumption for a surface skin layer. Modelled and observed surface have a root-mean-square difference of 1.8 K at the plateau AWS (corresponding to an uncertainty in the SEB of 5Wm–2) and <1 K (3Wm–2) at the other sites. The effect of wind-speed sensor freezing on the calculated SEB is discussed. At all sites the annual mean net radiation is negative and the near-surface air is on average stably stratified. Differences in the seasonal cycle of the SEB are mainly caused by the different wind climates at the AWS sites. In the katabatic wind zone, a combination of clear skies and strong winds forces a large wintertime turbulent transport of sensible heat towards the surface, which in turn enhances the longwave radiative heat loss. On the coastal ice shelf and on the plateau, strong winds are associated with overcast conditions, limiting the radiative heat loss and sensible heat exchange. During the short Antarctic summer, the net radiation becomes slightly positive at all sites. Away from the cold interior, the main compensating heat loss at the surface is sublimation. In the interior, summer temperatures are too low to allow significant sublimation to occur; here, surface heat loss is mainly due to convection.
Sea-spray deposition in Antarctic coastal and plateau areas from ITASE traverses
Authors: Benassai Silvia , Becagli Silvia , Gragnani Roberto , Magand Olivier , Proposito Marco , Fattori Ilaria , Traversi Rita , Udisti Roberto 
Published: November 2007

AbstractSea-salt markers (Na+, Mg2+ and Cl–) were analyzed in recent snow collected at more than 600 sites located in coastal and central areas of East Antarctica (northern Victoria Land–Dome C–Wilkes Land), in order to understand the effect of site remoteness, transport efficiency and depositional and post-depositional processes on the spatial distribution of the primary marine aerosol. Firn-core, snow-pit and 1m integrated superficial snow samples were collected in the framework of the International Trans-Antarctic Scientific Expeditions (ITASE) project during recent Italian Antarctic Campaigns (1992–2002). The sampling sites were mainly distributed along coast–inland traverses (northern Victoria Land– Dome C) and an east–west transect following the 2100m contour line (Wilkes Land). At each site, the snow ionic composition was determined. Here, we discuss the distribution of sea-spray components (Na+, Mg2+ and Cl–) as a function of distance from the sea, altitude and accumulation rate, in order to discover the pulling-down rate, possible fractionating phenomena and alternative sources moving inland from coastal areas. Sea-spray depositional fluxes decrease as a function of distance from the sea and altitude. A two-order-of-magnitude decrease occurs in the first 200km from the sea, corresponding to about 2000ma.s.l. Correlations of Mg2+ and Cl– with Na+ and trends of Mg2+/Na+ and Cl–/Na+ ratios showed that chloride has other sources than sea spray (HCl) and is affected by post-depositional processes. Accumulation rate higher than 80 kgm–2 a–1 preserves the chloride record in the snow. Sea-spray atmospheric scavenging is dominated by wet deposition in coastal and inland sites.
High-resolution ice-core stable-isotopic records from Antarctica: towards interannual climate reconstruction
Authors: Schneider David P. , Steig Eric J. , Van Ommen Tas 
Published: November 2007

AbstractIce-core records are a key resource for reconstructing Antarctic climate. However, a number of physical processes preclude the simple interpretation of ice-core properties such as oxygen isotopic ratios in terms of climate variables like temperature or sea-level pressure. We show that well-dated, sub-annually resolved stable-isotopic records from the United States International Trans-Antarctic Scientific Expedition (US-ITASE) traverses and other sources have a high correlation with local seasonal temperature variation. However, this temporal relationship cannot be simply extended to quantitative interannual resolution reconstructions of site temperature. We suggest that a consistent and important target for ice-core calibrations is a composite of annual mean temperature records from Antarctic weather stations, which covaries strongly with the dominant mode (from principal component analysis) of temperature variability in the Antarctic. Significant correlations with this temperature index are found with individual ice-core records, with a composite of the ice cores, and through a multiple linear regression model with the ice cores as predictors. These results imply that isotopic signals, like the instrumental temperature mode itself, have a strong response to large-scale atmospheric circulation variability, which in the Antarctic region is dominated by the Southern Annular Mode.
Meltwater retention in a transect across the Greenland ice sheet
Authors: Bøggild Carl Egede , Forsberg Rene , Niels REEH  
Published: November 2007

AbstractMeltwater retention by freezing is a highly climate-sensitive term in the mass budget since the cold content is directly controlled by winter climate, which is expected to change most in an anthropogenic-driven climate change. Meltwater released at the surface percolates into dry snow in a pattern with alternating horizontal and vertical water-flow directions, where the processes of pore refreezing (RF) (vertical flow) and superimposed ice (SI) formation (horizontal flow) occur. The flow cannot be forecasted and quantified when water first enters cold, dry snow. However, because the two processes are driven by different physical mechanisms, their potential magnitude can be estimated, which has been done in a transect at 66° N. Results show that SI declines from west to east and inversely correlates with accumulation. From the total retention capacity, theoretical lowest-runoff lines were determined at ∼1400ma.s.l. in the west and ∼1600ma.s.l. in the east. Since the SI potential is high in most places and the warming from SI formation predominately occurs near to the surface, it is argued that winter cooling effectively recharges the cold content of the snow/firn/ice pack, preventing the development of isothermal conditions and subsequent runoff. However, SI formation declines over time, so an extension of the melting season could result in deeper percolation beyond the SI layer.
Impact of fine-dust air burden on the mass balance of a high mountain glacier: a case study of the Chongce ice cap, west Kunlun Shan, China
Authors: Han Jiankang , Nakawo Masayoshi , Goto-Azuma Kumiko , Lu Chao 
Published: November 2007

AbstractThe coherent variations of annual snow accumulation rate and dust deposition over 60 years are recorded in an ice core drilled at 6530 ma.s.l. on the Chongce ice cap, located in the west Kunlun Shan, south of the Taklimakan desert in China. These records were investigated in the context both of the dust transport pathways from the source region and of climatic changes in this arid environment. The factors relating the dust transport from the source to sink area were taken into account to ascertain the integration of these factors on the precipitation-forming process at high elevations. Results indicate that: (1) dust is predominant among aerosols in precipitation at high altitude; (2) the dust aerosol population may be more instrumental than the vapor supply in the formation of precipitation at such altitudes; (3) compared to low-elevation glaciers, snow accumulation on high mountain glaciers seems to be more sensitive to changes in the concentration of air-burden dust particulates, which are closely related to the climatic variations around the desert region; and (4) under the current climate conditions surrounding the desert region, the decreasing trend in snow accumulation, in concert with the decrease in dust deposition that has occurred over the past several decades, might continue. This effect on snow accumulation at high altitudes may explain one of the elements potentially responsible for the longer-term glacial variation, i.e. the glacial retreat that has lasted for decades in central Asia.
Mass-balance characteristics of Ürümqi glacier No. 1, Tien Shan, China
Authors: Han Tianding , Ding Yongjian , Ye Baisheng , Liu Shiyin , Jiao Keqin 
Published: November 2007

AbstractThe temporal and spatial variations of mass balance on different timescales were analyzed to identify their response to climate change using long-term observed mass-balance data covering the period 1959–2002 at Ürümqi glacier No. 1 at the headwaters of the Ürümqi river, Tien Shan, China. The results show that the accumulated glacier mass balance has decreased by 9599 mm w.e., which is equivalent to about 10 m mean thickness reduction. The negative mass balance has been accentuated in recent years, with a mean mass balance during the period 1997–2002 of –739.6 mm a−1. The glacier mass balance shows a clear periodicity, with positive and negative alternations of 7 and 15 years during the past several decades. Annual mass balance shows a significant negative correlation with summer air temperature from June to August. It is influenced more by annual air temperature than by annual precipitation. The temperature increase preceded the precipitation increase as an influence on the mass balance. Furthermore, monthly mass balance shows a negative correlation with monthly air temperature, significant at the 99% confidence level in July and August. Monthly mass balance is negatively correlated with precipitation in May and August at the 95% confidence level, but positively and insignificantly correlated with precipitation in June and July. The negative relationship between mass balance and precipitation might be related to concurrent increases of precipitation and temperature.
The retreat of glaciers in response to recent climate warming in western China
Authors: Ding Yongjian , Liu Shiyin , Li Jing , Shangguan Donghui 
Published: November 2007

AbstractGlaciers in China are primarily located in the Tibetan Plateau (TP) and surrounding high mountains. The Chinese Glacier Inventory indicates that there are 46 377 glaciers in western China. Meteorological records indicate that air temperature in western China has risen by 0.2˚C per decade since 1951, and 1998 was the warmest year; precipitation in the region increased by 5–10% per decade from 1953 to 1997. Using remote-sensing and Geographic Information System methods, we have monitored the changes in >5000 glaciers over the past 50 years. We conclude that >80% of glaciers in western China have retreated, losing 4.5% of their combined areal coverage, although some glaciers have advanced. In addition, regional differences characterize glacier changes over the past few decades. For example, glaciers in the central and northwestern TP were relatively stable, while glaciers in the mountains surrounding the TP experienced extensive wastage. Mass-balance variations for some glaciers show accelerated ice shrinkage in the last two decades.
Climatic and atmospheric circulation pattern variability from ice-core isotope/geochemistry records (Altai, Tien Shan and Tibet)
Authors: Aizen Vladimir B. , Aizen Elena M. , Joswiak Daniel R. , Fujita Koji , Takeuchi Nozomu , Nikitin Stanislav A. 
Published: November 2007

AbstractSeveral firn/ice cores were recovered from the Siberian Altai (Belukha plateau), central Tien Shan (Inilchek glacier) and the Tibetan Plateau (Zuoqiupu glacier, Bomi) from 1998 to 2003. The comparison analyses of stable-isotope/geochemistry records obtained from these firn/ice cores identified the physical links controlling the climate-related signals at the seasonal-scale variability. The core data related to physical stratigraphy, meteorology and synoptic atmospheric dynamics were the basis for calibration, validation and clustering of the relationships between the firn-/ice-core isotope/ geochemistry and snow accumulation, air temperature and precipitation origin. The mean annual accumulation (in water equivalent) was 106 gcm−2 a−1 at Inilchek glacier, 69 gcm−2 a−1 at Belukha and 196 g cm−2 a−1 at Zuoqiupu. The slopes in regression lines between the δ18O ice-core records and air temperature were found to be positive for the Tien Shan and Altai glaciers and negative for southeastern Tibet, where heavy amounts of isotopically depleted precipitation occur during summer monsoons. The technique of coupling synoptic climatology and meteorological data with δ18O and d-excess in firn-core records was developed to determine climate-related signals and to identify the origin of moisture. In Altai, two-thirds of accumulation from 1984 to 2001 was formed from oceanic precipitation, and the rest of the precipitation was recycled over Aral–Caspian sources. In the Tien Shan, 87% of snow accumulation forms by precipitation originating from the Aral–Caspian closed basin, the eastern Mediterranean and Black Seas, and 13% from the North Atlantic.
Glacier retreat as a result of climate warming and increased precipitation in the Tarim river basin, northwest China
Authors: Liu Shiyin , Ding Yongjian , Shangguan Donghui , Zhang Yong , Li Jing , Han Haidong , Wang Jian , Xie Cangwei 
Published: November 2007

AbstractThe Tarim river basin, a river system formed by the convergence of nine tributaries, is the most heavily glacierized watershed in arid northwest China. In the basin, there are 11 665 glaciers with a total area of 19 878 km2 and a volume of 2313 km3. Glaciers in the basin play a significant role in the water resource system. It is estimated that they provide about 133 x 108 m3 of meltwater annually, contributing 39% of the total river runoff. Under the influence of global warming, northwest China has experienced a generally warmer and drier climate since the mid-19th century. However, a so-called ‘warm and wet transition’ has occurred since the late 1980s, evidenced by an increase in both precipitation and stream discharge in the Xinjiang Autonomous Region and neighboring regions. This paper describes how glaciers in the Tarim river basin have responded to such warming and increased precipitation, and the impact of these glacier changes. We analyzed the variations of more than 3000 glaciers since the 1960s using topographical maps, high-resolution satellite images and aerial photographs of the river basin. Our results indicate that glaciers in the basin have been mostly in retreat in the past 40 years, and ice wastage has significantly influenced water resources in the Tarim river basin. Estimation by a degree-day meltwater model shows the positive anomaly in stream runoff of the Tailan river can be partly attributed to the increase in glacier runoff (amounting to one-third of the stream discharge), and a rough estimation using observed average ablation on the termini of 15 glaciers in China verifies that the mass loss calculated by a glacier area-volume relation is reasonable.
Glacier variations and climate change in the central Himalaya over the past few decades
Authors: Ren Jiawen , Jing Zhefan , Pu Jianchen , Qin Xiang 
Published: November 2007

AbstractGlacier 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.