Showing papers on "Accumulation zone published in 2007"

Recent glacier retreat in the Caucasus Mountains, Russia, and associated increase in supraglacial debris cover and supra-/proglacial lake development

Abstract: This paper reports changes in supraglacial debris cover and supra-/proglacial lake development associated with recent glacier retreat (1985-2000) in the central Caucasus Mountains, Russia. Satellite imagery (Landsat TM and ETM+) was used to map the surface area and supraglacial debris cover on six neighbouring glaciers in the Adylsu valley through a process of manual digitizing on a false-colour composite of bands 5, 4, 3 (red, green, blue). The distribution and surface area of supraglacial and proglacial lakes was digitized for a larger area, which extended to the whole Landsat scene. We also compare our satellite interpretations to field observations in the Adylsu valley. Supraglacial debris cover ranges from 25% on individual glaciers, but glacier retreat between 1985 and 2000 resulted in a 3-6% increase in the proportion of each glacier covered by debris. The only exception to this trend was a very small glacier where debris cover did not change significantly and remote mapping proved more difficult. The increase in debris cover is characterized by a progressive up- glacier migration, which we suggest is being driven by focused ablation (and therefore glacier thinning) at the up-glacier limit of the debris cover, resulting in the progressive exposure of englacial debris. Glacier retreat has also been accompanied by an increase in the number of proglacial and supraglacial lakes in our study area, from 16 in 1985 to 24 in 2000, representing a 57% increase in their cumulative surface area. These lakes appear to be impounded by relatively recently lateral and terminal moraines and by debris deposits on the surface of the glacier. The changes in glacier surface characteristics reported here are likely to exert a profound influence on glacier mass balance and their future response to climate change. They may also increase the likelihood of glacier-related hazards (lake outbursts, debris slides), and future monitoring is recommended.

A full Stokes-flow thermo-mechanical model for firn and ice applied to the Gorshkov crater glacier, Kamchatka

Abstract: The Gorshkov crater glacier at Ushkovsky volcano, Kamchatka, is characterized by a large aspect ratio and special thermodynamic conditions at the bedrock caused by a locally enhanced and spatially varying geothermal heat flux. Furthermore, large parts of this glacier consist of firn rather than pure ice, which alters the rheological properties (such as viscosity and compressibility) of the glacier. We present a newly developed, thermo-mechanically coupled, three-dimensional flow model based on the finite-element (FE) modeling software Elmer, and apply it to the Gorshkov crater glacier. By assuming steady-state conditions, the present-day velocity field, temperature field, basal melting rate and age distribution are simulated. We find that flow velocities are generally small (10's of centimeters per year). Horizontal and vertical velocities are of comparable magnitude, which shows that the shallow-ice approximation is not applicable. Owing to the spatially variable volcanic heat flux, the thermal regime at the ice base is cold in the deeper parts of the glacier and temperate in the shallower parts. The measured temperature profile and age horizons at the K2 borehole are reproduced quite well, and remaining discrepancies may be attributed to transient (non-steady-state) conditions. Firn compressibility is identified as a crucial element for the modeling approach.

Glacier changes in the Siberian Altai Mountains, Ob river basin, (1952–2006) estimated with high resolution imagery

Abstract: The Siberian Altai covers about 70% of the area of all south Siberian glaciers, which provide fresh water to the upper tributaries of the Ob and Yenisey rivers. The observed air temperature has increased by 1.2 °C over northern Eurasia during the last 120 years, affecting the degradation of the Siberian Altai glaciers. In this study, we estimated glacier area changes in the Aktru River basin (44.8 km2), located in the central Altai mountains. We used the 1952, 1966, 1975 and 2006 remote sensed images with 0.6–3.0 m spatial resolution (aerial photographs, Corona and PRISM satellite images) and differential GPS (DGPS) data. From 1952 to 2006, the total glacier area in the Aktru basin shrank by 7.2% (1.2 km2). During the last three decades, the rate of glacier area loss increased by a factor of 1.8, thus resembling trends in other mountain systems of Eurasia (Alps, Tien Shan). The glacier area changes were caused mainly by increase of summer air temperature by 1.03 °C (from 1951 to 2000) at elevations below 2500 m, which intensified the melt of the glacier's ice in the ablation zone. At elevations above 2500 m (upper accumulation zone), the summer air temperature increased by only 0.83 °C.

Effect of dust event timing on glacier runoff: sensitivity analysis for a Tibetan glacier

Abstract: The impact of the timing of dust deposition on glacier runoff was evaluated using a glacier mass-balance model with a newly improved scheme to track a dusted layer in a snow layer of a glacier. The lowering of surface albedo due to the dusted layer appearing leads to a drastic increase of glacier runoff even under the same meteorological conditions. Calculations of seasonal sensitivity, the relationship between dusted date and resulting runoff, have shown that dust deposition during a melting season might cause a drastic mass outflow from a glacier through changing the surface albedo during the melting season. Copyright © 2006 John Wiley & Sons, Ltd.

Controls on advance of tidewater glaciers: results from numerical modeling applied to Columbia Glacier

Abstract: [1] A one-dimensional numerical ice flow model is used to study the advance of a tidewater glacier into deep water. Starting with ice-free conditions, the model simulates glacier growth at higher elevations followed by advance on land to the head of the fjord. Once the terminus reaches a bed below sea level, calving is initiated. A series of simulations was carried out with various boundary conditions and parameterizations of the annual mass balance. The results suggest that irrespective of the calving criterion and accumulation rate in the catchment area, it is impossible for the glacier terminus to advance into deeper water (>300 m water depth) unless sedimentation at the glacier front is included. The advance of Columbia Glacier, Alaska, is reproduced by the model by including “conveyor belt” recycling of subglacial sediment and the formation of a sediment bank at the glacier terminus. Results indicate slow advance through the deep fjord and faster advance in shallow waters approaching the terminal moraine shoal and the mouth of the fjord.

Glacier meltwater and runoff modelling, Keqicar Baqi glacier, southwestern Tien Shan, China

Abstract: Meltwater and runoff from Keqicar Baqi glacier, a large glacier in the southwestern Tien Shan, northwestern China, are simulated using a modified degree-day model including potential clear- sky direct solar radiation, coupled with a linear reservoir model for the period 1 July to 12 September 2003. There is good agreement between modelled and measured meltwater at ablation stakes and between simulated and observed runoff at the glacier terminus. A reconstruction of glacier meltwater and runoff from an assumed debris-free surface during the study period shows that the effect of the debris layer on glacier meltwater generation crucially affects glacier runoff. The model is also used to calculate glacier runoff given the climate scenario resulting from a doubling of CO2 as projected by the ReCM2 regional climate model. The projected changes in temperature and precipitation vary from 0 to 2.78C and from 0 to 25%, respectively. Results indicate that glacier runoff increases linearly with temperature over these ranges whether or not the debris layer is taken into consideration. The effect of change in temperature is much more noticeable than that for change in precipitation. Due to the debris layer predominantly covering (and insulating) the ablation area, the response of glacier runoff is less sensitive to temperature increase with a debris-covered surface than with a debris-free surface. Glacier runoff is also markedly reduced when a reduced glacier area is prescribed in the þ2:78C scenario.

A surface energy exchange model of glacier melt and net mass balance

Abstract: An energy balance model of surface climate and melt for a glacierized area is described, and applied to simulate ablation and net mass balance on Peyto Glacier. Surface characteristics are assigned according to general knowledge from physical climatology and experimental data from the glacier itself. A known elevational distribution of snow covers the glacier at the beginning of the ablation season, then melts in response to simulated energy input to the surface, thus exposing an ever increasing area of ice. The end result is the annual net mass balance, which is shown to be very sensitive to annual mean temperature, solar energy input, atmospheric emissivity, surface albedo, and climatic regime. Maritime climates produce steeper elevational gradients of net mass balance than do continental climates, which, in turn, are steeper than those created under Arctic conditions. It is also found that, in addition to lag caused by internal drainage development, there must be delay in peak meltwater production owing to changing surface conditions because, as snowline elevation rises, the glacier evolves into a more effective collector of solar energy.

Tide-induced perturbations of glacier velocities

Abstract: Recent observations showing substantial diurnal changes in velocities of glaciers flowing into the ocean, measured at locations far inland of glacier grounding lines, add fuel to the ongoing debate concerning the ability of glaciers to transmit longitudinal-stress perturbations over large distances. Resolution of this debate has major implications for the prediction of glacier mass balance, because it determines how rapidly a glacier can respond dynamically to changes such as weakening or removal of an ice shelf. Current IPCC assessment of sea-level rise takes little account of such changes, on the assumption that dynamic responses would be too slow to have any appreciable effect on ice discharge fluxes. However, this assumption must be questioned in view of observations showing massive increases in glacier velocities following removal of parts of the Larsen Ice Shelf, Antarctica, and of others showing diurnal velocity changes apparently linked to the tides. Here, I use a simple force-perturbation model to calculate the response of glacier strain rates to tidal rise and fall, assuming associated longitudinal-force perturbations are transmitted swiftly far inland of the glacier grounding line. Results show reasonable agreement with observations from an Alaskan glacier, where the velocity changes extended only a short distance up-glacier. However, for larger Antarctic glaciers, big velocity changes extending far upstream cannot be explained by this mechanism, unless ice-shelf “back forces” change substantially with the tides. Additional insight will require continuous measurement of velocity and strain-rate profiles along flow lines of glaciers and ice shelves. An example is suggested, involving continuous GPS measurements at a series of locations along the centre line of Glaciar San Rafael, Chile, extending from near the calving front to perhaps 20 km inland. Tidal range here is about ± 0.8 m, which should be sufficient to cause a variation in ice-front velocity of ± 2 cm h − 1 about its average value of 75 cm h − 1 , assuming local seawater depth of 150 m and glacier thickness of 200–400 m.

Modeling long-term stability of the Ferrar Glacier, East Antarctica: Implications for interpreting cosmogenic nuclide inheritance

Abstract: [1] The Ferrar Glacier extends from the Taylor Dome, through the Royal Society Range, to the Ross Sea. Its pathway is strongly influenced by large-scale topographic features. Ice thins and flows over these features, like water over a dam. Recently acquired evidence demonstrates that the profile of the Ferrar Glacier has been relatively static for the last ∼4 million years. This long record of stability is in sharp contrast to numerous other features in Antarctica and motivates an exploration of the stability with a numerical model. Large variations in ice thickness along the Ferrar profile make necessary a thermomechanically coupled model which includes higher-order stress terms. Such a model is presented here and then is used to investigate (1) glacial ice flow patterns, (2) stress fields, and (3) sensitivity to climate forcing. In all three cases, the Ferrar Glacier is shown to be generally insensitive to the changes and to have stability consistent with cosmogenic nuclide evidence. The modeling is novel in that the Ferrar Glacier is a member of a class of glaciers which has never before been modeled. Ice flow results indicate that curious flow patterns arise in the glacier, producing very old ice (∼100,000 years) near the surface up glacier of thinning points. This flow pattern is demonstrated to be of consequence when interpreting the inheritance of cosmogenic nuclides in two ways. First, the velocity field is used to determine the maximum time a cobble found on the glacier surface could have been exposed to cosmic radiation. Second, the flow entrains supraglacial material from the glacier's surface, shielding it from cosmic rays for a period, and then deposits the material at the surface down glacier. Both flow effects are discussed in relation to cosmogenic nuclide inheritance and are quantified. The sensitivity of the results to past climates and glacier surfaces is also considered.

CO2 isotopes as tracers of firn air diffusion and age in an Arctic ice cap with summer melting, Devon Island, Canada

Abstract: [1] Firn air and ice have been sampled and analyzed for trace gases (CO2, N2O, CH4, and CO) and isotopes (14C, 13C, and 18O of CO2; 3H of ice) at 3 m intervals from the surface to the depth of closure at 60 m on the Devon Island Ice Cap, a low-elevation permanent glacier in the Canadian Arctic Islands, to investigate firn diffusion and the effects of summer melting. The 14CO2 profile from the permeable firn includes the 1963 thermonuclear peak at a depth of 53.9 ± 1.5 m. The twofold increase and rapid decay that characterize the recent atmospheric history for 14CO2 provide a robust atmospheric scenario that is used with a firn air diffusion model to inversely construct the firn diffusivity profile. The results show a permeable but essentially nondiffusive zone from 50 to 60 m depth. A firn-ice age profile was produced from density measurements, and accumulation rates were calibrated with the depth of the 1963 thermonuclear 3H peak. The average ages for CO2 in the sampled firn air profile were determined by a new method based on the rate of 18O exchange between CO2 and the ice matrix. Calibrated with the 1963 peak for thermonuclear 14CO2, a 21.2-year reaction halftime is calculated for exchange taking place at the firn temperature of −22.8°C on Devon. This gives an average age of 54.9 (+6.0/−12.0) years for firn air at 60 m depth in 140-year-old ice. Thus CO2 has a mean age 85 years younger than associated ice at the point of occlusion. The measured in firn air provides no indication of alteration by summer melting, which is attributed to a high degree of convective and diffusive flushing of the upper firn as shown by diffusion modeling. This suggests that ice sheets with summer melt layers can reliably preserve atmospheric trace gas signals.

Glacier winds in the Rongbuk Valley, north of Mount Everest: 1. Meteorological modeling with remote sensing data

Abstract: [1] Persistent glacier winds blowing from noon to midnight in summer are present in the Rongbuk Valley, north of Mount Everest, with a maximum speed of 10 m s−1 and a vertical thickness as high as 1 km. These glacier winds may bring upper level atmosphere ozone to the surface, having a significant impact on the atmospheric environment. Such phenomena may be typical of the Tibetan Plateau, where most high mountains are covered by snow or glacier ice throughout the year. The Advanced Regional Prediction Model was used to simulate the down-valley flows, using realistic topography but neglecting synoptic winds. The modeling results agree well with the observations obtained in June 2002, revealing that the glacier winds are thermal flows primarily driven by the along-valley temperature gradient between the colder air over the glacier surface and the warmer air over surface areas covered by rock debris, which maintains air advection along the Rongbuk Valley. Downslope winds over the glacier slopes, especially from the western valley side, and the West Rongbuk Glacier, were forced by their inertia farther down into the valley and would intensify the glacier winds. The narrowing of the Rongbuk Valley could also speed up the glacier winds. Sensitivity tests showed that the detailed distribution of the Rongbuk Glacier, delineated by data from the Enhanced Thematic Mapper Plus on Landsat 7, plays an important role in glacier winds development. The glacier winds could be much weaker in winter when the area is completely snow covered.

Response of Glacier Melting to Climate Change——Take rümqi Glacier No.1 as an Example

Abstract: Current glacier recession under climate warming has drawn widely attention around the world.Initiated from 1958,the observations of rumqi Glacier No.1 at the headwaters of rumqi River in eastern Tianshan promise the best datasets of glacier and climate changes in China.Taking rumqi glacier No.1 as an example,this paper has analyzed the response of the glacier to the climate change.The results show that during the past 50 years,remarkable changes occurred on the glacier,including snow-firn stratigraphy,glacial zone,glacial temperature(borehole temperature),glacier area,and glacier terminus position etc.These changes are found to be closely related to temperature rise in this area.The glacier retreat appears throughout the entire observed time period and shows accelerated tendency during the last 20 years,particularly after 1995.In addition to summer temperature increase,other two reasons may also be response to the acceleration of glacier melting: one is the glacial temperature rise,which may reduce the cold reserve in the glacier and thus increase the sensitivity of the glacier to air temperature rise;the other is the decrease of albedo on the glacier surface,which evidently enhance absorption of radiation.It is also found that commonly determined by both precipitation and temperature,the mass balance can be determined only by air temperature if the temperature rises up to a certain level,even under a heavy precipitation background.In addition,this paper has also discussed the predication of future change of the glacier.

Subglacial drainage system changes of the Gulkana Glacier, Alaska: discharge and sediment load observations and modelling

Abstract: Hydrological characteristics of englacial and subglacial drainage systems in Gulkana Glacier, Alaska, were examined by analysing temporal variations of discharge and sediment load in the proglacial Phelan Creek in 2001. From data plots on semi-log paper, it appeared appropriate to separate both discharge and sediment load into fast and slow components. The two components were possibly produced by two different drainage systems: an englacial and subglacial, ‘channellized’ system in the ablation zone, and a subglacial, ‘distributed’ system in the accumulation zone. The data indicate the occurrence of an event during which part of the ‘distributed’ drainage system changed into the ‘channellized’ drainage system. The daily time-series of discharge and sediment load were represented using a tank model. In the model, the drainage from an additional tank was added, supposing that a subglacial reservoir full of water and sediment collapsed slowly when the subglacial drainage system changed from distributed to channellized. The simulation with the collapsed tank gave much more reasonable results than those with no collapsed tank. The contribution of the collapsed tank to total sediment load is 24%, which is much larger than 9% to total discharge. Copyright © 2006 John Wiley & Sons, Ltd.

Basic Features of the Miaoergou Flat-Topped Glacier in East Tianshan Mountains and Its Thickness Change over the Past 24 Years

Abstract: The shrinkage of alpine glaciers in the twentieth century is on a global scale.For a number of glaciers,the rate of shrinkage appears to have accelerated toward the end of the century.Located at the easternmost Tianshan Mountains in central Asia,Miaoergou Flat-Topped Glacier is surrounded by vast desert and gobi,where the Asia dust storms originate.Furthermore,the glaciers in this area are the major water supply for the extremely dry land.Therefore,the changes of these glaciers and their ice core records are widely concerned.On the basis of field investigations in 2004 and 2005 and the ice core records recovered from the summit of the glacier during 2005,this paper presents general characteristics of the Miaoergou Flat-Topped Glacier and its thickness changes over the past 24 years.The result shows that the glacial borehole temperature was around-7 ℃ at 10 m depth and-8.3 ℃ at the 60 m borehole bottom,indicating that this is a typical continental glacier.The net accumulation rate at the summit was approximately 200 mm\5a-1.Over the past 24 years,the glacier has evidently thinned around 5 m at the upper reaches.The ice core stratigraphy indicates that enhancement of the glacier melting may occur during the last 20 years.

Geometry change between 1990 and 2003 at Finsterwalderbreen, a Svalbard surge-type glacier, from GPS profiling

Abstract: Surface mass-balance and geometry data are key to quantifying the climate response of glaciers, and confidence in data synthesis and model interpretations and forecasts requires data from as wide a range of locations and glacier types as possible. This paper presents measurements of surface elevation change at the Svalbard surge-type glacier Finsterwalderbreen, by comparing a 1990 digital elevation model (DEM) with a surface GPS profile from 2003. The pattern of elevation change is consistent with that previously noted between 1970 and 1990, and reflects the continued quiescent- phase evolution of the glacier, with mass loss in the down-glacier/receiving area of up to -1.25 m w.e. a -1 , and mass gain in the up-glacier/reservoir area of up to 0.60 m w.e. a -1 ; the area-weighted, mean change for the whole glacier is 0.19 m w.e. a -1 . The spatial pattern of elevation increase and decrease is complex, and the boundary between thickening and thinning determined by combining GPS and DEM data does not appear to correspond with the equilibrium-line altitude determined from surface mass-balance measurements. There is no evidence yet of a decrease in the rate of reservoir area build-up driven by mass-balance change resulting from the warmer winter air temperatures, and decreased proportion of snowfall in total precipitation, noted at meteorological stations in Svalbard.

Records of Precipitation in the Muztag Ata Ice Core and Its Climate Significance to Glacier Water Resources

Abstract: During the summer 2003,a 41-m firn and ice core was extracted at the elevation of 7 010 m above sea level to determine annual accumulation rates at Muztag Ata Peak in the East Pamirs.Using strong seasonally variation of oxygen isotopic of the core to define annual layers,a 45-year record is obtained.Annual snow accumulation over the period is about 0.62 m water equivalent on average.The snow accumulation was higher during 1958-1975 than during 1976-2003.The accumulation decreased by a factor of two to three between 1958 and 2003.The reconstruction of mass balance in Muztag Ata glacier by using snow accumulation and temperature show a dramatically increasing wastage tendency in the past 20 years.The mean mass balance in Muztag Ata glacier was-123 mm·a-1 during the period of 1960-2003,while it reached to-419 mm·a-1 in the period of 1990-2003.Both the decreasing in snow accumulation at the high mountain and the increasing temperature are responsible for the wastage of glacier in Muztag Ata region.The increment of glacier wastage can enhance runoff of the Tarim River fed by glacier melting water in a short period.However,in the condition of global warming the glacier without enough supplements will shrink quickly.For a long period,most of the snow and ice will be gone and the Tarim River runoff will be reduced without glacier melting water fed.

Mass Balance of the Zhadang Glacier in the Central Tibetan Plateau

Abstract: New observations have been made on the Zhadang Glacier in Nyainqentanglha Rang in 2005/2006Based on the ocservation,the mass balance of the glacier was calculated to be negative,-1 54757 mm(mm we),suggesting that the glacier was thinning dramaticallyIn 2005/2006,the glacier was characterized by strong negative mass balance with a rising snow lineBoth the mass balance and snow line respond sensitively to the global warmingIt is infrequent that a large negative mass balance of glacier in the Central Tibetan Plateau like the Zhadang GlacierWith the global warming,it is expected that the glacier will experience negative mass balance,thinning,shrinking and snow line rising

Characteristics of the Surface Energy Balance of the Qiyi Glacier in Qilian Mountains in Melting Season

Abstract: The surface energy balance of a glacier describes the physical connection between ice/snow ablation and climatic forcing.To expand the knowledge on the response of the Qiyi Glacier to climate variation,the influence of climate change and glacier melting were analyzed,and the energy balance at the glacier surface was estimated too,by using the meteorology data observed by the Auto Weather Station of Qiyi Glacier,Qilian Mountains from June 9 to September 28.The calculation of heat balance components show that net radiation,turbulent heat fluxes and heat used for glacier/snow melting are the major elements of the energy balance.During the period,the heat income comprises net radiation and sensible heat exchange with the ratio of 82.4% and 17.6%,respectively;the heat outcome comprises latent heat flux and heat used for glacier/snow melting with the ratio of 12.8% and 87.2%,respectively.According to energy balance theory,the glacier surface melting is modeled,and the modeled glacier melting value is in agreement with the observed glacier melting value almost exactly,with a correlation coefficient equal to 0.83.

Influence of Debris Cover on Ogive-like Surface Morphology of Bilchenok Glacier in Kamchatka

Abstract: Bilchenok Glacier is a surging glacier in the Kamchatka Peninsula, Russia, which most recently surged in 1982 and is currently in its quiescent phase. Field research in 1998 revealed an ogive-like repeated pattern of transverse ridges and intervening gently sloping ice at the surface of the ablation area of this glacier. It was also observed that most of the glacial surface was covered by volcanic rocks and ash, and the debris thickness on the ridges was more than 1 m, whereas the gently sloping ice was covered by thin debris. We posit that the pattern of the debris thickness is caused by the unique conditions of Bilchenok Glacier, namely, the restricted position of its debris supply at the foot of the rock walls beside the icefall and its surging behavior. The distance between the ridges might indicate the total horizontal displacement attributable to surges. The dependence of the ablation rate on the debris thickness can result in a highly undulating ice surface between the ridge and the gently...

Portage Glacier and Portage Pass, Alaska: Little Ice Age dynamics and the chronology of glacial retreat

Abstract: Portage Glacier currently acts as a lacustrine calving glacier discharging icebergs into Portage Lake, Alaska. This glacier advanced during the Little Ice Age, and from 1799 to 1911 completely filled the lake basin and deposited three large moraines downvalley of the modern lakeshore. During this time the glacial ablation regime was dominated by melting and a large outwash stream flowed from the glacier to Turnagain Arm. Portage Lake, approximately 5 km long, 2 km wide and 200 m deep, began to form in 1914 after the glacier retreated off the 1852 AD moraine. The deep water of the lake caused calving to become the dominant ablation process. From 1799 to 1914, the retreat rate averaged 3.8 m/year when the ablation regime was dominated by melting, but this rate increased to 56.3 m/year from 1914 to 1994 as the ablation became dominated by calving into the deep lake. Since 1994, the terminus of Portage Glacier has become stabilized where it rests on the bedrock shoreline at the east end of the lake. ...

Solving Three Problems of Exploration and Engineering Geology by Digital Terrain Analysis

Abstract: In the smooth-surface approximation, local accumulation of a flow is controlled by relative deceleration and convergence. Flow deceleration is determined by vertical curvature of the land surface, while flow convergence is controlled by horizontal curvature. There is a concurrent action of flow convergence and relative deceleration at areas marked by negative values of both of these curvatures. These areas are said to be relative accumulation zones. We describe basic principles of applying maps of relative accumulation zones to solve three problems of exploration and engineering geology: (1) exploration of alluvial placers; (2) prediction of landsliding on reservoir shores; and (3) prediction of soil degradation and contamination along pipelines. The deposition of placer minerals is most likely to occur in relative accumulation zones with slope steepness below 3°, all other factors being equal. The activation of slope instability is most probably to occur in relative accumulation zones with slope steepness beyond 15°, which are adjacent to, upslope the reservoir water level. Soil degradation (waterlogging and salinisation) may be observed in relative accumulation zones adjacent to, upslope a pipeline. After the pipeline failure, one can use a map of specific catchment area to determine paths of lateral migration of petroleum in the landscape. Petroleum products are most likely to concentrate in relative accumulation zones situated along a flow line originating at a pipeline hole. To refine the prediction, one should analyse accumulation zone maps together with geological, geophysical, geochemical, soil, plant, and remotely sensed data as well as with models of other topographic variables.

Quantifying sublimation of buried glacier ice in Beacon Valley

Abstract: Summary A remnant of Taylor Glacier ice rests beneath a 40-to-80-cm-thick layer of sublimation till in central Bea-con Valley, Antarctica. Our 1-D vapor diffusion model, with input from micrometeorological data collected during the 2004 austral summer, shows that vapor flows into and out of sublimation till at rates dependent on the non-linear varia-tion of vapor concentration with depth. Although measured meteorological conditions during the study interval favored a net loss of buried glacier ice (~0.017 mm over 42 days), an average rate of ice sublimation that is consistent with a loss of 400 m of ice over 8.1 Ma (an amount suggested by Potter et al., 2003) is permissible if local temperatures de-crease by ~3oC; relative humidity increases by 15%; or snowmelt infiltration equals ~0.001 mm/day. Our model results are consistent with the potential for long-term survival of buried glacier ice in the hyper-arid upland zone of the Dry Valleys. Citation: Kowalewski, D.E. and D.R. Marchant (2007), Quantifying sublimation of buried glacier ice in Beacon Valley,

Chemical Characteristics of the Surface Snow on Glacier No.1 at the rümqi River Head:Organic Acids and Inorganic Anions

Abstract: Surface snow links the atmosphere and the ice core in geochemical compositions,thus,it is a benchmark for identifying post depositional changes of the geochemical constituent in the ice forming processes.For monitoring the variations of chemical composition in the transforms from snow to ice,snow samples collected during March 2004 to March 2005 field campaign from the accumulation zone of the Glacier No.1 at the rumqi River head,Tianshan Mountains,China,were analyzed for low molecular weight organic acids and inorganic anions.The organic acids in the snow include HCOO-,CH3COO-,C2H5COOand(COO)2-2,while the inorganic anions are F-,Cl-,NO-2,NO-3,SO2-4 and PO3-4.Most of the organic acids,except for(COO)2-2 and high-concentration inorganic anions as Cl-,NO-3 and SO2-4,demonstrate seasonal variations from April to September,which are caused primarily by strong local atmospheric circulations and the prevailing westerly in the seasons,with much even concentrations in the winter.All the anions change considerably from the late spring to early autumn,and reveal both the lowest and highest concentrations in a year.On the other hand,(COO)2-2 and low-concentration inorganic anions as F-,NO-2and PO3-4 show high variations in the whole year.Analyzed results indicate that the majority of high concentration anions can be preserved in the surface snow for a long time(at least half a year) without change in their concentrations if the weather condition remains relatively stable.

Petroleum Geological Characteristics and Tertiary Oil-prospect Evaluation in Kumukuli Basin

Abstract: Kumukuli Basin was situated between Qimantage Mountain and East Kunlun Aerojin Mountain.It was a Tertiary deposional basin with thickness about 7000m,it was a delta basin with the widest position about 255km and covered with a total area of 1.6×104km2.The Tertiary oil geologic condition was initially evaluated from the aspects of the basin structures,depositional facies,source rocks,reservoir and cap-rock conditions.Oil-bearing prospects of the basin were essentially evaluated.Results of the study show that hydrocarbon accumulation positions are on both sides of the central uplift belt,the next is on the north and south of megasyncline.On the basis of the importance of oil and gas enrichment,its oil-bearing prospective areas are divided into 3 zones,such as the northern oil and gas accumulation zone,the southern accumulation zone and Xiantuliang accumulation zone.