The thermal structure of Hansbreen, a tidewater glacier in southern Spitsbergen, Svalbard

Ice temperature measurements were taken from three shallow and five deep (to bedrock) boreholes on Hansbreen, Svalbard, in selected years between 1988 and 1994. In general, results show a subpolar, polythermal structure. The glacier accumulation zone is of warm ice within the entire vertical profile except the uppermost layer of seasonal temperature fluctuations where there is an upper cold ice layer in the ablation zone which varies in thickness and may even be absent in the western lateral part. The upper layer of cold ice thins along the glacier centre-line from the equilibrium line altitude down to the glacier front. The depth of the pressure melting, indicating the base of the cold ice layer, was defined at the borehole measurement sites but was not manifested as an internal reflection horizon using multi-frequency radar methods. The isotherm lies about 20 m above a radar internal reflecting horizon near the equilibrium line altitude and about 40 m above it in the frontal part of the glacier. The internal reflection horizon almost certainly reflects the high water content within temperate ice and not the cold/temperate ice interface. At 10 m depth, the temperatures are 2–3°C higher than the calculated mean annual air temperatures, demonstrating the importance of meltwater refreezing on the release of latent heat.     

Distribution features of stable oxygen isotopes in the typical monsoon temperate-glacier region, Mountain Yulong in China

During the summers of 1999 and 2000, sampling was carried out in Mt. Yulong, for the investigation of the spatial distribution of oxygen stable isotope in the atmospheric glacial hydro system and similar results obtained in the two years have confirmed our conclusion. There is an evident negative correlation between stable isotopic composition and air temperature precipitation amount, suggesting that there exits a strong "precipitation amount effect" in this typical monsoon temperate glacier region. There are marked differences between the δ 18 O values in winter accumulated snow, glacial meltwater, summer precipitation and glacier feeding stream. Under the control of varied climatic conditions, spatial and temporal variations of above glacial hydro mediums are apparent. Isotopic depletion or fractionation and ionic changes had occurred during the phase change and transformation processes of snow ice, ice meltwater, flowing of runoff and contact with bedrock. The variation of stable isotope in a runoff can reflect not only its own flowing process but also its different feeding sources.     

Temperature distribution of Collins Ice Cap,King George Island,Antarctica

ＴｅｍｐｅｒａｔｕｒｅｄｉｓｔｒｉｂｕｔｉｏｎｏｆＣｏｌｌｉｎｓＩｃｅＣａｐ，ＫｉｎｇＧｅｏｒｇｅＩｓｌａｎｄ，ＡｎｔａｒｃｔｉｃａＨａｎＪｉａｎｋａｎｇ（韩建康）ａｎｄＪｉｎＨｕｉｊｉｕｎ（金会军）（ＬａｎｚｈｏｕＩｎｓｔｉｔｕｔｅｏｆＧｌａｃｉｏ...     

南极洲纳尔逊冰帽浅层粒雪／冰的晶体组构特征

对纳尔逊冰帽３个地点浅层粒雪／冰芯的晶体组构测量表明，冰晶ｃ轴在冰帽表面具有优势方位，２０ｍ深度内普遍出现双扇形组构，在２０－３０ｍ深度具有向单极大型变化的趋势。这与所报道的中低纬度山地温冰川上的晶体组构特征有明显不同。估计大量融水渗浸和再冻结作用对冰晶组构有重要影响，但详细机制尚不清楚     

ICE THICKNESS,ABLATION, AND OTHER GLACIOLOGICAL MEASUREMENTS ON UPPER FREMONT GLACIER,WYOMING

Glaciological investigations of the Upper Fremont Glacier in the Wind River Range of Wyoming were conducted during 1990–1991. The glaciological data will provide baseline information for monitoring future changes to the glacier and support ongoing research utilizing glacial-ice-core composition to reconstruct paleoenvironmental records. Ice thickness, determined by radio-echo sounding, ranged from 60 to 172 m in the upper half of the glacier. Radio-echo sounding of ice thickness at one point was confirmed by drilling 159.7 m to bedrock. The difference between radio-echo sounding depth and measured drilling depth was about 4 m. Annual ablation (including snow, firn, and ice) measured for the 1990–1991 period averaged about 0.93 m/a. Densification proceeds rapidly on Upper Fremont Glacier. Measured densities in the near-surface parts of the glacier ranged from 4.4 x 10⁵ g/m³ at the surface to larger than 8.5 x 10⁵ g/m³ at depths exceeding 14 m. Surface ice velocity and direction were monitored from July 1990 to August 1991. Ice velocity decreased in a downslope direction. The largest measured velocity was about 3.1 m/a and the smallest was 0.8 m/a. The yearly mean air temperature of the study site during the period from July 11, 1990 to July 10, 1991 was -6.9°. Borehole temperatures from 10-m depths are 0 ± 0.4°. The warmer borehole temperatures relative to the yearly mean air temperature may be caused by the latent heat of freezing, as meltwater from the surface percolates into the glacier and refreezes. [Key words: glaciers, Wyoming, Wind River Range, ice thickness, ablation rates.]     

Geocryological characteristics of the upper permafrost in a tundra-forest transition of the Indigirka River Valley,Russia

Understanding geocryological characteristics of frozen sediment, such as cryostratigraphy, ice content, and stable isotope ratio of ground ice, is essential to predicting consequences of projected permafrost thaw in response to global warming. These characteristics determine thermokarst extent and controls hydrological regime—and hence vegetation growth—especially in areas of high latitude; it also yields knowledge about the history of changes in the hydrological regime. To obtain these fundamental data, we sampled and analyzed unfrozen and frozen surficial sediments from 18 boreholes down to 1–2.3 m depth at five sites near Chokurdakh, Russia. Profiles of volumetric ice content in upper permafrost excluding wedge ice volume showed large variation, ranging from 40 to 96%, with an average of 75%. This large amount of ground ice was in the form of ice lenses or veins forming well-developed cryostructures, mainly due to freezing of frost-susceptible sediment under water-saturated condition. Our analysis of geocryological characteristics in frozen ground including ice content, cryostratigraphy, soil mechanical characteristics, organic matter content and components, and water stable isotope ratio provided information to reconstruct terrestrial paleo-environments and to estimate the influence of recent maximum thaw depth, microtopography, and flooding upon permafrost development in permafrost regions of NE Russia.     

Structure and heat content of the West Spitsbergen Current

The seasonal evolution of the hydrographic structure of the West Spitsbergen Current (WSC) above bottom depths from 300 m to 800 m is discussed based on a modern data set with high spatial resolution. The WSC appears to have a core with high temperature and salinity, linked to the topography in this depth interval, with a width on the order of 10 km. Strong cooling occurs in the autumn, reducing the heat content of the upper 200 m, but advected temperature and salinity maxima survive close to the surface in spring when air-sea exchange and vertical mixing is hampered by sea ice and meltwater.     

2003年夏季东南印度洋上层海洋的水文特征

本文利用 2 0 0 3年 2月我国第 1 9次南极考察队在南极普里兹湾到澳大利亚弗里曼特尔南印度洋断面上获得的XBT和XCTD数据 ,分析了该断面上层的水团分布和锋面的特征 ,并讨论了极锋以南表层的淡水输入和热量输入与海冰、降水及平流之间的关系。南极夏季表层水(AASSW)、亚南极表层水 (SASW)、亚热带表层水 (STSW)分布于温盐跃层之上的混合层中 ,由南向北依次分布。AASSW之下是向北延伸的温度最小值层 ,即冬季水 (WW) ,其下则是涌升的上层南极饶及深层水 (UCDW)。南侵的高温高盐的亚热带表层水 (STSW)之下是温度和盐度相对均匀的亚南极模式水 (SAMW)。本航次发现 ,在 63.5°S ,79.7°E的 60 0m以深有低盐水体 (相对其周围水体 )存在 ,核心盐度 34.5 8,位于 80 0- 90 0m水深之间。这是历次考察在该断面所不曾观测到的现象。断面上的锋面从南向北依次为南极陆坡锋 (ASF)、极锋 (PF)、亚南极锋 (SAF)和亚热带锋 (STF)。ASF位于 65°S以南的 1 0 0m以深 ,等温线和等盐线向南倾斜 ;PF位于 5 4°S ,90 .4°E ;SAF位于 45 .3°- 47.5°S ,1 0 2 .5°- 1 0 4 .4°E之间 ,深达整个测量深度 ,温度具有两个高梯度核心 ;首次在该断面观测到双STF结构 ,位于 41 .9°- 42 .6°S,1 0 6.7°- 1 0 7.3°E和 37.7°- 38     

斯瓦尔巴群岛冰川学研究进展与我国北极冰川监测系统建设

北极斯瓦尔巴群岛冰川大多数属于亚极地型(sub-polar)或多热型(polythermal)。Austre Br(?)ggerbreen和Midre Lovénbreen冰川(＜10km~2)长时间系列物质平衡研究显示,自小冰期结束以来几乎所有的观测年中夏季消融比冬季积累更大,导致冰体稳定地减小；而面积更大、海拔高度更高的冰川如Kongsvegen冰川(105km~2)则更加接近稳定态的平衡。斯瓦尔巴群岛冰川流动速率一般较低,但跃动相当频繁,控制跃动型冰川空间分布的因素包括冰川长度、基底岩性和多热场。可通过冰川水文特征、钻孔温度测量和无线电回波探测获取斯瓦尔巴群岛冰川热场的信息。斯瓦尔巴群岛冰川的低流速和多热性结构对冰川上的排水系统相当重要,整个群岛淡水径流的四个主要来源分别是冰川消融、雪融化、夏季降雨和冰崩解,经验回归方法和模式方法用于计算淡水径流量。因夏季融水渗浸作用、采样分辨率低和化学成分分析有限,早期斯瓦尔巴群岛冰芯的准确定年受到严重影响,但最近的研究显示,来自斯瓦尔巴群岛冰帽的冰芯数据仍然能够提供重要的气候和环境信息。通过我国北极黄河站2005年度科学考察,我们已初步建立了Austre Lovénbreen冰川和Pedersenbreen冰川监测系统,并计划在Austre Lovénbreen冰川进行钻孔温度测量、冰川气象要素观测、冰川前缘水文观测以及冰川厚度和内部结构测量,重点开展斯瓦尔巴群岛冰川基本特征和发育条件、冰川表面能量和物质平衡、冰川波动与气候变化关系、淡水径流年际和季节性变化和气/雪/冰界面过程等方面的研究。     

Erosion of Bedrock by Subglacial Meltwater, Soya Coast, East Antarctica

The formation of the glacial erosional bedforms at the Soya Coast of Lützow-Holm Bay, East Antarctica is discussed. The streamlined bedforms in the studied area are classified into crescentic transverse ridges and tadpole rocks, and these bedforms are accompanied by small erosional marks (s-forms) which suport the interpretation of subglacial meltwater erosion. Some tadpole rocks are superimposed on a large roche moutonnée, and these two kinds of landform are interpreted to have different modes of formation. Observations and interpretations of these bedforms are used to reconstruct the historical development of the glacial erosional bedforms, and to draw attention to the significance and implications of subglacial meltwater erosion on the marginal area of the Antarctic Ice Sheet in the past. An initial episode of glacial plucking and abrasion produced roches moutonnées and basic large-scale landforms. Subglacial meltwater flowing peiodically into the Lützow-Holm Bay sculptured s-forms and streamlined bedforms in bedrock over much of the area. During this period, except for water-flowing phases, ice again came in contact with the bedrock to form striations superimposed on the s-forms and the hillocks.     

Quantitative geomorphological analysis of drumlins in the Peterborough drumlin field,Ontario, Canada

Drumlins are enigmatic subglacial landforms that have been interpreted to form by a number of processes, including incremental accumulation of till, erosion of previously deposited sediment, catastrophic meltwater floods, and sediment deformation. However, relatively little is known about the controls on drumlin formation, such as spatially variable glacial processes or substrate characteristics, and how these controls may be identified from variations in drumlin morphology within a single drumlin field. This paper explores a computational method that allows identification of drumlins and extraction of their morphological characteristics from existing topographic digital data for a portion of the Peterborough drumlin field in Ontario, Canada. Spatial and non‐spatial analysis of the form and distribution of drumlins across the study area identifies drumlin characteristics such as size, elongation ratio, symmetry and long axis orientation and shows that drumlins are not randomly distributed across the region and their form characteristics have distinct regional trends. Kernel density analysis is used to identify the regional trends in drumlin characteristics. Factors that appear to influence the form and distribution of drumlins in the study area include sediment thickness, length of time beneath the ice, ice velocity and direction of ice movement. The distribution of particularly well developed asymmetric and elongate drumlins coincides with the location of a broad bedrock low and is interpreted to identify the former location of a fast‐flowing ice stream.     

南极洲乔治王岛柯林斯冰帽小冰穹顶冰芯数学模式初步断代

冰芯钻取后，样品截取原则和环境记录的初步解释要求对年代－深度剖面有一初步了解，即要求建立冰体随深度变化的时间尺度。根据柯林斯冰帽一年多野外实测资料所揭示的小冰穹运动状况、温度分布、物质平衡和动力学特征，本文采用Ｄａｎｓｇａｒｒｄ－Ｊｏｈｎｓｅｎ模型和等温冰体流动模型（ｎ＝３），分别对一支８０．２ｍ冰芯的时间尺度进行初步估算。结果表明两种模型断代结果非常接近，在距冰床１０ｍ深度处，两模型分别给出１８９７年和１８５４年的冰龄。对比指出两种模型计算出的冰帽各深度冰龄最大误差不大于２％。与冰芯中上部含深褐色火山灰冰层的历史记录年代相比误差小于３％。     

南极洲乔治王岛柯林斯冰帽的温度分布

钻孔内温度实测表明，柯林斯冰帽积累区大部分呈温性，消融区可能呈冷性。冰帽活动层温度明显受气温季节变化的影响，降水暖渗浸对冰的增温作用显著，雪盖对温度分布也显示了一定的影响。测量显示，冰帽纵深层的温度大都接近融点，而小冰穹顶附近十数米范围内温度变化较大。小冰穹顶附近，钻进时３０ｍ以下孔中出水现象显著，可能是冰内径流、差异运动和较高盐度等因素共同作用的结果。     

Thermal regime of a valley glacier, Erikbreen, northern Spitsbergen

The thermal regime of the valley glacier, Erikbreen, northern Spitsbergen (79°40'N, 12°30'E) was studied using radio-echo sounding and temperature measurements from eight boreholes ranging from 13.5 to 24 m. Radar images indicate a glacier with a two-layered thermal structure. A surface layer of cold ice, 20 to 60 m thick along the centre flow line, extends from an altitude above equilibrium line to the glacier front. This layer represents 20 to 35% of the glacier thickness, except at the floating front, where the cold layer is about 50%. The ice beneath the cold surface layer is interpreted to be temperate. Cold-based areas exist near the glacier margin and in some locations in the accumulation area; the ice is interpreted to be entirely temperate in central parts of the accumulation area at high altitude. Freezing of temperate ice at the base of the cold surface layer is probably the main mechanism of cold ice formation in the frontal parts of Erikbreen. Calculated heat fluxes based on the borehole measurements show that a steady state cold layer 25 to 30 m thick is likely, assuming a surface melting of 1.7 m/y and a maximum water content of 3%. In the frontal parts the calculated mean annual upward heat flux at 10 to 15 m depth is roughly 0.6 W/m².     

Coastal cliff temperatures related to the potential for cryogenic weathering processes, western Spitsbergen, Svalbard

The main purpose of this research was to measure the near surface ground temperatures and describe the main characteristics of the thermal regime of a sheltered arctic coastal cliff. Measurements were made near Ny-Alesund, western Spitsbergen, Svalbard (79°N, 12°E), in a transect across sediments on top of a coastal cliff, in a 8 m high coastal cliff and across the beach below the cliff. Temperatures were logged hourly from August 1987 to August 1988. A local snow cover of 1–4 m on the beach had a strong influence on surface heat exchange, and hence the dynamics of the ground thermal regime. Late winter temperatures in the cliff and backshore sediments were stable and ranged from -5°C to -9°C. At the first snow melt events in spring there was a large heat flux into the ground due to the release of latent heat from refreezing of meltwater. The interpretation of the temperature records leads to a discussion on some aspects of cryogenic weathering. The snow-melt period in spring and summer may be a period of rock fracturing, based on the model of segregation ice growth at subzero temperatures. Steep temperature gradients and available meltwater at the surface favor water migration in the heavily fractured dolomitic limestone even at the low hydraulic conductivities expected at below zero temperatures.     

The tunnel through Torghatten,northern Norway: Landforms and discussion of formation

The tunnel through the mountain of Torghatten, in northern Norway, is generally regarded as a product of wave action. The tunnel is above the late Weichselian marine limit. Fresh looking polished bedrock that resembles subglacial ice-sculptured and meltwater forms, p-forms, occurs near the opening to the landward eastern side of the tunnel and inside. Most likely, the tunnel is a polygenetic formation. Storm action during deglaciations and also subglacial meltwater drainage and plastically sliding ice during glaciations have been active processes in the formation of the tunnel.     

Annual Mass-balance Series of a Temperate Glacier in the Caucasus, Reconstructed from an Ice Core

Identification of annual layers in a firn/ice core provides a possibility to reconstruct the mass-balance sequence for glaciers where no direct observations have been carried out. A number of cores is obtained from the boreholes drilled on the Djantugan firn plateau in the crest zone (3620 m a.s.l.) of the Main Caucasus Ridge. A geophysical radar survey shows ice thickness here being equal to 212 m, close to the maximum value within the plateau (235 m). The deepest layer achieved, c .93 m below the surface, is dated back to 1937. Annual layers are identified by visual and textural petrographic analysis in situ . Geochemical and isotope methods are also applied. Ambiguities in discerning annual boundaries due to epigenetic firn/ice homogenization can be eliminated by means of complex methods. Since the probability of complete melting of an annual layer is estimated as negligible, the reconstructed continuous mass-balance time series, after inserting rheological and inclinometrical amendments, describe the character of glacier evolution. It is corroborated with indirect calculation using data from the nearest weather station and with mass-balance series of the neighbouring Djankuat Glacier, one of 10 reference glaciers in the world. Located south of the meganticlinorium axis, the boring site is characterized by glacier budget improvement during the last decades similar to the northern slope – less rapidly until the 1980s and more rapidly since.     

The Grayling Fingers region of Michigan: soils, sedimentology, stratigraphy and geomorphic development

This paper provides data on the landforms, soils, and sediments within a unique northern Michigan landscape known as the Grayling Fingers, and evaluates these data to develop various scenarios for the geomorphic development of this region. Composed of several large, flat-topped ridges that trend N–S, the physiography of the “Fingers” resembles a hand. Previously interpreted as “remnant moraines”, the Grayling Fingers are actually a Pleistocene constructional landscape that was later deeply incised by glacial meltwater. The sediments that comprise the Fingers form a generally planar assemblage, with thick (>100 m), sandy glacial outwash forming the lowest unit. Above the outwash are several meters of till that is remarkably similar in texture to the outwash below; thus, the region is best described as an incised ground moraine. Finally, a thin silty “cap” is preserved on the flattest, most stable uplands. This sediment package and the physiography of the Fingers are suggestive of geomorphic processes not previously envisioned for Michigan.Although precise dates are lacking, we nonetheless present possible sequences of geomorphic/sedimentologic processes for the Fingers. This area was probably a topographic high prior to the advance of marine isotope stage 2 (Woodfordian) ice. Much of the glacial outwash in the Fingers is probably associated with a stagnant, early Woodfordian ice margin, implying that this interlobate area remained ice-free and ice-marginal for long periods during stage 2. Woodfordian ice eventually covered the region and deposited 5–10 m of sandy basal till over the proglacial outwash plain. Small stream valleys on the outwash surface were palimpsested onto the till surface as the ice retreated, as kettle chains and as dry, upland valleys. The larger of these valleys were so deeply incised by meltwater that they formed the large, through-flowing Finger valleys. The silt cap that occupies stable uplands was probably imported into the region, while still glaciated. The Fingers region, a col on the ice surface, could have acted as a collection basin for silts brought in as loess or in superglacial meltwater. This sediment was let down as the ice melted and preserved only on certain geomorphically stable and fluvially isolated locations. This study demonstrates that the impact of Woodfordian ice in this region was mostly erosional, and suggests that Mississippi Valley loess may have indirectly impacted this region.     

Laboratory experiments and thermal calculations for the development of a next-generation glacier-ice exploration system: Development of an electro-thermal drilling device

A next-generation drilling system, equipped with a thermal drilling device, is proposed for glacier ice. The system is designed to penetrate glacier ice via melting of the ice and continuously analyze melt-water in a contamination-free sonde. This new type of drilling system is expected to provide analysis data in less time and at less cost than existing systems. Because of the limited number of parameters that can be measured, the proposed system will not take the place of conventional drilling systems that are used to obtain ice cores; however, it will provide a useful method for quickly and simply investigating glacier ice.An electro-thermal drilling device is one of the most important elements needed to develop the proposed system. To estimate the thermal supply required to reach a target depth in a reasonable time, laboratory experiments were conducted using ice blocks and a small sonde equipped solely with heaters. Thermal calculations were then performed under a limited range of conditions. The experiments were undertaken to investigate the effects of the shape and material of the drill head and heater temperature on the rate of penetration into the ice. Additional thermal calculations were then performed based on the experimental results.According to the simple thermal calculations, if the thermal loss that occurs while heat is transferred from the heater to ice (in melting the ice) is assumed to be 50%, the total thermal supply required for heaters in the sonde and cable is as follows: (i) 4.8 kW (sonde) plus 0 W (cable) to penetrate to 300 m depth over 10 days into temperate glacier ice for which the temperature is 0 °C at all depths and to maintain a water layer along 300 m of cable; (ii) 10 kW (sonde) plus 19–32 kW (cable) to penetrate to 1000 m depth over 1 month into cold glacier ice for which the temperature is −25 °C at the surface and 0 °C at 1000 m depth and to maintain a water layer along 1000 m of cable; and (iii) 19 kW (sonde) plus 140–235 kW (cable) to penetrate to 3000 m depth over 2 months into an ice sheet for which the temperature is −55 °C at the surface and 0 °C at 3000 m depth and to maintain a water layer along 3000 m of cable. The thermal supply required for the cable is strongly affected by the thickness of the water layer, cable diameter, and the horizontal distance from the ice wall at which the ice temperature was maintained at its initial temperature. A large thermal supply is required to heat 3000 m of cable in an ice sheet (scenario (iii) above), but penetration into glacier ice (scenarios (i) and (ii) above) could be realistic with the use of a currently employed generator.     

Sedimentological and stratigraphic investigations of a sequence of 106 varves from glacial Lake Assiniboine,Saskatchewan

Sediments retrieved from a long core on the floor of glacial Lake Assiniboine, Saskatchewan, expose 106 couplets, consisting of thick, light coloured, silt-rich beds and thin, dark, clay-rich beds. The couplets contain sharp lower and upper contacts of the silt bed, silty and clayey laminations within both the silt and clay beds, and ice-rafted debris in the silt beds, which are features characteristic of glacial varves.Seasonal variations in runoff are reflected in grain size profiles of individual silt beds in the varves. Mean grain size maxima in the lower portion of the silt bed suggest that snow accumulation during the previous winter had been substantial and that a warm spring combined with a rapid melting rate generated significant volumes of nival meltwater runoff. Coarse laminae higher in the silty part of the couplet imply that substantial meltwater inflow was produced by summer melting of glacier ice.Vertical trends in clay bed thicknesses, silt bed thicknesses, and total couplet thicknesses were strongly influenced by the proximity of meltwater inflow channels and lake depth. These interpretations, and correlation of the core to varve exposures at the surface, formed the framework for a paleohydrological reconstruction. Close to 11,000 BP, ice dammed the outlet of glacial Lake Assiniboine and the water depth rose about 2 m yr^–1. Eventually the lake became deep enough for couplets to form. Varve years 1–40 contain thick clay beds, silt beds, and couplets as a result of the proximal inflow of meltwater. A decline in silt bed and couplet thicknesses from varve years 41–85 occurred in response to ice retreat and more distal inflow. Varve deposition ceased in the shallow part of the basin probably because underflow currents from the distal source were redirected. Varve years 86–106 are distinguished by an increase in silt bed and couplet thicknesses and a decrease in clay bed thickness caused by a reduction in water depth and a return to proximal inflow. Varved sedimentation terminated when Lake Assiniboine drained through the Assiniboine valley to Lake Agassiz.