Distribution of borehole temperature at four high-altitude alpine glaciers in Central Asia

The distribution of borehole temperature at four high-altitude alpine glaciers was investigated. The result shows that the temperature ranges from -13.4℃ to -1.84℃, indicating the glaciers are cold throughout the boreholes. The negative gradient （i.e., the temperature decreasing with the increasing of depth） due to the advection of ice and climate warming, and the negative gradient moving downwards relates to climate warming, are probably responsible for the observed minimum temperature moving to lower depth in boreholes of the Gyabrag glacier and Miaoergou glacier compared to the previously investigated continental ice core borehole temperature in West China. The borehole temperature at 10m depth ranges from -8.0℃ in the Gyabrag glacier in the central Himalayas to -12.9℃ in the Tsabagarav glacier in the Altai range. The borehole temperature at 10 m depth is 3-4 degrees higher than the calculated mean annual air temperature on the surface of the glaciers and the higher 10 m depth temperature is mainly caused by the production of latent heat due to melt-water percolation and refreezing. The basal temperature is far below the melting point, indicating that the glaciers are frozen to bedrock. The very low temperature gradients near the bedrock suggest that the influence of geothermal flux and ice flow on basal temperature is very weak. The low temperature and small velocity of ice flow of glaciers are beneficial for preservation of the chemical and isotopic information in ice cores.     

2000—2014年喀喇昆仑山音苏盖提冰川表面高程变化

喀喇昆仑山区冰川由于存在正物质平衡或跃动、前进现象,被称之为“喀喇昆仑异常”,不过该地区冰川变化差异显著,尤其是大型表碛覆盖冰川,呈现与其他类型冰川明显的差异性响应,为理解喀喇昆仑冰川异常的机理,冰川尺度的详细变化研究十分必要。音苏盖提冰川位于喀喇昆仑山乔戈里峰北坡,是中国面积最大的冰川,是典型的大型表碛覆盖冰川。通过应用TanDEM-X/TerraSAR-X（2014年2月）与SRTM-X DEM（2000年2月）的差分干涉测量方法计算音苏盖提冰川表面高程变化,并结合冰川表面流速对冰川表面高程变化和跃动进行分析和讨论。结果表明：2000—2014年音苏盖提冰川表面高程平均下降了1.68±0.94 m,即冰川整体厚度在减薄,年变化率为-0.12±0.07 m·a^-1。冰川表面高程变化分布不均,其中南分支（S）冰流冰川整体减薄较为显著,冰川南分支冰流运动速度较快,前进/跃动的末端占据了冰川的主干,阻滞原主干冰川物质的向下运移（跃动）,导致原主干冰舌表面高程上升;冰川厚度减薄随着海拔升高先下降后保持稳定,同时呈现一定的波动性;低海拔表碛区域消融大于裸冰区,可能存在较薄表碛,因热传导高、覆盖大量冰面湖塘和冰崖存在,加速了冰川消融;在坡度小于30 °的区域,冰川厚度减薄随着坡度的减小而加剧;坡向朝南冰川厚度略微增加（0.01 m）,西南坡向冰川厚度略微减薄（-0.03 m）,其他坡向冰川厚度减薄明显。近14 a来,表碛覆盖的音苏盖提冰川表面高程整体下降表明物质处于亏损状态,冰川跃动导致局部冰川表面高程的增加。     

祁连山老虎沟12号冰川消融区不同天气条件下的能量收支特征

冰川表面能量平衡模型建立了冰川与大气之间的联系。为探讨不同天气条件对冰川能量收支的影响, 利用祁连山老虎沟12号冰川海拔4 550 m处的气象资料（2011年8月24日 - 9月6日）, 结合能量平衡模型, 分析了不同天气条件下的能量收支变化特征。结果表明： 受云量影响, 晴天条件下向下短波辐射（318.3 W·m^-2）是多云条件下的1.5倍, 是阴天条件下的3倍。三种天气条件下的向下长波辐射, 晴天（215.4 W·m^-2）<多云（267.4 W·m^-2）<阴天（291.6 W·m^-2）。受固态降水的影响, 阴天条件下冰川反照率（0.50）是晴天时的2倍多。而三种天气下的最大消融耗热, 晴天（739.6 W·m^-2）>多云（582.8 W·m^-2）>阴天（324.5 W·m^-2）。在能量收入项中, 净短波辐射是主要来源（98%）, 但是受天气条件影响, 能量支出各项所占比例有明显差异; 在三种天气条件下, 净长波辐射所占比例分别为35%、 31%和23%, 消融耗热所占比例分别为62%、 64%和75%, 潜热通量所占比例相差不大。     

大陆型山谷冰川冰震的规律和影响因素——以老虎沟12号冰川为例

2015年10月,利用便携式宽频带地震仪在祁连山老虎沟12号冰川上进行了9 d的冰震观测,在台站的震动信号中识别出大量与冰川动态特性相关的冰震。根据信号的频率等特征,可将其分为短周期冰震和长周期冰震。短周期冰震的持续时间大多在0.1 s以下,频谱集中在20~100 Hz之间,其数量可达每天6 600个,占所检测到冰震的绝大部分。长周期冰震持续时间可达几十秒至数小时,其地震波形频率集中在0.1~10 Hz,观测期间检测到296次长周期冰震。对比冰震发震时间和当地气温发现:气温下降,短周期冰震事件数量快速增加;气温升高,短周期冰震数量逐渐减少。短周期冰震的发震时间分布呈现出以1 d为周期变化的特征。利用麦克斯韦模型模拟的冰川在气温影响下的应力变化可以解释观测到的冰震日变性:当气温下降,冰川温度下降,冰体积收缩并产生应变,相应的拉张应力使得冰裂隙破裂而产生短周期冰震信号。     

美国蒙大拿州冰川国家公园冰缘条带形地表植物功能属性和土壤微生物随坡位变化（英文）

The retreating snowfields and glaciers of Glacier National Park, Montana, USA, present alpine plants with changes in habitat and hydrology. The adjacent and relic periglacial patterned ground consists of solifluction terraces of green, vegetation-rich stripes alternating with sparsely vegetated brown stripes. We established georeferenced transects on striped periglacial patterned ground for long-term monitoring and data collection on species distribution and plant functional traits at Siyeh Pass and at Piegan Pass at Glacier National Park. We documented species distribution and calculated the relative percent cover(RPC) of qualitative functional traits and used 16 S rRNA from soil samples to characterize microbial distribution on green and brown stripes. Plant species distribution varied significantly and there were key differences in microbial distribution between the green and brown stripes. The rare arctic-alpine plants Draba macounii, Papaver pygmaeum, and Sagina nivalis were restricted to brown stripes, where the RPC of xeromorphic taprooted species was significantly higher at the leading edge of the Siyeh Pass snowfield. Brown stripes had a higher percentage of the thermophilic bacteria Thermacetogenium and Thermoflavimicrobium. Green stripes were co-dominated by the adventitiously-rooted dwarf shrubs Salix arctica and the possibly N-fixing Dryas octopetala. Green stripes were inhabited by Krummholz and seedlings of Abies lasiocarpa and Pinus albicaulus. Prosthecobacter, a hydrophilic bacterial genus, was more abundant on the green stripes, which had 6,524 bacterial sequences in comparison to the 1,183 sequences from the brown stripes. While further research can determine which functional traits are critical for these plants, knowledge of the current distribution of plant species and their functional traits can be used in predictive models of the responses of alpine plants to disappearing snowfields and glaciers. This research is important in conservation of rare arctic-alpine species on periglacial patterned ground.     

Glacier Extent and Volume Change （1966-9000） on the Su-lo Mountain in Northeastern Tibetan Plateau,China

The topographic maps of 1：50, 000 scales, aerial photographs taken in 1966, one Landsat image taken in 1999, and SRTM data from 2000 were used to quantify the losses in area and volume of the glaciers on the Su-lo Mountain, in the northeastern Tibetan Plateau, China in the past 30 years. The total glacier area decreased from 492.9 km^2 in 1966 to 458.2 km^2 in 1999. The volume loss of the studied glaciers reached 1.4 km^3 from 1966 to 2000. This agrees with documented changes in other mountain glaciers of the whole Tibetan Plateau.     

Effective Sample Size for Glacier Mass Balance

Correlograms from multiple time series of point mass balance, measured on White Glacier (Axel Heiberg Island, Canada) and Abramov Glacier (Alai Range, Kirgizia), show that the correlation decreases with the difference in elevation between the points. The correlogram is used to calculate an integral spatial scale or effective sample area which, when divided into the area of the glacier, yields an estimate of the number of degrees of freedom in a stake-based estimate of the whole-glacier balance. This number – the 'effective sample size'– is a small fraction of the number of point measurements; indeed, it is independent of the number of measurements. Estimates of average balance for elevation bands are at one remove from raw stake measurements, but they are amenable to a principal component analysis which confirms that the effective sample size is very small. The small effective sample size means that uncertainty in a typical measurement of whole-glacier mass balance cannot be much less than the large value implied by the conservative assumption that stakes are perfectly correlated. One way around this difficulty would be to increase the role of prior physical understanding by seeking to model the spatial variability of mass balance. A successful model would need only a few parameters, and would allow for the joint estimation of both magnitude and uncertainty; the uncertainty in mass balance could be derived objectively from the uncertainty in the parameters. This, however, would require good estimates of the variability of mass balance at the elevation-band scale, which might in turn require that many measurement networks be redesigned.     

Cyclic sedimentation produced by fluctuations in meltwater discharge, tides and marine productivity in an Alaskan fjord

Glacimarine sediment deposited in the fjord adjacent to Muir Glacier in south-eastern Alaska consists of rhythmically laminated muds, stratified sandy mud, sand and gravelly mud facies. Cyclicity is recorded by gravelly mud facies deposited during winter by ice-rafting, black mud laminae formed by spring plankton blooms and variations in tidal rhythmite thickness and texture produced by the interaction of meltwater discharges and tidal currents in the macrotidal fjord. Regular cyclicity in laminae thickness is tested statistically by Fourier transform and can be attributed to a lunar tidal cycle control in the five cores collected up to 6 km from the sediment source. Cores close to the source can have additional laminae as a result of discharge fluctuations, and distal cores may lack full cycles because of variability in the plume path and attenuation with distance. Cyclic variations in sediment texture are recorded in magnetic susceptibility (MS) profiles of the cores. High MS values are produced by turbidite sand beds or by stratified sandy mud deposited by overflow plumes during peak summer meltwater discharge. Low values reflect muddy intervals deposited during periods of low meltwater discharge, such as during autumn and winter. Sediment accumulation rates measured by ²¹⁰Pb dating range from 82 cm year^–1, 2 km from the sediment source at the head of the fjord, to 16 cm year^–1, 6 km away. These rates are within the same range as average sediment accumulation rates determined from cyclic seasonal markers within the cores. These data show that, with careful documentation, annual cycles of glacimarine sediment accumulation can be detected within marine cores. Cores collected from the distal portion of the basin were deposited during the transition of Muir Glacier from a tidewater terminus ending in deep water to a terrestrial glacier with an ice-contact delta deposited in front of the terminus. This transition is recorded by a coarsening-upward sedimentary sequence formed by turbidite sands originating from the prograding delta above fine-grained, laminated basin fill deposited by turbid overflow plumes.     

梅里雪山明永冰川的特征与变化

梅里雪山主峰卡格薄峰海拔６７４０ｍ,位于怒江与澜沧江之间,是尚未被人类征服的神秘高峰之一。位于卡格薄峰东坡的明永冰川,长１１．７ｋｍ,冰川末端海拔２６６０ｍ,是目前横断山区第二条较长的冰川。这是一条横断山区海拔最低的季风海洋性冰川,其冰舌上部运动速度可达５３３ｍ／ａ。１９７１￣１９８２和１９９８年冰川均处于前进状态。     

近30年来乌鲁木齐河流域冰川波动特征与流域高山带升温幅度的 …

乌鲁木齐河流域典型冰川与全流域其他冰川波动的监测结果表明,５０年代末与６０年代初以来,各冲川均处于全面退缩状态,且冰川长度退缩量,面积和冰储量减小量与冰川的规模有密切的关系,大冰川退缩量大,但退缩量所占百分比较小,小冰川则相反,而且三者与冲川的长度等级有较好的统计关系。