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1.
Landsat multispectral scanner images and 1:50, 000 scale aerial photographs are used to measure marginal fluctuations in 22 outlet glaciers of the Nordaustlandet ice caps, Svalbard, for all or parts of the period 1969 to 1981. Little was previously known about the behaviour of these glacier termini. Digital analysis of Landsat computer compatible tapes yielded measurement errors of less than ±150m, whereas data extracted from aerial photographs had an accuracy of ±25 m. Of the 22 glacier termini examined using aerial photographs, 15 were retreating, four were static and three were advancing. Retreat was usually in the order of hundreds of metres during the period of observation. For any outlet glacier, retreat was probably a result of either (1) glacier response to climatic wanning since the early part of the 20th century, or (2) stagnation and thinning during the quiescent period between surges. Short term iceberg calving events may also be responsible for retreat in a few cases. All observed outlet glaciers of Austfonna were static or retreating between 1969 and 1981, but analysis of Landsat imagery and aerial photographs showed that five outlet glaciers from Vestfonna and one from Vegafonna were advancing for all or part of that period. Bodleybreen advanced by a mean of 440 and a maximum of 580m a−1 between 1976 and 1981. Bodleybreen, Søre Rijpbreen, and Palanderbreen are identified as surging, based on increases or changes in the pattern of surface crevassing. The ice streams Aldousbreen, Frazerbreen, and Idunbreen also advanced between 1976 and 1981, but surface crevasse patterns remained largely unaltered and surging is not inferred.  相似文献   

2.
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。  相似文献   

3.
The Characteristics and Formation of A High-Arctic Proglacial Icing   总被引：1，自引：0，他引：1  
Well‐known from permafrost hydrology, icings (naled or Aufeis) are also frequently encountered at the margins of high‐latitude glaciers. The morphology of a proglacial icing at Scott Turnerbreen in the Norwegian Arctic archipelago of Svalbard is described, and the process of formation is considered in detail. Ground thermal‐regime modelling indicates an equilibrium permafrost depth of at least 200 m in the studied catchment, and it appears unlikely that groundwater contributes to icing formation. Meltwater flow through ice‐marginal drainage channels is accompanied by estimated heat fluxes of up to about 190 W m?2, suggesting that stored meltwater may continue to percolate through thawed sub‐channel sediments when surface runoff is absent during winter. A hydraulic conductivity of 6.9 × 10?3 m s?1 is implied, which is consistent with other studies of glacier drainage systems. The long residence time of winter‐draining meltwater, and solute rejection by refreezing water, account for high observed concentrations of solute in interstitial water in the icing. It has often been asserted that the presence of a proglacial icing indicates that a glacier is polythermal. However, as Scott Turnerbeen is entirely non‐temperate, the presence of an icing cannot always be treated as a reliable guide to the thermal regime of a glacier.  相似文献   

4.
对位于北极Svalbard群岛新奥尔松(Ny-lesund)的Austre Lovénbreen和Pedersenbreen冰川首个物质平衡年(2005/06年度)的冰川表面物质平衡及其运动特征进行研究,并阐述了Austre Lovénbreen冰川末端位置的变化状况。结果表明:(1)Austre Lovénbreen和Pedersenbreen冰川净物质平衡分别为-0.44和-0.20m w.e.,年消融量分别为0.99和0.94m w.e.,对应冰川零平衡线高度分别为478.10和494.87m。(2)两条冰川符合Svalbard地区跃动冰川运动的特征模式。运动速度矢量的水平分量表现为:向主流线辐合或平行于主流线。下游运动速度较慢,而在中上游运动相对较快。Austre Lovénbreen冰川表面各观测点的运动速度平均值为2.28m·a-1,运动速度最大值和最小值分别为3.91和0.81m·a-1;Pedersenbreen冰川表面观测点运动速度平均值为6.74m·a-1,运动速度最大值和最小值分别为8.13和5.49m·a-1。运动速度矢量的垂直分量表现为:消融区冰川消融量随海拔升高而减弱,Austr...  相似文献   

5.
To improve our understanding of Svalbard-type polythermal glacier drainage, hydraulic geometry models of the subglacial hydrology of two contrasting glaciers in Svalbard have been constructed. The models are tested against a uniquely long and rich set of field observations spanning 45 years. Digital elevation models (DEMs) were constructed from bedrock data measured with ground penetrating radar and surface data of two medium-sized polythermal glaciers, Hansbreen and Werenskioldbreen, in south-west Spitsbergen. Hansbreen has a low angle bed with over-deepenings and a calving front, while Werenskioldbreen has steeper bed and terminates on land. Together they are representative of many Svalbard glaciers. The DEMs were used to derive maps of hydraulic potential and subglacial drainage networks. Validation of the models was done using field observations including location mapping and speleological exploration of active moulins, positions of main river outflows, dyetracing and water chemistry studies, and observations of water pressure inside moulins. Results suggest that the water pressure is generally close to ice overburden pressure but varies greatly depending on local conditions such as bed location, the thickness of cold ice layer, the thickness of the glacier and seasonal changes in meltwater input.  相似文献   

6.

The results presented show how glacier velocities can be measured and calculated from Earth Resources Satellite (ERS) tandem interferometric synthetic aperture radar (InSAR) data by the use of geographical information systems (GIS) and non-interferometric software. A semi-automatic algorithm using existing and newly implemented modules in ESRI's GIS software Arc has been developed to unwrap existing height differentiated interferometric SAR (DInSAR) data. The algorithm is applied to a data set covering glaciers from the arctic archipelago Svalbard. Estimated DInSAR velocities are decomposed into the glacier surface flow direction using a digital elevation model (DEM). Velocity fields for the glaciers Isachsenfonna, Akademikerbreen and Nordbreen on Svalbard are presented.  相似文献   

7.
The identification of surge activity is important in assessing the duration of the active and quiescent phases of the surge cycle of Svalbard glaciers. Satellite and aerial photographic images are used to identify and describe the form and flow of Perseibreen, a valley glacier of 59 km2 on the east coast of Spitsbergen. Heavy surface crevassing and a steep ice front, indicative of surge activity, were first observed on Perseibreen in April 2002. Examination of high resolution (15 m) Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery confirmed this surge activity. Perseibreen retreated by almost 750 m between 1961 and 1990. Between 1990 and the summer of 2000, Perseibreen switched from retreat and its front began to advance. Rapid advance was underway during the period June 2000 to May 2001, with terminus advance at over 400 m yr−1. Between May and August 2001 the rate increased to over 750 m yr−1. The observed crevasse orientation indicates that ice was in longitudinal tension, suggesting the down-glacier transfer of mass. Ice surface velocities, derived from image correlation between ASTER images, were 2-2.5 m d−1 between May and August 2001. The glacier was flowing at a relatively uniform speed with sharp velocity gradients located close to its lateral margins, a velocity structure typical of ice masses in the active phase of the surge cycle. The stress regime is extensional throughout and the surge appears to be initiated low on the glacier. This is similar to the active-phase dynamics of other Svalbard tidewater glaciers. Perseibreen has probably been inactive since at least 1870, a period of about 130 years to the present surge which defines a minimum length for the quiescent phase.  相似文献   

8.
Svensson, Harald, 1976; Relict ice-wedge polygons revealed on aerial photographs from Kaltenkirchen, northern Germany. Geografisk Tidsskrift 75: 8–12. København, juni 1, 1976.

On aerial photographs polygonal patterns are detected in cultivated fields due to vegetational contrasts. In a section through the ground the structure and composition of the material were studied. The outline of the ice-wedge cast is very faint, hut the existing structure and soil qualities are sufficient to make the polygonal network show on the ground surface. The season of the year and the external conditions at the time of photographing are of great importance for a distinct reproduction of the pattern in the aerial photograph.  相似文献   

9.
Two small high-Arctic glaciers (Longyearbreen and Larsbreen) on Svalbard (78°N 15°E) were studied with respect to glaciological and hydrological characteristics. Fieldwork during the melting season of 1993 and 1994 was coupled with digital map analysis based on high-resolution digital elevation models (DEM) to reveal the dynamics and temperature regime of small glaciers in a high-Arctic environment, and its relationship to the material transport and sedimentation of these glaciers. The study showed Longyearbreen and Larsbreen to be low activity glaciers, cold-based with temperate patches, and thus having a low potential of basal erosion. The transport of ions and suspended solids in the glacial meltwater implies storage of material in and around the glacier which comes into contact with the meltwater. The study suggests that small Arctic glaciers couple the slope system with the fluvial system and therefore build a highly effective denudation system. Small polythermal glaciers are therefore important in understanding Pleistocene and Holocene landform development in cold regions.  相似文献   

10.
We examine the types of icings (aufeis) in the river basins of Primorski Krai. An assessment is made of the conditions for their formation in autumn and winter and for their decay in the spring-summer time. Depending on the type of icings, we identified the character of their impact on the main components of landscape: relief, hydrological regime of streams, soil, vegetation, etc. The emphasis in this study is on the icing formations in the zone of seasonally frozen earth materials and, to a lesser extent, in areas of permafrost islands.  相似文献   

11.
Glaciers in Svalbard: mass balance, runoff and freshwater flux   总被引：4，自引：1，他引：4  
Gain or loss of the freshwater stored in Svalbard glaciers has both global implications for sea level and, on a more local scale, impacts upon the hydrology of rivers and the freshwater flux to fjords. This paper gives an overview of the potential runoff from the Svalbard glaciers. The freshwater flux from basins of different scales is quantified. In small basins (A < 10 km2), the extra runoff due to the negative mass balance of the glaciers is related to the proportion of glacier cover and can at present yield more than 20% higher runoff than if the glaciers were in equilibrium with the present climate. This does not apply generally to the ice masses of Svalbard, which are mostly much closer to being in balance. The total surface runoff from Svalbard glaciers due to melting of snow and ice is roughly 25 ± 5 km3 a−1, which corresponds to a specific runoff of 680 ± 140 mm a−1, only slightly more than the annual snow accumulation. Calving of icebergs from Svalbard glaciers currently contributes significantly to the freshwater flux and is estimated to be 4 ± 1 km3 a−1 or about 110 mm a−1.  相似文献   

12.
Using three key areas as an example we examine the tendencies toward changes of the mountain geosystems in southern Siberia caused by fluctuations of climate. Presented are the quantitative parameters of the dynamics of nival-glacial geosystems (glaciers, perennial snow clusters, icings, and stony glaciers). Portions of large-scale maps for the key areas generated for a subsequent monitoring of the mountain geosystems are presented.  相似文献   

13.
The cumulative net mass balances of maritime glaciers in Norway display a net surplus during the period 1963–2000. The article seeks to establish the causal mechanisms that resulted in the positive net balances occurring on Norwegian maritime glaciers. To achieve this, a Temporal Synoptic Index (TSI) was derived for a 30-year period for a number of synoptic meteorological stations in Norway. The TSI is derived using Principal Components Analysis (PCA) and subsequent clustering of component scores to classify days for both winter and summer seasons. Findings indicate that the occurrence of ‘warm’ type air masses during the summer months have increased in frequency, particularly since the late 1980s. A reduction in the frequency of ‘cold’ cluster types during the winter months is evident after this period, while the frequency of ‘warm’ types, with an increased moisture carrying capacity, has increased in frequency. The frequency occurrence of these key air mass types is shown to be significantly related to glacier mass balance during both the accumulation and ablation season. Winter air mass types from maritime source regions act to enhance accumulation and suppress ablation, while summer continental source types suppress accumulation and enhance ablation.  相似文献   

14.
The retreat of 293 glaciers in the Tien Shan Mountains (Kyrgyz Republic) from their maximum extent during the Little Ice Age (LIA) is estimated using aerial photographs from 1980 to 1985 and maps at a scale of 1:25000, constructed during period 1956–1990. Two indices of changes are used: the linear distance from the glacier terminus to its Little Ice Age moraine and the difference in absolute elevation of the terminus and the moraine. Historical information about the front positions of glaciers in the 1880s to the 1930s was used as an indirect control of remote sensing data. The age of moraines in key regions was estimated by lichenometry. On average, Tien Shan glaciers have retreated by 989 ± 540 m since the LIA maximum. Their front elevations (dh) rose by 151 ± 105 m. These changes are similar to changes observed in the Alps and western Norway, Pamir‐Alay and Koryak plateau, but greater than in east Siberia over the same interval. Differences between four regions in Tien Shan (northern, western, inner, central) are generally small, though in the northern Tien Shan the glacier retreat and frontal rise are more prominent (1065 ± 479 m and 215 ± 140 m, respectively).  相似文献   

15.
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16.
As in previous years Norsk Polarinstitutt has carried out mass balance investigations on Storbreen and Hardangerjøkulen in mainland Norway and on Broggerbreen and Lovenbreen in Svalbard. More than 20 years of measurements show that the glaciers both in mainland Norway and in Svalbard are retreating.
Both in 1985 and in 1986 the glaciers in Norway had a negative net balance. At Storbreen the mean annual net balance value 1949-86 is -0.30 m in water equivalents, while on Hardangerjflkulen the mean value 1963-86 is -0.02 m.
The two glaciers measured in Svalbard also had negative net balance in 1985 and in 1986. Both measured glaciers have had negative balance nearly all years since the measurements started in 1966. The mean value is close to -40g/cm2 or -0.4 m on both.  相似文献   

17.
Glacier Benito is a temperate outlet glacier on the west side of the North Patagonian Icefield. Rates of thinning and ablation were obtained using data collected by the British Joint Services Expedition in 1972/73 and subsequent data collected in 2007 and 2011. Ice‐front recession rates were based on dendrochronological dating for the terminal moraines and aerial and satellite imagery of the ice front in 1944, 1998 and 2002. Between the first Benito survey in 1973 and 2007, the lower glacier thinned by nearly 150 m at an average rate of 4.3 m yr?1 with the rate increasing to 6.1 m yr?1 between 2007 and 2011, a 28.7% increase during the latter period. Increases in ice movement and ablation were negligible: ice movement for 1973 and 2007 averaged 0.45 m day?1 and ablation averaged 0.05 m day?1. Ice front recession along the glacier's centre line from 1886 to 2002 was approximately 1860 m. Retreat rates between 1886 and 1944 averaged 8.9 m yr?1. Thereafter glacier asymmetry makes measurement along the glacier centre line unrepresentative of areal change until 1998 when symmetry was restored; retreat between 1944 and 1998 was 15.4 m yr?1. From 1998 to 2002 the rate increased dramatically to 127.2 m yr?1. Recession from the southern end of Benito's terminal moraine in the 1850s supports an early date for initial retreat of the Icefield's glaciers.  相似文献   

18.
By stepwise regression analysis the accumulation, ablation, and equilibrium line altitude (ELA) were modelled by circulation indices and spring‐summer temperature on six Norwegian glaciers (Ålfotbreen, Nigardsbreen, Rembesdalsskåka, Storbreen, Hellstugubreen and Gråsubreen). The circulation indices were derived from a gridded monthly mean sea level pressure (MSLP) data set, whereas temperature series were derived from instrumental and proxy data. Analyses showed that accumulation on the western glaciers was strongly related to western airflow perpendicular to the main mountain range releasing precipitation on the glaciers. No other airflow variable significantly improved the regression. For the continental glaciers, circulating air in connection with low pressure systems was also found to be important. This may explain the lack of synchronicity in the glaciers' development in southern Norway during the Holocene. Accumulation was better modelled using the MSLP data set than by using the North Atlantic Oscillation (NAO) index as predictor. The decadal variations of accumulation, ablation, and ELA were analysed by a Gaussian low pass filter. The well‐known abundant accumulation on Norwegian glaciers during the early 1990s turned out to be unprecedented during the entire series (since 1781), whereas the accumulation of the 1960s has not been lower since the early 19th century according to model results. Ablation increased significantly from the mid‐19th century to the 1930s. The ablation maximum during the 1930s has not yet been exceeded. Also the 1930s show extremely high ELA values.  相似文献   

19.
In mainland Norway, mass balance measurements were carried out on the Hardangerjøkulen and Storbreen glaciers. Both had a small negative net balance. The two glaciers measured in Svalbard, Broggerbreen and Lovgnbreen, also had negative balances as in the previous 19 years. Length fluctuations measured at eight glacier tongues indicate that one was advancing, one in equilibrium, and six were retreating.  相似文献   

20.
Jakobshavns Isbræ in West Greenland (terminus at ≈69° 10′ N/50° W), a major outlet glacier of the Greenland Ice Sheet and a continuously fast-moving ice stream, has long been the fastest moving and one of the most productive glaciers on Earth. It had been moving continuously at speeds of over 20 m/day with a stable front position throughout most of the latter half of the twentieth century, except for relatively small seasonal changes. In 2002, the ice stream apparently suddenly entered a phase of rapid retreat. The ice front started to break up, the floating tongue disintegrated, and the production of icebergs increased. In July 2005, we conducted an extensive aerial survey of Jakobshavns Isbræ to measure and document the present state of retreat compared to our previous field observations since 1996. We use an approach that combines structural analysis of deformation features with continuum mechanics to assess the kinematics and dynamics of glaciers, based on aerial imagery, satellite data and GPS measurements. Results from interpretation of ERS-SAR and ASTER data from 1995 to 2005 in combination with aerial imagery from 1996 to 2005 shed light on the question of changes versus stability and their causes in the Jakobshavns Isbræ dynamical system. The recently observed retreat of Jakobshavns Isbræ is attributed to climatic warming, rather than to an inherent change in the glaciodynamic system. Close to the retreating front, deformation structures are characteristic of extension and disintegration. Deformation provinces that do not border the retreating front have had the same deformation characteristics throughout the past decade (1996–2005).  相似文献   

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