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1.
Surface velocities have been regularly monitored at the rock glacier in Outer Hochebenkar, Ötztal Alps, Austria since the early 1950s. This study provides an update to previously published surface velocity time series, showing mean profile velocities of four cross profiles since the beginning of the measurements (1951,1954, 1997; depending on the profile), as well as single block displacements from 1998 to 2015. Profiles P1, P2 and P3 have moved between 42 and 90 m, at mean velocities between 0.70 and 1.48 m yr–1, since they were first established in the early 1950s (1951/54). Profile P0, established in 1997, has since moved 13 m or 0.75 m yr–1. An acceleration can be observed at all profiles since the late 1990s, with a particularly sharp velocity increase since 2010. All profiles reached a new maximum velocity in 2015, with 1.98 m yr–1 at the slowest profile (P0) and 6.37 m yr–1 at the fastest profile (P1). Year‐to‐year variations in profile velocities cannot be clearly attributed to inter‐annual variations of climatic parameters like mean annual air temperature, summer temperature, positive degree days, or precipitation. However, higher correlation is found between velocities and cumulative anomalies of air temperature (mean annual air temperature and positive degree days) and summer precipitation, suggesting that these parameters play a key role for the movement of the rock glacier. The lower profiles (P0, P1) show more pronounced year‐to‐year variations than the upper profiles (P2, P3). It is considered likely that processes other than climatic forcing (e.g. sliding, topography) contribute to the different velocity patterns at the four profiles.  相似文献   

2.
The Sachette rock glacier is an active rock glacier located between 2660 and 2480 m a.s.l. in the Vanoise Massif, Northern French Alps (45° 29′ N, 6° 52′ E). In order to characterize its status as permafrost feature, shallow ground temperatures were monitored and the surface velocity measured by photogrammetry. The rock glacier exhibits near‐surface thermal regimes suggesting permafrost occurrence and also displays significant surface horizontal displacements (0.6–1.3 ± 0.6 m yr–1). In order to investigate its internal structure, a ground‐penetrating radar (GPR) survey was performed. Four constant‐offset GPR profiles were performed and analyzed to reconstruct the stratigraphy and model the radar wave velocity in two dimensions. Integration of the morphology, the velocity models and the stratigraphy revealed, in the upper half of the rock glacier, the good correspondence between widespread high radar wave velocities (>0.15–0.16 m ns–1) and strongly concave reflector structures. High radar wave velocity (0.165–0.170 m ns–1) is confirmed with the analysis of two punctual common mid‐point measurements in areas of exposed shallow pure ice. These evidences point towards the existence of a large buried body of ice in the upper part of the rock glacier. The rock glacier was interpreted to result from the former advance and decay of a glacier onto pre‐existing deposits, and from subsequent creep of the whole assemblage. Our study of the Sachette rock glacier thus highlights the rock glacier as a transitional landform involving the incorporation and preservation of glacier ice in permafrost environments with subsequent evolution arising from periglacial processes.  相似文献   

3.
Flow rates for rock glaciers in the European Alps have been monitored using photogrammetric techniques; however, a program has not been initiated for similar Front Range, USA, rock glaciers. Horizontal rock glacier displacements were measured by tracking large surficial rocks on temporal orthophotos from 1978, 1990, and 1999. Vertical change was measured by creating digital elevation models (DEMs) from digital stereopairs, then subtracting elevations to detect change. Long‐term horizontal velocities ranged from 14 to 20 cm/yr on average, although uncertainty ranged from 4 to 5 cm/yr. On average, vertical elevation changes were negligible with most rock glaciers exhibiting a slight growth or thinning (1–2 cm/yr). Over shorter time scales (c. 10‐year periods), horizontal velocities have only increased by about 2 cm/yr. Because horizontal and vertical change is minimal, Front Range rock glaciers appear to be adjusted with current climate, unlike some rock glaciers in the European Alps that have shown increasing subsidence rates or significant increasing or decreasing horizontal velocities.  相似文献   

4.
Groundwater in front of warm‐based glaciers is likely to become a more integrated part of the future proglacial hydrological system at high latitudes due to global warming. Here, we present the first monitoring results of shallow groundwater chemistry and geochemical fingerprinting of glacier meltwater in front of a warm‐based glacier in Southeast Greenland (Mittivakkat Gletscher, 65° 41′ N, 37° 48′ W). The groundwater temperature, electrical conductivity and pressure head were monitored from August 2009 to August 2011, and water samples were collected in 2009 and analyzed for major ions and water isotopes (δD, δ18O). The 2 yrs of monitoring revealed that major outbursts of glacier water during the ablation season flushed the proglacial aquifer and determined the groundwater quality for the next 2–8 weeks until stable chemical conditions were reached again. Water isotope composition shows that isotopic fractionation occurs in both groundwater and glacier meltwater, but fractionation due to evaporation from near‐surface soil moisture prior to infiltration has the most significant effect. This study shows that groundwater in Low Arctic Greenland is likely to possess a combined geochemical and isotopic composition, which is distinguishable from other water sources in the proglacial environment. However, the shallow groundwater composition at a given time is highly dependent on major outbursts of glacier water in the previous months.  相似文献   

5.
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   

6.
The origin and mobilization of the extensive debris cover associated with the glaciers of the Nanga Parbat Himalaya is complex. In this paper we propose a mechanism by which glaciers can form rock glaciers through inefficiency of sediment transfer from glacier ice to meltwater. Inefficient transfer is caused by various processes that promote plentiful sediment supply and decrease sediment transfer potential. Most debris‐covered glaciers on Nanga Parbat with higher velocities of movement and/ or efficient debris transfer mechanisms do not form rock glaciers, perhaps because debris is mobilized quickly and removed from such glacier systems. Those whose ice movement activity is lower and those where inefficient sediment transfer mechanisms allow plentiful debris to accumulate, can form classic rock glaciers. We document here with maps, satellite images, and field observations the probable evolution of part of a slow and inefficient ice glacier into a rock glacier at the margins of Sachen Glacier in c. 50 years, as well as several other examples that formed in a longer period of time. Sachen Glacier receives all of its nourishment from ice and snow avalanches from surrounding areas of high relief, but has low ice velocities and no efficient system of debris removal. Consequently it has a pronounced digitate terminus with four lobes that have moved outward from the lateral moraines as rock glaciers with prounced transverse ridges and furrows and steep fronts at the angle of repose. Raikot Glacier has a velocity five times higher than Sachen Glacier and a thick cover of rock debris at its terminus that is efficienctly removed. During the advance stage of the glacier since 1994, ice cliffs were exposed at the terminus, and an outbreak flood swept away much debris from its margins and terminus. Like the Sachen Glacier that it resembles, Shaigiri Glacier receives all its nourishment from ice and snow avalanches and has an extensive debris cover with steep margins close to the angle of repose. It has a high velocity similar to Raikot Glacier and catastrophic breakout floods have removed debris from its terminus twice in the recent past. In addition, the Shaigiri terminus blocked the Rupal River during the Little Ice Age and is presently being undercut and steepened by the river. With higher velocities and more efficient sediment transfer systems, neither the Raikot nor the Shaigiri form classic rock‐glacier morphologies.  相似文献   

7.
Smaller glaciers (<0.5 km2) react quickly to environmental changes and typically show a large scatter in their individual response. Accounting for these ice bodies is essential for assessing regional glacier change, given their high number and contribution to the total loss of glacier area in mountain regions. However, studying small glaciers using traditional techniques may be difficult or not feasible, and assessing their current activity and dynamics may be problematic. In this paper, we present an integrated approach for characterizing the current behaviour of a small, avalanche‐fed glacier at low altitude in the Italian Alps, combining geomorphological, geophysical and high‐resolution geodetic surveying with a terrestrial laser scanner. The glacier is still active and shows a detectable mass transfer from the accumulation area to the lower ablation area, which is covered by a thick debris mantle. The glacier owes its existence to the local topo‐climatic conditions, ensured by high rock walls which enhance accumulation by delivering avalanche snow and reduce ablation by providing topographic shading and regulating the debris budget of the glacier catchment. In the last several years the glacier has displayed peculiar behaviour compared with most glaciers of the European Alps, being close to equilibrium conditions in spite of warm ablation seasons. Proportionally small relative changes have also occurred since the Little Ice Age maximum. Compared with the majority of other Alpine glaciers, we infer for this glacier a lower sensitivity to air temperature and a higher sensitivity to precipitation, associated with important feedback from increasing debris cover during unfavourable periods.  相似文献   

8.
玉龙雪山冰川稳定同位素分馏冬夏对比   总被引：8，自引：0，他引：8  
利用玉龙雪山白水1号冰川区冬季和夏季表面积雪、雪坑、融水以及白水河河水中δ18O资料,对比分析了冬季和夏季我国典型季风温冰川系统内稳定同位素分馏行为的差异。分析结果表明,夏季冰川系统内各水体相变过程中稳定同位素分馏程度均比冬季强烈,指示出夏季季风海洋型冰川强烈消融的特点。另外,不论是冬季还是夏季,从表面积雪到融水再到由融水补给的河流,δ18O垂直变化梯度依次增大,反映了从固态降雪向冰川融水补给的河流河水转换过程中,稳定同位素分馏程度逐渐增强,体现了沉积后过程对海洋型冰川区同位素记录的影响具有空间差异性。  相似文献   

9.
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   

10.
In the southernmost tract of the Alps (Italian‐French Maritime Alps), extensively covered by glaciers during the Last Glacial Maximum, about 30 small glaciers were present by the end of the Little Ice Age. The aim of this paper is to document the progressive decrease towards exhaustion of these glaciers, located at the latitude of 44° N, highlighting the factors affecting their retreat. All available data sources were investigated for this work including: the annual glaciers fluctuations record, comparative analyses of historical maps and multi‐temporal oblique photographs and direct surveys in the field. The history of the Maritime Alps glaciers fluctuations was thoroughly reconstructed. Stationary conditions were observed from 1896 up to the beginning of the 1930s; since then they underwent phases of withdrawal with variable intensity. In the early 1990s, only six glaciers were still present, the extent of which were all was dramatically reduced. In the past two decades, the Maritime Alps glacier fronts experienced a global retreat of about 100 m, with a sharp acceleration after 2002. Currently ice patches along cirque walls and/or semi‐buried lenses of ice are still present; morphological evidence of permafrost creeping in the glacier forefield accounts for the incipient transition to periglacial landforms (i.e. rock glaciers). The main factors controlling glaciers retreat seem to have been their original extent at the beginning of the current regressive phase and their distance from the main chain divide. From a climatic point of view unfavourable factors for glaciers persistence have been in the last decades a remarkable and sharp temperature increase, a decrease in winter snowfall and a shift of the rainfall peak from autumn to spring.  相似文献   

11.
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   

12.
The polythcrmal valley glacier Erikbreen (79°40'N 12°30'E), northern Spitsbergen, was investigated in 1970 and 1990 using digital photogrammetry and digital elevation model (DEM) techniques. The bottom topography was derived from radio-echo soundings. Based on the DEM, mass balance and changes of surface slope, crevasse and flow pattern were evaluated, and internal ice deformation velocities were calculated. Calculations of the total mass balance show that Erikbreen has not been in equilibrium for the last 20 years. The average surface lowering was 0.38 m/a and the volume had decreased by 5% to 6% from 1970 to 1990 or on the average by 3.5 × 10−1 water. The glacier surface subsided over the whole glacier area except in minor areas with northfacing slopes in the accumulation area. The surface slope and the crevasse pattern, however, did not change significantly during the 20-year-period, except in areas below 100 ma.s.l.  相似文献   

13.
Mass balance of glaciers in mountain areas varies not only with altitude and regional position but also with aspect, gradient, glacier size, glacier type and detailed topographic position. These factors are combined here in models of how glacier altitude varies, tested with data for the Alps edited from the World Glacier Inventory. An overall northward tendency in glacier numbers (toward 005 ± 4°) and lower altitudes (013 ± 5°) is maintained across a range of glacier sizes, types, altitudes and the major divisions of the Alps. Variation with aspect of glacier altitude (and, by implication, of glacier balance) in the Alps is essentially unimodal, and north‐facing glaciers average 220 m lower in middle altitude than south‐facing: 148 m in the Western Alps, 232 m in the West‐central, 252 m in the East‐central, and 268 m in the Eastern Alps. For smaller subdivisions, confidence intervals on estimates are broader and many differences lack statistical significance. Contrasts are greater in the higher massifs, with greater relief, and lower in cloudy, windward areas. There are small windrelated tendencies east of north along the northern and western fringes, but trends across space are weak: position is thus treated by subdivision into districts and groups. Mid‐altitude averages 2891 m overall and varies from 2552 to 3127 m for 27 glacier districts, and from 2124 to 3209 m for 103 glacier groups. Glacier mid‐altitude varies also with glacier form, nourishment, height range and area, which account for over two‐thirds of variance in combined models.  相似文献   

14.
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.  相似文献   

15.
利用Landsat影像，EDM影像等数据资料，使用遥感图像处理及目视解译方法提取了喜马拉雅山东段中国与不丹边境地区冰川从1990—2015年4期边界，研究其与气温降水变化关系，并选取特定冰川，对其表面流速进行估算。研究表明：1990—2015年，该地区冰川退缩速率达0.43%·a-1，并且冰川年退缩率逐渐增大，表明冰川消融速度逐渐加快。该时段内，气温呈现明显上升趋势，导致了冰川的快速消融。通过对冰川表面流速的估算，得出中国与不丹边境地区研究选取的冰前湖对冰川流速具有促进作用，加速冰川消融。  相似文献   

16.
This paper examines the occurrence of ephemeral hoarfrost crystals at funnel openings (funnel hoarfrost) detected between large blocks at the surface of the presumably relict Schöneben Rock Glacier. Field mapping on 25 November 2011 identified 51 individual funnel openings with notable hoarfrost crystals distributed over the entire rock glacier. Hoarfrost was no longer detectable a few days after the initial mapping campaign. At least in the period 20–25 November 2011 temperature conditions at the rock glacier surface were favourable for hoarfrost formation and preservation as indicated by different types of measurements. A period of 24–48 h of hoarfrost‐suitable weather conditions would have been sufficient to form the observed hoarfrost if crystal growth rates of 2–4 mm h?1 are assumed. The void systems with funnel hoarfrost seem to be rather localised and limited in horizontal (10s of metres) and vertical (some metres) extent. Presumably the observed funnel hoarfrost was caused by the so‐called chimney effect, although no larger reversible air circulation systems with warm air exhalation were identified. Continuous ground temperature data from several sites at the rock glacier surface (period November 2011–December 2012) showed that hoarfrost sites are cooler and thermally buffered compared with non‐hoarfrost sites at similar elevations. This seems to be related to the decoupling of the air above the rock glacier and the pore air during periods of atmospheric warming. Only the combination of specific micro‐climatic (temperature/humidity), geometric (open void systems) and sedimentological (grain size/sediment structure) conditions allow the formation of the ephemeral funnel hoarfrost at this rock glacier.  相似文献   

17.
Abstract The results of this dendrogeomorphological study provide evidence of the active movement of Hilda rock glacier, a tongue‐shaped rock glacier in the Columbia Icefield region of Banff National Park. Cross‐sectional samples were cut from 44 detrital subalpine fir (Abies Iasiocarpa (Hook.) Nutt.) and Engelmann spruce (Picea engelmannii Parry) boles killed and buried by debris spilling off the steep distal slope of the rock glacier. The samples were crossdated using locally and regionally developed tree‐ring chronologies, and were shown to have been killed between 1576 and 1999. Our results show that Hilda rock glacier has advanced at an average rate of 1.6 cm/year since the late 1790s, with limited evidence of similar rates of activity extending back to the mid‐1570s. This rock glacier activity is believed to be linked to persistent periglacial processes that appear to be independent of the climatic forcing mechanisms known to influence glacier mass balances over the same interval.  相似文献   

18.
玉龙雪山冰川稳定同位素分馏冬夏对比   总被引：3，自引：0，他引：3  
1 Introduction Under the dominance of South Asian monsoon, China’s temperate glaciers are distributed on Hengduan Mountains (southeast of Tibetan Plateau), the central part and southern slope of the Himalaya Mountains as well as the central and eastern p…  相似文献   

19.
The daily water balance for the drainage basin of Koryto Glacier, Kamchatka Peninsula, Russia, was calculated during the period from August to September 2000. The result shows that 14×106 m3 of meltwater and 2×106 m3 of rainwater entered the basin, while 26×106 m3 of water drained from the basin through proglacial streams. Thus, about ?9×106 m3 of water storage reduction occurred in the basin. Vertical displacements of the glacier surface showed that the volume change due to contraction of subglacial cavities was nearly 20% of the total storage change. The remaining fraction of water storage during the period is thought to be stored in englacial and supraglacial locations. The estimate of water balance components in the early ablation season in 2000 indicates that meltwater was already stored within the glacier before the spring, even during the previous year, and that the stored water drained through the ablation season.  相似文献   

20.
Thermal regime of a valley glacier, Erikbreen, northern Spitsbergen   总被引：1，自引：0，他引：1  
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.  相似文献   

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