On the Temperature Regime of Continental-Type Glaciers in China
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Abstract Ice temperature data collected from the area of continental–type glaciers in China since 1959 are analysed. Formulae for the temperature stratification of the active layer and for annual mean temperature profiles are suggested. The temperature in continental–type glaciers in China is quite low, rising rapidly with depth. A major part of the bottom of most glaciers reaches the pressure–melting point, with basal sliding. The extreme huge valley glacier will change from a cold glacier into a temperate one when it descends to the district where the climate is temperate. The ice temperature of the lower bound of the active layer at the altitude of the equilibrium line is 1.8–3.7 deg higher than the annual mean air temperature at the same level. The western section of Ch’i–licn Shan (Qilian Shan) may be the place where the temperature of alpine glaciers is the lowest of the middle and low latitudes. The infiltration zone is warmed significantly by the infiltration and recongelation process. A scheme showing how the lower bound temperature of the active layer changes with glacial zones is drawn. Le régime des températures dans les glaciers de type continental en Chine. On analyse les températures de la glace recueillies sur glaciers de type continental en Chine depuis 1959. On a suggéré des formules pour rendre compte de la stratification des températures du niveau actif, et pour le profil de température moyenne annuelle. La température dans les glaciers de type continental en Chine est très basse, s’élevant rapidement en profondeur. La plus grande partie du fond, dans la plupart des glaciers atteint le point de fusion correspondant à la pression, avec glissement sur le fond. Un très grand glacier de vallée se transforme de glacier froid en glacier tempéré lorsqu’il aborde une région où le climat est tempéré. La température de la glace à la limite inférieure du niveau actif, à l’altitude de la ligne d’équilibre est de 1,8 à 3,7 deg supérieure à la température moyenne annuelle de l’air à la même altitude. La section occidentale du Ch’i–lien Shan (Qilian Shan) est peut être l’endroit où la température d’un glacier alpin est la plus basse dans les latitudes moyennes et basses. La zone d’infiltration est, de manière significative, réchauffée par un processus d’infiltration et de regel. On a dressé un schéma montrant les variations de la température de la limite inférieure du niveau actif avec les zones de glaciations. Über den Wärmehaushalt der kontinentalen Gletscher in China. Die Beobachtungen der Eistemperaturen aus dem Gebiet der kontinentalen Gletscher in China seit 1959 werden analysiert. Formeln fūr die Temperaturschichtung im aktiven Eis und fūr ein Profil der Jahresmitteltemperalur werden vorgelegt. Hie Temperatur in den kontinentalen Gletschern Chinas ist sehr niedrig, steigt jedoch schnell mit der Tiefe. Ein Grossteil der Grundschicht in den meisten Gletschern befindet sich auf dem Druckschmelzpunkt und gleitet am Untergrund. Extrem mächtige Talgletschcr wandeln sich von kalten zu temperierten Gletschern, wenn sie in den Bereich temperierten Klimas herabfliessen. An der unleren Grenze des aktiven Schichts in Höhe der Gleichgewichtslinie ist die Temperatur 1.8-3.7 deg höher als die Jahresmitteltemperatur in derselben Höhe. Der Westteil des Ch’i-lien Shan (QMian Shan) dūrfte der Ort sein, wo alpine Gletscher der mittleren und niedrigen Breiten ihre tiefste Temperatur erreichen. Die Sickerzone wird durch das Sickerwasser und die Wiedergerrierwärme beträchtlich erwärmt. Eine schematisch Darstellung zeigt die Veränderung der Temperatur der Untergrenzc des aktiven Schichts innerhalb der vergletscherten Zonen.Keywords:
Accumulation zone
Stratification (seeds)
Accumulation zone
Deglaciation
Glacier mass balance
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Latest satellite images have been utilized to update the inventories of glaciers and glacial lakes in the Pumqu river basin, Xizang (Tibet), in the study. Compared to the inventories in 1970s, the areas of glaciers are reduced by 19.05% while the areas of glacial lakes are increased by 26.76%. The magnitudes of glacier retreat rate and glacial lake increase rate during the period of 2001–2013 are more significant than those for the period of the 1970s–2001. The accelerated changes in areas of the glaciers and glacial lakes, as well as the increasing temperature and rising variability of precipitation, have resulted in an increased risk of glacial lake outburst floods (GLOFs) in the Pumqu river basin. Integrated criteria were established to identify potentially dangerous glacial lakes based on a bibliometric analysis method. It is found, in total, 19 glacial lakes were identified as dangerous. Such finding suggests that there is an immediate need to conduct field surveys not only to validate the findings, but also to acquire information for further use in order to assure the welfare of the humans.
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Glacial landform
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We have analyzed one rapidly expanding glacial lake and one stagnant glacial lake located in the central Himalaya to understand the impact of local topography on the expansion and evolution of glacial lakes using remote sensing data. The slope, aspect, incoming solar radiation and compactness ratio of glaciers associated with the glacial lakes have been studied and analyzed. Glacier topography play important role in the expansion of glacial lakes as observed from the study..
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<p>In recent years, the number and size of glacial lakes in mountain regions have increased worldwide associated to the climate-induced glacier retreat and thinning. Glacial lakes can cause glacial lake outburst floods (GLOFs) which can pose a significant natural hazard in mountainous areas and can cause loss of human life as well as damage to infrastructure and property.</p><p>The glacial landscape of the Jostedalsbreen ice cap in south-western Norway is currently undergoing significant changes reflected by progressing glacier length changes of the outlet glaciers and the formation of new glacial lakes within the recently exposed glacier forefields. We present a new glacier area outline for the entire Jostedalsbreen ice cap and the first detailed inventory of glacial lakes which were formed within the newly exposed ice-free area at the Jostedalsbreen ice cap. In detail, we explore (i) the glacial lake characteristics and types and (ii) analyse their spatial distribution and hazard potential.</p><p>For the period from 1952-1985 to 2017/2018 the entire glacier area of the Jostdalsbreen ice cap experienced a loss of 79 km<sup>2</sup>. A glacier area reduction of 10 km<sup>2</sup> occurred since 1999-2006. Two percent of the recently exposed surface area (since 1952-1985) is currently covered with newly developed glacial lakes corresponding to a total number of 57 lakes. In addition, eleven lakes that already existed have enlarged in size. Four types of glacial lakes are identified including bedrock-dammed, bedrock- and moraine-dammed, moraine-dammed and ice-dammed lakes. Especially ice- or moraine-dammed glacial lakes can be the source of potentially catastrophic glacier lake outburst floods. According to the inventory of glacier-related hazardous events in Norway GLOFs represent the most common hazardous events besides ice avalanches and incidents related to glacier length changes. Around the Jostedalsbreen ice cap several historical but also recent events are documented. The majority of the events caused partly severe damage to farmland and infrastructure but fortunately no people have been harmed by today.</p><p>Due to the predicted increase in summer temperatures for western Norway until the end of this century, it is very likely that the current trend of an accelerated mass loss of Norwegian glaciers will continue. As one consequence of this development, further new lakes will emerge within the newly exposed terrain. The development of new glacial lakes has diverse regional and global socio-economic implications. Especially in mainland Norway, where glaciers and glacier-fed streams have a high importance for hydropower production, tourism and climate research it is essential to gain a better understanding of the possible impacts of glacial lakes for being prepared for risks but also advantages arising from these newly emerging landscape elements.</p>
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Owing to intense glacial retreat and melting, it is anticipated that numerous glacial lakes will be formed in the next few decades. However, their development and distribution patterns in the Tibetan Plateau and its surroundings still need to be elucidated. In this study, a published glacier ice thickness distribution dataset was employed to fully detect overdeepened glacier beds as potential glacial lakes. We selected and expanded four morphological metrics to determine the formation probability of potential glacial lakes: surface slope, break in slope, lake area, and position on the glacier. The results revealed that 15,826 potential glacial lakes with areas >0.02 km2 exist in the Tibetan Plateau and its surroundings, covering an area of 2253.95 ± 1291.29 km2 with a water volume of 60.49 ± 28.94 km3 that would contribute to an equivalent sea level rise of 0.16 ± 0.08 mm. The experimental comparison and uncertainty assessment for the overdeepening processing showed that the different extraction methods and basic digital elevation models used could lead to non-negligible errors in the results (at least ±30%), which were ignored in previous studies, contributing to major divergences between the several current inventories of potential glacial lakes in the plateau. Notably, approximately 90% of the total area of the potential glacial lakes is concentrated in the lower half of the individual glaciers in the Tibetan Plateau and its surroundings. >70% of the potential glacial lakes and contemporary glacial lakes in this region were found to be concentrated within the 4000–5800 m elevation range. Moreover, the study identified 5361 potential glacial lakes with high or very high exposure probabilities, and their distribution was mostly determined by regional glacier resources. However, the numbers and sizes of some potential glacial lakes that are found in the Karakoram region are considered to be exaggerated because of the presence of numerous surge-type glaciers, which have not been discussed in previous studies. These results can improve our understanding of future glacial lake formation and distribution in the Tibetan Plateau and its surroundings and have implications for further implementation of effective prevention, mitigation, and adaptation measures for glacial lake outburst floods and water security.
Glacial lake
Elevation (ballistics)
Last Glacial Maximum
Meltwater
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Thinning
Accumulation zone
Glacier morphology
Glacier ice accumulation
Glacier terminus
Glacier mass balance
Rock glacier
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Based on surveying data of glacial striae on roches mountonnees near the terminus of Glacier No.1 and Glacier No.7 at the head of Urumqi River, Tian Shan Mt., the statistical graduation character of glacial striae is discussed in this paper. It is shown that the statistical graduation character of glacial striae conforms to the exponent model, and the parameters (A and B) of this model can be used as indexes to describe the density of glacial striae and the glacial dynamics. The larger A and B are, the larger the density of glacial striae is. The spatial distribution of the parameters (A and B) of glacial striae is influenced by the size of glacier, location in the trough, and position on the roches mountonnee. It is shown in this area that the A and B values are larger in the larger glacier (Glacier No.1) than those in the smaller (Glacier No.7), and larger on the top side of the roches mountonnee than those on the lateral side. At the same time, the A and B values are also varied from the center to the edge in glacial troughs influenced by the micro forms in glacial valleys.
Last Glacial Maximum
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Based on the measured surface temperature data on the Qiumianleiketage Glacier in the Kunlun Mountains,Tibetan Plateau,in the spring of 2013,it was found that:1)the glacier surface(covered by firn)temperature was lower in the clear day than in the cloudy or overcast day,which might be caused by that some parts of energy absorbed by the glacier surface were consumed for the firn surface melting rather than for the firn surface temperature increasing in the clear day;2)the glacier surface temperature decreased with increasing altitude with a lapse rate of 0.58 ℃·(100m)-1 in the clear day,which is slightly lower than the local free-air lapse rate;3)the depth of firn on the glacier surface could exert an important influence on the surface temperature in the clear day,and there was a significant positive relationship between them,which showed that the firn surface temperature increased by 0.46℃ while the depth of firn increased by 10cm.By comprehensive analysis of the surface temperature data from the glaciers over the Tibetan Plateau,it was revealed that the diurnal amplitude of glacier surface temperature was small,only about several degrees,under the condition that the melting occurred on the glacier surface.
Firn
Accumulation zone
Glacier mass balance
Overcast
Glacier ice accumulation
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