Deposition of Organic Compounds on Alpine Snow
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<p>Currently, little is understood about the deposition and re-volatilisation of organic matter (OM) in snow. Understanding this balance for individual organic compounds has the potential to provide important information about present and past atmospheric conditions. This research investigates in detail the deposition and re-volatilisation rates for speci&#64257;c atmospheric OM that are present in alpine snow. Captured in the blank canvas of snow, any dissolved organic matter (DOM) in surface snow will re&#64258;ect the relative abundances in the atmosphere once their deposition and revolatilisation rates are known. Likewise, DOM e&#64256;ectively preserved in glacial ice will also express relative atmospheric composition of past climates. A recent pilot study by D. Materi&#263; et al.[1] investigates the post-precipitation change of OM in snow near the Sonnblick Observatory in the Austrian Alps. Using proton transfer reaction mass spectrometry, surface snow samples taken over several days were analyzed, and any organics found were grouped by their similar dynamics. This research expands on this study by analyzing snow samples over a larger spatial domain around Sonnblick during the course of &#64257;ve days in conjunction with long-term snow sampling currently underway at the observatory. Together, analysis of these samples will reveal changes in OM in surface snow over the course of the entire melt season. This research also considers both &#64257;ltered and un&#64257;ltered snow samples to di&#64256;erentiate and identify OM of di&#64256;erent sizes that are present within each sample. Long-term measurements of post-precipitation OM in surface snow will provide more coherent trends for deposition and re-volatilisation rates of organics, which can be used to tie future measurements of DOM in surface snow to atmospheric OM.</p>Keywords:
Deposition
Volatilisation
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.
Glacial lake
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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.
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Elevation (ballistics)
Last Glacial Maximum
Meltwater
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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.
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