共查询到20条相似文献，搜索用时 31 毫秒
1.
Prakash Kumar Shrivastava Rajesh Asthana Sandip Kumar Roy 《Journal of the Geological Society of India》2011,78(2):117-123
Recession of the snout of Dakshin Gangotri glacier in the western part of Schirmacher Oasis, East Antarctica has been recorded
over two decades. However, the rate of retreat is not uniform and varies at different locations. The ice wall forming the
western flank of the glacier has shown an average retreat of 17.07 m between 2001 and 2009 while the snout had gone back by
6.94 m (average) during the same period. Before 2001, the snout had shown a complete recession of 3.13 m (average). The snout
occupies valley area receiving less amount of solar radiation as compared to the western wall, which is a vertical cliff receiving
maximum amount of solar radiation. The notable difference in the rate of recession in different parts of the Dakshin Gangotri
glacier overriding Schirmacher Oasis can be attributed to combined effect of natural factors, including meteorological parameters,
ice sheet dynamics and geomorphology of that area. 相似文献
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A. Bhattacharyya P. S. Ranhotra J. T. Gergan 《Journal of the Geological Society of India》2011,77(5):401-408
Palynological analysis from a 10 m deep sediment profile from Dokriani valley, Garhwal Himalaya, provides temporal variation
of vegetation vis-à-vis climate and glacier history of the region. This study reveals that between 12,406 and 10,633 cal yr
BP vegetation was sparse when the climate was cool-dry and the glacier snout might had been located at lower elevations in
comparison to its present position. Subsequently around 10,633 cal yr BP, an increase in the growth of diversified taxa close
to the site, indicates the early Holocene climatic amelioration when glacier might have retreated at faster rate. Further,
within Holocene some intermittent cool-dry episodes were recorded around 9,670 to 9,000 cal yr BP and 7,100 cal yr BP when
glacier might have shown reduction in retreat rate or came to stagnation. 相似文献
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冰川跃动是多种冰川灾害的主要致灾因子,近年来与冰川跃动相关的冰崩、冰川垮塌、冰川泥石流等灾害的发生频率不断增加,使其成为国际国内冰川学研究的热点。依据对现有文献的统计发现,全球总计约有1 850条跃动冰川,主要分布于环北极地区和亚洲高山区,其中我国西部约有跃动冰川146条。跃动冰川可通过其特殊的表面形态标志,跃动前后冰川末端位置、表面高程和运动速度的变化,以及跃动产生的地貌学和沉积学特征来进行鉴别。跃动冰川的特殊运动模式主要由其内部和底床特性决定,包括冰内/冰下的热力学、水力学与形变等参数及变化过程等。现有大多数跃动冰川研究是基于各类遥感技术,主要着眼于跃动冰川表面变化,并据其对冰川跃动的可能机制进行分析。由于遥感方法精度有限且受天气、地形条件等的制约,同时无法获取冰内/冰下关键参数,因此野外现场观测在这些参数获取方面仍具有不可替代的作用。受限于冰内/冰下参数野外观测数据的缺乏,目前对冰川跃动机理的认识仍局限于早期提出的水力学和热力学两种机制,无法解释同一区域具备不同跃动机制的冰川共存,以及部分冰川跃动从冰川下部发起等问题。同时,在气候变化对跃动冰川的影响研究以及冰川跃动的模拟和预测等方面还有较大欠缺,需要在未来研究中重点关注。 相似文献
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Henrik Løseth Jansen Svein Olaf Dahl Henriette Linge Jostein Bakke Pål Ringkjøb Nielsen Bjørn Christian Kvisvik 《Boreas: An International Journal of Quaternary Research》2023,52(2):168-193
Continuous glacier margin and equilibrium-line altitude fluctuations of a former glacier on central Andøya, northern Norway, are reconstructed during the Lateglacial based on moraines and AMS 14C-dated sediments from the distal glacier-fed lake Ner-Finnkongdalsvatnet. The results indicate that a valley glacier occupied the entire valley during the Last Glacial Maximum (before 21 970±620 cal. a BP). The glacier remained large throughout the early Lateglacial until a significant glacier retreat took place about 14 300±330 cal. a BP. Major advances occurred during the Older Dryas (OD) and during the Younger Dryas (YD), while minor advances are suggested to have taken place during the Intra Allerød Cold Period and the Late Allerød Cooling. Additionally, three smaller glacier retreats/re-advances within the YD are suggested to have taken place, the latter being the largest. The glacier re-formations/advances during the Lateglacial are consistent with increases in temperature, and they are thus suggested to be the result of increased winter precipitation. Comparing the results with relevant glacier and sea-surface temperature records, a south–north migration of storm tracks may have occurred between 12 100–11 810±220 cal. a BP. The high temporal resolution of local glacier activity in Finnkongdalen improves our understanding of the climate forcing of the regional glacier fluctuations of the northwestern sector of the Scandinavian Ice Sheet during the Skarpnes- (OD) and Tromsø-Lyngen (YD) re-advances. 相似文献
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The North Atlantic Oscillation (NAO) is one of the modes of climate variability in the North Atlantic region. The atmospheric circulation during the winter season in this region commonly displays a strong meridional (north–south) pressure contrast, with low air pressure (cyclone) centred close to Iceland and high air pressure (anticyclone) near the Azores. This pressure gradient drives the mean surface winds and the mid‐latitude winter storms from west to east across the North Atlantic, bringing mild moist air to northwest Europe. The NAO index is based on the difference of normalised sea‐level pressures (SLP) between Ponta Delgada, Azores and Stykkisholmur, Iceland. The SLP anomalies at these stations are normalised by division of each monthly pressure by the long‐term (1865–1984) standard deviation. Interannual atmospheric climate variability in northwest Europe, especially over Great Britain and western Scandinavia has, during the last decades, been attributed mainly to the NAO, causing variations in the winter weather over the northeast North Atlantic and the adjacent land areas. A comparison between the NAO index and the winter (December–March) precipitation between ad 1864 and 1995 in western Norway shows that these are strongly linked (correlation coefficient 0.77). Variations in the NAO index are also reflected in the mass balance records of glaciers in western Scandinavia. The NAO index is best correlated with mass balance data from maritime glaciers in southern Norway (e.g. Ålfotbreen R2 = 0.51). The record of Holocene (last ca. 11 500 cal. yr) glacier variations of maritime glaciers in western Scandinavia is thus a proxy of pre‐instrumental NAO variations. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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《Quaternary Research》2014,81(3):464-475
It is highly debated whether glacial advances on the Qinghai–Tibetan Plateau (QTP) occurred as a response to temperature cooling, or whether they were forced by an increase in moisture brought by the intensive Indian summer monsoon. We here report a case study investigating this issue. Multiple moraine series in the Yingpu Valley, Queer Shan ranges of the Hengduan Mountains, and eastern QTP, provide an excellent archive for examining the timing and trigger mechanism of glacier fluctuations. Twenty-seven optically stimulated luminescence (OSL) samples of glacial sediments were collected from this valley. The quartz OSL ages show that the moraine series of Y-1, I, M and O were formed during the Late Holocene, Late Glacial, the global Last Glacial Maximum (LGM) and Marine Oxygen Isotope Stage (MIS) 3 (likely mid-MIS-3). The youngest Y-2 moraines probably formed during the Little Ice Age (LIA). The oldest H moraines formed before MIS-3. We found that glacial advances during the late Quaternary at the Yingpu Valley responded to cold stages or cold events rather than episodes of enhanced summer monsoon and moisture. As a result, glaciers in the monsoonal Hengduan Mountains were mainly triggered by changes in temperature. Millennial time scale temperature oscillations might have caused the multiple glacial advances. 相似文献
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Natural Hazards - The paper presents a historical long-distance communication system based on beacon fires in one of the most dynamic and rugged mountain ranges of the world, the Hindu... 相似文献
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Glaciers in the southern province of the Southern Volcanic Zone (SVZ) of Chile (37–46°S) have experienced significant frontal retreats and area losses in recent decades which have been primarily triggered by tropospheric warming and precipitation decrease. The resulting altitudinal increase of the Equilibrium Line Altitude or ELA of glaciers has lead to varied responses to climate, although the predominant volcanic stratocone morphologies prevent drastic changes in their Accumulation Area Ratios or AAR. Superimposed on climate changes however, glacier variations have been influenced by frequent eruptive activity. Explosive eruptions of ice capped volcanoes have the strongest potential to destroy glaciers, with the most intense activity in historical times being recorded at Nevados de Chillán, Villarrica and Hudson. The total glacier area located on top of the 26 active volcanoes in the study area is ca. 500 km2. Glacier areal reductions ranged from a minimum of −0.07 km2 a −1 at Mentolat, a volcano with one of the smallest ice caps, up to a maximum of −1.16 km2 a −1 at Volcán Hudson. Extreme and contrasting glacier–volcano interactions are summarised with the cases ranging from the abnormal ice frontal advances at Michinmahuida, following the Chaitén eruption in 2008, to the rapid melting of the Hudson intracaldera ice following its plinian eruption of 1991. The net effect of climate changes and volcanic activity are negative mass balances, ice thinning and glacier area shrinkage. This paper summarizes the glacier changes on selected volcanoes within the region, and discusses climatic versus volcanic induced changes. This is crucial in a volcanic country like Chile due to the hazards imposed by lahars and other volcanic processes. 相似文献
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Ice core δ18O records from the No. 1 glacier at the head of the ürümqi River were used to characterize the relationship between δ18O and contemporaneous surface air temperature (Ta) nearby the Daxigou Meteorological Station (3539 m above sea level, ∼2km away from the ice core drilling site). Although the ice core records of annually averaged δ18O are positively correlated with contemporaneous surface air temperature, especially summer air temperature, the correlation is less significant than that for the precipitation samples due to depositional and post-depositional modification processes. However, the climatological significance of the ice core δ18O records can be still preserved to a certain degree, which might extend the application of high altitude and sub-tropical ice core δ18O records to paleoclimate reconstruction. 相似文献
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以泥盆系占优势的南秦岭成矿带中存在有重要的Ｐｂ－Ｚｎ－Ａｇ，Ａｕ，Ｈｇ－Ｓｂ及Ｃｕ矿床。它们形成中晚古生带扬子地块北部被动大陆边缘的沉积盆地演化与造山期中，成矿系列显示出时间与空间的演化特征，构在了一个热水沉积成矿系列，成矿发生于一个热旋回中，各种矿化有相似的物源，每一种地质事件都有特定的金属富集及富集在型和大型矿床是该地区构造－岩浆变质变形作用的最终产物。 相似文献
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应用ＩＣＰ－ＭＳ法测定了岩石中的痕量Ｎｂ、Ｔａ、Ｚｒ、Ｈｆ、Ｔｈ、Ｕ，给出了检出限，并对酸溶和碱熔两种制样方法进行了对比实验。 相似文献
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Marie-PierreAubry WilliamA.Berggren JohnVanCouvering BrianMcGowran BradPillans FritsHilgen 《《幕》》2005,28(2):118-120
The long controversy over the term ‘Quaternary‘ as a chronostratigraphic unit may be reaching an apotheosis, judging from recent papers (Pillans and Naish, 2004; Gibbard et al., 2005; and referencest herein). The debate is no longer centered on whether there should be a place in the geological time scale for a unit termed ‘Quaternary‘-despite its dubious past, it cannot be denied that a large body of earth-historical research is strongly identified with this term. The challenge now concerns an appropriate rank and definition of Quaternary with regard to other chronostratigraphic units. Several options have been proposed (Pillans and Naish, 2004), and Gibbard et al. (2005) encourage a debate on these before decision is reached. In this brief note, we describe an arrangement not previously considered that seems advantageous. It is instructive, however, to first review the Pleistocene Series and Neogene System, the two units that are directly affected by introduction of the Quaternary into the chronostratigraphic hierarchy. 相似文献
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大陆漂移, 板块构造, 地质力学 总被引：2，自引：0，他引：2
本文简要地介绍了魏格纳大陆漂移说的主要内容及其提出的依据; 论述了在大陆漂移说的基础上, 由于海洋地质地球物理调查发现了大洋中脊、洋底扩张, 解释了大陆张裂的机制, 并建立了全球板块构造理论, 形成现代地学思想的革命; 李四光在大陆漂移说提出的同时已在积极地探讨和论述大陆地壳水平运动问题, 并结合中国大陆实际, 发展了陆内碰撞变形理论, 即包括全球大陆构造体系在内的地质力学理论和方法。他强调地质力学是一支脚站在地质上, 另一支脚站在力学上来研究地壳运动和变形现象。后来更扩大了其在资源、环境方面的应用。文章对魏格纳大陆漂移说、全球板块构造理论及地质力学三者的关系做了深入探讨, 论述了李四光地质力学理论方法的现代意义、超前意义, 提出要重视和发扬李四光留给中国人民的宝贵遗产, 建议深入学习李四光的著述, 结合地质调查新成果去丰富它和发展它。 相似文献
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