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1.
南极海冰和陆架冰的时空变化动态 总被引：3，自引：0，他引：3
利用美国冰中心和雪冰中心提供的海冰资料和我国南极考察现场的海冰观测资料, 对南极海冰的长期变化进行了研究.结果表明: 20世纪70年代后期是多冰期; 80年代是少冰期; 90年代南极海冰属于上升趋势, 后期偏多; 区域性变化差别大, 东南极海冰偏多, 西南极海冰即南极半岛两侧特别是威德尔海(Weddell Sea)区和别林斯高晋海(Bellingshausen Sea)的冰明显偏少.东南极和西南极海冰的变化趋势总是反相的.90年代后期普里兹湾的海冰明显偏多, 南极大陆陆架冰外缘线总体没有明显的收缩, 有崩解也有再生的自然变化现象.西南极威德尔海的龙尼冰架(Ronne Ice Shelf)和罗斯海冰架(Ross Ice Shelf)东部崩解和收缩趋势明显, 东南极的冰架也有崩解和收缩, 但没有西南极明显.陆架冰崩解向海洋输送的冰山对全球海平面升高有一定的影响.目前, 南极冰盖断裂崩解形成的冰山, 向海洋输入的水量可使全球海平面上升约14 mm.南极海冰没有随着全球气候温暖化而明显减少, 而是按照东南极和西南极反相的变化规律进行周期性的变化、调整和制约. 相似文献
2.
南极海冰与气候 总被引：1，自引：0，他引：1
在极区,海冰的形成在海洋上部和大气下部之间构成了新的交界面,改变了大洋表面的辐射平衡和能量平衡,隔离了海洋与大气之间的热交换和水汽交换;海冰冻融过程影响着大洋温、盐流的形成和强度;海冰对南大洋和南极大陆气象、气候有重要的影响,在气候环境系统中起着重要的作用。南极海冰作用区约占南半球雪冰作用区面积的58%,约占地球表面积的3.58%。其中,一年生海冰约占南极海冰区分布面积的83%;其分布面积从夏末2月份最小时的3×106 km2左右,到9月份冬末最大时的18×106 km2左右,一年中季节变化幅度可达15×106 km2,季节变化率>500%。海冰分布区域的年际变化较大。南极海冰区是影响季节和年际全球气候环境变化的重要区域。当前,国际南极海冰与气候研究的核心问题是海冰物理过程和在海冰区的海洋—大气相互作用。结合目前承担的研究课题,对国际南极海冰与气候研究的前沿动态和相关的国际计划进行了综述。 相似文献
3.
大气、海洋与固体地球的能量交换 总被引：9，自引：0，他引：9
通过对南极气温资料、南极臭氧资料、环南极海冰资料、太平洋海温资料、地球自转速度变化资料、厄尔尼诺和拉尼娜资料的模拟验证，发现厄尔尼诺事件发生与德雷克海峡海冰减少在时间上有一一对应关系。南极半岛海冰减少是太平洋环流速度减慢的原因，德雷克海峡的海冰起重要作用。大气、海洋与固体地球的角动量交换在南、北半球有不同的形式。强震起源于海平面振荡。 相似文献
4.
极地海冰的研究及其在气候变化中的作用 总被引：4，自引：2，他引：2
极地海冰作为全球气候系统的一个重要组成部分,通过影响大洋表面的辐射平衡、物质平衡、能量平衡以及大洋温、盐流的形成和循环而影响全球气候变化.从最初研究极地海冰的强度和承载力到目前海/冰/气相互作用全球气候耦合模型的建立,使海冰变化和全球气候变化紧密结合起来.这些研究领域主要有:海冰及其表层雪的物理特性和过程、海冰区域生态特征、海冰区与气候相关的反照率和物质平衡研究以及海冰气候耦合模型等大的领域.模拟显示,21世纪因为全球变暖,南北极海冰都将减少.海冰和全球气候系统其它要素之间的相互作用问题、极地海冰的厚度季节性区域性分布问题、极地海冰边界及范围变化趋势问题、生消关键过程及其影响因素问题、冰间湖的作用以及海气相互作用等将是未来重要的研究方向. 相似文献
5.
南极海冰涛动及其对东亚季风和我国夏季降水的可能影响 总被引：2，自引：0，他引：2
利用NCEP 1973-2002年逐月南极海冰密集度格点资料,定义了具有跷跷板式变化规律的南极海冰涛动指数,分析了冬季南极海冰涛动指数与我国夏季降水及东亚季风爆发时间的关系.结果显示:南极海冰涛动指数与同期南极海冰密集度相关系数超过5%信度的格点数占南极海冰格点数的1/3,表明定义南极海冰涛动指数能够代表南极地区1/3海冰的变化区域.冬季南极海冰涛动指数和我国汛期(6-8月)降水距平百分比相关显著,正相关主要在长江流域及其以南地区,长江流域以北为负相关,相关系数均超过5%的信度.当冬季南极海冰涛动指数为负值时,南海季风爆发早,概率为11/14=79%;为正值时南海季风爆发晚,概率为12/15=80%.通过讨论冬季南极海冰涛动指数影响我国季风降水的可能过程,给出了概念模型. 相似文献
6.
太平洋环流速度减慢的原因 总被引：7，自引：1，他引：7
对南极气温资料、环南极海冰资料、太平洋海温资料、厄尔尼诺和拉尼娜资料的模拟验证，发现厄尔尼诺事件发生与德雷克海峡海冰减少在时间上有对应关系。南极半岛海冰减少是太平洋环流速度减慢的原因，德雷克海峡的海冰起重要作用。这一综合检验结果给出以日食—厄尔尼诺系数预测厄尔尼诺事件的有效性和准确性。两年周期的太平洋海温振荡使日食与厄尔尼诺之间存在12～24个月的位相差。 相似文献
7.
基于CryoSat-2卫星测高数据分析南极海冰厚度的时空变化 总被引：1，自引：1，他引：0
利用卫星测高数据能够获取大尺度、长时序的海冰厚度信息。相较于北极,目前南极海冰厚度特别是近期变化信息仍很缺乏。基于2013-2018年的CryoSat-2卫星测高数据,采用最低点高程法和静力平衡方程模型反演了近6年逐月平均海冰厚度并分析其时空变化规律。结果表明：2013-2018年南极海冰厚度整体呈现先上升后下降的趋势,其中,2014-2017年年平均海冰厚度表现为快速变薄。南极较厚的海冰集中在威德尔海西南海域,最大值出现在该海域2014年的7月（6.27 m）。年平均海冰厚度在2017年达到最低值。南极海冰厚度的时空变化研究可为深入研究海冰变化与全球变化的关系提供参考。 相似文献
8.
南极洲总面积为1400×10~4km~2,其中95％被一硕大无比的冰盖覆盖。南极冰盖平均厚度为2200m,总冰储量达2900×10~4km~3,占全球淡水资源的四分之三。南极大陆边缘还发育有若干个大小不一的冰架。冬季,南极洲边缘海面厚达1—2m的海冰向北延伸数百公里;夏季,海冰破裂随洋流飘逝,数以万计的冰山从冰盖边缘形成,星罗棋布遍及南大洋。南极冰盖、冰架、海冰和冰山,它们形成、发育过程和机制,与南半球进而与全球气候的关系,以及与人类生活和生产活动的关系,是南极冰川学研究的主要对象与任务。 相似文献
9.
北极海冰与全球气候变化 总被引：7，自引：2，他引：7
最近有关北极海冰在全球气候系统中作用的研究发现，北冰洋边缘海域大洋深水的形成与海冰发育有关，海冰冻融过程对盐度层结具有重要影响，海冰变化可引起盐度突变层的灾变和热盐环流的突然停止，热盐环流的变化与北大西洋海冰１０年际变化相联系，北大西洋气候的不稳定性与热盐环流变化密切相关。北极海冰－海洋－大气间耦合作用，使北极海冰构成了北大西洋和全球气候反馈循环中的重要环节。 相似文献
10.
基于走航观测的夏季南极海冰分布特征分析 总被引：1，自引：0，他引：1
依托中国第19次南极科学考察,基于ASPeCt(南极海冰过程与气候)海冰走航观测方法标准,以"雪龙号"破冰船为平台进行夏季南大洋海冰走航观测.在2003年1月4-17日近6 500km的航程断面上,分别获取了海冰的厚度、密集度、雪厚度、浮冰尺寸等海冰分布特征参数.结果表明,海冰分布特征参数均呈现了较大的空间变化.由于夏季海冰融化并受制于特定动力过程作用,海冰在威德尔海附近聚集,密集度达到峰值,沿断面在0%～80%之间变化;在断面的大部分观测到开阔水域.沿断面海冰厚度介于10～210cm,雪厚度介于2～80 cm之间,在埃默里冰架附近冰雪厚度达到了全断面的最高值.沿断面浮冰尺寸,最小到＜10 cm到最大超过2 000 m不等. 相似文献
11.
C.D. Ollier 《地学学报》1992,4(3):312-319
Landscape evolution is on the same time-scale as global tectonics, biological evolution, and major climatic change. Some features of global change reflected in landscape evolution result from the breakup of Pangaea. Others relate to major climatic changes, and yet others to a major change from a dominantly plains landscape of the Mesozoic to an increasingly mountainous landscape in the Tertiary. Worldwide deep weathering profiles of Cretaceous and early Tertiary age suggest widespread planation and warm, moist climates. Erosion of deeply weathered regolith following the formation of new continental margins and tectonic uplift led to the deposition of unusual mature sediments. Many river patterns can be traced to early Tertiary or older antecedents.
Some climatic changes are due to orbital forcing, but others may be related to changing positions of continents, creation of new seaways, or to mountain building. The timing of mountain uplift, climatic changes and biological changes must be resolved to test models of their mutual interaction. Geomorphic input on tectonics, drainage evolution, and deep weathering will be an essential component in dealing with these problems. 相似文献
Some climatic changes are due to orbital forcing, but others may be related to changing positions of continents, creation of new seaways, or to mountain building. The timing of mountain uplift, climatic changes and biological changes must be resolved to test models of their mutual interaction. Geomorphic input on tectonics, drainage evolution, and deep weathering will be an essential component in dealing with these problems. 相似文献
12.
Frédéric Fluteau 《Comptes Rendus Geoscience》2003,335(1):157-174
The evolution of the Earth's climate over geological time is now relatively well known. Conversely, the causes and feedback mechanisms involved in these climatic changes are still not well determined. At geological timescales, two factors play a prevailing role: plate tectonics and the chemical composition of the atmosphere. Their climatic effects will be examined using palaeoclimatic indicators as well as results of climate models. I focus primarily on the influence of continental drift on warm and cold climatic episodes. The consequences of peculiar land sea distributions (amalgamation/dispersal of continental blocks) are discussed. Plate tectonics also drive sea level changes as well as mountain uplift. Marine transgressions during the Mid-Cretaceous favoured warmth within the interiors of continents, although their effect could be very different according to the season. Mountain uplift is also an important factor, which is able to alter climate at large spatial scales. Experiments relative to climatic sensitivity to the elevation of the Appalachians during the Late Permian are discussed. To affect the whole Earth, the chemical composition of the atmosphere appears to be a more efficient forcing factor. The carbon dioxide driven by the long-term carbon cycle has influenced the global climate. Geochemical modelling simulates more or less accurately the long-term evolution of pCO2, which corresponds roughly to the icehouse/greenhouse climatic oscillations. However, the uncertainties on pCO2 are still important because different parameters involved in the long-term carbon cycle (degassing rate, chemical weathering of silicates, burial of organic matter) are not well constrained throughout the past. The chemical composition of the atmosphere is also altered by the emissions of modern volcanic eruptions leading to weak global cooling. The influence of large flood basalt provinces on climate is not yet known well enough; this volcanism may have released huge amounts of SO2 as well as CO2. At last, the chemical composition of the atmosphere may have been altered by the release of methane in response to the dissociation of gas hydrates. This scenario has been proposed to explain the abrupt warming during the Late Palaeocene. 相似文献
13.
《Journal of African Earth Sciences》1999,28(1):99-114
Lithological indicators of climate, such as coals, evaporites, bauxites, and tillites,can be used to map the past position of the major climatic zones (Humid Tropics, Dry Subtropics, Warm and Cool Temperate, and Polar) that crossed the supercontinent of Gondwana. The early proponents of continental drift (Wegener, 1912; du Toit, 1937) recognised this fact and inferred that apparent climatic changes (e.g. Late Ordovician tillites in the Sahara Desert) were actually the result of Gondwana's movement across these climatic belts. It is now known that the changing width and location of these climatic zones reflects both: (1) Gondwana's latitudinal movement; and (2) changes in global climate from Ice House to Hot House conditions. This paper presents seven palaeogeographic maps and seven palaeoclimatic maps illustrating Gondwana's changing climate. 相似文献
14.
环境·灾害与地学 总被引：12，自引：1，他引：12
环境与灾害已成为中国社会经济发展的重大制约因素 ,保护环境、减轻灾害需要全社会的努力和科学支撑。环境与灾害的形成主要受两大因素控制 :一是自然变异 ,二是人类社会活动。地球在不停地运动着、变化着 ,致使人类、地球、环境发生日新月异的变化 ,并导致自然灾害的发生。从表面看 ,地圈的运动和变化导致地质环境的变迁和地震及地质灾害的产生 ;水圈的运动和变化导致水环境的变化和水灾害的发生 ;气圈的运动和变化导致气候环境的变化和气象灾害的发生 ;地球表层系统和生物圈的运动和变化导致生态环境的变化和生物灾害的发生。然而 ,从深层次看 ,由于地球是一个开放的自组织系统 ,各个圈层自身运动变化的同时 ,彼此也在发生着物质和能量的交流 ,各个圈层的运动与变化受控于全球运动与全球变化 ,并受太阳及其它天体运动和变化的影响。由此看来 ,地球各个圈层的环境与灾害的产生都不是孤立的现象 ,而是彼此相关 ,形成环境灾害系统 ,并作为地球系统的一个分支 ,属于全球变化的一个组成部分。基于这一认识 ,环境与灾害应当是地学研究的新命题。 相似文献
15.
过去气候演化的阶段性和突变 总被引：4，自引：0，他引：4
地球系统的历史信息是评估全球变化的一项重要因素。前些年，过去气候研究中发现了气候的突然变化的现象，突变证据大多出现在冰期，或由冰期向间冰期的过渡时期，并认为这是冰盖的成冰与溶解过程造成海水铅直运动的结果。近些年，过去气候研究还发现在间冰期中也出现突变。我国的历史文献、冰芯和沉积的高分辨率的古气候恢复工作发现近２０００年来中国气候明显存在着突变事件。因此，这给我们带来了新的问题，即间冰期气候的稳定性问题。如果气候突变的证据增多，那意味着气候系统很可能按两种方式运行 相似文献
16.
大陆风化与全球气候变化 总被引：12，自引：3，他引：12
:“构造隆升驱动气候变化”的假说是当前解释新生代以来全球气候变冷的主流观点。该假说把新生代以来发生的几个主要现象 ,即全球气候总体上趋冷 ,大气 CO2 浓度下降 ,海洋 87Sr/ 86Sr比值上升 ,以及构造作用引起的大面积隆升等加以有机的联系 ,给以了合理的解释。近几年围绕大陆风化和全球气候变化问题取得了一些新的进展 ,主要是对发源于喜马拉雅山的河流进行研究 ,探讨青藏高原隆起对于大陆风化速率的影响。这些争论主要是有关硅酸盐风化还是碳酸盐风化 ,有机碳的风化与埋藏 ,大陆风化与大气温度 ,大气 CO2 浓度与大气温度等问题。最后介绍了我国研究人员在黄土高原的黄土沉积地层所作的研究工作和取得的成果。 相似文献
17.
Zircon crystals precipitated from granitoid magmas contain a robust record of the age and chemistry of continental magmatism spanning some 4.375 Ga of Earth history, a record that charts initiation of plate tectonics. However, constraining when exactly plate tectonics began to dominate crustal growth processes is challenging as the geochemical signatures of individual rocks may reflect local subduction processes rather than global plate tectonics. Here we apply counting statistics to a global database of coupled U–Pb and Hf isotope analyses on magmatic zircon grains from continental igneous and sedimentary rocks to quantify changes in the compositions of their source rocks. The analysis reveals a globally significant change in the sources of granitoid magmas between 3.2 and 2.7 Ga. These secular changes in zircon chemistry are driven by a coupling of the deep (depleted mantle) and shallow (crustal) Earth reservoirs, consistent with a geodynamic regime dominated by Wilson cycle style plate tectonics. 相似文献
18.
Kurt Lambeck Anthony Purcell Nicholas. C. Flemming Claudio Vita-Finzi Abdullah M. Alsharekh Geoffrey N. Bailey 《Quaternary Science Reviews》2011,30(25-26):3542-3574
The history of sea level within the Red Sea basin impinges on several areas of research. For archaeology and prehistory, past sea levels of the southern sector define possible pathways of human dispersal out of Africa. For tectonics, the interglacial sea levels provide estimates of rates for vertical tectonics. For global sea level studies, the Red Sea sediments contain a significant record of changing water chemistry with implications on the mass exchange between oceans and ice sheets during glacial cycles. And, because of its geometry and location, the Red Sea provides a test laboratory for models of glacio-hydro-isostasy. The Red Sea margins contain incomplete records of sea level for the Late Holocene, for the Last Glacial Maximum, for the Last Interglacial and for earlier interglacials. These are usually interpreted in terms of tectonics and ocean volume changes but it is shown here that the glacio-hydro-isostatic process is an additional important component with characteristic spatial variability. Through an iterative analysis of the Holocene and interglacial evidence a separation of the tectonic, isostatic and eustatic contributions is possible and we present a predictive model for palaeo-shorelines and water depths for a time interval encompassing the period proposed for migrations of modern humans out of Africa. Principal conclusions include the following. (i) Late Holocene sea level signals evolve along the length of the Red Sea, with characteristic mid-Holocene highstands not developing in the central part. (ii) Last Interglacial sea level signals are also location dependent and, in the absence of tectonics, are not predicted to occur more than 1–2 m above present sea level. (iii) For both periods, Red Sea levels at ‘expected far-field’ elevations are not necessarily indicative of tectonic stability and the evidence points to a long-wavelength tectonic uplift component along both the African and Arabian northern and central sides of the Red Sea. (iv) The observational evidence is consistent with tectonic and isostatic processes both operating over the past 300,000 years without requiring changes in the time averaged (over a few thousand years) tectonic rates. (v) Recent bathymetric data for the Bab al Mandab region have been compiled to confirm the location and depth of the sill controlling flow in and out of the Red Sea. Throughout the last 400,000 years the Red Sea has remained open to the Gulf of Aden with cross sectional areas at times of glacial maxima about 2% of that today. (vi) The minimum channel widths connecting the Red Sea to the Gulf of Aden at times of lowstand occur south of the Hanish Sill. The channels are less than 4 km wide and remain narrow for as long as local sea levels are below ?50 m. This occurs for a number of sustained periods during the last two glacial cycles and earlier. (vii) Periods suitable for crossing between Africa and Arabia without requiring seaworthy boats or seafaring skills occurred periodically throughout the Pleistocene, particularly at times of favourable environmental climatic conditions that occurred during times of sea level lowstand. 相似文献
19.
Mine Sezgül Kayseri-Özer 《Geodinamica Acta》2013,26(1-2):122-157
The continental climatic evolution of Anatolia has been reconstructed quantitatively for the last 45 million years using the coexistence approach. Although there were some regional effects, the Anatolian Cenozoic continental climate record correlated with the European climatic condition and the global oxygen isotope record from marine environments. From middle Eocene to late Miocene, continental warming in Anatolia was pronounced for inferred winter temperature and mean annual temperature as in Europe. Generally, the palaeoclimatic property of Anatolia resembles the European climatic changing and marine temperature changing based on the oxygen isotope record; however, climatic values of the terrestrial area in Anatolia are higher from Lutetian to Aquitanian and these values are lower than European values from Aquitanian to Tortonian. Correspondingly, Cenozoic climatic cooling in Anatolia is directly associated with an increase of seasonality, palaeogeographic position and terrestrial condition. Furthermore, mean annual precipitation values of Anatolia remained relatively stable during the Eocene–Oligocene; however, these values indicated changing throughout middle–late Miocene. Moreover, in this study, decline of abundance and variables for the mangrove and back mangrove palaeocommunities during the last 45 million years is recorded because of the decreasing of humidity, temperature and increasing of terrestrial condition. 相似文献
20.
Changing sea levels and erupting volcanoes: cause and effect? 总被引：3，自引：0，他引：3
W. J. McGUIRE 《Geology Today》1992,8(4):141-144
The Quaternary period was characterized not only by significant cyclic changes in global temperature but also by increased explosive volcanism. Is this just coincidence or is there a connection? And if the latter, what is it? A number of possible mechanisms have been proposed to explain how these two apparently unrelated phenomena may be related, most involving the climatic effects of volcanic debris ejected into the atmosphere. A new model, however, proposes that changing sea levels during the last Ice Age may also have had an important role to play in this problematical scenario. 相似文献