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1.
我国大量地质资料反映了全球海洋氧同位素3阶段(MIS3)晚期具有间冰阶海侵、暖湿的气候环境特征.对这一阶段的气候成因论证,将为现代温室效应的气候增温提供重要的历史相似型.本文使用含有陆面过程的全球9层大气环流谱模式(AGCM+SSiB),采用地球轨道参数驱动的太阳辐射、北半球第四纪冰盖和东亚植被预置的下垫面对35kaB.P.气候进行了敏感性模拟试验.研究结果表明:(1)MIS3晚期中、低纬度大部分大陆全年温度增加,欧亚大陆腹地气温增高主要是冬季增温贡献,反映太阳辐射变化通过大气环流作用引起的更加显著的气候效应.南北海陆水汽交换的加强首先使低纬度季风区降水收益.(2)相当于LGM50%规模的第四纪冰盖不仅仅具有高纬度区降温效应,还强化了辐射纬向差异造成的南北温差,从而增强了水汽从低纬度区向高纬度区输送的能力,使青藏高原、南亚和非洲季风区的降水进一步增加.(3)35kaB.P.东亚植被对辐射的低纬度区增温具有增强效应,而对冰盖高纬度区降温具有减缓效应,结果扩大了欧亚内陆的降水增加范围,使中国高降水带向北推移.(4)中国各大区域35kaB.P.气候类型不尽相同.当中国东部与太平洋在同纬度带的热力差异减小时,东西向水汽输送减弱,造成东部沿海降水减少;但当欧亚大陆与低纬度区海洋温差增大时,南北水汽交换加强,有利于我国内陆降水增加. 相似文献
2.
IPCC第六次评估报告（AR6）显示,自20世纪起极地冰盖持续消融,全球海平面不断上升。目前对于地球冰盖未来的预测以及过去的演变历史尚不明确,而数值模拟能够提供一种有效的解决方案。在冰盖模拟研究中,冰期指数法可依据古气候代用指标将离散的气候强迫转化为连续的气候强迫,用于冰盖演变的瞬态模拟。基于该方法,利用2组（共6条）分别代表全球海平面和温度变化的代用指标,开展末次冰期旋回北半球冰盖的时空演变模拟研究,结果表明：(1)模拟的冰量演变特征受指数的变化趋势控制;(2)在指数变化特征（轨迹和变幅）相似时,千年尺度气候突变事件的存在会导致模拟的总冰量偏少;(3)在同一气候强迫下,不同指数模拟的最大冰盖范围受夏季0℃等温线的约束,同时指数的演变轨迹与变幅也会影响末次冰期盛冰期冰盖模拟的空间分布。因此,在利用冰期指数法开展冰盖瞬态模拟研究时,需根据关注的研究区域选取有代表性的指数并考虑古气候代用指标（即冰期指数）的不确定性对模拟结果的影响。 相似文献
3.
在国际古气候模拟比较设计设定的边界条件下（其中包括：海洋表面温度，陆地冰盖，CO2浓度，地球轨道参数等变化）。本文汇报了利用中国科学院大气物理研究所的9层全球大气环流格点模式对末次盛冰期气候进行数值模拟的研究成果。结果表明：末次盛冰期全球年平均温度在低5．3℃，降雨量下降9％，其中大陆年平均降水量仅为目前的71％。通过与其他模式模拟结果和重建古气候资料的对比表明，该模式捕捉到了末次盛冰期干，冷的冰期气候特征。在此基础上，我们根据刘东生等的科研成果，初步探讨了青藏高原在末次盛冰期倘若存在一定范围的冰盖，那么该冰盖会对东亚区域古气候模拟结果产生怎样的冲击。 相似文献
4.
利用CCM3/NCAR全球气候模式在21kaB.P.(2.1万年前)的末次盛冰期(LGM)气候背景下,对中国区域植被变化对夏季(6～7月)东亚季风降水的影响进行了模拟,结果表明： 在LGM时期气候背景下,植被退化会使得中国东南部夏季降水减少,其中东南沿海减少超过20mm,而在 100°E 以东的中国北方大部分地区降水增加,其中心值大于50mm,从而导致降水南少北多的现象,植被的这种影响可以从物理上得到解释。在LGM气候背景下,植被退化在暖季起着增温的作用,即通过影响地表热状况使夏季大陆增温,增强了夏季东亚大陆与其周边海域的热力差异,从而使夏季东亚地区的西南风增强,35°～45°N的北方地区对流层低层的空气辐合和对流层上升运动加强,伴随着在 30°N 以南的中国南方地区出现异常下沉运动; 同时,西南季风的加强也导致夏季在 30°～40°N 之间的华北地区低层水汽输送加大。在这些因子的共同作用下,中国北方夏季降水增多,而东南部降水减少。这些结果说明使用LGM时期中国区域不同的重建植被资料可以对东亚季风气候模拟产生一定的不确定性。因此,重建可信度高的东亚植被对于降低对气候模拟的不确定性是十分重要的。 相似文献
5.
本文依据在青藏高原存在第四纪大陆冰盖的基础上,给定了3个不同厚度的冰盖,应用弹性板模式模拟计算了大陆冰盖消融前后的地壳均衡过程。计算结果表明,由大陆冰盖消融可能引起的高原隆升最大不超过700m。因此,就整个高原的隆升幅度来说可忽略其影响。但由于冰川消融前后高原负荷发生了变化,导致了隆升速度的相应变化,因而引起地表侵蚀强弱程度的不同及其它一些地质现象是不能忽视的。 相似文献
6.
早新生代是地质史上最后一个温室气候期，随后南极冰盖形成，地球进入到晚新生代冰期。温室气候的成因和冰期气候转型的机制一直是国际相关学界关注的问题。评述国际上对此开展的古气候模拟，反映了早新生代温室气候受到了海洋和大陆的地理位置、暖海洋温盐环流和海洋热输送、太阳辐射和大气CO2浓度变化的作用和影响。古气候模拟还反映了早新生代温室气候转向冰期气候，受到了大洋通道改变和高原构造隆起、大气成分变化以及海陆生态系相互的作用和反馈。这些古气候模拟试验锁定在气候变化的关键时段和重要驱动因子，对测试地球内外驱动力和地球各圈层反馈作用提供了重要的科学依据；温室气候以及趋向冰期气候的模拟研究对探讨气候变化内在机制、预测未来气候具有重要意义。
相似文献
7.
千百年尺度气候快速变化及其数值模拟研究进展 总被引：1，自引：0，他引：1
千百年尺度全球气候快速变化是古气候研究中的一个重要内容。研究发现，末次冰期和全新世都存在着千年、百年尺度的快速气候变化，其变化幅度可以达到典型的地质变化或天文因子所造成的冰期/间冰期的气候振荡幅度，同时这些古气候事件具有全球性。对冰期和全新世气候变化的数值模拟揭示了气候系统对地球轨道参数变化的响应以及海洋、植被、冰盖、温室气体等反馈因子的重要性,其中大洋温盐环流对北大西洋淡水注入的敏感性与末次冰期和全新世气候快速变化密切相联。利用中等复杂程度的气候模式（EMIC）CLIMBER 2模拟了末次冰期典型时段（60~20 ka BP）D/O和Heinrich事件以及东亚气候的响应过程。模拟研究揭示了全新世青藏高原冰雪环境对亚洲—非洲季风气候的显著影响。今后的古气候模拟研究将在改进模式分辨率、结合古气候代用资料确定更加符合历史时期边界条件以进一步改善气候模式的基础上,更加注重气候突变机制的研究以及加强全球变化背景下的区域气候的长期变化研究。 相似文献
8.
青藏高原及毗邻山地利用冰川地貌重建古气候的研究综述 总被引：4，自引：4，他引：0
利用冰川地貌定量重建冰期时的古气候特征是探讨冰川驱动机制的关键。利用冰川地貌反演古气候的模型主要有两类：基于物质平衡线高度变化和基于估算古冰川表面物质平衡的气候重建模型,因其原理、所需数据量的不同,适用性存在着差异,应用时需根据冰川区的具体特征选取多种模型重建古气候,提高模拟的精度。青藏高原及毗邻山地已有的基于古冰川的气候重建数据显示：MIS 6以来冰川变化为气温变化驱动,冰川规模还受降水量增多的影响;MIS 3中期冰川的规模较之末次冰盛期（Last Glacial Maximum,LGM）更大,主要是该较冷的亚阶段降水比LGM时期更为丰沛所致。 相似文献
9.
利用全球海气耦合气候模式ECHO-G的近千年连续积分资料,选取与降水关系较好的东亚夏季风指数,对不同气候特征时期的东亚环流及季风影响因子进行了探讨.结果表明用海陆热力差异定义的东亚夏季风指数Isun在年际尺度上较好地体现了长江流域及华北地区降水的变化,而利用850 hPa纬向风场定义的指数Iwang在年代际尺度上较好地体现了长江流域的降水变化.从不同气候特征时期的环流来看,中世纪暖期夏季风最强,东亚大陆降水明显偏多,现代暖期夏季风较之有所减弱,而小冰期则是夏季风最弱的时期,东亚大陆的降水明显偏少.不同气候特征时期夏季风指数与海温的相关表明,ENSO事件对东亚夏季风的影响在现代暖期有所增强,而与外部强迫因子的相关揭示出中世纪暖期有效太阳辐射变化是影响东亚夏季风变化的主要因子,现代暖期则是温室气体对夏季风的影响更重要. 相似文献
10.
气候重建工作的深入开展极大地促进了全新世亚洲季风变化的研究,然而当前重建结果对亚洲季风的演变特征和机理存在很大争议,开展古气候模拟对理解全新世亚洲季风演变的时空特征和成因机制具有重要意义。为此,本文主要从气候模式模拟的角度回顾全新世亚洲季风百年-千年尺度变化的模拟研究工作,并将从外强迫和气候系统内部变率这两个角度对机制进行探讨。主要有以下进展:全新世瞬变模拟试验结果反映早全新世以来亚洲季风降水呈下降趋势,这主要受到地球轨道参数的影响,并通过改变海陆热力差异和半球间温度梯度来影响亚洲季风降水。在百年尺度弱季风事件上,模拟的8.2 ka BP时期的亚洲季风弱事件主要是由冰川融水触发,引起大西洋经向翻转环流AMOC减弱并通过大气遥相关导致季风降水减少;而4.2 ka BP时期模式模拟的亚洲弱季风事件主要是受内部变率所主导而并非外强迫因子影响。亚洲季风百年尺度变化的模拟研究主要集中在过去2 000年时段,中世纪气候异常期季风明显增强,而在小冰期逐渐减弱,太阳辐射和火山活动是影响其变化的主导因子,它们通过影响海陆热力差异、印—太海温变化来影响季风变化。 相似文献
11.
《地学前缘(英文版)》2016,7(6)
We present here a simple and novel proposal for the modulation and rhythm of ice-ages and interglacials during the late Pleistocene. While the standard Milankovitch-precession theory fails to explain the long intervals between interglacials, these can be accounted for by a novel forcing and feedback system involving CO_2, dust and albedo. During the glacial period, the high albedo of the northern ice sheets drives down global temperatures and CO_2 concentrations, despite subsequent precessional forcing maxima. Over the following millennia more CO_2 is sequestered in the oceans and atmospheric concentrations eventually reach a critical minima of about 200 ppm, which combined with arid conditions,causes a die-back of temperate and boreal forests and grasslands, especially at high altitude. The ensuing soil erosion generates dust storms, resulting in increased dust deposition and lower albedo on the northern ice sheets. As northern hemisphere insolation increases during the next Milankovitch cycle, the dust-laden ice-sheets absorb considerably more insolation and undergo rapid melting, which forces the climate into an interglacial period. The proposed mechanism is simple, robust, and comprehensive in its scope, and its key elements are well supported by empirical evidence. 相似文献
12.
At the 41,000-period of orbital tilt, summer insolation forces a lagged response in northern ice sheets. This delayed ice signal is rapidly transferred to nearby northern oceans and landmasses by atmospheric dynamics. These ice-driven responses lead to late-phased changes in atmospheric CO2 that provide positive feedback to the ice sheets and also project ‘late’ 41-K forcing across the tropics and the Southern Hemisphere. Responses in austral regions are also influenced by a fast response to summer insolation forcing at high southern latitudes.At the 22,000-year precession period, northern summer insolation again forces a lagged ice-sheet response, but with muted transfers to proximal regions and no subsequent effect on atmospheric CO2. Most 22,000-year greenhouse-gas responses have the ‘early’ phase of July insolation. July forcing of monsoonal and boreal wetlands explains the early CH4 response. The slightly later 22-K CO2 response originates in the southern hemisphere. The early 22-K CH4 and CO2 responses add to insolation forcing of the ice sheets.The dominant 100,000-year response of ice sheets is not externally forced, nor does it result from internal resonance. Internal forcing appears to play at most a minor role. The origin of this signal lies mainly in internal feedbacks (CO2 and ice albedo) that drive the gradual build-up of large ice sheets and then their rapid destruction. Ice melting during terminations is initiated by uniquely coincident forcing from insolation and greenhouse gases at the periods of tilt and precession. 相似文献
13.
J. Oerlemans 《Quaternary Research》1980,14(3):349-359
The interaction between continential ice sheets and the planetary radiation budget is potentially important in climate-sensitivity studies. A simple ice-sheet model incorporated in an energybalance climate model provides a tool for studying this interaction in a quantitative way. Experiments in which the ice-sheet model is coupled step by step to the climate model show that ice sheets hardly affect the zonal mean radiation balance because the albedo feedback due to sea ice and snow cover is dominating. The model requires a 5% drop in the solar constant to create ice sheets of ice-age size.If the feedback between surface elevation and ice-mass balance is included (in a very crude way), the ice-sheet size (L, measured southward from 70°N) becomes much more sensitive to in insolation. For a range of normalized solar constants, roughly from 0.98 to 1.02, two stable solutions exist: L 0 and L 2000 km. This result demonstrates that the response of ice sheets to insolation variations is far from linear. It also stresses the need for explicit modeling of the ice-mass balance of ice sheets, particularly its dependence on surface elevation. 相似文献
14.
Modelling palaeoglaciers in mountainous terrain is challenging due to the need for detailed ice flow computations in relatively narrow and steep valleys, high-resolution climate estimations, knowledge of pre-ice topography, and proxy-based palaeoclimate forcing. The Parallel Ice Sheet Model (PISM), a numerical model that approximates glacier sliding and deformation to simulate large ice sheets such as Greenland and Antarctica, was recently adapted to alpine environments. In an attempt to reconstruct the climate conditions during the Last Glacial Maximum (LGM) on Mount Dedegöl in SW Turkey, we used PISM and explored palaeoglacier dynamics at high spatial resolution (100 m) in a relatively small domain (225 km2). Palaeoice-flow fields were modelled as a function of present temperature and precipitation. Nine different palaeoclimate simulations were run to reach the steady-state glacier extents and the modelled glacial areas were compared with the field-based and chronologically well-established ice extents. Although our results provide a non-unique solution, best-fit scenarios indicate that the LGM climate on Mount Dedegöl was between 9.2 and 10.6 °C colder than today, while precipitation levels were the same as today. More humid (20% wetter) or arid (20% drier) conditions than today bring the palaeotemperature estimates to 7.7–8.8 or 11.5–13.2 °C lower than present, respectively. 相似文献
15.
本文试图介绍发生在非冰期,主要是全新世的突然气候变化研究所取得的进展,包括山地冰川和深海沉积物所记录的全新世突然气候变化,季风和干旱气候突然变化,以及突然气候变化与太阳变化的关系。太阳变化对整个全新世气候变化的影响似乎正愈来愈明晰起来。 相似文献
16.
《Quaternary Science Reviews》2007,26(17-18):2152-2166
High-resolution modern climate data for the Southern and Central Rocky Mountains provide a starting point for analysis of climate changes necessary to produce regional Late Pleistocene glaciation. A GIS-based model was used to assess the sensitivity of glaciation in different ranges to climatic change and the combinations of temperature and precipitation change necessary to sustain the last glacial maximum (LGM) extent of glaciation in each range. Extensive glaciation initiates first in the Wind River Range of Wyoming under every climate change scenario tested. In absence of precipitation change a summer temperature depression of 6–8 °C would be necessary to maintain LGM ice extents in Colorado and Wyoming. If precipitation was halved, necessary summer temperature depression would be 8–10 °C; if precipitation was doubled, a depression of 3.5–5.5 °C would suffice. Given model uncertainties, these values may underestimate necessary temperature depression by as much as 2 °C. Under all scenarios tested, LGM glaciation in Utah, particularly the Wasatch Range, requires either more temperature depression for given precipitation change, or more precipitation for a given temperature depression than is required in the Colorado/Wyoming Rockies. A summer temperature depression of 7 °C, which would suffice to sustain LGM ice extent with little change from modern precipitation in the Colorado/Wyoming Rockies, would need to be coupled with a near doubling of precipitation to maintain LGM ice extent in the Wasatch Range. This difference appears to reflect LGM precipitation enhancement in the Wasatch Range, and to a lesser degree the Uinta Mountains, resulting from the presence of Lake Bonneville immediately upwind of these ranges. 相似文献
17.
Colm Ó Cofaigh S. Louise Callard David H. Roberts Richard C. Chiverrell C. K. Ballantyne David J. A. Evans Margot Saher Katrien J. J. Van Landeghem Rachel Smedley Sara Benetti Matthew Burke Chris D. Clark Geoff A. T. Duller Derek Fabel Stephen J. Livingstone Stephen Mccarron Alicia Medialdea Steven G. Moreton Fabio Sacchetti 《第四纪科学杂志》2021,36(5):805-832
Understanding the pace and drivers of marine-based ice-sheet retreat relies upon the integration of numerical ice-sheet models with observations from contemporary polar ice sheets and well-constrained palaeo-glaciological reconstructions. This paper provides a reconstruction of the retreat of the last British–Irish Ice Sheet (BIIS) from the Atlantic shelf west of Ireland during and following the Last Glacial Maximum (LGM). It uses marine-geophysical data and sediment cores dated by radiocarbon, combined with terrestrial cosmogenic nuclide and optically stimulated luminescence dating of onshore ice-marginal landforms, to reconstruct the timing and rate of ice-sheet retreat from the continental shelf and across the adjoining coastline of Ireland, thus including the switch from a marine- to a terrestrially-based ice-sheet margin. Seafloor bathymetric data in the form of moraines and grounding-zone wedges on the continental shelf record an extensive ice sheet west of Ireland during the LGM which advanced to the outer shelf. This interpretation is supported by the presence of dated subglacial tills and overridden glacimarine sediments from across the Porcupine Bank, a westwards extension of the Irish continental shelf. The ice sheet was grounded on the outer shelf at ~26.8 ka cal bp with initial retreat underway by 25.9 ka cal bp. Retreat was not a continuous process but was punctuated by marginal oscillations until ~24.3 ka cal bp. The ice sheet thereafter retreated to the mid-shelf where it formed a large grounding-zone complex at ~23.7 ka cal bp. This retreat occurred in a glacimarine environment. The Aran Islands on the inner continental shelf were ice-free by ~19.5 ka bp and the ice sheet had become largely terrestrially based by 17.3 ka bp. This suggests that the Aran Islands acted to stabilize and slow overall ice-sheet retreat once the BIIS margin had reached the inner shelf. Our results constrain the timing of initial retreat of the BIIS from the outer shelf west of Ireland to the period of minimum global eustatic sea level. Initial retreat was driven, at least in part, by glacio-isostatically induced, high relative sea level. Net rates of ice-sheet retreat across the shelf were slow (62–19 m a−1) and reduced (8 m a−1) as the ice sheet vacated the inner shelf and moved onshore. A picture therefore emerges of an extensive BIIS on the Atlantic shelf west of Ireland, in which early, oscillatory retreat was followed by slow episodic retreat which decelerated further as the ice margin became terrestrially based. More broadly, this demonstrates the importance of localized controls, in particular bed topography, on modulating the retreat of marine-based sectors of ice sheets. 相似文献
18.
ERIK KJELLSTRÖM JENNY BRANDEFELT JENS‐OVE NÄSLUND BEN SMITH GUSTAV STRANDBERG ANTJE H. L. VOELKER BARBARA WOHLFARTH 《Boreas: An International Journal of Quaternary Research》2010,39(2):436-456
Kjellström, E., Brandefelt, J., Näslund, J.‐O., Smith, B., Strandberg, G., Voelker, A. H. L. & Wohlfarth, B. 2010: Simulated climate conditions in Europe during the Marine Isotope Stage 3 stadial. Boreas, 10.1111/j.1502‐3885.2010.00143.x. ISSN 0300‐9483. State‐of‐the‐art climate models were used to simulate climate conditions in Europe during Greenland Stadial (GS) 12 at 44 ka BP. The models employed for these simulations were: (i) a fully coupled atmosphere–ocean global climate model (AOGCM), and (ii) a regional atmospheric climate model (RCM) to dynamically downscale results from the global model for a more detailed investigation of European climate conditions. The vegetation was simulated off‐line by a dynamic vegetation model forced by the climate from the RCM. The resulting vegetation was then compared with the a priori vegetation used in the first simulation. In a subsequent step, the RCM was rerun to yield a new climate more consistent with the simulated vegetation. Forcing conditions included orbital forcing, land–sea distribution, ice‐sheet configuration, and atmospheric greenhouse gas concentrations representative for 44 ka BP. The results show a cold climate on the global scale, with global annual mean surface temperatures 5 °C colder than the modern climate. This is still significantly warmer than temperatures derived from the same model system for the Last Glacial Maximum (LGM). Regional, northern European climate is much colder than today, but still significantly warmer than during the LGM. Comparisons between the simulated climate and proxy‐based sea‐surface temperature reconstructions show that the results are in broad agreement, albeit with a possible cold bias in parts of the North Atlantic in summer. Given a prescribed restricted Marine Isotope Stage 3 ice‐sheet configuration, with large ice‐free regions in Sweden and Finland, the AOGCM and RCM model simulations produce a cold and dry climate in line with the restricted ice‐sheet configuration during GS 12. The simulated temperature climate, with prescribed ice‐free conditions in south‐central Fennoscandia, is favourable for the development of permafrost, but does not allow local ice‐sheet formation as all snow melts during summer. 相似文献
19.
Holocene temperature proxy records are commonly used in quantitative synthesis and model-data comparisons. However, comparing correlations between time series from records collected in proximity to one another with the expected correlations based on climate model simulations indicates either regional or noisy climate signals in Holocene temperature proxy records. In this study, we evaluate the consistency of spatial correlations present in Holocene proxy records with those found in data from the Last Glacial Maximum (LGM). Specifically, we predict correlations expected in LGM proxy records if the only difference to Holocene correlations would be due to more time uncertainty and more climate variability in the LGM. We compare this simple prediction to the actual correlation structure in the LGM proxy records. We found that time series data of ice-core stable isotope records and planktonic foraminifera Mg/Ca ratios were consistent between the Holocene and LGM periods, while time series of Uk'37 proxy records were not as we found no correlation between nearby LGM records. Our results support the finding of highly regional or noisy marine proxy records in the compilation analysed here and suggest the need for further studies on the role of climate proxies and the processes of climate signal recording and preservation. 相似文献