共查询到18条相似文献，搜索用时 922 毫秒
1.
南海南部50万年以来碳酸钙和有机碳记录及其揭示的东亚夏季风演化 总被引：1，自引：0，他引：1
为了解南海南部第四纪冰期旋回中表层生产力的变化与东亚夏季风的演化关系,通过对南海南部MD05-2897孔晚第四纪500ka以来碳酸钙和有机碳含量及堆积速率高分辨率的研究发现,碳酸钙含量及堆积速率表现出明显的冰期-间冰期旋回变化,而有机碳的含量及堆积速率则主要呈现频率更高的周期性变化.碳酸钙和有机碳含量及堆积速率都在间冰期时增加,冰期时降低,反映了间冰期时夏季风的增强导致上升流的加强和营养物质的增加,促使表层生产力提高.碳酸钙和有机碳含量及堆积速率具有100ka偏心率周期、40ka斜率周期、20ka岁差和10ka半岁差周期等最为丰富的频谱,显示出低纬海区对轨道周期响应的特色.碳酸钙和有机碳的堆积速率与北半球低纬夏季日射量吻合较好,说明岁差相关的北半球低纬夏季太阳辐射量的变化可能是东亚夏季风强度变化的主要控制因素,而与全球冰量相关的气候变化可能是次要因素. 相似文献
2.
显生宙沉积旋回会受到地球轨道参数偏心率、地轴斜率和岁差的周期性变化(米兰科维奇旋回)的控制,但目前对前寒武系的相关研究较为薄弱。天津蓟县剖面中元古界洪水庄组-铁岭组为一套潟湖-潮坪相沉积,主要呈砂岩-页岩互层的韵律性产出。为探索这种岩性韵律是否与轨道旋回有关,对其进行了高分辨率的岩性刻画,并以磁化率和伽马能谱数据作为古气候-古环境替代性指标,通过频谱分析等方法进行旋回地层学分析。结果表明各指标均记录了完整的米兰科维奇旋回。铁岭组一段下部由短偏心率、斜率和岁差控制的地层旋回厚度分别为1.2~1.5 m、0.4 m和0.17~0.19 m,其中0.1 m的半岁差周期也较明显;洪水庄组二段顶部由长偏心率、短偏心率、斜率和岁差控制的地层旋回厚度分别为1.1~1.8 m、0.34~0.54 m、0.14~0.16 m和0.08~0.09 m。以识别出的稳定长偏心率周期405 ka旋回对洪水庄组进行了天文年代校准,并估计出当时的短偏心率、斜率以及岁差周期分别为100 ka、22~24 ka和15 ka。在洪水庄组中记录的偏心率振幅变化周期为~2 Ma,比现今~2.4 Ma的周期略短。 相似文献
3.
气候变化轨道驱动的发现,使古气候研究进入了定量探索变化机理的新阶段。然而经典版本的米兰科维奇学说只考虑北半球高纬区的辐射量变化,与新发现的地质记录和热带过程在现代气候中所起的作用相矛盾。文章简要地综述以贸易风与季风系统为主的低纬过程如何响应轨道变化,指出岁差与偏心率周期通过驱动热带过程影响全球气候的重要性,建议在古气候研究中发展新思路,重视区别高、低纬区不同过程的轨道周期,从高、低纬区相互作用的角度研究气候变化的机理。 相似文献
4.
《地球科学进展》2016,(3)
首先综述了现代热带海洋生产力的分类与影响因素,然后讨论了古生产力替代性指标的分类与各类方法的优点与局限性。在此基础上,通过收集整理前人使用不同替代性指标对热带海洋古生产力重建的结果,讨论了热带海洋古生产力记录的特征、周期性与驱动机制。发现从末次冰期到全新世热带海洋古生产力在冰期时明显偏高,但冰期生产力高间冰期生产力低的规律并不一直适用,MIS 22前后西太平洋初级生产力在冰期—间冰期的变化发生反转。热带海洋古生产力的周期性也与高纬海区显著不同,岁差和斜率的信号更为显著。还存在约30 ka等不同轨道周期叠加之后形成的周期。颗石藻计算的海洋生产力可能存在约400 ka周期,这对全球碳同位素的影响有待深入研究。 相似文献
5.
1100万年以来中国北方风尘堆积与古气候变化的周期及驱动因素分析 总被引：3，自引：0，他引：3
中国北方连续堆积的晚新生代风成红粘土-黄土,是气候干湿变化的良好地质记录.对第四纪黄土的研究,揭示了中国北方干湿的周期变化,但是中新世以来的古气候变化规律及其驱动机制还不清楚.通过对具有代表性的红粘土-黄土序列的粒度测试,并根据独立的古地磁地层年代控制,建立了我国北方1100万年以来气候变化的时间序列.在此基础上,应用传统谱分析和小波变换的方法,对1100万年以来的干湿变化进行了分析,讨论了11～7.3 Ma,8.0～5.0 Ma,5.3～2.5 Ma,2.5～1.2 Ma和1.2～O Ma期间我国北方和亚洲中部干湿变化的周期,发现在不同时间段分别存在着～20 ka的岁差周期、～40 ka的黄赤交角周期和～100 ka的地球轨道偏心率周期,获得了地球轨道运动变化引起太阳辐射变化驱动晚新生代亚洲内陆干湿变化的新证据.同时,还发现风尘沉积的粒度时间序列存在非轨道周期,可能是轨道周期谐振和时间标尺不确定性造成的.地球轨道运动变化引起的北半球太阳辆射量的变化,从而引起北半球冰期-间冰期旋回、西风带位置移动和亚洲季风强度的共同变化,可能控制着晚新生代我国北方粉尘沉积过程和古气候变化.加强粉尘堆积记录和古气候模拟研究,可深入认识我国北方晚新生代干湿变化的规律和机制. 相似文献
6.
认识偏心率周期的地层古气候意义 总被引：15，自引：0，他引：15
介绍了偏心率周期在地层和古气候研究方面的新发展.现有地球轨道模式对250Ma以来的轨道运算误差能控制在0.2%之内, 使基于偏心率周期来划分地层年代成为可能.新的国际标准地层年代表以405ka长偏心率周期为基础来划分主要地层界线.新生代将包括E1-E162偏心率长周期, 底界年龄(65.5±0.3) Ma.这一地层年代表的建立, 标志着轨道地层学时代的到来.偏心率的100ka短周期和405ka长周期在诸多地质记录中都有反映, 特别是来自深海钻孔的物理化学古气候指标.很多古气候重大事件往往发生在偏心率周期的弱振幅时期, 表明弱振幅时期易受其他因素的干扰影响, 这些因素包括碳储库、冰盖和海平面变化、电磁场, 以及区域构造重组等等.越来越多的研究发现碳同位素在偏心率周期上与地球轨道驱动相关, 且常领先于氧同位素的变化, 表明热带碳循环过程是影响全球气候变化的关键因素之一. 相似文献
7.
8.
珊瑚礁能够灵敏地记录过去气候变化过程，对于长尺度气候记录而言，高精度的地层年代框架能为区域和全球事件对比提供精确的年代约束。文章以南海西沙群岛琛科2井的珊瑚礁钻孔为研究材料，选取对沉积旋回反应灵敏的非磁滞剩磁(ARM)作为气候替代指标进行旋回分析。ARM分段深度域频谱分析结果显示其存在稳定的代表斜率调制周期约1.2 Ma和长偏心率周期约405 ka的沉积旋回。基于以上识别出的沉积旋回，分别利用轨道参数理论滤波曲线对0～878.21 m的深度域ARM数据序列进行分段天文调谐。最终将珊瑚礁起始发育的天文年代厘定为约19.2 Ma,分辨率可以达到十万年的轨道尺度，可以与Sr同位素年代相互校准。时间域的ARM频谱分析发现，整个中新世以来约1.2 Ma的斜率调制周期在南海珊瑚礁沉积地层中最明显，约405 ka和约95 ka的偏心率周期及约173 ka的斜率调制短周期均不连续。这表明斜率调控的百万年尺度的轨道周期可能对南海珊瑚礁的演化起着主要的调控作用，而珊瑚礁沉积记录的主控周期的改变可能是其对南北半球冰川作用气候效应的及时响应。 相似文献
9.
全球大洋深海有孔虫碳同位素(δ13C)记录中广泛发现40万年周期,这一周期可能与偏心率长周期的轨道驱动有关.1.6 Ma以来,δ13C的这一长周期拉长到50万年,且重值期不再与偏心率低值对应.目前对δ13C 40万年周期的成因及其周期拉长的机制还不明确.这里使用了包含9个箱体的箱式模型,用于研究热带过程与冰盖相互作用及其对大洋碳循环的影响.模拟结果显示当北半球高纬海区海冰迅速增大时冰盖迅速融化,进入冰消期,而当海冰快速消失后,冰盖则重新缓慢增长.冰盖变化具有冰期长,间冰期短的非对称形态.在季节性太阳辐射量的驱动下冰盖变化具有10万年冰期-间冰期旋回.当冰盖融化速率受北半球高纬夏季太阳辐射量控制时,冰盖变化的岁差周期明显加强,相位与地质记录一致,说明轨道驱动可以通过非线性相位锁定机制使冰盖变化与其在相位上保持一致.海冰的阻隔效应使大气中CO2在冰消期时增多.冰期时大洋环流减弱使大气中CO2逐渐减少.当模型只有ETP驱动的风化作用而不考虑冰盖变化时,模拟的δ13C记录显示极强的40万年周期,体现了大洋碳储库对热带风化过程的响应.当同时考虑冰盖变化和风化作用时,模拟的δ13C结果中40万年周期减弱而10万年周期加强,并且40万年周期上碳储库与偏心率的相位与不考虑冰盖变化时的相位也存在差异,反映了冰盖变化引起的洋流改组压制了大洋碳循环对热带过程的响应. 相似文献
10.
YIN Zhi-qiang ) HAN Yan-ben ) XU Dao-yi ) YAO Yi-Min ) HAN Yong-gang ) ) National Astronomical Observatories Chinese Academy of Sciences Beijing ) Institute of Geology China Earthquake Administration Beijing ) Geological Scientific Research Institute of Shengli Oilfield Company SINOPEC Dongying 《地层学杂志》2007,(Z2)
地球轨道要素的变化已作为确定地质年表的一种重要依据。应用地球轨道参数变化理论计算值来进行小波分析,结果清楚地展示出偏心率值约100ka、405ka、1Myr和2.3Myr等周期成份的随时间变化特征,100ka和405ka周期的振幅强度的变化成反相位关系,2.3Myr周期对100ka和405ka周期成份有调制作用。0—51Ma范围内变化较为稳定的地球轨道偏心率值的变化分析可以为地质年龄的划分和对比提供一定的参考。 相似文献
11.
《Quaternary Science Reviews》2003,22(15-17):1597-1629
The SPECMAP models of orbital-scale climate change (Imbrie et al., Paleoceanography 7 (1992) 701, Paleoceanography 8 (1993) 699) are the most comprehensive to date: all major climatic observations were analyzed within the framework of the three orbital signals. Subsequently, tuning of signals in Vostok ice to insolation forcing has fixed the timing of greenhouse-gas changes closely enough to permit an assessment of their orbital-scale climatic role. In addition, evidence from several sources has suggested changes in the SPECMAP δ18O time scale. This new information indicates that the timing of CO2 changes at the periods of precession and obliquity does not fit the 1992 SPECMAP model of a “train” of responses initiated in the north, propagated to the south, and later returning north to force the ice sheets. In addition, analysis of the effects of rectification on 100,000-year climatic signals reveals that all have a phase on or near that of eccentricity. This close clustering of phases rules out the long time constants for 100,000-year ice sheets required by the 1993 SPECMAP model.A new hypotheses presented here revives elements of an earlier CLIMAP view (Hays et al., Science 194 (1976a) 1121) but adds a new assessment of the role of greenhouse gases.As proposed by Milankovitch, summer (mid-July) insolation forces northern hemisphere ice sheets at the obliquity and precession periods, with an ice time constant derived here of 10,000 years. Changes in ice volume at 41,000 years drive ice-proximal signals (SST, NADW, dust) that produce a strong positive CO2 feedback and further amplify ice-volume changes. At the precession period, July insolation forces ice sheets but it also drives fast and early responses in CH4 through changes in tropical monsoons and boreal wetlands, and variations in CO2 through southern hemisphere processes. These CH4 and CO2 responses enhance insolation forcing of ice volume.Climatic responses at 100,000 years result from eccentricity pacing of forced processes embedded in obliquity and precession cycles. Increased modulation of precession by eccentricity every 100,000 years produces 23,000-year CO2 and CH4 maxima that enhance ablation caused by summer insolation and drive climate deeper into an interglacial state. When eccentricity modulation decreases at the 100,000-year cycle, ice sheets grow larger in response to obliquity forcing and activate a 41,000-year CO2 feedback that drives climate deeper into a glacial state. Alternation of these forced processes because of eccentricity pacing produces the 100,000-year cycle. The 100,000-year cycle began 0.9 Myr ago because gradual global cooling allowed ice sheets to survive during weak precession insolation maxima and grow large enough during 41,000-year ice-volume maxima to generate strong positive CO2 feedback.The natural orbital-scale timing of these processes indicates that ice sheets should have appeared 6000–3500 years ago and that CO2 and CH4 concentrations should have fallen steadily from 11,000 years ago until now. But new ice did not appear, and CO2 and CH4 began anomalous increases at 8000 and 5000 years ago, respectively. Human generation of CO2 and CH4 is implicated in these anomalous trends and in the failure of ice sheets to appear in Canada. 相似文献
12.
The classification and influencing factors of modern marine productivity were reviewed at the beginning. We discussed the pros and cons of different paleoproductivity proxies. Based on these discussions, we collected paleoproductivity reconstructions in tropical marine from previous studies and focus on the glacial-interglacial features, periodicity and forcing mechanisms of tropical marine productivity. We found that the productivity in most tropical sites decreased from MIS 2 to MIS 1. The productivity was not always higher in glacial: The glacial-interglacial pattern of productivity turned at MIS 22 in western Pacific. There were remarkable differences between tropical productivity and high latitude productivity. The precession and obliquity bands were more significant in tropical productivity and ~30 ka cycles caused by the superimposing of different orbital cycles were common in tropical. The coccolith based productivity seemed to have a quasiperiod of 400 ka and more researches are needed to discover the relationship between productivity and global 13C in this band. 相似文献
13.
V. A. Bol’shakov 《Stratigraphy and Geological Correlation》2014,22(5):538-551
The study demonstrates that the orbital climatic diagram (OCD) built on the basis of the simplified and general concepts of mechanisms for climatic response to orbital forcing can be a reasonable alternative to Milankovitch’s and his followers’ discrete insolation curves, which are widely used in paleoclimate interpretations. Comparison of the OCD and the oxygen isotope record LR04 indicates a fairly good match (considering the simplicity of the OCD construction and interpretation) in 0–1240 ka. The study discusses some discrepancies in the chronology and structure of the LR04 and OCD. It was shown that climate response may differ from that predicted by orbital insolation forcing on the basis of the generally accepted mechanisms causing transformation of orbital signals. It was shown that a shift from a dominant glacial periodicity of 41 to 100 k.y. (Middle Pleistocene transition) took place at ～1240 ka. Since then, the 100-k.y. eccentricity cycle has not been interrupted. Therefore, strictly speaking, the revised numbering of marine isotope stages (MIS) should be adopted for the interval of 1240-900 ka to reflect realistic 100-k.y. cycles instead of 41-k.y. cycles, similar to the interval of 900–100 ka. 相似文献
14.
TianJun WangPinxian ChengXinrong 《中国地质大学学报(英文版)》2004,15(3):283-289
The continuous wavelet transform (CWT) analysis reveals the instantaneous variability of the foraminiferal δ18O and δ13C of Site 1143 for the past 5 Ma at the eccentricity, obliquity and precession bands. The cross CWT analysis further demonstrates nonstationary phases of the benthic -δ18O relative to ETP at the three primary Milankovitch bands in the last 5 Ma. The instantaneous phases between benthic -δ18O and δ13C at the precession band display a prominent 128 ka period, probably the cyclicity of the nonstationary climate close to the eccentricity. To explain these nonstationary phases, it is desirable to introduce a nonlinear response model to the global climate system, in which the output has a prominent cycle around 100 ka to match the 128 ka cycle of the instantaneous phase of the δ13C and -δ18O on the precession band. 相似文献
15.
基于米兰科维奇天文旋回理论在三角洲前缘开展砂岩组和单层级别的油层对比研究,频谱分析和小波变换揭示萨尔图油层Ⅲ油层组存在米兰科维奇天文旋回,可识别出比值接近5∶2∶1的3个旋回厚度,分别对应于偏心率100 ka、斜率40 ka和岁差20 ka周期,推测地层在沉积时受到米兰科维奇天文轨道周期性变化的影响。根据岁差20 ka周期带通滤波（BPF）和堆积速率变化特征,将萨尔图油层Ⅲ油层组划分为9个砂岩组和20个单层。研究表明,岁差20 ka周期调控气候波动的机制与超短期基准面升降变化之间存在着一定的协调作用,利用米兰科维奇天文旋回划分出的单层具有严格的等时性。20个单层砂体的展布特征表明,萨尔图油层Ⅲ油层组经历了多期水进—水退事件,与砂岩组的划分具有较好的对应关系。 相似文献
16.
Since the Mid Pleistocene Revolution, which occurred about one million years ago, global temperatures have fluctuated with a quasi‐periodicity of ca. 100 ka. The pattern of past change in the extent of woodlands, and therefore by inference vegetation carbon storage, has been demonstrated to have a strong positive link with this global temperature change at high and mid latitudes. However, understanding of climate systems and ecosystem function indicates that the pattern of woodland change at low latitudes may follow a fundamentally different pattern. We present output from the intermediate complexity model GENIE‐1, comprising a single transient simulation over the last 800 ka and a 174‐member ensemble of 130 ka transient simulations over the last glacial cycle. These simulations suggest that while vegetation carbon storage in mid–high northern latitudes robustly follows the characteristic ca. 100 ka cycle, this signal is not a robust feature of tropical vegetation, which is subject to stronger direct forcing by the precessional (21 ka) orbital cycle (albeit with a highly uncertain response). We conclude that the correlation of palaeoenvironmental records from low latitudes with global temperature change must be done with caution. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
17.
《Quaternary Science Reviews》2007,26(13-14):1713-1724
Continuous high-resolution pollen data for the past 225 ka from sediments in Bear Lake, Utah–Idaho reflect changes in vegetation and climate that correlate well with variations in summer insolation and global ice-volume during MIS 1 through 7. Spectral analysis of the pollen data identified peaks at 21–22 and 100 ka corresponding to periodicities in Earth's precession and eccentricity orbital cycles. Suborbital climatic fluctuations recorded in the pollen data, denoted by 6 and 5 ka cyclicities, are similar to Greenland atmospheric temperatures and North Atlantic ice-rafting Heinrich events. Our results show that millennial-scale climate variability is also evident during MIS 5, 6 and 7, including the occurrence of Heinrich-like events in MIS 6, showing the long-term feature of such climate variability. This study provides clear evidence of a highly interconnected ocean–atmosphere system during the last two glacial/interglacial cycles that extended its influence as far as continental western North America. Our study also contributes to a greater understanding of the impact of long-term climate change on vegetation of western North America. Such high-resolution studies are particularly important in efforts of the scientific community to predict the consequences of future climate change. 相似文献
18.
Milankovitch theory posits that Earth's orbital cycles were the primary forcing of Pleistocene ice-age cycles through their strong influence on summer insolation at high latitudes. Accordingly, Milankovitch theory predicts ice volume should vary at both obliquity and precessional periods. However, early Pleistocene global ice volume varied mainly at the obliquity period with weak variability at the precessional period suggesting that Milankovitch theory is not sufficient to explain the ice-age cycles. Here we describe the results from a series of coupled ocean-atmosphere general circulation model experiments, using the Fast Ocean Atmosphere Model, that systematically investigate the influence of precession and obliquity on continental snowfall and potential ablation.Our model results identify three factors that magnify the influence of obliquity forcing on the global ice volume: First, high-latitude snowfall variability is dominated by changes in Earth's axial tilt. Second, hemispheric changes in net snowfall due to Earth's precession are out-of-phase, and largely cancel to produce a very small global snowfall change. Third, snowmelt variability over Antarctica responds greatly to changes in obliquity that intensify accumulation over obliquity cycle. We discuss the implications of these factors for existing hypotheses that account for the variability in the ice volume record. 相似文献