Estimating Climatic Timeseries From Multi-Site Data Afflicted With Dating Error     

Craig Loehle 《Mathematical Geology》2005,37(2):127-140

Timeseries of estimated temperature have been combined to create global or hemispheric climate series over periods exceeding 1000 yr. The data used in these studies, however, may be subject to dating errors. It is shown that when timeseries with dating error are combined, the noise in the data smoothes periodic signals but leaves linear trends intact. This means that the effect of dating error of sample data in a timeseries reconstruction is to smooth out any signals (waves, cycles) that may be present. The purpose of this study was to develop signal extraction methods that will work for this type of historical data. The method used was nonlinear estimation of sample series where dating error has been added by Monte Carlo sampling. Several algorithms were tested for handling the dating error problem. Results were that using nonlinear model fitting, the periods of signals can be identified even from the averaged data. In a second stage of the estimation procedure, the cycle magnitudes can be estimated. Very good fits were achieved for two example cases. Temperature estimation error (white noise due to the use of proxies) was also considered and the method was extended to cover this case with quite good results. Using the new estimation methods, the information inherent in multiple series can be used to overcome the problem of dating error.  相似文献   

Orbital‐ and millennial‐scale climate and vegetation changes between 32.5 and 6.9k cal a BP from Hanon Maar paleolake on Jeju Island,South Korea          下载免费PDF全文

JUNGJAE PARK  HYOUN SOO LIM  JAESOO LIM  KEUN BAE YU  JINMU CHOI 《第四纪科学杂志》2014,29(6):570-580

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Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis     

H. Elderfield  J. Yu  P. Anand  T. Kiefer  B. Nyland   《Earth and Planetary Science Letters》2006,250(3-4):633-649

Benthic foraminiferal magnesium/calcium ratios were determined on one hundred and forty core-top samples from the Atlantic Ocean, the Norwegian Sea, the Indian Ocean, the Arabian Sea and the Pacific Ocean, mostly at sites with bottom water temperatures below 5 °C. Mg/Ca ratios are consistently lower, by  0.2 mmol/mol, in samples cleaned using oxidative and reductive steps than using oxidative cleaning. Differences between Cibicidoides species have been identified: Mg/Ca of Cibicidoides robertsonianus > Cibicidoides kullenbergi > Cibicidoides wuellerstorfi. Comparison with bottom water temperatures support observations of lowered Mg/Ca of C. wuellerstorfi at temperature below  3 °C compared with values predicted by published calibrations and from other Cibicidoides species. Hydrographic data shows that carbonate ion saturation (Δ[CO₃²⁻]) decreases rapidly below this temperature. An empirical sensitivity of Δ[CO₃²⁻] on Mg/Ca has been established for C. wuellerstorfi of 0.0086 ± 0.0006 mmol/mol/μmol/kg. A novel application using modern temperatures and Last Glacial Maximum temperatures derived via pore fluid modelling supports a carbonate ion saturation state effect on Mg incorporation. This may significantly affect calculated δ¹⁸O_seawater obtained from foraminiferal δ¹⁸O and Mg/Ca temperature.  相似文献   

小冰期气候研究回顾和机理探寻   总被引：4，自引：0，他引：4  

宋燕  季劲钧  王月宾  王沛涛 《气象》2003,29(7):3-6

回顾了古气候学中利用代用气象资料对小冰期气候重建的研究结果，归纳出小冰期时期全球气候特征及东亚季风区域气候特征，分析了小冰期气候形成的可能原因，介绍了国外有关小冰期气候成因的数值模拟现状，并对未来模拟工作发展方向提出了建议。  相似文献   

Constraining recycled detritus in quartz‐rich sandstones: Insights from a multi‐proxy provenance study of the Mid‐Carboniferous,Clare Basin,western Ireland     

Martin Nauton‐Fourteu  Shane Tyrrell  Andrew Morton  Chris Mark  Gary J. O&#x;Sullivan  David M. Chew 《Basin Research》2021,33(1):342-363

Quartz‐rich sandstones can be produced through multiple sedimentary processes, potentially acting in combination, such as extensive sedimentary recycling or intense chemical weathering. Determining the provenance of such sedimentary rocks can be challenging due to low amounts of accessory minerals, the fact that the primary mineralogy may have been altered during transport, storage or burial and difficulties in the recognition of polycyclic components. This study uses zircon and apatite U‐Pb geochronology, apatite trace elements, zircon‐tourmaline‐rutile indices and petrographic observations to investigate the sedimentary history of mineralogically mature mid‐Carboniferous sandstones of the Tullig Cyclothem, Clare Basin, western Ireland. The provenance data show that the sandstones have been dominantly and ultimately sourced from three basement terranes: older Laurentian‐ associated rocks (ca. 900–2500 Ma) which lay to the north of the basin, peri‐Gondwanan terranes (ca. 500–700 Ma) to the south and igneous intrusive rocks associated with the Caledonian Orogenic Cycle (ca. 380–500 Ma). However, the multi‐proxy approach also helps constrain the sedimentary history and suggests that not all grain populations were derived directly from their original source. Grains with a Laurentian or a Caledonian affinity have likely been recycled through Devonian basins to the south. Grains with a peri‐Gondwanan affinity appear to be first cycle and are potentially derived from south/southwest of the basin. Taken as a whole, these data are consistent with input into the basin from the south and southwest, with the reworking of older sedimentary rocks, rather than intensive first‐cycle chemical weathering, likely explaining the compositional maturity of the sandstones. This study highlights the need for a multi‐proxy provenance approach to constrain sedimentary recycling, particularly in compositionally mature sandstones, as the use of zircon geochronology alone would have led to erroneous provenance interpretations. Zircon, together with U‐Pb geochronology from more labile phases such as apatite, can help distinguish first‐cycle versus polycyclic detritus.  相似文献   

Modelling the regional climate and isotopic composition of Svalbard precipitation using REMOiso: a comparison with available GNIP and ice core data     

D. V. Divine  J. Sjolte  E. Isaksson  H. A. J. Meijer  R. S. W. van de Wal  T. Martma  V. Pohjola  C. Sturm  F. Godtliebsen 《水文研究》2011,25(24):3748-3759

Simulations of a regional (approx. 50 km resolution) circulation model REMO_iso with embedded stable water isotope module covering the period 1958‐2001 are compared with the two instrumental climate and four isotope series (δ¹⁸O) from western Svalbard. We examine the data from ice cores drilled on Svalbard ice caps in 1997 (Lomonosovfonna, 1250 m asl) and 2005 (Holtedahlfonna, 1150 m asl) and the GNIP series from Ny‐Ålesund and Isfjord Radio. The surface air temperature (SAT) and precipitation data from Longyearbyen and Ny‐Ålesund are used to assess the skill of the model in reproducing the local climate. The model successfully captures the climate variations on the daily to multidecadal times scales although it tends to systematically underestimate the winter SAT. Analysis suggests that REMO_iso performs better at simulating isotope compositions of precipitation in the winter than summer. The simulated and measured Holtedahlfonna δ¹⁸O series agree reasonably well, whereas no significant correlation has been observed between the modelled and measured Lomonosovfonna ice core isotopic series. It is shown that sporadic nature as well as variability in the amount inherent in precipitation process potentially limits the accuracy of the past SAT reconstruction from the ice core data. This effect in the study area is, however, diminished by the role of other factors controlling δ¹⁸O in precipitation, most likely sea ice extent, which is directly related with the SAT anomalies. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

湖北辽瓦店遗址地层中多元素指标对古人类活动的记录   总被引：3，自引：0，他引：3  

李中轩  朱诚  王然  欧阳杰  张广胜  马春梅 《海洋地质与第四纪地质》2008,28(6)

用ICP—AES和XRF方法测试了湖北辽瓦店遗址T0709地层中对人类活动有指示意义的元素含量，恢复了夏代以来遗址地层记录的人类活动特征：（1）夏代文化层（250～325cm）时期是整个剖面的最湿热阶段，人类活动对自然环境干扰相对有限，生态系统良好。（2）东周文化层下段（205～250cm）仍是相对湿热的环境，磁化率大幅上升，人类活动的强度加大。其中220cm处的K、Mn、Sr、Ba含量骤降，说明该层段可能因自然灾害等原因曾被废弃。而在205cm处地层中8种元素的含量快速升高，表明在下东周文化层中期人类活动异常频繁。东周文化层上段（120～205cm）气候变冷、风化作用减弱，Pb含量的异常和Cu含量高值暗示遗址有青铜器制造活动的遗迹。（3）明清文化层（70～120cm）时期气候干冷。本期地层中除Cu含量无显著变化外，Ba、Ca、P、Pb、Sr、Mn、K均有高值层位，而且本层位磁化率较高，这表明该时期人类活动的繁荣。同时，本层中含有陶片和瓷片以及较高的Pb含量，说明遗址在明清时期曾有瓷器作坊的历史；而Cu含量的低值则表明青铜器的制造和使用已丧失了原有的地位。  相似文献   

气候变化对中国古代财政平衡的影响   总被引：2，自引：1，他引：1  

魏柱灯  方修琦  苏筠 《地理科学》2015,35(9):1156-1163

以当代历史和经济史著作为资料,建立与历朝财政盈亏状态相关词汇的语义分级标准,重建了中国自秦朝至清末（220 BC~1910 AD）10 a分辨率的财政等级序列,并分析其与气候变化的关系。结果表明,秦朝至清末的财政平衡大体经历了4个相对充裕阶段（220 BC~31 BC,441~760 AD,961~1210 AD,1381~1910 AD）和3个相对匮乏阶段（30 BC~440 AD,761~960 AD,1211~1380 AD）。财政危机在寒冷-干旱的气候背景下爆发的可能性最大。财政平衡与温度和降水变化均成正相关,财政平衡的趋势性变化受长期的温度和降水变化影响较为明显。但受多因素的复杂反馈环节影响,两者在某些时段呈现反相位关系。  相似文献   

Rapid societal change as a proxy for regional environmental forcing: Evidence and explanations for Pacific island societies in the 14–15th centuries          下载免费PDF全文

James Goff  Patrick D. Nunn 《Island Arc》2016,25(5):305-315

Given the unquestioned impacts of recent/future environmental changes on human societies, it is reasonable to posit that past societal responses could be used as proxies of contemporaneous environmental forcing and might help identify the drivers of these, particularly where independent evidence of the effects of these events is inadequate. Such areas include Pacific oceanic islands for most of which there is evidence of a societal perturbation in the 14th and 15th centuries that saw the outbreak of region‐wide conflict, abandonment of coastal settlements and the abrupt end of long‐distance cross‐ocean voyaging networks. The contemporaneity of these effects across a vast region requires a driver that is external to particular island groups with the only possibility that of oceanic origin, most likely large waves (tsunamis or storm surges) or rapid sea‐level change. The explanation is less important than the principle that societal changes can be used as proxies for environmental activity.  相似文献   

河蚬壳体与水体的无机碳同位素关系     

闫慧  殷学永 《热带地理》2012,32(6):613-617

河流溶解无机碳对于评价区域水环境的碳循环具有重要意义,若能获得古水体DIC的地球化学特征,则可以为重建过去环境变化提供大量基础数据,因此寻找δ¹³C_DIC替代指标十分迫切。对花溪河淡水双壳类河蚬进行了室内养殖研究,结果表明：河蚬壳体碳同位素与生长期间水体δ¹³C_DIC存在显著正相关关系,δ¹³C_DIC是影响δ¹³C_shell的重要因素,壳体记录了其形成时期水体的信息,δ¹³C_shell可以用作δ¹³C_DIC定性的替代指标来区分具有不同δ¹³C_DIC值的水环境。由于新陈代谢作用的影响,利用δ¹³C_shell重建的δ¹³C_DIC值与真实的δ¹³C_DIC值相比,平均偏负约2.00‰,且这种差异随着河蚬年龄的增大而增大,因此δ¹³C_shell不能够直接用来定量提取水体δ¹³C_DIC。  相似文献