Solar and proxy-sensitivity imprints on paleohydrological records for the last millennium in west-central Europe     

M. Magny  F. Arnaud 《Quaternary Research》2010,73(2):173-179

This paper presents a lake-level record established for the last millennium at Lake Saint-Point in the French Jura Mountains. A comparison of this lake-level record with a solar irradiance record supports the hypothesis of a solar forcing of variations in the hydrological cycle linked to climatic oscillations over the last millennium in west-central Europe, with higher lake levels during the solar minimums of Oort (around AD 1060), Wolf (around AD 1320), Spörer (around AD 1450), Maunder (around AD 1690), and Dalton (around AD 1820). Further comparisons of the Saint-Point record with the fluctuations of the Great Aletsch Glacier (Swiss Alps) and a record of Rhône River floods from Lake Bourget (French Alps) give evidence of possible imprints of proxy sensitivity on reconstructed paleohydrological records. In particular, the Great Aletsch record shows an increasing glacier mass from AD 1350 to 1850, suggesting a cumulative effect of the Little Ice Age cooling and/or a possible reflection of a millennial-scale general cooling until the mid-19th century in the Northern Hemisphere. In contrast, the Saint-Point and Bourget records show a general trend toward a decrease in lake levels and in flood magnitude anti-correlated with generally increasing solar irradiance.  相似文献   

近千年来三个气候特征时期东亚夏季风的模拟对比     

况雪源  刘健  林惠娟  王红丽  提汝媛 《地球科学进展》2010,25(10):1082-1090

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   

Cosmogenic isotope (Cl) surface exposure dating of the Norber erratics, Yorkshire Dales: Further constraints on the timing of the LGM deglaciation in Britain     

Peter J. Vincent  Peter Wilson  Tom C. Lord  Christoph Schnabel 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(1):24-31

Cosmogenic isotope (³⁶Cl) surface exposure dating of four of the erratic boulders at Norber in the Yorkshire Dales National Park, northwest England, yielded mean ages of ∼22.2 ± 2.0 ka BP and ∼18.0 ± 1.6 ka BP for their emplacement. These two mean values derive from different ³⁶Cl production rates used for exposure age calculation. The ages are uncorrected for temporal variations in production rates and may underestimate the true ages by 5-7%. The former age, although implying early deglaciation for this area of the British ice sheet, is not incompatible with minimum deglaciation ages from other contexts and locations in northwest England. However, the latter age is more consistent with the same minimum deglaciation ages and geochronological evidence for ice-free conditions in parts of the northern sector of the Irish Sea. Within uncertainties, the younger of the mean ages from Norber may indicate that boulder emplacement was associated with North Atlantic Heinrich event 1. The limited spatial (downvalley) extent of the Norber boulders implies that at the time of their deposition the ice margin was coincident with the distal margin of the erratic train. Loss of ice cover at Norber was followed by persistent stadial conditions until the abrupt opening of the Lateglacial Interstadial when large carnivorous mammals colonised the area. The ³⁶Cl ages are between ∼3.0 ka and ∼13.0 ka older than previous estimates based on rates of limestone dissolution derived from the heights of pedestals beneath the erratics.  相似文献   

近50 a中国霜期的变化特征分析   总被引：7，自引：3，他引：4  

许艳  王国复  王盘兴 《气象科学》2009,29(4):427-433

通过对中国霜气象观测资料的整理和分析,研究了1957-2006年中国霜期、初霜日、终霜日的时空分布和气候特征.结果表明,中国各地的霜期总体上是自北向南、自高山向平原逐渐缩短的,霜期长(短)的地区与初霜早(晚)、终霜晚(早)的地区非常一致.近50 a来,在全球增暖的背景下,中国大部分地区霜期在逐渐缩短,初霜日在逐渐推迟,终霜日在不断提前,1990s后这种趋势变得更加明显.霜期缩短显著的区域主要集中在我国东北、华北、内蒙古中部、江淮流域以及云贵高原和华南部分地区,而四川盆地和长江中下游部分地区霜期缩短的趋势并不明显,一些地方甚至略有延长的趋势.比较初霜日期与终霜日期的趋势变化,发现终霜日提前的趋势要比初霜日推后的趋势更加明显,这可能是由不同季节的增温幅度不同而引起的.  相似文献   

富县地区末次间冰期以来古气候环境的演变     

柯曼红  孙建中  赵景波 《地球科学与环境学报》1993,(4)

研究剖面位于洛川源北部的富县县城东郊。剖面由第一层古土壤(S_1)、马兰黄土(L_1)和全新世古土壤(S_0)组成。孢粉分析结果表明,黄土地层中孢粉非常丰富,为恢复古植被与古气候提供了可靠依据。S_1的植被是以榛、菊、蒿为主的疏林草原,有亚热带树种出现,反映了末次冰期的温湿气候。L_1时主要为菊、蒿干草原,气候冷干,其间有四次乔木增多期,反映了末次间冰期中有四次间冰阶的相对温湿气候波动。近代耕土中为以松、藜、中华卷柏为主的森林草原,反映了全新世某个时期比较温凉干旱的气候。  相似文献   

Relict rock glaciers as indicators of Mediterranean palaeoclimate during the Last Glacial Maximum (Late Würmian) in northwest Greece     

P. D. Hughes  P. L. Gibbard  J. C. Woodward 《第四纪科学杂志》2003,18(5):431-440

  相似文献   

鲁北平原黄河古河道初步研究   总被引：10，自引：0，他引：10  

张祖陆 《地理学报》1990,45(4):457-466

鲁北平原黄河古河道可分为地面古河道(埋藏深度0—8m)和浅埋古河道(埋藏深度8—40m)。两类古河道部大致可分为三条古河道带,呈SW-NE向近平行展布,每带一般宽5—15km,最宽处可达20km。 古河道沉积层主要由细砂或粉砂组成,为古河床之曲流砂堤或天然堤沉积。各期古河道沉积层之顶、底板主要为粘土或亚粘土和淤泥层所构成,为古黄河泛滥相沉积物。 本区古河道按形成时间顺序可分为三期,下部第一期古河道大约形成于晚更新世晚期—全新世早期,中部第二期古河道形成于全新世早—中期,上部第三期古河道形成于全新世中—晚期。  相似文献   

Chronology of the last recession of the Greenland Ice Sheet   总被引：1，自引：0，他引：1  

Ole Bennike  Svante Bjrck 《第四纪科学杂志》2002,17(3):211-219

A new deglaciation chronology for the ice‐free parts of Greenland, the continental shelf and eastern Ellesmere Island (Canada) is proposed. The chronology is based on a new compilation of all published radiocarbon dates from Greenland, and includes crucial new material from southern, northeastern and northwestern Greenland. Although each date provides only a minimum age for the local deglaciation, some of the dates come from species that indicate ice‐proximal glaciomarine conditions, and thus may be connected with the actual ice recession. In addition to shell dates, dates from marine algae, lake sediments, peat, terrestrial plants and driftwood also are included. Only offshore and in the far south have secure late‐glacial sediments been found. Other previous reports of late‐glacial sediments (older than 11.5 cal. kyr BP) from onshore parts of Greenland need to be confirmed. Most of the present ice‐free parts of Greenland and Nares Strait between Greenland and Ellesmere Island were not deglaciated until the early Holocene. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

末次冰消期以来渤、黄、东海陆架潮汐、潮流演变过程模拟研究   总被引：1，自引：0，他引：1  

朱玉荣 《中国海洋大学学报(自然科学版)》2002,32(2):279-286

末次盛冰期结束、海侵开始后渤、黄、东海陆架潮汐、潮流的演变对该区泥沙的输运与沉积 ,以及海底地貌的形成、分布以及演变等具有深刻影响。文中数值模拟末次冰消期以来 4个特定时期 ,即比现在海面低 80 m、5 2 m、30 m海面以及全新世最大海侵时渤、黄、东海陆架的潮汐、潮流。根据不同时期的潮汐、潮流分布特征得出 ,末次冰消期以来渤、黄、东海陆架潮汐、潮流的演变过程大致以全新世最大海侵为界划分为两个阶段 :1全新世最大海侵前为渤、黄、东海陆架潮汐、潮流基本分布格局的形成阶段 ;2全新世最大海侵后 ,为基本分布格局的局部调整阶段。末次冰消期以来基本海岸轮廓的变迁是渤、黄、东海陆架区潮汐、潮流演变的主要控制因素  相似文献   

末次盛冰期以来长江南通段古河谷的地层特征     

曹光杰  王建  屈贵贤 《地层学杂志》2007,31(2):175-178

通过对南通段古河谷典型钻孔及剖面沉积物颗粒、微体生物化石、14C测年等的分析,对末次盛冰期以来的沉积地层进行了划分。该段古河谷末次冰期以来的地层,基本上反映了河床相—河漫滩相—浅海相—三角洲相的冰后期海侵沉积旋回。现代河床的底部,浅海相淤泥质亚黏土层已被侵蚀掉,沉积的是现代河床相砂层。  相似文献