LATE‐GLACIAL GLACIER EVENTS IN SOUTHERNMOST SOUTH AMERICA: A BLEND OF ‘NORTHERN’ AND 'SOUTHERN’ HEMISPHERIC CLIMATIC SIGNALS?   总被引：2，自引：0，他引：2  

D.E. SUGDEN  M.J. BENTLEY  C.J. FOGWILL  N.R.J. HULTON  R.D. McCULLOCH  R.S. PURVES 《Geografiska Annaler: Series A, Physical Geography》2005,87(2):273-288

ABSTRACT. This paper examines new geomorphological, chronological and modelling data on glacier fluctuations in southernmost South America in latitudes 46–55°S during the last glacial–interglacial transition. Establishing leads and lags between the northern and southern hemispheres and between southern mid‐latitudes and Antarctica is key to an appreciation of the mechanisms and resilience of global climate. This is particularly important in the southern hemisphere where there is a paucity of empirical data. The overall structure of the last glacial cycle in Patagonia has a northern hemisphere signal. Glaciers reached or approached their Last Glacial Maxima on two or more occasions at 25–23 ka (calendar) and there was a third less extensive advance at 17.5 ka. Deglaciation occurred in two steps at 17.5 ka and at 11.4 ka. This structure is the same as that recognized in the northern hemisphere and taking place in spite of glacier advances occurring at a time of high southern hemisphere summer insolation and deglaciation at a time of decreasing summer insolation. The implication is that at orbital time scales the‘northern’ signal dominates any southern hemisphere signal. During deglaciation, at a millennial scale, the glacier fluctuations mirror an antiphase 'southern’ climatic signal as revealed in Antarctic ice cores. There is a glacier advance coincident with the Antarctic Cold Reversal at 15.3–12.2 ka. Furthermore, deglaciation begins in the middle of the Younger Dryas. The implication is that, during the last glacial–interglacial transition, southernmost South America was under the influence of sea surface temperatures, sea ice and southern westerlies responding to conditions in the 'southern’ Antarctic domain. Such asynchrony may reflect a situation whereby, during deglaciation, the world is more sensitized to fluctuations in the oceanic thermohaline circulation, perhaps related to the bipolar seesaw, than at orbital timescales.  相似文献   

Land-sea correlations for the last glaciation inferred from a pollen and dinocyst record from the portuguese margin     

Jean-Louis Turon  Anne-Marie LézineMichelle Denèfle 《Quaternary Research》2003,59(1):88-96

Pollen and dinoflagellate cyst assemblages from Core SU 81-18 recovered off Portugal (37°46′N, 10°11′W; 3135-m water depth) have been used to document the short-term environmental changes that occurred in southwest Europe since 25,000 yr B.P. The relationship between the oceanic and continental environments has been further examined by the use of other marine proxies (coarse sedimentary fraction, foraminifera) and by comparison with proximal land pollen records. Heinrich 2 (H2) and Heinrich 1 (H1) events were the most extreme parts of the highly variable last glacial period, with the maximum extension of dry steppe on land and the occurrence of cool and dilute waters at the core site. Our study shows that H1 and H2 are divided in two distinct phases: one with Neogloboquadrina pachyderma left coiling associated with the maximum input of ice rafted debris, reflecting the in situ release of icebergs and the occurrence of cool and dilute seawater at the core site; the other with dinoflagellate cysts of subpolar affinity, Bitectatodinium tepikiense, reflecting a seasonal control marked by warm summer SST and cold winter SST.  相似文献   

从会宁末次间冰期土壤看北大西洋气候不稳定性   总被引：2，自引：0，他引：2       下载免费PDF全文

任剑璋  丁仲礼 《地球物理学报》1998,41(2):162-167

会宁李家塬与新庄塬高分辨率黄土剖面的粒度分析表明,末次间冰期氧同位素阶段5e时期,黄土高原地区处于较为稳定的气候环境．该结果与格陵兰冰芯GRIP记录的气候变化过程不同  相似文献   

三江平原沼泽生态系统中露水凝结研究   总被引：8，自引：0，他引：8  

阎百兴  王毅勇  徐治国  董树斌 《湿地科学》2004,2(2):94-99

通过对三江平原露日季节变化的分析及对毛果苔草沼泽群落中露水的实地观测，探讨了年露日的出现规律及露水凝结量的时空变化。结果表明：三江平原露水出现频率较高的季节是夏秋季(6～9月)，近12年来露日在66～108d／a，平均为95．42d／a；每年露水的凝结存在两个明显的峰值，分别是6月(或7月)、9月；露水量随高度的变化明显，植物冠层高度处的露水凝结量较多；由于沼泽植物茂密，叶面积较大，加之地面粗糙，单位土地面积上在植物及地面实际凝结的露水量远高于相同面积下较光滑的收集器测得的露水量。用杨木棒测得的毛果苔草地表面的露水量为2．83mm／a，折算成单位土地面积上地表面和植物叶片实际凝结的露水量为20．68mm／a，占同期降水量的5．05％。露水是影响水量平衡的重要因子。  相似文献   

广州市雷暴日异常的基本气候特征及其与近海海温关系初探   总被引：8，自引：6，他引：8  

陈绍东  林奕峰  区永平 《热带气象学报》2004,20(1):106-112

分析了广州市雷暴日变化的基本气候特征。结果表明:广州市雷暴日主要集中在5～8月,占全年雷暴日总量的71.38%,雷暴日的季节分布具有双峰型的特征。近48年以来广州市雷暴日呈明显的下降趋势。广州市5～8月的雷暴日与同期850hPa大气环流的关系:多雷暴年整个亚洲中纬地区(35N)有明显的偏西风距平,南海及广东以及向北延伸的广大地区的西南及偏南气流盛行,少雷暴年则刚好相反。与近海海温做了简单的相关分析,得出:广州市雷暴日与前期4～6月印尼附近西太平洋海温呈负相关的变化趋势。  相似文献   

多种再分析地面气温资料在江西省的适用性     

李翔翔  黄淑娥  杨军  秦晓晨 《气象科技》2020,48(6):877-886

为评估不同再分析地面气温资料的适用性和模拟精度，采用双线性内插法将JRA55、ERA Interim、ERA5和MERRA2等再分析地面气温资料降尺度至气象观测站，评估其对实测气温的平均态（平均偏差、均方根误差、相关性分析）、趋势态（年际趋势）和极端态（高温日数、低温日数）的再现能力。通过在江西省的对比分析，结果表明：①利用邻近格点气温和高度值计算的逐时气温垂直递减率具有合理的波动范围以及季节性周期，适用于复杂地形下逐时再分析资料的内插订正；②订正后JRA55地面气温资料的均方根误差最小，MERRA2其次，ERA Interim和ERA5最大；③从气温年际变化趋势来看，JRA55、ERA Interim和ERA5增温速率与实测值较为一致，且JRA55对增温中心的刻画更优；④4种再分析资料均能再现高、低温日数的年际波动，但JRA55在量级上描述最优。综上，再分析地面气温资料的适用性JRA55＞ERA Interim＞ERA5＞MERRA2，JRA55再分析资料能较好地再现气温实际观测资料。  相似文献   

江西省2000年秋季异常连阴雨天气过程分析   总被引：1，自引：1，他引：1  

尹洁  刘献耀 《气象与减灾研究》2001,24(3):14-17

分析了江西省 2000年 10月 12～ 28日秋季连阴雨天气过程期间的 500 hPa和地面形势特征及 700 hPa湿度场特征，发现西风带低槽活动频繁、副高位置适中稳定使得冷空气和南方暖湿气流持续交汇于江南中北部是造成这次连阴雨天气过程的主要原因。  相似文献   

河西走廊末次冰期砂楔的发现及其古气候意义   总被引：8，自引：6，他引：8  

王乃昂  王涛  史正涛  胡刚  高顺尉 《冰川冻土》2001,23(1):46-50

河西走廊砂楔主要形成在晚更新世冲洪积砾石层中，楔体内充填的风成砂^14C年龄证明其是末次冰期的产物，在末次冰期，洒西走廊年平均气温为－5－7度左右，较现在低13－15度，这一 估算数据与根据本区芒硝沉积层所推测的气温下降值是一致的，亦与最近有关北半球高，中纬度冰期降温幅度的研究相符合，当时，河西走廊西段年降水量可能达到100－200mm，比现在平均年降水量增加约100mm左右。  相似文献   

青藏高原西北部17000年以来的介形类及环境演变   总被引：32，自引：3，他引：32  

李元芳 Gasse  F 《地理学报》1994,49(1):46-54

通过班公错和松西错两钻孔以及红山湖地层剖面的介形类分析，讨论了昆仑山、喀喇昆仑山地区晚更新世晚期以来的主要气候事件和环境变迁。  相似文献   

The 27-Day Signal in Sunspot Number Series and the Solar Dynamo     

Jean-Louis Le Mouël  Mikhail G. Shnirman  Elena M. Blanter 《Solar physics》2007,246(2):295-307

We analyze the Wolf number daily series WN (1849 to present) as well as two other related series characterizing solar activity. Our analysis consists in computing the amplitude of a given Fourier component in a sliding time window and examining its long-term evolution. We start with the well-known 27.03- and 27.6-day periods and observe strong decadal variations of this amplitude as well as a sharp increase of the average value starting around 1905. We then consider a packet of 31 lines with periods from 25.743 to 28.453 days, which is shown to be a better representation of the synodic solar rotation. We first examine the temporal evolution of individual lines, then the energy of the packet. The energy of the packet increases sharply at the beginning of the 20th century, leading by more than two decades the well-known increase of the Wolf number. The nonaxisymmetry of sunspots increases before the total increase of activity and may be considered as a precursor. We discuss briefly and tentatively this observation in terms of solar dynamo theory.  相似文献