共查询到10条相似文献，搜索用时 312 毫秒
1.
基于乌鲁木齐河源1号冰川4 130 m处的雪冰化学资料,探究了气温和降水与冰芯记录形成过程及其分辨率的关系,并通过建立温度参数的淋溶模型,探讨了夏季消融期雪坑离子浓度与正积温的关系。结果表明：乌鲁木齐河源1号冰川Mg2+离子以1年为分辨率形成冰芯记录,其浓度仅保存了初始值的30%。春季,化学离子浓度峰值受到离子来源和降水的影响而增大,这种增大趋势随着深度的增加明显弱化。淋溶模式显示,雪坑离子浓度是关于消融量与离子损失率的指数函数,随正积温的增大表现出指数衰减的规律。该模式基本能反映不同离子的淋溶过程。 相似文献
2.
在冰芯研究中,氧同位素比率不仅是气温的一种代用指标,而且其变化又是冰芯年层划分的依据之一。本文着重阐述了青藏高原古里雅３０９ｍ冰芯中δ１８Ｏ记录研究的一些结果。对于该冰芯上部１２０ｍ,根据δ１８Ｏ等的季节变化特征可划分出２０００多个年层,这是该冰芯高分辨率气候环境记录恢复的基础。借助于放射性物质（３６ＣＩ）测年等手段,建立了该冰芯下部的时间标尺。据此恢复了０．１２５Ｍａ以来古里雅冰芯中１８Ｏ记录,将其与深海沉积中的氧同位素变化相比较,可划分出阶段 １,２,３,４和５,其中阶段５又可划分出 ５个业阶段,即ａ,ｂ,ｃ,ｄ和ｅ亚阶段。古里雅冰芯１８Ｏ记录的一个突出特征就是其升高和降低的幅度都很大,这反映了青藏高原对于气候变化的响应是极为敏感的。５ｅ时古里雅冰芯中δ１８Ｏ所记录的升温幅度达５℃,高于全球平均升温值２～３℃。 相似文献
3.
Quantitative analyses of planktic foraminifera, sea‐surface temperatures (SSTs), oxygen isotope and radiocarbon dating from a deep‐sea core recovered in the South Adriatic Sea have been used to reconstruct a subcentennial climatic and biochronological record since the late glacial (the last 24 cal. ka BP). The identification and relative abundance of 25 species of planktic foraminifera along the core have provided a continuous record of the faunal changes over this time interval. These results have permitted the establishment of 10 biozones in the South Adriatic Sea based on the appearance and/or disappearance of the main specific taxa, from peaks of abundance and/or by modification in marine conditions. The robust chronology of the South Adriatic core allowed correlation of SST estimates to the GISP2 ice core record, indicating that the main climate changes recorded in Greenland ice cores over the last 24 ka are recorded and globally synchronous with those observed in the South Adriatic Sea. This finding further allows comparison of the planktic foraminifera record with the event stratigraphic scheme proposed by the INTIMATE group in order to better identify the relationship between past climatic changes and the response of microfaunal assemblages in the South Adriatic. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
4.
Lindsay L. Vare Guillaume Massé Thomas R. Gregory Christopher W. Smart Simon T. Belt 《Quaternary Science Reviews》2009,28(13-14):1354-1366
A sea ice record for Barrow Strait in the Canadian Arctic Archipelago (CAA) is presented for the interval 10.0–0.4 cal. kyr BP. This Holocene record is based primarily on the occurrence of a sea ice biomarker chemical, IP25, isolated from a marine sediment core obtained from Barrow Strait in 2005. A core chronology is based on 14C AMS dating of mollusc shells obtained from ten horizons within the core. The primary IP25 data are compared with complementary proxy data obtained from analysis of other organic biomarkers, stable isotope composition of bulk organic matter, benthic foraminifera, particle size distributions and ratios of inorganic elements. The combined proxy data show that the palaeo-sea ice record can be grouped according to four intervals, and these can be contextualised further with respect to the Holocene Thermal Maximum (HTM). Spring sea ice occurrence was lowest during the early–mid Holocene (10.0–6.0 cal. kyr BP) and this was followed by a second phase (6.0–4.0 cal. kyr BP) where spring sea ice occurrence showed a small increase. Between 4.0 and 3.0 cal. kyr BP, spring sea ice occurrence increased abruptly to above the median and we associate this interval with the termination of the HTM. Elevated spring sea ice occurrences continued from 3.0 to 0.4 cal. kyr BP, although they were more variable on shorter timescales. Within this fourth interval, we also provide evidence for slightly lower and subsequently higher spring sea ice occurrence during the Mediaeval Warm Period and the Little Ice Age respectively. Comparisons are made between our proxy data with those obtained from other palaeo-climate and sea ice studies for the CAA. 相似文献
5.
Anette K. Mortensen Matthias Bigler Karl Grnvold Jrgen P. Steffensen Sigfús J. Johnsen 《第四纪科学杂志》2005,20(3):209-219
The tephrochronological record of the 1400–1640 m depth (～10 000–16 000 calendar ice core years before present) of the NGRIP ice core has been established by particle screening of selected samples. Ash was identified in 20 samples. Correlation with ice, marine and terrestrial records from volcanic source regions in the northern hemisphere positively identifies the Saksunarvatn Ash and the Vedde Ash (Ash Zone 1). Major element chemistry of the remaining identified ash layers mainly points towards an Icelandic origin. This tephrochronological record provides new important marker horizons for correlating the timing of the climatic changes associated with the Last Glacial Termination within the North Atlantic region, as well as outlining more details concerning the frequency and composition of volcanic eruptions occurring at this deglaciation. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
6.
《Earth》2003,60(1-2):131-146
This review paper is mainly concerned with a geochemical investigation of the deepest part of the Vostok ice core between 3310 m, the depth at which the palaeoenvironmental record present in the ice above is lost, and the bottom of the core about 130 m above subglacial Lake Vostok. Two sections constitute this part of the core.The upper section (3310–3539 m depth) still consists of ice of meteoric origin but subjected to widespread complex deformation. This deformation is analysed in light of a δD–deuterium excess diagram and information on microparticles, crystal sizes and chemical elements distributions in that part of the core. Such ice deformation occurred when the ice was still grounded upstream from Vostok station in a region with subfreezing temperatures.The lower section from 3539 m to the bottom of the core at 3623 m depth is lake ice formed by freezing of subglacial Lake Vostok waters. This is indicated by the isotopic properties (δD, δ18O and deuterium excess), by electrical conductivity measurements (ECM), crystallography and gas content of the ice. These ice core data together with data on ionic chemistry favour an origin of the lake ice by frazil ice generation in a supercooled (below pressure melting point) water plume existing in the lake followed by accretion and consolidation by subsequent freezing of the host water.The helium profile of this deepest part of the Vostok core is quite unusual and surprising. It has important implications for the interactions between the ice sheet and the lake. Two constrasting scenarios can be satisfactorily constructed so that the lake residence time is not well constrained. 相似文献
7.
神农架天鹅洞石笋76～58 kaB.P.时段DO事件 总被引：1，自引：1，他引：0
据神农架高海拔天鹅洞一支石笋9个230Th年龄和332组氧、碳同位素数据,建立了76～58 kaB.P. Dansgaard Oeschger (DO)事件时间序列,揭示了深海氧同位素4阶段(MIS4)东亚季风降水百年尺度变化过程。天鹅洞和葫芦洞石笋、格陵兰NGRIP冰芯δ18O对比显示,天鹅洞记录DO18事件暖湿程度相当于深海氧同位素3阶段(MIS3)水平,其振幅类似于格陵兰冰芯δ18O记录。起始时间上,天鹅洞记录DO18事件在710年230Th测年误差范围内和葫芦洞记录保持一致,并支持了NGRIP冰芯记录对应时标。在全球降温背景下,如此典型DO事件指示了强季风降水过程。70 kaB.P.左右,冰芯DO19事件至少老于石笋记录约950年,远大于700年左右的230Th测年误差,对老于该时段的冰芯时标需高分辨率地质记录进一步验证。69.09～64.64 kaB.P.（ DO19ˊ~18）期间,冰芯记录的百年尺度峰谷变化和天鹅洞石笋记录一一对应,反映了低纬热带海洋和北大西洋温盐环流之间耦合作用。 相似文献
8.
Jianzhong Xu Dahe Qin Paul Andrew Mayewski Barbara Delmonte Jiawen Ren Sungmin Hong 《Quaternary Research》2010,73(1):33-38
The central Himalaya can be regarded as an ideal site for developing a long-term ice core dust record to reflect the environmental signals from regional to semi-hemispheric scales. Here we present a dust record from segments of a 108.83-m ice core recovered from the East Rongbuk (ER) Glacier (27°59′N, 86°55′E; 6518 m a.s.l.) on the northeast slope of Mt. Qomolangma (Everest) in the central Himalaya, covering the period AD 600-1960. Due to rapidly layer thinning and coarse sampling, we primarily discuss the changes in the dust record since AD 1500 in this paper. Results show a significant positive relationship between the dust concentration and reconstructed air temperatures during this period, suggesting a likely cold-humid and warm-dry climatic pattern in the dust source regions, namely Central Asia. This is associated with the variability in the strength of the westerlies and its corresponding precipitation. 相似文献
9.
Anders Svensson Katrine K. Andersen Matthias Bigler Henrik B. Clausen Dorthe Dahl-Jensen Siwan M. Davies Sigfus J. Johnsen Raimund Muscheler Sune O. Rasmussen Regine Rthlisberger Jrgen Peder Steffensen Bo.M. Vinther 《Quaternary Science Reviews》2006,25(23-24):3258
A new Greenland Ice Core Chronology (GICC05) based on multi-parameter counting of annual layers has been obtained for the last 42 ka. Here we compare the glacial part of the new time scale, which is based entirely on records from the NorthGRIP ice core, to existing time scales and reference horizons covering the same period. These include the GRIP and NorthGRIP modelled time scales, the Meese-Sowers GISP2 counted time scale, the Shackleton–Fairbanks GRIP time scale (SFCP04) based on 14C calibration of a marine core, the Hulu Cave record, three volcanic reference horizons, and the Laschamp geomagnetic excursion event occurring around Greenland Interstadial 10. GICC05 is generally in good long-term agreement with the existing Greenland ice core chronologies and with the Hulu Cave record, but on shorter time scales there are significant discrepancies. Around the Last Glacial Maximum there is a more than 1 ka age difference between GICC05 and SFCP04 and a more than 0.5 ka discrepancy in the same direction between GICC05 and the age of a recently identified tephra layer in the NorthGRIP ice core. Both SFCP04 and the tephra age are based on 14C-dated marine cores and fixed marine reservoir ages. For the Laschamp event, GICC05 agrees with a recent independent dating within the uncertainties. 相似文献