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1.
The reconstruction of air trapped in ice cores provides us the most direct information about atmospheric CH4 variations in the past history. Ice core records from the ＂Three Poles （Antarctica, Greenland and Tibetan Plateau）＂ reveal the detailed fluctuations of atmospheric CH4 concentration with time and are allowed to quantify the CH4 differences among latitudes. These data are indispensably in the farther study of the relationship between greenhouse gases and climatic change, and of the past changes in terrestrial CH4 emissions. Ice cores reconstruction indicates that atmospheric CH4 concentration has increased quickly since industrialization, and the present day＇s level of atmospheric CH4 （1800 ppby） is unprecedented during the past Glacial-Interglacial climate cycles.  相似文献   

2.
A high-resolution 2000-year methane record has been constructed from an ice core recovered at 7200 m a.s.l. on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend in the concentration of methane during the industrial era that is similar to observations from polar regions. However, we also observed the differences in the atmospheric methane mixing ratio between this monsoon record and those from polar regions during pre-industrial times. In the time interval 0-1850 A.D., the average methane concentration in the Dasuopu ice core was 782±40 ppbv and the maximum temporal variation exceeded 200 ppbv. The difference gradient of methane concentration in Dasuopu ice core with Greenland and Antarctica cores are 66±40 ppbv and 107±40 ppbv, respectively. This suggests that the tropical latitudes might have acted as a major global methane source in pre- industrial times. In addition, the temporal fluctuation of the pre-industrial methane records suggests that monsoon evolution incorporated with high methane emission from south Asia might be responsible for the relatively high methane concentration observed in the Dasuopu ice core around A.D. 800 and A.D. 1600. These results provide a rough understanding of the contribution of tropical methane source to the global methane budget and also the relationship between atmospheric methane and climate change.  相似文献   

3.
Because of the limitations of sampling and seasonal study in polar regions, knowledge of dinoflagellate diversity, distribution and ecology are limited. Dinoflagellates have been incidentally reported from polar regions during some seasons and some populations have been reported as components of microalgae. Surveys of molecular diversity link the genotype of dinoflagellates from polar regions with environmental adaptation. In this study, 37 positive clones of dinoflagellates collected from different sites were used for genotype analysis, providing new insights into the biodiversity and distribution of these species based on 18S rRNA sequencing. Diverse genotypes were recorded for the summer season in Kongsfjorden (high Arctic) whilst a single novel genotype of dinoflagellate was recorded from winter samples from the Antarctic Ocean. Data from ice cores suggests that this single dinoflagellate genotype was adapted to extreme cold and clone library screening found that it was occasionally the only microbial eukaryotic genotype found in winter ice cores. The findings of this study could improve our understanding of the diverse dinoflagellate genotypes occurring in these perennially cold microbial ecosystems.  相似文献   

4.
以青藏高原西南部塔若错的34cm浅湖芯为研究对象,对其沉积物样品进行总有机碳、无机碳、总氮、微量元素、正构烷烃含量及碳氮比等多项指标的分析测定。采用过剩210 Pb和137 Cs计年法对该湖芯进行了定年和沉积速率研究,获得了近300年的连续湖泊沉积环境序列。在明确了各指标气候环境指示意义的前提下,综合对比分析湖芯中各项气候环境指标,并结合定年结果重建了塔若错湖区近300年来的气候环境变化。结果表明:塔若错湖区气候环境变化可分为3个明显阶段:早期为1705～1778年,该地区气候环境温暖湿润,湖区植被广泛发育;中期为1778～1860年,湖区处于小冰期末次阶段,气候环境寒冷而湿润,植被发育受阻;后期为1860年至今,为小冰期结束后偏暖干化时期。其中,后期又可分为3个亚阶段:1860～1924年,湖区气候环境稍暖且干旱,植被稍有发育;1924～1969年,湖区气候环境呈现偏冷干特点,植被发育暂缓;1969年至今,湖区气候回暖,环境干旱化有所缓解,植被开始逐渐发育。在气候冷暖变化上,该湖芯记录与古里雅冰芯记录和青海湖湖泊沉积记录都有较好的可对比性,只是在起讫年代上存在一些差异。  相似文献   

5.
Ice cores contain an abundance of information about the Earth''s climate in the past,and recovered from shallow drilling down to 300--350 m give sufficient information for reconstructing of the last climatic chan- ges and for monitoring of pollution from human being． Cable-suspended core auger drills use an armored cable with a winch to provide power to the down-hole motor system and to retrieve the down-hole unit． Because of their lightweight,convenient transportation and installation,high penetration rates and low power consumption, core auger drills are widely used for shallow drilling in ice． Nowadays at least 14 types of auger electromechani- cal drills were designed and tested in different foreign and national glaciological laboratories． However,auger options were usually determined by experience,and the main parameters (helix angle of the fights and rotational speed) are varied in a wide range from drill to drill． If parameters of auger are not chosen properly,poorly en- gineered drills had troubles with low efficiency of cuttings transportation,jam of ice cuttings,repeated fragmen- tation,cutters icing and stop penetration,abnormal power consumption,high rotation torques,and so on． Thus,this paper presents the method of optimization of ice cuttings transportation of cable-suspended core auger drill on the base of the theory of rotary auger． As the result,the optimal helix angle was determined correspond- ing to the rotational speed from the transportation efficiency point of view．  相似文献   

6.
During August 1999, we investigated sea ice characteristics; its distribution, surface feature, thickness, ice floe movement, and the temperature field around inter-borders of air/ice/seawater in the Chukchi Sea. Thirteen ice cores were drilled at 11 floe stations in the area of 72°24′ 77°18′N, 153°34′ 163°28′W and the ice core structure was observed. From field observation, three melting processes of ice were observed; surface layer melting, surface and bottom layers melting, and all of ice melting. The observation of temperature fields around sea ice floes showed that the bottom melting under the ice floes were important process. As ice floes and open water areas were alternately distributed in summer Arctic Ocean; the water under ice was colder than the open water by 0.4 2.8℃. The sun radiation heated seawater in open sea areas so that the warmer water went to the bottom when the ice floes move to those areas. This causes ice melting to start at the bottom of the ice floes. This process can balance effectively the temperature fluctuating in the sea in summer. From the crystalline structure of sea ice observed from the cores, it was concluded that the ice was composed of ice crystals and brine-ice films. During the sea ice melting, the brine-ice films between ice crystals melted firstly; then the ice crystals were encircled by brine films; the sea ice became the mixture of ice and liquid brine. At the end of melting, the ice crystals would be separated each other, the bond between ice crystals weakens and this leads to the collapse of the ice sheet.  相似文献   

7.
ChineselOeSSischaracterizedbythegreatthicknessandgabscontinuity.ItrererdsQuaternalyclimaticoscillations(Liu,1985).Inrecentyears,scientistshavetriedtOusephysicalorchemicalparameterstOrecostructthepastclimaticchanges.FOrinstance,theparticlesizeisUSedasproxyindicatorforthewintermo~intensity(Liu,1993),stableoxygenisotopicrecordofCarbenatenodulesisusedtoreflectthetemperaturevallationsOfsoilformation(Han,1995),andrnsgneticsuSCeptibilityandCarhanatecontentareughasproxyparametersforsuxnmermourn…  相似文献   

8.
走向海外是解决我国能源安全问题的必由之路。但海外油气藏评价往往缺乏第一手岩心资料, 使得储层孔隙结构和渗流规律认识不清, 影响评价效果。以海外J油田孔隙型碳酸盐岩油藏为例, 应用数字岩心技术开展油气藏孔渗特征研究。①以不同流动单元的铸体薄片图像作为输入数据, 经过中值滤波和阈值分割预处理后, 基于马尔科夫链蒙特卡洛数值重构算法构建数字岩心; ②分析孔喉分布、孔喉连通性、孔隙度特征; ③基于格子玻尔兹曼模拟方法开展单相和油水两相流动模拟, 计算数字岩心的绝对渗透率和相对渗透率曲线。结果表明, 构建的三维数字岩心能够刻画不同流动单元孔隙型碳酸盐岩的孔喉半径分布及孔喉连通程度的差异化特征。数字岩心孔隙度与铸体薄片孔隙度吻合度高, 数字岩心渗透率与真实岩心渗透率存在较好的正相关关系, 且符合真实岩心所属的流动单元。油水两相稳态流动模拟计算的相对渗透率曲线体现了不同流动单元的两相渗流能力差异, 可作为数值模拟输入条件, 以及估算油藏采收率。数字岩心分析与物理实验结果吻合良好, 证明了该方法的可靠性。为岩心资料稀缺条件下油气藏表征和渗流特征分析提供新的思路, 对油气藏精细描述具有重要的参考价值。   相似文献   

9.
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10.
利用Bedmap2数据与中国第29次南极科学考察期间获取的冰雷达数据,在中山站至Dome A断面的Gamburtsev山脉地区首次构建11.3 km×11.5 km南极局部冰盖三维模型。着重介绍三维模型建立过程中的数据处理,其中冰雷达数据采集首次采用中国自主研发的冰雷达系统。详细阐述了冰雷达数据的处理流程,包括数据预处理、常规图像修正技术以及冰下地形获取,得到冰下基岩埋深和冰盖内部等时层埋深,插值得到100 m分辨率的冰下基岩DEM（海拔1 729 m~2 718 m）和等时层DEM（海拔2 601 m~2 950 m）,利用南极Bedmap2冰表面栅格影像得到100 m分辨率的冰盖表面DEM（海拔3 679 m~3 745 m）。结合冰盖内外部数据处理结果,构建包含冰盖表面、冰盖内部等时层和冰下基岩地形特征的三维模型,并对模型进行检验,对冰盖内外部地形特征进行初步分析。  相似文献   

11.
To predict future spatio-temporal patterns of climate change, we should fully understand the spatio-temporal patterns of climate change during the past millennium. But, we are not yet able to delineate the patterns because the qualities of the retrieved proxy records and the spatial coverage of those records are not adequate. Northern Xinjiang of China is one of such areas where the records are not adequate. Here, we present a 500-yr land-surface moisture sequence from Heiyangpo Peat (48.34°N, 87.18°E, 1353 m a.s.l) in the southern Altai Mountains within northern Xinjiang. Specifically, peat carbon isotope value of cellulose (δ13Ccellulose) was used to estimate the warm-season moisture variations and the degree of humification was used to constrain the δ13Ccellulose-based hydrological interpretation. The climatic attributions of the interpreted hydrological variations were based on the warm-season temperature reconstructed from Belukha ice core and the warm-season precipitation inferred from the reconstructed Atlantic Multidecadal Oscillations (AMO). The results show that humification decreased and the δ13Ccellulose-suggested moisture decreased from ~1510 to ~1775 AD, implying that a constant drying condition may have inhibited peat decay. Our comparison with reconstructed climatic parameters suggests that the moisture-level decline was most likely resulted from a constant decline of precipitation. The results also show that humification kept a stable level and the δ13Ccellulose-suggested moisture also decreased from ~1775 to ~2013 AD, implying that peat decay in the acrotelm primarily did not depend on the water availability or an aerobic environment. Again, our comparison with reconstructed climatic parameters suggests that the land-surface moisturelevel decline was most likely resulted from a steady warming of growing-season temperature.  相似文献   

12.
Based on investigations of the Zhongwei Nanshan aeolian section situated in the southeastern margin of Tengger Dcsert, carbon-14 and TL (thermoluminescence) dating results and paleoclimatic proxies such as magnetic susceptibility and grain size, we inferred that the northwestern margin of East Asian monsoon region experienced abrupt climatic changes during the last deglaciation. Six oscillation events were identified: Oldest Dryas, Belling, Older Dryas, AllerФd, lntra-AllerФd Cold Period (1ACP) and Younger Dryas (YD). The summer monsoon was weaker during Oldest Dryas and Younger Dryas when the winter monsoon was stronger. However, during the B/A (BФlling/AllerФd) period, the summer monsoon strengthened, reflected by magnetic susceptibility, when the winter monsoon also became strong, which is different from the paleoclimatic pattern established in the East Asian monsoon region. Furthermore,the summer monsoon was nearly in phase with the climate changes inferred from the oxygen isotopic records of Greenland ice cores. It could be speculated that the variations of the sea ice cover in the high latitudes of the North Hemisphere affected the high pressure of Asian continent and the changes of the winter monsoon inland. On the other hand,the sea ice cover variations might have indirectly caused the occurrence of ENSO events that has tightly been related to the summer monsoon in northwest margin of East Asian monsoon region.  相似文献   

13.
DRY-WET EVOLUTION IN GUANGDONG PROVINCE DURING LAST 500 YEARS   总被引：1，自引：0，他引：1  
1 INTRODUCTIONThe global warming change has already become one ofthe focuses that many scientists pay attention to, and theprecipitation change of China is also one part of thequestionsunder the whole world changes today. Accord-ing to the actual material analysis, the climate in Chinahad a warm-dry tendency in a wide spread range duringthe past one hundred years (ZHAO, 1993), and it couldnot draw a verdict as for future tendency at present. Fol-lowing the thought of Prof. HUANG Bing…  相似文献   

14.
Using the NCEP/NCAR reanalysis monthly 500 hPa height data on a 2.5 latitude-longitude grid and 1°×1° sea ice data,the polar vortex area,intensity index and arctic sea ice area index are calculated respectively,and the meridional distribution,period variation and the abrupts in the long range trend are analyzed to study their relationship.The results show that the meridional distribution of sea ice and polar vortex h-ave distinctive difference,the relative positions of them are different in the eastern and western hemispheres,and exept they have periods of 4 months,quasi half year,quasi year,4-5 years and 10 years commonly,and each of them has its own respective variation as well.The sea ice area is decreasing apparently since 1980's,so is the polar vortex area,but their abrupt changge time are different totally.The area of sea ice and polar vortex has prominent positive correlation,but the relationship of sea ice intensity,polar vortex intensity,polar vortex area is complicated.  相似文献   

15.
The Yellow Sea (YS) environmental and ecological changes during the Holocene are driven by the interactions between the Yellow Sea Warm Current (YSWC), the East Asian Winter Monsoon (EAWM) and the Kuroshio Current (KC). We report marine biomarker records of brassicasterol, dinosterol and C37 alkenones in core ZY1 and core ZY2 from the South Yellow Sea (SYS) to reconstruct the spatial/temporal variations and possible mechanisms of phytoplankton primary productivity and community structure changes during the Mid-late Holocene. The contents of the corresponding biomarkers in the two cores are similar, and they also reveal broadly similar temporal trends. From 6 kyr to 3 kyr, the biomarker contents in the two cores were relatively low with small oscillations, followed by a distinct increase at about 3 kyr indicating productivity increases caused by a stronger EAWM. The alkenone/brassicasterol ratio (A/B) is used as a community structure proxy, which also showed higher values in both cores since 3 kyr, indicating increased haptophyte contribution to total productivity. It is proposed that the YS community structure has been mainly influenced by the YSWC, with stronger YSWC influences causing an increase in haptophyte contribution since 3 kyr. Some differences of the biomarker records between ZY2 and ZY1 suggest spatial variations in response to YSWC and KC forcing. When the KC was intensified during the periods of 6–4.2 kyr and 1.7–0 kyr, the YSWC extended eastward, exerting more influence on core ZY1. On the other hand, when the KC weakened during 4.2–1.7 kyr, the YSWC extended westward, exerting more influence on the ZY2.  相似文献   

16.
CLIMATIC VARIATIONS IN CHINA OVER THE LAST 2000 YEARS   总被引：4，自引：0，他引：4  
1 INTRODUCTIONIn the last years, evidence for climate changes showed that the timing of the two great climatic events of “Medieval Warm Period” (MWP) and “Little Ice Age” (LIA) differed geographically (HUGHES et al., 1994, JONES and BRADLEY, 1992). In other words, the cold or warm periods in one region were often not coincident with those in other regions. The Northern Hemisphere warmth degree in the Middle Ages was lower than or at most comparable to that in the mid-20…  相似文献   

17.
以2003年架设的NOAA／FY极轨卫星数据地面接收站为基础,针对NOAA系列卫星．采用分布式处理方案,设计并建立了地震热红外卫星监测业务运行系统。系统主要功能包括：卫星数据的接收、处理、归档、查询、发布;自动生成全国夜晚地表亮温图像、全国白天彩色合成图像、全国每旬无云地表亮温图像等专题数据库产品;对任意选定的监测区进行热红外亮温动态跟踪和异常警示;实现了直观的无人值守的准实时自动化处理以及远程管理和数据检索。通过对地震热红外卫星监测业务运行系统的研究和开发,在数据标定、辐射校正、图像预处理、专题产品的生成与管理等方面取得了宝贵的经验,为我国地震卫星地面数据接收、处理系统的建立奠定了基础。  相似文献   

18.
Mt. Yulong is the southernmost currently glacier-covered area in Eurasia, including China. There are 19 sub-tropical temperate glaciers on the mountain, controlled by the south-western monsoon climate. In the summer of 1999, a firn core, 10. 10 m long, extending down to glacier ice, was recovered in the accumulation area of the largest glacier, Baishui No. 1. Periodic variations of climatic signals above 7. 8 m depth were apparent, and net accumulation of four years was identified by the annual oscillations of isotopic and ionic composition. The boundaries of annual accumulation were confirmed by higher values of electrical conductivity and pH, and by dirty refreezing ice layers at the levels of summer surfaces. Calculated mean annual net accumulation from 1994/1995 to 1997/1998 was about 900 mm water equivalent. The amplitude of isotopic variations in the profile decreased with increasing depth, and isotopic homogenization occurred below 7. 8 m as a result of meltwater percolation. Variations of δ18O above 7. 8 m showed an approximate correlation with the winter climatic trend at Li Jiang Station, 25 km away. Concentrations of Ca2+ and Mg2+ were much higher than those of Na+ and K+ , indicating that the air masses for precipitation were mainly from a continental source, and that the core material accumulated during the winter period. The close correspondence of C1- and Na+ indicated their common origin. Very low concentrations of SO2-4 and NO3- suggest that pollution caused by human activities is quite low in the area. The mean annual net accumulation in the core and the estimated ablation indicate that the average annual precipitation above the glacier's equilibrium line is 2400 - 3150 mm, but this needs to be confirmed by long term observation of mass balance.  相似文献   

19.
Status of the Recent Declining of Arctic Sea Ice Studies   总被引：2，自引：0，他引：2  
In the past 30 years, a large-scale change occurred in the Arctic climatic system, which had never been observed before 1980s. At the same time, the Arctic sea ice experienced a special evolution with more and more rapidly dramatic declining. In this circumstance, the Arctic sea ice became a new focus of the Arctic research. The recent advancements about abrupt change of the Arctic sea ice are reviewed in this paper .The previous analyses have demonstrated the accelerated declining trend of Arctic sea ice extent in the past 30 years, based on in-situ and satellite-based observations of atmosphere, as well as the results of global and regional climate simulations. Especially in summer, the rate of decrease for the ice extents was above 10% per decade. In present paper, the evolution characteristics of the arctic sea ice and its possible cause are discussed in three aspects, i.e. the sea ice physical properties, the interaction process of sea ice, ocean and atmosphere and its response and feedback mechanism to global and arctic climate system.  相似文献   

20.
We performed a comparison analysis of the variations .in Mercury ( Hg) concentrations and the precipitation proxies ( e. g. , 18 O values and 10 Be concentrations) in the Dome C ice core. The results showed that there were significant correlations between Hg and δ 10O values, 10Be concentrations, indicating that the accumulation rate in Dome C is one of the key factors controlling the variations of Hg concentrations in the past 34 ,000 years, and implying that Hg concentrations in ice core can be used as another reliable proxy of precipitation rate in Antarctica. Based upon the high-resolution δ 18O values, we estimated the variations in mercury deposition flux to Antarctica over the past 34,000 years. The highest mercury deposition flux is about 3. 80 pg cm-2 yr-1 during the Last Glacial Maxium (LGM) as high as 3. 5 times of the mercury deposition flux ( about 1. 08 pg cm -2 yr -1) in Holocene due to the fluctuations in natural mercury emissions such as the oceanic biological emissions.  相似文献   

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