Glaciomarine sedimentation and bottom current activity on the north-western and northern continental margins of Svalbard during the late Quaternary

Palaeo-bottom current strength of the West Spitsbergen Current (WSC) and the influence of the Svalbard-Barents Sea Ice Sheet (SBIS) on the depositional environment along the northern Svalbard margins are poorly known. Two gravity cores from the southern Yermak Plateau and the upper slope north of Nordaustlandet, covering marine isotope stage (MIS) 1 to MIS 5, are investigated. Five lithofacies, based on grain size distribution, silt/clay ratio, content and mean of sortable silt (SS), are distinguished to characterise the contourite-dominated sedimentary environments. In addition, depositional environments are described using total organic carbon (TOC), total sulphur (TS) and calcium carbonate (CaCO₃) contents of sediments. Facies A, containing coarse SS, suggests strong bottom current activity and good bottom water ventilation conditions as inferred from low TOC content. This facies was deposited during the glacial periods MIS 4, MIS 2 and during the late Holocene. Facies B is dominated by fine SS indicating weak bottom current and poor ventilation (cf. high TOC content of 1.2–1.6%), and correlates with the MIS 4/3 and MIS 2/1 transition periods. With an equal amount of clay and sand, fine SS and high content of TOC, facies C indicates reduced bottom current strength for intervals with sediment supply from proximal sources such as icebergs, sea ice or meltwater discharge. This facies was deposited during the last glacial maximum. Facies D represents mass-flow deposits on the northern Svalbard margin attributed to the SBIS advance at or near the shelf edge. Facies E sediments indicating moderate bottom current strength were deposited during MIS 5 and MIS 3, and during parts of MIS 2. This first late Quaternary proxy record of the WSC flow and sedimentation history from the northern Svalbard margin suggests that the oceanographic conditions and ice sheet processes have exerted first-order control on sediment properties.     

Solar-, monsoon- and Kuroshio-influenced thermocline depth and sea surface salinity in the southern Okinawa Trough during the past 17,300 years

Factors influencing millennial-scale variability in the thermocline depth (vertical mixing) and sea surface salinity (SSS) of the southern Okinawa Trough (OT) during the past 17,300 years were investigated based on foraminifer oxygen isotope records of the surface dweller Globigerinoides ruber sensu stricto and the thermocline dweller Pulleniatina obliquiloculata in the AMS ¹⁴C dated OKT-3 core. The thermocline depth is influenced by surface thermal buoyancy (heat) flux, in turn controlled by the annual mean insolation at 30°N and the strength of the East Asian winter monsoon (EAWM). Strong insolation and weak EAWM tend to increase buoyancy gain (decrease buoyancy loss), corresponding to shallow thermocline depths, and vice versa. Regional SSS is influenced by the global ice volume, the Kuroshio Current (KC), and vertical mixing. A deep thermocline coincides with a high SSS because strong vertical mixing brings more, saltier subsurface KC water to the surface, and vice versa. Local SSS (excluding the global ice volume effect) became lower in the northern OT than in the southern OT after ~9.2 ka, implying that Changjiang diluted water had stronger influence in the northern sector. SSS show no major changes during the Bølling/Allerød and Younger Dryas events, probably because the KC disturbed the North Atlantic signals. This argues against earlier interpretations of sea surface temperature records of this core. Wavelet and spectral analyses of the Δδ¹⁸O_P-G (δ¹⁸O of P. obliquiloculata minus G. ruber s.s.) and δ¹⁸O_local records display 1,540-, 1,480-, 1,050-, 860-, 640-, and 630-year periods. These are consistent with published evidence of a pervasive periodicity of 1,500 years in global climate as well as EAWM and KC signatures, and a fundamental solar periodicity of 1,000 years and intermediary derived periodicity of 700 years.     

最近千年来山东半岛西部气候环境变化的石笋δ18O、δ13C记录(Ⅰ)

Ky1石笋采自山东半岛西部的开元洞,沿生长轴方向长度75 mm。在高精度U-230Th测年基础上,通过年纹层连续计数和平均沉积速率内插/外推相结合的定年方法,确定Ky1石笋生长于892-1894AD的1 000年间。在沿石笋生长轴采集的583个样品中,选择303个进行了δ18O、δ13C测试,平均分辨率约为3年。结果显示,最近1 000年来Ky1石笋的δ18O比值变化呈现明显阶段性,显示与小冰期(LIA)和中世纪暖期(MWP)对应的数百年尺度波动。根据δ18O记录,山东半岛在1482AD前后发生与MWP/LIA转换对应的气候突变,1 482 AD前相当于夏季风强烈、降水较多的中世纪暖期,1482AD后则为夏季风微弱、降水较少的小冰期,以1609AD夏季风最弱。Ky1石笋的δ13C比值变化,也由与MWP、LIA相当的两个阶段构成,其间也存在突变关系。比较而言,δ13C变化要比δ18O显著平缓,而且LIA后期以来二者变化明显不同步。最近1 000年来,与MWP/LIA对应的气候突变相当于明朝中期;就各个朝代内部的气候变化趋势而言,不同朝代之间不尽相同;不同朝代之间的更替期均大致与MWP、LIA内部的次级气候突变时期对应。因此,中世纪暖期和小冰期内部的次级气候波动对中国社会发展的影响,可能比千年尺度上最剧烈的MWP/LIA突变本身更显著。另一方面,洞穴所在山地的土地利用程度不断提高,其与气候变化共同影响着洞穴所在山地的植被的C3/C4植物构成及土壤性质,从而影响到石笋δ13C比值。从892-1318AD,土地利用对山地植被构成、土壤特征的影响程度尚不及气候变化;1318-1479AD,已达到或超过小幅度的气候变化;1483-1779AD,达到或超过大幅度的气候变化;1779-1894AD,土地利用程度趋于稳定,气候变化对环境的影响程度则又相对凸显。     

近几十年来西北江三角洲网河区顶点的河相关系

据西北江三角洲网河区顶点马口、三水两水文站1959－1988年的实测大断面、流量、流速和水位资料，采用Leopold的水力几何形态关系建立断面河相关系，探讨两水文观测断面的河相关系特征、年际变化及河相关系的差异。河相关系表明，西北江三角洲的断面水力几何形态指数β1值相对较小，而β3值相对较大，代表了珠江特有的丰水少沙河流的河相关系。     

<Emphasis Type="Italic">Phragmites australis</Emphasis> (Common Reed) Invasion in the Rhode River Subestuary of the Chesapeake Bay: Disentangling the Effects of Foliar Nutrients,Genetic Diversity,Patch Size,and Seed Viability

The invasion and expansion of the introduced haplotype of Phragmites australis across North America is of growing concern. Previous studies in the Chesapeake Bay region found that Phragmites was more abundant, had higher foliar nitrogen, and produced more viable seeds in brackish wetland subestuaries with more anthropogenic development of the watershed. Here, we focus on a different scale and address issues related to the invasion of Phragmites within a single subestuary, the Rhode River. We evaluated patterns in seed viability, foliar nutrient concentrations, patch size, and genetic variation in ten Phragmites patches in wetlands that occur in the side of the subestuary that is surrounded by forest and 10 patches in wetlands that are in the side of the subestuary that has extensive anthropogenic development. Seed viability varied from 0–60% among the 20 patches but did not differ significantly between patches on the developed vs. forested sides of the Rhode River. Foliar nutrients also did not differ between patches on the two sides of the Rhode River. Seed viability, however, was negatively related to foliar nutrients. Most Phragmites patches consisted of >1 genotype. Larger patches had multiple genotypes, and patches with more genotypes produced more viable seeds. Our study indicates that the Rhode River subestuary behaves as one system with no differences in the measured Phragmites variables between the forested vs. developed sides of the watershed. Our findings also suggest a cyclical process by which Phragmites can spread: larger patches contain more genetic diversity, which increases the chances for cross-fertilization. The subsequent increased production of viable seeds can increase local levels of genetic diversity, which can further facilitate the spread of Phragmites by seed.     

济南市一次大雾天气过程的诊断分析

利用济南地区地面气象观测资料和探空观测资料以及NCEP1°×1°再分析资料，对2007年1月2-4日济南地区大雾形成及持续原因进行了初步分析，发现：稳定的经向大气环流、较弱的地面气压场是大雾形成的主要天气形势，较弱而持续的偏北风、源源不断的水汽补充及明显的逆温层是这次大雾形成并维持的必要条件。在实际气象预报工作中，不仅要注意天气形势、水汽等条件的分析，在冬季更要注重逆温层对大雾形成的分析。     

Distribution and source of heavy metals in the surface sediments from the near-shore area,north Jiangsu Province,China

Samples of surface sediment and vibrocore were collected in the near-shore area of north Jiangsu Province for grain size, elements, ²¹⁰Pb_excess and ¹³⁷Cs analyses. In our study area, the diversity of metal concentration was controlled not by the grain size, but by the source. The element content of the old Yellow River Delta was used as baseline for our study area. Geoaccumulation indexes indicate that no station was polluted by Cu, Pb, Zn and As, but the I_geo values of As were close to zero in some stations. Slight pollution caused by Cd was observed in some stations. Correlation and enrichment factors suggest that Cu, Pb and Zn are lithogenic in origin, while As and Cd are mixed in origin. Especially, in some polluted stations Cd was obviously anthropogenic in origin.     

Segmentation algorithm for long time series analysis

Time series analysis is an important issue in the earth science-related engineering applications such as hydrology, meteorology and environmetrics. Inconsistency and nonhomogeneity that might arise in a time series yield segments with different statistical characteristics. In this study, an algorithm based on the first order statistical moment (average) of a time series is developed and applied on five time series with length ranging from 84 items to nearly 1,300. Comparison to the existing segmentation algorithms proves the applicability and usefulness of the proposed algorithm in long hydrometeorological and geophysical time series analysis.     

Assessment of three temperature reconstruction methods in the virtual reality of a climate simulation

The performance of statistical climate reconstruction methods in the pre-instrumental period is uncertain, as they are calibrated in a short instrumental period but applied to much longer reconstructions time spans. Here, the virtual reality created by a climate simulation of the past millennium with the model ECHO-G is used as a test bed of three methods to reconstruct the annual Northern Hemisphere temperature. The methods are Composite plus Scaling, the inverse regression method of Mann et al. (Nature 392:779–787, 1998) and a direct principal-components regression method. The testing methodology is based on the construction of pseudo-proxies derived from the climate model output, the application of each of these methods to pseudo-proxy timeseries, and the comparison of their result with the simulated mean temperature. Different structures of the noise have been used to construct pseudo-proxies, ranging from the simulated grid-point precipitation. Also, one sparse and one denser pseudo-proxy network, co-located with two real networks, have been considered. All three methods underestimate the simulated variations of the Northern Hemisphere temperature, but the Composite plus Scaling method clearly displays a better performance and is robust against the different noise models and network size. The most relevant factor determining the skill of the reconstruction appears to be the network size, whereas the different noise models tend to yield similar results.     

电镀PDC石油全面钻头及其在油气田中的应用

采用低温电镀工艺生产ＰＤＣ石油全面钻头对金刚石无任何热损伤，对喷咀进行组合设计，在两口井中进行试验，取得了很好的经济效益和社会效益，并分析了钻头的特点及存在的问题。