The Role of the Solar Cycle in the Relationship Between the North Atlantic Oscillation and Northern Hemisphere Surface Temperatures

The North Atlantic Oscillation （NAO） is one of the leading modes of climate variability in the Northern Hemisphere. It has been shown that it clearly relates to changes in meteorological variables, such as surface temperature, at hemispherical scales. However, recent studies have revealed that the NAO spatial pattern also depends upon solar forcing. Therefore, its effects on meteorological variables must vary depending upon this factor. Moreover, it could be that the Sun affects climate through variability patterns, a hypothesis that is the focus of this study. We find that the relationship between the NAO/AO and hemispheric temperature varies depending upon solar activity. The results show a positive significant correlation only when solar activity is high. Also, the results support the idea that solar activity influences tropospheric climate fluctuations in the Northern Hemisphere via the fluctuations of the stratospheric polar vortex .     

Definition and character of the Regency Interglacial and Early-Middle Pleistocene stratigraphy in the King Valley, western Tasmania, Australia

Interpretation of weathered glacial and interglacial deposits in the lower King Valley suggests that the Early Pleistocene Thureau Formation is conformably overlain by the Regency Formation. Pollen analysis of the Regency Formation provides evidence of a new climatic stage, the Regency Interglacial. The interglacial deposit consists of humified peat overlain by drifted wood and leaves. The pollen analysis shows a transition from montane scrub rainforest to lowland temperate rainforest dominated by Lagarostrobos franklinii, Nothofagus cunninghamii and Phyllocladus aspleniifolius. Trace quantities of the species Quintinia psi-latispora and Gothanipollis perplexus , now both extinct in Tasmania, were also recorded. On the basis of intense chemical weathering and correlation with sediments that have a reversed magnetization the weathered glacial deposits of the Thureau Formation are thought to be older than 730,000 B.P. The eroded interglacial deposit rests on the weathered deposits and is buried by outwash gravels of the David Formation, which was deposited during an ice advance of the Middle Pleistocene Henty Glaciation (c. 150,000 B.P.). Comparison of the Regency site with a site 2 km to the south at Baxter Rivulet shows that the unconformity between the interglacial deposit and the overlying outwash gravel represents the erosion of the evidence for the Middle Pleistocene Moore Glaciation.     

井间电磁成像系统应用研究

井间电磁（EM）成像系统的技术目标是实现井间电学特性的直接测量,并提供井间电阻率的二维及三维图像.从1997年开始,胜利油田与美国EMI公司合作,开展了EM技术的应用与研究,主要是通过大型、系统的现场试验,在大井间距的条件下,进一步验证仪器的性能,进行油藏研究的适用性和可行性分析;以系统的现场实测数据为依据,加快成像处理方法和软件的开发;开展穿透金属套管井的EM试验,探讨金属套管条件下的电阻率成像方法。两年来,利用EMI提供的XBH2000型测量系统,对胜利油田典型的低电阻率砂泥岩剖面,成功地进行了3对井、10个井次的试验。试验证明了仪器性能的可靠,取得了测量重复性好、系统完整的井间EM数据.并反演得到电阻率成像,在分析井间油气分布和油层开采动态方面,取得了良好的地质效果.     

Changes in velocity profiles at roughness transitions in coarse grained channels

Heterogeneous coarse grained channels are often characterized by local transitions in bed surface roughness. Distinct spatial zones in terms of grain size have been reported, for example sand ribbons and bedload sheets. The transition from areas of finer to coarser grained surface sediment is often abrupt. However, the effects of these transitions on the shape of the velocity profile and associated shear velocity and roughness length estimates have not been investigated in detail in coarse grained channels. This paper therefore examines the combined effects of a sudden change in surface roughness and of superimposed scales of resistancé on the structure of the turbulent boundary layer. Measurements along roughness transitions from smooth to rough beds were conducted in a flume using artificial roughness features and in a natural gravel bed river. Immediately at the transition from a zone of close packed roughness to a rougher section dominated by obstacles superimposed on the more or less uniform roughness surface, boundary shear stress and roughness length increase considerably. Downstream from this transition, velocity profiles become concave upwards. Downstream and upstream sections show significant differences in terms of near bed velocities (deceleration downstream of the transition), velocity gradient and turbulence intensity of the streamwise velocity component. Comparing the mean velocity profiles corresponding to these two different roughness surfaces gives some indication of the proportion of total shear velocity (or shear stress) associated with the pressure drag produced by large and isolated obstacles.     

中国早期人类分布的环境制约因素探讨

在环境因素起制约作用的背景下,随着中国古人类演化与生存能力的进步,其数量和空间分布在不同时间段呈现出不同的特征。为了更好地了解中国早期人类的时空分布特征,本研究以中国境内已发表的2110处旧石器遗址的坐标和年代信息为基础,采用统计学和空间分析的方法,对遗址的时间分布进行以蒙特卡洛模拟为基础的时间不定性模拟,对遗址的空间分布进行核密度估计和聚类分析;同时,利用环境空间数据集中的海拔、水源、气温和降水信息,对不同时期内各个遗址所在地的环境条件进行统计分析。研究结果表明,在旧石器时代,随着时间的发展,中国境内的遗址数量不断增多,分布范围也逐渐从中部、南部和东部地区向条件较恶劣的北部和西部扩张。其中,600 ka和57 ka为这一变化的两个关键时间点,600 ka之前遗址数量较少,分布也较为局限;在600 ka至57 ka之间,遗址数量缓慢增加,分布范围也在季风区内逐渐扩大;57 ka之后,遗址数量迅速增长,分布遍布中国境内的大部分地区。本文所梳理的中国境内旧石器遗址整体时空分布特征,为进一步解读中国早期人类的环境适应能力,特别是古人类的体质演化和技术进步的环境驱动机制提供参考。

     

Seismic evidence of up to 200 m lake‐level change in Southern Patagonia since Marine Isotope Stage 4

Maar lake Laguna Potrok Aike is located north of the Strait of Magellan (south‐eastern Patagonia). Seismic reflection profiles revealed a highly dynamic palaeoclimate history. Dunes were identified in the eastern part of the lake at approximately 30 to 80 m below the lake floor, overlying older lacustrine strata, and suggest that the region experienced dry conditions probably combined with strong westerly winds. It is quite likely that this can be linked to a major dust event recorded in the Antarctic ice cores during Marine Isotope Stage 4. The dunes are overlain by a series of palaeo‐shorelines indicating a stepwise water‐level evolution of a new lake established after this dry period, and thus a change towards wetter conditions. After the initial, rapid and stepwise lake‐level rise, the basin became deeper and wider, and sediments deposited on the lake shoulder at approximately 33 m below present‐day lake level point towards a long period of lake‐level highstand between roughly 53·5 ka cal. bp and 30 ka cal. bp with a maximum lake level some 200 m higher than the desiccation horizon. This highstand was then followed by a regressional phase of uncertain age, although it must have happened some time between approximately 30 ka cal. bp and 6750 yrs cal. bp . Dryer conditions during the Mid‐Holocene are evidenced by a dropping lake level, resulting in a basin‐wide erosional unconformity on the lake shoulder. A second stepwise transgression between ca 5·8 to 5·4 ka cal. bp and ca 4·7 to 4 ka cal. bp with palaeo‐shorelines deposited on the lake shoulder unconformity again indicates a change towards wetter conditions.     

Wind tunnel and field testing of a simple sand catcher for sampling inhomogeneously saltating sand in desertified environments

Problems of vertical alignment and vibrations of disposable coffee cups used in a modified version of the De Ploey saltating sand catcher were solved. The new version was tested in a sediment wind tunnel. Its catches appeared linearly related to amounts of eroded sand, largely independent of wind speed and wind direction, and depended logarithmically on height. The catch efficiency may therefore be taken to be approximately independent of wind speed and direction. The instrument performed well under conditions of inhomogeneously saltating sand in a strongly desertified environment in Central Sudan. Use and results show the improved simple catcher to be easy to assemble, reproducible and cheap, suitable for multipoint use to cover all inhomogeneities in outdoor saltating sand fields.     

Optical dating of relict sand wedges and composite-wedge pseudomorphs in Flanders, Belgium

We report on quartz Optically Stimulated Luminescence (OSL) dating of the infill of 14 relict sand wedges and composite-wedge pseudomorphs at 5 different sites in Flanders, Belgium. A laboratory dose recovery test indicates that the single-aliquot regenerative-dose (SAR) procedure is suitable for our samples (measured to a given dose ratio 0.980 ± 0.005; n =139). Completeness of resetting of the wedge infill of two samples was confirmed by single-grain analyses. The suite of optical ages indicates that repeated thermal contraction cracking, degradation and infilling with wind-blown sediment appear to have been commonplace in Flanders during the Late Pleniglacial (Oxygen Isotope Stage 2; OIS2); more specifically, around the Last Glacial Maximum (LGM, ∼21 kyr ago) and the transition period between the LGM and the start of the Lateglacial (∼15 kyr ago). Optical dating at one site has revealed two significantly older wedge levels, the younger inset into the older; the younger wedge has an age of 36 ± 4 kyr (Middle Pleniglacial; OIS3), the older wedge 129 ± 11 kyr, which points to formation during the Late Saalian (OIS6). Our OSL ages of the wedges and host sediments bracket formation of the BGB (Beuningen Gravel Bed: a widespread deflation horizon in northwestern Europe) at between ∼15 and 18 kyr; this is in good agreement with previous OSL dating studies. We conclude that optical dating using quartz SAR OSL establishes an absolute chronology for these periglacial phenomena and allows secure palaeoenvironmental reconstructions to be made.     

The Merzbacher & Eggler (1984) Geohygrometer: a Cautionary Note on its Suitability for High-K Suites

The use of the popular Merzbacher & Eggler (1984, Geology12, 587–590) experimental geohygrometer for calcalkalineandesites and dacites is critically evaluated and two pitfallsare found. First, calculation of the correct projection parametersis problematic because two endmember calculation schemes arefound in the literature; Baker & Eggler (1983, Journal ofVolcanology and Geothermal Research 18, 387–404) and Walkeret al. (1979, Contributions to Mineralogy and Petrology 70,111–125). Although related, these two schemes have crucialdifferences that can result in very different projection parametersfor the plagioclase component. This is most crucial for high-Kcompositions; H₂O contents estimated using the Walker et al.(1979) scheme can be as much as 100% higher than those estimatedusing the Baker & Eggler (1983) projection. Incorrect projectionparameter calculation has led to overestimation of water contentsin high-K andesites and dacites from the Central Andes. Second,for medium-K and high-K andesitic–dacitic compositionswater contents derived using the Merzbacher & Eggler (1984)geohygrometer deviate considerably from water contents estimatedusing other methods. Experimental data from the literature,and our studies of water contents inferred from melt inclusionsand plagioclase–melt equilibrium for dacites from theAltiplano–Puna Volcanic Complex of the Central Andes indicatethat the Merzbacher & Eggler (1984) geohygrometer shouldnot be applied to compositions with K₂O >1·9 wt %,as originally calibrated. KEY WORDS: magmatic volatiles; pre-eruptive water; experimental geohygrometer; high-K suites; melt inclusion