SiB2和SiB3对高寒草甸和茶树地表能量通量模拟的比较

运用简单生物圈模式第2版(SiB2)和第3版(SiB3),分别模拟青藏高原两个观测站(那曲、安多)和长江三角洲苏州东山观测站的近地面能量收支,并与相应观测数据进行比较研究,分析SiB2、SiB3模拟结果和观测资料产生差异的原因,以此来认识上述地区地表能量收支特点。结果表明,SiB2和SiB3模拟的近地面能量通量与观测数据有较好的一致性。对感热通量,那曲和安多站SiB3比SiB2模拟的结果更接近观测资料,但苏州站SiB2模拟的结果与观测资料更吻合;对潜热通量,SiB3比SiB2模拟的日变化与观测资料更一致,SiB3的模拟结果与观测资料(除苏州站外)相关系数都在0.8以上;对地表土壤热通量,SiB2和SiB3模拟结果与观测数据相关系数都在0.8以上;对净辐射通量,SiB2和SiB3模拟结果与观测资料相关系数接近1.0。与SiB2相比,SiB3引用通用陆面模式的土壤描述并增加对冠层空间层温度、湿度和痕量气体的预报,使其能够改善潜热通量和土壤热通量的模拟,但对复杂下垫面的感热和净辐射通量模拟能力提高不明显。     

Decision makers' perspectives on European geographic information policy issues

The proposals for a European policy framework for Geographic Information (GI) recently put forward by Directorate General XIII raise three sets of issues about measures required to facilitate the dissemination of GI in the European Union: (1)'hot topics' such as privacy and the legal protection of databases that apply to information generally; (2) GI issues such as reference data and metadata services that may require action by the European Commission; and (3) perceived barriers to the development of a European GI market. This paper examines the views of 20 experts responsible for the provision and management of GI in key organizations throughout Europe. A Delphi-style strategy was used to identify the relative importance of the issues raised by the proposals and to ascertain the level of agreement as to the importance of these issues between the experts. The results show that issues relating to copyright, the protection of intellectual property rights, data quality, and data access policies were ranked highly by most of the respondents. A lack of awareness, education, and training (as opposed to the lack of public domain data and metadata services) were viewed as the main barriers to the deveiopment of the GI market in Europe.     

The relationship of porosity and angle of repose to mixture proportions in assemblages of different sized materials

Rotating drum experiments on the repose angles of mixtures of glass spheres have shown that φ_r (angle of shear) is strongly influenced by the proportions of the mixture. It was found that φ_r reached a peak value for the minimum porosity mixture; where the pore spaces between the large particles were just filled with small material; which was attributed to increased dilatation on the shear plane during avalanching. The geomorphic significance of these observations, in terms of slope development, is discussed. Secondly, the results of the experiments showed that, although more constant than φ_i (limiting angle of repose), φ_r was subject to some variation. Thus φ_r, as measured in a rotating drum, is not a true constant and can not be exactly analogous to φ'_cv (angle of internal sliding friction at constant volume) as measured in a shearbox test—as has been previously suggested. It is tentatively suggested that at least some of the variability in φ_r is attributable to the magnitude of the immediately preceding value of φ_i, in that an unusually high value of φ_i, favours a lower value of φ_r due to the greater amount of kinetic energy released on failure.     

A RAPID METHOD FOR THIN-SECTIONING CLAYS

Thin-sections of clays can be produced very rapidly and without impregnating by smoothing a face on dry glass plates, mounting the chip on “Araldite” adhesive and finally washing off the clay. A thin film of clay is preserved with larger mineral grains held firmly in place. This is suitable for wet staining techniques or for covering with Canada balsam.     

Complexity of the 8 ka climate event in Sweden recorded by varved lake sediments

Mineral magnetic and carbon analyses of a continuous varved lake sediment sequence in west-central Sweden (Lake Mötterudstjärnet) complement similar palaeoclimate proxies obtained from two varved lake sediment sequences in northern Sweden and one in central Finland. The varve chronology is supported by tephrochronology, palaeomagnetic secular variations and ¹⁴C AMS dating of terrestrial macrofossils. We apply a simple model in which the transport and deposition of catchment mineral matter reflect the amount of winter snow accumulation, spring snow-melt and stream discharge. Our data show that winter snow accumulation was generally enhanced in Sweden between 8100 and 7750 cal. yr BP. If dating errors are taken into account, the 350-year period of increased erosion is the geomorphic response to a multi-centennial scale climatic cooling that occurred some time between 8500 and 7500 cal. yr BP. The most significant erosion event in central Sweden was centred at 8050 cal. yr BP. It lasted 150 years (between 8100 and 7950 cal. yr BP) and is equivalent to the most extreme Holocene climate anomaly in the northern hemisphere, known as the 8 ka or 8200 cal. yr BP climate event. Our high-resolution paramagnetic susceptibility and ferrimagnetic grain-size parameters suggest that snowpack accumulation increased most significantly in northern Sweden between 7900 and 7750 cal. yr BP. We suggest that this north–south difference was a response to the re-establishment of moisture-laden westerly air masses, as meridional Atlantic overturning circulation was re-established at the beginning of the Holocene thermal maximum.     

Geomorphic features of Quaternary glaciation in the Taniantaweng Mountain,on the southeastern Qinghai-Tibet Plateau

We present geomorphological evidence for multiple glacial fluctuations during the Quaternary in the Taniantaweng Mountain, which is situated at the transition zone of the southeastern Qinghai-Tibet Plateau and the Yunnan-Guizhou Plateau. To reconstruct the history of glacial evolution during the Quaternary Glaciation, we present a ~13000 km~2 geomorphologic map(1:440,000) for the Quaternary glaciations, as well as three electron spin resonance(ESR) ages and three optically stimulated luminescence(OSL) ages from the landforms. By integrating these with ages from previous studies, four major glacial advances are identified during marine oxygen isotope stages(MIS) 6, 3, 2 and 1. This glacial chronology is in reasonable agreement with existing glacial chronologies from other parts of the Hengduan Mountains and surrounding mountains. Glaciers had extended to the Yuqu River during the glacial maximum advance(MIS 6), but became successively more restricted from MIS 3 to MIS 1. The glacial distribution show that precipitation brought by the south Asian monsoon might play a primary role in driving glacial advances during the last glacial period in the southeastern Qinghai-Tibet Plateau.     

Lateglacial–Holocene shoreface progradation offshore eastern Scotland: a response to climatic and coastal hydrographic change

Seismic facies, provenance and marine faunal associations of a nearshore prograding sediment wedge offshore eastern Scotland are studied to investigate environmental changes in the adjacent North Sea during Lateglacial–Holocene time. The sediments form part of the St. Andrews Bay Member (Forth Formation), which is divided into four lithozones (L1–L4) that represent distinct pulses of sedimentation during the sequential growth of the sediment wedge. Radiocarbon dates, combined with the local curve of relative sea level change, indicate that progradation was initiated as a fluvio-deltaic deposit (L1) during the Younger Dryas Stadial. Further construction of the sediment package took place during the mid- to late Holocene by sublittoral tidal processes that deposited three discrete, highstand shoreface wedges (L2–L4), which display both progradation and longshore migration (to the NE), and may have experienced episodic brackish marine conditions. A depositional cyclicity of about 1000 years is proposed for lithozones L2–L4, separated by hiatuses of 1000–2000 years. We tentatively suggest that the Holocene development of the prograding wedge offshore eastern Scotland was a response to phases of strong westerly winds driving an enhanced influx of Atlantic Water into the North Sea. A concomitant increase in rainfall may account for the freshening of the coastal zone at this time. However, correlation with the recently postulated global periods of Holocene rapid climate change remains unclear.     

A new lead mine in the northern Pennines

Plans by Durham County Council, owners of the Killhope Lead Mining Centre in Weardale, to open parts of the oroginal underground workings of Park Level Mine to visitors were frustrated when exploration of the mine revealed the seriously collapsed state of the workings. This disappointment has now been turned to advantage by the building of a new, 'artificial', specially constructed mine on the site, planned to be geologically consistent with the original mine. The new mine was recently officially opened by Tony Blair MP.     

Ringed seal Phoca hispida fright behaviour caused by walrus Odobenus rosmarus

Other marine mammals tend to avoid walruses. The present paper describes two incidents of avoidance behaviour displayed by ringed seals in the presence of a walrus.