Cores from boreholes penetrating late Quaternary, glacial, interglacial and postglacial sediments and the underlying late Cenozoic delta complex of the southern North Sea have been examined for their magnetic properties. A magnetic polarity stratigraphy has been established as an aid to biostratigraphic dating of the sediments; the Kaena-Gauss and Gauss—Matuyama transitions and the base and top of the Olduvai subchron have been identified. The strength and stability of laboratory-induced isothermal remanent magnetisation display clear magneto-petrological variations, which match lithostratigraphic changes in the cores. Principal component analysis has picked out a basin-wide and palaeoenvironmental consistency in the magnetic data. Large, multi-domain magnetite grains predominate in the post-deltaic and fluvio-deltaic sediments, whereas smaller greigite or titanomagnetite grains are concentrated in the intertidal and marine deltaic facies. Since heavy mineral analysis indicates that most of the deltaic detritus derived from common source areas, the differences in magnetic mineralogy have probably been caused by the sediment transport processes operating within the delta complex. 相似文献
利用NCAR公用陆面模式（Community Land Model 3.0,CLM3.0）及普林斯顿大学1948—2001年1°×1°、3 h一次的全球大气近地面强迫资料,对中国地区1948-2001年的土壤温度进行了off-line模拟试验,通过对模拟结果和全国台站观测土壤温度资料的对比,评估了CLM3.0对中国区域不同层次土壤温度的模拟能力。结果表明：模式能模拟出中国地区多年平均土壤温度的空间分布型,除部分地区模拟比观测偏高外,模式模拟的土壤温度普遍偏低;模式能较好地反映出中国地区土壤温度的年际变化,对4月的模拟稍好于7月。对于划分的8个子区域,东部区域模拟好于其它各区,除高原一带外,表层的模拟均好于深层;模式基本能抓住土壤温度的变化趋势,而且模拟出了7月长江流域以南地区土壤温度显著降低这一趋势,但模拟的趋势比观测有所偏弱。 相似文献
The salinization of freshwater-dependent coastal ecosystems precedes inundation by sea level rise. This type of saltwater intrusion places communities, ecosystems, and infrastructure at substantial risk. Risk perceptions of local residents are an indicator to gauge public support for climate change adaptation planning. Here, we document residential perspectives on the present and future threats posed by saltwater intrusion in a rural, low-lying region in coastal North Carolina, and we compare the spatial distribution of survey responses to physical landscape variables such as distance to coastline, artificial drainage density, elevation, saltwater intrusion vulnerability, and actual salinity measured during a synoptic field survey. We evaluate and discuss the degree of alignment or misalignment between risk perceptions and metrics of exposure to saltwater intrusion. Risk perceptions align well with the physical landscape characteristics, as residents with greater exposure to saltwater intrusion, including those living on low-lying land with high concentrations of artificial drainages, perceive greater risk than people living in low-exposure areas. Uncertainty about threats of saltwater intrusion is greatest among those living at higher elevations, whose properties and communities are less likely to be exposed to high salinity. As rising sea levels, drought, and coastal storms increase the likelihood of saltwater intrusion in coastal regions, integrated assessments of risk perceptions and physical exposure are critical for developing outreach activities and planning adaptation measures.
