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151.
九龙江河口区水体中的226Ra和228Ra 总被引:8,自引:0,他引:8
用MnO2-纤维富集大体积水样中的Ra同位素,并用直接射气法测定226Ra和228Ac的β计数法测定228Ra的方法,研究了九龙江河口区226Ra,228Ra的行为,结果表明:在该河口区226Ra,228Ra均呈非保守行为,226Ra,228Ra的最高值分别在盐度为19和9处测得。228Ra/226Ra)A.R.值在盐度小于19的区域约为3左右。与世界其他河口区相比,九龙江河口区的226Ra,22 相似文献
152.
冰心中的气候环境记录与全球变化研究 总被引:1,自引:0,他引:1
冰心是高分辨地记录全球变化的主要信息载体之一。本文总结了冰心中提取古气候和古环境信息的系列记录,包括同位素、微量气体、阴阳离子、微粒、生物和有机质等。着重讨论了由这些记录提取的古气候和古环境变化方面的研究进展,并提出了今后的研究重点。 相似文献
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156.
Noriaki Kimura 《Journal of Oceanography》2007,63(4):685-694
This paper examines the mechanism controlling the short time-scale variation of sea ice cover over the Southern Ocean. Sea
ice concentration and ice velocity datasets derived from images of the Defense Meteorological Satellite Program (DMSP) Special
Sensor Microwave Imager (SSM/I) are employed to reveal this mechanism. The contribution of both dynamic and thermodynamic
processes to the change in ice edge location is examined by comparing the meridional velocity of ice edge displacement and
sea ice drift. In the winter expansion phase, the thermodynamic process of new ice production off the ice edge plays an important
role in daily advances of ice cover, whereas daily retreats are mostly due to southward ice drift. On the other hand, both
advance and retreat of ice edges in the spring contraction phase are mostly caused by the dynamic process of the ice drift.
Based on the above mechanism and the linear relation between the degree of ice production at the ice edge and northward wind
speed, the seasonal advance of ice cover can be roughly reproduced using the meridional velocity of ice drift at the ice edge. 相似文献
157.
Two distinct series of slumps deform the upper part of the sedimentary sequence along the continental margin of the Levant.
One series is found along the base of the continental slope, where it overlies the disrupted eastern edge of the Messinian
evaporites. The second series of slumps transects the continental margin from the shelf break to the Levant Basin. It seemed
that the two series were triggered by two unrelated, though contemporaneous, processes. The shore-parallel slumps were initiated
by basinwards flow of the Messinian salt, that carried along the overlying Plio-Quaternary sediments. Seawater that percolated
along the detachment faults dissolved the underlying salt to form distinctly disrupted structures. The slope-normal slumps
are located on top of large canyons that cut into the pre-Messinian sedimentary rocks. A layer of salt is found in the canyons,
and the Plio-Quaternary sediments were deposited on that layer. The slumps are bounded by large, NW-trending faults where
post-Messinian faulted offset was measured. We presume that the flow of the salt in the canyons also drives the slope-normal
slumps. Thus thin-skinned halokynetic processes generated the composite post-Tortonian structural patterns of the Levant margin.
The Phoenician Structures are a prime example of the collapse of a distal continental margin due to the dissolution of a massive
salt layer. 相似文献
158.
台湾岛的雨量受台湾山地的雨影效应影响明显,各地各月随着风向的不同,雨量表现出很大的差异。福建沿海一线存在着一个雨量低值区,主要是由于该地带所处的地理位置及地形条件所决定,与台湾山地的雨影效应无关。 相似文献
159.
在20×10~9Pa和25×10~9Pa条件下,对石榴石橄榄岩进行的14次高温高压熔融实验研究表明,在1600℃时石榴石橄榄岩开始熔融(初熔),熔体中的SiO_2>70%,Na_2O+K_2O>8%,类似于A型花岗岩成分。本实验为地幔花岗岩的成因提供了证据。 相似文献
160.
Using meteorological data of field observation in 1990 - 2000, especially polar orbit high-resolution NOAA satellite cloud maps received from the Antarctic expedition vessel since 1997, the formation and development of the Prydz Bay cyclone are studied in this paper. Some new viewpoints are suggested such as: when surround-polar cyclone enters the Prydz Bay, it can also intensify and develop in summer; cyclone can also develop in the easterlies in this bay. These view points revise old uncom-plete view point that the Prydz Bay is a burial ground of cyclone, and also further consummate formation-development theory of surround-cyclone in the Antarctic westerlies and cyclone in the Antarctic easterlies. In this paper, the mechanism of ice-air-sea interaction in the Prydz Bay is studied, and the physical process of cyclone formation-development is explained. By use of wholly dynamic transportation method, an energy exchange case of a cyclone, which explosively developed after entering the Prydz Bay, is calcu 相似文献