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101.
古海洋溶解氧研究方法综述 总被引:15,自引:0,他引:15
介绍了国内外在古海洋溶解氧研究领域内的主要方法和动态,并分别对沉积构造法、沉积硫法、同位素法、微量元素法、稀土元素法、有机地球化学法及古生态法等研究方法进行了全面的分析和评论,指出,古海洋溶解氧含量重建对于理解大洋循环、古气候、生物绝灭、地质事件以及有机质演化具有十分重要的科学意义,它有赖于溶解氧含量的替代性指标的建立、富氧问题研究的进一步深入以及综合分析气圈、水圈、沉积圈、生物圈等各子系统内部及它们之间氧的物质输送和转化。 相似文献
102.
103.
Oceanic general circulation models have become an important tool for the study of marine status and change. This paper reports a numerical simulation carried out using LICOM2.0 and the forcing field from CORE. When compared with SODA reanalysis data and ERSST.v3 b data, the patterns and variability of the tropical Pacific–Indian Ocean associated mode(PIOAM) are reproduced very well in this experiment. This indicates that, when the tropical central–western Indian Ocean and central–eastern Pacific are abnormally warmer/colder, the tropical eastern Indian Ocean and western Pacific are correspondingly colder/warmer. This further confirms that the tropical PIOAM is an important mode that is not only significant in the SST anomaly field, but also more obviously in the subsurface ocean temperature anomaly field. The surface associated mode index(SAMI) and the thermocline(i.e., subsurface) associated mode index(TAMI) calculated using the model output data are both consistent with the values of these indices derived from observation and reanalysis data. However, the model SAMI and TAMI are more closely and synchronously related to each other. 相似文献
104.
105.
We investigate the seismic structure of the western Philippine Sea using two sets of seismological observations: ScS reverberations, which provide the layering framework for a regional upper mantle model, and observations of frequency-dependent phase delays for direct S waves, surface-reflected phases (sS, SS, sSS), and surface waves (R1, G1), which constrain the velocity and anisotropy structure within the layers. The combined data set, comprising 17 discontinuity amplitudes and layer travel times from the ScS-reverberation stack and more than 1000 frequency-dependent phase delays, was inverted for a path-averaged, radially anisotropic model. Mineralogical estimates of the bulk sound velocity and density are incorporated as complementary constraints. The final model, PHB3, is characterized by a 11.5-km thick crust, an anisotropic lid bounded by a sharp negative G discontinuity at 89 km, an anisotropic low-velocity layer extending to 166 km, a subjacent high-gradient region, and transition-zone discontinuities at depths of 408 km, 520 km and 664 km. The lid is slower than in a comparable model for the Tonga–Hawaii corridor (PA5), but also significantly thicker, requiring a compositional variation between the two regions. We explore the hypothesis that the thickness of the oceanic lid is controlled by the melting depth at the spreading centers during crust formation, and that the thicker crust and lid in the Philippine Sea results from deeper melting owing to a higher potential temperature and perhaps a higher water content in the upper mantle. 相似文献
106.
During and after the very wet 1991/1992 winter experienced in Jordan, significant instabilities occurred in several sections
of the new Irbid–Amman Highway in Jordan. A potential impact of surface and subsurface flow on the failed areas was noted.
This paper is concerned with a hydrological study of the Irbid–Amman Highway, including watershed characteristics, hydrological
data analysis, and hydraulic analysis of remedial works to failed areas and other parts of the highway drainage to minimize
the impact of surface runoff and the effects of subsurface water with respect to the stability of the upslope and to limit
the porewater pressure within the road formation. The study shows that the culvert capacity and the discharge velocity of
the cross-highway drainage are deficient. Recommendations (e.g. gabion cascades) are therefore suggested to reduce drainage
to the cross highway drainage structures. Grouting is suggested to stabilize the embankments above the inlets to culverts.
Remedial drainage works are suggested for each major failed area. These include: culverts, table drain, drainage blanket beneath
road formation, cut-off drains above cuttings, subsurface drains into the cut in the vicinity of springs, curtain drain beneath
the lined table drain, and others.
Received: 26 March 1997 · Accepted: 23 March 1998 相似文献
107.
108.
Direct Measurements of Deep Currents in the Northern Japan Sea 总被引:5,自引:0,他引:5
Masaki Takematsu Zentaro Nagano Alexander G. Ostrovski Kuu Kim Yuri Volkov 《Journal of Oceanography》1999,55(2):207-216
Long-term current measurements by means of subsurface moorings were made for the first time at seven sites in the Japan Basin,
the northern part of the Japan Sea. The objective was to directly explore the velocity field in the highly homogeneous deep
water mass (the Japan Sea Proper Water) that occupies depths below 500 m. On each mooring three current meters were equipped
at an approximately equal distance below about 1000 m depth. Duration of the measurements was 1 to 3 years depending on specific
site. This paper describes the basic data set from the moored measurements. It is found that the deep water of the Japan Basin
is very energetic with eddies and vertically coherent currents of the order of 0.1 m/s. Surprisingly, the currents and eddies
exhibit strong seasonal dependence even in the deepest layers of the Basin. The observed new current features are discussed
in comparison with conventional deep circulation pictures derived from hydrographic data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
109.
110.
Piping dynamics in mid‐altitude mountains under a temperate climate: Bieszczady Mountains,eastern Carpathians 下载免费PDF全文
Piping has been recognized as an important geomorphic, soil erosion and hydrologic process. It seems that it is far more widespread than it has often been supposed. However, our knowledge about piping dynamics and its quantification currently relies on a limited number of data for mainly loess‐derived areas and marl badlands. Therefore, this research aimed to recognize piping dynamics in mid‐altitude mountains under a temperate climate, where piping occurs in Cambisols, not previously considered as piping‐prone soils. It has been expressed by the estimation of erosion rates due to piping and elongation of pipes in the Bere?nica Wy?na catchment in the Bieszczady Mountains, eastern Carpathians (305 ha, 188 collapsed pipes). The research was based on the monitoring of selected piping systems (1971–1974, 2013–2016). Changes in soil loss vary significantly between different years (up to 27.36 t ha?1 yr?1), as well as between the mean short‐term erosion rate (up to 13.10 t ha?1 yr?1), and the long‐term (45 years) mean of 1.34 t ha?1 yr?1. The elongation of pipes also differs, from no changes to 36 m during one year. The mean total soil loss is 48.8 t ha?1 in plots, whereas in the whole studied catchment it is 2.0 t ha?1. Hence, piping is both spatially and temporally dependent. The magnitude of piping in the study area is at least three orders of magnitude higher than surface erosion rates (i.e. sheet and rill erosion) under similar land use (grasslands), and it is comparable to the magnitude of surface soil erosion on arable lands. It means that piping constitutes a significant environmental problem and, wherever it occurs, it is an important, or even the main, sediment source. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献