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61.
Yoshiki Saito 《中国科学D辑(英文版)》2006,49(6):604-614
The last 2000 years are an important time span both for IGBP-PAGES and CLIVAR of WCRP. One of the main aims of these projects is to obtain high-resolution records of global change, such as that stored in ice cores, tree rings, speleothems, corals, lakes, marine records, etc., and then use these data to make sound estimates for future global change. To accomplish these projects, we first need to obtain high-resolution geological records and proxies for climatic/environ- mental changes. … 相似文献
62.
Results from an ice-ocean coupled model are used to investigate the impact of long-term variability in sea ice transport at
the Fram Strait on the intensity of the Atlantic deep circulation. An increase (or decrease) in sea ice transport through
the Fram Strait leads to a stronger (or weaker) deep circulation in the Atlantic. Change in the sea ice transport is accompanied
by a salinity anomaly in the surface layer of the Arctic Ocean. Such an anomaly could inversely affect the Atlantic circulation
once it reaches deep water formation regions. If the Canadian Archipelago is closed, the anomaly is subsequently transported
through the Fram Strait, and counters the initial changes in the Atlantic deep circulation. On the other hand, if the Canadian
Archipelago is open, some of the anomaly is transported to the Canadian Archipelago, and the initial change in the Atlantic
deep circulation persists. In the Arctic Ocean basin, the time scale and path of the salinity anomalys propagation depends
on the large-scale flow at the surface of the Arctic Ocean. Our results suggest that the salinity anomaly transport and its
propagation pathway out of the Arctic Ocean are important determinants of the role of sea ice transport variability through
the Fram Strait in controlling the intensity of the Atlantic deep circulation. 相似文献
63.
东亚东倾地形格局的形成与季风系统演化历史寻踪——综合大洋钻探计划683号航次建议书简介 总被引:2,自引:1,他引:1
郑洪波 汪品先 刘志飞 杨守业 王家林 李前裕 周祖翼 贾军涛 李上卿 贾健宜 John Chappell Yoshiki Saito Takahiro Inoue 《地球科学进展》2008,23(11):1150-1160
围绕IODP 683号建议书,介绍东亚东倾地形格局与季风系统演化历史的相关研究。新生代全球宏观环境格局发生了一系列重大变化,表现为岩石圈活动强烈,板块漂移导致海陆格局和地貌格局的变化,并引发洋流和大气环流的改组,最终导致全球气候的重大变化。新生代岩石圈运动和气候变化表现最为典型的地区是亚洲,其中最具标志性和全球意义的地质事件是喜马拉雅山和青藏高原的隆升及亚洲季风系统的形成与演化。青藏高原隆升最直接的结果是亚洲地区现代地貌格局的形成,大江大河的发育,并在很大程度上影响了亚洲季风系统的形成与演化。综合大洋钻探计划683号航次建议书,计划在长江中下游盆地和东海陆架盆地实施钻探,以获得长江历史演化和东亚季风演化的地质记录,并为研究青藏高原的演化提供新的证据。 相似文献
64.
2万年来我国东部海陆环境变化的不同步现象 总被引:9,自引:0,他引:9
冲绳海槽DG9603孔高分辨率的硅藻、有孔虫、孢粉和植物硅酸体化石的记录,提供了联系海洋与陆地气候变化的直接证据。结果显示,中国东部及邻海区最近20kaBP以来海洋环境的文化滞后陆地气候的变化约1000a,初步认为这种滞后现象可能是北半球陆地气候快速变化的同步性和温盐环流从北大西洋缓慢传送到太平洋海域的时间差引起的。 相似文献
65.
Reaction of juvenile flounder to grid separators 总被引:1,自引:0,他引:1
Matsushita Yoshiki; Fujita Kaoru; Ikegami Naoya; Ohata Satoshi 《ICES Journal of Marine Science》2004,61(7):1174-1178
66.
Detailed rock magnetic investigations were undertaken at 2~4 cm interval for the gravity core CSH1(with a length of 17.36 m) from the northern Okinawa Trough.Time-scale of the core was constructed by two characteristic tephras and foraminferal assemblages,indicating an age of 50 ka for the bottom of the core.Except for three tephras and abrupt decrease in surface,there are little changes in all kinds of rock magnetic parameters that can be correlated to the climate change for the last 50 ka.Different from the common sediments,most S-ratios(S equals the negative ratio of IRM-0.3T to SIRM,which is an indicator of low coercivity content)of the sediments are smaller than 0.9,which implies a substantial amount of magnetic minerals with high coercivity.The existence of iron sulphide(greigite or pyrrhotite) is revealed by representative susceptibility-temperature curves showing 200~350 ℃ Curie temperature in addition to 580 ℃ of magnetite,and also by awful smell during heating and dark heating products.Both the occurrence of authigenic iron sulphide and quick decrease of magnetic parameters near the surface clearly show that sediments from Core CSH1 have undergone early diagenesis.The featureless magnetic changes of the whole core except for three tephras mean that the post-depositonal alteration is so strong that most original signals have been destroyed.For the same reason,the organic matter in sediment and sulphate in pore water must have been consumed along with dissolution,precipitation of iron and manganese happening sequencially during the redox reaction series.Great caution must be taken when using these altered chemical parameters for the interpretation of climatic changes. 相似文献
67.
Distribution of Trace Bioelements in the Subarctic North Pacific Ocean and the Bering Sea (the R/V Hakuho Maru Cruise KH-97-2) 总被引:2,自引:1,他引:2
Yukiyo Fujishima Kazumasa Ueda Masahiro Maruo Ehchiro Nakayama Chikako Tokutome Hiroshi Hasegawa Masakazu Matsui Yoshiki Sohrin 《Journal of Oceanography》2001,57(3):261-273
A column concentration-high resolution inductively coupled plasma mass spectrometry (ICP-MS) determination was applied to measure the total dissolved concentrations of Fe, Co, Ni, Cu and Zn in seawater collected from the subarctic North Pacific (~45°N) and the Bering Sea in July–September 1997. Total adsorbable Mn was determined on board by column electrolysis preconcentration and chemiluminescence detection. The vertical profiles for Fe, Ni and Zn were nutrient-like. The deep water concentration of Fe was ~0.5 nM in the northeast Pacific (18°-140°W) and increased to ~1 nM in the northwest Pacific (161°E) and ~2 nM in the Bering Sea (57°N, 180°E). The deep water concentrations for Ni and Zn in the Bering Sea were also 1.3–2 times higher than in the North Pacific. The profiles for Co and Cu were examined in the subarctic North Pacific, and results obtained were consistent with previous reports. There was a significant correlation between the concentrations of Co and Mn except for surface mixed layer. The profiles for total adsorbable Mn were similar to the reported profiles for total dissolvable Mn. The deep water concentration of Mn in the Bering Sea was also 4 times higher than in the North Pacific. Iron and zinc were depleted in surface water of the subarctic North Pacific. The relationship between these trace elements and nutrients suggests that these elements could be a limiting factor of phytoplankton productivity. In the Bering Sea, surface water contained ~0.3 nM of Fe. The Zn concentration, which was less than the detection limit in surface water, increased at shallower depths (~30 m) compared with the subarctic North Pacific. These results imply a higher flux of Fe and Zn to surface water in the Bering Sea. This in turn may cause the ecosystem in the Bering Sea characterized by a dominance of diatoms and high regenerated production. 相似文献
68.
Wood Nathan Jones Jeanne M. Yamazaki Yoshiki Cheung Kwok-Fai Brown Jacinta Jones Jamie L. Abdollahian Nina 《Natural Hazards》2019,95(3):505-528
Natural Hazards - Population vulnerability from tsunamis is a function of the number and location of individuals in hazard zones and their ability to reach safety before wave arrival. Previous... 相似文献
69.
Geochemical characteristics of sediment as indicators of post-glacial environmental changes off the Shandong Peninsula in the Yellow Sea 总被引:4,自引:0,他引:4
Core NYS-101, which was recovered at a water depth of 49 m northeast of the Shandong Peninsula in the North Yellow Sea, penetrates the Holocene subaqueous clinoform that wraps around the Shandong Peninsula. The uppermost 18 m of this well-dated core was deposited after about 13 cal kyr BP during the post-glacial transgression. We focused on trace and rare earth element (REE) chemistries of the core sediments in the uppermost 18 m to investigate the sediment provenance and factors controlling the sediment composition. On the basis of down-core distributions of REE fractionation parameters and of ratios among REEs and other immobile elements, we divided the uppermost 18 m into three distinct compositional intervals: Interval 1 (above 6.08 m, from the time tens of years earlier than 6500 cal yr BP up to the present), Interval 2 (13.90–6.08 m, from about 8200 cal yr BP to the boundary between Intervals 1 and 2), and Interval 3 (below 13.90 m, from about 13,000 to 10,400 cal yr BP). The chondrite- and upper continental crust (UCC)-normalized REE fractionation patterns of Intervals 3 and 2 are similar to those of Yellow River sediments, but the patterns in Interval 1 are obviously different. 相似文献
70.
Yu Otsuki Masahiro Kurata Konstantinos A. Skalomenos Yoshiki Ikeda Motoki Akazawa 《地震工程与结构动力学》2019,48(9):1007-1029
Expansion joints are used as a special connection equipment between adjacent buildings to accommodate the relative motions generated by wind, thermal, or earthquake loads, but they often exhibit damage during severe earthquakes. The level of damage and safety factors required to avoid loss of function are not well considered in current design practices. The objective of this paper is to provide quantitative information on the seismic damage probability of common expansion joints and the associated repair costs. The designer and engineer can refer to this information as a basis for decision making in the selection of expansion joints. Four common types of expansion joints are considered: high- and standard-performance floor and wall expansion joints, whose damage states have been evaluated recently by the authors through shaking table tests. First, the fragility functions of expansion joints for seven damage patterns are developed utilizing the test results. Next, the vulnerability of expansion joints installed between adjacent building models is assessed via incremental dynamic analysis. The recommended level of safety factor to ensure the function of expansion joints is discussed. Finally, a procedure for cost-effective selection of expansion joints is introduced, where case studies are examined using buildings with different characteristics. The presented results are deemed to be beneficial for improving the design practice of expansion joints and for reducing future seismic loss. 相似文献