Novel sledge net system employing propulsion vehicles for sampling demersal organisms on sandy bottoms     

Hiroyuki Munehara  Yoshiki Tanaka  Tomoyuki Futamura 《Estuarine, Coastal and Shelf Science》2009

A new sledge net system using propulsion vehicles has been developed to sample more efficiently the demersal juveniles of marine organisms. A net attached to a sledge maneuvered by a SCUBA diver who uses operating switches on a steering handle to adjust the altitude of the sledge and the position of the tickler chains to ensure that the footcloth of the mouth of the net remains in constant contact with the bottom surface. Video camera, flow meter, compass, and dive computers are positioned on the sledge net in the view of the diver. Given that the system can attain speeds of 70 cm s⁻¹, the net can be employed to capture highly mobile fish. Unlike most boat-based net sampling methods, the use of propulsion vehicles means that there are no sound or vibration disturbances due to the boat and tow ropes typically used to maneuver these types of sampling nets. Marine fauna was collected at monthly intervals over a two-year period in a sampling area along the southern coast of Hokkaido, Japan. A total of 2641 specimens comprising 61 species and including five species which were the first records for the region were collected. These findings suggest that the new sledge net system employing propulsion vehicles was effective for sampling demersal juveniles, particularly in situations where sledge nets towed by boats or push nets cannot be deployed.  相似文献   

Rock magnetic property of gravity core CSH1 from the northern Okinawa Trough and the effect of early diagenesis     

GE Shulan  SHI Xuef  WU Yonghu  LEE Tehquei  XIONG Yingqian  SAITO Yoshiki 《海洋学报(英文版)》2007,26(5):54-65

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   

An overview of decadal climate predictability in a multi-model ensemble by climate model MIROC   总被引：1，自引：1，他引：0  

Yoshimitsu Chikamoto  Masahide Kimoto  Masayoshi Ishii  Takashi Mochizuki  Takashi T. Sakamoto  Hiroaki Tatebe  Yoshiki Komuro  Masahiro Watanabe  Toru Nozawa  Hideo Shiogama  Masato Mori  Sayaka Yasunaka  Yukiko Imada 《Climate Dynamics》2013,40(5-6):1201-1222

Decadal climate predictability is examined in hindcast experiments by a multi-model ensemble using three versions of the coupled atmosphere-ocean model MIROC. In these hindcast experiments, initial conditions are obtained from an anomaly assimilation procedure using the observed oceanic temperature and salinity with prescribed natural and anthropogenic forcings on the basis of the historical data and future emission scenarios in the Intergovernmental Panel of Climate Change. Results of the multi-model ensemble in our hindcast experiments show that predictability of surface air temperature (SAT) anomalies on decadal timescales mostly originates from externally forced variability. Although the predictable component of internally generated variability has considerably smaller SAT variance than that of externally forced variability, ocean subsurface temperature variability has predictive skills over almost a decade, particularly in the North Pacific and the North Atlantic where dominant signals associated with Pacific decadal oscillation (PDO) and the Atlantic multidecadal oscillation (AMO) are observed. Initialization enhances the predictive skills of AMO and PDO indices and slightly improves those of global mean temperature anomalies. Improvement of these predictive skills in the multi-model ensemble is higher than that in a single-model ensemble.  相似文献   

Clashing strategic cultures and climate policy     

Megan Ceronsky  Cameron Hepburn  Michael Obersteiner  Yoshiki Yamagata 《Climate Policy》2013,13(4):347-357

Abstract

Kagan (2002) argues that the different responses of Europeans and Americans to major strategic and international challenges is not simply due to differences in the current administrations, but rather results from (i) a power gap and (ii) differing ideologies. This article applies Kagan's theory to climate policy, employing terrorism policy as a point of comparison. We argue that the power gap between Europe and America is unable to explain the differences in climate policy. In contrast, the ideology gap may indeed have some explanatory value. Furthermore, we argue that one additional feature is critical—the costs and benefits imposed by climate change and terrorism prevention, and the process by which such costs and benefits are evaluated, differ between America and Europe.  相似文献   

The Megadeltas of Asia: interlinkage of land and sea,and human development     

Zhongyuan Chen  Yoshiki Saito 《地球表面变化过程与地形》2011,36(12):1703-1704

This special issue describes research arising from the megadelta project of the Asia‐Pacific‐Networks (APN), undertaken between 2004 and 2009 ( www.megadelta.ecnu.edu.cn ). Numerous delta‐coast scientists from more than 20 countries were involved in the project concerned with developing our knowledge of land–estuarine–coastal interactions in megadeltas, and with fusing this knowledge with societal development and management. Project workshops were held in Bangkok (2004), Ho Chi Minh City (2005), Dhaka (2007) and Shanghai (2008) with over 500 participants. The main objectives of the project were: (1) development of regional databases; (2) understanding of delta formation and associated fluxes between land and sea; (3) knowledge transfer and building research capacity; and (4) understanding how better social management might follow. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Seismic-response-controlled structure with active mass driver system. Part 1: Design     

Takuji Kobori  Norihide Koshika  Kazuhiko Yamada  Yoshiki Ikeda 《地震工程与结构动力学》1991,20(2):133-149

An Active Mass Driver (AMD) system is proposed to suppress actively the response of a building to irregular external excitations such as earthquakes and typhoons. This system has been introduced to an actual ten-storey office building for the first time in the world. The system controls the motions of a structure by means of an external energy supply. It consists of an auxiliary mass installed in a building and an actuator that operates the mass and produces a control force which counters disturbances to the building. The design method of the AMD system, including the location of the installation and the capacity and stability of the system, is proposed. Simplification of the control algorithm is also described.  相似文献   

Assessment of RCM and urban scenarios uncertainties in the climate projections for August in the 2050s in Tokyo     

Hiroyuki Kusaka  Asuka Suzuki-Parker  Toshinori Aoyagi  Sachiho A. Adachi  Yoshiki Yamagata 《Climatic change》2016,136(3-4):427-444

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Dissolved and labile particulate Zr,Hf, Nb,Ta, Mo and W in the western North Pacific Ocean     

M. Lutfi Firdaus  Kazuhiro Norisuye  Yusuke Nakagawa  Seiji Nakatsuka  Yoshiki Sohrin 《Journal of Oceanography》2008,64(2):247-257

Dissolved and labile particulate Zr, Hf, Nb, Ta, Mo and W were determined at stations K1 (51°N, 165°E), K2 (47°N, 160°E), KNOT (44°N, 155°E) and 35N (35°N, 160°E) in the western North Pacific Ocean. A portion of seawater for dissolved species (D) was passed through a 0.2 μm Nuclepore filter and acidified to pH 2.2 with HCl and HF. A portion of seawater for acid-dissolvable species (AD) was acidified without filtration. Labile particulate (LP) species is defined as AD minus D, which represents a chemically labile fraction of particulate species. D-Zr, Hf and Ta increase with depth, Nb shows a slight depletion in surface water, whereas Mo and W have a conservative vertical profile. The concentration range of D-Zr, Hf, Nb, Ta and W is 31–275, 0.14–0.95, 4.0–7.2, 0.08–0.29 and 40–51 pmol kg⁻¹, respectively, whereas that of Mo is 97–105 nmol kg⁻¹. LP-species of Zr, Hf and Ta account for 10–14% of AD in average and increase up to 25% below 4000 m, whereas those for Mo and W are negligible. In contrast, LP-Nb shows maxima (up to 27%) in surface water. We also found that D-Zr/Hf, Nb/Ta and Mo/W mole ratios generally increase in the order continental crust < river water < coastal sea < open ocean.  相似文献   

近万年来冲绳海槽北部浮游藻类沉积率反映的环境变化   总被引：3，自引：0，他引：3  

吴国瑄  王吉良  宋长青  孙湘君  Saito Yoshiki 《海洋地质与第四纪地质》2000,20(4):69-74

对冲绳海槽北部B－3GC柱状样的84份样品做了浮游藻类（绝大多数是沟鞭藻孢囊）沉积率分析。冲绳海槽约6790a以前的全新世早期和3620－2390aB.P.两个阶段的沟鞭藻孢囊沉积率较高,特别是在全新世早期,孢囊沉积率明显高于其他阶段。沟鞭藻孢囊沉积率的变化反映了冲绳海槽北部全新世表层海水营养和生产力水平的变化,其趋势与黑潮影响强度的变化趋势一致。在黑潮影响甚微的全新世早期,表层海水富营养且高生产力,约6790aB.P.起黑潮影响强度明显加大,表层海水营养和生产力幅度下降,只是在3620－2390aB.P.期间因黑潮影响强度减弱而表层海水营养和生产力有小幅度上升。黑潮对于冲绳槽表层海水营养和生产力的营养,不公亩在为其本身低营养、低生产力的特性,也由于其对来自我国大陆一侧陆源输入物的阻隔作用。Operculodinium centrocarpum沉积率在剖面下段高于Spiniferites spp.,上段则呈相反的情况,Spiniferites spp沉积率较高,变化的转折点（约6790aB.P.)与黑潮对冲绳海槽影响强度出现骤然变化的时间吻合。所以,Operculodinium centrocarpum沉积率高实际上指示了偏低的表层水温,约6790aB.P.冲绳海槽北部表导水温明显上升。  相似文献   

High-resolution records of thermocline in the Okinawa Trough since about 10000 aBP     

Wang Jiliang  SAITO Yoshiki  OBA Tadamichi  JIAN Zhimin  WANG Pinxian 《中国科学D辑(英文版)》2001,44(3):193-200

The present paper uses planktonic foraminifera and their stable isotopes to study the changes in the depth of thermocline (DOT) in the Okinawa Trough since the last 10000 a based on the analysis of Core B-3GC in the northern Okinawa Trough, together with that of the core in the southern Okinawa Trough. As results show, the thermocline was shallow before 6400 aBP, and deepened afterward, then became shallow again from 4000 to 2000 aBP. The DOT fluctuations display a positive correlation with those of sea surface temperature (SST). In addition, the changes in the northern Okinawa Trough are similar to those in the southern trough, implying a possible connection with the variation of the Kuroshio Current. The changes of SST and DOT suggest that the Kuroshio Current changed its intensity or main axis from 4000 to 2000 aBP and around about 6400 aBP respectively. Moreover, the changes of DOT from 8200 to 6400 aBP may indicate a gradual intensification of the Kuroshio Current.  相似文献