日本中部地区上新世到更新世过渡时期的气候演变:来自水杉叶片化石稳定碳同位素及其形态性状的证据     

王雨晴  百原新  孙梅  王力  周浙昆 《第四纪研究》2015,35(3)

晚上新世至更新世是地质历史时期中十分重要的阶段,2.7Ma之后北半球由温暖湿润的气候进入冰期,水杉叶片化石稳定碳同位素值、叶片面积和叶片长宽比在地质历史时期的变化可以推测该时期内环境的变化趋势、探索植物对环境变化的响应.本研究选取日本中部地区的5个化石点(泉南郡、八王子市、东近江市、十日町市和生驹市)的水杉叶片化石(3.00～0.95Ma)材料.这些化石点的化石叶片稳定碳同位素值在八王子市(2.6～2.7Ma,晚上新世)出现最低值(-29.05‰±0.15‰),明显低于其他化石点材料的稳定碳同位素值,并且在此期间化石叶片的面积为7.45±1.31mm2,大于其他时期;同时,叶片的长宽比较大,为4.22±0.67.这些结果相互印证共同指示出,上新世与更新世交界时期存在一个间冰期;之后,气候逐渐变冷变于.并且本研究结果与日本古植物群落演替得出的结论相一致.  相似文献   

Reciprocal sound transmission measurement of mean current and temperature variations in the central part (Aki-nada) of the Seto Inland Sea,Japan     

Yudi Adityawarman  Arata Kaneko  Koji Nakano  Naokazu Taniguchi  Katsuaki Komai  Xinyu Guo  Noriaki Gohda 《Journal of Oceanography》2011,67(2):173-182

A 30 km-range reciprocal sound transmission experiment was carried out on the line connecting Honshu and Shikoku (the first and fourth biggest main Japanese islands, respectively) in the central part (Aki-nada) of the Seto Inland Sea, Japan, during March–May 2010 to measure the mean current and temperature variations over the sea. The range-averaged current along the sound transmission line was estimated to have a mean and standard deviation of (3.8–4.4) ± (1.7–1.8) cm/s after converting the travel time difference data into currents, including a fortnightly tidal variation in the range of ±30 cm/s. The positive mean current implies slow water movement from the west to east through Aki-nada. The range-averaged speed of sound was estimated by converting from the mean travel time or one-way travel time into the speed of sound, and further converted into temperature for fixed values of salinity and depth, according to the standard speed of sound formula. Besides the precise measurement (to an accuracy of 0.01°C) of semidiurnal and diurnal tidal variations and seasonal warming, the temperature data showed periodic variations with periods of 7.0 and 21.1 days that had never been observed in Aki-nada before. This study suggests that reciprocal sound transmission is a powerful technique for the long-term accurate measurement of mean current and temperature variations in coastal and inland seas.  相似文献   

Mapping of tidal current and associated nonlinear currents in the Xiangshan Bay by coastal acoustic tomography     

Chen  Minmo  Zhu  Ze-Nan  Zhang  Chuanzheng  Zhu  Xiao-Hua  Zhang  Zhensheng  Wang  Min  Zheng  Hua  Zhang  Xinyu  Chen  Juntian  He  Zongcai  Dai  Longhao  Kaneko  Arata 《Ocean Dynamics》2021,71(8):811-821

Ocean Dynamics - Herein, tidal current and associated nonlinear currents were measured using nine coastal acoustic tomography (CAT) systems surrounding the tomography domain in Xiangshan Bay from...  相似文献   

Optimum design of the ocean acoustic tomography system for the Sea of Japan     

Arata Kaneko  Gang Yuan  Noriaki Gohda  Iwao Nakano 《Journal of Oceanography》1994,50(3):281-293

An ocean acoustic tomography system covering the region of 800×1000 km with the spatial resolution of eddy-resolving scales has been designed on the basis of computer experiments using the hydrographic data collected in the Sea of Japan. The optimum number of acoustic sources required for 20 acoustic receivers was estimated as 13 by changing the source number. The spatial resolution for the optimum system was 41 km smaller than the dominant size of meso-scale eddies in the Sea of Japan. The effect of travel-time errors on tomographic maps is also quantified.  相似文献   

Monitoring Surface Velocity from Repeated ADCP Observations and Satellite Altimetry   总被引：1，自引：1，他引：1  

Kaoru Ichikawa  Noriaki Gohda  Masazumi Arai  Arata Kaneko 《Journal of Oceanography》2004,60(2):365-374

A method has been developed to monitor the surface velocity field by combining repeated acoustic Doppler current profiler (ADCP) observations and satellite altimetry data. The geostrophic velocity anomaly is calculated from the sea surface height anomaly field estimated from the altimetry data by an optimal interpolation. It has been confirmed that this accurately observes the smoothed velocity anomaly field when the interpolation scales are set according to the spatio-temporal sampling pattern of the altimeter used. The velocity anomaly obtained from the altimetry data is subtracted from the repeated ADCP observations to estimate temporal mean velocity along the ship tracks. Regularly sampled, nine-year time series of surface velocity can then be obtained by adding the computed mean velocity and the altimetry anomaly components. This clearly illustrates surface velocity fluctuations such as the movement of the Kuroshio axis due to its meandering and an increase of the interannual variability of the Subtropical Countercurrent toward its downstream region. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Towed ADCP fish with Depth and Roll controllable wings and its application to the Kuroshio observation     

Arata Kaneko  Noriaki Gohda  Wataru Koterayama  Masahiko Nakamura  Shinjiro Mizuno  Hirohito Furukawa 《Journal of Oceanography》1993,49(4):383-395

An intelligent ADCP (Acoustic Doppler Current Profiler) fish, called DRAKE (Depth and Roll Adjustable Kite for Energy flux measurements) was developed with the controllable wings which can adjust the submerging depth of the fish and stabilize its roll motion. The Kuroshio west of Okinawa was measured in a roundtrip course on the same traverse line by the ADCP fish. The forward survey obtained the maximum submerging depth of 208 m at a fish operation speed of 2.9 ms^–1. The maximum fish speed of 5.4 ms^–1 was achieved at a submerging depth of 48 m in the return survey. The data in the overlapped area of data acquisition between depths 212 and 276 m were used to examine the accuracy of velocity measurement for the towed ADCP system. The summation of both survey data made it possible to estimate a sectional velocity structure and transport of the upper 600 m corresponding roughly to the whole section of the Kuroshio in this region.  相似文献   

Computer Simulation of Coastal Acoustic Tomography by a Two-Dimensional Vortex Model     

Jae-Hun Park  Arata Kaneko 《Journal of Oceanography》2001,57(5):593-602

Computer simulation of coastal acoustic tomography with four, five, seven and nine stations was applied to two-dimensional vortex fields of horizontal domain 5 km × 5 km. Travel time data obtained in reciprocal directions between all pairs of acoustic stations were analyzed to reconstruct the vortex fields by the stochastic inverse method, reduced to the damped least squares method. The weighting factor appearing in the inverse analysis was determined by applying the L-curve method, in which a point making both the size of estimated error ‖y - Ex‖ and solution ‖x‖ as small as possible in a balance is specified as an optimum. The performance of this method was examined using two-dimensional vortex models which have different wavenumber spectra and adding the random error of different levels to the travel time difference data y. This study suggests that in the selection of the optimal weighting factor the horizontal section of the simulated tidal vortex fields can be well reconstructed by the coastal acoustic tomography system composed of five to seven acoustic stations located in the periphery of the vortex fields. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献