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21.
Radiocarbon dates of fifteen samples representing raised shorelines on various islands of the tectonically mobile region of eastern Indonesia suggest rates of tectonic uplift ranging up to 12.5 mm/year. Low rates of 0.35–1.2 mm/year are from Biak Island and are averages for the last 31,000–36,000 years. The low rates may be explained to indicate subsidence alternating with uplift, both of which occurring under influence of the large Irian fault zone that passes to the immediate south of the island. Very young elevated strandlines (250 years BP) indicate rates of uplift between 8 and 12.5 mm/year which seem to demonstrate the episodic character of vertical diastrophic movements. Intermediate rates of uplift are in the order of 5 mm/year and may represent averages for eastern Indonesia. 相似文献
22.
Abstract. Simulation experiments with a one-dimensional static model for formation of methane hydrate are used to demonstrate models of hydrate occurrence and its generation mechanism for two end-member cases. The simulation results compare well with experimental data for two natural examples (the Nankai Trough and the Blake Ridge).
At the MITI Nankai Trough wells, the hydrate occurrence is characterized by strongly hydrated sediments developing just above the BGHS. Such occurrence can be reproduced well by simulation in which the end-member case of upward advective fluid flow from below the BGHS is set. The strongly hydrated sediments is formed by oversaturated solution with free gas which directly enters the BGHS by the upward advective fluid flow. The recycling of dissociated methane of preexisting hydrate also contributes to the increase of hydrate saturation.
At the Site 997 in the Blake Ridge area, the hydrate occurrence is characterized by thick zone with poorly hydrated sediments and no hydrate zone developing above the hydrate zone. Such occurrence can be reproduced well by simulation in which the end-member case of in-situ biogenic production of methane in the sediment of methane hydrate zone is set. The distribution pattern of hydrate saturation is basically controlled by that of TOC. However, the hydrate concentration near the bottom of the hydrate zone is increased by the effect of recycling of dissociated methane of pre-existing hydrate. No hydrate zone expresses the geologic time needed until the local concentration of methane exceeds the solubility by gradual accumulation of in-situ biogenic methane with burial. 相似文献
At the MITI Nankai Trough wells, the hydrate occurrence is characterized by strongly hydrated sediments developing just above the BGHS. Such occurrence can be reproduced well by simulation in which the end-member case of upward advective fluid flow from below the BGHS is set. The strongly hydrated sediments is formed by oversaturated solution with free gas which directly enters the BGHS by the upward advective fluid flow. The recycling of dissociated methane of preexisting hydrate also contributes to the increase of hydrate saturation.
At the Site 997 in the Blake Ridge area, the hydrate occurrence is characterized by thick zone with poorly hydrated sediments and no hydrate zone developing above the hydrate zone. Such occurrence can be reproduced well by simulation in which the end-member case of in-situ biogenic production of methane in the sediment of methane hydrate zone is set. The distribution pattern of hydrate saturation is basically controlled by that of TOC. However, the hydrate concentration near the bottom of the hydrate zone is increased by the effect of recycling of dissociated methane of pre-existing hydrate. No hydrate zone expresses the geologic time needed until the local concentration of methane exceeds the solubility by gradual accumulation of in-situ biogenic methane with burial. 相似文献
23.
During Tropical Ocean and Global Atmosphere (TOGA)/Coupled Ocean and Atmosphere Research Experiment (COARE) Intensive Observing Period (IOP), upward-looking acoustic Doppler current profilers (ADCP) and current meters were moored at two equatorial sites (147°E and 154°E) and two off-equatorial sites (2°N and 2°S, 156°E) in the warm pool region of the western equatorial Pacific. Using current data obtained by these moorings, we have shown that there is a dominant signal with a period of about 2 days from the end of November to the middle of December in 1992, except at the equatorial site on 147°E (Ueki et al., 1998). The energy of this quasi-2-day signal for the meridional current is larger than that for the zonal one and the signal has a high coherence between two off-equatorial sites. In this paper, using band-passed time series of the meridional curerent, we investigated characters of the quasi-2-day signal and attempted to interpret this signal as an equatorially trapped wave. Complex empirical orthogonal function (CEOF) analysis reveals two different phase propagating features between the equatorial and off-equatorial site. One is an upward propagating signal, which is dominant near the surface at two off-equatorial sites, and the other is a downward propagating signal, which is dominant near 200 m at the equatorial site. If one interprets the quasi-2-day signal as an equatorially trapped wave, it is suggested that it cannot be explained as a single wave but can be described as the superimposition of several wave signals. The main part of these signals consists of two signals, one caused by a meteorological forcing and another by another factor in the ocean field. 相似文献
24.
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
25.
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
26.
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
27.
A Late Holocene geomagnetic secular variation record from Erhai Lake, southwest China 总被引：1，自引：0，他引：1
Masayuki Hyodo Arata Yoshihara Kenji Kashiwaya Takashi Okimura Toshiyuki Masuzawa Ryotaro Nomura Shingo Tanaka Tang Bang Xing Liu Su Qing & Liu Shi Jian 《Geophysical Journal International》1999,136(3):784-790
A secular variation record of the geomagnetic field direction for the last 6.5 kyr has been obtained from the magnetization of sediment cores from Erhai Lake, southwest China. In order to make a comparison with this record, secular variation in east-central China was investigated by combining available magnetic field data from historical records and archaeomagnetic measurements since about 350 bc . The secular variation in Erhai Lake shows features consistent with the combined record, except for the oldest three observed declination swings in Sian from 720 to 900 ad . Many features of declination and inclination in China also occur in Japan. From 500 to 1000 ad , declination was westerly ranging from about −20° to −5° in Erhai Lake, east-central China, and Japan. 相似文献
28.
Recent progress in studies of the South China Sea circulation 总被引：12，自引：1，他引：12
The South China Sea (SCS) is a semi-enclosed marginal sea with deep a basin. The SCS is located at low latitudes, where the
ocean circulations are driven principally by the Asia-Australia monsoon. Ocean circulation in the SCS is very complex and
plays an important role in both the marine environment and climate variability. Due to the monsoon-mountain interactions the
seasonal spatial pattern of the sea surface wind stress curl is very specific. These distinct patterns induce different basin-scale
circulation and gyre in summer and winter, respectively. The intensified western boundary currents associated with the cyclonic
and anticyclonic gyres in the SCS play important roles in the sea surface temperature variability of the basin. The mesoscale
eddies in the SCS are rather active and their formation mechanisms have been described in recent studies. The water exchange
through the Luzon Strait and other straits could give rise to the relation between the Pacific and the SCS. This paper reviews
the research results mentioned above. 相似文献
29.
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
30.
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