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排序方式: 共有710条查询结果,搜索用时 15 毫秒
541.
Takashi Ninomiya Shoichi Shimoyama Koichiro Watanabe Kenji Horie Daniel J. Dunkley Kazuyuki Shiraishi 《Island Arc》2014,23(3):206-220
The Taishu Group, a marine formation with a thickness of >5400 m, crops out on Tsushima Island, located in the southwestern Japan Sea. The group, which is generally regarded as early Eocene to early Miocene in age, provides important information about the tectonic setting of the Japan Sea. In this study, we present new SHRIMP U–Pb dates for igneous zircons from the Kunehama Tuff, which is in the basal part of the Taishu Group, and the Oobaura Tuff, which is in the uppermost part of the group. Results show that the Taishu Group was deposited rapidly, during the short interval of 17.9–15.9 Ma (early–middle Miocene), and is equivalent to other early–middle Miocene strata found in the Japan Sea region. Our results provide new constraints on the geological history of the Japan Sea and its islands. 相似文献
542.
Gleb Panteleev Max Yaremchuk Vladimir Luchin Dmitri Nechaev Takashi Kukuchi 《Journal of Oceanography》2012,68(4):485-496
Sea surface height anomalies observed by satellites in 1992–2010 are combined with monthly climatologies of temperature and salinity to estimate circulation in the southern Bering Sea. The estimated surface and deep currents are consistent with independent velocity observations by surface drifters and Argo floats parked at 1,000?m. Analysis reveals 1–3-Sv interannual transport variations of the major currents with typical intra-annual variability of 3–7?Sv. On the seasonal scale, the Alaskan Stream transport is well correlated with the Kamchatka (0.81), Near Strait (0.53) and the Bering Slope (0.37) currents. Lagged correlations reveal a gradual increase of the time the lags between the transports of the Alaskan Stream, the Bering Slope Current and the Kamchatka Current, supporting the concept that the Bering Sea basin is ventilated by the waters carried by the Alaskan Stream south of the Aleutian Arc and by the flow through the Near Strait. Correlations of the Bering Sea currents with the Bering Strait transport are dominated by the seasonal cycle. On the interannual time scale, significant negative correlations are diagnosed between the Near Strait transport and the Bering Slope and Alaskan Stream currents. Substantial correlations are also diagnosed between the eddy kinetic energy and Pacific Decadal Oscillation. 相似文献
543.
544.
An oxygen minimum zone (OMZ) currently exists at intermediate water depths on the northern Japanese margin in the northwestern Pacific. The OMZ results largely from a combination of high surface–water productivity and poor ventilation of intermediate waters. We investigated the late Quaternary history (last 27 kyr) of the intensity of this OMZ using changes in benthic foraminiferal carbon isotopes and assemblages in a sediment core taken on the continental slope off Shimokita Peninsula, northern Japan, at a water depth of 975 m. The core was located well within the region of the present-day OMZ and high surface–water productivity. The benthic foraminiferal δ13C values, which indicate millennial-scale fluctuations of nutrient contents at the sediment–water interface, were 0.48‰ lower during the last glacial maximum (LGM) than during the late Holocene. These results do not indicate the formation of glacial intermediate waters of subarctic Pacific origin, but rather the large contribution of high-nutrient water masses such as the Antarctic Intermediate Water, implying that the regional circulation pattern during the LGM was similar to that of modern times. Benthic foraminiferal assemblages underwent major changes in response to changes in dissolved oxygen concentrations in ocean floor sediments. The lowest oxygen and highest nutrient conditions, marked by dysoxic taxa and negative values of benthic foraminiferal δ13C, occurred during the Bølling/Allerød (B/A) and Pre-Boreal warming events. Dysoxic conditions in this region during these intervals were possibly caused by high surface–water productivity at times of reduced intermediate–water ventilation in the northwestern Pacific. The benthic assemblages show dysoxic events on approx. 100- to 200-year cycles during the B/A, reflecting centennial-scale productivity changes related to freshwater cycles and surface–water circulation in the North Pacific. 相似文献
545.
Motohiko Kashima Shin-Ichi Ito Kaoru Ichikawa Shiro Imawaki Shin-Ichiro Umatani Hiroshi Uchida Takashi Setou 《Journal of Oceanography》2009,65(1):73-80
A quasiperiodic variation of 100–110 days in the Kuroshio path off Cape Ashizuri, resulting from the passage of small meanders,
was detected by observation with moored current meters during 1993–1995. TOPEX/POSEIDON altimeter data covering 9 years showed
that the quasiperiodic variation period was not persistent and modulated twice, with a ∼110-day period from mid-1993 to late
1996, a ∼150-day period from late 1996 to mid-1999, and a ∼110-day period from mid-1999 to late 2001. The quasiperiodic variations
of the Kuroshio path migration were contemporaneous with the quasiperiodic arrivals of mesoscale eddies from the east along
27–32°N over the same ∼110- and ∼150-day period quasiperiodic variations. The periodic arrivals of the eddies configure the
periodic variations of the Kuroshio path and its inter-annual modulation. 相似文献
546.
Role of environment and hydrography in determining the picoplankton community structure of Sagami Bay,Japan 总被引:1,自引:0,他引:1
Smita Mitbavkar Toshiro Saino Naho Horimoto Jota Kanda Takashi Ishimaru 《Journal of Oceanography》2009,65(2):195-208
Seasonal variations in the picoplankton community were investigated from June 2002 to March 2004 within the photic zone of
Sagami Bay, Japan. The study area was mostly dominated by coastal waters during the warm period (mixed layer water temperature
≥ 18°C). During the cold period (mixed layer water temperature ≤ 18°C), the water mass was characterized by low temperature
and high saline waters indicative of the North Pacific Subtropical Mode Water (NPSTMW). Occasionally, a third type of water
mass characterized by high temperature and low saline properties was observed, which could be evidence of the intrusion of
warm Kuroshio waters. Synechococcus was the dominant picophytoplankton (5−28 × 1011 cells m−2) followed by Prochlorococcus (1−5 × 1011 cells m−2) and picoeukaryotes during the warm period. Heterotrophic bacteria dominated the picoplankton community throughout the year,
especially in the warm period. During the Kuroshio Current advection, cyanobacterial abundance was high whereas that of picoeukaryotes
and heterotrophic bacteria was low. During the cold period, homogeneously distributed, lower picophytoplankton cell densities
were observed. The dominance of Synechococcus in the warm period reflects the importance of high temperature, low salinity and high Photosynthetically Active Radiation
(PAR) on its distribution. Cyanobacterial and heterotrophic bacterial abundance showed a positive correlation with temperature.
Prochlorococcus and picoeukaryotes showed a positive correlation with nutrients. Picoeukaryotes were the major contributors to the picophytoplankton
carbon biomass. The annual picophytoplankton contribution to the photosynthetic biomass was 32 ± 4%. These observations suggest
that the environmental conditions, combined with the seasonal variability in the source of the water mass, determines the
community structure of picoplankton, which contributes substantially to the phytoplankton biomass and can play a very important
role in the food web dynamics of Sagami Bay. 相似文献
547.
Water mass variability in the western North Pacific detected in a 15-year eddy resolving ocean reanalysis 总被引:2,自引:0,他引:2
548.
Research and development of the New Generation Sea Surface Temperature for Open Ccean (NGSST-O) product and its demonstration operation 总被引:1,自引:0,他引:1
Futoki Sakaida Hiroshi Kawamura Shin Takahashi Teruhisa Shimada Yoshimi Kawai Kohtaro Hosoda Lei Guan 《Journal of Oceanography》2009,65(6):859-870
Real-time generation and distribution of the New Generation Sea Surface Temperature for Open Ocean (NGSST-O) product began
in September 2003 as a demonstration operation of the Global Ocean Data Assimilation Experiment (GODAE) High-Resolution Sea
Surface Temperature Pilot Project. Satellite sea surface temperature (SST) observations from infrared radiometers (AVHRR,
MODIS) and a microwave radiometer (AMSR-E) are objectively merged to generate the NGSST-O product, which is a quality-controlled,
cloud-free, high-spatial-resolution (0.05° gridded), wide-coverage (13–63° N, 116–166° E), daily SST digital map. The NGSST-O
demonstration operation system has been developed in cooperation with the Japanese Space Agency (JAXA) and has produced six
years of continuous data without gaps. Comparison to in situ SSTs measured by drifting buoys indicates that the root mean-square error of NGSST-O has been kept at approximately 0.9°C. 相似文献
549.
To assess differences in fish assemblage structures among microhabitats within the surf zone of an exposed sandy beach, three microhabitats (onshore current, rip current, and river adjacent sites) were sampled at Sanrimatsubara Beach, western Japan, in May, August, and November 2002 and 2003. Although several physical variables (e.g. wave height, current speed, turbidity, salinity, and sand particle size) and major prey abundances (calanoid copepods and mysids) differed among the sites, no significant differences were apparent in the numbers of fish species and individuals among the sites in any month in either year. In addition, species and individual numbers of two dominant feeding groups (zooplankton feeders, and epiphytic and benthic crustacean feeders) did not show any significant responses to among-site differences in prey abundance. Cluster and ordination analysis confirmed the similarity in fish species composition among the three sites. These results indicated that the surf zone fish assemblage structures were similar among the microhabitats in spite of there being microhabitat-related differences in abiotic and biotic environments. 相似文献
550.
Diurnal sea surface temperature variation and its impact on the atmosphere and ocean: A review 总被引:9,自引:1,他引:9
The importance of the diurnal variability of sea surface temperature (SST) on air-sea interaction is now being increasingly
recognized. This review synthesizes knowledge of the diurnal SST variation, mainly paying attention to its impact on the atmosphere
or the ocean. Diurnal SST warming becomes evident when the surface wind is weak and insolation is strong. Recent observations
using satellite data and advanced instruments have revealed that a large diurnal SST rise occurs over wide areas in a specific
season, and in an extreme case the diurnal amplitude of SST exceeds 5 K. The large diurnal SST rise can lead to an increase
in net surface heat flux from the ocean of 50–60 Wm−2 in the daytime. The temporal mean of the increase exceeds 10 Wm−2, which will be non-negligible for the atmosphere. A few numerical experiments have indicated that the diurnal SST variation
can modify atmospheric properties over the Pacific warm pool or a coastal sea, but the processes underlying the modification
have not yet been investigated in detail. Furthermore, it has been shown that the diurnal change of ocean mixing process near
the surface must be considered correctly in order to reproduce SST variations on an intraseasonal scale in a numerical model.
The variation of mixed-layer properties on the daily scale is nonlinearly related to the intraseasonal variability. The mixed-layer
deepening/shoaling process on the daily scale will also be related to biological and material circulation processes. 相似文献