Modern sediment characteristics and accumulation rates from the delta front to prodelta of the Yellow River (Huanghe)   总被引：2，自引：0，他引：2  

Liangyong Zhou  Jian Liu  Yoshiki Saito  Maosheng Gao  Shaobo Diao  Jiandong Qiu  Shaofeng Pei 《Geo-Marine Letters》2016,36(4):247-258

Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (¹³⁷Cs, ²¹⁰Pb and ⁷Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river’s course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5–18.6 cm year^–1 on the delta front slope, 2 cm year^–1 at the toe of the slope, and 1–2 cm year^–1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on ⁷Be distribution, the shorter-term deposition rate was at least 20 cm year^–1 in the delta front.  相似文献   

The post flare loops observed at the total eclipse of February 16, 1980     

Yoichiro Hanaoka  Hiroki Kurokawa  Sumisaburo Saito 《Solar physics》1986,105(1):133-148

A post flare loop system was observed on the west limb at the total solar eclipse of February 16, 1980 in Kenya. Analyzing the monochromatic images and the flash spectra, we obtained the following results: (1) the lower part of the post flare loop system is characterized mainly by distinct cool loops of H and Fe x 6374. Fe x 6374 emitting plasma (T _e = 1.0 × 10⁶ K) is highly concentrated in the loops. The 6374 loops are broader in diameter and located very close to but a little higher than the corresponding H loops. The electron densities of the dense part in H and Fe x 6374 loops are 10¹¹ cm^-3 and 6 × 10⁹cm^-3, respectively; (2) the Ca xv emitting region (3.5 × 10⁶ K) is confined to the upper part of the post flare loops. The electron density of this hot region is estimated as 8 × 10⁹ cm^-3 from the Ca xv line intensity ratio, I(5694)I(5445). These observational results led us to construct an empirical model of the post flare loop system which is consistent with the reconnection model of Kopp and Pneuman (1976).Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 267.  相似文献   

Characterization of humic and fulvic acids isolated from marine sediments of Sagami and Suruga Bays with C-13 and proton nuclear magnetic resonance     

Yoshiji Saito  Shigeo Hayano 《Journal of Oceanography》1981,36(6):286-292

The C-13 and proton NMR spectra of marine humic and fulvic acids isolated from sediments of Sagami and Suruga Bays and Aldrich humic acid were obtained using pulse Fourier transform mode. The C-13 and proton NMR spectra, which clarified the differences in chemical characteristics among the various humic substances, showed that the marine humic acids had more aliphatic and less aromatic character than the Aldrich humic acid, and the marine fulvic acids had polysaccharide-like character. The C-13 NMR spectra of the marine humic substances, in particular, had many relatively well-resolved peaks with significant intensities, indicating the presence of variously bonded carbon atoms in them.  相似文献   

Tidal Mixing in the Kuril Straits and Its Impact on Ventilation in the North Pacific Ocean     

Tomohiro Nakamura  Takahiro Toyoda  Yoichi Ishikawa  Toshiyuki Awaji 《Journal of Oceanography》2004,60(2):411-423

A numerical study using a 3-D nonhydrostatic model has been applied to baroclinic processes generated by the K ₁ tidal flow in and around the Kuril Straits. The result shows that large-amplitude unsteady lee waves are generated and cause intense diapycnal mixing all along the Kuril Island Chain to levels of a maximum diapycnal diffusivity exceeding 10³ cm²s⁻¹. Significant water transformation by the vigorous mixing in shallow regions produces the distinct density and potential vorticity (PV) fronts along the Island Chain. The pinched-off eddies that arise and move away from the fronts have the ability to transport a large amount of mixed water (∼14 Sv) to the offshore regions, roughly half being directed to the North Pacific. These features are consistent with recent satellite imagery and in-situ observations, suggesting that diapycnal mixing within the vicinity of the Kuril Islands has a greater impact than was previously supposed on the Okhotsk Sea and the North Pacific. To examine this influence of tidal processes at the Kurils on circulations in the neighboring two basins, another numerical experiment was conducted using an ocean general circulation model with inclusion of tidal mixing along the islands, which gives a better representation of the Okhotsk Sea Mode Water than in the case without the tidal mixing. This is mainly attributed to the added effect of a significant upward salt flux into the surface layer due to tidal mixing in the Kuril Straits, which is subsequently transported to the interior region of the Okhotsk Sea. With a saline flux into the surface layer, cooling in winter in the northern part of the Okhotsk Sea can produce heavier water and thus enhance subduction, which is capable of reproducing a realistic Okhotsk Sea Mode Water. The associated low PV flux from the Kuril Straits to the open North Pacific excites the 2nd baroclinic-mode Kelvin and Rossby waves in addition to the 1st mode. Interestingly, the meridional overturning in the North Pacific is strengthened as a result of the dynamical adjustment caused by these waves, leading to a more realistic reproduction of the North Pacific Intermediate Water (NPIW) than in the case without tidal mixing. Accordingly, the joint effect of tidally-induced transport and transformation dominating in the Kuril Straits and subsequent eddy-transport is considered to play an important role in the ventilation of both the Okhotsk Sea and the North Pacific Ocean. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The stratigraphic architecture of the central Sunda Shelf (SE Asia) recorded by shallow-seismic surveying   总被引：7，自引：0，他引：7  

Till J. Hanebuth  Karl Stattegger  Yoshiki Saito 《Geo-Marine Letters》2002,22(2):86-94

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Application of Sensitivity Analysis Using an Adjoint Model for Short-Range Forecasts of the Kuroshio Path South of Japan     

Yoichi Ishikawa  Toshiyuki Awaji  Nobumasa Komori  Takahiro Toyoda 《Journal of Oceanography》2004,60(2):293-301

A sensitivity experiment has been performed by assimilating altimetric data into a 1.5-layer primitive equation model as a first attempt to examine the impact of initialization on forecasts of the Kuroshio path variability south of Japan. By exploiting the advantage of an adjoint model, our approach clearly shows that a small meander off Shikoku Island has a large impact on the prediction of meander growth in the Kuroshio region. Further, the strengthening of the Kuroshio current and its recirculation clearly becomes an important factor in the development of the meander. These results demonstrate the effectiveness of our assimilation approach in identifying efficient initialization schemes on numerical forecasting of the Kuroshio south of Japan and should help in the construction of an effective observing system for improving the forecasting. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The Kyucho in the Bungo Channel,Japan —Periodic intrusion of oceanic warm water     

Hidetaka Takeoka  Hideki Akiyama  Takahiro Kikuchi 《Journal of Oceanography》1993,49(4):369-382

Kyucho is a sudden and swift current which is usually accompanied by rise of water temperature. Several features of the Kyucho in the Bungo Channel, Japan, are presented through field observations. The Kyucho in the Bungo Channel is an intrusion of warm water from the Pacific Ocean into the eastern half of the Bungo Channel, being driven gravitationally and advancing along the eastern coast of the channel. The Kyucho occurs usually in summer and seldom occurs in winter. It occurs at neap tides showing the prominent spring-neap periodicity. The modulation of the vertical mixing intensity associated with the variations of tidal current, wind and surface heating etc. is supposed to be a main cause of springneap and seasonal periodicities.  相似文献   

Distribution of oxygen-containing functional groups and elements in humic acids from marine sediments     

Yoshiji Saito  Shigeo Hayano 《Journal of Oceanography》1980,36(1):59-67

The elemental composition and oxygen-containing functional groups contents in the marine humic acids from the five sediment samples from Sagami Bay and Suruga Bay were determined. Kumada's method of classification of soil humic acids was applied to the marine humic acids. The carbon, nitrogen, hydrogen, oxygen and sulfur contents of the marine humic acids were, on average, 52.96, 5.12, 5.79, 34.99 and 1.13%, respectively, without wide variation. In comparison with terrestrial humic acids, the marine ones had relatively lower carbon content and higher hydrogen and nitrogen contents. It is suggested that the marine humic acids have more aliphatic and less aromatic character, as expected from their possible origins, e.g., phytoplankton. The total acidity, carboxyl, phenolic and alcoholic hydroxyl, carbonyl and methoxyl group contents in the marine humic acids were, on average, 5.80, 3.27, 2.53, 2.53, 3.09 and 0.41 milliequivalents per gram of dry ash-free humic acid (me g^–1), respectively. From quantitative data on the elemental composition and functional groups of the average marine humic acid, its empirical formula was calculated to be C₁₀₇H₁₃₈O₂₀(COOH)₉(OH)₇ ^phenolic (OH)₇ ^alcoholic (CO)₉(OCH)₃N₁₀S. The marine humic acids were similar to the so-called B type of soil humic acids with regard to the distribution of functional groups and spectroscopic properties.  相似文献   

Spatial Variability of Living Coccolithophore Distribution in the Western Subarctic Pacific and Western Bering Sea   总被引：1，自引：0，他引：1  

Hiroshi Hattori  Makoto Koike  Kenichi Tachikawa  Hiroaki Saito  Kazuya Nagasawa 《Journal of Oceanography》2004,60(2):505-515

Vertical distributions of coccolithophores were observed in the depth range 0–50 m in the western subarctic Pacific and western Bering Sea in summer, 1997. Thirty-five species of coccolithophores were collected. Overall, Emiliania huxleyi var. huxleyi was the most abundant taxon, accounting for 82.8% of all coccolithophores, although it was less abundant in the western Bering Sea. Maximum abundance of this species was found in an area south of 41°N and east of 175°E (Transition Zone) reaching >10,000 cells L⁻¹ in the water column. In addition to this species, Coccolithus pelagicus f. pelagicus, which accounted for 4.2% of the assemblage, was representative of the coccolithophore standing crop in the western part of the subarctic Pacific. Coccolithus pelagicus f. hyalinus was relatively abundant in the Bering Sea, accounting for 2.6% of the assemblage. Coccolithophore standing crops in the top 50 m were high south of 41°N (>241 × 10⁶ cells m⁻²) and east of 170°E (542 × 10⁶ cells m⁻²) where temperatures were higher than 12°C and salinities were greater than 34.2. The lowest standing crop was observed in the Bering Sea and Oyashio areas where temperatures were lower than 6–10°C and salinities were less than 33.0. From the coccolithophore volumes, the calcite stocks in the Transition, Subarctic, and the Bering Sea regions were estimated to be 73.0, 9.7, and 6.9 mg m⁻², respectively, corresponding to calcite fluxes of 3.6, 0.5, and 0.3 mg m⁻²d⁻¹ using Stoke's Law. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Mesozooplankton responses to iron-fertilization in the western subarctic Pacific (SEEDS2001)   总被引：1，自引：1，他引：1  

Atsushi Tsuda  Hiroaki Saito  Jun Nishioka  Tsuneo Ono 《Progress in Oceanography》2005,64(2-4):237

A mesoscale iron-fertilization experiment was carried out in the western subarctic Pacific during summer 2001. The iron-patch was traced for 14 days after the fertilization, and the abundance and behavior of mesozooplankton were compared with those outside of the patch. The phytoplankton biomass in the patch rapidly increased to over 15 times the initial level by the later half of the observation period, and was composed of large-sized (>10 mm), centric diatoms. Dominant zooplankton species in the upper 200-m depth were large copepods: Neocalanus plumchrus, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica. Mesozoplankton biomass as well as species composition did not change significantly in the patch over the observation period. Furthermore, no changes of vertical distribution or diel vertical migration were observed for any species or stages of mesozooplankton throughout the observation period. However, the abundance of the first copepodite stages of N. plumchrus and E. bungii increased several fold in the patch after the diatom bloom formation compared to the densities outside the patch. The increases of both species are considered to be due to lowered mortality during the egg and nauplius stages. Spawning of N. plumchrus takes place at depth using lipid storage, while spawning of E. bungii takes place in the surface layer supported by grazing. These facts suggest that the relative importance of nauplii in the diets of the large copepods was decreased in the patch by the diatom bloom. Gut-pigment contents of dominant copepods in the patch increased 4–18 times, and the maximum values were observed during the bloom peak. However, the grazing impact on phytoplankton was low throughout the experiment, especially during the bloom period (<6% of the primary production).  相似文献