Interstitial water chemistry in deep-sea sediments from the Japan Sea     

Masuzawa  Toshiyuki  Kitano  Yasushi 《Journal of Oceanography》1983,39(4):171-184

Vertical profiles of pH, Eh, and major and minor chemical constituents in interstitial waters have been studied in four piston cores from deep-sea basins of the Japan Sea. Sulfate concentration decreases remarkably with increasing depth in three cores, and hydrogen sulfide is observed in two cores although the overlying bottom water is highly aerated. Three types of interstitial waters are observed in the four cores: (1) alkalinity and manganese concentration increase gradually with increasing depth, and sulfate reduction is not appreciable, (2) alkalinity increases and sulfate concentration decreases remarkably, and hydrogen sulfide is not detected, and (3) alkalinity increases and sulfate concentration decreases remarkably, and hydrogen sulfide is observed. Factors controlling the chemical composition of interstitial waters are discussed.  相似文献   

Temporal variation in mass fluxes and the major components of sinking particles in Sagami Bay, off Japan     

Toshiyuki Masuzawa  Tie LiYun Duan  Mineko YamamotoYuriko Hibi  Takeshi NakatsukaHiroshi Kitazato  Yoshihisa Kato 《Progress in Oceanography》2003,57(1):59-75

Sinking particles were collected using time-series sediment traps deployed at 350 and 20 mab at Site SB (34° 58.5’N, 139° 20.9’E, 1544 m depth) near the center of Sagami Bay, off Japan with high time resolutions of 5-8 days (March 1997 to August 1998) and 3-4.5 days (March 1998 to August 1998), respectively. The major components (CaCO₃, OM, opal, and clay) of these sinking particles and surface bottom sediments were determined using a stepwise leaching method combined with gravimetry. Average total mass fluxes were 1480, 5560 and 3068 mg/m²/year at 350 mab, at 20 mab, and in the surface sediments, respectively, indicating an enhanced collection of sinking particles at 20 mab. Clay was the dominant component and biogenic components (opal+OM+CaCO₃) were dominated mainly by opal and secondly by OM. On average, opal and CaCO₃ contents decreased gradually as clay content increased with increasing depth from 350 mab-20 mab and in the surface sediments, indicating dissolution of opal and CaCO₃ through sinking, rebound, resuspension or sedimentation processes. Thirteen total mass flux peaks at 17--40-day intervals were observed at 350 mab during the period from March 1997 to August 1998 except for winter, while eight peaks were observed at 20 mab for the period from March 1998 to August 1998. Two types of total mass peaks can be distinguished: one with a clear increase in biogenic flux (opal+OM+CaCO₃) and little or no increase in clay flux and termed a bloom type (B-type), and the other with a clear increase in clay flux, little increase in biogenic flux and termed a resuspension type (R-type). Some R-type peaks, but not all, coincided with total mass flux peaks observed at the mouth of Tokyo Bay and suggested the possibility of the effect of particulate materials transported from Tokyo Bay to site SB. The enormously large peak observed at 20 mab in late May 1998 and that at 350 mab in early June 1998 were considered to be due to some physical perturbations from an earthquake swarm near site SB during the period from April to June 1998. The 17--40-day periodicity was associated clearly with the change in biogenic flux dominated by opal flux and is thought to reflect the periodicity of biological productivity dominated by diatoms in the euphotic zone of Sagami Bay.  相似文献   

Strong tidal currents observed near the bottom in the Suruga Trough,central Japan     

Masaji Matsuyama  Suguru Ohta  Toshiyuki Hibiya  Haruya Yamada 《Journal of Oceanography》1993,49(6):683-696

Current measurements carried out at the depth of 4 m above the sea bottom near the northern edge of the Suruga Trough in the early fall of 1985 indicated the existence of strong semidiurnal tidal currents, which were considered to be associated with internal tides. In order to examine the spatial structure of the bottom intensified tidal flow, more detailed current observations were carried out at three or four depths at two stations along the main axis of the Suruga Trough during about 70 days from August to October 1988. We obtained the following results: (1) the variations of the current velocity caused by the semidiurnal and diurnal internal tides are evident in all of the records, and the orientation of the major axis of each tidal ellipse nearly coincides with that of the main axis of the trough; (2) the semidiurnal internal tide is dominant over the diurnal internal tide at 4 m above the sea bottom at both stations; (3) at the northern station the semidiurnal internal tide is dominant over the diurnal internal tide, whereas they are nearly equal at the southern station except at 4 m above the sea bottom; (4) the biharmonic internal tides with 1/3 day and 1/4 day periods, are found near the sea bottom and the major axis of the tidal ellipse is perpendicular to the orientation of the main axis of the Suruga Trough.  相似文献   

Assessment of turbulence closure models for resonant inertial response in the oceanic mixed layer using a large eddy simulation model   总被引：1，自引：0，他引：1  

Naoki Furuichi  Toshiyuki Hibiya  Yoshihiro Niwa 《Journal of Oceanography》2012,68(2):285-294

Large eddy simulation (LES) of the resonant inertial response of the upper ocean to strong wind forcing is carried out; the results are used to evaluate the performance of each of the two second-order turbulence closure models presented by Mellor and Yamada (Rev Geophys Space Phys 20:851–875, 1982) (MY) and by Nakanishi and Niino (J Meteorol Soc Jpn 87:895–912, 2009) (NN). The major difference between MY and NN is in the formulation of the stability functions and the turbulent length scale, both strongly linked with turbulent fluxes; in particular, the turbulent length scale in NN, unlike that in MY, is allowed to decrease with increasing density stratification. We find that MY underestimates and NN overestimates the development of mixed layer features, for example, the strong entrainment at the base of the oceanic mixed layer and the accompanying decrease of sea surface temperature. Considering that the stability functions in NN perform better than those in MY in reproducing the vertical structure of turbulent heat flux, we slightly modify NN to find that the discrepancy between LES and NN can be reduced by more strongly restricting the turbulent length scale with increasing density stratification.  相似文献   

Numerical study of tide-induced mixing over rough bathymetry in the abyssal ocean     

Nobuyuki Iwamae  Toshiyuki Hibiya 《Journal of Oceanography》2012,68(1):195-203

Locally enhanced turbulent mixing over rough bottom bathymetry is one of the candidates that might make up for the lack of diapycnal diffusivity in maintaining the global overturning circulation. In the present study, using a two-dimensional vertical numerical model for the Brazil Basin, we numerically examine the intensity and vertical structure of tide-induced mixing over multi-beam bottom bathymetry via the comparison with those over somewhat smoothed bottom bathymetry. Note that even this smoothed bottom bathymetry is finer than in commonly used datasets. In comparison to the response over the smoothed bottom bathymetry, energy dissipation rates are enhanced within a few hundred meters over the multi-beam bottom bathymetry. In spite of several limitations of the two-dimensional vertical numerical model, the magnitude and vertical distribution of the calculated dissipation rates agree well with those from microstructure measurements. We find that tidal interaction with fine-scale (≤2 km) bottom bathymetry efficiently generates high wavenumber internal waves, which are subject to local energy dissipation and hence strongly control the abyssal mixing; the most important finding is that the intensity and vertical decay scale of abyssal mixing are in a trade-off relationship with each other, which is not taken into account in the existing parameterizations.  相似文献   

Horizontal and vertical distributions of <Superscript>137</Superscript>Cs in seabed sediments around the river mouth near Fukushima Daiichi Nuclear Power Plant     

Tadahiko Tsuruta  Hisaya Harada  Toshiharu Misonou  Toshiyuki Matsuoka  Yasuyuki Hodotsuka 《Journal of Oceanography》2017,73(5):547-558

Investigations including a bathymetric survey, sonic prospecting, and vibrocoring were performed to understand the horizontal and vertical distribution of ¹³⁷Cs in seabed sediments in shallow seas with depths less than 30 m near the Fukushima Daiichi Nuclear Power Plant. Especially, features of ¹³⁷Cs distributions in deeper sections of the seabed sediments were studied to evaluate the vertical heterogeneity of ¹³⁷Cs distribution in the seabed sediments in shallow seas. The distribution area of the seabed sediments was less than half of the investigation area, and the locations of the seabed sediments were divided into flat and terrace-like seafloors based on their topographical features. The thicknesses of the seabed sediment layers were mostly <2 m. The ¹³⁷Cs inventories in the seabed sediments varied from 13 ± 1 to 3,510 ± 26 kBq m^?2, and continuous distributions of ¹³⁷Cs at depths greater than 81 cm were observed. The ¹³⁷Cs distributions were not uniform; however, the ¹³⁷Cs inventories tended to be larger near the base of the steeper ascending slopes than in the terrace-like seafloors themselves. Based on the relationship between the ¹³⁷Cs inventories and mean shear stress, features of the seafloor topography were inferred to be significant control factors governing the horizontal and vertical distribution of ¹³⁷Cs in the seabed sediments. Rapid changes and multiple peaks in the vertical profile of the ¹³⁷Cs distributions suggest that they are related to pulse input caused by heavy-rain events. Change in the ¹³⁷Cs inventories with depth in this study are larger than those reported in previous studies, indicating earlier results of ¹³⁷Cs inventories per unit in seabed sediments in shallow seas, especially near the river mouth, which drains a radiologically highly-contaminated basin, were underestimated.  相似文献   

Phytoplankton community reorganization driven by eutrophication and warming in Lake Biwa   总被引：1，自引：0，他引：1  

Chih Hao Hsieh  Kanako Ishikawa  Yoichiro Sakai  Toshiyuki Ishikawa  Satoshi Ichise  Yoshimasa Yamamoto  Ting Chun Kuo  Ho Dong Park  Norio Yamamura  Michio Kumagai 《Aquatic Sciences - Research Across Boundaries》2010,72(4):467-483

We compiled and analyzed long-term data, including chemical, physical and phytoplankton community data, for the Lake Biwa ecosystem from 1962 to 2003. Analyses on environmental data indicate that Lake Biwa had experienced intensified eutrophication (according to total phosphorus concentration) in the late 1960s and returned to a less eutrophic status around 1985, and then exhibited rapid warming and thus increased water column stability since 1990. Total phytoplankton cell volume largely followed the trend of total phosphorus concentration, albeit short-term fluctuations existed. However, phytoplankton community shifted dramatically in response to those changes of environmental states. These shifts were cause by changes in trophic status driven by phosphorus loadings and physical properties in the water column driven by warming. Moreover, most phytoplankton species did not show a strong linear correlation with environmental variables, suggesting nonlinear transitions among different states.  相似文献   

Cover Image          下载免费PDF全文

Jan‐Hendrik May  He‐Qing Huang  Toshiyuki Fujioka  David Fink  Alexandru Codilean  Guo‐An Yu  Yuanxu Ma  Gerwin Wulf  Jing Gu 《地球表面变化过程与地形》2018,43(3):i-i

  相似文献   

Production of the Blood Pressure Lowing Peptides from Brown Alga ( Undaria pinnatifida )     

Sato Minoru  Oba Takashi  Hosokawa Takao  Yamaguchi Toshiyasu  Nakano Toshiki  Saito Tadao  Muramoto Koji  Kahara Takashi  Funayama Katsura  Kobayashi Akio  Nakano Takahisa 《中国海洋大学学报(英文版)》2005,4(3)

1 IntroductionIncreased blood pressure appears to be one of theprimary risk factors of circulatory organ diseases suchas encepharo-apoplexy, encepharo-infarction and cardi-ac infraction. Angiotensin-I-converting enzyme (ACE)plays an important role in the rennin-angiotensin sys-tem by regulating blood pressure. Antihypertensivedrugs such as captopril and enalapril are potent ACEinhibitors (Ondetti et al., 1977). Recently, severalinhibitory peptides derived from food proteins havebeen isolat…  相似文献   

Consistency and fidelity of Indonesian-throughflow total volume transport estimated by 14 ocean data assimilation products     

Tong Lee  Toshiyuki Awaji  Magdalena Balmaseda  Nicolas Ferry  Yosuke Fujii  Ichiro Fukumori  Benjamin Giese  Patrick Heimbach  Armin Köhl  Simona Masina  Elisabeth Remy  Anthony Rosati  Michael Schodlok  Detlef Stammer  Anthony Weaver 《Dynamics of Atmospheres and Oceans》2010

Monthly averaged total volume transport of the Indonesian throughflow (ITF) estimated by 14 global ocean data assimilation (ODA) products that are decade to multi-decade long are compared among themselves and with observations from the INSTANT Program (2004–2006). The main goals of the comparisons are to examine the consistency and evaluate the skill of different ODA products in simulating ITF transport. The ensemble averaged, time-mean value of ODA estimates is 13.6 Sv (1 Sv = 10⁶ m³/s) for the common 1993–2001 period and 13.9 Sv for the 2004–2006 INSTANT Program period. These values are close to the 15-Sv estimate derived from INSTANT observations. All but one ODA time-mean estimate fall within the range of uncertainty of the INSTANT estimate. In terms of temporal variability, the scatter among different ODA estimates averaged over time is 1.7 Sv, which is substantially smaller than the magnitude of the temporal variability simulated by the ODA systems. Therefore, the overall “signal-to-noise” ratio for the ensemble estimates is larger than one. The best consistency among the products occurs on seasonal-to-interannual time scales, with generally stronger (weaker) ITF during boreal summer (winter) and during La Nina (El Nino) events. The scatter among different products for seasonal-to-interannual time scales is approximately 1 Sv. Despite the good consistency, systematic difference is found between most ODA products and the INSTANT observations. All but the highest-resolution (18 km) ODA product show a dominant annual cycle while the INSTANT estimate and the 18-km product exhibit a strong semi-annual signal. The coarse resolution is an important factor that limits the level of agreement between ODA and INSTANT estimates. Decadal signals with periods of 10–15 years are seen. The most conspicuous and consistent decadal change is a relatively sharp increase in ITF transport during 1993–2000 associated with the strengthening tropical Pacific trade wind. Most products do not show a weakening ITF after the mid-1970s’ associated with the weakened Pacific trade wind. The scatter of ODA estimates is smaller after than before 1980, reflecting the impact of the enhanced observations after the 1980s. To assess the representativeness of using the average over a three-year period (e.g., the span of the INSTANT Program) to describe longer-term mean, we investigate the temporal variations of the three-year low-pass ODA estimates. The average variation is about 3.6 Sv, which is largely due to the increase of ITF transport from 1993 to 2000. However, the three-year average during the 2004–2006 INSTANT Program period is within 0.5 Sv of the long-term mean for the past few decades.  相似文献