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1.
Variations in the calcite compensation depth (CCD) in the East Sea (Sea of Japan) since the early middle Miocene were inferred from data on age-depth relationships, sediment carbonate, and benthic foraminifers from ODP sites 794, 795, and 797. The CCD remained relatively shallow during much of the middle Miocene–Pliocene, and deepened sharply at the beginning of the Pleistocene. Since then it has fluctuated rapidly, possibly in relation to the onset of the northern hemisphere glacial cycles in the late Pliocene. The average CCD has deepened since at least the early middle Miocene, coinciding with the long-term drop in eustatic sea level. Received: 5 November 1998 / Revision accepted: 2 February 2000  相似文献   

2.
Mesozooplankton composition and distribution were investigated by Juday net hauls in the Pechora Sea (south-eastern Barents Sea) in July 2001. A total of 66 taxa were identified. The total mesozooplankton abundance varied between 2416 ind m−2 in the northern part and 1458?935 ind m−2 in the south. The biomass ranged between 81 and 19?078 mg DW m−2. Three groups differed greatly in composition, abundance and biomass as delineated by cluster analysis. Copepod species Calanus finmarchicus, Pseudocalanus species and Limnocalanus macrurus dominated in terms of the total biomass within each single cluster. There were significant Spearman rank correlations between mesozooplankton abundance and oceanographic variables, and phytoplankton concentration. Salinity was the main factor affecting the mesozooplankton distribution in the coastal waters, while temperature had greater influence on the abundance and biomass in the central and northern parts. The mean mesozooplankton biomass in the region was higher in comparison with some previous investigations probably due to higher water temperature in summer 2001.  相似文献   

3.
During CREAMS expeditions, fCO2 for surface waters was measured continuously along the cruise tracks. The fCO2 in surface waters in summer varied in the range 320–440 μatm, showing moderate supersaturation with respect to atmospheric CO2. In winter, however, fCO2 showed under-saturation of CO2 in most of the area, while varying in a much wider range from 180 to 520 μatm. Some very high fCO2 values observed in the northern East Sea (Japan Sea) appeared to be associated with the intensive convection system developed in the area. A gas-exchange model was developed for describing the annual variation of fCO2 and for estimating the annual flux of CO2 at the air-sea interface. The model incorporated annual variations in SST, the thickness of the mixed layer, gas exchange associated with wind velocity, biological activity and atmospheric concentration of CO2. The model shows that the East Sea releases CO2 into the atmosphere from June to September, and absorbs CO2 during the rest of the year, from October through May. The net annual CO2 flux at the air-sea interface was estimated to be 0.032 (±0.012) Gt-C per year from the atmosphere into the East Sea. Water column chemistry shows penetration of CO2 into the whole water column, supporting a short turnover time for deep waters in the East Sea. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

4.
Water masses in the East Sea are newly defined based upon vertical structure and analysis of CTD data collected in 1993–1999 during Circulation Research of the East Asian Marginal Seas (CREAMS). A distinct salinity minimum layer was found at 1500 m for the first time in the East Sea, which divides the East Sea Central Water (ESCW) above the minimum layer and the East Sea Deep Water (ESDW) below the minimum layer. ESCW is characterized by a tight temperature–salinity relationship in the temperature range of 0.6–0.12 °C, occupying 400–1500 m. It is also high in dissolved oxygen, which has been increasing since 1969, unlike the decrease in the ESDW and East Sea Bottom Water (ESBW). In the eastern Japan Basin a new water with high salinity in the temperature range of 1–5 °C was found in the upper layer and named the High Salinity Intermediate Water (HSIW). The origin of the East Sea Intermediate Water (ESIW), whose characteristics were found near the Korea Strait in the southwestern part of the East Sea in 1981 [Kim, K., & Chung, J. Y. (1984) On the salinity-minimum and dissolved oxygen-maximum layer in the East Sea (Sea of Japan), In T. Ichiye (Ed.), Ocean Hydrodynamics of the Japan and East China Seas (pp. 55–65). Amsterdam: Elsevier Science Publishers], is traced by its low salinity and high dissolved oxygen in the western Japan Basin. CTD data collected in winters of 1995–1999 confirmed that the HSIW and ESIW are formed locally in the Eastern and Western Japan Basin. CREAMS CTD data reveal that overall structure and characteristics of water masses in the East Sea are as complicated as those of the open oceans, where minute variations of salinity in deep waters are carefully magnified to the limit of CTD resolution. Since the 1960s water mass characteristics in the East Sea have changed, as bottom water formation has stopped or slowed down and production of the ESCW has increased recently.  相似文献   

5.
本文对1987～1988年在山东省部分海岛底栖生物调查时发现的异毛虫科5个种进行了详细的描述并配有插图,其中一种为新亚种,另有3个种在我国为首次记录。  相似文献   

6.
A record of radionuclide fluxes at a deep marginal sea of the Northwest Pacific Ocean (39°40′N 132°24′ E, Japan Basin, East Sea/Sea of Japan) was obtained from analysis of a 1-year continuous collection of sediment-trap samples. The trap was placed at a depth of 2800 m, 500 m above the sea floor, and the samples were recovered at the end of one year. Concentrations of 238U, 234U, 232Th, 230Th and 228Th were measured in the trapped material. All of the radionuclide fluxes showed seasonal variations that were in phase with the variations in total particle flux, which were shown in earlier work to be closely tied to the primary production in the surface water. The formation of authigenic 238U appears to be less than in other open ocean regimes. The residence time of particulate thorium isotopes were of the order of a year, resulting in an average settling rate of a meter per day. Comparison of the measured 230Thex flux with that of the theoretical production in the overlying water column yielded about 40% surplus of 230Th, indicating that lateral advection contributes 230Th to this sampling site.  相似文献   

7.
The vertical structure of low-frequency flows in the central Ulleung Interplain Gap of the southwestern East Sea (Sea of Japan) is analyzed based on full-depth current measurement during November 2002–April 2004. Record-length mean flows are directed toward the Ulleung Basin (Tsushima Basin) throughout the entire water column. Upper current variability above the permanent thermocline with a dominant period of about 50–60 days is shown to be closely related to the displacement of an anticyclonic warm eddy associated with the westward meander of the Offshore Branch. Fluctuations of deep currents below the permanent thermocline have a dominant period of about 40 days. Coherence between the current near the seabed and shallower depths is statistically significant up to 360 m for a period range between 15 and 100 days, but less significantly correlated with currents in the upper 200 m. Data from the densely equipped mooring line reveal that mean and eddy kinetic energies are minima at 1000 m, where isotherm slopes are also relatively flat. Empirical orthogonal function (EOF) analyses suggest that more than 79% of total variances of upper and deep currents can be explained by their respective first EOF mode characterized by nearly depth-independent eigenvectors. Spectral and EOF analyses of observed currents suggest that most of the deep current variability is not directly related to local upper current variability during the observation period.  相似文献   

8.
本文根据１９８９年７月至１９９０年５月北黄海长山群岛海区四个航次（春、夏、秋、冬）水质及底质１４０００余个数据的分析测试结果，探讨了测区水质、底质各要素分布特征，并对其环境质量现状作了初步评价。结果表明，调查区环境质量良好．南部海域环境优于北部。  相似文献   

9.
The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s (SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm3 between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.  相似文献   

10.
The purpose of this paper was to study the community structure, in terms of species composition, abundance and spatial distribution, of fish larvae in a wide coastal area of Sicily facing the Southeastern Tyrrhenian Sea, extending for 2300 km2 from Cape Cefalù to the west, to Cape Rasocolmo in the east. This study analyses how species are assembled in relation to an inshore–offshore gradient and also how environmental conditions, determined by surface circulation patterns occurring in the Central Mediterranean at the local scale, determine the distribution patterns. Samples from 39 stations were collected using a 60‐cm Bongo net during an ichthyoplanktonic survey carried out in June 2006. In all, 62 taxa, representing 32 families, were identified. Cyclothone braueri (59.6%), Engraulis encrasicolus (9.2%) Lampanyctus crocodilus (4.3%) and Lampanyctus pusillus (4.1%) were the most abundant species. The results showed that the highest abundance value (14830.6 fish larvae per 10 m2 sea surface) was observed in the western part of the study area. MDS, SIMPER and CCA analyses revealed well defined groups of stations and assemblages of larvae in accordance with an inshore–offshore gradient. The results of this study could have implications for the management of marine resources because the investigated area has already been identified as a nursery area for many pelagic and coastal fishes and a natural habitat for many species of high commercial interest.  相似文献   

11.
A significant surface net heat loss appears around the Kuroshio and the Tsushima Warm Current regions. The area where the surface heat loss occurs should require heat to be supplied by the current to maintain the long-term annual heat balance. Oceanic heat advection in these regions plays an important role in the heat budget. The spatial distribution of the heat supply by the Tsushima Warm Current near the surface was examined by calculating the horizontal heat supply in the surface layer of the East Sea (the Japan Sea) (ESJS), directly from historical sea surface temperature and current data. We have also found a simple estimation of the effective vertical scale of heat supply by the current to compensate net heat loss using the heat supplied by the current in the surface 10 m layer. The heat supplied by the current for the annual heat balance was large in the Korea/Tsushima Strait and along the Japanese Coast, and was small in the northwestern part of the ESJS. The amount of heat supplied by the current was large in the northwestern part and small in the south-eastern part of the ESJS. These features suggest that the heat supplied by the Tsushima Warm Current is restricted to near the surface around the northeastern part and extends to a deeper layer around the southeastern part of the ESJS. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

12.
 Recent sediment accumulation rates are 18–230 mg cm-2 yr-1 (0.02–0.2 cm yr-1) based on excess 210Pb activity profiles in the southwestern part of the East Sea (Sea of Japan). Assuming no mixing beneath surface mixed layers, 210Pb-derived sediment accumulation rates are 18–32 mg cm-2 yr-1 in the northern part of the Yamato Ridge and the Ulleung Basin, 29–136 mg cm-2 yr-1 in the Korea Plateau, and 230 mg cm-2 yr-1 in the southern shelf. These values generally agree with long-term sedimentation rates estimated from dated ash layers. Received: 6 October 1995 / Revision received: 31 May 1996  相似文献   

13.
Abstract. Seven harpacticoid species were found to be associated with sea ice collected during 5 Antarctic cruises of the RV Polarstern. Their distribution within the fast ice and pack ice zones of the Weddell Sea is presented. Whereas some individuals probably become entrapped into the ice only accidentally, at least 4 species arc genuinely sympagic. These have evolved remarkable adaptations, as evidenced by field and laboratory studies of Dresclieriella glacialis , which is by far the most abundant. Such adaptations include: the ability to penetrate deep into ice; a comparatively high salinity tolerance allowing it to endure large salinity fluctuations associated with ice crystal formation and melting; good swimming ability, necessary both for horizontal dispersal and for a planktonic intermezzo after annual melting of the sea ice. D. glacialis is the first polar non-vertebrate mctazoan to be cultivated through its entire life cycle. Its life history suggests an r-stratcgy; this would be the first indication of such a trait in the polar environment. A new species of Drescheriella , on the other hand, exhibits resting stages (C IV-V) known to date only for Calanoidu but not reported for Harpacticoida.  相似文献   

14.
A nested circulation model system based on the Princeton ocean model(POM) is set up to simulate the currentmeter data from a bottom-mounted Acoustic Doppler Profiler(ADP) deployed at the 30 m depth in the Lunan(South Shandong Province,China) Trough south of the Shandong Peninsula in the summer of 2008,and to study the dynamics of the circulation in the southwestern Huanghai Sea(Yellow Sea).The model has reproduced well the observed subtidal current at the mooring site.The results of the model simulation suggest that the bottom topography has strong steering effects on the regional circulation in summer.The model simulation shows that the Subei(North Jiangsu Province,China)coastal current flows northward in summer,in contrast to the southeastward current in the center of the Lunan Trough measured by the moored currentmeter.The analyses of the model results suggest that the southeastward current at the mooring site in the Lunan Trough is forced by the westward wind-driven current along the Lunan coast,which meets the northward Subei coastal current at the head of the Haizhou Bay to flow along an offshore path in the southeastward direction in the Lunan Trough.Analysis suggests that the Subei coastal current,the Lunan coastal current,and the circulation in the Lunan Trough are independent current systems controlled by different dynamics.Therefore,the current measurements in the Lunan Trough cannot be used to represent the Subei coastal current in general.  相似文献   

15.
Based on the comprehensive collection of the field observed salinity of the Bohai Sea (BHS) and the northern Huanghai Sea (NHS) from the 1950s to the present,the patterns of 10-years-averaged salinity at the different layers in the recent five decades (the 1950s,the 1960s,the 1970s,the 1980s and the 1990s) are obtained by the spatial-temporal interpolation technique with the scrupulous data quality control in this study.Then,by combining the spatial-temporal interpolation technique with successive correction method,the annual distributions of salinity both in the BHS and in the NHS are obtained as well.The data analyses indicate that the overall salinity in the BHS and the NHS increases from the 1960s till the present,with the increase of annual mean salinity of 0.04 psu from the 1950s,and the maximum increase rate of salinity is about 0.14 psu/a in the Bohai Bay.The high salinity tongue extended significantly from the NHS into the BHS.The intensified eastern wind field is related to the western intrusion of the NHS warm current,which probably leads to the moving forward of the high salinity water mass into the BHS.However,it is rather different from the salinity distribution characteristics between the 1950s and the 1960s.The extensive precipitation in the 1960s could lead to an increase in the discharge of the Huanghe River,which might result in the decrease of salinity in the BHS.But the salinity isoline of 32 in the NHS still extended significantly into the BHS in the 1960s.Since the 1980s,the patterns of salinity distribution have changed thoroughly.The salinity in the central area of the BHS was low,while the salinity in the Bohai Bay and the Liaodong Bay was higher than the other regions with its horizontal salinity gradient decreasing in the 1980s.The Empirical Orthogonal Function Analysis (EOF) is also conducted to study the interannual salinity variability of the BHS and the NHS.The correlation coefficient between the time coefficient series of the main mode and the Huanghe River discharge can reach -64.57%.It can be concluded that salinity variation of the BHS and the NHS has strong negative correlation with the Huanghe River discharge.  相似文献   

16.
Integrated geological and geophysical analysis of the anomalous magnetic field along with the previously unpublished profiles of Spanish expeditions onboard the R/V Hesperides and international databases of geomagnetic data processed in the context of the global tectonics concepts made it possible to identify paleomagnetic anomalies C11–C15 and compile the first map of the bottom geochronology of the Scan Basin. Unlike in earlier known publications, the paleoaxis of spreading does extend northeast, but approximately at an angle of 345°. According to calculations, spreading began 35.294?35.706 Ma ago during chron C15r, and the spreading paleoaxis was abandoned 29.527?29.970 Ma ago during chron C11n.2n. Thus, the destruction of the American–Antarctic bridge in the region joining the Bruce and Discovery banks with formation of oceanic crust in the Scan Basin started about 36 Ma ago. Regular spreading of the bottom has been continuing for about 6 Ma at a average rate close to 1.8 cm/year.  相似文献   

17.
Several coeval volcanogenic complexes indicating synchronous volcanic events in the Sea of Japan and the Sea of Okhotsk are defined. Volcanics from different-age complexes of the Sea of Okhotsk show many features in common and are attributed to the Pacific type of calc-alkaline series. They were formed in geodynamic settings of the active continental margin and point to its origination on the continental crust of the fragmented Asian continent margin. The volcanic rocks developed in the Sea of Japan reflect different rifting stages. The initial stage was marked by an eruption of calc-alkaline lavas (Paleocene-Eocene complex). At the stage of the marginal-sea spreading, erupted volcanics of the middle Miocene-Pliocene complex were melted from the depleted mantle and magmatism terminated by an eruption of postspreading Pliocene-Holocene volcanics melted from the enriched mantle EM I. Along with the differences, the magmatism in the Sea of Japan and Sea of Okhotsk has some features in common. In both cases, the sialic component of the lithosphere substantially influenced the magma generation.  相似文献   

18.
Seasonal and spatial distributions of dissolved and particulate dimethylsulfoxide(DMSOd,DMSOp)were measured in the East China Sea and the Yellow Sea during March–April 2011 and October–November 2011.The concentrations of DMSOd and DMSOp in the surface water were 20.6(5.13–73.8)and 8.90(3.75–29.6)nmol/L in spring,and 13.4(4.17–42.7)and 8.18(3.44–22.6)nmol/L in autumn,respectively.Both DMSOd and DMSOp concentrations revealed similar seasonal changes with higher values occurring in spring,mainly because of the higher phytoplankton biomass observed in spring.Moreover,the ratios of DMSOp/chlorophyll a also exhibited an apparent seasonal change with higher values in autumn(35.7 mmol/g)and lower values in spring(23.4 mmol/g),thereby corresponding with the seasonal variation in the proportion of DMSO producers in the phytoplankton community between spring and autumn.In addition,DMSOd and DMSOp concentrations in the surface seawater revealed obvious diurnal variations with the maxima appearing in the afternoon.  相似文献   

19.
To facilitate geological analyses of the Ulleung Basin in the East Sea (Japan Sea) between Korea and Japan, shipborne and satellite altimetry-derived gravity data are combined to derive a regionally coherent anomaly field. The 2-min gridded satellite altimetry-based gravity predicted by Sandwell and Smith [Sandwell DT, Smith WHF (1997) J Geophys Res 102(B5):10,039–10,054] are used for making cross-over adjustments that reduce the errors between track segments and at the cross-over points of shipborne gravity profiles. Relative to the regionally more homogeneous satellite gravity anomalies, the longer wavelength components of the shipborne anomalies are significantly improved with minimal distortion of their shorter wavelength components. The resulting free-air gravity anomaly map yields a more coherent integration of short and long wavelength anomalies compared to that obtained from either the shipborne or satellite data sets separately. The derived free-air anomalies range over about 140 mGals or more in amplitude and regionally correspond with bathymetric undulations in the Ulleung Basin. The gravity lows and highs along the basin’s margin indicate the transition from continental to oceanic crust. However, in the northeastern and central Ulleung Basin, the negative regional correlation between the central gravity high and bathymetric low suggests the presence of shallow denser mantle beneath thinned oceanic crust. A series of gravity highs mark seamounts or volcanic terranes from the Korean Plateau to Oki Island. Gravity modeling suggests underplating by mafic igneous rocks of the northwestern margin of the Ulleung Basin and the transition between continental and oceanic crust. The crust of the central Ulleung Basin is about a 14–15 km thick with a 4–5 km thick sediment cover. It may also include a relatively weakly developed buried fossil spreading ridge with approximately 2 km of relief.  相似文献   

20.
The changes in the phytoplankton absorption properties during a diurnal cycle were investigated at one station located in the north-western area of the Alborán Sea. The experiment was performed in spring when the water column was strongly stratified. This hydrological situation permitted the establishment of a deep chlorophyll a (chl a) fluorescence maximum (DFM) which was located on average close to the lower limit of the mixed layer and the nutricline. The relative abundance of pico-phytoplankton (estimated as its contribution to the total chl a) was higher in the surface, however, micro-phytoplankton dominated the community at the DFM level. Chl a specific absorption coefficient (a*(λ)) also varied with optical depth, with a* (the spectrally average specific absorption coefficient) decreasing by 30% at the DFM depth with respect to the surface. A significant negative correlation between the contribution of the micro-phytoplankton to the total chl a and a* was obtained indicating that a* reduction was due to changes in the packaging effect. Below the euphotic layer, a* increased three-fold with respect to the DFM, which agrees with the expected accumulation of accessory pigments relative to chl a as an acclimation response to the low available irradiance. The most conspicuous change during the diurnal cycle was produced in the euphotic layer where the chl a concentration decreased significantly in the afternoon (from a mean concentration of 1.1 μg L−1 to 0.7 μg L−1) and increased at dusk when it averaged 1.4 μg L−1. In addition, a* and the blue-to-red absorption band ratio increased in the afternoon. These results suggest that a*(λ) diurnal variability was due to increase in photo-protective and accessory pigments relative to chl a. The variation ranges of a*(λ) at 675 and 440 nm (the absorption peaks in the red and blue spectral bands, respectively) in the euphotic layer were 0.01–0.04 and 0.02–0.10 m2 mg−1 chl a, respectively. Approximately 30% out of this variability can be attributed to the diurnal cycle. This factor should therefore be taken into account in refining primary production models based on phytoplankton light absorption.  相似文献   

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