The continental shelf wave of the East China Sea and its effect on the Kuroshio

The free shelf wave theory is applied to the practical case of the continental shelf in the East China Sea to analyse the effects of the shelf wave on the Kuroshio. The results indicate that the shelf wave in lower frequency travels from north to south and its phase velocity is proportional to the Kuroshio's current velocity) the maximum current velocity of the Kuroshio lies at the continental margin. The analytical solutions obtained indicate that the hydrodynamic characters of the sea region over the shelf present band structure. The horizontal motion ( x -component) caused by the shelf wave at the margin may be one of the causes for generating wavy pattern of the Kuroshio's axis .     

Transport patterns of micro nutrient elements from the continental shelf of the East China Sea to the Kuroshio area

On the basis of the in situ data of DO2, pH, SiO2. PO4-P, NO3-N and NO2-N collected in the north of the East China Sea during 1987-1988, the following points are mainly expounded.1.The inorgonic nutrients are obviously affected by continent runoff in the north of the East China Sea. Their distributions are characteristic of its distribution of terrigenous materials.2.There are three transport paths of nutrients from the shelf to the Kuroshio area. The first is mixing-diffusing-advec-tion and upwelling process, the process of biology and biochemistry belongs to the second, and the sinking process is the last one.3.The swing of the Kuroshio axis affectes both the range of the migration of substances through mixing-diffusing-advec-tion process and the upwelling degree of the subsurface Kuroshio water to the shelf.4.Most part of the substances sink as macroparticles to the deep layer before reaching the Kuroshio area.     

The amplifying effect of southern continental shelf of the East China Sea on semidiurnal tides

The coast of Zhejiang Province is a zone of maximum tidal ranges in China. One of the causes is the influence of the adjacent continental shelf. A model is presented in this paper, whose theory suggests that the amplitudes of semidiurnal tides should be amplified on the southern continental shelf of the East China Sea, while those of diurnal tides should not. The values computed from the equations are basically in agreement with observations.     

Study on interaction between the coastal water, shelf water and Kuroshio water in the Huanghai Sea and East China Sea

The main processes of interaction between the coastal water, shelf water and Kuroshiowater in the Huanghai Sea (HS) and East China Sea (ECS) are analyzed based on the observation and study results in recent years. These processes include the intrusion of the Kuroshio water into the shelf area of the ECS, the entrainment of the shelf water into the Kuroshio, the seasonal process in the southern shelf area of the ECS controlled alternatively by the Taiwan Strait water and the Kuroshio water intruding into the shelf area, the interaction between the Kuroshio branch water, shelf mixed water and modified coastal water in the northeastern ECS, the water-exchange between the HS and ECS and the spread of the Changjiang diluted water.     

Role of Kuroshio frontal eddy in exchange between shelf water and Kuroshio water in East China Sea

Basic patterns of the reversal of the Kuroshio water toward the shelf, intrusion of the shelf mixed waterinto the Kuroshio and uplifting of the near-bottom nutrient-rich water into the upper layer by the pumping of the frontal eddy are analyzed on the basis of satellite infrared images and hydrologic, chemical and biological observations. Results show that the Kuroshio frontal eddies play a very important role in the exchange between the shelf water and the Kuroshio water. The estimation of the average volume transports for three frontal eddy events indicates that the shelf mixed water entrained by an eddy into Kuroshio is 0.44×10~6 m3/s and the reversal Kuroshio water onto the shelf region only 0.04×10~6 m3/s. Along the whole shelf edge, the volume transport of the shelf mixed water entrained by the eddies into the Kuroshio is 1.8×10~6 m3/s. The nutrient (NO3-N) flux pumped to the euphotic zone and input to the continental shelf through a column with 1 m wide is 974 μmol/(s·m) when there is frontal eddy and only 79 μmol/(s·m) in the case of no frontal eddy. Yearly nutrient (NO3-N) flux input to the shelf area caused by the frontal eddy is 1.7×10~5 t/a.     

Response to comments by on “Evidence for the biotic origin of seabed pockmarks on the Australian continental shelf”

Nicholas et al. (2016) restate the results and conclusions of their own past work and that of colleagues on the North West Shelf. Although they accept that fish may be involved in ‘pockmark’ maintenance, they do not accept that fish can initiate such features. The fluid flow theory with which they have been working therefore remains intact. However, the restatement also provides no new information and no cause to revise the conclusions of Mueller (2015). More field data is required.     

An analysis on the formation mechanism of the distribution of high content of chlorophyll-a in the continental shelf edge waters of East China Sea

On the basis of the data obtained from the comprehensive Kuroshio surveys in 1987-1988,this paper analyses the oceanographic characteristics in the area (125°-130° E,27°-31° N) of the continental shelf edge of the East China Sea (E. C. S. ) and its adjacent waters and discusses the effects of the Kuroshio front,thermocline and upwelling of the Kuroshio subsurface water on the distribution of standing stock of phytoplankton (chlorophyll-a). The distribution of high content of chlorophylly-a has been detected at 20-50 in depth in the water body on the left side of the Kuroshio front in the continental shelf edge waters of the E. C. S. The high content of chlorophyll-a spreads from the shelf area to the Kuroshio area in the form of a tongue and connects with the maximum layer of subsurface chlorophyll-a of the Kuroshio and pelagic sea. The author considers that the formation of the distribution of high content chlorophyll-a in this area results from the bottom topography and oceanic environment and the     

The formation and evolution of the East China Sea winter dense water

On the basis of the historical profile observations and the recent Kuroshio observations,the yearly formation,development and decay of the high density water found between 50 to 100 m isobath over the middle and southern East China Sea continental shelf are anyalysed. The formation of this high density water occurs between November and March of the following year. A possible reason for it is that as the mixed water between the coastal water and the outer sea water transports northward by the Taiwan Warm Current, its density increases by surface cooling. It also mixes with the neighbouring lower density water masses. The transportation and decay of the high density water through April to July are also descussed. They can be ascribed to the seasonal surface layer warming and the fast development of Taiwan Warm Current. The high density water disappears in August.     

The study of the Kuroshio in the East China Sea and the currents east of the Ryukyu Islands

In this study, the inverse method is used to compute the Kuroshio in the East China Sea and southeast of Kyushu and the currents east of the Ryukyu Islands, on the basis of hydrographic data obtained during September-October, 1987 by R/V Chofu Maru. The results show that: (1)A part of the Taiwan Warm Current has a tendency to converge to the shelf break; (2) the Kuroshio flows across the section C3 (PN) with a reduced current width, and the velocity of the Kuroshio at the section C3 increases and its maximum current speed is about 158 cm/s, and its volume transport here is about 26×106m3/s; (3) the Kuroshio has two current cores at the sections C3 (PN) and B2 (at the Tokara Strait); (4) the currents east of the Ryukyu Islands are found to flow northward over the Ryukyu Trench during September-October, 1987. The velocities of the currents are not strong throughout the depths. At the section C2 east of the Ryukyu Islands, the maximum current speed is at the 699 m levei and its magnitude is 25 cm/s, and i     

Surface distribution of alkalinity and specific alkalinity and their application to water mass tracing in Kuroshio area of the East China Sea

Surface distribution and seasonal variation of alkalinity and specific alkalinity in Kuroshio area of the East ChinaSea and their application to the water mass tracing are discussed in this paper. Results show a distinct seasonal variation of the alkalinity, which is concerned with the process of vertical mixing. Different specific alkalinity in various water masses has been found. On the basis of the difference of the specific alkalinity and the distribution of alkalinity, two water fronts in summer season, located at 27°-30°N and 124°-1 27°E, (Ⅰ), and at the northern waters about one latitude from the Taiwan Island, (Ⅱ); one in winter season at about one longitude from coast of mainland of China and 26°-30°N were found. In summer season, about 1-2 longitudes eastward shift of front (Ⅰ) is found by comparison of data in May and August. And the high alkalinity of the northern East China Sea in summer season may be caused by the Huanghe River runoff flowing southward along with the Huanghai Sea     

Response of the low-frequency fluctuations of sea level to atmospheric forcing along the coasts of the Huanghai Sea and the East China Sea

In this paper, the low-frequency fluctuations of sea level and their relationship to atmospheric forcing along the coasts of the Huanghai Sea and the East China Sea are studied. Spectrum analyses are made for the time series of daily mean sea level, atmospheric pressure and wind stress at seven coastal stations. It is found that at all the stations, the main part of the energy of the sea level fluctuations, within the (2-60)-day period, is concentrated on the (12-60)-day period band and that an obvious spectral peak appears at the 3-day period. Along the coast of the Huanghai Sea, variations in the sea level are greater in winter than in summer. In winter, along the coasts of the Huanghai Sea and the East China Sea there is a kind of sea level fluctuations propagating southwards. Among the many factors causing sea level variation, the most obvious one is atmospheric pressure, followed next by the alongshore wind stress.     

Distributional characteristics of planktonic Amphipoda (Hyperiidea) in the South Huanghai Sea and East China Sea

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Characteristic analysis on oxygen isotopic tracer in the East China Sea and waters to east of the Ryukyu－gunto

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Seasonal distribution of Calanus sinicus (Copepoda, Crustacea) in the East China Sea

On the basis of the four-season investigation in 23°30′~33°N and 118°30′~128°E of the East China Sea from 1997 to 2000, the seasonal distribution of Calanus sinicus was studied with aggregation intensity, regression contribution and other statistical methods. It was inferred that C. sinicus’s predominance presented from winter to summer, especially in spring and summer, because its dominance amounted to 0.62 and 0.29 respectively. The percent of its abundance in copepod abundance was 76.71% in summer, greater than 66.60% in spring, greater than 19.02% in winter, greater than 4.02% in autumn. The occurrence frequency in winter and spring was 83.08% and 93.89%, higher than that in summer and autumn, 76.71% and 73.87%. Compared with other dominant species of copepods, C. sinicus’s contribution to the copepod abundance was obviously greater than that of the other species in winter, summer and spring, but smaller in autumn. C. sinicus tended to have an aggregated distribution. The clumping index peaked in summer (50.19), followed in spring (19.60), declined in autumn (13.18) and was the lowest in winter (3.04). The abundance changed in different seasons and areas, relating to temperature but not salinity in spring and autumn, to salinity but not temperature in summer; to neither temperature nor salinity in winter. In spring and summer, its high abundance area was often located in the mixed water mass formed by the Taiwan Warm Current, the Huanghai Sea Cold Water Mass, the coastal water masses and the Changjiang Dilute Water. In spring and autumn, its abundance was affected by the warm current, as well as the runoff from continental rivers affected it in summer. It can be inferred that C. sinicus was adapted to wide salinity and temperature, as a euryhalinous and eurythermous species in the East China Sea.     

Organic matter–apatite–pyrite relationships in the Botneheia Formation (Middle Triassic) of eastern Svalbard: Relevance to the formation of petroleum source rocks in the NW Barents Sea shelf

The Middle Triassic Botneheia Formation of eastern Svalbard (Edgeøya and Barentsøya) comprises an organic carbon-rich, fine-grained clastic succession (∼100 m thick) that makes the best petroleum source rock horizon in the NW Barents Sea shelf. The succession records a transgressive–regressive interplay between the prodelta depositional system sourced in the southern Barents Sea shelf (black shale facies of the lower and middle parts of the Muen Member) and the open shelf phosphogenic system related to upwelling and nutrient supply from the Panthalassic Ocean (phosphogenic black shale facies of the upper part of the Muen Member and the Blanknuten Member). The relationships between organic matter, authigenic apatite, and pyrite in these facies allow to characterize the relative roles of redox conditions and oceanic productivity in the organic carbon preservation. The accumulation of terrestrial and autochthonous marine organic matter in the black shale facies occurred under dominating oxic conditions and increasing-upward productivity related to early transgressive phase and retrogradation of the prodelta system. The phosphogenic black shale facies deposited in an oxygen-minimum zone (OMZ) of the open shelf environment during the late transgressive to regressive phases under conditions of high biological productivity, suppressed sedimentation rates, and changing bottom redox. The phosphatic black shales occurring in the lower and upper parts of the phosphogenic succession reveal depositional conditions indicative of the shallower part of OMZ, including high input of autochthonous organic matter into sediment, oxic-to-dysoxic (episodically suboxic and/or anoxic) conditions, intense phosphogenesis, and recurrent reworking of the seabed. The massive phosphatic mudstone occurring in the middle of the phosphogenic succession reflects the development of euxinia in the deeper part of OMZ during high-stand of the sea. High input of autochthonous organic matter in this environment was coupled with mineral starvation and intermittent phosphogenesis. In mature sections in eastern Svalbard, the petroleum potential of the Botneheia Formation rises from moderate to good in the black shale facies, and from good to very good in the phosphogenic black shale facies, attaining maximum in the massive phosphatic mudstone.     

Long-term (1998–2007) trends on the spatial distribution of heterotrophic ciliates in the East China Sea in summer: effect of the Three Gorges Dam construction

The spatial distribution of heterotrophic ciliates, environmental factors and potential food items (bacteria, Synechococcus spp. and nanoflagellates) were measured in the East China Sea to examine which variables contributed importantly to the long-term distribution of ciliates between 1998 and 2007. In July 1998 and June 2003, heterotrophic ciliates were found to be abundant (1,000–2,000 × 10³ cells m⁻³) in regions where surface salinity <32 but extremely low (<500 × 10³ cells m⁻³) in shelf waters of surface salinity >32. After August 2003, shortly after the completion of the Three Gorges Dam, we found no significant areal differences in the abundance of heterotrophic ciliates (HC). However, we found a significantly negative correlation between temperature and HC abundance of surface water after the completion of the dam, suggesting that temperature had a greater influence on HC abundance, once the original saline state had changed. For the long-term trends on the vertical distribution of HC, their abundance was significantly higher in the upper 50 m of the water column than at either 75 or 100 m. Abundance of Synechococcus spp. at these levels varied significantly in regions of surface salinity <32, suggesting that ciliates and picophytoplankton contribute greatly to mediating the transfer of organic matter to higher trophic levels in this marine ecosystem.     

Determination of trophic levels of marine fish in the Yellow Sea and northern East China Sea using nitrogen stable isotope(δ15N)analysis of otoliths

Fish otolith δ15N(δ15Noto)is a demonstrated source of information of dietary history for marine fish as it is available in otolith archives and sedimentary depo...     

The River–Sea Transition Zone (Marginal Filter) of the Northern Dvina River as an Effective Trap of Riverine Sedimentary Matter on Its Way to the Open Area of the White Sea

Oceanology - The article presents the results of generalizing the data of 20 years of research in the river–sea transition zone of the Northern Dvina River and White Sea (marginal filter...     

The effect of the causative algae of large-scale HAB in the East China Sea on egg hatching of Argopecten irradians, and population growth of Brachionus plicatilis and Moina mongolica

The impacts of Prorocentrum donghaiense Lu and Alexandrium catenella Balech, causative species of the large-scale HAB in the East China Sea, were studied under laboratory conditions. According to bloom densities, the effects of monoculture and mixture of the two species were examined on the egg-hatching success of Argopecten irradians Lamarck, and the population growth of Brachionus plicatilis Müller and Moina mongolica Daday. The results showed that monoculture of A. catenella had a significant inhibition on the egg hatching success of A. irradians, and the population growth of B. plicatilis and M. mongolica. The median effective densities (ED_50) inhibiting the egg hatching success of A. irradians for 24 h and the population growth of B. plicatilis and M. mongolica for 96 h were 800, 630, and 2 400 cells/cm3, respectively. Monoculture of P. donghaiense has no such inhibitory effect on the egg hatching success of A. irradians; P. donghaiense at lower suitable densities could sustain the population growth of B. plicatilis (1×104~3×104cells/cm3) and M. mongolica (2×104~5×104cells/cm3); P. donghaiense at higher densities had significantly adverse effect on the population growth of B. plicatilis (4×104~10×104cells/cm3) and M. mongolica (10×104cells/cm3). When the two algae were mixed according to bloom densities, P. donghaiense at suitable densities to some extent could decrease the toxicity of A. catenella to B. plicatilis and M. mongolica. The results indicated that the large-scale HAB in the East China Sea could have adverse effect on zooplankton, and might further influence the marine ecosystem, especially when there was also Alexandrium bloom.     

Reply to the comment of Talwani et al. (2017) on the Sibuet et al. (2016) paper entitled “Thinned continental crust intruded by volcanics beneath the northern Bay of Bengal”

The northern Bay of Bengal velocity-depth profiles do not follow the velocity-depth curve for the North Atlantic volcanic margins, and only partially the Kerguelen plume velocity-depth curves. Compared with the South China Sea northern margin proxy, we still suggest that the Bay of Bengal crust is thinned continental crust intruded by post-rifting volcanics, as also shown by the interpretation of the numerous high-quality deep multichannel seismic profiles we collected there. What was supposed to be underplating might be sills intruded through the lower thinned continental crust.