Several significant hydrographic characteristics and their formation mechanism in the South China Sea during the spring and summer of 1998

INTRODUCTIONTheSCSisthelargestmarginseainthewestoftheNorthPacificOcean .Theprevailingwindinwinterisnortheast,whileinsummeritissouthwest .Itisstilluncertainthathowthecirculationandtemperature -salinityfieldassociatewiththemonsoonforcingandaccompanywithseveralkindsofvariationsbeforeorafterthesummermonsoonburst .DuringSECMEXin 1 998,twointensiveobservationperiods (IOP)havebeencarriedoutntheSCS (Fig 1 ) :IOP1 ,from 1 0Aprilto 5May ;IOP2 ,from 1 2JunetoJuly 6 ,inordertounderstandthe…     

Phytoplankton-pigment signatures and their relationship to spring–summer stratification in the Gulf of Gabes

We investigated the phytoplankton dynamics (determined by CHEMTAX analysis of HPLC pigment data) and its relationships with nutrients and water column structure, during two oceanographic cruises in May–June and September 2006 in the Gulf of Gabes (south-eastern Mediterranean). The May–June cruise coincided with the beginning of the summer stratification, while a strong stratification occurred in September with a more than 30 m deepening of the thermocline, and a reduction of the euphotic depth. This strong stratification resulted in a shift in nitrogen sources from nitrates to ammonium as well as phosphate depletion (0.2 μM) and a decrease in silicate concentrations (<2 μM). With the exception of chlorophyll a, pigment concentrations were higher in September than in May–June samplings. The pico- and nanophytoplankton were the major contributors to phytoplankton total biomass, accounting for 90% and 87% of total chlorophyll a in May–June and September, respectively. Picoplankton persisted throughout the entire survey, occupying different depth layers. Chlorophytes were present at substantial amounts (average 23% of total chlorophyll a) during May–June; however, they declined in September (average 5%). Diatoms were overall poorly represented in this study (2% of total chlorophyll a), due probably to silicate shortage. Apparently, the nutrient availability, but also the water column stability seemed to be among the major factors determining phytoplankton dynamics. Indeed, cyanobacteria were prominent in surface samples during the period of strong stratification, whereas the relative contribution of chlorophytes decreased, probably due to low phosphate availability.     

Distribution of molluscan remains in the sediment of the Chukchi Sea and its vicinity, the Arctic

INTRODUCTIONInordertostudythemarinesedimentationoftheChukchiSeaandBeringSeaandgathertheinformationofpaleoceanographyandpaleoenvironment,theFirstChineseNationalArcticResearchExpeditionTeamcollectedbenthonicmolluscansamplesintheChukchiSea ,BeaufortSeaandBeringSeafromJuly 1sttoSeptember 9th ,1 999byicebreakerXuelong .ItwasnotonlythefirstsamplingthatChinesescientistscollectedmolluscaremainsinabove mentionedar eas,butalsooneofinvestigationsinasinglecruisewithhighersamplingrateandalotofb…     

Diagnostic study of the summer thermocline depth in the Huanghai Sea and the East China Sea

- In this paper, the depth of the summer thermocline of the South Huanghai Sea and the East China Sea is calculated with two kinds of one-dimentional models, and the formation reasons are explained for the summer thermocline depth distribution characteristics in the study area. It is proved that in the shelf area of the East China Sea, tidal mixing has an important impact on the thermocline depth. And a new explanation for certain phenomena of the so-called coastal upwelling in the East China Sea is proposed.     

Winter convection in the Irminger Sea in 2004–2014

Winter convection in the Irminger Sea leading to the formation of Labrador Sea Water (LSW) is analyzed using CTD data collected along the 59.5° N transatlantic section in 2004–2014, winter Argo data from 2012–2014, and daily North American regional reanalysis (NARR). The interannual variability of LSW in the Irminger Sea is investigated. The dissolved oxygen saturation rate of 93% is used to indicate maximal local convection depth. It is shown that the deepest convection (up to 1000 m) resulting in the largest LSW volume that formed in the Irminger Sea in 2008 and 2012. These years were characterized by numerous storms with anomalously strong turbulent heat loss from the ocean to the atmosphere and negative air temperature to the east of the southern tip of Greenland in January–March. LSW became warmer by 0.42°C, saltier by more than 0.03 PSU, and more oxygenated by 8 µmol/kg between 2004 and 2014. A strong LSW decay in the Iceland Basin is also noted.     

Succession of phytoplankton functional groups from spring to early summer in the central Bohai Sea using HPLC–CHEMTAX approaches

Phytoplankton is a key component in the functioning of marine ecosystems, phytoplankton community structures are very sensitive to their environment. This study was conducted in the central Bohai Sea in the spring and early summer of 2015. Spatial variations in phytoplankton functional groups were examined through high-performance liquid chromatography pigment–CHEMTAX analysis. Results suggested that the phytoplankton biomass (chlorophyll a [Chl a]) in spring was mainly derived from the diatom community and was 3.5-fold higher than that in the summer. Meanwhile, the phytoplankton in the early summer sustained more diverse marker pigments than that in the spring. Despite the overwhelming predominance of microsized phytoplankton in the spring, some smaller phytoplankton (pico- or nanosized), including flagellates, such as prasinophytes, chlorophytes, and cryptophytes, highly contributed to the total Chl a in the summer. Various physico-chemical variables were recorded, and their correlations with phytoplankton density were established by redundancy analysis. Temperature, water stratification, nutrient availability, and even nutritive proportion influenced the succession of phytoplankton functional groups from diatom dominance in the spring to flagellate (mainly haptophytes and prasinophytes) dominance in the early summer. In conclusion, our work comprehensively evaluated the phytoplankton diversity and dynamics in the central Bohai Sea and suggests the need for long-term monitoring for further investigation.     

210Pb as a tracer of shelf–basin transport and sediment focusing in the Chukchi Sea

Activities of dissolved, particulate, and sedimentary ²¹⁰Pb were measured in the shelf-slope region of the Chukchi Sea. Samples were collected as part of the Shelf–Basin Interactions (SBI) Phase II process study (6 May–15 June, 2002) along three shelf–basin transects identified as West Hanna Shoal, East Hanna Shoal, and Barrow Canyon. Distributions of ²¹⁰Pb and suspended particulate matter indicate efficient removal of ²¹⁰Pb over the shelf by particle scavenging. Low ²¹⁰Pb activities measured throughout the halocline of the Canada Basin are attributed to shelf scavenging and subsequent advective transport into the interior basin. Additionally, ²¹⁰Pb inventories were used to construct a water-column-sediment budget of ²¹⁰Pb and determine regions of particle export and deposition on the continental shelf and slope. Sediment focusing calculated with this ²¹⁰Pb budget was observed throughout the shelf-slope region, particularly in shallow (∼100 m) shelf waters at Barrow Canyon. Despite elevated concentrations of suspended particulate matter in Barrow Canyon, the ²¹⁰Pb budget does not indicate that sediment transport occurred from the West and East Hanna Shoals into Barrow Canyon.     

Comparison of carbonate parameters and air–sea CO<Subscript>2</Subscript> flux in the southern Yellow Sea and East China Sea during spring and summer of 2011

In this work, we examined the carbonate parameters, i.e. total alkalinity (TA), pH, and partial pressure of CO₂ (pCO₂), and the air–sea CO₂ flux (FCO₂) in the continental shelves of the southern Yellow Sea (SYS) and East China Sea (ECS), based on two field surveys conducted in April and August of 2011. Surface pCO₂ showed significant spatial variations, ranging from 246 to 686 µatm in spring (average ± standard deviation = 379 ± 95 µatm) and from 178 to 680 µatm in summer (384 ± 114 µatm). During the spring cruise, the central SYS (pCO₂ < 240 µatm) and the Changjiang estuary (pCO₂ < 300 µatm) were under-saturated with CO₂, while the southern SYS and the southwestern ECS were supersaturated (pCO₂ = 420–680 µatm). In summer, however, the CO₂-supersaturated waters (pCO₂ = 380–680 µatm) occupied a relatively wide area, including the nearshore of the SYS and the Changjiang estuary, whereas pCO₂-deficient water (pCO₂ = 220–380 µatm) was observed only at the offshore ECS. In general, the entire SYS and ECS area behaved as a sustained CO₂ sink, with average FCO₂ of ?3.9 and ?2.1 mmol m^?2 d^?1 in spring and summer, respectively. Phytoplankton production was the driving force for CO₂ absorption, especially during the spring cruise. In addition, we found that typical water mixing processes and decomposition of terrestrial material were responsible for the release of CO₂ in three turbidity maximum regions.     

Spatiotemporal variability of thermal front features in the Baltic Sea 2010–2011

Regions of the formation of the thermal front in the Baltic Sea (a direct manifestation of the lacustrine thermal bar), and its specific features, were analyzed on the basis of subsurface temperature and salinity. Data were obtained from 25 horizontal tows along sections in the southern and central parts of the Baltic Sea during spring 2010 and autumn/winter 2010/2011. The width of the front was approximately 5?C30 km, and the front lifetime was 1.5 months. Horizontal temperature ranged from 0.7 to 2.5°C; thus, the temperature gradient was one- to twofold larger than the long-term monthly mean equivalent. Analysis of hourly temperature and salinity data from the Arkona basin and at the Darss Sill, obtained at 2 m depth, indicated that the surface temperature increased during the transition through temperatures of maximum density at a rate of approximately 0.01?C0.02°C/h between 3?C5 days; which is 1.4- to 5-fold higher than values before and after this period. The thermal front simultaneously propagated along the main sea axis (due to the significant salinity and buoyancy flux variations from south to north), and from the shallow parts towards the deep parts of the Baltic Sea. Therefore, the horizontal advection of the cold/warm waters clearly contributes to the speed increase of the thermal front at the end of the respective season. The speed of the thermal front propagation from south to north was approximately 28 km/day at the end of the spring period of 2010 (based on field data). This was considerably higher in comparison with the typical values of the lacustrine thermal bar speeds; however, it accords with estimates for a basin with depth/salinity horizontal variation.     

Changes in the population structure of Calanus sinicus during summer–autumn in the southern Yellow Sea

Calanus sinicus is a calanoid copepod widely distributed in coastal waters of China and Japan, and oversummering strategies may have major impacts on their population dynamics which in turn affect local marine food web structure. The abundance, stage composition, and sex composition of the planktonic copepod C. sinicus were studied from August to October 2002 in the southern Yellow Sea to understand how its population recovers from the over-summering state. Results showed that C. sinicus had low reproduction in August due to high temperature, except in waters near the Cheju Island with rich food and moderate bottom temperature, but the reproduction rates here decreased in September–October as food availability declined. When temperature dropped in September–October, C. sinicus actively propagated in coastal shallow waters. However, reproduction rates of C. sinicus individuals inhabiting the Yellow Sea Cold Water Mass(YSCWM) remained low during the three months of the study. The percentage of C. sinicus females was high during the reproductive period, which suggests that the sex composition of adult C. sinicus may reflect whether or not the population is in the reproductive mode.Numerous fifth copepodite stage(CV) C. sinicus aggregated in the YSCWM in a suspended developmental stage during the three months of this study, and they potentially served as the parental individuals for population development when conditions became optimal for reproduction later in the year.     

Study on circulation and meso-scale eddies in the South China Sea in summer of 1998

ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｙｅａｒｓ’ｓｔｕｄｙｈａｓｐｒｉｍａｒｉｌｙｓｈｏｗｎｔｈａｔｔｈｅＳＣＳｈａｓａｎｉｍｐｏｒｔａｎｔｉｎｆｌｕｅｎｃｅｏｎｔｈｅｍｏｎｓｏｏｎｃｕｒｒｅｎｔｓａｎｄｏｎｔｈｅｆｌｏｏｄａｃｔｉｖｉｔｉｅｓｏｃｃｕｒｒｅｄｉｎｔｈｅｒｅｇｉｏｎｏｆＣｈｉｎａ (Ｓｕｎｅｔａｌ .,1 999,Ｄｉｎｇｅｔａｌ.,1 999) .ＴｈｅｍｏｎｓｏｏｎｏｎｓｅｔｉｎｅｖｉｔａｂｌｙｃａｕｓｅｓｔｈｅａｄｊｕｓｔｍｅｎｔｏｆｔｈｅＳＣＳｃｉｒｃｕｌａ ｔｉｏｎ ,ａｎｄｉｎｔｕｒｎ ,ｔｈ…     

Distribution of Pacific-origin water in the region of the Chukchi Plateau in the Arctic Ocean in the summer of 2003

1Introduction Besidestheprecipitationandriverdischarges,the watersinthePacificOceanandtheAtlanticOceanare thesourcesoftheArcticOceanwater.TheAtlantic waterenterstheArcticOceanviatheFramStraitand theBarentsSea.Foritsdenserfeatureduetohigh salinity,mostofitsinkstothenorthofSvaldbardand circulatesinallthedeepbasinsintheArcticOcean, formingthedeepandbottomwatersoftheArcticO- cean(Aagaardetal.,1985;Rudelsetal.,1999).The BeringStraitistheonlychannelforthePacificwater toflowintotheArcticOce…     

Sea ice characteristics between the middle Weddell Sea and the Prydz Bay, Antarctica during the austral summer of 2003

The antarctic sea ice was investigated upon five occasions between January 4 and February 15, 2003. The investigations included: (1) estimation of sea ice distribution by ship-based observations between the middle Weddell Sea and the Prydz Bay; (2) estimation of sea ice distribution by aerial photography in the Prydz Bay; (3) direct measurements of fast ice thickness and snow cover, as well as ice core sampling in Nella Fjord; (4) estimation of melting sea ice distribution near the Zhongshan Station; and (5) observation of sea ice early freeze near the Zhongshan Station. On average, sea ice covered 14.4% of the study area. The highest sea ice concentration (80%) was observed in the Weddell Sea. First-year ice was dominant (99.7%-99.8%). Sea ice distributions in the Prydz Bay were more variable due to complex inshore topography, proximity of the Larsemann Hills, and/or grounded icebergs. The average thickness of landfast ice in NeUa Fjord was 169.5 cm. Wind-blown snow redistribution plays an important role in affecting the ice thickness in Nella Fjord. Preliminary freezing of sea ice near the Zhongshan Station follows the first two phases of the pancake cycle.     

Distribution of artificial radionuclides in the Black Sea and Mediterranean Sea in 1989–1990

The result of research into the distribution of artificial radionuclides of¹³⁷Cs in the Black Sea and the Mediterranean Sea are reported. The data obtained permits consideration of the peculiarities of distribution of this radionuclide in the areas under investigation. The contribution of the Chernobyl radiocaesium to the total radioactivity of these water areas is estimated.Translated by Mikhail M. Trufanov.     

Size-fractionated phytoplankton standing stock and primary production in the Bohai Sea during late spring

During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-fractionated chlorophyll a (Chl a) and primary production, photosynthet-ically available radiation (PAR), as well as the related physico-oceanographic and zooplanktonic parameters were measured at five time-series observation stations representing sub-areas of the sea. Results obtained show that there were the marked features of spatial zonation of Chl a and primary production in the Bohai Sea. The values in the Laizhou Bay, the Liaodong Gulf and the Bohai Gulf were high and showed close relation with tidal fluctuations, i.e. high Chl a concentration occurred during high tide in the Laizhou Bay, and during low tide in the Liaodong Gulf and the Bohai Gulf. In the strait and the central region of the Bohai Sea, the values were relatively low and no relationship with tidal fluctuation could be foun     

Investigation on the fishing ground and fishing period of the drift fishery of Spanish Mackerel in the Huanghai Sea and Bohai Sea during the spring season

The Spanish Mackerel Scomberomorus niphonius (C. et V.), a fish of the upper layer lukewarm water quick in movement, migrates over long distances in shoals. With the development of the nylon drift net the annual catch of such fish has increased rapidly. Since     

Seasonal and inter-annual variability of air–sea CO2 fluxes and seawater carbonate chemistry in the Southern North Sea

A 3D coupled biogeochemical–hydrodynamic model (MIRO-CO₂&CO) is implemented in the English Channel (ECH) and the Southern Bight of the North Sea (SBNS) to estimate the present-day spatio-temporal distribution of air–sea CO₂ fluxes, surface water partial pressure of CO₂ (pCO₂) and other components of the carbonate system (pH, saturation state of calcite (Ω_ca) and of aragonite (Ω_ar)), and the main drivers of their variability. Over the 1994–2004 period, air–sea CO₂ fluxes show significant inter-annual variability, with oscillations between net annual CO₂ sinks and sources. The inter-annual variability of air–sea CO₂ fluxes simulated in the SBNS is controlled primarily by river loads and changes of biological activities (net autotrophy in spring and early summer, and net heterotrophy in winter and autumn), while in areas less influenced by river inputs such as the ECH, the inter-annual variations of air–sea CO₂ fluxes are mainly due to changes in sea surface temperature and in near-surface wind strength and direction. In the ECH, the decrease of pH, of Ω_ca and of Ω_ar follows the one expected from the increase of atmospheric CO₂ (ocean acidification), but the decrease of these quantities in the SBNS during the considered time period is faster than the one expected from ocean acidification alone. This seems to be related to a general pattern of decreasing nutrient river loads and net ecosystem production (NEP) in the SBNS. Annually, the combined effect of carbon and nutrient loads leads to an increase of the sink of CO₂ in the ECH and the SBNS, but the impact of the river loads varies spatially and is stronger in river plumes and nearshore waters than in offshore waters. The impact of organic and inorganic carbon (C) inputs is mainly confined to the coast and generates a source of CO₂ to the atmosphere and low pH, of Ω_ca and of Ω_ar values in estuarine plumes, while the impact of nutrient loads, highest than the effect of C inputs in coastal nearshore waters, also propagates offshore and, by stimulating primary production, drives a sink of atmospheric CO₂ and higher values of pH, of Ω_ca and of Ω_ar.     

The size-fractionated chlorophyll a and primary productivity in the Bering Sea during the summer of 2003

1Introduction Thephytoplanktonistheprimaryproducerofor- ganicsubstancesintheoceanandplaysanimportant roleinthesubstancecycleandenergyconversionof marineecosystem.Chlorophyllaconcentration(Chla) isanimportantindexmanifestingthelightenergy-au- totrophicbiomassinthesea.Primaryproductivityre- flectstheabilitytoconvertinorganiccarbonintoor- ganiccarbonbythephytoplanktonintheocean.Both Chlaandprimaryproductivityaretheimportantcon-tentsbeingstudiedinthemarineecosystemaswellas theimportantfoundationa…     

Multi-scale variability of subsurface temperature in the South China Sea

Using Morlet wavelet transform and harmonic analysis the multi-scale variability of subsurface temperature in the South China Sea is studied by analyzing one-year (from April 1998 to April 1999) ATLAS mooring data. By wavelet transform, annual and semi-annual cycle as well as intrasea-sonal variations are found, with different dominance, in subsurface temperature. For annual harmonic cycle, both the downward net surface heat flux and thermocline vertical movement partially control the subsurface temperature variability. For semi-annual cycle and intraseasonal variability, the subsurface temperature variability is mainly linked to the vertical displacement of thermocline.     

Role of wind and thermal forcing in the formation of the water circulation variability in the Japan/East Sea Central Basin in 1958–2006

Based on the numerical experiment on simulation of the Japan/East Sea (JES) water circulation response to the atmospheric forcing for 1958–2006, the analysis is made of its long-term variability in the JES Central Basin (CB). It was found that during the climatic year, the circulation remains cyclonic, strengthening in spring and weakening in autumn. The analysis of mean relative vorticity (MRV) at intermediate depths in the JES CB showed one that the spectrum of its interannual variability is formed mainly by oscillations of periods ～2, ～4 and ～5 years, and in the decadal range with ～10 and ～14 years. Along the depth, the spectral composition of MRV variability does not change, but there is a noticeable weakening of decadal variability amplitude, which does not occur with the 4- and 5-year oscillations. Using SVD-analysis, the connection is established between MRV variability, wind stress curl (WSC), as well as sensible heat flux. The strong connection between MRV and WSC is revealed in the range of 4–5 years, and in the decadal range (period is 10 years) the significant connection is with both WSC and air-sea temperature as a result of winter cooling and following deep convection.