Increase in total carbonate in the western North Pacific water and a hypothesis on the missing sink of anthropogenic carbon

Sea water samples were collected from various depths in the North Pacific (40–21°N) along 165°E in 1991. Their total carbonate (total dissolved carbonate species) contents were determined with random errors less than 0.2% by a coulometric method. The preformed carbonate contents defined by Chen (1982) were calculated from the obtained data and other observed data including potential temperature, salinity, dissolved oxygen and total alkalinity. The same calculation was done for the GEOSECS data obtained in nearly the same region in 1973. The difference between the two data sets reveals that the preformed carbonate has increased by 180±41 gC/m² during the last 18 years. This value is comparable or somewhat larger than 150 gC/m² obtained in the case that the ocean uptakes 3 GtC/yr for 18 years and distributes it equally among the world oceans. Based on the results, a hypothesis on the missing sink for the anthropogenic carbon dioxide is presented, in that the missing sink is the intermediate waters formed in the northern North Pacific and the Southern Ocean besides the deep waters formed in the North Atlantic and the Southern Ocean.     

Absorption of Atmospheric CO2 and Its Transport to the Intermediate Layer in the Okhotsk Sea

In the southwestern Okhotsk Sea off Hokkaido we observed chemical components related to the carbonate system for 1 year from August 1997 to June 1998. Using the conservative components salinity and water temperature, we confirmed the existence of two water masses flowing into the intermediate layer of the Okhotsk Sea, the East Sakhalin Current Water (ESCW) which becomes denser by mixing of brine water, and the Forerunner of Soya Warm Current Water (FSWW) which becomes denser due to cooling of the saline Kuroshio water. The ΔNTC_x values were calculated by comparing the ESCW and the FSWW with the Pacific Deep Water (PDW). The ΔNTC_x values obtained are 100–110 μmol/kg and 70–100 μmol/kg for the ESCW and the FSWW off Hokkaido, respectively, which are considerably larger than that of the Kuroshio water. These large ΔNTC_x values may be due to both low DIC concentration in the surface water and intense gas exchange under the cold and stormy winter conditions for the ESCW and the cooling of the FSWW as it flows northward. Since the flow rates of dense waters concerned with the ESCW and the FSWW have previously been estimated as 0.9 Sv and 0.2 Sv, respectively, the amount of atmospheric CO₂ absorbed and transported to the intermediate layer turns out to be 3.9−4.1 × 10¹³ gC/yr. This flux is small on a global scale, but the flux divided by the surface layer of the Okhotsk Sea is 30 gC/m²/yr, which is 5 times greater than the mean absorption flux of anthropogenic CO₂ in the world's oceans. It is thus considered that atmospheric CO₂ is efficiently absorbed in the Okhotsk Sea. This revised version was published online in July 2006 with corrections to the Cover Date.     

Total amount of oceanic excess CO2 taken from the North Pacific subpolar region

Concentrations of total carbonate, alkalinity and dissolved oxygen were obtained near the 1973 GEOSECS stations in the North Pacific subpolar region north of 40°N along 175°E between 1993 and 1994. A difference of excess CO₂ content between the GEOSECS and our expeditions was estimated. The maximum difference in water column inventory of excess CO₂ has increased by about 280 gC m^–2 above 2000 m depth which apparently means an uptake of excess CO₂ taken from air to sea during the last two decades. An averaged value of the annual flux of excess CO₂ at 75–1000 m depth was 8.63±2.01 gC m^–2yr^–1 in the North Pacific subpolar region. By introducing the annual flux of excess CO₂ into a two-box model for the North Pacific subpolar region, a penetration factor of excess CO₂ from air to sea was obtained to be 1.08×10^–2 gC m^–3ppm^–1 in the North Pacific subpolar region. Based on this factor, the surface concentration of excess CO₂ in the North Pacific subpolar region was estimated to be 68 mole I^–1, suggesting that the North Pacific subpolar region absorbed atmospheric excess CO₂ more than the saturated concentration of excess CO₂. Total amount of excess CO₂ taken from the North Pacific subpolar region by 1993 was estimated to be 36.2×10¹⁵ gC, which was equal to about one tenth of that released by human activities after the preindustrial era.     

Inorganic carbon in the Labrador Sea: Estimation of the anthropogenic component

The intermediate and deep waters of the Labrador Sea are dominated by recently ventilated water masses (ventilation ages <20 yr). Atmospheric gases such as CO₂ and chlorofluorocarbons are incorporated into these water masses at the time of formation and subsequently transported via boundary currents into the North Atlantic interior. Recent measurements of total carbonate were used in tandem with total alkalinity and oxygen to estimate the levels of anthropogenic carbon dioxide in the Labrador Sea region. Upper water column anthropogenic CO₂ estimated in this manner showed good agreement with levels calculated from CO₂ increase in the atmosphere. In spring 1997, anthropogenic contributions to total carbonate (CTant) were 40±3 μmol/kg in water penetrated by deep convection the previous winter and slightly lower (37±2 μmol/kg) in the deeper convective layer formed in the winters of 1992–1994. Consistent with the concurrent profiles of CFC-11, levels decrease into the older NEADW (North East Atlantic Deep Water) with levels of 30±3 μmol/kg and then increase near bottom within the layer of DSOW (Denmark Strait Overflow Water). The distribution of CTant shows the flow of new LSW southwards with the western boundary current and also eastwards into the Irminger Sea. We estimate that 0.15–0.35 Gt carbon of anthropogenic origin flow through the Labrador Sea within the Western Boundary Undercurrent per year.     

Increase of carbon dioxide in the bottom water of the Weddell Sea, Antarctica

High precision total CO₂ (TCO₂) data are presented from the NW Weddell Sea obtained during two cruises which were 3 years apart. A TCO₂ increase from 1993 to 1996 was observed in the newly formed bottom water, whereas no TCO₂ increase was found in the surrounding water masses. Accompanying this TCO₂ increase in the bottom water was an oxygen decrease. Obviously, bottom water with variable characteristics is produced along the margins of the Weddell Sea. Examination of possible causes leads to the conclusion that the bottom water variability is largely due to varying amounts of Warm Deep Water intruding onto the shelves of the Weddell Sea, thus changing the shelf water end-member of bottom water formation. Analysis of the data, using the observed differences of oxygen to perform a correction, suggested that some part of the TCO₂ increase of the bottom water is due to the increased level of anthropogenic CO₂. The TCO₂ increase of the bottom water is commensurate to a tentative annual increase of about 1 μmol kg⁻¹ in the surface water source of this bottom water. This would agree fairly well with the increase of the partial pressure of CO₂ in the atmosphere.     

Uptake of atmospheric carbon dioxide in Arctic shelf seas: evaluation of the relative importance of processes that influence pCO2 in water transported over the Bering–Chukchi Sea shelf

The uptake of atmospheric carbon dioxide in the water transported over the Bering–Chukchi shelves has been assessed from the change in carbon-related chemical constituents. The calculated uptake of atmospheric CO₂ from the time that the water enters the Bering Sea shelf until it reaches the northern Chukchi Sea shelf slope (1 year) was estimated to be 86±22 g C m⁻² in the upper 100 m. Combining the average uptake per m³ with a volume flow of 0.83×10⁶ m³ s⁻¹ through the Bering Strait yields a flux of 22×10¹² g C year⁻¹. We have also estimated the relative contribution from cooling, biology, freshening, CaCO₃ dissolution, and denitrification for the modification of the seawater pCO₂ over the shelf. The latter three had negligible impact on pCO₂ compared to biology and cooling. Biology was found to be almost twice as important as cooling for lowering the pCO₂ in the water on the Bering–Chukchi shelves. Those results were compared with earlier surveys made in the Barents Sea, where the uptake of atmospheric CO₂ was about half that estimated in the Bering–Chukchi Seas. Cooling and biology were of nearly equal significance in the Barents Sea in driving the flux of CO₂ into the ocean. The differences between the two regions are discussed. The loss of inorganic carbon due to primary production was estimated from the change in phosphate concentration in the water column. A larger loss of nitrate relative to phosphate compared to the classical ΔN/ΔP ratio of 16 was found. This excess loss was about 30% of the initial nitrate concentration and could possibly be explained by denitrification in the sediment of the Bering and Chukchi Seas.     

Variability of the carbonate system parameters in the coast-shelf zone of the East Siberian Sea during the autumn season

The publication presents the results of the studies on the carbonate system of the waters of the East Siberian Sea performed aboard R/V Ivan Kireev in September 2003–2004. It is shown that the aquatic area considered may be subdivided into two biohydrochemical provinces. The western part of the sea is a CO₂ supplier to the atmosphere, while its eastern part is a sink for CO₂. This is caused by the fact that the western part of the East Siberian Sea was affected by the waters of the southeastern part of the Laptev Sea, which were desalinated by riverine runoff, turbid, and enriched in the bioactive organic matter supplied into the water due to the coastal (and bottom) erosion. In the eastern part, cold waters of Pacific origin prevailed (saline, transparent, and productive), which caused a pronounced decrease in the partial pressure of CO₂(pCO₂) in the surface layer. In the frontal zone delimiting the desalinated shelf waters and those of the Pacific origin, the direction of the CO₂ flux between the atmosphere and the sea changed (from evasion to invasion). The interannual variability of the carbonate system parameters in the coastal-shelf zone of the East Siberian Sea was determined by the intensity of the propagation of the waters of different origins over the sea aquatic area caused by the atmospheric circulation, as well as by the riverine runoff intensity and the dynamics of erosion processes.     

Late quaternary organic carbon cycles and paleoproductivity in the Labrador Sea

Accumulation rates of (marine) organic carbon and estimates of paleoproductivity from organic carbon data indicate distinct late Quaternary glacial/interglacial cycles at Ocean Drilling Program (ODP) Site 646. During the last 240,000 years, surface-water productivity was significantly higher in the northern Labrador Sea during interglacial than during glacial times (70 to 170 gC/m²/yr vs. 30 to 70 gC/m²/yr). The reduced glacial productivity is probably caused by a closed sea-ice cover dominating the northern Labrador Sea during glacial intervals.     

The continental shelf pump for CO2 in the North Sea—evidence from summer observation

Data on the distribution of dissolved inorganic carbon (DIC) and partial pressure of CO₂ (pCO₂) were obtained during a cruise in the North Sea during late summer 2001. A 1° by 1° grid of 97 stations was sampled for DIC while the pCO₂ was measured continuously between the stations. The surface distributions of these two parameters show a clear boundary located around 54°N. South of this boundary the DIC and pCO₂ range from 2070 to 2130 μmol kg⁻¹ and 290 to 490 ppm, respectively, whereas in the northern North Sea, values range between 1970 and 2070 μmol kg⁻¹ and 190 to 350 ppm, respectively. The vertical profiles measured in the two different areas show that the mixing regime of the water column is the major factor determining the surface distributions. The entirely mixed water column of the southern North Sea is heterotrophic, whereas the surface layer of the stratified water column in the northern North Sea is autotrophic. The application of different formulations for the calculation of the CO₂ air–sea fluxes shows that the southern North Sea acts as a source of CO₂ for the atmosphere within a range of +0.8 to +1.7 mmol m⁻² day⁻¹, whereas the northern North Sea absorbs CO₂ within a range of −2.4 to −3.8 mmol m⁻² day⁻¹ in late summer. The North Sea as a whole acts as a sink of atmospheric CO₂ of −1.5 to −2.2 mmol m⁻² day⁻¹ during late summer. Compared to the Baltic and the East China Seas at the same period of the year, the North Sea acts a weak sink of atmospheric CO₂. The anticlockwise circulation and the short residence time of the water in the North Sea lead to a rapid transport of the atmospheric CO₂ to the deeper layer of the North Atlantic Ocean. Thus, in late summer, the North Sea exports 2.2×10¹² g C month⁻¹ to the North Atlantic Ocean via the Norwegian trench, and, at the same period, absorbs from the atmosphere a quantity of CO₂ (0.4 10¹² g C month⁻¹) equal to 15% of that export, which makes the North Sea a continental shelf pump of CO₂.     

白令海BR断面海-气CO2通量及其参数特征

通过对2008年夏季白令海大气和海水pCO2连续观测资料,结合BR断面上站位水体垂直采样测量,对白令海不同海区pCO2的分布特征及其与理化参数的关系进行了初步研究,结果表明,将白令海划分为4个具有不同CO2吸收能力的海区,其中陆坡流区碳通量高达-18.72 mmol/(m2·d),是海盆北区的近2倍,比海盆南区高一个量...     

南海东北部春季海表pCO_2分布及海-气CO_2通量

2013年南海东北部春季共享航次采用走航观测方式,现场测定了表层海水和大气的二氧化碳分压(pCO2)及相应参数。结合水文、化学等同步观测要素资料,对该海域pCO2的分布变化进行了探讨。结果表明,陆架区受珠江冲淡水、沿岸上升流及生物活动的影响,呈现CO2的强汇特征;吕宋海峡附近及吕宋岛西北附近海域受海表高温、黑潮分支"西伸"、吕宋岛西北海域上升流等因素影响,呈现强源特征。根据Wanninkhof的通量模式,春季整个南海东北部海域共向大气释放约4.25×104 t碳。     

Distribution and air-sea fluxes of carbon dioxide on the Chukchi Sea shelf

This article presents the results of long-term studies of the dynamics of carbonate parameters and air–sea carbon dioxide fluxes on the Chukchi Sea shelf during the summer. As a result of the interaction of physical and biological factors, the surface waters on the west of Chukchi Sea were undersaturated with carbon dioxide when compared with atmospheric air; the partial pressure of CO₂ varied in the range from 134 to 359 μatm. The average value of CO₂ flux in the Chukchi Sea per unit area varied in the range from–2.4 to–22.0 mmol /(m² day), which is significantly higher than the average value of CO₂ flux in the World Ocean. It has been estimated that the minimal mass of C absorbed by the surface of Chukchi Sea from the atmosphere during ice-free season is 13 × 10¹² g; a great part of this carbon is transported to the deeper layers of sea and isolated from the atmosphere for a long period of time. The studies of the carbonate system of the Chukchi Sea, especially of its western part, will provide some new data on the fluxes of carbon dioxide in the Arctic Ocean and their changes. Our analysis can be used for an interpretation of the satellite assessment of CO₂ fluxes and dissolved CO₂ distribution in the upper layers of the ocean.     

Roles of Continental Shelves and Marginal Seas in the Biogeochemical Cycles of the North Pacific Ocean

Most marginal seas in the North Pacific are fed by nutrients supported mainly by upwelling and many are undersaturated with respect to atmospheric CO₂ in the surface water mainly as a result of the biological pump and winter cooling. These seas absorb CO₂ at an average rate of 1.1 ± 0.3 mol C m⁻²yr⁻¹ but release N₂/N₂O at an average rate of 0.07 ± 0.03 mol N m⁻²yr⁻¹. Most of primary production, however, is regenerated on the shelves, and only less than 15% is transported to the open oceans as dissolved and particulate organic carbon (POC) with a small amount of POC deposited in the sediments. It is estimated that seawater in the marginal seas in the North Pacific alone may have taken up 1.6 ± 0.3 Gt (10¹⁵ g) of excess carbon, including 0.21 ± 0.05 Gt for the Bering Sea, 0.18 ± 0.08 Gt for the Okhotsk Sea; 0.31 ± 0.05 Gt for the Japan/East Sea; 0.07 ± 0.02 Gt for the East China and Yellow Seas; 0.80 ± 0.15 Gt for the South China Sea; and 0.015 ± 0.005 Gt for the Gulf of California. More importantly, high latitude marginal seas such as the Bering and Okhotsk Seas may act as conveyer belts in exporting 0.1 ± 0.08 Gt C anthropogenic, excess CO₂ into the North Pacific Intermediate Water per year. The upward migration of calcite and aragonite saturation horizons due to the penetration of excess CO₂ may also make the shelf deposits on the Bering and Okhotsk Seas more susceptible to dissolution, which would then neutralize excess CO₂ in the near future. Further, because most nutrients come from upwelling, increased water consumption on land and damming of major rivers may reduce freshwater output and the buoyancy effect on the shelves. As a result, upwelling, nutrient input and biological productivity may all be reduced in the future. As a final note, the Japan/East Sea has started to show responses to global warming. Warmer surface layer has reduced upwelling of nutrient-rich subsurface water, resulting in a decline of spring phytoplankton biomass. Less bottom water formation because of less winter cooling may lead to the disappearance of the bottom water as early as 2040. Or else, an anoxic condition may form as early as 2200 AD. This revised version was published online in July 2006 with corrections to the Cover Date.     

Origin of freshwater and polynya water in the Arctic Ocean halocline in summer 2007

Extremely low summer sea-ice coverage in the Arctic Ocean in 2007 allowed extensive sampling and a wide quasi-synoptic hydrographic and δ¹⁸O dataset could be collected in the Eurasian Basin and the Makarov Basin up to the Alpha Ridge and the East Siberian continental margin. With the aim of determining the origin of freshwater in the halocline, fractions of river water and sea-ice meltwater in the upper 150 m were quantified by a combination of salinity and δ¹⁸O in the Eurasian Basin. Two methods, applying the preformed phosphate concentration (PO^*) and the nitrate-to-phosphate ratio (N/P), were compared to further differentiate the marine fraction into Atlantic and Pacific-derived contributions. While PO^*-based assessments systematically underestimate the contribution of Pacific-derived waters, N/P-based calculations overestimate Pacific-derived waters within the Transpolar Drift due to denitrification in bottom sediments at the Laptev Sea continental margin.Within the Eurasian Basin a west to east oriented front between net melting and production of sea-ice is observed. Outside the Atlantic regime dominated by net sea-ice melting, a pronounced layer influenced by brines released during sea-ice formation is present at about 30–50 m water depth with a maximum over the Lomonosov Ridge. The geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the Transpolar Drift.The ratio of sea-ice derived brine influence and river water is roughly constant within each layer of the Arctic Ocean halocline. The correlation between brine influence and river water reveals two clusters that can be assigned to the two main mechanisms of sea-ice formation within the Arctic Ocean. Over the open ocean or in polynyas at the continental slope where relatively small amounts of river water are found, sea-ice formation results in a linear correlation between brine influence and river water at salinities of about 32–34. In coastal polynyas in the shallow regions of the Laptev Sea and southern Kara Sea, sea-ice formation transports river water into the shelf’s bottom layer due to the close proximity to the river mouths. This process therefore results in waters that form a second linear correlation between brine influence and river water at salinities of about 30–32. Our study indicates which layers of the Arctic Ocean halocline are primarily influenced by sea-ice formation in coastal polynyas and which layers are primarily influenced by sea-ice formation over the open ocean. Accordingly we use the ratio of sea-ice derived brine influence and river water to link the maximum in brine influence within the Transpolar Drift with a pulse of shelf waters from the Laptev Sea that was likely released in summer 2005.     

Carbon dioxide stored and acidified low oxygen bottom waters in coastal seas,Japan

Recently carbon dioxide fluxes between sea water and air have been measured in many coastal seas to clarify whether the coastal seas are source or sink of CO₂. In this study behavior of CO₂ within the water column was studied in a semi-enclosed coastal sea: the Seto Inland Sea, Japan. It was found that seasonal formation of hypoxic water mass is highly related to CO₂ dynamics in coastal seas. Bacterial remineralization of organic matter consumes dissolved oxygen (DO) and releases dissolved CO₂ in the bottom water when summertime thermal stratification develops. The CO₂ accumulates within the low DO bottom water (hypoxic water) and causes increasing of carbonic acid content which results in low pH. Concentrations of dissolved CO₂ and pH are highly correlated with DO concentration. The summertime low DO and acidification (low pH) occur in the lower layer every year. The accumulated CO₂ during the summer season is dispersed to the atmosphere at the beginning of mixing season.     

Intraannual and long-term variations of the carbonate system of the aerobic zone in the black sea

We provide an expert quality assessment of the data for 1932–1993 and used these data to perform the numerical analysis of the carbonate system of the aerobic zone in the Black Sea. The intraannual and long-term variations of the carbonate system are studied in the abyssal part of the sea for 1960–1993. We propose explanations of the intraannual variations of the analyzed system for various layers of the aerobic zone and reveal long-term variations of the pH values, total alkalinity, and the ratios of the components of the carbonate system. We discover and explain the observed increase in the concentrations of TCO₂ and CO₂ and the partial pressure of carbon dioxide pCO₂, as well as a decrease in pH values and the concentration of CO₃²⁻ in waters of the aerobic zone of the Black Sea.     

Ventilation time and anthropogenic CO<Subscript>2</Subscript> in the Bering Sea and the Arctic Ocean based on carbon tetrachloride measurements

The Arctic Ocean is connected to the Pacific by the Bering Sea and the Bering Strait. During the 4th Chinese National Arctic Research Expedition, measurements of carbon tetrachloride (CCl₄) were used to estimate ventilation time-scales and anthropogenic CO₂ (C_ant) concentrations in the Arctic Ocean and Bering Sea based on the transit time distribution method. The profile distribution showed that there was a high-CCl₄ tongue entering through the Canada Basin in the intermediate layer (27.6?<?σ_θ?<?28), at latitudes between 78 and 85°N, which may be related to the inflow of Atlantic water. Between stations B09 and B10, upwelling appeared to occur near the continental slope in the Bering Sea. The ventilation time scales (mean ages) for deep and bottom water in the Arctic Ocean (~?230–380 years) were shorter than in the Bering Sea (~?430–970 years). Higher mean ages show that ventilation processes are weaker in the intermediate water of the Bering Sea than in the Arctic Ocean. The mean C_ant column inventory in the upper 4000 m was higher (60–82 mol m^?2) in the Arctic Ocean compared to the Bering Sea (35–48 mol m^?2).     

Recent sediment accumulation and origin of shelf mud deposits in the Yellow and East China Seas

Modern (last 100 yr) accumulation rates of shelf mud deposits in the Yellow and East China Seas were investigated using the distribution of excess ²¹⁰Pb (²¹⁰Pb_ex) in sediment core samples. Compilation and merger of new and previously published data helped clarify sediment accumulation in these seas. The estimated accumulation rates, together with data of suspended sediment concentrations, provided findings on the sediment budget, origin, and transport pathway of the mud deposits. The overall accumulation distribution in the Yellow and East China Sea shelf revealed a general, cross-shelf decreasing trend along the sediment dispersal system away from the rivers, except for the South Sea (SSM) and southeastern Yellow Sea (SEYSM) mud patches found along the Korean coast. Notably, ²¹⁰Pb_ex activity profiles within the SSM and the SEYSM yielded a relatively high accumulation rate of 2-5 mm/yr, implying a sedimentation rate of 4-15 × 10⁷ tons per year in this coastal zone. Such an annual accumulation rate is about one order of magnitude greater than the total sediment discharge (6-20 × 10⁶ tons/yr) from Korean rivers, suggesting an additional offshore source. The distribution pattern of the well-defined suspended plume clearly showed the possible transport and exchange of fine-grained sediments between the ECS shelf and the coastal area of Korea, especially during winter. Such a high accumulation in Korean coastal areas is attributable to the sediments supplied from the mud deposit of the ECS (i.e., SWCIM), with origins in Chinese rivers. Therefore, the Korean coastal area may be an important sink for some of Chinese river sediments being transported from the south by the Yellow Sea Warm Current.     

Density Current Descending along Continental Slope and the Associated Deep Water Formation: Two-Dimensional Numerical Experiments with a Nonhydrostatic Model

Numerical experiments with a two-dimensional nonhydrostatic ocean model have been carried out to investigate the dynamical process of descending density current on a continental slope. The associated deep water formation has been also examined by tracking labeled particles. The descending flow along the continental slope occurs in the bottom Ekman layer. The net pressure gradient determining the volume transport consists of not only the pressure gradient due to density deviation but also the surface pressure gradient due to the depth-mean alongshore flow. Since these constituents have the opposite signs and strengthen each other, the oscillation with an alternation of intense up- and downslope flows appears around the shelf break. This temporal variation of the flow field causes the effective mixing on the slope between descending shelf and interior waters and forms the deep water as a mixture of them at a ratio of about 1:3. The present result is applied to the slope current around Antarctica, using velocity and density fields calculated by an ocean general circulation model. The Ekman volume transport is estimated at 0.97 Sv (1 Sv = 10⁶ m³s^–1) in the Weddell Sea, 0.35 Sv in the Ross Sea, and 1.8 Sv in total. About 70% of them is attributed to the depth-mean alongshore flow, such as the East Wind Drift and the Weddell Gyre driven by the wind. This suggests that the pressure gradient due to other factors than density deviation may play an important role in the deep and bottom water formation in the actual oceans.     

Dimethylsulfide in coastal zone of the East China Sea

Dimethylsulfide (DMS) in seawater were observed four times from February 1993 to August 1994 along a fixed section (PN line) in the East China Sea. The DMS concentrations showed remarkable temporal and spatial variations. The DMS concentrations were generally higher in the upper euphotic layer of the continental shelf zone in summer. The spatial variation, however, was more pronounced even in well mixed winter water, where the concentration of DMS varied widely from 3 to 106 ng-S/l in the continental shelf zone while the salinity was vertically almost uniform. This means that DMS in seawater is rapidly produced and decomposed with a time scale less than one month in the water column. The largest value of 376 ng-S/l was obtained at 5 m depth near the mouth of Changjiang River in August 1994. The mean concentrations in the surface 30 m layer in the continental shelf zone were 21, 54, 126 and 57 ng-S/l in February, October, June and August, respectively, which were about twice as large as those in the Kuroshio region. The mean fluxes of DMS from the East China Sea to the atmosphere are estimated to be 49 g-S/m²/day in winter and 194 g-S/m²/day in summer in the continental shelf zone, and to be 32 and 107 g-S/m²/day in the Kuroshio region.