The distribution of the carbonate parameters in the waters of Anadyr Bay of the Bering Sea and in the western part of the Chukchi Sea

The distribution of the total alkalinity (TA), the total inorganic carbon (TCO₂), the calcium (Ca), and the CO₂ partial pressure in the waters of the northwestern Bering Sea (Anadyr Bay) and in the western part of the Chukchi Sea is considered according to the data obtained in August–September 2002. It is shown that the areas treated were sinks of atmospheric CO₂ in the summer of 2002: the total CO₂ exchange between the atmosphere and the seawater was equal to about −20 mmol C/(m² day). The net community production according to the TCO₂ decrease in the upper photic layer in the west of the Chukchi Sea and in the Anadyr Bay waters amounted to 48 ± 12 and 72 ± 18 g C/(m² year), respectively. The comparison with historical data allows one to tell about the pronounced increase of the TCO₂, TA, and Ca concentrations in the waters of Anadyr Bay and in the western part of the Chukchi Sea in the summer 2002. The processes that might have caused the changes observed are the enrichment of the estuarine waters in marine salts under the ice formation in winter and the decrease of the supply of the waters of the Bering Slope Current to the northwestern part of the Bering Sea.     

Annual cycle of fCO2 under sea-ice and in open water in Prydz Bay, East Antarctica

The annual cycle of dissolved nutrients and the fugacity of CO₂ (fCO₂), calculated from the concentration of dissolved inorganic carbon (DIC) and pH, was studied over a 14-month long period (December 1993 to February 1995) at a site in Prydz Bay near Davis Station, Vestfold Hills, East Antarctica. Significant spring decreases in fCO₂ began under the sea-ice in mid-October, when both water column and sea-ice algal activity resulted in the removal of nutrients and DIC and increased pH. Minimum fCO₂ (<100 μatm) and lowest nutrient and DIC concentrations occurred in December and January. The low summer fCO₂ values were clearly the result of biological activity. The seasonal depletion of dissolved nitrate reached 85% in mid-summer when chlorophyll-a concentrations exceeded 15 mg m⁻³. Oceanic uptake of carbon dioxide from the atmosphere, calculated from the fugacity difference and daily wind speeds, averaged more than 30 mmol m⁻² day⁻¹ during the summer ice-free period. This exchange replaced approximately half of the DIC consumed by biological activity. Apparent nutrient utilisation ratios (C/N/P) were close to Redfield values. In autumn fCO₂ began to rise, continuing slowly well into winter, and reaching a maximum close to modern atmospheric values between July and September. This increase can be attributed to a combination of local remineralisation of organic carbon in the water column and the steady increase in the mixing depth of the water column. At first glance, this suggests that air–sea equilibration occurred in winter despite the sea-ice cover, perhaps by horizontal circulation from regions outside the pack ice, or through openings in the ice. However, the persistent 15 to 20% undersaturation of dissolved oxygen throughout the winter suggests an alternate explanation. The late winter fCO₂ level may represent a characteristic established by global circulation, so that as a result of increasing atmospheric CO₂ concentrations, these Antarctic waters are in transition from being a winter-time source of CO₂ to the atmosphere to becoming a sink. Our fCO₂ observations emphasize the need to address seasonal variations in assessing Antarctic contributions to the oceanic control of atmospheric CO₂.     

fCO2 variability at the CARIACO tropical coastal upwelling time series station

Monthly seawater pH and alkalinity measurements were collected between January 1996 and December 2000 at 10°30′N, 64°40′W as part of the CARIACO (CArbon Retention In A Colored Ocean) oceanographic time series. One key objective of CARIACO is to study temporal variability in Total CO₂ (TCO₂) concentrations and CO₂ fugacity (fCO₂) at this tropical coastal wind-driven upwelling site. Between 1996 and 2000, the difference between atmospheric and surface ocean CO₂ concentrations ranged from about − 64.3 to + 62.3 μatm. Physical and biochemical factors, specifically upwelling, temperature, primary production, and TCO₂ concentrations interacted to control temporal variations in fCO₂. Air–sea CO₂ fluxes were typically depressed (0 to + 10 mmol C m^{− 2} day^{− 1}) in the first few months of the year during upwelling. Fluxes were higher during June–November (+ 10 to 20 mmol C m^{− 2} day^{− 1}). Fluxes were generally independent of the slight changes in salinity normally seen at the station, but low positive flux values were seen in the second half of 1999 during a period of anomalously heavy rains and land-derived runoff. During the 5 years of monthly data examined, only two episodes of negative air–sea CO₂ flux were observed. These occurred during short but intense upwelling events in March 1997 (−10 mmol C m^{− 2} day^{− 1}) and March 1998 (− 50 mmol C m^{− 2} day^{− 1}). Therefore, the Cariaco Basin generally acted as a source of CO₂ to the atmosphere in spite of primary productivity in excess of between 300 and 600 g C m^{− 2} year^{− 1}.     

The spatial distribution of surface <Emphasis Type="Italic">f</Emphasis>CO<Subscript>2</Subscript> in the Southwestern East Sea/Japan sea during summer 2005

Fugacity of CO₂ (fCO₂), temperature, salinity, nutrients, and chlorophyll-a were measured in the surface waters of southwestern East Sea/Japan Sea in July 2005. Surface waters were divided into three waters based on hydrographic characteristics: the water with moderate sea surface temperature (SST) and high sea surface salinity (SSS) located east of the front (East water); the water with high SST and moderate SSS located west of the front (West water); and the water with low SST and SSS located in the middle part of the study area (Middle water). High fCO₂ larger than 420 μatm were found in the West water. In the Middle water, CO₂ was undersaturated with respect to the atmosphere, with values between 246 and 380 μatm. Moderate fCO₂ values ranging from 370 to 420 μatm were observed in the East water. For the East and West waters, estimates of temperature dependency of fCO₂ (12.6 and 15.1 μatm °C⁻¹, respectively) were rather similar to a theoretical value, indicating that SST is likely to be a major factor controlling the surface fCO₂ distribution in these two regions. In the Middle water, however, the estimated temperature dependence was somewhat lower than the theoretical value, and relatively high concentrations of surface chlorophyll-a coincided with the low surface fCO₂, implying that biological uptake may considerably affect the fCO₂ distribution. The net sea-to-air CO₂ flux of the study area was estimated to be 0.30±4.81 mmol m⁻² day⁻¹ in summer, 2005.     

Summer and winter air–sea CO2 fluxes in the Southern Ocean

The seasonal variability of the carbon dioxide (CO₂) system in the Southern Ocean, south of 50°S, is analysed from observations obtained in January and August 2000 during OISO cruises conducted in the Indian Antarctic sector. In the seasonal ice zone, SIZ (south of 58°S), surface ocean CO₂ concentrations are well below equilibrium during austral summer. During this season, when sea-ice is not obstructing gas exchange at the air–sea interface, the oceanic CO₂ sink ranges from −2 to −4 mmol/m²/d in the SIZ. In the permanent open ocean zone, POOZ (50–58°S), surface oceanic fugacity fCO₂ increases from summer to winter. The seasonal fCO₂ variations (from 10 to 30 μatm) are relatively low compared to seasonal amplitudes observed in the subtropics or the subantarctic zones. However, these variations in the POOZ are large enough to cross the atmospheric level from summer to winter. Therefore, this region is neither a permanent CO₂ sink nor a permanent CO₂ source. In the POOZ, air–sea CO₂ fluxes calculated from observations are about −1.1 mmol/m²/d in January (a small sink) and 2.5 mmol/m²/d in August (a source). These estimates obtained for only two periods of the year need to be extrapolated on a monthly scale in order to calculate an integrated air–sea CO₂ flux on an annual basis. For doing this, we use a biogeochemical model that creates annual cycles for nitrate, inorganic carbon, total alkalinity and fCO₂. The changing pattern of ocean CO₂ summer sink and winter source is well reproduced by the model. It is controlled mainly by the balance between summer primary production and winter deep vertical mixing. In the POOZ, the annual air–sea CO₂ flux is about −0.5 mol/m²/yr, which is small compared to previous estimates based on oceanic observations but comparable to the small CO₂ sink deduced from atmospheric inverse methods. For reducing the uncertainties attached to the global ocean CO₂ sink south of the Polar Front the regional results presented here should be synthetized with historical and new observations, especially during winter, in other sectors of the Southern Ocean.     

Small Scale Field Study of an Ocean CO<Subscript>2</Subscript> Plume

We have carried out a small-scale (∼20 l) CO₂ sequestration experiment off northern California (684 m depth, ∼5°C, background ocean pH ∼7.7) designed as an initial investigation of the effects of physical forcing of the fluid, and the problem of sensing the formation of a low pH plume. The buoyant CO₂ was contained in a square frame 1.2 m high, exposing 0.21 m² to ocean flow. Two pH electrodes attached to the frame recorded the signal; a second frame placed 1.9 m south of the CO₂ pool was also equipped with two recording pH electrodes. An additional pH electrode was held in the ROV robotic arm to probe the fluid interface. Local water velocities of up to 40 cm sec⁻¹ were encountered, creating significant eddies within the CO₂ box, and forcing wavelets at the fluid interface. This resulted in rapid CO₂ dissolution, with all CO₂ being depleted in a little more than 2 days. The pH record from the sensor closest (∼10 cm) to the CO₂ showed many spikes of low pH water, the extreme value being ∼5.9. The sensor 1 m immediately below this showed no detectable response. The electrodes placed 1.9 m distant from the source also recorded very small perturbations. The results provide important clues for the design of future experiments for CO₂ disposal and biogeochemical impact studies. These include the need for dealing with the slow CO₂ hydration kinetics, better understanding of the fluid dynamics of the CO₂-water interface, and non-point source release designs to provide more constant, controlled local CO₂ enrichments within the experimental area. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

富油微藻富碳培养下油脂积累及固碳研究

微藻固碳是一种新型节能减排技术,具有长期可持续发展的潜力。本文对两株富油微藻（球等鞭金藻和微拟球藻）进行了富碳培养下生长特性及中性脂积累特性的研究。两株富油微藻的最佳培养条件为10%CO₂浓度和f培养基。本研究对两株富油微藻的最大生物量产率、总脂含量、最大油脂产率、微藻的C含量和CO₂固定率进行了测定。球等鞭金藻的各参数指标分别为：142.42±4.58g/（m²·d）,39.95%±0.77%,84.47±1.56g/（m²·d）,45.98%±1.75%和33.74±1.65g/（m²·d）。微拟球藻的各参数指标分别为：149.92±1.80g/（m²·d）,37.91%±0.58%,89.90±1.98g/（m²·d）,46.88%±2.01%和34.08±1.32g/（m²·d）。实验结果显示,两株海洋微藻均属于高固碳优良藻株,适合应用于微藻烟气减排技术开发,具备用于海洋生物质能耦合CO₂减排开发的潜力。     

Effect of changes in water salinity on ammonium, calcium, dissolved inorganic carbon and influence on water/sediment dynamics

The effect of a sudden increase in salinity from 10 to 37 in porewater concentration and the benthic fluxes of ammonium, calcium and dissolved inorganic carbon were studied in sediments of a small coastal lagoon, the Albufera d'Es Grau (Minorca Island, Spain). The temporal effects of the changes in salinity were examined over 17 days using a single diffusion-reaction model and a mass-balance approach. After the salinity change, NH₄⁺-flux to the water and Ca-flux toward sediments increased (NH₄⁺-flux: 5000–3000 μmol m⁻² d⁻¹ in seawater and 600/250 μmol m⁻² d⁻¹ in brackish water; Ca-flux: −40/−76 meq m⁻² d⁻¹ at S=37 and −13/−10 meq m⁻² d⁻¹ at S=10); however, later NH₄⁺-flux decreased in seawater, reaching values lower than in brackish water. In contrast, Ca-flux presented similar values in both conditions. The fluxes of dissolved inorganic carbon, which were constant at S=10 (55/45 mmol m⁻² d⁻¹), increased during the experiment at S=37 (from 30 mmol m⁻² d⁻¹ immediately after salinity increase to 60 mmol m⁻² d⁻¹ after 17 days).In brackish conditions, NH₄⁺ and Ca²⁺ fluxes were consistent with a single diffusion-reaction model that assumes a zero-order reaction for NH₄⁺ production and a first-order reaction for Ca²⁺ production. In seawater, this model explained the Ca-flux observed, but did not account for the high initial flux of NH₄⁺.The mass balance for 17 days indicated a higher retention of NH₄⁺ in porewater in the littoral station in seawater conditions (9.5 mmol m⁻² at S=37 and 1.6 mmol m⁻² at S=10) and a significant reduction in the water consumption at both sites (5 mmol m⁻² at S=37; 35/23 mmol m⁻² at S=10). In contrast, accumulation of dissolved inorganic carbon in porewater was lower in seawater incubations (−10/−1 meq m⁻² at S=37; 50/90 meq m⁻² at S=10) and was linked to a higher efflux of CO₂ to the atmosphere, because of calcium carbonate precipitation in water (675/500 meq m⁻²). These results indicate that increased salinity in shallow coastal waters could play a major role in the global carbon cycle.     

The inhabitants of the spring ice,under-ice water,and sediments of the white sea in the estuarine zone of the Severnaya Dvina River

The data on the supra-ice snow, ice, under-ice water, and benthic algal flora obtained in 2007–2008 by sampling in the estuary of the Severnaya Dvina River are analyzed. The river ice and under-ice water in the estuarine zone and in the channel part of the Severnaya Dvina differed greatly in the algal flora’s composition. The fresh water species never exceeded 8.6%, while the ice algae composed 90–96% of the total ice inhabitants’ biomass. In the under-ice water, this value did not exceed 58–64%. The bacteria in the ice composed not more than 2.5–10% of the total biomass, while, in the under-ice water, 36–49%. The shares of ciliates (0.04%) and nematodes (0.005–1.6%) in the total biomass were negligible. In the estuarine zone, the ice was inhabited mainly by nematodes (78% of the total biomass), while, in the river, their share decreased to 9%. The contribution of bacteria was 15% in Dvina Bay and increased to 61% in the river. The importance of algae in the snow was minor: 7% of the total biomass in the marine zone and 30% in the river region. High species diversity of the algal flora in the sandy and sandy-silty littoral grounds was revealed. The values of the total biomass of the bottom algal flora (0.38 g C/m²) were only two to three times lower than the values revealed in similar habitats in the summer. The epipelithic forms (0.15 g C/m²) dominated, being represented by 46 species of algae (49%). The shares of epipsammonic (0.12 g C/m²) and planktonic (0.11 g C/m²) species were almost equal to each other: 25 and 22 species, respectively (27 and 24%).     

Plankton carbon metabolism and air–water CO2 fluxes at a hypereutrophic tropical estuary

Multiple biotic and abiotic drivers regulate the balance between CO₂ assimilation and release in surface waters. In the present study, we compared in situ measurements of plankton carbon metabolism (primary production and respiration) to calculated air–water CO₂ fluxes (based on abiotic parameters) during 1 year (2008) in a hypereutrophic tropical estuary (Recife Harbor, NE Brazil – 08°03′S, 34°52′W) to test the hypothesis that high productivity leads to a net CO₂ flux from the atmosphere. The calculated CO₂ fluxes through the air–water interface (FCO₂) were negative throughout the year (FCO₂: –2 to –9 mmol C·m^?2·day^?1), indicating that Recife Harbor is an atmospheric CO₂ sink. Respiration rates of the plankton community ranged from 2 to 45 mmol C·m^?2·hr^?1. Gross primary production ranged from 0.2 to 281 mmol C·m^?2·hr^?1, exceeding respiration during most of the year (net autotrophy), except for the end of the wet season, when the water column was net heterotrophic. The present results highlight the importance of including eutrophic tropical shallow estuaries in global air–water CO₂ flux studies, in order to better understand their role as a sink of atmospheric CO₂.     

南大洋普里兹湾基于234Th/238U不平衡法的POC输出通量研究

中国第22次南极科学考察(2005年11月至2006年3月)期间,测定了南极普里兹湾海域5个站位的从表层至150 m水深的不同层位水样中溶解态和颗粒态234Th,238U的放射性比活度以及颗粒有机碳.利用234Th/238U在上层水体中的不平衡,计算了南极普里兹湾上层水体中234Th的平均停留时间和输出通量.结果显示,随着纬度的增加,上层水体中颗粒态和溶解态234Th的平均停留时间总体趋向减小,并在中纬度站位出现了最低值,分别为1~8和29~48 d,而颗粒态和溶解态234Th的输出通量则在中纬度站位出现了最大值,分别为21~38和26~39 dpm/(m3·d).运用箱型清除模式,利用两种不同的方法估算了各水柱中从真光层底部输出的POC通量,平均值分别达到104.7 mmol/(m2·d)(E法)和120.6 mmol/(m2·d)(B法),表明南极普里兹湾夏季存在很高的新生产力,它将会对该海域碳的生物泵过程产生重要作用.     

Biological versus physical processes as drivers of large oscillations of the air–sea CO2 flux in the Antarctic marginal ice zone during summer

The fugacity of CO₂ and abundance of chlorophyll a (Chla) were determined in two long transects from the Polar Front to the Antarctic Continent in austral summer, December 1995–January 1996. Large undersaturations of CO₂ in the surface water were observed coinciding with high Chla content. In the major hydrographic regions the mean air–sea fluxes were found to range from −3 to +7 mmol m⁻² d⁻¹ making these regions act as a sink as well as a source for CO₂. In the total 40-d period, the summation of the several strong source and sink regions revealed an overall modest net source of 0.3 mmol m⁻² d⁻¹, this based on the Wanninkhof (J. Geophys. Res. 97 (1992) 7373) quadratic relationship at in situ windspeed. A simple budget approach was used to quantify the role of phytoplankton blooms in the inorganic carbonate system of the Antarctic seas in a time frame spanning several weeks. The major controlling physical factors such as air–sea flux, Ekman pumping and upwelling are included. Net community production varies between −9 and +7 mmol m⁻² d⁻¹, because of the large oscillations in the dominance of autotrophic (CO₂ fixation) versus heterotrophic (CO₂ respiration) activity. Here the mixed layer depth is the major controlling factor. When integrated over time the gross influx and efflux of CO₂ from air to sea is large, but the net residual air/sea exchange is a modest efflux from sea to atmosphere.     

Dissolved inorganic carbon dynamics in the waters surrounding forested mangroves of the Ca Mau Province (Vietnam)

Dissolved inorganic carbon (DIC) and ancillary data were obtained during the dry and rainy seasons in the waters surrounding two 10-year-old forested mangrove sites (Tam Giang and Kiên Vàng) located in the Ca Mau Province (South-West Vietnam). During both seasons, the spatial variations of partial pressure of CO₂ (pCO₂) were marked, with values ranging from 704 ppm to 11481 ppm during the dry season, and from 1209 ppm to 8136 ppm during the rainy season. During both seasons, DIC, pCO₂, total alkalinity (TAlk) and oxygen saturation levels (%O₂) were correlated with salinity in the mangrove creeks suggesting that a combination of lower water volume and longer residence time (leading to an increase in salinity due to evaporation) enhanced the enrichment in DIC, pCO₂ and TAlk, and an impoverishment in O₂. The low O₂ and high DIC and pCO₂ values suggest that heterotrophic processes in the water column and sediments controlled these variables. The latter processes were meaningful since the high DIC and TAlk values in the creek waters were related to some extent to the influx of pore waters, consistent with previous observations. This was confirmed by the stochiometric relationship between TAlk and DIC that shows that anaerobic processes control these variables, although this approach did not allow identifying unambiguously the dominant diagenetic carbon degradation pathway. During the rainy season, dilution led to significant decreases of salinity, TAlk and DIC in both mangrove creeks and adjacent main channels. In the Kiên Vàng mangrove creeks a distinct increase of pCO₂ and decrease of %O₂ were observed. The increase of TSM suggested enhanced inputs of organic matter probably from land surrounding the mangrove creeks, that could have led to higher benthic and water column heterotrophy. However, the flushing of water enriched in dissolved CO₂ originating from soil respiration and impoverished in O₂ could also have explained to some extent the patterns observed during the rainy season. Seasonal variations of pCO₂ were more pronounced in the Kiên Vàng mangrove creeks than in the Tam Giang mangrove creeks. The air–water CO₂ fluxes were 5 times higher during the rainy season than during the dry season in the Kiên Vàng mangrove creeks. In the Tam Giang mangrove creeks, the air–water CO₂ fluxes were similar during both seasons. The air–water CO₂ fluxes ranged from 27.1 mmol C m⁻² d⁻¹ to 141.5 mmol C m⁻² d⁻¹ during the dry season, and from 81.3 mmol m⁻² d⁻¹ to 154.7 mmol m⁻² d⁻¹ during the rainy season. These values are within the range of values previously reported in other mangrove creeks and confirm that the emission of CO₂ from waters surrounding mangrove forests are meaningful for the carbon budgets of mangrove forests.     

Spatiotemporal Decreases of Nutrients and Chlorophyll-a in the Surface Mixed Layer of the Western North Pacific from 1971 to 2000

Using time series of hydrographic data in the wintertime and summertime obtained along 137°E from 1971 to 2000, we found that the average contents of nutrients in the surface mixed layer showed linear decreasing trends of 0.001∼0.004 μmol-PO₄ l⁻¹ yr⁻¹ and 0.01∼0.04 μmol-NO₃ l⁻¹ yr⁻¹ with the decrease of density. The water column Chl-a (CHL) and the net community production (NCP) had also declined by 0.27∼0.48 mg-Chl m⁻² yr⁻¹ and 0.08∼0.47 g-C-NCP m⁻² yr⁻¹ with a clear oscillation of 20.8±0.8 years. These changes showed a strong negative correlation with the Pacific Decadal Oscillation Index (PDO) with a time lag of 2 years (R = 0.89 ± 0.02). Considering the recent significant decrease of O₂ over the North Pacific subsurface water, these findings suggest that the long-term decreasing trend of surface-deep water mixing has caused the decrease of marine biological activity in the surface mixed layer with a bidecadal oscillation over the western North Pacific.     

Temporal variations of surface oceanic and atmospheric CO2 fugacity and total dissolved inorganic carbon in the northwestern North Pacific

In order to examine temporal variations of the surface oceanic and atmospheric fCO₂ and the DIC concentration, we analyzed air and seawater samples collected during the period May 1992–June 1996 in the northwestern North Pacific, about 30 km off the coast of the main island of Japan. The atmospheric CO₂ concentration has increased secularly at a rate of 1.9 ppmv yr⁻¹, and it showed a clear seasonal cycle with a maximum in spring and a minimum late in summer, produced mainly by seasonally-dependent terrestrial biospheric activities. DIC also showed a prominent seasonal cycle in the surface ocean; the minimum and maximum values of the cycle appeared in early fall and in early spring, respectively, due primarily to the seasonally-dependent activities of marine biota and partly to the vertical mixing of seawater and the coastal upwelling. The oceanic fCO₂ values were almost always lower than those of the atmospheric fCO₂, suggesting that this area of the ocean acts as a sink for atmospheric CO₂. Values varied seasonally, mainly reflecting seasonal changes of SST and DIC, with a secular increase at a rate of 3.7 μatm yr⁻¹. The average values of the annual net CO₂ flux between the ocean and the atmosphere calculated by using the different bulk equations ranged between −0.8 and −1.7 mol m⁻²yr⁻¹, and its magnitude was enhanced and reduced late in spring and mid-summer, respectively, due mainly to the seasonally varying oceanic fCO₂.     

Seasonal and interannual variability of carbon cycle in South China Sea: A three-dimensional physical-biogeochemical modeling study

The South China Sea (SCS) exhibits strong variations on seasonal to interannual time scale, and the changing Southeast Asian Monsoon has direct impacts on the nutrients and phytoplankton dynamics, as well as the carbon cycle. A Pacific basin-wide physical-biogeochemical model has been developed and used to investigate the physical variations, ecosystem responses, and carbon cycle consequences. The Pacific basin-wide circulation model, based on the Regional Ocean Model Systems (ROMS) with a 50-km spatial resolution, is driven with daily air-sea fluxes derived from the National Centers for Environmental Prediction (NCEP) reanalysis between 1990 and 2004. The biogeochemical processes are simulated with the Carbon, Si(OH)₄, Nitrogen Ecosystem (CoSINE) model consisting of multiple nutrients and plankton functional groups and detailed carbon cycle dynamics. The ROMS-CoSINE model is capable of reproducing many observed features and their variability over the same period at the SouthEast Asian Time-series Study (SEATS) station in the SCS. The integrated air-sea CO₂ flux over the entire SCS reveals a strong seasonal cycle, serving as a source of CO₂ to the atmosphere in spring, summer and autumn, but acting as a sink of CO₂ for the atmosphere in winter. The annual mean sea-to-air CO₂ flux averaged over the entire SCS is +0.33 moles CO₂ m⁻²year⁻¹, which indicates that the SCS is a weak source of CO₂ to the atmosphere. Temperature has a stronger influence on the seasonal variation of pCO₂ than biological activity, and is thus the dominant factor controlling the oceanic pCO₂ in the SCS. The water temperature, seasonal upwelling and Kuroshio intrusion determine the pCO₂ differences at coast of Vietnam and the northwestern region of the Luzon Island. The inverse relationship between the interannual variability of Chl-a in summer near the coast of Vietnam and NINO₃ SST (Sea Surface Temperature) index in January implies that the carbon cycle and primary productivity in the SCS is teleconnected to the Pacific-East Asian large-scale climatic variability.     

Alkalinity of sea ice in the high-latitudinal arctic according to the surveys performed at north pole drifting station 34 and characterization of the role of the arctic ice in the CO<Subscript>2</Subscript> exchange

The variability of the total alkalinity in the sea ice of the high-latitudinal Arctic from November 2005 to May 2006 is considered. For the bulk of the one- and two-year sea ice, the alkalinity dependence on the salinity is described as TA = k × Sal, where k is the salinity: alkalinity ratio in the under-ice water. The given relationship is valid within a wide salinity range from 0.1 psu in the desalinated fraction of two-year ice to 36 psu in the snow on the young ice surface. Geochemically significant deviations from the relationship noted were observed exclusively in the snow and the upper layer of one-year ice. In the upper layer of one-year ice, an alkalinity deficiency is observed (ΔTA ～ ?0.07 mequiv/kg, or ?15%). In the snow on the surface of the one-year ice, an alkalinity excess is formed under the desalination (ΔTA is as high as 1.3 mequiv/kg, 380%). The deviations registered are caused by the possibility of carbonate precipitation in the form of CaCO₃ · 6H₂O under the seawater freezing. It is shown that the ice formation and the following melting might cause a loss of the atmospheric CO₂ of up to 3 × 10¹² g C/year.     

High-resolution measurement of Southern Ocean CO2 and O2/Ar by membrane inlet mass spectrometry

This paper evaluates the simultaneous measurement of dissolved gases (CO₂ and O₂/Ar ratios) by membrane inlet mass spectrometry (MIMS) along the 180° meridian in the Southern Ocean. The calibration of pCO₂ measurements by MIMS is reported for the first time using two independent methods of temperature correction. Multiple calibrations and method comparison exercises conducted in the Southern Ocean between New Zealand and the Ross Sea showed that the MIMS method provides pCO₂ measurements that are consistent with those obtained by standard techniques (i.e. headspace equilibrator equipped with a Li–Cor NDIR analyser). The overall MIMS accuracy compared to Li–Cor measurements was 0.8 μatm. The O₂/Ar ratio measurements were calibrated with air-equilibrated seawater standards stored at constant temperature (0 ± 1 °C). The reproducibility of the O₂/Ar standards was better than 0.07% during the 9 days of transect between New Zealand and the Ross Sea.The high frequency, real-time measurements of dissolved gases with MIMS revealed significant small-scale heterogeneity in the distribution of pCO₂ and biologically-induced O₂ supersaturation (ΔO₂/Ar). North of 65°S several prominent thermal fronts influenced CO₂ concentrations, with biological factors also contributing to local variability. In contrast, the spatial variation of pCO₂ in the Ross Sea gyre was almost entirely attributed to the biological utilization of CO_2, with only small temperature effects. This high productivity region showed a strong inverse relationship between pCO₂ and biologically-induced O₂ disequilibria (r² = 0.93). The daily sea air CO₂ flux ranged from − 0.2 mmol/m² in the Northern Sub-Antarctic Front to − 6.4 mmol/m² on the Ross Sea shelves where the maximum CO₂ influx reached values up to − 13.9 mmol/m². This suggests that the Southern Ocean water (south of 58°S) acts as a seasonal sink for atmospheric CO₂ at the time of our field study.     

考洲洋牡蛎养殖海域海-气界面CO2交换通量的时空变化

根据2018年7月、11月和2019年1月、4月对广东考洲洋牡蛎养殖海域进行4个季节调查获得的p H、溶解无机碳(DIC)、水温、盐度、溶解氧(DO)及叶绿素a(Chla)等数据,估算该区域表层海水溶解无机碳体系各分量的浓度、初级生产力(PP)、表层海水CO₂分压[p(CO₂)]和海-气界面CO₂交换通量(FCO₂),分析牡蛎养殖活动对养殖区碳循环的影响。结果表明:牡蛎养殖区表层海水中Chl a、DIC、HCO₃^–和PP显著低于非养殖区;养殖淡季表层海水中pH、DO、DIC、HCO₃^–、和CO₃^2–显著大于养殖旺季,养殖旺季的p(CO₂)和FCO₂显著大于养殖淡季。牡蛎养殖区表层海水夏季、秋季、冬季和春季的海-气界面CO₂交换通量FCO₂平均值分别是(42.04±9.56)、(276...