On the variation in calcium content of the waters of Laccadives (Arabian Sea)

The concentration of calcium was determined in the samples collected from four stations in the Laccadive Sea and from two lagoons of Kavaratti and Minicoy atolls. The calcium/chlorinity ratio for the open ocean samples was found to be 0.02168 ± 0.000015 with an average calcium concentration of 424.9 mg kg^?1. A maximum in this ratio was observed at about 200 m depth, below the salinity maximum corresponding to Arabian Sea Surface Water mass. No increase in calcium concentration or in calcium/chlorinity ratio was observed down to 1500 m depth, thereby ruling out the possibility of any calcium carbonate dissolution at these depths. Samples from Kavaratti and Minicoy lagoons gave much lower values of the Ca/Cl ratio (0.02145 ± 0.000036 and 0.02142 ± 0.000046, respectively). These low values are apparently the result of calcium utilization by the coral reefs. Using the reduction in the calcium concentration inside the lagoon, in the absence of any chemical precipitation, the annual CaCO₃ production by reef flat and lagoon on Kavaratti Atoll has been estimated as 1 · 10⁷ kg. This gives an average gross production of 1.4 kg CaCO₃ per m² per yr.     

Recent Primary Production and Small Phytoplankton Contribution in the Yellow Sea during the Summer in 2016

The high nutrient concentration associated with the mixing dynamics of two warm and cold water masses supports high primary production in the Yellow Sea. Although various environmental changes have been reported, no recent information on small phytoplankton contribution to the total primary production as an important indicator for marine ecosystem changes is currently available in the Yellow Sea. The major objective of this study is to determine the small (< 2 μm) phytoplankton contribution to the total primary production in the Yellow Sea during August, 2016. In this study, we found relatively lower chlorophyll a concentrations in the water column than those previously reported in the central waters of the Yellow Sea. Moreover, the overall contribution of small phytoplankton (53.1%) to the total chlorophyll a concentration was considerably higher in this study than that (10.7%) observed previously. Based on the N/P ratio (67.6 ± 36.6) observed in this study, which is significantly higher than the Redfield ratio (16), we believe that phytoplankton experienced P-limiting conditions during the study period. The average daily carbon uptake rate of total phytoplankton in this study was 291.1 mg C m^-2 d^-1 (± 165.0 mg C m^-2 d^-1) and the rate of small phytoplankton was 205.7 mg C m^-2 d^-1 (± 116.0 mg C m^-2 d^-1) which is 71.9% (± 8.8%) of the total daily carbon uptake rate. This contribution of small phytoplankton observed in this study appears to be higher than that reported previously. Our recent measured primary production is approximately 50% lower than the previous values decades ago. The higher contributions of small phytoplankton to the total chlorophyll a concentration and primary production might be caused by P-limited conditions and this resulted in lower chlorophyll a concentration and total primary production in this study compared to previous studies.     

Peculiarities of the primary production process in the Kara Sea at the end of the vegetation season

Research was implemented from September 15 through October 4, 2011 in the Kara Sea along transects located southeastwards Novaya Zemlya, in the St. Anna Trough, the Yenisei River estuary, and the adjacent shelf. The concentration of chlorophyll a was the highest in the photic zone (0.05–2.30 mg/m³, on average, 0.80 ± 0.37 mg/m³). The maximal concentration of Chl a at most of the stations located in the water layer of 7–30 m. Integral primary production in the water column varied from 3.0 to 151.0 mg C/m² per day, on average, 37.2 ± 36.6 mg C/m² per day. The maximal rate of primary production at most of the stations has been observed for the surface layer of the water column. Within the upper mixed water layer, relative primary production was from 31 to 100% (on average, 77 ± 20%). The most productive zone was the waters along Yenisei transect. In the estuary and at the adjacent shelf, primary production was 50 mg C/m² per day, exceeding the range observed for other areas by 1.5–2.0 times. The concentrations of silica and nitrogen together with light regime and water temperature were the major limiting factors affecting the primary production rate in the Kara Sea in autumn.     

Dynamics of phosphorus exchange between sediment and water in a gravel-bed river

ABSTRACT

Phosphorus (P) stores in gravel-bed rivers are released for uptake by periphyton when pH levels exceed 8.5. The Tukituki River has low alkalinity water and frequently experiences periphyton blooms, and daytime pH?>?9 during summer low-flows. We measured dissolved reactive P (DRP) and EPC₀, the water concentration of DRP at which no net release or sorption from the river bed occurs, in sediment samples from the Tukituki River subject to controlled pH levels before (2014) and after (2017) changes to two wastewater discharges that reduced P release to the river by 95%. DRP released from 2014 sediments at pH 8.5–10 were 30?±?10?mg/m³ above background (pH 8) whereas those released from 2017 sediments were 5?±?3?mg/m³ above background. EPC₀ levels in 2014 and 2017 were 11?±?6 and 7?±?2?mg/m³, respectively. Field estimates of released DRP calculated from continuous pH and the Redfield equation suggested that most of the readily available DRP released from sediments at elevated pH is derived from material attached to recently deposited sediment. Subsequently, a reduction in wastewater inputs or agricultural runoff should reduce sediment DRP stores, and hence sediment fluxes, within a few years and mitigate periphyton blooms in addition to directly lowering water column concentrations.     

渤海海区COD分布及对海水富营养化贡献分析

于2002年8月10～18日和2003年8月12～28日对渤海海区进行了海水水质调查。结果表明,调查海域化学耗氧量(COD)平均浓度分别为0.70 mg/L±0.21 mg/L和0.63 mg/L±0.18 mg/L,其中相对高值区(>1 mg/L)主要分布在辽东湾北部,莱州湾南部和中央海区西北部海域,而相对低值区(<0.6 mg/L)主要分布在中央海区东南部。分析表明,调查海域COD浓度不仅远远低于国家一类海水水质标准,而且也大大低于渤海沿岸水。进一步分析表明,COD对于调查海域富营养化的贡献仅为1/4左右,这一结果证明了造成渤海海区富营养化的化学污染物不是COD。     

Seasonal variation of the satellite-derived phytoplankton primary production in the Kara Sea

Seasonal variation of the integrated primary production (IPP) and surface chlorophyll (Chl₀) in different regions of the Kara Sea was studied from satellite data obtained by the MODIS-Aqua colour scanner and averaged for 2003–2015. The minimum variation of Chl₀ concentration during the growing season (from April to October) was 1.5 times in southwestern region and 2 times in the northern region of the sea. It was found that the Chl₀ concentration increased slightly in all regions by the end of the growing season. The maximum IPP value recorded in June coincided with the peak level of photosynthetically active radiation (PAR) and maximum river discharge. The IPP value varied in a wider range compared with the Chl₀ concentration. The ratio of the maximum and minimum monthly average IPP values varied from 8.9 times in Southwestern region to 11.7 times in the Northern region of the sea. The average increase in the Chl₀ concentration was 1.7 times (from 0.78 mg/m³ in April to 1.29 mg/m³ in October). The IPP value varied by a factor of 10.7 (from 26 mg C/m2 per day in October to 279 mg C/m² per day in June). The article also discusses the influence of water column stratification, the concentration of nutrients, the PAR level, and river discharge on the seasonal IPP dynamics in the Kara Sea.     

Northwestern Weddell Sea deep outflow into the Scotia Sea during the austral summers of 2000 and 2001 estimated by inverse methods

The northward outflow of cold, dense water from the Weddell Sea into the world ocean basins plays a key role in balancing the global heat budget. We estimate the geostrophic flow patterns in the northwestern Weddell Sea using box inverse methods applied to quasi-synoptic hydrographic data collected during the Brazilian DOVETAIL 2000 and 2001 austral summer cruises. The analysis is focused on the variations of the deep Weddell Sea outflow into the Scotia Sea within boxes that bound the main deep gaps over the South Scotia Ridge. To determine the geostrophic volume transports in each box, mass, salt, and heat are conserved within neutral density layers that are not in contact with the atmosphere. Implementing the inverse model and using property anomaly equations weighted by the flow estimate uncertainty our results are consistent with those reported in the literature. A bottom triangle extrapolation method is introduced, which improves the estimated property fluxes through hydrographic sections. In the austral summer of 2000 the transports of Weddell Sea Deep Water (WSDW) through the Philip Passage, Orkney Passage, and southwestern Bruce Passage are 0.01±0.01, 1.15±0.33, and 1.03±0.23 Sv (1 Sv=10⁶ m³ s⁻¹, >0 is northward), respectively. After extrapolation within bottom triangles these transports increase to 0.12±0.03, 3.48±1.81, and 1.20±2.16 Sv. Analysis of the hydrographic data reveal distinct oceanographic conditions over the Philip Passage region, with evidence of mesoscale meanders, warmer and saltier Warm Deep Water (WDW) and colder WSDW observed in 2001 than in 2000. Despite these differences the WSDW transport does not present a significant variation between 2000 and 2001. The WSDW transports through the Philip Passage in 2001 are 0.012±0.001 and 0.113±0.001 Sv after extrapolation within bottom triangles. The circulation derived from the inversion in the austral summer of 2001 suggests a sharp weakening of the barotropic cyclonic flow in the Powell Basin, which may be due to northerly and northeasterly winds associated with an atmospheric low-pressure center located west of the Antarctic Peninsula. We suggest that similar variations in atmospheric forcing may explain changes in the intensity of the cyclonic flow observed in the northwestern Weddell Sea and Powell Basin.     

茅尾海夏季海水与表层沉积物叶绿素a空间分布研究

根据2011年6月茅尾海生态环境调查资料,对该海域海水和表层沉积物中叶绿素a的空间分布进行了分析。结果表明,海水叶绿素a变化范围1.384~4.060 mg/m3,平均值为2.143 mg/m3,表层沉积物叶绿素a范围为0.006~0.740 mg/kg(湿重),均值为0.124 mg/kg;海水与表层沉积物叶绿素a均呈现自河口向南逐渐降低的空间分布特征。单位面积表层沉积物叶绿素a平均含量为上方水柱叶绿素a平均含量的129.44%,沉积物对该海域初级生产力有显著的潜在贡献。相关分析表明,海水和沉积物叶绿素a均与无机氮及底栖动物栖息密度呈显著或极显著的正相关关系(P0.05或P0.01)。     

The organic carbon in the water,the particulate matter,and the upper layer of the bottom sediments of the west Kara Sea

In three sections in the Kara Sea, the contents of the dissolved and particulate organic carbon (the DOC and POC, respectively), as well as of the organic carbon of the bottom sediments (C_org) were determined. The contents of varied from 6.3 to 2400 μg/l for the DOC and from 0.84 to 12.2 mg of C/l for the POC. The average concentrations for all the samples tested amounted to 200 μg/l for the DOC (n = 78, σ = 368) and 2.7 mg/l for the POC (n = 92, σ = 2.7). The concentrations of Corg in the samples of the upper layer of the bottom sediments of the area treated varied from 0.13 to 2.10% of the dry substance at an average value of 0.9% (n = 21, σ= 0.49%). It is shown that the distribution of the different forms of organic matter (OM) is an indicator of the supply and spreading of the particulate matter in the Kara Sea and that the DOC and POC of the Kara Sea are formed under the impact of the runoff of the Ob and Yenisei river waters. It is found that the distribution of the OM of the bottom sediments in the surveyed area of the Kara Sea is closely related to their grain-size composition and to the structure of the currents in the area studied. The variations in the Corg content in the bottom sediment cores from the zone of riverine and marine water mixing represent the variability of the OM burial.     

A carbon budget for the Barents Sea

The first carbon budget constructed for the Barents Sea to study the fluxes of carbon into, out of, and within the region is presented. The budget is based on modelled volume flows, measured dissolved inorganic carbon (DIC) concentration, and literature values for dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations. The results of the budget show that ～5600±660×10⁶ t C yr^?1 is exchanged through the boundaries of the Barents Sea. If a 40% uncertainty in the volume flows is included in the error calculation it resulted in a total uncertainty of ±1600×10⁶ t C yr^?1. The largest part of the total budget flux consists of DIC advection (～95% of the inflow and ～97% of the outflow). The other sources and sinks are, in order of importance, advection of organic carbon (DOC+POC; ～3% of both in- and outflow), total uptake of atmospheric CO₂ (～1% of the inflow), river and land sources (～0.2% of the inflow), and burial of organic carbon in the sediments (～0.2% of the outflow). The Barents Sea is a net exporter of carbon to the Arctic Ocean; the net DIC export is ～2500±660×10⁶ t C yr^?1 of which ～1700±650×10⁶ t C yr^?1 (～70%) is in subsurface water masses and thus sequestered from the atmosphere. The net total organic carbon export to the Arctic Ocean is ～80±20×10⁶ t C yr^?1. Shelf pumping in the Barents Sea results in an uptake of ～22±11×10⁶ t C yr^?1 from the atmosphere which is exported out of the area in the dense modified Atlantic Waters. The main part of this carbon was channelled through export production (～16±10×10⁶ t C yr^?1).     

Distribution of the primary production and chlorophyll <Emphasis Type="Italic">a</Emphasis> in the Kara Sea in September of 2007

The studies were performed from September 10 to 29 of 2007 in the Kara Sea in transects westward of the Yamal Peninsula, near the St. Anna Trough, in the Ob River’s estuary, and on the adjacent shelf. The concentration of chlorophyll a in the euphotic layer changed from 0.02 to 4.37 mg/m³, amounting on the average to 0.76 mg/m³. The primary production in the water column varied from 10.9 to 148.0 mg C/m² per day (the mean was 56.9 mg C/m² per day). It was shown that frontal zones divided the Kara Sea into distinct areas with different productivities. The maximum levels of the primary production were measured in the deep part of the Yamal transect (132.4 mg C/m² per day) and the shallow Kara Sea shelf near the Ob River’s estuary (74.9 mg C/m² per day). The characteristics of these regions were the low salinity of the surface water layer (19–25 psu) and the elevated silicon content (12.8–28.1 μg-atom Si/l), which is explainable by the river water inflow. The frontal zones of the Yamal Current in the Yamal and Ob transects displayed high values of the assimilation numbers, amounting to 2.32 and 1.49 mg C/mg of chlorophyll per h, respectively (the maximal for the studied regions).     

Chlorophyll, delayed fluorescence, and primary production in the northwestern part of the Sea of Japan

The content of chlorophyll (Chl), the intensity of delayed fluorescence (DF), the primary production (PP), and the concentrations of macronutrients were measured in the northwestern part of the Sea of Japan during cruise 30 of R/V Professor Gagarinskii in the autumn of 2000. Sixty-three stations were executed in two steps: October 12–17 (stations 2–34) and October 29–November 3 (stations 35–63). At all the stations, CTD probes were performed. Three cross sections were executed twice within a 2-to 3-week interval, during which structural changes in the hydrological fields took place due to the development of an upwelling. During this time, the length of a day and the daily photosynthetically active radiation (PAR) decreased notably. The vertical profiles of Chl and DF showed pronounced maxima. The waters of the shallow-water stations were characterized by an increased Chl content as compared to the deep-water stations. The content of Chl in the photosynthetic layer amounted from 11 to 30 mg/m²; the PP values were from 120 to 520 mg C/m²/day. At the shallow-water stations, during the second step, the Chl concentration increased by roughly 60% (on average, from 0.47 ± 0.22 to 0.77 ± 0.42 mg/m³); the PP value grew by about 40% (from 268 ± 67 to 370 ± 72 mg C/m²/day). At the deep-water stations, this increase was small (the Chl concentration and PP value increased from 0.37 ± 0.20 to 0.41 ± 0.18 mg/m³ and from 356 ± 72 to 377 ± 74 mg C/m²/day, respectively). The changes noted proceeded due to the increase in the nutrient concentrations during the time between the two surveys, despite the decrease in the length of the day and of the daily PAR. The observations performed showed that, during the autumn time, the horizontal water advection across the shelf, caused by the development of the upwelling, plays the key role in the variations of the production characteristics of the Primor’e coastal zone.     

Behavior of uranium in two estuaries of the southeastern United States

Soluble uranium concentrations in the Ogeechee and Savannah Rivers are 0.046 ± 0.005 and 0.026 ± 0.01 μg/l, respectively. Particulate concentrations are approximately similar in the Ogeechee River but are about four times the soluble concentration in the Savannah River. River end-member ²³⁴U/²³⁸U ratios range from 1.04 ± 0.04 to 1.08 ± 0.12. Observations suggest that uranium is removed from estuarine waters at low salinities during low discharge.     

Chemistry of modern sediments in a hypersaline lagoon,north of Jeddah,Red Sea

Previous studies of modern peritidal sedimentary environments of the Red Sea, such as hypersaline lagoons and sea-marginal flats, have concentrated on its northern part, particularly in the Gulf of Aqaba. However, little is known about lagoon sediments in other localities along the Red Sea coastal stretches. This paper deals with the chemical characteristics of the sediments of a hypersaline (Ras Hatiba) lagoon, north of Jeddah, Saudi Arabia. The chemistry of hypersaline lagoon sediments is considerably changed following the modifications to the water chemistry by evaporation and precipitation.Ras Hatiba lagoon is a hypersaline elongated water body connected to the Red Sea by a narrow and shallow opening. The total area of the lagoon is c. 30 km².Coarse bioclastic sands are dominant in the lagoon and mostly surround lithified calcareous grounds. However, fine silt and clay sediments are present in separate patches. The sediments are rich in carbonates (average 78·5%) and organic carbon (average 7·3%), although they are negatively correlated. Calcium (average 25·1%) and magnesium (average 10·8‰) show a similar distribution pattern in the lagoon sediments. Strontium (average 5·2‰) is positively correlated with calcium. Sodium and potassium are relatively highly concentrated in the sediments (average 118 ppm and 173 ppm, respectively). Magnesium and strontium are of prime importance in the process of mineralization and diagenesis.The sabkha formation surrounding the lagoon is of low carbonate and organic carbon content, compared with the lagoon sediments, whilst it is characterized by high magnesium, sodium and potassium concentrations.Ras Hatiba lagoon sediments and sabkha resemble those of the northern Red Sea in the Gulfs of Aqaba and Suez and the Arabian Gulf in their major sedimentological and chemical characteristics.     

Isotope parameters (δD, δ<Superscript>18</Superscript>O) and sources of freshwater input to Kara Sea

The isotope characteristics (δD, δ¹⁸О) of Kara Sea water were studied for quantitative estimation of freshwater runoff at stations located along transect from Yamal Peninsula to Blagopoluchiya Bay (Novaya Zemlya). Freshwater samples were studied for glaciers (Rose, Serp i Molot) and for Yenisei and Ob estuaries. As a whole, δD and δ¹⁸O are higher in glaciers than in river waters. isotope composition of estuarial water from Ob River is δD =–131.4 and δ18O =–17.6‰. Estuarial waters of Yenisei River are characterized by compositions close to those of Ob River (–134.4 and–17.7‰), as well as by isotopically “heavier” compositions (–120.7 and–15.8‰). Waters from studied section of Kara Sea can be product of mixing of freshwater (δD =–119.4, δ¹⁸O =–15.5) and seawater (S = 34.9, δD = +1.56, δ¹⁸O = +0.25) with a composition close to that of Barents Sea water. isotope parameters of water vary significantly with salinity in surface layer, and Kara Sea waters are desalinated along entire studied transect due to river runoff. concentration of freshwater is 5–10% in main part of water column, and <5% at a depth of >100 m. maximum contribution of freshwater (>65%) was recorded in surface layer of central part of sea.     

Eutrophication and annual primary production of phytoplankton in the deep-water part of the Black Sea

Using the data of daily primary production, as well as intraannual and long-term changes in the concentration of chlorophyll “a” and hydrochemical characteristics, the annual primary production of phytoplankton in the deep-water part of the Black Sea is estimated for the three key periods in the contemporary evolution of the sea: preeutrophication, very intense eutrophication, and the present-day period characterized by deeutrophication. It is shown that eutrophication in the second part of the 20th Century led to an increase in the production level not only in the shelf of the Black Sea, but also its deep-water areas. By the end of the 1980s and the early 1990s, the value of the annual primary production in this part of the sea increased from 63 ± 18 g C m⁻² yr⁻¹ (in the 1960s) up to 135 ± 30 g C m⁻² yr⁻¹. On the contrary, after 1993, mainly because of reduced runoff of biogenic substances into the Black Sea from land based sources, there was a decrease in the annual production of phytoplankton in the deep-water areas of the sea, which is currently about 105 g C m⁻² yr⁻¹.     

台湾海峡铀的来源及保守性混合

Seawater samples are collected in the spring of 2013 from the Taiwan Strait for the analysis of uranium(U)concentrations and isotopic compositions using MC-ICP-MS, and the geochemical behavior patterns of U in the Taiwan Strait are then investigated. Average concentrations of individual U isotopes are(3.23±0.14) μg/kg for 238 U,(2.34±0.09)×10~(–2) μg/kg for ~(235)U and(2.05±0.07)×10~(–4) μg/kg for 234 U. Correspondingly, the U isotopic compositions are 155±18 for δ234U and 138±2 for 238U:235U. The U concentrations and isotopic ratios in the Taiwan Strait are similar to those of open ocean seawater, suggesting the dominance of the open ocean input to the strait's U pool.However, river input, as suggested by the slightly lower salinity than that of the open ocean, also affected the U concentrations and isotopic compositions in the strait. From a compilation of U concentrations in the Taiwan Strait and adjacent areas, including the Jiulong Estuary and Zhujiang Estuary, the Xiamen Bay and the northern South China Sea, a strong and significant relationship between U concentration and salinity [U:S; U=(0.093 4±0.002 4)S+(0.092 0±0.061 5)] is revealed, suggesting conservative mixing of U in the Taiwan Strait. To better understand the U geochemistry in the Taiwan Strait, a multiple endmembers mixing model is applied to estimate the contributions of potential sources. The open ocean seawater contributed 69%–95% of U in the Taiwan Strait, with river water approximately 2%, and dust deposition only around 0.13%. Therefore, the model results supported the open ocean input source and the conservative mixing behavior of U derived from the observation of U concentrations and isotopic ratios and U:S ratios. The sediment interstitial water may be an important source of U to the Taiwan Strait with a possible contribution of 3%–29%, consistent with previous investigations based on radium isotopes.However, further investigations are warranted to examine the U concentration in the sediment interstitial water and its input to the overlying seawater in the Taiwan Strait.     

冬季东寨港微微型浮游植物丰度、分布及影响因素

微微型浮游植物是水环境生态碳汇的重要基石之一,也是初级生产的重要执行者。选取了一个典型的陆海交界关键带环境——海南东寨港入海口水域,采集了东寨港红树林保护区开阔水域、入港河流和新埠海海端的微微型浮游植物的样品,通过流式细胞仪分析技术对样品进行分析,以探究它们在东寨港水域中的丰度、分布及环境指示意义。结果表明,冬季水域微微型浮游植物以真核浮游植物(Eukaryote,Euk)和聚球藻(Synechococcus,Syn)两大类群为主,其中聚球藻有两个亚群,分别为富含藻蓝蛋白聚球藻(Phycocyanin-rich,PC)和富含藻红蛋白聚球藻(Phycoerythrin-rich,PE)。Syn-PC、Syn-PE和Euk在东寨港水域表层水体的平均丰度分别为(2.61×10⁴±1.09×10⁴)、(3.06×10⁴±7.05×10³)、(1.56×10⁵±8.03×10⁴) cells/m L,底层水体的平均丰度分别为(2.64×10⁴±...     

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.     

Heat and Freshwater Budgets and Pathways in the Arctic Mediterranean in a Coupled Ocean/Sea-ice Model

The Arctic Mediterranean is important for climate studies because of its unique thermodynamic characteristics and its potential role in freshwater export, which would influences air-sea and ice-sea interactions and may change the North Atlantic thermohaline circulation. It is difficult to obtain consistent and complete estimates of heat and freshwater budgets due to sparse observation. In this paper, we use a coupled Arctic ocean/sea-ice model with NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data, long-term gauged river runoff data, precipitation data and estimates of volume transports to examine heat and freshwater budgets and pathways in dynamically and thermodynamically consistence. The model implements Neptune effect, flux-corrected-transport algorithm and more sophisticated treatments of heat and freshwater fluxes. Uncertainties and deficiencies in the modeling were also evaluated. Results indicate that the Arctic Ocean is provided heat mainly from the Fram Strait branch of Atlantic water at about 46 TW, which is within the range in literature. The Barents Sea branch carries about 43 TW of net heat entering the Barents Sea, but only 2 TW of net heat enters the Arctic Ocean. The Atlantic water is significantly modified in the Barents Sea. About 39 TW of heat is lost, which is consistent with the range of estimates by Simonsen and Haugan (1996). The model suggests 79,422 km³ of freshwater storage mainly distributing the Canada Basin, the Beaufort Sea and the Eurasian coast, which is in a good agreement with estimate by Aagaard and Carmack (1989). Freshwater origins from river runoff, precipitation and the Bering Strait throughflow. Liquid freshwater mainly exports via the Canadian Archipelago and Fram Strait at the rates of 3100 km³/yr and 1400 km³/yr. Sea-ice is dominantly transported through Fram Strait with 1923 km³/yr. Model discrepancies exist and climate drift is clear, which require comprehensive physical treatments of mixing processes and dense water processes in the model.