The atmospheric distribution of lead over a number of marine regions

A data base of 111 filter-collected marine atmospheric particulates is used to describe the distribution of lead over the North and South Atlantic, the Mediterranean Sea, the Red Sea, the Gulf of Aden and the northern and central Arabian Sea. The distribution of atmospheric Pb is assessed in terms of enrichment factor diagrams, and it is shown that over the marine regions studied in both the Northern and Southern Hemispheres the distribution of Pb in the atmosphere is controlled by the mixing of a background component, or components, with crustal material within certain concentration limits. For the Northern Hemisphere samples used in the investigation there is a reasonably well-defined Pb concentration minimum of ～ 0.6 ng m^?3 of air; however, this will be severely decreased in more remote Northern Hemisphere marine regions. Geometric average Pb atmospheric concentrations vary from one marine region to another, ranging from ～ 0.98 ng m^?3 of air for the South Atlantic westerlies to ～ 15 ng m^?3 of air in the North Atlantic westerlies; although the latter reduces to ～ 7 ng m^?3 of air when ‘polluted’ samples are excluded. Lead sea-surface deposition fluxes are calculated on the basis of two deposition velocities (0.25 and 1 cm s^?1), the largest flux (220 ng Pb cm^?2 yr^?1) being found for the westerlies over the eastern margins of the North Atlantic. The distribution of lead over the North Atlantic is assessed in terms of the global lead budget and it is estimated that a maximum of ～ 24% of the total ‘natural’ lead injected annually into the World atmosphere, and ～ 3.5% of the anthropogenic lead injected annually into the Northern Hemisphere atmosphere, are deposited over the North Atlantic sea surface.     

The distributions of particulate atmospheric trace metals and mineral aerosols over the Indian Ocean

Data are presented for the concentrations of Al, Fe, Mn, Ni, Co, Cr, V, Cu, Zn, Pb and Cd in aerosols collected over two contrasting regions of the Indian Ocean. These are: (1) the northern Arabian Sea (AS), from which samples were collected in the northeast monsoon, during which the region receives an input of crustal material from the surrounding arid land masses; and (2) the Tropical Southern Indian Ocean (TSIO), a remote region from which samples were collected from air masses for which there were no large-scale up-wind continental aerosol sources. The TSIO samples can be divided into two populations: Population I aerosols, collected from air masses which have probably impinged on Madagascar, and Population II aerosols, which have been confined to open-ocean regions to the south of the area.The data indicate that there are strong latitudinal variations in the chemical signatures of aerosols over the Indian Ocean. The input of crustal material to the Arabian Sea gives rise to an average Al concentration of about 1000 ng m⁻³ of air in the northeast monsoon regime. As a result, the concentrations of all trace metals are relatively high, and the values of crustal enrichment factors are less than 10 for most metals, in the AS aerosols. In contrast, TSIO Population II ‘open-ocean southern air’ sampled during the southwest monsoon season, has an average Al concentration of only about 10 ng m⁻³ of air. Trace metal concentrations in the TSIO ‘open-ocean southern air’ during the southwest monsoon season are representative of ‘clean’ remote marine air and are generally similar to those reported over the central North Pacific.Mineral dust concentrations over the Indian Ocean decrease in a north to south direction, from about 15–20 μg m⁻³ of air in the extreme north to about 0.01–0.25 μg m⁻³ of air in the far south. The deposition of mineral dust over the northern Arabian Sea can account for approximately 75% of the non-carbonate material incorporated into the underlying sediments.In the Arabian Sea the dissolved atmospheric inputs of all the trace metals, with the exception of Cu and Co, exceed those from fluvial run-off by factors which range from 9.6 for Pb to 1.6 for Cr.     

Responses of marine phytoplankton in iron enrichment experiments in the northern North Sea and northeast Atlantic Ocean

Short-term iron enrichment experiments were carried out with samples collected in areas with different phytoplankton activity in the northern North Sea and northeast Atlantic Ocean in the summer of 1993. The research area was dominated by high numbers of pico-phytoplankton, up to 70,000 ml⁻¹. Maximum chlorophyll a concentrations varied from about 1.0 μg l⁻¹ in a high-reflectance zone (caused by loose coccoliths, remnants from a bloom of Emiliania huxleyi) and about 3.5 μg l⁻¹ in a zone in which the phytoplankton were growing, to about 0.5 μg l⁻¹ in the northeast Atlantic Ocean. From the high-reflectance zone to the northeast Atlantic Ocean, nitrate concentrations increased from 0.5 μM to 6.0 μM. Concentrations of reactive iron in surface water showed an opposite trend and decreased from about 2.6 nM in the high-reflectance zone to <1.0 nM in the northeast Atlantic Ocean. In the research area, no signs of true iron deficiency were found, but iron enrichments in the high-reflectance zone, numerically dominated by Synechococcus sp., resulted in increased nitrate uptake. Ammonium uptake was hardly affected. Strong support for the effect of Fe on cell physiology is given by the increase in the f-ratio. Net growth rates of the phytoplankton (changes in cell numbers over 24 h) were almost unchanged. Phytoplankton collected from the northeast Atlantic Ocean, did not show changes in the nitrogen metabolism upon addition of iron. Net growth rates in these incubations were low or negative, with only slightly higher values with additional iron.     

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.     

Barents Sea upstream events impact the properties of Atlantic water inflow into the Arctic Ocean: Evidence from 2005 to 2006 downstream observations

Inflow of Atlantic water (AW) from Fram Strait and the Barents Sea into the Arctic Ocean conditions the intermediate (100–1000 m) waters of the Arctic Ocean Eurasian margins. While over the Siberian margin the Fram Strait AW branch (FSBW) has exhibited continuous dramatic warming beginning in 2004, the tendency of the Barents Sea AW branch (BSBW) has remained poorly known. Here we document the contrary cooling tendency of the BSBW through the analysis of observational data collected from the icebreaker Kapitan Dranitsyn over the continental slope of the Eurasian Basin in 2005 and 2006. The CTD data from the R.V. Polarstern cruise in 1995 were used as a reference point for evaluating external atmospheric and sea-ice forcing and oxygen isotope analysis. Our data show that in 2006 the BSBW core was saltier (by ～0.037), cooler (by ～0.41 °C), denser (by ～0.04 kg/m³), deeper (by 150–200 m), and relatively better ventilated (by 7–8 μmol/kg of dissolved oxygen, or by 1.1–1.7% of saturation) compared with 2005. We hypothesize that the shift of the meridional wind from off-shore to on-shore direction during the BSBW translation through the Barents and northern Kara seas results in longer surface residence time for the BSBW sampled in 2006 compared with samples from 2005. The cooler, more saline, and better-ventilated BSBW sampled in 2006 may result from longer upstream translation through the Barents and northern Kara seas where the BSBW was modified by sea-ice formation and interaction with atmosphere. The data for stable oxygen isotopes from 1995 and 2006 reveals amplified brine modification of the BSBW core sampled downstream in 2006, which supports the assumption of an increased upstream residence time as indicated by wind patterns and dissolved oxygen values.     

Soil-sized eolian dusts from the lower troposphere of the eastern Mediterranean Sea

Soil-sized eolian dusts have been collected by a mesh technique from the lower troposphere of the eastern Mediterranean. The overall average dust-loading in this region is 14 μg m^?3 of air, which is among the highest recorded for maritime soil-sized dusts.There are two distinct dust populations in the eastern Mediterranean; these have been termed the “northeastern Mediterranean assemblage” and the “southeastern Mediterranean assemblage”.The dusts of the “northeastern assemblage” originate in the soils of southern Europe. The average dust-loading of this assemblage is 12 μg m^?3 of air, and illite is the principal clay mineral with secondary amounts of kaolinite and the smectites. These dusts make only a secondary contribution to the land-derived material in the underlying deep-sea sediments.The dusts of the “southeastern assemblage” have their origin in the desert belts of North Africa and the Middle East. Their average dust-loading is 17 μg m^?3 of air, and kaolinite is their dominant clay mineral. Dusts of the “southeastern assemblage” make an important contribution to the land-derived fractions of some eastern Mediterranean deep-sea sediments.In addition to eolian dusts, river-transported material from the island of Cyprus has also been investigated. The effects of this “Cyprus assemblage” on sedimentation in the eastern Mediterranean is confined to the immediate vicinity of the island itself.     

北冰洋楚科奇海浮游细菌丰度和生产力及其分布特征

2012年夏季中国第5次北极科学考察期间,对北冰洋楚科奇海及其北部边缘海浮游细菌丰度和生产力进行了测定,并将其与环境因子进行了相关性分析。结果显示,楚科奇海浮游细菌丰度的变化范围为0.56×108~6.41×108 cells/dm3,平均为2.25×108 cells/dm3;细菌生产力介于0.042~1.92mg/(m3·d)(以碳计)之间,平均为0.54mg/(m3·d)(以碳计),与已有研究结果基本相当。陆架区细菌丰度和生产力要明显高于北部边缘区,但前者的单位细菌生产力则较低。与环境因子的相关性分析显示,细菌丰度与温度和叶绿素a浓度存在显著正相关(p0.01),表明北极变暖导致的海水升温及浮游植物生物量的增加均会促进细菌的生长,从而进一步提高细菌在海洋生态系统和碳循环中的作用。但陆架区的细菌生产力与环境参数均没有显著相关性,表明其影响因素较为复杂;生产力在北部边缘区则仅与叶绿素a存在显著正相关(p0.01),表明浮游植物生长过程产生的溶解有机碳(DOC)是细菌生长最为主要的碳源,碳源的单一可能制约细菌的生产从而导致该海域无冰状态下细菌丰度的增加不如预期,但融冰过程带来的大量DOC将促进细菌活性的增加。     

Particulate aluminium fluxes in the eastern Atlantic

The atmospheric, primary down-column and sedimentary fluxes of particulate aluminium (Al_p) have been calculated for a number of regions in the Atlantic Ocean.The vertical down-column flux of Al_p from Atlantic surface waters exhibits a strong geographical variation, and its magnitude is influenced by supply mechanisms, which control the surface Al_p concentrations, and primary production, which affects the rate of down-column transport. Overall, the down-column transport of Al_p is greatest in the marginal regions of the Atlantic. In the eastern margins the highest surface water concentrations are found in the region lying between ～30°N and ～10°N, i.e. under the general path of the northeast trades. In this region there is excellent agreement between the dry (i.e. 1 cm^?1 s^?1 deposition velocity) atmospheric flux (～80 000 ng Al_p cm^?2 y^?1), the primary vertical down-column flux ($\text{? 70 000}\text{ng Al}{}_{\mathrm{p}}\text{cm}{}^{\mathrm{?2}}\text{y}{}^{\mathrm{?1}}$) and the sediment flux (～90 000 ng Al_p cm^?2 y^?1). In the regions to the north (i.e. ～40°N to ～30°N) and to the south (i.e. ～10°N to ～5°S) the primary down-column Al_p flux decreases to an average of ～19 000 μg cm^?2 y^?1, which makes a direct maximum contribution of ～20% of the sediment Al_p requirement. In the open-ocean South Atlantic the primary down-column flux of Al_p is ～3300 μg cm^?2 y^?1, this is similar to the dry (i.e. 1 cm^?1 s^?1 deposition velocity) atmospheric flux, and contributes ～20% of the Al_p required by the underlying deep-sea sediment.     

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).     

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.     

Dense water formation and circulation in the Barents Sea

Dense water masses from Arctic shelf seas are an important part of the Arctic thermohaline system. We present previously unpublished observations from shallow banks in the Barents Sea, which reveal large interannual variability in dense water temperature and salinity. To examine the formation and circulation of dense water, and the processes governing interannual variability, a regional coupled ice-ocean model is applied to the Barents Sea for the period 1948-2007. Volume and characteristics of dense water are investigated with respect to the initial autumn surface salinity, atmospheric cooling, and sea-ice growth (salt flux). In the southern Barents Sea (Spitsbergen Bank and Central Bank) dense water formation is associated with advection of Atlantic Water into the Barents Sea and corresponding variations in initial salinities and heat loss at the air-sea interface. The characteristics of the dense water on the Spitsbergen Bank and Central Bank are thus determined by the regional climate of the Barents Sea. Preconditioning is also important to dense water variability on the northern banks, and can be related to local ice melt (Great Bank) and properties of the Novaya Zemlya Coastal Current (Novaya Zemlya Bank). The dense water mainly exits the Barents Sea between Frans Josef Land and Novaya Zemlya, where it constitutes 63% (1.2 Sv) of the net outflow and has an average density of 1028.07 kg m⁻³. An amount of 0.4 Sv enters the Arctic Ocean between Svalbard and Frans Josef Land. Covering 9% of the ocean area, the banks contribute with approximately 1/3 of the exported dense water. Formation on the banks is more important when the Barents Sea is in a cold state (less Atlantic Water inflow, more sea-ice). During warm periods with high throughflow more dense water is produced broadly over the shelf by general cooling of the northward flowing Atlantic Water. However, our results indicate that during extremely warm periods (1950s and late 2000s) the total export of dense water to the Arctic Ocean becomes strongly reduced.     

1957～2002年南海—北印度洋海浪场波候特征分析

利用ERA-40海表10 m风场驱动第三代海浪数值模式WAVEWATCH-Ⅲ,得到南海—北印度洋1957年9月至2002年8月的海浪场,并分析其波候(风候)特征.研究发现如下主要特征:(1)该海域的波高波向、风速风向受季风影响显著;(2)北印度洋大部分海域的海表风速呈显著性逐年线性递增趋势,大约0.01～0.02 m/(s·a),南海线性递增的区域则较少,有效波高呈显著性逐年线性递增的区域主要集中在低纬度中东印度洋(约0.003～0.006 m/a)、索马里附近海域(大约0.002～0.005 m/a)、南海大部分海域(约0.002～0.004 m/a),线性递减的区域主要集中在孟加拉湾海域(约-0.002 m/a);(3)Nino3指数与南海—北印度洋的海表风场、浪场存在密切的关系;(4)南海—北印度洋的海表风速与有效波高存在5.2a左右的共同周期,南海的海表风速、有效波高还存在2.0a左右的共同周期,北印度洋的海表风速、有效波高还存在26.0a的长周期震荡.     

Phytoplankton growth and microzooplankton grazing in the subarctic Pacific Ocean and the Bering Sea during summer 1999

Phytoplankton growth and microzooplankton grazing rates were measured by the dilution technique in the subarctic North Pacific Ocean along a west–east transect during summer 1999. Average phytoplankton growth rates without added nutrients (μ₀) were 0.33, 0.41, 0.20 and 0.49 d⁻¹ for the four regions sampled: the Western Gyre, the Bering Sea, the Gulf of Alaska gyre and stations along the Aleutian Trench. Average grazing mortality rates (m) were 0.34, 0.27, 0.20 and 0.49 d⁻¹. Limitation of phytoplankton growth by macronutrients, such as NO₃ and SiO₂, was identified only at a few stations, with overall μ₀/μ_n (μ_n is nutrient-enhanced growth rate) averaging 0.9. Phytoplankton growth and microzooplankton grazing were approximately balanced, as indicated by high m/μ₀ ratio, except in the Bering Sea, where the m/μ₀ ratio was 0.65, indicating the relative importance of the diatom-macrozooplankton grazing food chain and possible higher export flux to the deep layer. Flow cytometric analysis revealed that the growth rates of picoplankton (Synechococcus and picoeukaryotes) were usually much lower than the total phytoplankton community growth rates estimated from chlorophyll a, except for stations in the Gulf of Alaska Gyre, where the growth rates for different populations were about the same. Lower than community-average growth rate for picoplankton indicates larger phytoplankters, presumably diatoms, were growing at a much faster rate. Suppressed phytoplankton growth in the Gulf of Alaska was probably a result of iron limitation.     

北太平洋冬季SST、风场及环流对淡水强迫的响应

通过海气耦合模式CCSM3(The Community Climate System Model version 3),研究在北大西洋高纬度淡水强迫下,北太平洋冬季的海表温度SST、风场及流场的响应及其区域性差异。结果表明:淡水的注入使北太平洋整体变冷,但有部分区域异常增暖;在太平洋东部赤道两侧,SST的变化出现北负南正的偶极子型分布。阿留申低压北移的同时中纬度西风减弱,热带附近东北信风增强。黑潮和南赤道流减弱,北太平洋副热带逆流和北赤道流增强,日本海被南向流控制。风场及流场的改变共同导致了北太平洋SST异常出现复杂的空间差异:北太平洋中高纬度SST的降温主要由大气过程决定,海洋动力过程主要影响黑潮、日本海及副热带逆流区域的SST,太平洋热带地区SST异常由大气与海洋共同主导。     

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.     

中国第三次北极科学考察走航路线上空黑碳气溶胶的观测研究

2008年7月至9月,中国第3次北极科学考察期间,在走航路线上利用黑碳仪对黄海-日本海-鄂霍次克海-西北太平洋-白令海-楚科奇海-加拿大海盆等海区上的黑碳气溶胶浓度进行连续观测,最北观测位置达85°21.3′N.观测结果显示,北冰洋是全航线黑碳浓度最低的海区,平均浓度为(5.3±3.7)ng/m3;在70°N以北的海区...     

Observation of Algal Bloom in the Northwest Arabian Sea Using Multisensor Remote Sensing Satellite Data

Algal bloom observed using Indian Remote Sensing Satellite IRS-P4 Ocean Color Monitor (OCM) derived chlorophyll images during December 23, 2003–January 8, 2004, off the Oman coast. High chlorophyll concentration (～20 mg m^?3) patches were observed. MODIS-Aqua data of January 1, 2004, were analyzed to generate normalized water leaving radiance (nLw) images for seven visible channels: 412, 443, 488, 531, 551, 667 and 678 nm. The channels 667 and 678 nm showed interesting algal bloom features. The bloom features were detected in OCM image of January 2, 2004, using Subramanian's Trichodesmium detection Protocol. MODIS-Aqua retrieved Sea Surface Temperature (SST) around the bloom patches was observed to be >240°C. The OCM chlorophyll mean observed to be very high (>10.0 mg m^?3) in two bloom pockets. Quickscat scatterometer derived wind speed was found to be optimum in the range of 3–5 m/sec.     

Dianeutral mixing,transformation and transport of the deep water of the Indian Ocean

The realization of North Atlantic Deep Water (NADW) replacement in the deep northern Indian Ocean is crucial to the “conveyor belt” scheme. This was investigated with the updated 1994 Levitus climatological atlas. The study was performed on four selected neutral surfaces, encompassing the Indian deep water from 2000 to 3500 m. The Indian deep water comprises three major water masses: NADW, Circumpolar Deep Water (CDW) and North Indian Deep Water (NIDW). Since NADW flowing into the southwest Indian Ocean is largely blocked by the ridges (the Madagascar Ridge in the east and Davie Ridge in the north in the Mozambique Channel) and NIDW is the only source in the northern Indian Ocean that cannot provide a large amount of volume transport, CDW has to be a major source for the Indian deep circulation and ventilation in the north. Thus the question of NADW replacement becomes that of how the advective flows of CDW from the south are changed to be upwelled flows in the north—a water-mass transformation scenario. This study considered various processes causing motion across neutral surfaces. It is found that dianeutral mixing is vital to achieve CDW transformation. Basin-wide uniform dianeutral upwelling is detected in the entire Indian deep water north of 32°S, somewhat concentrated in the eastern Indian Ocean on the lowest surface. However, the integrated dianeutral transport is quite low, about a net of 0.2 Sv (1 Sv=10⁶ m³ s^-1) across the lowermost neutral surface upward and 0.4 Sv across the uppermost surface upward north of 32°S with an error band of about 10–20% when an uncertainty of half-order change in diffusivities is assumed. Given about 10–15% of rough ridge area where dianeutral diffusivity could be about one order of magnitude higher (10^-4 m² s^-1) due to internal-wave breaking, the additional amount of increased net dianeutral transport across the lowest neutral surface is still within that error band. The averaged net upward transport in the north is matched with a net downward transport of 0.3 Sv integrated in the Southern Ocean south of 45°S across the lowermost surface. With the previous works of You (1996. Deep Sea Research 43, 291–320) in the thermocline and You (Journal of Geophysical Research) in the intermediate water combined, a schematic dianeutral circulation of the Indian Ocean emerges. The integrated net dianeutral upwelling transport shows a steady increase from the deep water to the upper thermocline (from 0.2 to 4.6) north of 32°S. The dianeutral upwelling transport is accumulated upward as the northward advective transport provided from the Southern Ocean increases. As a result, the dianeutral upwelling transport north of 32°S can provide at least 4.6 Sv to south of 32°S from the upper main thermocline, most likely to the Agulhas Current system. This amount of dianeutral upwelling transport does not include the top 150–200 m, which may contribute much more volume transport to the south.     

Phytoplankton composition and its ecological effect in subsurface cold pool of the northern Bering Sea in summer as revealed by HPLC derived pigment signatures

CHEMTAX analysis of high-performance liquid chromatography(HPLC) pigment was conducted to study phytoplankton community structure in the northern Bering Sea shelf, where a seasonal subsurface cold pool emerges. The results showed that fucoxanthin(Fuco) and chlorophyll a(Chl a) were the most abundant diagnostic pigments, with the integrated water column values ranging from 141 to 2 160 μg/m2 and 477 to 5 535 μg/m2, respectively. Moreover, a diatom bloom was identified at Sta. BB06 with the standing stock of Fuco up to 9 214 μg/m3. The results of CHEMTAX suggested that the phytoplankton community in the northern Bering Sea shelf was dominated by diatoms and chrysophytes with an average relative contribution to Chl a of 80% and 12%, respectively, followed by chlorophytes, dinoflagellates, and cryptophytes. Diatoms were the absolutely dominant algae in the subsurface cold pool with a relative contribution exceeding 90%, while the contribution of chrysophytes was generally higher in oligotrophic upper water. Additionally, the presence of a cold pool would tend to favor accumulation of diatom biomass and a bloom that occurred beneath the halocline would be beneficial to organic matter sinks, which suggests that a large part of the phytoplankton biomass would settle to the seabed and support a rich benthic biomass.     

Water transport from the North-east Irish Sea to western Scottish coastal waters: Further observations from time-trend matching of Sellafield radiocaesium

Radiocaesium isotopes, discharged into the North-east Irish Sea from the Sellafield (formerly Windscale) nuclear fuel reprocessing plant in Cumbria, have been employed as flow monitors to update and extend the record of coastal water movement from the Irish Sea to the Clyde Sea area and, further north, to Loch Etive. The temporal trends in radiocaesium levels have been used to determine the extent of water mixing en route and to define mean advection rates. Flow conditions from the Irish Sea have changed considerably since the mid-1970s, the residence time of northern Irish Sea waters being ～12 months during 1978–1980 inclusive. Average transport times of four and six months are estimated for the Sellafield to Clyde and Sellafield to Etive transects respectively. Sellafield ¹³⁷Cs levels in seawater were diluted by factors of 27 and 50 respectively during current movement to the Clyde and Etive areas. The decrease in salinity-corrected ¹³⁷Cs concentrations between the Clyde and Etive suggests that dilution by Atlantic water occurs, the latter mainly entering the Firth of Lorne from the west. The majority (～94%) of the radiocaesium supply to Loch Etive enters the Firth of Lorne via the portion of the coastal current circulating west of Islay, only ～6% arriving via the Sound of Jura.