Seasonal and daily variation of mercury evasion at coastal and off shore sites from the Mediterranean Sea

Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hg_extr / H', Hg_extr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March–April 2004 and October–November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hg_extr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600–1150%) was observed during the summer. The spring showed the lowest variation (260–360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500–1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P.S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air–sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(1):373–387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m^− 2 h^− 1. The summer value was estimated to 22.3 pmol m^− 2 h^− 1 and the spring to 7.6 pmol m^− 2 h^− 1. Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons.     

Seasonal variation in the three-dimensional structures of coastal thermal front off western Guangdong

The seasonal structure and dynamic mechanism of oceanic surface thermal fronts(STFs) along the western Guangdong coast over the northern South China Sea shelf were analyzed using in situ observational data, remote sensing data, and numerical simulations. Both in situ and satellite observations show that the coastal thermal front exhibits substantial seasonal variability, being strongest in winter when it has the greatest extent and strongest sea surface temperature gradient. The winter coastal thermal front begins to appear in November and disappears after the following April. Although runoff water is more plentiful in summer, the front is weak in the western part of Guangdong. The frontal intensity has a significant positive correlation with the coastal wind speed,while the change of temperature gradient after September lags somewhat relative to the alongshore wind. The numerical simulation results accurately reflect the seasonal variation and annual cycle characteristics of the frontal structure in the simulated area. Based on vertical cross-section data, the different frontal lifecycles of the two sides of the Zhujiang(Pearl) River Estuary are analyzed.     

Seasonal and inter-annual variation of mesozooplankton in the coastal upwelling zone off central-southern Chile

Zooplankton sampling at Station 18 off Concepción (36°30′S and 73°07′W), on an average frequency of 30 days (August 2002 to December 2005), allowed the assessment of seasonal and inter-annual variation in zooplankton biomass, its C and N content, and the community structure in relation to upwelling variability. Copepods contributed 79% of the total zooplankton community and were mostly represented by Paracalanus parvus, Oithona similis, Oithona nana, Calanus chilensis, and Rhincalanus nasutus. Other copepod species, euphausiids (mainly Euphausia mucronata), gelatinous zooplankton, and crustacean larvae comprised the rest of the community. Changes in the depth of the upper boundary of the oxygen minimum zone indicated the strongly seasonal upwelling pattern. The bulk of zooplankton biomass and total copepod abundance were both strongly and positively associated with a shallow (<20 m) oxygen minimum zone; these values increased in spring/summer, when upwelling prevailed. Gelatinous zooplankton showed positive abundance anomalies in the spring and winter, whereas euphausiids had no seasonal pattern and a positive anomaly in the fall. The C content and the C/N ratio of zooplankton biomass significantly increased during the spring when chlorophyll-a was high (>5 mg m⁻³). No major changes in zooplankton biomass and species were found from one year to the next. We concluded that upwelling is the key process modulating variability in zooplankton biomass and its community structure in this zone. The spring/summer increase in zooplankton may be largely the result of the aggregation of dominant copepods within the upwelling region; these may reproduce throughout the year, increasing their C content and C/N ratios given high diatom concentrations.     

Seasonal variations in temperature,salinity and density in the southern coastal waters of the Caspian Sea

Variability in water temperature, salinity and density was investigated based on field measurements near Anzali Port, in the Southern Caspian Sea in 2008. Seasonal changes of seawater properties were mainly observed through the upper 100 m layer, while below this layer seasonal variations of the parameters were minor. Vertical structure of the temperature in the southern coastal waters of the Caspian Sea is characterized by a significant seasonal thermocline between 20–50 m depths with vertical variation in temperature about 16°C in midsummer (August). Decrease of the thermocline occurs with the general cooling of the air and sea surface water, and deepening of the mixed layer during late of autumn and winter. Seasonal averages of the salinity were estimated in a range of 12.27–12.37 PSU. The structure of thermocline and pycnocline indicated agreement between changes of temperature and density of seawater. Seasonal pycnocline was observed in position of the thermocline layer.     

Seasonal variations of the deep-sea macrobenthos communities in the coastal and bathyal zones off sanriku,northeastern Japan

Seasonal variations of macrobenthos communities were analyzed over six years at two fixed stations at the depths of 500 m and 1,000 m in the bathyal zone off Sanriku, northeastern Japan, and were compared with those of the 80 m station established at the mouth of Otsuchi Bay, northeastern Japan. Significant seasonal variations of macrobenthos density were detected at the 80 m and 500 m stations. While the density increased in late spring and decreased until July at the 80 m station, it increased between May and August, and decreased in September at the 500 m station. At the 1,000 m station, no seasonal variation of macrobenthos abundance could be detected. The seasonal variations of the density observed at the 80 m and 500 m stations are probably related to that of the supply of organic materials derived from surface phytoplankton. Differences in the patterns of seasonal variations among the three stations may reflect the different periods of food supply to the sea floor. Significant seasonal variation in the feeding structure of the polychaete communities could be detected at the 80 m and 1,000 m stations.     

安达曼海中尺度涡季节变化分析

利用 AVISO 提供的中尺度涡数据集,对1993–2019年间安达曼海中尺度涡的涡旋特征、运动规律及其季节变化机制进行统计分析。结果显示,27年间安达曼海共出现中尺度涡328个,其中反气旋涡（171个）多于气旋涡（157个）,主要分布在中西部盆地深水区。涡旋平均寿命为46.4 d,平均半径为111.8 km,平均振幅为4.7 cm,平均最大转速为24.8 cm/s,平均移动速度为15.0 cm/s,反气旋涡的平均半径、振幅和转速均大于气旋涡,而移动速度小于气旋涡。涡旋的半径、振幅和最大转速在其生命周期中都经历了先增大后减小的过程,移动速度则先减小后增大。在季节变化方面,反气旋涡和气旋涡性质冬夏对比呈现“跷跷板”现象,即夏季气旋涡比反气旋涡更多更强更大,冬季则反气旋涡更多更强更大;涡旋分布位置,夏季从北向南呈“气旋–反气旋–气旋”的极性反转交替分布,冬季则与之相反。动力机制分析显示,背景流场涡度可能影响安达曼海涡旋极性交替分布,正（负）涡度背景流利于气旋（反气旋）涡存在。涡旋能量变化机制显示,风强迫是安达曼海涡旋主要能量来源,风场能量输入与涡旋动能的季节变化吻合。     

Seasonal Variations in the Sea off Sanriku Coast, Japan

The temperature and salinity data obtained by the Iwate Fisheries Technology Center for the 25-year period from 1971 to 1995 were analyzed to clarify the seasonal variations in the sea off Sanriku, Japan. The variations of three typical waters found in this region, the Tsugaru Current water, the Oyashio water, and the Kuroshio water are discussed in terms, of a T-S scatter diagram referring to the water mass classification proposed by Hanawa and Mitsudera (1986). The mean temperature and salinity fields averaged for each month show clear seasonal variation. Distributions of the Tsugaru Current water and the Oyashio water can barely be distinguished in the fields deeper than 200 m since the Tsugaru Current has a shallow structure; however, the fields at 100 m depth indicate remarkable seasonal variation in the area of the Tsugaru Current. At 100 m depth, the temperature and salinity fronts between the Tsugaru Current water and the Oyashio water gradually disappear in January through April, appear again in May, then become clearest in September. This revised version was published online in July 2006 with corrections to the Cover Date.     

Seasonal variation of mesoscale eddy intensity in the global ocean

Mesoscale eddies are a prominent oceanic phenomenon that plays an important role in oceanic mass transport and energy conversion. Characterizing by rotational speed, the eddy intensity is one of the most fundamental properties of an eddy. However, the seasonal spatiotemporal variation in eddy intensity has not been examined from a global ocean perspective. In this study, we unveil the seasonal spatiotemporal characteristics of eddy intensity in the global ocean by using the latest satellite-alti...     

Reprint of “Seasonal and daily variation of mercury evasion at coastal and off shore sites from the Mediterranean Sea”

Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hg_extr / H', Hg_extr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March–April 2004 and October–November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hg_extr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600–1150%) was observed during the summer. The spring showed the lowest variation (260–360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500–1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P.S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air–sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(1):373–387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m^− 2 h^− 1. The summer value was estimated to 22.3 pmol m^− 2 h^− 1 and the spring to 7.6 pmol m^− 2 h^− 1. Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons.     

山东半岛东部近岸表层沉积物放射性核素的季节性变化及其环境指示意义

基于2019年4月、7月、10月、12月渤黄海共享航次取得山东半岛东部近岸H01和H02站位多个季节沉积物样品,通过低本底γ能谱仪分析得到其表层沉积物放射性核素7Be、210Pbex、228Thex和 137Cs活度数据。结果表明,短半衰期核素7Be、228Thex与长半衰期核素210Pbex、137Cs在同一站位的季节分布存在差异,同一核素在H01和H02站位的季节分布也存在差异;H01站位的7Be和228Thex,H02站位的210Pbex和137Cs,受表层沉积物粒度影响较不明显,7Be和228Thex的季节变化受悬浮物质的输运和沉降的影响显著,而210Pbex和137Cs更多指示的是环流作用下的沉积物再分配;与H02相比,H01站位表层沉积物核素变化受大气沉降影响较低。H01和H02站位分别位于“Ω”形泥质体顶部和东部边缘,其物源和沉积动力环境存在差异,放射性核素7Be、210Pbex、228Thex和137Cs在示踪物质输运和沉降过程中具有重要意义。     

Observation of temperature and velocity in the coastal water off Kuala Terengganu,Malaysia

Mooring observation of current and temperature was made at 17.8 m layer of 19 m depth about 8 km east to Kuala Terengganu, Peninsular Malaysia. Harmonic analysis was applied to tidal currents for 30 days in September 1993, and to the tides observed at Chendering. The K1 tide was the largest both in tidal currents and the tides. Daily mean temperature, currents, sea level, and winds were analyzed from September 1993 to May 1994. Northeast Monsoon from December to February caused sea level rise of 50 cm and temperature lowering of 1°C.     

Seasonal variations of water temperature and salinity in Osaka Bay

The characteristics of seasonal variations of water temperature, salinity and density in the upper, middle and lower layers in Osaka Bay are described. Osaka Bay is considered to be an estuary, because the weak mixed state appears in spring and summer and the moderate mixed state in autumn and winter. Osaka Bay is divided into three areas, the eastern shallow area that has a large amplitude of seasonal variation of water temperature and low average salinity, the southwestern deep area which has small amplitude of seasonal variation of water temperature and high average salinity, and the northwestern deep area, which has small amplitude of seasonal variation of water temperature and low average salinity.     

Seasonal and areal variation of continental aerosol in the surface air over the western North Pacific region

Weekly aerosol samples were collected for two years from 1981 at six stations in the western North Pacific region. The samples were analyzed for aluminum to determine the mineral dust concentration in the air. By combining our data with observations in the central and eastern North Pacific by a US research group, the following results and conclusions have been obtained. Spring peaks in atmospheric mineral dust were observed at all the stations accompanied byKosa episodes (hazes due to mineral dust of Chinese origin). The spring peaks, however, varied from year to year. The mean concentration of mineral dust depends not only on the distance from the Asian coast but also on the latitude of the sampling station. The half-decrease distance of the atmospheric mineral dust turned out to be 500–600 km for all latitudes in the western North Pacific. This indicates that the rate of deposition of mineral dust in the western North Pacific is much larger than that in the central and eastern North Pacific.     

浙南沿岸海表面温度分布特征

文章根据浙南沿岸3个海洋观测站大陈、坎门、南麂站51a(1960-2010年)SST观测资料,进行统计分析,得出SST时空分布特征.结果表明,浙南沿岸的SST总体呈现北低南岛的趋势,冬季南北差异最小,夏季南北差异最大:51a年浙南沿岸SST总体呈现上升趋势,上升速率为0.017℃/a:SST变化存在3.5 a、5～6a...     

Co-variation of the surface wind speed and the sea surface temperature over mesoscale eddies in the Gulf Stream region:momentum vertical mixing aspect

The co-variation of surface wind speed and sea surface temperature (SST) over the Gulf Stream frontal region is investigated using high-resolution satellite measurements and atmospheric reanalysis data. Results show that the pattern of positive SST-surface wind speed correlations is anchored by strong SST gradient and marine atmospheric boundary layer (MABL) height front, with active warm and cold-ocean eddies around. The MABL has an obvious transitional structure along the strong SST front, with greater (lesser) heights over the north (south) side. The significant positive SST-surface wind-speed perturbation correlations are mostly found over both strong warm and cold eddies. The surface wind speed increases (decreases) about 0.32 (0.41) m/s and the MABL elevates (drops) approximate 55 (54) m per 1℃ of SST perturbation induced by warm (cold) eddies. The response of the surface wind speed to SST perturbations over the mesoscale eddies is mainly attributed to the momentum vertical mixing in the MABL, which is confirmed by the linear relationships between the downwind (crosswind) SST gradient and wind divergence (curl).     

浙南沿岸海表面温度分布特征(英文)

文章根据浙南沿岸3个海洋观测站大陈、坎门、南麂站51a(1960～2010年)SST观测资料,进行统计分析,得出SST时空分布特征。结果表明,浙南沿岸的SST总体呈现北低南高的趋势,冬季南北差异最小,夏季南北差异最大;51a年浙南沿岸SST总体呈现上升趋势,上升速率为0.017°C/a;SST变化存在3.5a、5a～6a、2a～7a及11a左右的振荡周期;SST主要由年循环分量决定,谐波拟合效果良好。     

Seasonal variation of atmospheric coupling with oceanic mesoscale eddies in the North Pacific Subtropical Countercurrent

This study investigated the seasonal variation in the atmospheric response to oceanic mesoscale eddies in the North Pacific Subtropical Countercurrent (STCC) and its mechanism, based on satellite altimetric and reanalysis datasets. Although mesoscale eddy in the study area is more active in summer, the sea surface temperature (SST) anomaly associated with mesoscale eddies is more intense and dipolar in winter, which is largely due to the larger background SST gradient. Similarly, the impact of the oceanic eddy on sea surface wind speed and heat flux is strongest in winter, whereas its effect on precipitation rate is more significant in summer. The study revealed that the SST gradient in STCC could impact the atmosphere layer by up to 800 hPa (900 hPa) in boreal winter (summer) through the dominant vertical mixing mechanism. Moreover, the intensity of the SST gradient causes such seasonal variation in mesoscale air-sea coupling in the study region. In brief, a stronger (weaker) background SST gradient field in wintertime (summertime) leads to a larger (smaller) eddy-induced SST anomaly, thus differently impacting atmosphere instability and transitional kinetic energy flux over oceanic eddies, leading to seasonal variation in mesoscale air-sea coupling intensity.