Role of sea ice on satellite-observed chlorophyll-a concentration variations during spring bloom in the East/Japan sea     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

The relationship between the spring bloom along the Primorye coast and the sea ice of the Tatarskiy Strait in the northern region of the East/Japan Sea, a semi-enclosed marginal sea in the North Pacific, was investigated using the ten-year SeaWiFS chlorophyll-a concentration data and DMSP/SSMI sea ice concentration data from 1998 to 2007. Year-to-year variations in the chlorophyll-a concentrations in the spring were positively correlated with those of the sea ice concentrations in the Tatarskiy Strait in the previous winter with a correlation coefficient of 0.77. Abrupt increases in nutrients, essential for the spring bloom in the upper ocean during spring, were supplied from sea ice-melted waters. Time series of vertical distributions of the nutrients indicated that phosphate concentrations were extremely elevated in the upper ocean (less than 100 m) without any connection to high concentrations in the deep waters below. The water mass from sea ice provided preferable conditions for the spring bloom through changes in the vertical stratification structure of the water columns. Along-coast ratios of stability parameters between two neighboring months clearly showed the rapid progression of the generation of a shallow pycnocline due to fresh water originating from sea ice. This study addressed the importance of the physical environment for biogeochemical processes in semi-enclosed marginal seas affected by local sea ice.  相似文献   

Fate of three major rivers in the Bohai Sea: A model study   总被引：1，自引：0，他引：1  

Hao Liu 《Continental Shelf Research》2011,31(14):1490-1499

Huanghe (Yellow River), Haihe and Liaohe are three major rivers flowing into the Bohai Sea and account for more than 80% of the freshwater and land-drained material inputs annually. The fate of three rivers in the seawaters correlates with the transport and distribution of the riverine sediments and nutrients, and further exerts a profound influence on the local marine ecosystem dynamics. Therefore, the evolution of the river plumes under the influence of the freshwater buoyancy, the tidal forcing and the wind stress are examined using a three-dimensional primitive equation ocean circulation model, independently and jointly. It is found that both tide and wind stirring can deteriorate the stabilization of the water column caused by the freshwater buoyancy; however, the processes are different. The tide stirring originates from the seafloor due to the bottom friction as the tidal wave propagates into the shallow waters, and then the turbulent kinetic energy dissipates upward. On the other hand, the wind stirring proceeds in the up-down direction. The influences of different winds on the evolution of the river plumes are also examined. Since the situation of each river mouth is different, the wind influence is also distinct. At last, the fate of three major rivers driven by the combined tidal forcing and climatology winds is reproduced, and the simulated salinity distribution shows a reasonable agreement with that observed, meaning that the river plume evolution plays a crucial role in shaping the salinity distribution in BS.  相似文献   

基于INSTANT数据对ITF流出海峡海流的功率谱分析     

刘凯  孙照渤  杜岩 《热带海洋学报》2011,(6)

利用INSTANT(The International Nusantara Stratification and Transport,努沙登加拉层结及输运的国际联合观测计划)计划所测得的流场数据,研究了ITF(Indonesian Throughflow,印度尼西亚贯穿流)在主要流出海峡——龙目海峡(Lombok Strait)、翁拜海峡(Ombai Strait)和帝汶海峡(Timor Passage)随深度和时间的变化,并对表层和温跃层的流速进行了功率谱分析。研究发现,ITF流场在龙目和翁拜海峡表层有显著的年循环,在季风转换期间各个层次上海流都会出现反转,从印度洋流向海峡内;而帝汶海峡在300m以下出现反转流。3个海峡的表层流都以年周期为主,温跃层的流以半年变化为主,并且都有丰富的季节内变化。高频部分,除了在龙目海峡表层K1日潮占优外,各海峡均以M2半日潮为主。  相似文献   

Seasonal variations and trophic ecology of microzooplankton in the southeastern Arabian Sea     

C.R. Asha Devi  R. JyothibabuP. Sabu  Josia JacobH. Habeebrehman  M.P. PrabhakaranK.J. Jayalakshmi  C.T. Achuthankutty 《Continental Shelf Research》2010

The seasonal ecological response of microzooplankton in the southeastern Arabian Sea is presented. During the spring intermonsoon period, stratification and depletion of nitrate in the surface waters (nitracline was at 60 m depth) cause low integrated chlorophyll a (av. 19±11.3 mg m⁻²) and primary production (av. 164±91 mgC m⁻² d⁻¹). On the other hand, nutrient enrichment associated with coastal upwelling and river influx during the onset and peak summer monsoon resulted in high integrated chlorophyll a (av. 21±6 mg m⁻² and av. 29±21 mg m⁻², respectively) and primary production (av. 255±94 mgC m⁻² d⁻¹ and av. 335±278 mgC m⁻² d⁻¹, respectively). During all three periods, diazotropic cyanobacterium Trichodesmium erythraeum dominated in the nutrient depleted surface waters. A general increase in abundance of larger diatoms was evident in the surface waters of the inshore region during monsoon periods. The microzooplankton abundance was found to be significantly higher during the spring intermonsoon (av.241±113×10³ ind m⁻²) as compared to onset of summer monsoon (av. 105±89×10³ ind m⁻²) and peak summer monsoon (av.185±175×10³ ind m⁻²). Microzooplankton community during the spring intermonsoon was numerically dominated by ciliates while heterotrophic dinoflagellate was the dominant ones during the monsoon periods. The high abundance of ciliates during the spring intermonsoon could be attributed to the stratified environmental condition prevailed in the study area which favors high abundance of smaller phytoplankton and cyanobacteria, the most preferred food of ciliates. On the other hand, the dominance of heterotrophic dinoflagellates during the monsoon periods could be linked to their ability to graze larger diatoms which were abundant during the monsoon periods. The overall results show low abundance of microzooplankton in the eastern Arabian Sea during the monsoon periods mainly due to a decline in ciliates abundance. This decline during the monsoon periods could be the result of (a) low abundance of smaller phytoplankton and (b) high stock of mesozooplankton predators (av. 245 ml 100 m⁻³).  相似文献   

Flow resistance in the Great Belt,the biggest strait between the North Sea and the Baltic Sea     

Flemming Jakobsen  Ian Sehested Hansen  Niels-Erik Ottesen Hansen  Frank Østrup-Rasmussen 《Estuarine, Coastal and Shelf Science》2010

The Danish Straits are part of the transition area between the North Sea and the central Baltic Sea. More precisely, the Danish Straits connect Kattegat to the Arkona Basin and includes the relatively narrow and shallow sub-areas: Great Belt, Little Belt, Fehmarn Belt and Sound. The flow resistances in the straits are hydraulically determined by among other factors, the contractions, sills and stratification found in the straits. Close to the entrance to the Arkona Basin the Darss and Drogden Sills are located that trap inflowing dense water partially before it enters the central Baltic Sea. Hence, the resistances in the Danish Straits are of crucial importance for the stratification and ecosystems in the central Baltic Sea. The present work comprises calculations of flow resistance in the Great Belt based on measurements collected as part of the Great Belt Fixed Link investigations. The specific resistance in the Great Belt is determined to be an average of 41.2 × 10⁻¹² s² m⁻⁵, but it depends heavily on the interface position. When calculating long-term discharge time-series on the basis of the momentum equation it is advised to apply a seasonal varying resistance.  相似文献   

Spring phytoplankton bloom in the fronts of the East China Sea   总被引：2，自引：0，他引：2  

SeungHyun Son  Sinjae Yoo  Jae-Hoon Noh 《Ocean Science Journal》2006,41(3):181-189

Frontal areas between warm and saline waters of the Kuroshio currents and colder and diluted waters of the East China Sea (ECS) influenced by the Changjiang River were identified from the satellite thermal imagery and hydrological data obtained from the Coastal Ocean Process Experiment (COPEX) cruise during the period between March 1^st and 10^th, 1997. High chlorophyll concentrations appeared in the fronts of the East China Seas with the highest chlorophyll-a concentration in the southwestern area of Jeju Island (~2.9 mg/m³) and the eastern area of the Changjiang River Mouth (~2.8 mg/m³). Vertical structures of temperature, salinity and density were similar, showing the fronts between ECS and Kuroshio waters. The water column was well mixed in the shelf waters and was stratified around the fronts. It is inferred that the optimal condition for light utilization and nutrients induced both from the coastal and deep waters enhances the high phytoplankton productivity in the fronts of the ECS. In addition, the high chlorophyll-a in the fronts seems to have been associated with the water column stability as well.  相似文献   

The alpha/beta ocean distinction: A perspective on freshwater fluxes, convection, nutrients and productivity in high-latitude seas   总被引：3，自引：0，他引：3  

Eddy C. Carmack   《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2578

Stratification is perhaps the most important attribute of oceans with regards to climate and biology. Two simple aspects of the ocean's climate system appear to have a surprisingly important role in transforming waters that feed the global thermohaline circulation, dominating patterns of biogeochemical flux and establishing macroecological domains. First, largely because of meridional distillation (mainly due to the atmospheric transport of freshwater across the Isthmus of Panama) the North Pacific is fresher than the North Atlantic. Second, largely because of zonal distillation (e.g., warming and evaporation at low latitudes and poleward transport of latent heat and moisture by the atmosphere) the upper layers of subtropical seas are permanently stratified by temperature (N_T²=gαdT/dz>0; here called alpha oceans), while the upper layers of high-latitude seas are permanently stratified by salinity (N_S²=gβdS/dz>0; here called beta oceans). The physical basis for the boundary separating alpha and beta oceans is unclear, but may lie in the thermodynamical equations published by Fofonoff [1961. Energy transformations in the sea. Fisheries Research Board of Canada, Report Series 109, 82pp]. Nevertheless, it is clear that the resulting thermohaline distributions establish a ‘downhill journey’ of low-salinity (and nutrient-rich) waters from the North Pacific to the Arctic and then into the North Atlantic. The Arctic Ocean—itself—acts a double estuary, whereby waters entering from the North Atlantic become either denser through cooling (negative estuary) or lighter by freshening (positive estuary) as they circulate within the basin and then return to the North Atlantic as a variety of components of the ocean's conveyor. Intermediate and deep waters generally form within cyclonic beta oceans in close proximity to alphas systems. Similar patterns of stratification, nutrients and biogeographical boundaries persist in the Southern Hemisphere. It is thus argued that this simple distinction—alpha versus beta oceans—provides a broad, conceptual framework for simple interpretation of key physical and biological processes and rates, including the impacts of climate variability.  相似文献   

Profiles of polar conductivities and of radon-222 concentration in the atmosphere by stable and labile stratification of surface layer     

A.I. Petrov  G.G. Petrova  I.N. Panchishkina 《Atmospheric Research》2009,91(2-4):206-214

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Use of major and selected trace elements to describe mixing processes in a water reservoir   总被引：1，自引：0，他引：1  

Nathalie Gassama  Constantin Cocirta  Haino Uwe Kasper 《Comptes Rendus Geoscience》2012,344(1):25-32

Data on temperature, major constituents and some trace elements, measured in the dissolved and particulate phases, were used to identify the hydrodynamics of a reservoir (the Bicaz reservoir, Romania). Results revealed that the reservoir experiences two thermal stratifications per year (summer and winter). However, the summer stratification is delayed by the high river inflow of June–July. Two layers were identified, a surface and a deep layer, whose location and impact vary with time. The surface layer originates from the river inflow (intrusion layer) and the deep current is produced by the outflow (velocity current). According to season, the river inflow either supplies the deep current or remains recordable up to the dam. Consequently, the structure of the water column, and thus the biogeochemical processes within it, are governed both by thermal stratification and by these layers.  相似文献   

Simulating seasonal to multi-decadal variation in lake thermal response to meteorological forcing using the UCLAKE 1-dimensional model code     

《Limnologica》2021

Lake temperature responses to climate forcing are of interest on account of the important linkages between water temperature and ecosystem processes. This paper describes a new 1-dimensional (1D) numerical model code and its application to investigations of multi-scale linkages between the vertical temperature structure and meteorological forcing. UCLAKE is implemented as highly portable open-source software, based on computationally efficient algorithms, and able to resolve sub-daily (e.g., hourly) dynamics while retaining the efficiency to simulate multi-decadal time scales.A UCLAKE model is calibrated and validated against thermistor profile time series for a small upland lake in North Wales, UK. Some of the challenges in 1D model calibration are explored and a sensitivity analysis reveals a dependence of optimal parameter set values on water column depth and time. An exploratory 52-year hindcast simulation demonstrates the computational efficiency of UCLAKE for multi-decadal studies of trends in lake temperature that vary with depth. A supplementary application of UCLAKE to Windermere, in the English Lake District, demonstrates its performance for larger and deeper lakes.  相似文献