Pelitic matter differentiation in seas and oceans

Pelitic matter is subjected to differentiation at any depth. Filter feeding organisms just accelerate sedimentation of fine particles and do not affect their distribution at the bottom, thus, passively reflecting the content of pelitic fractions in suspended matter.     

Simulating large-scale circulation in seas and oceans

The problem of simulating ocean general circulation is considered using an approach developed by G.I. Marchuk. Most attention is focused on problems associated with the application of multi-component-splitting and adjoint-equation methods and with the parameterization of turbulent-exchange processes. The statement of the problem, an algorithm of its solution, and the results of the four-dimensional temperature and salinity data assimilation in a model of World Ocean hydrodynamics are discussed. This algorithm yields qualitatively reliable results, and its main features are modularity, usability, and the possibility of using efficient implicit schemes.     

利用气候态水文数据Hydrobase II分析北欧海深层水的分布与输运

Deep water in the Nordic seas is the major source of Atlantic deep water and its formation and transport play an important role in the heat and mass exchange between polar and the North Atlantic. A monthly hydrological climatology—Hydrobase II—is used to estimate the deep ocean circulation pattern and the deep water distribution in the Nordic seas. An improved P-vector method is applied in the geostrophic current calculation which introduces sea surface height gradient to solve the issue that a residual barotropic flow cannot be recognized by traditional method in regions where motionless level does not exist. The volume proportions, spatial distributions and seasonal variations of major water masses are examined and a comparison with other hydrological dataset is carried out. The variations and transports of deep water are investigated based on estimated circulation and water mass distributions. The seasonal variation of deep water volume in the Greenland Basin is around 22×103 km3 whereas significantly weaker in the Lofoten and Norwegian Basins. Annual downstream transports of about 1.54×103 and 0.64×103 km3 are reported between the Greenland/Lofoten and Lofoten/Norwegian Basins. The deep water transport among major basins is generally in the Greenland-Lofoten-Norwegian direction.     

On the transport of water masses by long-period waves in seas and oceans

Parallel with the traditional hypotheses on the predominantly wind (Ekman), gradient, and thermohaline nature of large-scale currents in seas and oceans, there exist hypotheses on the participation of long-period waves in the formation of these currents. As the physical mechanisms of generation of currents by waves, one can mention nonlinear wave transport and the phenomenon of negative viscosity in waves. From the viewpoint of existence of these mechanisms, numerous scientists explain high velocities of jet currents and their stable character. The predominant role of winds and thermohaline processes in the formation of large-scale currents is also accepted. On the basis of the experimental data, we demonstrate additional possibilities for the formation of large-scale currents given by the transport of water masses by long-period waves.Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 24–34, September–October, 2004.This revised version was published online in May 2005 with corrections to cover date.     

A classification of hydrological climatic seasons in the China seas

By using a method of boundary temperature index of seasons, a classification of hydrological climatic seasons in the China seas is made on the basis statistics of the sea surface air and water temperatures over the years. The results indicate that the assignment of hydrological seasons in the China seas differs with various sea areas. It may be divided into three climatic belts. In the temperate zone area, four seasons are clearly distinct with very long winter. While in the subtropical zone area, there is no winter throughout the year. The autumn is linked together with the spring, and the summer is unusually long. As for the tropical zone area, it is summer all the year round without any other seasons. In addition , the regular pattern of transformation of the four seasons and the regional characteristics of the length of each season are analyzed in greater detail. The results are in agreement with the continental seasonal classification and it is also shown that the results are reasonable and reliabl     

Problems of operational data assimilation for marginal seas

Operational models based on the system of equations of geophysical thermohydrodynamics of the marine medium are considered, as are methods for an approximate reconstruction of the main geophysical fields from the data of deep-sea thermohaline measurements. The results of calculations for the White, Barents, and Kara seas are presented.     

Assimilation of climatic hydrological data in a Black-Sea model based on the algorithm of adaptive statistics of prognostic errors

We propose an algorithm of adaptive statistics of prognostic errors aimed at the assimilation of the climatic temperature and salinity fields in a model of dynamics of the sea. The algorithm is used for the numerical solution of the proposed differential equations for the dispersions of prognostic errors of temperature and salinity. The sources in the equations of advective diffusion of heat and salt depend on the four-dimensional dispersions of prognostic errors and one-dimensional (along the vertical coordinate) dispersions of measurement errors. The dispersions of prognostic errors are corrected at the times of assimilation of the data. We perform the reconstruction and analysis of the climatic fields of currents in the Black Sea. It is shown that the structure of the fields of dispersions in the upper mixed layer is determined by the vertical diffusion. Below this layer, the distribution of dispersions depends on the vertical advection. The algorithm of adaptive statistics of prognostic errors allows us to reconstruct the improved mutually adapted hydrophysical parameters with regard for the dynamics of the dispersions of errors. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 26–37, January–February, 2008.     

Fragmentation in high seas fisheries: Preliminary reflections on a global oceans governance approach

Notwithstanding the wide range of actions taken to strengthen the legal regime of international fisheries, overexploitation and the risk of depletion of stocks have been strong concerns for decades. Indeed, the regime of international fisheries law is currently not rooted in sustainability, and it does not adequately take into consideration the impact of fishing activities on the wider marine environment. One of the main causes lies in fragmentation of international fisheries law: a lack of coordination between instruments and institutions, and gaps in effective coherent structures for fisheries management. Areas beyond national jurisdiction (ABNJ), including the high seas, are particularly prone to this lack of coordination and integration.One alternative to reach a durable management of high seas fisheries might be found in a ‘global oceans governance approach’. This paper explores how this approach could impact the fragmented regime of fisheries. It suggests that governance-based perspectives underline concepts rooted in adaptability and interactions, concepts that suggest to approach international fisheries law not as a static set of rules but as an evolutive process. Reflecting on an overarching goal of coordination and possible management challenges in ABNJ provides an interesting starting point to develop a comprehensive understanding of the impacts of oceans governance on the fragmented legal regime of high seas fisheries. We now need to see how to give effect to governance, a task that remains, at this point, a work in progress.     

浙江近海潮汐潮流的数值模拟

用三维陆架海模式(HAMSOM)对浙江近海的潮汐、潮流进行了数值模拟,并采用网格嵌套和动边界技术对原模式作了改进,以提高计算的精度,改进后的模式在浙江近海的应用中被证明是成功的.沿岸50个潮位站计算与实测值的比较表明,加入动边界以后的小区域细网格计算较之粗网格以及未加动边界以前精度普遍提高,比较的均方差结果为:M₂分潮振幅差4.6cm,相角差7.14°;S₂分潮振幅差5.0cm,相角差5.4°;K₁分潮振幅差2.25cm,相角差5.76°;O₁分潮振幅差1.56cm,相角差5.5°,可见计算与实测符合良好.另外,选取了105个实测潮流点,比较了表层M₂和K₁分潮流调和常数分量Ucosξ,Usinξ,Vcosη,Vsinη的实测值与计算值的偏差,结果表明计算与实测的符合程度较好.在此基础上,给出了各主要分潮的潮位同潮图、潮流同潮图、潮汐性质、潮流性质、潮流椭圆和潮流的运动形式等,发现4个主要分潮M₂,S₂,K₁,O₁在本区内均未出现无潮点;M₂分潮流在29°18'N,122°46'E处有一个圆流点.此外还得到了一些有意义的结论,都与实测情况符合良好,从而对整个浙江沿海区域的潮汐潮流特性有了一个全面认识.     

A theoretical reason to expect inviscid western boundary currents in realistic oceans

The conventional picture of an ocean gyre, based on an ocean with vertical sidewalls, assumes a balance between an input of vorticity by wind stress curl, and a viscous flux of vorticity through the boundary at the same latitude, resulting from a viscous western boundary current which may be significantly modified by nonlinear terms. Potential interactions with topography are also commonly acknowledged as a possible complicating factor. In this idealized picture, the zonal momentum balance is taken to be geostrophic, as numerous model analyses confirm. A theoretical argument is given here which shows that, in an ocean with sloping sidewalls, this geostrophic balance results in bottom pressure torques which balance the wind stress curl at each latitude. This removes the requirement for a viscous western boundary current at each latitude suggesting that the dynamics within a western boundary current may be essentially inviscid. While inviscid western boundary currents have already been found in certain idealized systems, and in one set of diagnostics from an eddy permitting model, the generality of the argument presented here gives a strong reason to believe that these are not special cases. Inviscid western boundary currents are in fact the rule, and the vertical sidewall case is an unrealistic exception.     

Fine vertical structure of currents and hydrological elements in the Black Sea

Data on the fine vertical structure of currents and hydrological elements in the Black Sea, obtained through the use of a hydrophysical OLT profiler, are examined. Vertical exchange coefficients are evaluated, whose distribution is characterized by the occurrence of minima in the seasonal pycnocline and main halocline, a maximum in the core of the cold intermediate layer (CIL), and relatively steady values within the 300–500 m layer. The vertical exchange coefficient values, are consistent with the data acquired through other techniques, and the profiles of this parameter vertically are more detailed.Translated by Vladimir A. Puchkin.     

Assimilation of simulated float data in Lagrangian coordinates

We implement an approach for the accurate assimilation of Lagrangian data into regional general ocean circulation models. The forward model is expressed in Lagrangian coordinates and simulated float data are incorporated into the model via four-dimensional variational data assimilation. We show that forward solutions computed in Lagrangian coordinates are reliable for time periods of up to 100 days with phase speeds of 1 m/s and deformation radius of 35 km. The position and depth of simulated floats are assimilated into the viscous, Lagrangian shallow water equations. The weights for the errors in the model and data are varied and the assimilation results react appropriately. We show the effect of different spatial and temporal samplings of float data on all Lagrangian trajectories in the computational domain. At the end of the assimilation period, results from the Lagrangian shallow water equations could be interpolated and used as initial and boundary conditions in an Eulerian general ocean circulation model.     

Assimilation of historical SST data for long-term ENSO retrospective forecasts

In this study, the assimilation of historic SST (sea surface temperature) data was performed for long-term ENSO hindcasts. The emphasis was placed on the design of background error covariance (BEC) that dominates the transfer of SST information to the subsurface. Four different data-assimilation schemes, based on Optimal Interpolation (OI) algorithm, were proposed, and compared in terms of ENSO simulation and prediction skills for the period from 1876 to 2000.It was found that the data-assimilation scheme that has a three-dimensional BEC constructed from model simulations forced by observed wind stress can effectively correct the second-layer temperature in the SST assimilation and lead to the best ENSO prediction skill. Further analysis for the long-term hindcasts shows that the prediction skills have a striking decadal/interdecadal variability similar to that found in other models. These results provide a fundamental basis for the further study of ENSO predictability.     

Chaotic magnetic patterns in marginal seas and small ocean basins have similar origin to structural magnetic quiet zones in deep oceans

The empirical observation is made that marginal seas which have spread orthogonal to their margins have clearly defined lineated magnetic anomaly patterns, while marginal seas which have spread at acute angles to their margins have chaotic or subdued magnetic anomaly patterns.Deep ocean basins which have acute angles between their margins and their spreading directions generate magnetic patterns that are also chaotic (magnetic quiet or smooth zones), due to a geometrically controlled MOR structure consisting of many small spreading-segments connected by many small-offset FZ. Magnetization of such a complex structure by reversals of the Earth's magnetic field produces a magnetic pattern having many small magnetic domains juxtaposed, half with normal and half with reversed polarity. The FZ offsets cause blocks of one polarity to be surrounded on all sides by blocks of opposed polarity, and both their small size and close proximity results in sea-surface magnetometers recording magnetically subdued or chaotic area.Marginal sea basins having margins acutely angled to the spreading direction, can also be explained as structural magnetic quiet zones.     

The dynamic method of calculating currents and analysis of the vertical kinematic structure

The basic relations of the classical dyamic method have been complemented with the condition allowing for the non-monotonicity of the vertical kinematic structure. The elements of the multi-layered system of geostrophic currents have been found to correlate over depth with seawater density and hydrostatic pressure distribution. An example of the analysis of the vertical structure of currents, involving specific hydrological data, is given. Translated by Vladimir A. Puchkin.     

Assimilation of sea surface temperature in the Northwest Pacific Ocean and its marginal seas using the ensemble Kalman filter

Satellite-borne sea surface temperature (SST) data were assimilated with the ensemble Kalman filter (EnKF) in a Northwest Pacific Ocean circulation model to examine the effect of data assimilation. The model domain included the northwestern part of the Pacific Ocean and its marginal seas, such as the Yellow Sea and East/Japan Sea. The performance of the data assimilation was evaluated by comparing the simulated ocean state with that observed. Spatially averaged root-mean-squared errors in the SST and sea surface height (SSH) decreased by 0.44 °C and 4 cm, respectively, by the assimilation. The results of the numerical experiments substantiated the effectiveness of the SST assimilation via the EnKF for all marginal seas, as well as the Kuroshio region. The benefit of the data assimilation depended on the characteristics of each marginal sea. The variation of the SST in the East/Japan Sea and the Kuroshio extension (KE) region were improved 34% and those in the Yellow Sea 12.5%. The variation of the SSH was improved approximately 36% in the KE region. This large improvement was achieved in the deep-water regions because assimilation of SST data corrected the separation point of the western boundary currents, such as the Kuroshio and the East Korea Warm Current, and the associated horizontal surface currents. The SST assimilation via the EnKF also improved the subsurface temperature profiles. The effectiveness of SST assimilation was seasonally dependent, with the improvement being relatively larger in winter than in summer, which was related to the seasonal variation of the vertical mixing and stratification in the ocean surface layer.     

中国近海ASCAT和ERA-Interim风场资料的评估

利用中国近海23个浮标对2015年一整年的ASCAT轨道风场和ERA-Interim再分析风场进行质量评估,并对比了ERA-Interim和CFSV2两种再分析风场资料在中国近海的适用性。结果表明:ASCAT在中国近海与浮标风速的一致性优于ERA-Interim,而二者与浮标风向的一致性则相差不大。同时,对比CFSV2与ERA-Interim的误差统计结果发现,CFSV2的风速误差较ERAInterim略小,风向误差相差不大。     

Assimilation of surface currents into a regionalmodel over Qingdao coastal waters of China

Surface currents measured by high frequency （HF） radar arrays are assimilated into a regional ocean model over Qingdao coastal waters based on Kalman filter method. A series of numerical experiments are per- formed to evaluate the performance of the data assimilation schemes. In order to optimize the analysis pro- cedure in the traditional ensemble Kalman filter （ENKF）, a different analysis scheme called quasiensemble Kaman filter （QENKF） is proposed. The comparisons between the ENKF and the QENKF suggest that both them can improve the simulated error and the spatial structure. The estimations of the background error covariance （BEC） are also assessed by comparing three different methods： Monte Carlo method; Canadian quick covariance （CQC） method and data uncertainty engine （DUE） method. A significant reduction of the root-mean-square （RMS） errors between model results and the observations shows that the CQC method is able to better reproduce the error statistics for this coastal ocean model and the corresponding external forcing. In addition, the sensibility of the data assimilation system to the ensemble size is also analyzed by means of different scales of the ensemble size used in the experiments. It is found that given the balance of the computational cost and the forecasting accuracy, the ensemble size of 50 will be an appropriate choice in the Qingdao coastal waters.     

Evaluation of tidal error in altimetry data in the Asian marginal seas

The magnitude and geographical distribution of the error in the Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO) altimetry data associated with tidal correction around Asian marginal seas has been revealed. The errors were evaluated by harmonic analysis of the AVISO corrected sea surface heights data (CorSSH). Errors of more than 15 cm of tidal correction were recognized in the western and northern parts of the Yellow Sea, Celebes Sea, Kuril Islands, and the northwestern part of the Okhotsk Sea. It was found that the CorSSH and sea level anomaly (SLA) data downloaded from the AVISO are not available for direct use in those marginal seas. To reduce the tidal correction error, the harmonic constants calculated from the latest tide model and regional tide model were applied as the tidal correction of the Altimetry data. The tidal errors in the Yellow Sea and the northwestern part of the Okhotsk Sea were reduced by approximately 20 cm and 10 cm, respectively. Root mean square differences between the harmonic constants derived from tide models and those derived from altimetry data were calculated. The root mean square differences were large in the Yellow and the Okhotsk Seas. Root sum squares for four principal tidal constituents in the Yellow and East China Seas and Okhotsk Sea were 7.72 cm and 8.36 cm, respectively.