Salinity Fields Research Articles

Volumetric Characterization of the South Atlantic Subtropical Mode Water Types

AbstractTime series (2002–2018) of a global monthly objectively analyzed fields of temperature and salinity were used to investigate the South Atlantic subtropical mode water (SASTMW). It is characterized as homogeneous layers in the temperature range of 13 to 16 °C and with low potential vorticity. Three different types of SASTMW were distinguished allowing us to evaluate their temporal volumetric variation. Each type has its distinct spatial and temporal distribution patterns and consequently dissimilar volumetric variation. This variability is seen in the volume anomaly and turnover time of each type. To examine these differences we compared two rates: the water formation in a given temperature range due to heat flux and the mode water formation. The first (13.1±2.4 Sv) is higher than the second (10.2±2.0 Sv), showing that although heat flux is essential for the formation of SASTMW, there are other factors that influence each type differently.

Three-dimensional thermohaline anomaly structures of rings in the Kuroshio Extension region

Using AVISO satellite altimeter observations during 1993–2015 and a manual eddy detection method, a total of 276 anticyclonic rings and 242 cyclonic rings shed from the Kuroshio Extension (KE) were identified, and their three-dimensional (3D) anomaly structures were further reconstructd based on the Argo float data and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) cruise and buoy data through an interpolation method. It is found that the cyclonic (anticyclonic) rings presented consistent negative (positive) anomalies of potential temperature; meanwhile the relevant maximum anomaly center became increasingly shallow for the cyclonic rings whereas it went deeper for the anticyclonic rings as the potential temperature anomaly decreased from the west to the east. The above deepening or shoaling trend is associated with the zonal change of the depth of the main thermocline. Moreover, the composite cold ring between 140° and 150°E was found to exhibit a double-core vertical structure due to the existence of mode water with low potential vorticity. Specifically, a relatively large negative (positive) salinity anomaly and a small positive (negative) one appeared for the composite cyclonic (anticyclonic) ring at the depth above and below 600 m, respectively. The underlying driving force for the temperature and salinity anomaly of the composite rings was also attempted, which varies depending on the intensity of the background current and the temperature and salinity fields in different areas of the KE region, and the rings’ influences on the temperature and salinity could reach deeper than 1 000 m on average.

Numerical modelling of suspended-sediment transport in a geographically complex microtidal estuary: Sydney Harbour Estuary, NSW

A numerical study was conducted to investigate the sediment dynamics in a geographically complex estuary, the Sydney Harbour Estuary (SHE). The SHE is a good example of a microtidal estuary, with irregular shorelines and a complex bathymetry, characterized by many headlands and islands forming a meandering main channel. Horizontal sediment transport showed a local estuarine turbidity maximum (ETM) as a result of complex topography, independent of salinity fields and river flows during dry weather. The along-estuary advection of sediment was mainly driven by the mean advection, with a minor contribution by tidal pumping. Mean advection associated with barotropic forcing drives sediment flux seaward in the upper estuary and landward in the middle estuary, leading to a longitudinal convergence of sediment transport, without upstream or downstream migration of ETM during high river flows. The interactions between tidal currents, complex topography and asymmetric vertical mixing led to spring-neap and flood-ebb variations in sediment distribution. The Singular Spectrum Analysis (SSA) method was used to calculate the relative contributions of the identified environmental forcing frequencies (tidal range, tidal frequency, river discharges, wind stress) to the variability in suspended-sediment concentration. Tidal frequency and river discharges were the major contributors to this variability. Tidal range made the highest contribution in the middle estuary, where the ETM was located, driving the spring-neap cycle of the ETM.

Physiological characterization of a pepper hybrid rootstock designed to cope with salinity stress

In pepper crops, rootstocks that tolerate salt stress are not used because available commercial rootstocks offer limited profits. In this context, we obtained the hybrid NIBER®, a new salinity-tolerant rootstock that has been tested under real salinity field conditions for 3 years with 32%–80% higher yields than ungrafted pepper plants. This study aimed to set up the initial mechanisms involved in the salinity tolerance of grafted pepper plants using NIBER® as a rootstock to study root-shoot behavior, a basic requirement to develop efficient rootstocks. Gas exchange, Na+/K+, antioxidant capacity, nitrate reductase activity, ABA, proline, H2O2, phenols, MDA concentration and biomass were measured in ungrafted plants of cultivar Adige (A), self-grafted (A/A), grafted onto NIBER® (A/N) and reciprocal grafted plants (N/A), all exposed to 0 mM and 70 mM NaCl over a 10-day period. Salinity significantly and quickly decreased photosynthesis, stomatal conductance and nitrate reductase activity, but to lower extent in A/N plants compared to A, A/A and N/A. A/N plants showed decreases in the Na+/K+ ratio, ABA content and lipid peroxidation activity. This oxidative damage alleviation in A/N was probably due to an enhanced H2O2 level that activates antioxidant capacity to cope salinity stress, and acts as a signal molecule rather than a damaging one by contributing a major increase in phenols and, to a lesser extent, in proline concentration. These traits led to a minor impact on biomass in A/N plants under salinity conditions. Only the plants with the NIBER® rootstock controlled the scion by modulating responses to salinity.

Characteristics and vertical structure of oceanic mesoscale eddies in the Bay of Bengal

The signatures of mesoscale eddies induced surface and subsurface changes have not been comprehensively quantified for the Bay of Bengal (BoB) region. This study quantifies the statistical properties and three-dimensional (3D) eddy structures in the BoB. To accomplish this, the satellite altimetry data combined with automated eddy detection and tracking algorithm is used. Horizontal distribution of surface characteristics of eddies is analyzed by using 24 years (1993–2016) of AVHRR infrared satellite sea surface temperature (SST) and 7 years (2010–2016) of sea surface salinity (SSS) of SMOS satellite data. Surface eddy centric composite analysis reveals the existence of warm (cold) and diverse SSS anomalies for anticyclonic (cyclonic) eddies. During winter, it is important to note that the eddy induced SST and SSS anomalies show the dipole patterns show opposite phases for the cyclonic and anticyclonic eddies. Observed diploe structures are consistent with the eddy rotation and background large-scale meridional gradient of temperature and salinity fields. The 3D structure of eddies is investigated by using the ARMOR3D and Argo float profiles. The horizontal distribution of temperature and salinity anomalies from ARMOR3D signify the monopole structure of eddies in the subsurface layers. Further, the analysis of composite averages of 241 (200) Argo temperature profiles indicates the core of anticyclonic (cyclonic) eddies centered at about ∼140 m (∼100 m). However, salinity profiles depict the existence of core at ∼65 m (∼50 m). This study have practical relevance to a variety of stakeholders and finds profound importance in the validation of eddy-resolving ocean models for the BoB region.

Mediterranean overflow water in the North Atlantic and its multidecadal variability

The Mediterranean overflow water is one of the most important intermediate-depth water masses in the North Atlantic. To investigate its properties a pre-industrial simulation with the earth system model EC-Earth is used. The multidecadal variability of the outflow is analysed by examining the modelled volume and salt transports through the Strait of Gibraltar as well as different atmospheric patterns (such as the wind pattern and the net freshwater fluxes). The salinity evolution in the main core of the outflow in the mid-Atlantic is also taken into account. The leading empirical orthogonal functions for the modelled salinity 900 m coincided with the modelled distribution of outflow water. The associated principal component showed a multidecadal variability of the salinity field. The variability of the net salt transport through the Strait of Gibraltar showed a similar behaviour where the Atlantic-Mediterranean system manifested two clear states. One of these is when the Mediterranean imports salt from the Atlantic and the other is where salt export to the Atlantic predominates. This result indicates that the Mediterranean Sea acts as a storage of salt alternating between the two states. The negative phase of the North Atlantic oscillation appears to play a role driving the variability of the salt transport and its impact on the overturning circulation in the North Atlantic.

Black Sea Intrapycnocline Lenses according to the Results of a Numerical Simulation of Basin Circulation

The exact scenario of the propagation of highly saline Marmora Sea waters in the Black Sea basin is not clear. Together with river runoff, they form the prevailing haline stratification of the basin. One regime of their propagation can be the formation of lenses similar to highly salted and warm lenses of the Mediterranean Sea water in the Atlantic Ocean basin. The purpose of this study is the numerical modeling and subsequent analysis of these dynamic structures that form in the Black Sea due to water exchange through the Bosphorus strait. In this case, the main difficulty is the need for high spatial resolution in the strait. The paper provides a brief description of the NEMO ocean-modeling framework used and the features of configuration that make it possible to reproduce the circulation in the basins of the Azov, Black, and Marmara seas with a spatial resolution of 1.16 km. Fields from the ERA5 atmospheric reanalysis are used as the atmospheric forcing. The numerical experiment carried out by us allows reproducing a typical structure of the seasonal variability of the Black Sea rim current and the features of the vertical structure of the basin waters for the period of 2008–2009. The spatial resolution of the results of numerical modeling made it possible to accomplish a high-quality reconstruction of the saltwater dynamics in the basin and at the exit of the Bosphorus strait. Five lenses formed near the strait and captured by the rim current jet were simulated for the period of 2008–2009. They are well-pronounced in the seawater salinity field for the period of 1–2 months. Using one of the lenses as an example, it is shown that its core is located at a depth of about 75 m. The vertical size of the structure is almost 40 m and its horizontal scale is 15 km. The simulation results demonstrate that lens formation events are associated with the gain in the saltwater inflow after storms in the Sea of Marmara basin. Verifying the results of the study can be done based on a specialized field experiment in the Bosphorus region during the periods of the most probable formation of the Black Sea intrapycnocline lenses.

Hydrography of the Eastern Mediterranean basin derived from argo floats profile data

As the Eastern Mediterranean integrates different sub-basins with important hydrological features, during recent decades it has often become a target of study by the oceanographic community. The recent expansion of observational tools and methods in the marginal seas has allowed more enhanced studies of the oceanographic processes that dominate such areas. In this work, temperature and salinity profile data collected by Argo floats in the Eastern Mediterranean are analysed for the period 2004–2017. The spatio-temporal variability of the basin's physical properties, together with the depicted changes in the different sub-basins, is investigated in an attempt to construct the latest hydrographic picture of the region. The findings describe the dominant water masses and reveal a general positive trend in the basin's thermohaline properties. The inter-annual variability of the stored heat and salt, and their distribution in the water column, reveals strong climatic signals that are dominated by previously reported alternations of the general circulation and convection events in the area. The latter are correlated with the surface temperature and salinity fields and are traced within the area's different sub-basins. In the early period (2004–2010), data from Levantine and Ionian depict inter-annual variability of the upper layers salinity field that is correlated with previously reported alternations of the Levantine's circulation, and intermediate water production in the Ionian. During the latest period (2012–2017), when the data coverage is denser and more representative for the wider area of the Eastern Mediterranean, the Adriatic sub-basin presents intense dense water production activity while the Aegean Sea undergoes a relaxation period with significant variability at intermediate layers due to water mass exchanges.

THE METHOD FOR CALCULATIONS THE VERTICAL DISTRIBUTION OF THE FIELDS OF THERMOHALINE CHARACTERISTICS FOR THE BLACK SEA DEEP-WATER AREA BY REMOTE MEASUREMENTS DATA

Problem Statement and Purpose. The results of studies on the development of methods for calculations of the vertical distribution of temperature and salinity fields in the active layer of the Black Sea by remote measurements data was presents in article. To solve the many practical problems, it is necessary to use vertical distribution of hydrological characteristics of the marine environment. Today there isn't an easy way to get a in situ data for evaluation of the vertical distribution of these characteristics. Indirect definitions of the vertical distribution of water temperature and salinity through the development of various methods for the calculation of the vertical profile of water temperature are used to date.Main purpose of this work is to estimate an ability of using of satellite data for calculation of the spatial distribution of thermohaline characteristics (on the example of the Black Sea).Data & Methods. The initial data of the actual water temperature and salinity values were station data or measurement from the ship data (OSD – Ocean Station data), data measured with the help of floats (PFL – Profiling float data) and satellite data of the sea surface temperature.Calculations of the vertical distribution of temperature and salinity fields in the active layer of the Black Sea by remote measurements data are based on original methods developed by the State Institution “Hydroacoustics Branch of Institute of Geophysics of NAS of Ukraine”. The development of methods was based on mathematical, physical and statistical methods of calculation.Study of vertical distribution of water temperature and salinity in the Black Sea were carried out in the deep-water part sea at standard levels (0, 10, 20, 25, 30, 50 meters) in spring – autumn period.Results. In the process of research, the following tasks were solved: the possibility of calculating the speed of sound from the values of water temperature calculated on the basis of satellite information are estimated; the possibility of calculating the salinity of water by the values of water temperature, sound speed in water and hydrostatic pressure are estimated; a method for calculations the vertical distribution of the fields of thermohaline characteristics in the active layer of the Black Sea by remote measurements data has been developed.A prototype of a computer program for calculations the vertical distribution of temperature and salinity fields in the Black Sea based on remote measurements data has been developed. The program automatically determines where and by what equations the vertical distribution of the fields of thermohaline characteristics in the active layer of the Black Sea can be calculated.The initial data for the calculations are only daily satellite data of the sea surface temperature and the month of the year.Designed by us, the prototype of a computer program to calculate the vertical distribution of the fields of thermohaline characteristics in the active layer of the Black Sea based on the remote measurements could serve as a basis for the establishment of a "Operational Forecast System of the fields of thermohaline characteristics in the Black Sea based on the remote measurements" (OFS). With the help of which the dynamics of characteristics and effects of their change on hydrobiological, hydrochemical, hydrophysical processes in the Black Sea and the ecosystem of the sea in general can be evaluated.In our opinion the developed method for calculating of the vertical distribution of the fields of thermohaline characteristics by remote measurements data can be applied to others water area of the World Ocean taking into account their hydrological conditions.

ИССЛЕДОВАТЕЛЬ ЦИРКУЛЯЦИИ ВОД ИНДИЙСКОГО, АТЛАНТИЧЕСКОГО И ТИХОГО ОКЕАНОВ – К 90-ЛЕТИЮ А.Д. ЩЕРБИНИНА

This year we celebrate the 90th anniversary of the birth of Anatoly Dmitrievich Shcherbinin, a famous oceanologist, experimenter and veteran who kept the honor and created the glory of the Shirshov Institute of Oceanology of the Russian Academy of Sciences. Dr. Shcherbinin created the first climate Oceanographic Data Bank of the Indian Ocean, published a 12-volume atlas monograph of the fields of temperature, salinity, density, electrical conductivity and speed of sound, summarized in the monograph “Formation and Variability of Hydrophysical Fields of the Pacific and Atlantic Oceans”, as well as four thematic monographs in publishing house «Hydrometeoizdat». For these works, he was twice awarded the M.Yu. Shokalsky Prize.

LongRunMIP: Motivation and Design for a Large Collection of Millennial-Length AOGCM Simulations

AbstractWe present a model intercomparison project, LongRunMIP, the first collection of millennial-length (1,000+ years) simulations of complex coupled climate models with a representation of ocean, atmosphere, sea ice, and land surface, and their interactions. Standard model simulations are generally only a few hundred years long. However, modeling the long-term equilibration in response to radiative forcing perturbation is important for understanding many climate phenomena, such as the evolution of ocean circulation, time- and temperature-dependent feedbacks, and the differentiation of forced signal and internal variability. The aim of LongRunMIP is to facilitate research into these questions by serving as an archive for simulations that capture as much of this equilibration as possible. The only requirement to participate in LongRunMIP is to contribute a simulation with elevated, constant CO2 forcing that lasts at least 1,000 years. LongRunMIP is an MIP of opportunity in that the simulations were mostly performed prior to the conception of the archive without an agreed-upon set of experiments. For most models, the archive contains a preindustrial control simulation and simulations with an idealized (typically abrupt) CO2 forcing. We collect 2D surface and top-of-atmosphere fields and 3D ocean temperature and salinity fields. Here, we document the collection of simulations and discuss initial results, including the evolution of surface and deep ocean temperature and cloud radiative effects. As of October 2019, the collection includes 50 simulations of 15 models by 10 modeling centers. The data of LongRunMIP are publicly available. We encourage submissions of more simulations in the future.

Wind‐Driven Strain Extends Seasonal Stratification

AbstractThe onset and breakdown of stratification are key physical drivers of phytoplankton growth in shelf seas and the open ocean. We show how in the Celtic Sea, where seasonality in stratification is generally viewed as controlled by heat input, a cross‐shelf salinity gradient horizontally strained by the wind prolonged the stratified period by 5–6 days in autumn prior to full winter mixing, while in spring caused seasonal stratification to begin 7 days early. Salinity straining has important implications for setting light conditions during the start of the spring bloom and for the timing of bottom‐water ventilation in winter. Analysis of winds around the time of likely onset of spring stratification between 1979 and 2016 showed that in 60% of the years' wind conditions were favorable for salinity straining. Accurate knowledge of the horizontal salinity field and wind stress are required to correctly determine the onset and breakdown of stratification.

Marmara Sea waters with the Mediterranean origin in the formation of the salinity and dynamics fields in the Black Sea

The peculiarities of the bottom of the central basin of the Black Sea are specified, and four depression zones with maximum depths of 2170, 2210, 2171 and 2140 m were allocated for the first time, as well as the positions of the focuses of maximum salinity in the Black Sea water column in a long-term climatic plan. The presence of three foci of maximum salinity in the water column, which are connected with the bottom depressions in the central Black Sea basin, and two similar foci which are located in the coastal areas of the sea (SW ― the Bosphorus and SE ― the Batumi-Trabzon area), was determined with the field of factual average annual salinity. In the fields of salinity extremes, there are 4 foci of maximum salinity in the central basin of the sea and two ones in the SW and SE sea coastal areas. The nature of their occurrence and permanent existence was explained by the entry of highly salted Marmara Sea waters of Mediterranean origin into the bottom layers of the Black Sea and their further intrusion from the depths to the surface because there are no other sources of high-saline waters. The up-welling vertical movements that occur during the intrusion of water from the depths into the overlying layers are interacted with the Coriolis force and are led to the formation of horizontal cyclonic circulation in high salinity cupolas. This process develops and exists in the entire water column.The differences are established in the vertical distribution of average and extreme salinity. Well-defined disturbances caused by water mixing processes are traced in the curves of salinity extremes: in the field of minimal salinity they are located at horizons from 300 to 1200 m with the formation of even a homogeneous layer of water at depths of 500―600 m; in the field of maximum salinity, a abrupt decrease in the gradient at the horizon of 400―500 m, as well as the formation of a homogeneous layer of water at depths of 800―1000 m.

A 3D-hydrodynamic model for predicting the environmental fate of chemical pollutants in Xiamen Bay, southeast China

Simulation model is very essential for predicting the environmental fate and the potential environmental consequences of chemical pollutants including those from accidental chemical spills. However very few of such simulation model is seen related to Chinese costal water body. As the first step toward our final goal to develop a simulation model for the prediction and the risk assessment of chemical pollutants in Chinese coastal water, this study developed a three-dimensional (3D) hydrodynamic model of Xiamen Bay (XMB). This hydrodynamic model was externally derived by meteorological data, river discharge and boundary conditions of XMB. We used the model to calculate the physical factors, especially water temperature, salinity and flow field, from June to September 2016 in XMB. The results demonstrated a good match between observations and simulations, which underscores the feasibility of this model in predicting the spatial-temporal concentration of chemical pollutants in the coastal water of XMB. Longitudinal salinity distributions and the mixing profile of river-sea interactions are discussed, including the obvious gradation of salinity from the river towards sea sites shown by the model. We further assumed that 1000 kg and 1000 mg/L of a virtual chemical pollutant leaked out from Jiulong River (JR) estuary (point source) and whole XMB (non-point source), respectively. The model illustrates that it takes three months for XMB to become purified when point source pollution occurs in the estuary, while half a year to be required in the case of non-point source pollution across the entire bay. Moreover, the model indicated that pollutants can easily accumulate in the western coastal zone and narrow waters like Maluan Bay, which can guide environmental protection strategies.

ОСОБЕННОСТИ РАСПРОСТРАНЕНИЯ СЕВЕРОМОРСКОЙ ВОДЫ В БОРНХОЛЬМСКОМ БАССЕЙНЕ ПО РЕЗУЛЬТАТАМ МОДЕЛИРОВАНИЯОСОБЕННОСТИ РАСПРОСТРАНЕНИЯ СЕВЕРОМОРСКОЙ ВОДЫ В БОРНХОЛЬМСКОМ БАССЕЙНЕ ПО РЕЗУЛЬТАТАМ МОДЕЛИРОВАНИЯ

With the help of mathematical modeling, the features of the distribution of North Sea waters in the Bornholm basin are considered on the example of a large inflow occurring in January 2003. For better resolution of bottom processes in the bottom density flow model, the computational domain is split vertically into bottom and overlying areas. In the lower region with a thickness of 20 m, the vertical grid spacing is 1 m. The basic equations of the model are transformed for each of the regions using σ-coordinate. According to the simulation results, the features of the distribution of North Sea water are highlighted, as well as the associated change in the salinity field in the overlying layer. Estimates of the possible influence of runoff currents on the distribution of North Sea waters are obtained.

Analysis of Ocean Tide‐Induced Magnetic Fields Derived From Oceanic In Situ Observations: Climate Trends and the Remarkable Sensitivity of Shelf Regions

AbstractTidal motion of oceanic salt water through the ambient geomagnetic field induces periodic electromagnetic field signals. Amplitudes of the induced signals are sensitive to variations in electrical seawater conductivity and, consequently, to changes in oceanic temperature and salinity. In this paper, we computed and analyzed time series of global ocean tide‐induced magnetic field amplitudes. For this purpose, we combined data of global in situ observations of oceanic temperature and salinity fields from 1990–2016 with data of oceanic tidal flow, the geomagnetic field, mantle conductivity, and sediment conductance to derive ocean tide‐induced magnetic field amplitudes. The results were used to compare present day developments in the oceanic climate with two existing climate model scenarios, namely, global oceanic warming and Greenland glacial melting. Model fits of linear and quadratic long‐term trends of the derived magnetic field amplitudes show indications for both scenarios. Also, we find that magnetic field amplitude anomalies caused by oceanic seasonal variability and oceanic climate variations are 10 times larger in shallow ocean regions than in the open ocean. Consequently, changes in the oceanic and therefore the Earth's climate system will be observed first in shelf regions. In other words, climate variations of ocean tide‐induced magnetic field amplitudes are best observed in shallow ocean regions using targeted monitoring techniques.

Analysis of hydrophysical fields in the northern part of the Black Sea on the basis of assimilation in the hydrodynamic model of temperature and salinity observations in the summer season of 2016

A numerical experiment was conducted to reconstruct the fields of the currents, the level, temperature and salinity of the Black Sea for the summer season of 2016 on the basis of the hydrodynamic model that included nonlinear equations of motion, advection equations of heat and salt. We used a high spatial resolution (horizontal grid ∼1.6 ×1.6 km and 27 vertical layers) and real atmospheric forcing. The assimilation procedure of observational data was based on a modified Kalman filter taking into account the heterogeneity and non-isotropy of estimates of the temperature and salinity fields. Areas of generation of meso- and submesoscale features of hydrophysical fields were determined in the northern part of the Black Sea (eddies of different signs of rotation with a radius of about 30 km in the western part of the region, a cyclonic eddy with a radius of about 40 km in the eastern deep-water part of the region, anticyclonic eddy with a radius of about 25 km near the city of Yalta, intense jets along the Crimean coast and eddies of small scales of a different sign of rotation along the coast of Crimea and on the north-western shelf) and possible reasons of their formation were discussed.

The impact of various types of open boundary conditions in numerical simulation of the Black Sea coastal circulation

An important problem is to obtain a short-term forecast in the Black Sea coastal zone with a high resolution. It is solved on the basis of numerical modeling of ocean circulation. Carrying out simulations that allow reproducing the meso- and submesoscale processes in a reasonable machine time requires a considerable computational power. One of the common ways to solve this problem is to create a regional configuration (a nested domain). This work is performed to study the influence of methods of specifying open boundary conditions. To conduct such a study, a regional configuration corresponding to the southern coast of Crimea with a resolution of 1.5 km is developed. Four short-term numerical experiments are carried out to investigate the influence of various types of open boundary conditions on the simulation results. The results of the simulations have shown that for a correct reproduction of the hydrophysical parameters, barotropic velocities at the open border should not be taken into account. At the open boundary, in the fields of temperature and salinity, there is no numerical noise when using a flow relaxation scheme. The sea level is reproduced correctly when using a Flather-type scheme.

Reconstruction of the mesoscale variability of the Black Sea based on assimilation in the model of three-dimensional fields of pseudo-measurements of temperature and salinity

The paper presents the results of the analysis of the hydrophysical fields of the Black Sea, reconstructed in the reanalysis through the assimilation in the model of pseudo-measurements of temperature and salinity. Much attention was paid to assessing the reproduction of mesoscale eddies. To perform a retrospective analysis of hydrophysical fields, three-dimensional temperature and salinity fields obtained by the original method of joint analysis of data on sea-level anomalies and rare contact measurements were acquired in the model. To identify the eddy structures, an automatic identification procedure is used, based on the definition of closed streamlines in the velocity fields. The coordinates of the eddy, trajectories of motion, velocity, time of life and vertical structure are calculated.

Heat, water and solute transfer in saline loess under uniaxial freezing condition

Salt weathering of loess slopes in the seasonally frozen region is closely related to water and salt migration induced by temperature gradient. This paper carried out uniaxial freezing tests on sodium sulfate saline loess with three temperature gradients considered. Visible cracks are developed in the frozen domain during testing while little change noted in lower unfrozen part. The lower the cold-end temperature, or the higher the temperature gradient, the less developed cracks emerge. At higher temperature gradients, the freezing front descends more rapidly, corresponding to higher freezing rates and larger maximum frozen depths. Synchronous variations were found in water and salinity profiles, with peak values near the frozen fringe. An improved Harlan model was then established for heat-water transfer in freezing soils, incorporating an impedance factor. Considering the convection and diffusion of solute, the models for salinity field were proposed based on Darcy’s and Fick’s law. Numerical simulations were carried out on the coupled heat-water-solute transfer in freezing saline loess columns. Comparisons of calculated and measured data prove the rationality of the models. Finally, dynamic changes of unfrozen water content and the influence of freezing point on thermal regime, water and salinity profiles were discussed.