Water Density Range Research Articles

Developing a Reactivity-Equivalent Physical Transformation to Simulate an Axially Heterogeneous Boiling Water Reactor

Hitachi is advancing their designs for a conceptual reactor called the resource-renewable boiling water reactor (RBWR), a concept reactor similar to the advanced boiling water reactor with a harder neutron spectrum. This design aims to minimise construction costs and waste production as well as to utilise separated plutonium and minor actinide fuel. However, the axial heterogeneity of the design poses calculation difficulties. The aim of this work is to use a known method, reactivity-equivalent physical transformation (RPT), for calculating fuel with double heterogeneity and apply it to a BWR-type fuel pin. This could reduce the calculation time needed for optimisation of the design of the RBWR. The objective of the study is to use SCALE 6.2 to produce an equivalent axial pin model by comparison with the burnup and neutron spectra of a radial model of the fuel. This model can then be used for 2D burnup calculations, and in future work will be used for the generation of two-group and multigroup cross-sections for further deterministic calculations as part of a two-step approach for analysis of the RBWR. The RPT method has been extensively tested on spherical fuel, and SCALE is a standard industry code. The initial radial model is a hexagonal assembly with 20% enriched UO2 fuel in a zircaloy cladding, surrounded by light water moderator. The derived axial model has a water density distribution taken from Hitachi’s RBWR designs. Criticality over 70 GWd/tU burnup is estimated using the model. The application of the RPT to the BWR pin was shown to be possible, but to have limitations with the introduction of additional radial complexity. For a single pin, excellent agreement between the radial and axial models could be found across a range of water densities, but in the case of an assembly level calculation distinct equivalence models were required for each water density. In addition, the produced RPT model is validated using SCALE’s 3D Monte Carlo module, KENO.

A Helical Monolayer Ice.

Understanding water wetting layers on solid surfaces is essential for many natural and industrial processes. Here we find a helical ice monolayer with every six water molecules helically arranged along the normal of the basal plane by performing an intensive structural search based on ab initio calculations. The helical ice is more stable than all previous models of monolayer and bilayer ices in a wide range of water densities both in vacuum and on weakly interacting substrates due to a stronger network of hydrogen bonds enabled by the helical geometry. More compelling is the fact that this model adequately explains a recent experimental ice monolayer grown on graphite in terms of the lattice parameter, water density, and Moiré pattern. The helical character in the new ice model echoes previously reported helical motifs in one-dimensional ice structures and suggests an unexpected capability of hydrogen bonds in driving the surface reconstruction of ice structures.

A folded ice monolayer.

A highly stable ice monolayer with folded structural motifs is predicted by means of a novel tiling method augmented with ab initio calculations. This ice monolayer has every two neighboring water hexamers connected by a water square yet folded into two distinct planes, and is thus coined as a folded ice model. It is in the ground state in a range of water densities from 0.08 to 0.12 Å-2, with a stronger energy preference at a lower water density. Its stability shown by ab initio molecular dynamics simulations can sustain up to a temperature of 100 K. The tiling method also enables the prediction of a family of considerably stable ice monolayers with a variety of puckered structures. These results enrich our knowledge of low-dimensional water structures and pave a way to explore more exotic ice nanostructures under confinements.

LOW-LINEAR ENERGY TRANSFER RADIOLYSIS OF SUPERCRITICAL WATER AT 400 °C: DENSITY DEPENDENCE OF THE G(•OH)

Monte Carlo simulations were used to predict the yield of primary specie • OH denoted as g ( • OH) that is formed from the radiolysis of pure, deaerat- ed supercritical water (SCW) (H 2 O) at 400 °C in the range of water density between ~0.15 and 0.6 g/ cm 3 . It is known that • OH, is one of the oxidizing species that significantly can increase the possibil- ity of various corrosion and material degradation as well. The thorough radiolysis processes in SCW - cooled reactor is not established currently, and it is believed to be a challenge in developing chemis- try control strategies for future Supercritical Water Reactor (SCWR). Since SCWR technology is now still under the conceptual design, hence there is only limited information published on the yields of radiolysis under these conditions. In this work, g ( • OH) was calculated at spur lifetime ( τ s / minimum time needed before the species within spur distributed homogeneously into the bulk solu- tion), 10 - 7 and 10 - 6 sec after the ionization event at all densities. From this work, it is shown that the data measured by other researcher at lower density ( 0.35 g/cm 3 ) is taken about near the spur lifetime. Finally, more experimental data are highly required in order to examine more thoroughly modeling calculation.

Radiolysis of Supercritical Water at 400°C: A Sensitivity Study of the Density Dependence of the Yield of Hydrated Electrons on the (eaq−+eaq−) Reaction Rate Constant

The temperature dependence of the rate constant (k) of the bimolecular reaction of two hydrated electrons (eaq−) measured in alkaline water exhibits an abrupt drop between 150°C and 200°C; above 250°C, it is too small to be measured reliably. Although this result is well established, the applicability of this sudden drop in k(eaq−+eaq−)) above ∼150°C to neutral or slightly acidic solution, as recommended by some authors, still remains uncertain. In fact, the recent work suggested that in near-neutral water the abrupt change in k above ∼150°C does not occur and that k should increase, rather than decrease, at temperatures greater than 150°C with roughly the same Arrhenius dependence of the data below 150°C. In view of this uncertainty of k, Monte Carlo simulations were used in this study to examine the sensitivity of the density dependence of the yield of eaq− in the low–linear energy transfer (LET) radiolysis of supercritical water (H2O) at 400°C on variations in the temperature dependence of k. Two different values of the eaq− self-reaction rate constant at 400°C were used: one was based on the temperature dependence of k above 150°C as measured in alkaline water (4.2×108 M−1 s−1), and the other was based on an Arrhenius extrapolation of the values below 150°C (2.5×1011 M−1 s−1). In both cases, the density dependences of our calculated eaq− yields at ∼60 ps and 1 ns were found to compare fairly well with the available picosecond pulse radiolysis experimental data (for D2O) for the entire water density range studied (∼0.15–0.6 g/cm3). Only a small effect of k on the variation of G(eaq−)) as a function of density at 60 ps and 1 ns could be observed. In conclusion, our present calculations did not allow us to unambiguously confirm (or deny) the applicability of the predicted sudden drop of k(eaq−+eaq−) at ∼150°C in near-neutral water.

Nuclear Safety of an RBMK Spent Fuel Pool

Aspects of the nuclear safety of the spent fuel pools of RMBK reactors under normal conditions and design basis and beyond design basis accidents are studied using a three-dimensional model verified by comparing with Monte Carlo calculations. It is shown that the storage of spent fuel assemblies in pencil-shaped cases secures nuclear safety in the entire range of water density, lattice spacing, and fuel burnup, i.e., in all, including hypothetical, emergency situations. For compact case-free storage, nuclear safety is secured in real scenarios where the water density changes upon disruption of heat removal or flooding of a dewatered pool. The disruption of the lattice spacing of compact storage in design basis, including seismic action, and beyond design basis accidents is examined. The conditions under which nuclear safety is secured are shown.

Interannual Variation of Annual Subduction Rate in the North Pacific Estimated from a Gridded Argo Product

AbstractSpatiotemporal variability of the subduction rate in the North Pacific from 2005 to 2012 is examined based on the Argo observational data. The subduction rate in the subtropical North Pacific varies significantly from year to year between 25 and 50 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1), and it is well correlated with the Pacific decadal oscillation. The temporal change of the subduction rate is largely determined by that of the late winter mixed layer depth through the lateral induction term. The increase (decrease) in the subduction rate in the subtropical mode water areas accompanies densification (lightening) of the mode density class of the subducted water. The subduction rate variability in the central mode water and eastern subtropical mode water regions is anticorrelated as found in the previous study using the output from an ocean GCM. The subduction rate in the central mode water density range changes dramatically, which is very large in 2005 and 2010 but almost disappears in 2009. The subduction rate variability in the western subtropical mode water regions seems to be correlated with the Pacific decadal oscillation with a lag of a few years.

An equation of state for predicting the thermodynamic properties and vapour–liquid partitioning of aqueous Ge(OH)4 in a wide range of water densities

Although germanic acid is an important compound in many engineering and natural aqueous environments, its exact stoichiometry, structure and stability are insufficiently known. To fill this gap, we combined theoretical quantum chemistry simulations of Ge speciation and structure with a recently developed equation of state for aqueous neutral species, applied to available experimental GeO2(s) solubility measurements. Results allow generation of a consistent set of thermodynamic properties of Ge(OH)4(aq) over a large T–P-fluid density range (298–900K, 0.1–300MPa, and 0.01–1.0gcm−3). These properties enable quantitative predictions of Ge transport and its fractionation from similar elements (e.g. Si) in aqueous vapour–liquid and supercritical fluid systems.

Habitat characterization of deep-water coral reefs in La Gaviera Canyon (Avilés Canyon System, Cantabrian Sea)

Surveys conducted at the complex Avilés Canyon System (southern Bay of Biscay) in order to identify vulnerable habitats and biological communities revealed the presence of noteworthy deep-water coral reefs in one of the tributaries of the system (La Gaviera Canyon). The aim of the present study is to determine why this deep-sea canyon provides suitable environmental conditions for corals to grow. This hanging canyon is characterized by an irregular U-shaped floor with two narrow differentiated flanks. Sand ripples and rocky outcrops structured in diverse W–E directed steps are observed on the canyon floor, suggesting intense hydrodynamic activity. Accordingly, high-frequency near-bottom current and thermal structure profiles showed that there occur strong shifts in currents/hydrography behaving as front-like features at each tidal cycle. These involve the sudden increase of along-axis velocities to over 50cm/s and vertical velocities of over 5cm/s in each tidal cycle associated with the passage of sharp thermal fronts and thermal inversions suggesting overturning. A year-long near-bottom current record showed events with near-bottom velocities well over 1m/s lasting for several days.Three cold-water coral settings were distinguished: a dense coral reef located on stepped rocky bottoms of the eastern and western flanks, carbonate mounds (20–30m high) located on the canyon floor, and a cluster of shallower water dead coral framework at the head sector of the canyon. Video and still images from a towed sled and ROV verified the presence of dropstones and rippled sand sheets surrounding the mounds and revealed changes in the coral population (alive or dead; total or patchy coverage) in coral reef and carbonate mound areas. The dominant species of the reef are Lophelia pertusa and Madrepora oculata, which considerably increase the habitat′s complexity and biodiversity in relation to other facies described in the canyon. The presence of living cold-water reefs is directly related to a high-energy environment at depths between 700 and 1200m in the levels between the lower bound of Eastern North Atlantic Central Water (ENACW) and the core of Mediterranean Water (MW). Such level matches the water density range σθ=27.35–27.65kgm−3 which has been identified as limits for cold-water coral distribution in the North Atlantic.

SU-GG-T-34: Effects of Target Replacement on Helical MVCT Images for Use in Adaptive Radiotherapy

Purpose: To investigate the effects of target replacement on helical mega‐voltage CT (MVCT) images for use in adaptive radiotherapy.Method and Materials:CT number to density tables were measured for three helical tomotherapy systems at two separate institutions. For each machine, MVCT images and measurements were acquired before and after their respective beam targets were replaced. Phantoms containing removable plugs having known physical densities between 0.6–1.8 g/cm3 were imaged on the helical tomotherapy imaging systems. Physical densities were collected from phantom specifications, and CT numbers were recorded from regions of interests consistently drawn within each phantom plug. Phantom and clinical MVCT images before and after the target replacements were compared. Results: For all three machines, target replacements affected CT number to density tables. In the density range of water, CT numbers before and after target replacement differed by 45, 105, and 56 HU for Machines A, B, and C, respectively. The post‐target replacement CT number to density tables for Machines A and B were extremely similar to each other. Images acquired after the target replacement showed qualitative improvements in image quality. Conclusion: The helical tomotherapy imaging system is affected by major hardware changes, which is evident from measured changes in CT number to density tables before and after a target replacement. If MVCT images are used for treatment planning, these images should be monitored with at minimum an equivalent quality assurance program as for conventional CT simulators. In order to reduce dosimetric uncertainties when using these images for treatment planning or adaptive radiotherapy, the integrity of the CT number to density table should be monitored more rigorously in the presence of machine repairs or instabilities.

Labrador Sea convection and subpolar North Atlantic Deep Water export in the SODA assimilation model

Labrador Sea convection was most intense and reached the greatest depths in the early 1990s, followed by weaker, shallower, and more variable convection after 1995. The Simple Ocean Data Assimilation (SODA) version 2.0.2/2.0.4 assimilation model is used to explore convective activity in the North Atlantic Ocean for the period from 1992 to 2007. Hydrographic conditions, which are relatively well observed during this period, are used to compare modeled and observed winter mixed-layer depths and water mass anomalies in relation to Deep Western Boundary Current transports and meridional overturning circulation (MOC) changes at the exit of the subpolar basin. The assimilation differs markedly from local observations in the March mixed-layer depth, which represents deep convection and water mass transformation. However, mean MOC rates at the exit of the subpolar gyre, forced by stratification in the mid-latitudes, are similar to estimates based on observations and show no significant decrease during the 1992–2007 period. SODA reproduces the deep Labrador Sea Water formation in the western North Atlantic without any clear indication of significant formation in the Irminger Sea while the lighter upper Labrador Sea Water density range is reached in the Irminger Sea in the 1990s, in agreement with existing assumptions of deep convection in the Irminger Sea and also supported by computed lag correlations with the Labrador Sea. Deep Water transformation mainly takes place in the eastern North Atlantic. The introduction of CFC-11 into the SODA model as a tracer reproduces the mean and multiyear variations of observed distributions.

Kinetic Study on Disproportionations of C1 Aldehydes in Supercritical Water: Methanol from Formaldehyde and Formic Acid

The reaction pathways and kinetics of C1 aldehydes, formaldehyde (HCHO) and formic acid (HCOOH=HOCHO), are studied at 400 degrees C in neat condition and in supercritical water over a wide range of water density, 0.1-0.6 g/cm3. Formaldehyde exhibits four reactions: (i) the self-disproportionation of formaldehyde generating methanol and formic acid, (ii) the cross-disproportionation between formaldehyde and formic acid generating methanol and carbon dioxide, (iii) the water-independent self-disproportionation of formaldehyde generating methanol and carbon monoxide, and (iv) the decarbonylation of formaldehyde generating hydrogen and carbon monoxide. The self- and cross-disproportionations overwhelm the water-independent self-disproportionation and the formaldehyde decarbonylation. The rate constants of the self- and cross-disproportionations are determined in the water density range of 0.1-0.6 g/cm3. The rate constant of the cross-disproportionation is 2-3 orders of magnitude larger than that of the self-disproportionation, which indicates that formic acid is a stronger reductant than formaldehyde. Combining the kinetic results with our former computational study on the equilibrium constants of the self- and cross-disproportionations, the reaction mechanisms of these disproportionations are discussed within the framework of transition-state theory. The reaction path for methanol production can be controlled by tuning the water density and reactant concentrations. The methanol yield of approximately 80% is achieved by mixing formaldehyde with formic acid in the ratio of 1:2 at the water density of 0.4 g/cm3.

Direct observation of cellulose dissolution in subcritical and supercritical water over a wide range of water densities (550–1000 kg/m3)

Direct observations of the heating of microcrystalline cellulose (230 DP) in water at temperatures up to 410 °C and at pressures up to 700 MPa were made with a batch-type microreactor. Cellulose particles were found to dissolve with water over temperatures ranging from 315 to 355 °C at high pressures. Dissolution temperatures depended on water density and decreased from about 350 °C at a water density of 560 kg/m3 to a minimum of around 320 °C at a water density of 850 kg/m3. At densities greater than 850 kg/m3, the dissolution temperatures increased and reached a value of about 347 °C at 980 kg/m3. The cellulose dissolution temperatures were independent of heating rates for values ranging from 10 to 17 °C/s. The low dependence of dissolution temperatures on the heating rates is strong evidence for simultaneous dissolution and reaction of the cellulose. Different phenomena occurred depending on water density. At low densities, particles turned transparent and seemed to dissolve into the aqueous phase from the surface. From 670 to 850 kg/m3, the cellulose particles visibly swelled just before completely collapsing and dissolving into the aqueous phase. The swelling probably increased water accessibility and particle surface area and thus lead to the lower dissolution temperatures observed. From 850 to 1000 kg/m3, the particles required longer times to dissolve and many fine brown-like particles were generated as the particles dissolved. FT-IR spectra of the residues were analyzed. Residues formed from heating cellulose at high densities still retained some cellulose character whereas those as low densities had little cellulose character, especially in the O–H stretching vibration region.

Molecular Dynamics Simulation Studies of the Limiting Conductances of MgCl2 and CaCl2 in Supercritical Water Using SPC/E Model for Water

We report results of molecular dynamics (MD) simulations of the limiting conductances of MgCl2 and CaCl2 in supercritical water as a function of water density using the SPC/E model for water. The limiting conductances of Mg2+, Ca2+ and Cl- over the whole range of water density considered exhibits a linear dependence of the limiting conductance on the water density. In the cases of Mg2+ and Ca2+, a solventberg picture for the behavior of small divalent cation emerges from our studies. From the view of the solventberg picture, the ion and its shell moving together as an entity interacts with the second hydration shell water molecules, and its mobility is restricted mostly by the number of the second hydration shell water which is proportional to the water density of the whole system. In the case of Cl-, the range of water density considered in this study belongs to the higher-density region (above 0.45 g/cm3) in which the effect of the number of hydration water molecules around ions dominated. As the water density increases, the water molecules of the first hydration shell restrict the mobility of Cl- and the limiting conductance of Cl- decreases nearly linearly. Significant different dependence on the water density is observed between the calculated limiting conductances of MgCl2 and CaCl2 at 673 K and the experimental results over the water density of 0.60–0.90 g/cm3. Possible limitation of the extended simple point charge (SPC/E) model with regard to this difference should be pointed out and the use of a more precise model like the revised polarizable (RPOL) model is indispensable for a further MD study to gain a complete picture of the chemical circumstance around the ions.

Kinetics of Water-Gas Shift Reaction in Supercritical Water

The kinetics of the water gas shift reaction was investigated in supercritical water using the Raman spectroscopic method for in situ quantitative measurement of reactants and relevant products in a stopped flow type reactor. The reaction proceeded according to the stoichiometric reaction as CO + H2O → CO2 + H2, whose rate was first order on the concentration of CO. The dependence on the reactant water was 1.5 ± 0.1 in the water density range from 4 to 25 mol dm–3 at a temperature of 380°C. The steady state concentration of formic acid was in the order of 10–4 against the initial concentration of CO and dependent on a 1.2 ± 0.3 order on the water density. These findings evidence that the rate determining step of the water gas shift reaction is the formation process of formic acid, which subsequently dissociates to CO2 + H2 at a much larger reaction rate. The slightly larger dependence than unity on the water density in the reaction rate as well as in the steady state concentration of the intermediate formic acid suggests that the transition state structure of the formic acid formation process resembles a certain kind of complex formed between a CO molecule and several water molecules such as suggested by Melius et al. (1990) by ab initio calculations.

Molecular Dynamics Simulation of Limiting Conductance for Na2+, Cl2−, Na°, and Cl° in Supercritical Water

We report results of molecular dynamics simulations of the limiting conductance of Na2+, Cl2−, Na°, and Cl° in supercritical water using the SPC/E model for water in conjuction with our previous study (Lee et al., Chem. Phys. Lett. 293, 289 (1998)). The behavior of the limiting conductances of Na2+ and Cl2− in the whole range of water density shows almost the same trend as those of Na+ and Cl−, but the deviation from the assumed linear dependence of limiting conductances of Na2+ and Cl2− on the water density is smaller than that of Na+ and Cl−. The ratio of the limiting conductance of the divalentions to that of the corresponding monovalentions over the whole range of water density is almost constant. In the cases of Na2+ and Cl2−, the dominating factor of the number of hydration water molecules around ions in the higher-density region and the dominating factor of the interaction strength between the ions and the hydration water molecules in the lower-density region are also found as was the cases for Na+ and Cl−. These factors, however, are not so strong as for the corresponding monovalent ions because the change in the energetics, structure, and dynamics are very small mainly due to the strong Coulomb interaction of the divalent ions with the hydration water molecules. The diffusion coefficient of Na° and Cl° monotonically increases with decreasing water density over the whole range of water density. The increase of the diffusion coefficient with decreasing water density is attributed only to the dramatic decrease of the hydration number of water in the first solvation shell around the uncharged species. Among the two important competing factors in the limiting conductance of Na+ and Cl−, the effect of the number of hydration water molecules around the uncharged species is the only existing factor over the whole range of water density since the interaction strength between the uncharged species and the hydration water molecules very small through the LJ interaction. This result has confirmed the dominating factor of the number of hydration water molecules around ions in the higher-density region in the explanation of the limiting conductance of Na+ and Cl− in supercritical water at 673 K.

Intermediate water mass production controlled by southern hemisphere winds

It is demonstrated that the production of intermediate water in a coarse resolution ocean general circulation model is controlled by Southern Hemisphere winds. Results from four equilibrium experiments using simplified topography and surface forcing are presented. The first experiment was carried out with no wind forcing, subsequent experiments employed annual mean surface stresses, which were amplified using factors of 0.5, 1, and 2.0 south of 30°S. In all experiments, the salinity minimum characteristic for intermediate water is reproduced. Volume transports are directly proportional to the applied Southern Hemisphere surface stresses. These force an increased export of intermediate water and heat into the South Pacific Ocean northward across 30°S and through Drake Passage into the South Atlantic Ocean. It results in a warming of the South Pacific Ocean, which is at a maximum in the intermediate water density range.

Decomposition of nitrobenzene in supercritical water

This work was conducted to extend the understanding of the reaction kinetics and mechanisms of nitrogen containing compounds in SCW. The main objectives were to investigate the reaction kinetics and pathways for the decomposition of nitrobenzene in SCW, and the fate of nitrogen upon the decomposition. The experimental conditions included the temperature range from 440 to 550°C and the supercritical water density range from 0.09 to 0.23 g ml −1. A continuous flow stirred tank reactor system and a batch reactor system were used for the decomposition experiments without and with oxygen, respectively. In the absence of oxygen, nitrobenzene decomposed in SCW to form primarily benzene and nitrite. The decomposition kinetics had an activation energy of 68.0 ± 9.0 kJ mol −1. Nitrobenzene concentration showed a weak effect on the decomposition kinetics whereas the density of SCW had no effect. Additional decomposition products such as carbon monoxide and carbon dioxide suggested the occurrence of oxidation driven possibly by the nitro-group as well as SCW. The oxidative role of the nitro-group was supported by the observation of the reduction of nitrite to nitrogen gas. The decomposition rate was substantially enhanced in the presence of oxygen. The oxidation yielded a number of aromatic reaction products including aniline, phenol, 2-(2-pyridinyl)-benzonitrile, and dibenzofuran. The nitrogen in the decomposed nitrobenzene appeared to form mainly nitrogen gas even in the oxidative environments.

The Eastern Boundary of the Subtropical North Atlantic

A quasi-meridional hydrographic section carried out between 60° and 20°N offshore from the European and African continental slopes is analyzed in terms of water masses and zonal transports in and out of the eastern boundary. Outstanding features of the meridional distribution of water masses are focused on, such as the transition between North Atlantic and South Atlantic Central Waters at 20°–25°N, the properties and anticyclonic circulation of the Rockall Channel mode water, and the northern boundary of the large-scale Mediterranean Water plume at about 50°N. An eastward transport of about 11×10 6 m 3 s −1 is found to enter the eastern boundary layer at densities lower than 27.25 and feed southward alongshore currents. The relation of the incoming transport to the water mass distribution and its eventual splitting into several outflowing components are discussed. Apart from the downward entrainment of upper water known to occur in the Gulf of Cadiz, there is no sign of the so-called “eastern boundary ventilation” mechanism in the central water density range. Yet a significant transport is found to escape the winter mixed layer toward the interior of the subtropical gyre, suggesting the horizontal southward currents across the sloping bottom of the mixed layer to be the main cause of ventilation at the eastern boundary.

The Water Masses of the Central North Atlantic in 1983—84

Abstract Hydrographic surveys carried out in 1983–84 along both sides of the Mid-Atlantic Ridge between 24° and 53°N provide a detailed description of the well-known North Atlantic water masses with particular emphasis on their meridional distribution and zonal dissymetry. In the upper layers the dense horizontal sampling resolves the several narrow Gulf Stream extensions into the ocean interior, giving the image, in the Central Water density range, of a mosaic of mode waters separated by fronts. At intermediate depths a vertical shear in the distributions of the Mediterranean Water and Labrador Sea Water stands out, both water masses having their lower part displaced southwards relative to their upper parts. Bottom waters containing nearly 20 percent of pure Antarctic Bottom Water are observed at 50°N in the eastern basin, in contrast with the western basin where proportions greater than 10 percent were found only south of 36°N along our section. This water mass analysis also gives indications that stron...