Changes In Water Volume Research Articles

Seasonal variation in pans in relation to limno-chemistry, size, hydroperiod, and river connectivity in a semi-arid subtropical region

Seasonal pans are hydrologically dynamic, with significant changes in water volume and depth in response to high evaporation, infiltration rates and inundation events. Intra-seasonal and inter-seasonal changes in endorheic and floodplain pans in relation to limnology, size, hydroperiod, and river connectivity were studied over two rainfall seasons across 36 pans at the Save Valley Conservancy. In the study region, floodplain pans were identified as pans that had connectivity with the Save River, while the endorheic pans (large and small) were hydrologically isolated basins. Seasonal trends for physico-chemical variables were initial low and gradual increased for both rainfall seasons. Significant inter-seasonal differences for several physico-chemical variables were observed. No significant differences in physico-chemical variables were observed between large and small endorheic pans, with the except for vegetation cover, which was higher in large pans. Floodplain pans differed from the endorheic systems in pH, conductivity, nutrients and suspended solids. Connectivity was found to be insignificant, as connections between these systems were probably too infrequent. Seasonal pans were uniquely distinguished by their morphometric, physico-chemical and hydrological characteristics. Inevitably, they are vulnerable to climate change with the extent of their resilience currently unknown.

Using Exceedance Probability to Determine Total Maximum Daily Loads for Reservoir Water Quality Management

Total maximum daily loads (TMDLs) are used to protect water bodies based on their assimilative ability and are transferred as a maximum allowable load, which is the sum of all pollution emissions in a watershed that cannot be exceeded. This allowable load is calculated from a target water quality concentration and a flow state. The target water quality concentration is typically consistent with water quality standards; however, it is difficult to determine which flow state to use, especially for lakes and reservoirs. In this study, an exceedance probability method is established for determining the TMDL for reservoirs. The SWMM (Storm Water Management Model) was used to understand the pollution loads from the watershed, and the Vollenweider model was used to simulate the total phosphorous (TP) concentrations in the reservoir. Using the validated Vollenweider model, the relationship between pollution loads and the target TP concentration is illustrated. This relationship is associated with real changes in the reservoir water volume and is presented as the exceedance probability. In the study area (i.e., the Shiman Reservoir in Taiwan), an exceedance probability of 50% is suggested, and the allowable TP load is 22,209 kg/year when considering a target TP concentration of 20 μg/L. When considering effective management, the pollution sources in three hot spots are priorities, and controlling their point and nonpoint pollution sources can decrease TP from 25 to 22 μg/L.

Pathways of deep cyclones associated with large volume changes (LVCs) and major Baltic inflows (MBIs)

Large volume changes (LVCs) and major Baltic inflows (MBIs) are essential processes for the water exchange and renewal of the stagnant water in the Baltic Sea deep basins. These strong inflows are known to be forced by persistent westerly wind conditions. In this study, MBIs are considered as subset of LVCs transporting with the large water volume a big amount of highly saline and oxygenated water into the Baltic Sea. Since the early 1980s the frequency of MBIs has dropped drastically from 5 to 7 events to only one inflow per decade, and long lasting periods without MBIs became the usual state. Only in January 1993, 2003 and December 2014 MBIs occurred that were able to interrupt the stagnation periods in the deep basins of the Baltic Sea. However, in spite of the decreasing frequency of MBIs, there is no obvious decrease of LVCs. The Landsort sea level is known to reflect the mean sea level of the Baltic Sea very well, and hence LVCs have been calculated for the period 1887–2015 filtering daily time series of Landsort sea surface elevation anomalies. The cases with local minimum and maximum difference resulting in at least 60km3 of water volume change excluding the volume change due to runoff have been chosen for a closer study (1948–2013) of characteristic pathways of deep cyclones. The average duration of LVCs is about 40days. During this time, 5–6 deep cyclones move along characteristic storm tracks. Furthermore, MBIs are characterized by even higher cyclonic activity compared to average LVCs. We obtained four main routes of deep cyclones which were associated with LVCs, but also with the climatology. One is approaching from the west at about 56–60°N, passing the northern North Sea, northern Denmark, Sweden and the Island of Gotland. A second broad corridor of frequent cyclone pathways enters the study area north of Scotland between 60 and 66°N turning north-eastwards along the northern coast of Scandinavia. This branch bifurcates into smaller routes. One at about 62°N passing Oslo, southern Sweden and entering the central Baltic Sea, and another less frequent one at about 65°N, crossing Scandinavia south-eastwards passing the Sea of Bothnia and entering Finland. The conditions for LVCs to happen are temporal clustering of deep cyclones in certain trajectory corridors. We also found an increasing linear trend of the number of deep cyclones for the period 1950–2010.

Relationship between oxidative stress and brain swelling in goldfish (Carassius auratus) exposed to high environmental ammonia.

Buildups of ammonia can cause potentially fatal brain swelling in mammals, but such swelling is reversible in the anoxia- and ammonia-tolerant goldfish (Carassius auratus). We investigated brain swelling and its possible relationship to oxidative stress in the brain and liver of goldfish acutely exposed to high external ammonia (HEA; 5 mmol/l NH4Cl) at two different acclimation temperatures (14°C, 4°C). Exposure to HEA at 14°C for 72h resulted in increased internal ammonia and glutamine concentrations in the brain, and it caused cellular oxidative damage in the brain and liver. However, oxidative damage was most pronounced in brain, in which there was a twofold increase in thiobarbituric acid-reactive substances, a threefold increase in protein carbonylation, and a 20% increase in water volume (indicative of brain swelling). Increased activities of catalase, glutathione peroxidase, and glutathione reductase in the brain suggested that goldfish upregulate their antioxidant capacity to partially offset oxidative stress during hyperammonemia at 14°C. Notably, acclimation to colder (4°C) water completely attenuated the oxidative stress response to HEA in both tissues, and there was no change in brain water volume despite similar increases in internal ammonia. We suggest that ammonia-induced oxidative stress may be responsible for the swelling of goldfish brain during HEA, but further studies are needed to establish a mechanistic link between reactive oxygen species production and brain swelling. Nevertheless, a high capacity to withstand oxidative stress in response to variations in internal ammonia likely explains why goldfish are more resilient to this stressor than most other vertebrates.

Seasonal Changes in the Inundation Area and Water Volume of the Tonle Sap River and Its Floodplain

Flood pulses occur annually along the Tonle Sap River (TSR) due to the large volume of water flowing from Tonle Sap Lake (TSL), its tributaries, and the Mekong River (MR). This study describes the seasonal changes in inundation area and water volume in the floodplain along the TSR over three years. The method employed time series remote sensing images of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data, the digital elevation model (DEM) of the Shuttle Radar Topography Mission (SRTM), bathymetric data, and observed water level data. Adding normalized difference vegetation index (NDVI) as a “third band” in the maximum likelihood classification (MLC) provided higher accuracy compared to thresholding NDVI and pure MLC (two bands) only. The results showed that the inundation area ranged from 123.8 to 3251.2 km2 (mean: 1028.5 km2) with overall accuracy of 96.9%. The estimated water volume ranged from 418.3 to 2223.9 million m3 (mean: 917.3 million m3) from the dry to wet season, respectively. Seasonally, the TSR floodplain accounted for up to 5.3% and 3.2% of the mean annual inflow and outflow of the TSR, respectively. In addition to the TSL water reservoir, the TSR and its floodplain exchanged and stabilized the flow of the MR and its downstream delta, respectively. Overall, the obtained results have enhanced our understanding of the TSR, supporting further studies on river connectivity and reversal flow in this study area.

Advanced testing and performance specifications for the cementitious materials under external sulfate attacks

A new monitoring approach was developed to enhance the analysis of performance tests and provide new sulfate resistance criteria. Even in the case of low degradation rates or non-swelling materials exposed to external sulfate attacks, the method allows detecting microscopic evolutions via a set of easily accessible monitored parameters. The monitoring has been performed on a set of sulfate-resisting and non sulfate-resisting cement-based mortars. The main phenomena induced by external sulfate attack are leaching, precipitation, aggregates loss and cracking. Based on the monitoring of mass, hydrostatic weighing, elongation and the amount of leached OH− the method provides the samples dimensional variations, the volume and mass changes of minerals and free water, corresponding to the main phenomena of the external sulfate attack. On the one hand, the phenomena decoupling allows a better understanding of the sulfate attack mechanism. The observed equivalence between the volumes of leached and precipitated products highlights the influence of portlandite, the major leached mineral, on the precipitation mechanism. The precipitation-deformation correlation and the samples absolute deformation monitoring showed a common expansion mechanism for the different cement compositions. The cement type was found to influence the magnitude of deformations. On the other hand, the determination of the volume variations corresponding to each phenomenon allows the proposition of new performance indicators from the monitoring approach outputs: the averaged density, the deformation path and the expansion potential. The three indicators were sensitive to the microstructural and macroscopic evolutions. The expansion potential, related to crystallization pressure, was found to depend on cement composition.

Freeze–thaw performance of base course treated with carboxylated styrene–butadiene emulsion–Portland cement

Freeze–thaw (FT) cycles and moisture susceptibility are important factors influencing the geotechnical characteristics of soil–aggregates. Given the lack of published information on the behaviour of base course materials stabilised with styrene butadiene emulsions (SBE) and cement–SBE-treated base (CSBETB) under environmental conditions, especially freezing and thawing, this study investigated the effects of these additives on the CSBETB performance. The primary goal was to evaluate the resistance of CSBETB to moisture damage by performing FT, Marshall conditioning and AASHTO T-283 tests and to evaluate the long-term stripping susceptibility of CSBETB while also predicting the liquid antistripping additives to assess the mixture’s durability and workability. Specimens were stabilised with Portland cement, SBE and a Portland cement–SBE mixture and cured for 7 days, and their short- and long-term performances were studied. Test evaluation results show that the additions of additives increase the resistance of the mixtures to moisture damage. Results of durability tests performed for determining the resistance of compacted specimens to repeated FT cycles indicate that the specimen with the 4% cement–8% SBE mixture significantly improves water absorption, volume changes and weight losses. This indicates the effectiveness of this additive as a road base stabiliser with excellent engineering properties.

Changes in lakes water volume and runoff over ungauged Sahelian watersheds

A large part of the Sahel consists of endorheic hydrological systems, where reservoirs and lakes capture surface runoff during the rainy season, making water available during the dry season. Monitoring and understanding the dynamics of these lakes and their relationships to the ecohydrological evolution of the region is important to assess past, present and future changes of water resources in the Sahel.Yet, most of Sahelian watersheds are still ungauged or poorly gauged, which hinders the assessment of the water flows feeding the lakes and the overall runoff over their watershed.In this paper, a methodology is developed to estimate water inflow to lakes for ungauged watersheds. It is tested for the Agoufou lake in the Gourma region in Mali, for which in situ water height measurements and surface areas estimations by remote sensing are simultaneously available. A Height-Volume-Area (HVA) model is developed to relate water volume to water height and lake surface area. This model is combined to daily evaporation and precipitation to estimate water inflow to the lake, which approximates runoff over the whole watershed. The ratio between annual water inflow and precipitation increases over the last sixty years as a result of a significant increase in runoff coefficient over the Agoufou watershed.The method is then extended to derive water inflow to three other Sahelian lakes in Mauritania and Niger. No in situ measurements are available and lake surface areas estimation by remote sensing is the only source of information. Dry season surface area changes and estimated evaporation are used to select a suited VA relationship for each case.It is found that the ratio between annual water inflow and precipitation has also increased in the last 60years over these watersheds, although trends at the Mauritanian site are not statistically significant.The remote sensing approach developed in this study can be easily applied to recent sensors such as Sentinel-2 or Landsat-8, to quantify the evolution of hydrological systems in ungauged Sahelian regions.

Hydrological Evaluation of Lake Chad Basin Using Space Borne and Hydrological Model Observations

Sustainable water resource management requires the assessment of hydrological changes in response to climate fluctuations and anthropogenic activities in any given area. A quantitative estimation of water balance entities is important to understand the variations within a basin. Water resources in remote areas with little infrastructure and technological knowhow suffer from poor documentation, rendering water management difficult and unreliable. This study analyzes the changes in the hydrological behavior of the Lake Chad basin with extreme climatic and environmental conditions that hinder the collection of field observations. Total water storage (TWS) from the Gravity Recovery and Climate Experiment (GRACE), lake level variations from satellite altimetry, and water fluxes and soil moisture from Global Land Data Assimilation System (GLDAS) were used to study the spatiotemporal variability of the hydrological parameters of the Lake Chad basin. The estimated TWS varies in a similar pattern as the lake water level. TWS in the basin area is governed by the lake’s surface water. The subsurface water volume changes were derived by combining the altimetric lake volume with the TWS over the drainage basin. The results were compared with groundwater outputs from WaterGAP Global Hydrology Model (WGHM), with both showing a somewhat similar pattern. These results could provide an insight to the availability of water resources in the Lake Chad basin for current and future management purposes.

Monitoring changes in the water volume of Hulun Lake by integrating satellite altimetry data and Landsat images between 1992 and 2010

Lake level and volume are sensitive to climate change, and their changes can affect the sustainable utilization of regional water resources. Satellite radar/laser altimetry has effectively been used for monitoring water-level changes in recent years. In this study, satellite altimetry data and optical images were used to assess the changes in water level, area, and volume of Hulun Lake in north-eastern China. We derived a time series of lake levels for nearly two decades (1992 to 2010) from the altimetry data of two satellite sensors (Topex/Poseidon and Envisat RA-2); additionally, lake surface extent was extracted from Landsat TM/ETM+ images during the same period. The results indicate that the water level, area, and volume of Hulun Lake decreased over the past two decades. The water level shows a significant decrease (−0.36 m/year) of a total of −5.21 m from 1992 to 2010, specifically including a slight decrease (−0.4 m) during 1992 to 1999 and a sudden drop (−4.81 m) during 2000 to 2010. There has also been a consistent and significant reduction in lake area (−355.35 km 2 ) and volume (−12.92 km 3 ) . An integrated examination on changes in temperature, evaporation, precipitation, and runoff during 1992 to 2010 shows that the main changes in the Hulun Lake area are correlated with increasing temperature (0.47°C/year) and evaporation (13.61 mm/year) , as well as decreasing precipitation (−6.58 mm/year) and runoff (−1.04×10 8 m 3 /year) . Thus, we infer that climate warming is likely the main cause of the changes in water level, area, and volume of Hulun Lake. In addition, anthropogenic factors accelerate the degradation of the Hulun Lake wetland to some extent.

Development of experimental resin modified glass ionomer cements (RMGICs) with reduced water uptake and dimensional change

ObjectiveTo investigate water uptake, desorption, diffusion coefficient, solubility and dimensional changes of four experimental RMGICs in deionized water (DW) and artificial saliva (AS), and compare with two commercial RMGICs and control home liquids based on the two commercial materials used. MethodsTwo commercial RMGICs, RelyX Luting (RX, 3M ESPE) and Fuji Plus (FP, GC), two control home liquids and four new liquid compositions (F1, F2, R1, R2) comprising different percentages of the monomer THFM (tetrahydrofurfuryl-methacrylate) with the original monomer HEMA (2-hydroxyethyl-methacrylate) were used in this study. Home and experimental liquids were mixed with the corresponding commercial powder. Disk-shaped specimens (16mm diameter 1mm thickness) were immersed in DW/AS at 37°C (n=6) and weighed at regular time intervals. Percentage weight change with time was recorded. At 24 weeks, disks were desorbed in an oven at 37°C to minimum weight. ResultsAll new compositions showed lower water uptake and dimensional (volume) changes than the commercial products in both DW and AS. On desorption, FP showed higher weight loss compared to materials in the same group in both solutions (p<0.0001), with the exception of F2 in DW (p=0.283). RX had higher weight loss compared to R1 and R2 in DW and AS (p<0.0001). Fickian diffusion was confirmed for all materials immersed in DW and AS. SignificanceThe experimental compositions in this study have shown promising results when tested in both DW and AS with lower water uptakes and volume changes than commercial materials. This may lead to wider applications than current commercial materials.

Anatomy of Subsidence in Tianjin from Time Series InSAR

Groundwater is a major source of fresh water in Tianjin Municipality, China. The average rate of groundwater extraction in this area for the last 20 years fluctuates between 0.6 and 0.8 billion cubic meters per year. As a result, significant subsidence has been observed in Tianjin. In this study, C-band Envisat (Environmental Satellite) ASAR (Advanced Synthetic Aperture Radar) images and L-band ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array type L-band Synthetic Aperture Radar) data were employed to recover the Earth’s surface evolution during the period between 2007 and 2009 using InSAR time series techniques. Similar subsidence patterns can be observed in the overlapping area of the ASAR and PALSAR mean velocity maps with a maximum radar line of sight rate of ~170 mm·year−1. The west subsidence is modeled for ground water volume change using Mogi source array. Geological control by major faults on the east subsidence is analyzed. Storage coefficient of the east subsidence is estimated by InSAR displacements and temporal pattern of water level changes. InSAR has proven a useful tool for subsidence monitoring and displacement interpretation associated with underground water usage.

Trophic status of the largest freshwater lakes in the world

AbstractThe problem of lake eutrophication has been a relevant challenge for more than a century. Eutrophication has presently affected not only small‐sized and middle‐sized lakes, but most of the largest lakes in the world as well. The most rapid eutrophication has occurred for shallow water bodies in both tropical and temperate latitudinal zones. These processes are intensified by consistently high temperatures in tropical lakes, which contribute to accelerated biological processes. The eutrophication processes in deep lakes that contain large water volumes have mostly local impacts and primarily affect the shallow water zones. The dynamics of trophic status changes for the largest lakes in the world are discussed in this study, considering changes in the total water volumes characterizing different trophic categories that occurred during the period from 1950 to 2010. As the largest lakes are the most important reserves of surface fresh water on our planet, it is very important to have an understanding of the quality changes taking place in regard to this important water resource.

Wetting and elasto-plasticity based sculpture of liquid marbles.

As an emerging material with exotic properties, liquid marble holds great potential for such areas as microfluidics, stimuli-responsive sensors, micro-chemical reactors, micro-bioreactors, energy harvesting devices, and mechanical structures. In this study, we mainly concentrate on the mechanical behaviors, such as elasto-plasticity of liquid marble with the decrease of liquid volume. The contact radius with the substrate and Young's contact angle of liquid marble are both measured with the change of water volume, and those of a water droplet are compared. The mechanism for the different responses for liquid marble and water droplet is clarified according to the mechanics analysis. Moreover, it is found that liquid marble can behave like an elasto-plastic material when the particle surface density is big enough. Based upon this fact, liquid marble can be sculpted to all kinds of special shapes as expected. These investigations may cast new light on how to engineer multifunctional materials and devices, which are beneficial to microprinting and micromachining.

A Study of Some Physical Problems of Water Condition and Mass Transfer in Cellulose Acetate and Dynamic Membranes

The paper presents experimental study of physical water condition and mass transfer in cellulose acetate and dynamic semipermeable membranes by infrared spectrometric and hydrodynamic methods. The authors found that OH-groups of cellulose acetate form a nonequilibrium grid of hydrogen bonds between molecules and their fragments in the amorphous phase of the semipermeable membrane in the air-dried sample. The water molecules adsorbed on active —OH and —C = O groups, particularly in the amorphous phase, create additional negative charge on the molecules of cellulose acetate resulting from the orientation of the water dipoles, which leads to electrostatic repulsion of broken, stranded molecule fragments and straightening of polymer molecule while breaking intermolecular hydrogen bonds. Thermogravimetric studies to find out the structural organization of hydrogen bonds and water condition in the samples of the semipermeable polymeric MGA-95 membrane showed that at temperatures in the air-dry and water-saturated samples the membrane degradation process starts and ends with mass loss and endothermic effect. The research proves the fact of dynamic membranes formation on the ultrafilters from water starch solutions. Due to the changes in condition and volume of water in the dynamic layer of the membrane, it is possible to change kinetic coefficients, i.e. to regulate the process of baromembrane separation of industrial water solutions. Electro-kinetic characteristics of reverse osmosis semipermeable membranes were studied. The experimental curves of the potential depending on sorption of sodium bicarbonate by MGA-95 and LSA-100 membranes were obtained. The discrepancy between the calculated and experimental data did not exceed 10 %. The method devised for determining the membrane potential in the process of sorption of sodium bicarbonate can be used as a testing methodology of polymeric semipermeable membranes.

Camera on Vessel: A Camera-Based System to Measure Change in Water Volume in a Drinking Glass.

A major problem related to chronic health is patients’ “compliance” with new lifestyle changes, medical prescriptions, recommendations, or restrictions. Heart-failure and hemodialysis patients are usually placed on fluid restrictions due to their hemodynamic status. A holistic approach to managing fluid imbalance will incorporate the monitoring of salt-water intake, body-fluid retention, and fluid excretion in order to provide effective intervention at an early stage. Such an approach creates a need to develop a smart device that can monitor the drinking activities of the patient. This paper employs an empirical approach to infer the real water level in a conically shapped glass and the volume difference due to changes in water level. The method uses a low-resolution miniaturized camera to obtain images using an Arduino microcontroller. The images are processed in MATLAB. Conventional segmentation techniques (such as a Sobel filter to obtain a binary image) are applied to extract the level gradient, and an ellipsoidal fitting helps to estimate the size of the cup. The fitting (using least-squares criterion) between derived measurements in pixel and the real measurements shows a low covariance between the estimated measurement and the mean. The correlation between the estimated results to ground truth produced a variation of 3% from the mean.

Evolution of permeability across the transition from brittle failure to cataclastic flow in porous siltstone

AbstractPorous sedimentary rocks fail in a variety of modes ranging from localized, brittle deformation to pervasive, cataclastic flow. To improve our understanding of this transition and its affect on fluid flow and permeability, we investigated the mechanical behavior of a siltstone unit within the Marcellus Formation, PA USA, characterized by an initial porosity ranging from 41 to 45%. We explored both hydrostatic loading paths (σ1 = σ2 = σ3) and triaxial loading paths (σ1 &gt; σ2 = σ3) while maintaining constant effective pressure (Pe = Pc – Pp). Samples were deformed with an axial displacement rate of 0.1 μm/s (strain rate of 2 × 10−6 s−1). Changes in pore water volume were monitored (drained conditions) to measure the evolution of porosity. Permeability was measured at several stages of each experiment. Under hydrostatic loading, we find the onset of macroscropic grain crushing (P*) at 39 MPa. Triaxial loading experiments show a transition from brittle behavior with shear localization and compaction to cataclastic‐flow as confining pressure increases. When samples fail by shear localization, permeability decreases abruptly without significant changes in porosity. Conversely, for cataclastic deformation, permeability reduction is associated with significant porosity reduction. Postexperiment observation of brittle samples show localized shear zones characterized by grain comminution. Our data show how zones of shear localization can act as barriers to fluid flow and thus modify the hydrological and mechanical properties of the surrounding rocks. Our results have important implications for deformation behavior and permeability evolution in sedimentary systems, and in particular where the stress field is influenced by injection or pumping.

Using in situ vertical displacements to characterize changes in moisture load

AbstractChanges in soil moisture content alter the load on underlying material, and we have developed a technique for characterizing this effect by using an extensometer to measure the displacement caused by the load change. The extensometer is pushed into soil at depths of 5 m or more, and displacement between two anchors separated by ∼1.5 m is measured with a resolution of better than 0.01 μm (10−8 m). The instrument is sensitive to load changes at the ground surface within a radial distance that is roughly twice its depth, potentially providing a method for averaging changes in water content over hundreds of m2 or more. During a field trial at a site in South Carolina, compressive displacements in unsaturated saprolite were strongly correlated to rainfall with a calibration factor of 0.16 μm displacement per mm of rainfall ±0.002 μm/mm (R2 = 0.95). Estimates of the net change in water volume per unit area made using the calibration factor from rainfall were similar to independent estimates of evapotranspiration. The technique was affected by barometric pressure variations, but the sensitivity was less than expected and does not hinder meaningful application. A companion instrument demonstrated the displacement signal was repeatable.

DMSO Induces Dehydration near Lipid Membrane Surfaces

Dimethyl sulfoxide (DMSO) has been broadly used in biology as a cosolvent, a cryoprotectant, and an enhancer of membrane permeability, leading to the general assumption that DMSO-induced structural changes in cell membranes and their hydration water play important functional roles. Although the effects of DMSO on the membrane structure and the headgroup dehydration have been extensively studied, the mechanism by which DMSO invokes its effect on lipid membranes and the direct role of water in this process are unresolved. By directly probing the translational water diffusivity near unconfined lipid vesicle surfaces, the lipid headgroup mobility, and the repeat distances in multilamellar vesicles, we found that DMSO exclusively weakens the surface water network near the lipid membrane at a bulk DMSO mole fraction (XDMSO) of <0.1, regardless of the lipid composition and the lipid phase. Specifically, DMSO was found to effectively destabilize the hydration water structure at the lipid membrane surface at XDMSO <0.1, lower the energetic barrier to dehydrate this surface water, whose displacement otherwise requires a higher activation energy, consequently yielding compressed interbilayer distances in multilamellar vesicles at equilibrium with unaltered bilayer thicknesses. At XDMSO >0.1, DMSO enters the lipid interface and restricts the lipid headgroup motion. We postulate that DMSO acts as an efficient cryoprotectant even at low concentrations by exclusively disrupting the water network near the lipid membrane surface, weakening the cohesion between water and adhesion of water to the lipid headgroups, and so mitigating the stress induced by the volume change of water during freeze-thaw.

Correlation between subsurface high-salinity water in the northern South China Sea and the North Equatorial Current–Kuroshio circulation system from HYCOM simulations

Abstract. The North Pacific Tropical Water (NPTW), characterized by subsurface high salinity, is observed in the South China Sea (SCS) and is often used as an indicator of the water intrusion from the northwestern Pacific into the SCS. Based on the assimilation product from a global high-resolution Hybrid Coordinate Ocean Model (HYCOM) from 2008 through 2013, this study investigates the seasonal variability of subsurface high-salinity water (SHSW) in the northern SCS and its relationship with the North Equatorial Current–Kuroshio circulation system. Results show that the obvious seasonal variability of the SHSW appears at about 100–200 m in depth. It extends as far west as southeast of Hainan, reaching its volume maximum (minimum) in January (May). The seasonal variance contribution (seasonal variance accounting for the entire variance) is 0.38 in the period we considered, albeit with significant annual variance in other years. Further analysis shows that the changes in high-salinity water volume are highly correlated with the shift in the North Equatorial Current bifurcation latitude (NECBL), which reaches its northernmost point in December and its southernmost point in May. Due to the large-scale wind changes in the Pacific, the Luzon Strait transport (LST) weakens (strengthens) when the NECBL shifts to the south (north) during summer (winter), which results in the reduced (enhanced) SHSW intrusion from the northwestern Pacific into the northern SCS. It is also found that, on a seasonal timescale, the Kuroshio transport (KT) does not vary in phase with NECBL, LST and SHSW, indicating that the KT changes are probably not the governing factor for the seasonal variability of SHSW in the northern SCS.