Ocean Salt Research Articles

Phase Transitions in a Vanthoffite-Type Compound, Na6Zn(SO4)4: Insights from In Situ PXRD and Raman Spectroscopy.

The study of phase transitions in minerals or synthetic compounds analogous to mineral structures is of fundamental interest in different scientific disciplines, with applications ranging from understanding the Earth's geological history to advancing materials science and technology. They provide valuable data and insight into developing new functional materials with desired properties. In this context, we have investigated the structural phase transitions of Na6Zn(SO4)4, a synthetic compound analogous to the Vanthoffite mineral Na6Mg(SO4)4, which occurs abundantly in nature as oceanic salt deposits. The room temperature crystal structure is refined from powder X-ray diffraction (PXRD) data, and it belongs to a monoclinic system, space group P21/c, with Z = 2. Differential scanning calorimetry analysis suggests the possibility of multiple structural phase transitions between 338 and 400 °C. These phase transitions are substantiated by in situ powder X-ray diffraction and Raman spectroscopy. PXRD data with temperature reveal structural phase transitions with a change in crystal symmetry accompanied by the appearance/disappearance of diffraction peaks. Further, the dynamics of the SO4 tetrahedra units are probed using variable temperature Raman spectroscopy to understand the mechanism of structural phase transitions. These phase transitions are driven by the anomalies of the molecular vibration of sulfate tetrahedra at higher temperatures as revealed from Raman data. Additionally, ionic conductivity measurements also depict these structural phase transitions with a change in slope with an increase in temperature.

Corrosion performance of naval brass in a simulated ocean water environment under different aqueous conditions

This study assesses the corrosion response of naval brass (NB) (Cu-39.0Zn-1.0Sn-3.5Pb wt.%) with ocean water salt mixture added in distilled water (DW), tap water (TW), and 50%Tap water + 50%Rain water (TW + RW) conditions. The NB in DW exhibited reduced weight loss and corrosion rate compared to TW and TW + RW conditions, which was maximum in TW condition. The electrochemical corrosion rates increased to 168 h and declined at 336 h, with higher corrosion rates witnessed in TW and lowest in DW conditions. The corrosion rate after 168 h in TW was 32 % higher than in DW condition. The corrosion products on NB include cuprite, atacamite, brochantite, and simonkolleite, more prevalent in TW conditions. The dezincification was minimal in DW but increased in TW and TW + RW conditions, peaking in TW condition. Pit number and size were smaller in DW but larger in TW and TW + RW conditions, with TW exhibiting the most extensive and deeper pits, indicating heightened corrosion from localized Zn dissolution. Zn removal from α and β′ phases was lower initially in DW while escalating in TW and TW + RW conditions over time. The NB in the TW condition showed prominent Zn removal than in DW condition, especially after 336 h.

An innovative electrolytic cation exchange reactor system for cleaner generation of hydrogen gas using ocean water

The study presents a novel integrated three-compartment electrochemical continuous electrodeionization reactor that was constructed in a laboratory environment. In order to extract large amounts of carbon dioxide from naturally occurring oceanwater in the form of bicarbonate and carbonate, it develops a innovative electrolytic cation exchange process. At the same time, it produces hydrogen gas for possible hydrocarbon synthesis. The study employs the Box-Behnken experimental design approach implemented through the Design Expert software to investigate and optimize the performance of electrochemical hydrogen extraction from Ocean water from an integrated reactor. The integrated electrochemical continuous-type electrodeionization reactor comprises two cation-permeable membranes that operate as boundaries between three compartments: a central compartment and electrode compartments that house the cathode and anode, each of which may reverse polarity. These membranes are made of gel polystyrene cross-linked with divinylbenzene, which has acidic properties that allow cation transport while inhibiting anions. The integrated reactor's electrode chambers are enclosed in plexiglass end plates and contain distinct Plexiglass electrode compartments. These compartments have mesh and solid steel anode and cathode electrodes, with an electrode active area of 176.71 cm2. The influence of various factors, such as voltage and electrolyte amount, on the production of hydrogen synthesis is examined. The study results demonstrate a maximum hydrogen production rate of 2.2 mg/min and a hydrogen production efficiency of 7.82%. The lab testing was carried out using experimental equipment to determine viability. The tests included 35-min runs that measured hydrogen generation under various parameters, such as applied voltage, electrolyte concentration, and pH levels. The ocean salt solutions of 0.5M, 1M, and 2M were initially prepared and evaluated for hydrogen generation. Each concentration is assessed at a voltage range of 4–15V, with matching solution pH values ranging from 2 to 7. Optimization studies were conducted to enhance the hydrogen production rate. The results indicate that hydrogen production rises proportionally with applied voltage and electrolyte concentration but falls with pH growth. Within the Design Expert software, the statistical methods for response surface analysis and optimization are utilized accordingly.

Ocean eddy detection based on YOLO deep learning algorithm by synthetic aperture radar data

Ocean eddies play a crucial role in the global energy cycle and significantly impact the transport of heat, salt, and nutrients in the global ocean. Spaceborne synthetic aperture radar (SAR), with its high spatial resolution (O(20 m)) and wide coverage, is an important tool for studying ocean eddies. In this paper, we propose a deep-learning network, named EOLO, to automatically detect ocean Eddies observed in C-band spaceborne SAR imagery, based on the You-Only-Look-Once (YOLO) deep learning algorithm. A Sentinel-1 (S1) SAR data-based ocean eddy dataset (named EddyDataset) is established to train the EOLO network. To effectively improve the performance of the EOLO network, we introduced a channel attention mechanism, adopted the up-sampling operator with the larger receptive field, and improved feature fusion method, anchor box size, and loss function. With the support of a high-performance detection network, the geographic information extraction module based on the affine geographic transformation model and a data preprocessing module were added, making EOLO an application-level framework. Our experiment results on EddyDataset demonstrate that EOLO achieves a high quality of eddy detection with 91.5% average precision. We further applied EOLO to entire scenes of S1 images to detect eddies in the Red Sea, the Baltic Sea, and the Western Mediterranean Sea, achieving 96.6%, 98.8% and 98.9% precision, respectively. Moreover, EOLO was used to extract size and location information of ocean eddies based on 6135 S1 scenes acquired in 2021 over the Western Mediterranean Sea. Their spatial characteristics were derived and compared with the eddies extracted from radar altimeter data, presenting interesting discrepancies between sub-mesoscale and mesoscale eddies in the ocean.

Planning for Drinking Water Salinization in the U.S. Atlantic and Gulf Coast Regions

Problem, research strategy, and findings Sea-level rise will bring ocean salts inland and salinize the drinking water sources of some coastal communities. How are municipalities, regions, and states preparing for salinization? In this study I evaluated 264 climate plans and seven state water plans from the Atlantic and Gulf coasts of the United States. Of these, 65 climate adaptation plans engaged with salinization in the context of drinking water; 21 made salinity adaptation recommendations, 6 discussed implemented monitoring or modeling, and 11 discussed implemented adaptation strategies. In state water plans, some states showed considerable salinization adaptation activity, but not all linked these actions to climate adaptation. Despite seawater intrusion and salinization being widely recognized, actions were concentrated in fewer states. Maryland, Delaware, Virginia, Florida, and Texas exhibited high degrees of engagement. Louisiana, Mississippi, Alabama, and Georgia showed little evidence of planning for salinization in climate or state water plans. In the absence of federal or state governments leading on managing sea-level rise–driven salinization, evaluating and preparing for the challenge of salinization is likely to become the de facto responsibility of coastal water suppliers and well owners, who may not have the capacity, budget, or jurisdiction to adequately monitor and protect supplies. Takeaway for practice Left to individual drinking water suppliers and well owners with varying capacity for adaptation, water supply salinization driven by sea-level rise has the potential to exacerbate existing inequities in drinking water provision. Planners can contribute to adapting coastal drinking water systems by integrating monitoring and modeling into climate adaptation plans, creating partnerships that enable drinking water adaptation actions, and supporting new approaches to water funding and financing.

Impact of marine atmospheric corrosion on the thermophysical properties of building coatings

Coastal structures are subjected to substantial thermal and solar loads, as well as relentless erosion from salt sprays originating from the ocean. This erosion poses a significant threat to the integrity of the surface coatings. However, the examination of the impact of salt spray on coatings from a heat-transfer perspective is limited. The objective of this study is to quantitatively evaluate the influence of ocean salt spray on the thermal properties of building coatings by investigating the modifications in surface thermal properties and heat transfer performance. Specifically, water-based polyurethane coatings, water-based acrylic coatings, and solvent-based coatings was subjected to corrosion through indoor accelerated aging tests and wind tunnel experiments. After a 30-day expose to ultraviolet ageing and salt spray corrosion, noticeable discoloration, and a substantial reduction in surface glossiness of up to 84 % are observed in the coating samples. The change in reflectance ratio before and after corrosion was measured using a spectrophotometer, indicating a maximum reduction of 9.4 %. To analyse the variations in the dynamic heat transfer performance of the samples before and after corrosion, this study employed the heat balance equation and conducted dynamic wind tunnel tests. The corrosion process appears to increase heat transfer along the coating's surface, evident from the consistent elevation in heat transfer capacity coefficients (CHTC) of the specimens after corrosion. Notably, these increases, particularly pronounced during nighttime, reveal substantial and consistent gaps in coefficients, reaching values of up to 10 W/m2 (WP1), 12.5 W/m2 (WA1), and 10 W/m2 (S2), respectively.

Three-dimensional characteristics of mesoscale eddies in the western boundary current region of the Bay of Bengal using ROMS-NPZD

Eddies play an important role in transporting and redistributing the heat, salt, and biological parameters in the global ocean. In this study, three-dimensional physio-biochemical characteristics of an anticyclonic (AE) and a cyclonic eddy (CE) associated with the poleward western boundary current (WBC) in the Bay of Bengal (BoB) are analyzed using a coupled bio-physical ocean model (ROMS-NPZD). Due to eddy-induced upwelling (downwelling) associated with the CE (AE), monopole patterns of temperature and salinity anomaly around the eddy center are occurred with extremum values at 100 – 150 m and 50 – 100 m depth, respectively. The upward (downward) curvature with a tip at eddy centers is observed in the isothermal layer depth, 20℃ isotherm (D20) nutricline, and oxycline. The depth of D20 deepens and shallows at the center from the edge by ∼60 m and ∼40 m for AE and CE, respectively. A relatively thick barrier layer around the center of AE is noted as compared to the CE. Within eddy interior, temperature and salinity tendencies of horizontal advection show a strong dipole pattern with extremum at eddy edges. The AE currents show positive tendencies in horizontal advection of temperature (salinity) at its northeastern (southwestern) side, which is totally opposite to that of CE. Intense horizontal advections in the adjacent flanks of eddies to the eastward jet of the WBC are due to their strong interactions. Vertical advection shows a quadrupole structure with alternating positive and negative cells within the eddies following the distorted vertical velocity field. Diffusion terms within eddies are quite small compared to the advection. Abundances of chlorophyll-a (∼1.2 mg/m3) at the base of the mixed layer around the CE center are absent for the AE.

Modeling seasonal salinity variations in a large West African lagoon (Nokoué, Benin): Major drivers and mechanisms

Nokoué lagoon is a shallow water body connected to the Gulf of Guinea through the long and narrow Cotonou channel. The salinity dynamics in the lagoon is investigated using the 3D SYMPHONIE numerical model. We first validate the model using salinity and water level data. Simulated and observed salinity and water level variations compare well demonstrating that the reference model simulation correctly reproduces the dynamics of the lagoon. By performing several simulations with varying external forcings and freshwater fluxes, the main drivers of salinity variability in the lagoon are identified. We first focus on the salinization phase of the lagoon at the end of the tropical wet season (between November and February), and we investigate the total change in salinity and the salt fluxes involved in these variations. The high frequency salt fluxes associated with the ocean tide import salt from the ocean via the Cotonou channel to the south of the lagoon. Baroclinic fluxes, associated with the influence of salt on density and associated pressure gradient, increase this local salinity input in the south, but also play a major role in the dispersion of salt throughout the lagoon. Two rivers provide a permanent freshwater inflow in the north/ northeast of the lagoon that limits the salinization of the whole lagoon. Finally, wind-generated high frequency recirculation, partially prevents the salinisation of the North-East of the lagoon. During the desalinization period (between May and September), the lagoon salinity variations are highly sensitive to the magnitude of river inflow. At a constant river flux rate, the lagoon attains an equilibrium state in salinity. As this equilibrium is reached, both the overall salinity level and the time needed to achieve it decrease notably with higher fluxes. Beyond 100 m3 s-1, only a small area near the Cotonou channel retains higher salinity, while surpassing 500 m3 s-1 results in complete desalination of the entire Nokoué lagoon.

Variable Salinity and Hydrogen Production in Europa's Ocean

AbstractEuropa's long‐term habitability depends on thermodynamics—modulated by tidal evolution—and geochemical pathways that define chemical and energy inventories for use by putative biology. Hydrogen produced from the reaction of water and rock during serpentinization is one potential source of metabolic energy. Here, we demonstrate how thermally modulated volumetric changes to Europa's ice shell, ocean, and fluid‐accessible rocky mantle influence oceanic salinity and serpentinization rates in Europa's interior. During periods of steady cooling, hydrogen flux into the ocean remains relatively constant because of the continuous propagation of thermal cracking into the rocky mantle regardless of ocean composition. However, during periods of fluctuating heat production driven by changes in orbital eccentricity, modulation of the ice shell volume, and consequently the salinity and water activity of the ocean, alters the serpentinization rate. In parallel, the extent of fracturing within the seafloor varies, changing the volume of reactable rock available. Our results show that the stability of serpentinization reactions on Europa over time highly depends on the thermal‐orbital evolution and oceanic salt content. The variability in the hydrogen production rate is significant across potential orbital histories, varying by up to 15 orders of magnitude for the lowest salinity and most kosmotropic ocean conditions, such as dilute MgSO4 compositions. We also show that this variability decreases with increasing ocean salinity and more chaotropic compositions, such as a concentrated NaCl ocean. These results suggest new ways that ocean composition and water activity are essential to stable habitable conditions in ocean worlds.

Enhanced Dissipation of Internal Tides in a Mesoscale Baroclinic Eddy

Abstract The dissipation of low-mode internal tides as they propagate through mesoscale baroclinic eddies is examined using a series of numerical simulations, complemented by three-dimensional ray tracing calculations. The incident mode-1 internal tide is refracted into convergent energy beams, resulting in a zone of reduced energy flux in the lee of the eddy. The dissipation of internal tides is significantly enhanced in the upper water column within strongly baroclinic (anticyclonic) eddies, exhibiting a spatially asymmetric pattern, due to trapped high-mode internal tides. Where the eddy velocity opposes the internal tide propagation velocity, high-mode waves can be trapped within the eddy, whereas high modes can freely propagate away from regions where eddy and internal wave velocities are in the same direction. The trapped high modes with large vertical shear are then dissipated, with the asymmetric distribution of trapping leading to the asymmetric distribution of dissipation. Three-dimensional ray tracing solutions further illustrate the importance of the baroclinic current for wave trapping. Similar enhancement of dissipation is also found for a baroclinic cyclonic eddy. However, a barotropic eddy is incapable of facilitating robust high modes and thus cannot generate significant dissipation of internal tides, despite its strong velocities. Both energy transfer from low to high modes in the baroclinic eddy structure and trapping of those high modes by the eddy velocity field are therefore necessary to produce internal wave dissipation, a conclusion confirmed by examining the sensitivity of the internal tide dissipation to eddy radius, vorticity, and vertical scale. Significance Statement The oceanic tides drive underwater waves at the tidal frequency known as internal tides. When these waves break, or dissipate, they can lead to mixing of oceanic heat and salt which impacts the ocean circulation and climate. Accurate climate predictions require computer models that correctly represent the distribution of this mixing. Here we explore how an oceanic eddy, a swirling vortex of order 100–400 km across, can locally enhance the dissipation of oceanic internal tides. We find that strong ocean eddies can be hotspots for internal tide dissipation, for both clockwise and anticlockwise rotating vortices, and surface-enhanced eddies are most effective at internal tide dissipation. These results can improve climate model representations of tidally driven mixing, leading to more credible future predictions.

Solid–liquid equilibria of Sorel phases and Mg(OH)2 in the system Na-Mg-Cl-OH-H2O. Part II: Pitzer modeling

For geochemical calculations of solubility equilibria between Sorel phases, Mg(OH)2, and oceanic salt solutions, the polythermal THEREDA dataset (based on the HMW model at 25°C) was extended. With both models, H+ solution concentrations in equilibrium with Mg(OH)2(s) and the 3-1-8 Sorel phase at 25°C can be calculated in good agreement. In contrast, calculated OH− solution concentrations do not agree. Using the solubility constants (lg Ks) determined up to 60°C in Part I of this work, together with available solubility isotherms up to 120°C, temperature functions for the 3-1-8 phase (25°C–100°C), 2-1-4 phase (60°C–120°C), and 9-1-4 phase (100°C–120°C) were derived. In order to accurately model the OH− solution concentrations, it was necessary to implement the solution species Mg3(OH)42+ (∆RGm° temperature function) in addition to the MgOH+ already contained in the previous model. Finally, fitting Pitzer mixing coefficients for both species now allow the calculation of the solubility equilibria of Mg(OH)2(s) and the Sorel phases in agreement with the experimental data in the Mg-Cl-OH-H2O and Na-Mg-Cl-OH-H2O systems.

Stable Brine Layers beneath Europa’s Chaos

The formation mechanism of Europa’s large chaos terrain (>∼100 km diameter) and associated lenticulae (<∼10 km diameter) has been debated since their observations by the Galileo spacecraft. Their geomorphology and distribution suggest there may be reservoirs of saline liquid water 1–3 km beneath the surface—the “shallow water” model—generated by injection of ocean water or melting of the ice shell. Recent investigations on the evolution of small shallow-water bodies (≤103 km3) suggests that salts with a small effect on melting point (MgSO4) can extend the lifetime of saline bodies by ∼5% compared to freshwater reservoirs. However, sodium chloride, identified as a potential oceanic salt, has a significantly stronger impact on the freezing point, suggesting a further extension of liquid lifetimes. Moreover, the substantial volumes of liquid water (∼104 km3) beneath large chaos could be melted in situ rather than injected through a fracture, implying a distinct chemistry and formation environment. Here, we use numerical models to explore how the chemistry and disparate origins of shallow water control its evolution and lifetime. For small, injected sills, we find that NaCl can extend their liquid lifetime to ∼140 kyr—up to a ∼60% increase over freshwater sills. Saline melt lenses will last at least 175 kyr but, in contrast to sills, may persist as a stable layer of brine beneath the surface for over 500 kyr. Our results provide further support for the presence of liquid water at shallow depths within Europa’s ice shell today.

Sand, Water, Salt: Managing the Elements in Literature of the American West, 1880–1925 by Jada Ach

Reviewed by: Sand, Water, Salt: Managing the Elements in Literature of the American West, 1880–1925 by Jada Ach Jenna Gersie Jada Ach, Sand, Water, Salt: Managing the Elements in Literature of the American West, 1880–1925. Lubbock: Texas Tech UP, 2021. 328 pp. Hardcover, $39.95; e-book, $19.95. In Jada Ach’s Sand, Water, Salt: Managing the Elements in Literature of the American West, 1880–1925, the ecomaterials of the West’s arid deserts and oceanscapes are radical, dynamic elements that become entangled with the human bodies that live there. Sand, water, and salt are neither waste materials nor commodities, but actants that resist control by the humans who try to manage both the elements themselves and their own bodies as they are exposed to the elements. “Try as we might, we can never manage our way out of ecological enmeshment” (9), Ach writes, and through her observations of intimate human–element engagements, Ach employs material ecocritical and queer ecology lenses to counter the top-down, hierarchical environmental management of the West’s wasteland spaces. Through her analysis of Progressive Era literature, Ach searches for hope in the porous spaces of environmental management, suggesting that we might learn from these texts how to “manage without mastery” as we approach human–environment relationships in the Anthropocene with compassion, care, and a focus on environmental justice (16). In McTeague: A Story of San Francisco by Frank Norris (1899) and The Land of Little Rain by Mary Austin (1903), Ach reads the desert sand as a queer actant with “revolutionary potential” as it works to undermine human attempts at management of desert spaces (76). As porous human bodies are inundated with sand in an intimate becoming, interactions with this lively element reveal human desires and longings as they resist the temporal progression and masculine ideals of administrative management. Similarly reading elements of desire and liveliness in the West’s water resources, Ach suggests that Progressive Era attitudes about water management can inform today’s water policy. In The River by Ednah Aiken (1914), The Virginian by Owen Wister (1902), and Life among the Piutes: Their Wrongs and Claims by Sarah Winnemucca Hopkins (1883), Ach shows how water is co-actant with the humans that attempt to [End Page 427] manage it, even as water, in its liveliness, remains beyond complete control. Finally, Ach heads further west, to the Pacific Ocean, where she reads The Sea-Wolf by Jack London (1904) and The American Diary of a Japanese Girl by Yonejirō Noguchi (1902) to explore how ocean salt permeates human bodies in culturally mediated ways, illustrating how both race and gender are managed in the production of imperial and transnational modern bodies. Throughout Sand, Water, Salt, Ach addresses contemporary environmental concerns, from uranium mining on Navajo land and managing radioactive waste to water crises at Standing Rock and in Flint. To address these environmental crises of the Anthropocene, Ach proposes “managing-by-drift,” allowing our engagements with the lively elements to inform and inspire decision-making about management. By drifting into moments of intimacy, activism, and pleasure, “situated managements” of “mutual care and shared governance” (29) can supplement already-established practices and policies as we “shift our attention from an ethics of fixing to one of living-with” (233 emphasis original). Together with the elements we can learn to resist hierarchies of management as we recognize our inseparability from the “strange agents and agencies” with which we are always intermingling in the West’s varied environments (233). Jenna Gersie University of Colorado Boulder Copyright © 2023 Western Literature Association ...

Impact of ocean data assimilation on climate predictions with ICON-ESM

We develop a data assimilation scheme with the Icosahedral Non-hydrostatic Earth System Model (ICON-ESM) for operational decadal and seasonal climate predictions at the German weather service. For this purpose, we implement an Ensemble Kalman Filter to the ocean component as a first step towards a weakly coupled data assimilation. We performed an assimilation experiment over the period 1960–2014. This ocean-only assimilation experiment serves to initialize 10-year long retrospective predictions (hindcasts) started each year on 1 November. On multi-annual time scales, we find predictability of sea surface temperature and salinity as well as oceanic heat and salt contents especially in the North Atlantic. The mean Atlantic Meridional Overturning Circulation is realistic and the variability is stable during the assimilation. On seasonal time scales, we find high predictive skill in the tropics with highest values in variables related to the El Niño/Southern Oscillation phenomenon. In the Arctic, the hindcasts correctly represent the decreasing sea ice trend in winter and, to a lesser degree, also in summer, although sea ice concentration is generally much too low in both hemispheres in summer. However, compared to other prediction systems, prediction skill is relatively low in regions apart from the tropical Pacific due to the missing atmospheric assimilation. Further improvements of the simulated mean state of ICON-ESM, e.g. through fine-tuning of the sea ice and the oceanic circulation in the Southern Ocean, are expected to improve the predictive skill. In general, we demonstrate that our data assimilation method is successfully initializing the oceanic component of the climate system.

Atlantic Water Properties, Transport and Heat Loss From Mooring Observations North of Svalbard

AbstractThe Atlantic Water inflow to the Arctic Ocean is transformed and modified in the area north of Svalbard, which influences the Arctic Ocean heat and salt budget. Year‐round observations are relatively sparse in this region partially covered by sea ice. We took advantage of one‐year‐long records of ocean currents and hydrography from seven moorings north of Svalbard. The moorings are organized in two arrays separated by 94 km along the path of the Atlantic Water inflow to investigate the properties, transport and heat loss of the Atlantic Water in 2018/2019. The Atlantic Water volume transport varies from 0.5 Sv (1 Sv = 106 m3s−1) in spring to 2 Sv in fall. The first mode of variation of the Atlantic Water inflow temperature is a warm/cold mode with a seasonal cycle. The second mode corresponds to a shorter time scale (6–7 days) variability in the onshore/offshore displacement of the temperature core linked to the mesoscale variability. Heat loss from the Atlantic Water in this region is estimated, for the first time using two mooring arrays and conserving the volume transport. The heat loss varies between 302 W m−2 in winter to 60 W m−2 in spring. The onshore moorings show a westward countercurrent driven by Ekman setup in spring, carrying transformed‐Atlantic Water. The offshore moorings show a bottom‐intensified current that covaries with the wind stress curl. These two mooring arrays allowed for a better comprehension of the structure and transformation of the slope currents north of Svalbard.

The Maxwell Effect and the Material Transport by Transient Eddies

AbstractMesoscale eddies—irregular time‐dependent currents with lateral scales of 10–200 km—are ubiquitous in the World Ocean. They profoundly affect general circulation and actively redistribute oceanic heat, salt, biogeochemical tracers, and pollutants. The development of accurate parameterizations of eddy‐induced transport remains one of the most pressing challenges in physical oceanography. Commonly used mesoscale parameterizations assume that the relation between eddy‐induced fluxes and the large‐scale property gradients is local and instantaneous. The present communication challenges this premise. We consider a closure that incorporates a delay in the adjustment of eddy fluxes to changing ambient distribution of properties. This model is inspired by the century‐and‐a‐half‐old idea of Maxwell, who argued that molecular dispersion necessarily involves a finite relaxation period. In our study, this principle is reinterpreted in the context of the turbulent transport problem. A series of simulations reveal marked improvements in eddy parameterizations brought by the inclusion of Maxwell's effect.

Effect of Climatic Precession on Dansgaard‐Oeschger‐Like Oscillations

AbstractUsing the climate model MIROC4m, we simulate self‐sustained oscillations of millennial‐scale periodicity in the climate and Atlantic meridional overturning circulation under glacial conditions. We show two cases of extreme climatic precession and examine the mechanism of these oscillations. When the climatic precession corresponds to strong (weak) boreal seasonality, the period of the oscillation is about 1,500 (3,000) years. During the stadial, hot (cool) summer conditions in the Northern Hemisphere contribute to thin (thick) sea ice, which covers the deep convection sites, triggering early (late) abrupt climate change. During the interstadial, as sea ice is thin (thick), cold deep‐water forms and cools the subsurface quickly (slowly), which influences the stratification of the North Atlantic Ocean. We show that the oscillations are explained by the internal feedbacks of the atmosphere‐sea ice‐ocean system, especially subsurface ocean temperature change and salt advection feedback with a positive feedback between the subpolar gyre and deep convection.

Improved High Resolution Ocean Reanalyses Using a Simple Smoother Algorithm

AbstractWe present a simple smoother designed for smooth data adjustments in sequentially generated reanalysis products by utilizing knowledge of future assimilation increments. A decay time parameter is applied to the smoother increments to account for memory decay timescales in the ocean. The result is different from simply time smoothing the reanalysis itself as only the increments are smoothed so the reanalysis product can retain high frequency variability that is being internally generated by the model and the atmospheric forcing. The smoother is applied first to the Lorenz 1963 model and then to the daily Met Office GloSea5 Global ¼° ocean reanalysis during 2016. Results show significant improvement over the original reanalysis in the 3D temperature and salinity state and variability, as well as in the sea surface height (SSH) and ocean currents. Comparisons are made directly against temperature, salinity and SSH observations, as well as independent 15 m drifter velocities. The impact on the time variability of conservative quantities, particularly ocean heat and salt content, as well as kinetic energy and the Atlantic Meridional Overturning Circulation (AMOC), is also demonstrated.

Geochemical benchmark tests to validate the conversion of thermodynamic data for TOUGHREACT

Abstract. According to the ongoing site selection process for a repository for high-level radioactive waste in Germany, rock salt, clay and crystalline rock are possible host rocks. The pore water of these rocks contains saline solutions with high ionic strengths. To model the speciation and/or migration of radionuclides in long-term safety analyses for nuclear waste disposal, a geochemical code that includes thermodynamic data suitable for saline solutions is needed. Thermodynamic equilibrium in saline solutions with high ionic strengths is usually modelled using the Pitzer approach (Pitzer, 1991). Within the context of nuclear waste disposal, the THEREDA project (Moog et al., 2015) provides thermodynamic data for some widely used geochemical codes (PHREEQC, Geochemist's Workbench, ChemApp, and EQ 3/6) using the Pitzer approach; however, for modelling in long-term safety analyses for nuclear waste disposal, another geochemical code, TOUGHREACT, is used. Therefore, scripts were developed to convert thermodynamic data of the THEREDA project to be applicable in TOUGHREACT. The scripts were validated by benchmark tests and by comparing calculations using PHREEQC and TOUGHREACT (Weyand et al., 2021). In total, 50 different benchmark tests were performed considering 3 specific geochemical systems, which are relevant to long-term safety analyses: (1) oceanic salt system, polythermal: K, Mg, Ca, Cl, SO4, H2O(l), (2) actinide system, isothermal: Am(III), Cm(III), Nd(III), Na, Mg, Ca, Cl, OH, H2O(l) and (3) carbonate system, isothermal: Na, K, Mg, Ca, Cl, SO4, HCO3/CO2(g), H2O(l). Each benchmark test considered specific ion concentrations in solution and in gaseous phases in the presence of specific minerals. The benchmark tests derived the geochemical equilibria and the results of both codes were compared to each other and to experimental data. The results of the calculations using both codes showed a good correlation. Remaining deviations can be explained by technical differences of the codes.

Extended thermodynamic model for high salinity produced waters

To support the development of desalination processes for high salinity produced waters, we developed a comprehensive thermodynamic model that reliably predicts the thermodynamic properties and phase behavior of produced water. This study extends a previously developed thermodynamic model for the aqueous hexary oceanic salt system by incorporating the Sr2+ and Ba2+ ions. Based on the electrolyte nonrandom two-liquid theory, the model requires two adjustable binary interaction parameters for each water-electrolyte and electrolyte-electrolyte pair that has a common ion. The binary interaction parameters for the electrolyte-electrolyte pairs involving Sr2+ and Ba2+ ions were identified using thermodynamic and salt solubility data. The model was validated for temperatures from 273.15 K to 473.15 K and electrolyte concentrations from infinite dilution to salt saturation. Extension of the model to include HCO3−, CO32−, and CO2 is currently in progress.