Brine Rejection Research Articles

A Model‐Based Investigation of the Recent Rebound of Shelf Water Salinity in the Ross Sea

AbstractIntense atmosphere‐ocean‐ice interactions in the Ross Sea play a vital role in global overturning circulation by supplying saline and dense shelf waters. Since the 1960s, freshening of the Ross Sea shelf water has led to a decline in Antarctic Bottom Water formation. However, during 2012–2018, salinity of the western Ross Sea has rebounded. This study adopts a global ocean‐sea ice model to investigate the causes of this salinity rebound. Model‐based surface salinity budget analysis indicates that the salinity rebound was driven by increased brine rejection from sea ice formation, triggered by nearly equal effects of local anomalous winds and surface heat flux. The local divergent wind anomalies promoted local sea ice formation by creating a thin ice area, while cooling heat flux anomaly decreased the surface temperature, increasing sea ice production as well. This highlights the importance of understanding local climate variability in projecting future dense shelf water change.

The coupling of winds, ocean turbulence, and High Salinity Shelf Water in the Terra Nova Bay Polynya

The Terra Nova Bay (TNB) Polynya in the Western Ross Sea of Antarctica is a major producer of High Salinity Shelf Water (HSSW), a precursor to Antarctica Bottom Water (AABW). Processes occurring in and around the polynya can therefore effect change in the lower limb of overturning circulation in this region. Here, we use data from a densely-instrumented upper-ocean mooring, deployed for 1 year in a region of active HSSW formation within TNB, to examine the coupling of surface brine rejection and vertical mixing to katabatic wind forcing. We find a high correlation between salinity and winds during the wintertime HSSW production season at the mooring site, with a lag-response of 20 h in near-surface (∼47 m) salinity to winds measured at the nearby Automatic Weather Station (AWS) Manuela. Salinity and temperature measurements show a fully destratified water column by June, with a lag-response of near-seabed (∼360 m) salinity to near-surface salinity of just 5 h. Measurements of turbulent kinetic energy (TKE) dissipation rate (ɛ) from moored pulse-coherent acoustic Doppler current profilers (ADCPs) show general agreement with classic boundary layer scaling (BLS), and calculations of a vertical mixing timescale using the Obukhov length scale average to ∼2.5 h during austral winter, consistent with the 5-h lag time observed in the salinity data. Comparisons to data from concurrent mooring deployments along the southern boundary of TNB, as well as to previously published assessments of model simulations and data from Climatic Long-term Interaction for the Mass-balance in Antarctica (CLIMA) moorings, allow us to explore spatial variability in the coupling of winds and salinity across TNB and to speculate on possible HSSW circulation pathways.

Quantifying Drivers of Seasonal and Interannual Variability of Dissolved Oxygen in the Canada Basin Mixed Layer

AbstractAnalysis of dissolved oxygen (O2) in the Arctic's surface ocean provides insights into gas transfer between the atmosphere‐ice‐ocean system, water mass dynamics, and biogeochemical processes. In the Arctic Ocean's Canada Basin mixed layer, higher O2 concentrations are generally observed under sea ice compared to open water regions. Annual cycles of O2 and O2 saturation, increasing from summer through spring and then sharply declining to late summer, are tightly linked to sea ice cover. The primary fluxes that influence seasonal variability of O2 are modeled and compared to Ice‐Tethered Profiler O2 observations to understand the relative role of each flux in the annual cycle. Findings suggest that sea ice melt/growth dominates seasonal variations in mixed layer O2, with minor contributions from vertical entrainment and atmospheric exchange. While the influence of biological activity on O2 variability cannot be directly assessed, indirect evidence suggests relatively minor contributions, although with significant uncertainty. Past studies show that O2 molecules are expelled from sea ice during brine rejection; sea ice cover can then inhibit air‐sea gas exchange resulting in winter mixed layers that are super‐saturated. Decreasing mixed layer O2 concentrations and saturation levels are observed during winter months between 2007 and 2019 in the Canada Basin. Only a minor portion of the decreasing trend in wintertime O2 can be attributed to decreased solubility. This suggests the O2 decline may be linked to more efficient air‐sea exchange associated with increased open water areas in the winter sea ice pack that are not necessarily detectable via satellite observations.

Innovative stimuli-responsive membrane MSF brine rejection dilution by tertiary treated sewage effluent

In this study, treated wastewater and Multi-Stage Flash (MSF) brine were integrated into the Forward Osmosis (FO) system using pressure stimuli-responsive Nanofiltration (PSRNF) membranes to dilute magnesium, calcium, and sulfate MSF plant brine reject. The deposition of magnesium sulfate and calcium sulfate in the heat exchanger is one of the main issues affecting the performance and efficiency of MSF thermal desalination plants. Reducing the concentration of the divalent ions can minimize scale formation and deposition to a level that allows the MSF plant to operate at high top brine temperature (TBT) and without scale problems. The PSRNF membranes were chosen in the FO process because of their high water permeability, rejection of divalent and monovalent ions, small structure parameter (S), and inexpensiveness compared to commercial FO membranes. Three PSRNF membranes were tested in the FO process with the feed solution facing the active membrane layer to avoid active layer delamination. Although the PSRNF membrane exhibited negligible water flux at 0 bar, it increased when a 2–4 bar was applied to the feed solution. The wastewater temperature was set at 25 °C while 40 °C was the brine operational temperature to mimic the field situation. A maximum average water flux of 39.5 L/m2h was recorded at 4 bar feed pressure when the PSRNF membrane was used for the brine dilution, achieving up to 42% divalent ions dilution at 0.02 kWh/m3 specific power consumption. The average water flux in the PRSNF membrane was 35% higher than that in the commercial TFC FO membrane. Notably, the PSRNF membrane is ten times cheaper than commercial FO membranes. Notably, the PSRNF membrane is ten times cheaper than commercial FO membranes, achieving substantial cost reductions and pioneering advancements in FO purification technology.

An investigation of a proposed freezing desalination system integrating sweating effect and a Centrifugal-Based brine rejection technique

Freeze desalination (FD) presents a promising yet underutilized technique for addressing global water scarcity, hindered by challenges such as the necessity for ice crushing and washing. This study introduces an innovative FD system incorporating sweating effects and centrifugal brine rejection, aiming to simplify the process by eliminating these additional steps. We evaluate the impact of key variables including sweating period, centrifugation duration, and rotational velocity on ice quality and process efficiency. Through systematic examination, our findings reveal that the sweating period significantly influences product salinity and salt rejection efficiency, achieving a salinity reduction from 40 ppt to 0.99 ppt with a 95.05 % salt rejection rate. Additionally, the centrifugation method showcased low power consumption, marking a significant advancement towards more sustainable desalination practices. This research not only demonstrates the feasibility of the proposed FD system but also sets the groundwork for future enhancements in the field of desalination technology.

The Mixed Layer Salinity Balance in the Western Arctic Ocean

AbstractIn this study, we explore the mixed layer salinity (MLS) balance in the western Arctic Ocean based on the Arctic Subpolar gyre sTate Estimate (ASTE) results. The key components of the MLS budgets and their variabilities in response to the Beaufort Gyre (BG) spin‐up are identified. Seasonally, the surface forcing (brine rejection plus freshwater input) is the most important dominant contributor to the MLS balance. On the other hand, the entrainment dominates the interannual variability of MLS tendency inside the BG, while the advection dominates that in the Beaufort Sea. The sensitivity test of increased river discharge revealed a greater role of the advection term, along with weakened contributions from the surface forcing and entrainment, in determining the interannual variability of MLS balance. In contrast, the seasonal variabilities remained largely unchanged. The Lagrangian particle tracking reveals that the majority of BG freshwater within the mixed layer exits through the Canadian Archipelago prior to the BG spin‐up (2002–2006) and during its relaxation (2012–2017). We found a reduction in mixed layer freshwater sources from the external BG that could feed the gyre during its spin‐up (2007–2011), with the major contributions coming from the Beaufort Sea and the BG region itself through Ekman convergence. The mixed layer freshwater pathways are similar in the two versions of ASTE, but with noticeable proportion changes with the increasing river discharge.

Electrified Solar Zero Liquid Discharge: Exploring the Potential of PV-ZLD in the US.

Current brine management strategies are based on the disposal of brine in nearby aquifers, representing a loss in potential water and mineral resources. Zero liquid discharge (ZLD) is a possible strategy to reduce brine rejection while increasing the resource recovery from desalination plants. However, ZLD substantially increases the energy consumption and carbon footprint of a desalination plant. The predominant strategy to reduce the energy consumption and carbon footprint of ZLD is through the use of a hybrid desalination technology that integrates renewable energy. Here, we built a computational thermodynamic model of the most mature electrified hybrid technology for ZLD powered by photovoltaic (PV). We examine the potential size and cost of ZLD plants in the US. This work explores the variables (geospatial and design) that most influence the levelized cost of water and the second law efficiency. There is a negative correlation between minimizing the LCOW and maximizing the second-law. And maximizing the second-law, the states that more brine produces, Texas is the location where the studied system achieves the lowest LCOW and high second-law efficiency, while California is the state where the studied system is less favorable. A multiobjective optimization study assesses the impact of considering a carbon tax in the cost of produced water and determines the best potential size for the studied plant.

Sustainable biomimetic solar distillation with edge crystallization for passive salt collection and zero brine discharge

The urgency of addressing water scarcity and exponential population rise has necessitated the use of sustainable desalination for clean water production, while conventional thermal desalination processes consume fossil fuel with brine rejection. As a promising solution to sustainable solar thermal distillation, we report a scalable mangrove-mimicked device for direct solar vapor generation and passive salt collection without brine discharge. Capillarity-driven salty water supply and continuous vapor generation are ensured by anti-corrosion porous wicking stem and multi-layer leaves, which are made of low-cost superhydrophilic nanostructured titanium meshes. Precipitated salt at the leaf edge forms porous patch during daytime evaporation and get peeled by gravity during night when saline water rewets the leaves, and these salt patches can enhance vaporization by 1.6 times as indicated by our findings. The proposed solar vapor generator achieves a stable photothermal efficiency around 94% under one sun when treating synthetic seawater with a salinity of 3.5 wt.%. Under outdoor conditions, it can produce 2.2 L m−2 of freshwater per day from real seawater, which is sufficient for individual drinking needs. This kind of biomimetic solar distillation devices have demonstrated great capability in clean water production and passive salt collection to tackle global water and environmental challenges.

Application of deep learning in estimating the convective mixing induced by brine rejection

The open-water deep convection induced by brine rejection constitutes a primary process for deep water formation in high latitudes, playing a critical role in the global thermohaline circulation. Proper parameterization of subgrid-scale convective salt plumes arising from brine rejection is crucial for improving climate model simulations of ocean convection. Traditional physically driven parameterization schemes require numerous physical parameters. In this study, we aim to explore an objective, few-data-driven approach by using deep learning for subgrid scale salt plume parameterization. The Backpropagation Neural Network (BPNN) is trained using the output results of the Large Eddy Simulation (LES) model, which is well-suited for simulating the highly turbulent salt plumes. Results show that using the BPNN driven solely by salinity and latitude effectively captures essential information about the mixing coefficient induced by salt plumes. The application of deep learning provides a new perspective for proposing the subgrid scale parameterization of salt plumes.

Numerical Investigation of Diapycnal Mixing of the Kitikmeot Sea in the Southern Canadian Arctic Archipelago

ABSTRACT Utilizing a 1 / 12 ∘ numerical model, we examine the diapycnal mixing patterns in the Kitikmeot Sea, a semi-enclosed water body within the southern Canadian Arctic Archipelago. The analysis reveals that mixing intensity near the sea surface varies seasonally, with effective diffusivity values ranging from 10 − 5 to 10 − 3 m 2 s − 1 , while away from the surface, the effective diffusivity remains relatively stable between 10 − 5 and 10 − 4 m 2 s − 1 . The seasonal fluctuations in surface mixing intensity are strongly influenced by ice coverage, which impacts both the stratification and the energy input to the surface driving the mixing process. Mixing energetics analysis indicates that the majority of energy contributing to the mixing processes are applied to the sea surface. During ice-free periods, wind-driven stirring dominates near-surface mixing with effective diffusivities of 10 − 5 to 10 − 4 m 2 s − 1 . Minimum near-surface effective diffusivity values occur in July and August, when the surface water is fresher and near-surface stratification is stronger due to spring freshet. Conversely, during ice-covered seasons, surface cooling and brine rejection primarily drive near-surface mixing, leading to effective diffusivities of 10 − 3 m 2 s − 1 or higher. In most cases, the observed mixing efficiency is within the range of what has been found in other regions of the Arctic Ocean.

Sensitivity of Antarctic Shelf Waters and Abyssal Overturning to Local Winds

Abstract Winds around the Antarctic continental margin are known to exert a strong control on the local ocean stratification and circulation. However, past work has largely focused on the ocean response to changing winds in limited regional sectors and the circumpolar dynamical response to polar wind change remains uncertain. In this work, we use a high-resolution global ocean–sea ice model to investigate how dense shelf water formation and the temperature of continental shelf waters respond to changes in the zonal and meridional components of the polar surface winds. Increasing the zonal easterly wind component drives an enhanced southward Ekman transport in the surface layer, raising sea level over the continental shelf and deepening coastal isopycnals. The downward isopycnal movement cools the continental shelf, as colder surface waters replace warmer waters below. However, in this model the zonal easterly winds do not impact the strength of the abyssal overturning circulation, in contrast to past idealized model studies. Instead, increasing the meridional wind speed strengthens the abyssal overturning circulation via a sea ice advection mechanism. Enhanced offshore meridional wind speed increases the northward export of sea ice, resulting in decreased sea ice thickness over the continental shelf. The reduction in sea ice coverage leads to increased air–sea heat loss, sea ice formation, brine rejection, dense shelf water formation, and abyssal overturning circulation. Increasing the meridional winds causes warming at depth over most of the continental shelf, due to a heat advection feedback associated with the enhanced overturning circulation.

On the ability of OMIP models to simulate the ocean mixed layer depth and its seasonal cycle in the Arctic Ocean

We evaluate the skills of ocean–sea ice general circulation models involved in the Ocean Modeling Intercomparison Project in simulating the ocean mixed layer depth and its seasonal cycle in the Arctic region. During summer months, all models consistently underestimate the mixed layer depth compared to observational data from the Monthly Isopycnal Mixed layer Ocean Climatology and the Ice Tethered Profilers. In fall and winter, the models exhibit great variability compared to observational data, and inter-model comparison reveals differences up to several tens of meters. We analyze the origin of the fall and winter model biases in ice-covered regions, where the seasonal cycle of the surface salinity and mixed layer depth is strongly influenced by brine rejection resulting from ocean–sea ice interactions.Focusing first on the central Arctic Ocean, defined here as the region north of 80° N, we show that all models simulate more or less the same vertical sea ice mass balance and thus similar salt fluxes into the ocean during sea ice freezing. Furthermore, the model ensemble features a strong relationship between the stratification profile in September and the mixed layer depth at the end of winter. The models whose stratification compares the best to observational data also display the most realistic values of the mixed layer depth at the end of winter. We argue that the discrepancies between models are therefore not so much linked to the surface salt balance but rather to the accuracy with which those models reproduce the vertical salinity profile. In short, a weakly stratified ocean tends to create a deep mixed layer, while strong stratification leads to a shallow mixed layer. To substantiate this conclusion, we apply a simple conceptual model, which simulates the month-to-month evolution of the mixed layer depth using as input the vertical salinity gradients and the surface salt fluxes from general circulation models. Quite surprisingly, this simplified dynamics captures very well the behavior of the general circulation models, emphasizing the role of the different vertical stratification in the control of the mixed layer depth. Furthermore, this interplay may also significantly account for the large mixed layer biases observed in other ice-covered regions of the pan-Arctic seas, even though sea–ice ocean interaction is not the only driver of mixed layer variability in fall and winter there.

Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities.

Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities.

A 600 kyr reconstruction of deep Arctic seawater δ18O from benthic foraminiferal δ18O and ostracode Mg ∕ Ca paleothermometry

Abstract. The oxygen isotopic composition of benthic foraminiferal tests (δ18Ob) is one of the pre-eminent tools for correlating marine sediments and interpreting past terrestrial ice volume and deep-ocean temperatures. Despite the prevalence of δ18Ob applications to marine sediment cores over the Quaternary, its use is limited in the Arctic Ocean because of low benthic foraminiferal abundances, challenges with constructing independent sediment core age models, and an apparent muted amplitude of Arctic δ18Ob variability compared to open-ocean records. Here we evaluate the controls on Arctic δ18Ob by using ostracode Mg/Ca paleothermometry to generate a composite record of the δ18O of seawater (δ18Osw) from 12 sediment cores in the intermediate to deep Arctic Ocean (700–2700 m) that covers the last 600 kyr based on biostratigraphy and orbitally tuned age models. Results show that Arctic δ18Ob was generally higher than open-ocean δ18Ob during interglacials but was generally equivalent to global reference records during glacial periods. The reduced glacial–interglacial Arctic δ18Ob range resulted in part from the opposing effect of temperature, with intermediate to deep Arctic warming during glacials counteracting the whole-ocean δ18Osw increase from expanded terrestrial ice sheets. After removing the temperature effect from δ18Ob, we find that the intermediate to deep Arctic experienced large (≥1 ‰) variations in local δ18Osw, with generally higher local δ18Osw during interglacials and lower δ18Osw during glacials. Both the magnitude and timing of low local δ18Osw intervals are inconsistent with the recent proposal of freshwater intervals in the Arctic Ocean during past glaciations. Instead, we suggest that lower local δ18Osw in the intermediate to deep Arctic Ocean during glaciations reflected weaker upper-ocean stratification and more efficient transport of low-δ18Osw Arctic surface waters to depth by mixing and/or brine rejection.

The Salinity Budget of the Ross Sea Continental Shelf, Antarctica

AbstractToward understanding the trend and variability in the bottom water salinity in the Ross Sea, this study focuses on the seasonality of the salinity budget over the Ross Sea continental shelf, using a new coupled regional ocean‐sea ice‐ice shelf model. Owing to the sea ice production, the upstream advection, and the glacial melting, the Ross Sea continental shelf is characterized by the relatively saltier water on the western shelf than on the eastern shelf, with the saltiest water in the Terra Nova Bay Polynya. During the early freezing season (March–April), there is remarkable sea ice production over the broad continental shelf, which makes a significant contribution to the production of High Salinity Shelf Water (HSSW). The brine rejection in the polynyas leads to the salinification and deepening of the mixed layer, yet the upstream advection acts to decrease the salinity below the mixed layer until the deep convection is fully developed throughout the water column. The seasonal cycle of the salinity budget in the Ross Sea continental shelf is largely determined by the formation/melting of sea ice, the intrusion of modified Circumpolar Deep Water, and the outflow of HSSW, while the contribution of the Ross Ice Shelf melting is relatively small.

Controls on Dense Shelf Water Formation in Four East Antarctic Polynyas

AbstractCoastal polynyas are key formation regions for dense shelf water (DSW) that ultimately contributes to the ventilation of the ocean abyss. However, not all polynyas form DSW. We examine how the physiographic setting, water‐mass distribution and transformation, water column stratification, and sea‐ice production regulate DSW formation in four East Antarctic coastal polynyas. We use a salt budget to estimate the relative contribution of sea‐ice production and lateral advection to the monthly change in salinity in each polynya. DSW forms in Mackenzie polynya due to a combination of physical features (shallow water depth and a broad continental shelf) and high sea‐ice production. Sea‐ice formation begins early (March) in Mackenzie polynya, counteracting fresh advection and establishing a salty mixed layer in autumn that preconditions the water column for deep convection in winter. Sea‐ice production is moderate in the other three polynyas, but saline DSW is not formed (a fresh variety is formed in the Barrier polynya). In the Shackleton polynya, brine rejection during winter is insufficient to overcome the very fresh autumn mixed layer. In Vincennes Bay, a strong inflow of modified Circumpolar Deep Water stratifies the water column, hindering deep convection and DSW formation. Our study highlights that DSW formation in a given polynya depends on a complex combination of factors, some of which may be strongly altered under a changing climate, with potentially important consequences for the ventilation of the deep ocean, the global meridional overturning circulation, and the transport of ocean heat to Antarctic ice shelves.

Dominant frazil ice production in the Cape Darnley polynya leading to Antarctic Bottom Water formation.

Antarctic Bottom Water (AABW) occupies the abyssal layer of the world ocean and contributes to the global overturning circulation. It originates from dense shelf water, which forms from brine rejection during sea ice production. An important region of AABW formation has been identified off the Cape Darnley polynya. However, it remains unclear why and how high ice production leads to AABW formation. Using moored acoustic measurements and a satellite microwave algorithm, we reveal that underwater frazil ice dominates in the polynya. This underwater ice formation prevents heat-insulating surface-cover ice forming, thereby enabling efficient ice production. The high ice production in the nearshore and longer residence times create high-salinity source water for the AABW. Underwater frazil ice occurs as long as strong winds continue and occasionally penetrates depths of at least 80 m. Deep-penetrating frazil ice is particularly prominent in this polynya, while it also occurs in other Antarctic coastal polynyas.

Convective mixing induced by brine rejection and its parameterization using large eddy simulation

Brine rejection is a primary component of deep convection formation, in which the turbulent mixing associated with the convective plume is the key parameter. Large Eddy Simulation (LES) is more suitable for the modeling of convective mixing. In this study, we use LES to investigate the brine rejection-induced convective mixing forced by the loss of salinity flux at the surface. The model domain is set in a stratified, high-latitude location due to brine rejection most often occurring at high latitudes. The control case for the numerical experiments is configured with a horizontal and vertical resolution of 5 m located at 70°N. Results show that the three-dimensional structure of the sinking plume displays an umbrella-like shape with an upward flow along the central axis and downward flows around the central axis, and is associated with a robust anticlockwise vortex below the source of the salinity flux. A series of numerical experiments are conducted to test the sensitivity of three plume characteristic parameters: eddy viscosity, maximum sinking plume depth, and vortex intensity to two environmental variables: negative salinity flux imposed at the surface (SaF) and background stratification (N). Based on the sensitivity experiments, scaling relationships of eddy viscosity and maximum sinking plume depth concerning SaF and N are identified. Additionally, distributions of velocity show that the rotation has a significant inhibition effect on the sinking plume, while the scaling relationship of the sinking plume shows that gravitational force has a much stronger enhancement effect.

Recent changes and distribution of the newly-formed Cape Darnley Bottom Water, East Antarctica

Hydrographic top-to-bottom CTDs and profiling float profiles were collected during 2003–2020 periods in the south-west Indian Ocean sector of the Antarctic margin. Those calibrated dissolved oxygen, temperature and salinity records were used to document the distribution, pathway and changes of the newly-formed Cape Darnley Bottom Water (CDBW). We found that the newly-formed CDBW, with high fractions (50–90%) in the bottom 300 m, primarily appeared on the continental slope (64.5°-70°E) and the abyssal ocean (57°-64.5°E) in the eastern Cooperation Sea. Those distributions of CDBW fractions suggested a pathway originating from the Cape Darnley Polynya (CDP) and descending down Wild and Daly Canyons, and finally accumulating in the northwest abyssal ocean. The newly-formed CDBW presented decadal changes in potential temperature, salinity, dissolved oxygen, and neutral density between 2003-2006 and 2013–2020. It showed significant cooling (∼0.098 °C/decade), freshening (∼0.013/decade), increasing dissolved oxygen (∼11.8 μmol/kg/decade) rates on the continental slope just off CDP, while warming (0.018–0.038 °C/decade), freshening (0.0044–0.0055/decade), decreasing density (0.009–0.014 kg/m3/decade) and increasing dissolved oxygen (4–12 μmol/kg/decade) in the Daly Canyon. The most likely explanation of those high change rates is the enhanced CDBW formation caused by increased cascading Dense Shelf Water (DSW) plumes in Daly Canyon, and subsequently enhanced entrainment of warmer mid-depth Modified Circumpolar Deep Water (MCDW). In the northwest abyssal plain, the potential temperature and dissolved oxygen show little change while the freshening and more buoyant signals remain considerable, which might be influenced by the changes of AABWs from different sources. Finally, we relate the recent changes of newly-formed CDBW to the Sea Ice Production (SIP) change in the CDP. The SIP in the CDP shows significant increasing trends (0.52 m/decade) during 2002–2020. It increased by 12.5% during this period, which indicates an increased formation of regional DSW driven by the sea-ice formation and associated brine rejection, thus increasing formation of CDBW. Those processes were likely responsible for the decadal changes of the recently-formed CDBW.

On the variability of the Bering Sea Cold Pool and implications for the biophysical environment.

The Bering Sea experiences a seasonal sea ice cover, which is important to the biophysical environment found there. A pool of cold bottom water (<2°C) is formed on the shelf each winter as a result of cooling and vertical mixing due to brine rejection during the predominately local sea ice growth. The extent and distribution of this Cold Pool (CP) is largely controlled by the winter extent of sea ice in the Bering Sea, which can vary considerably and recently has been much lower than average. The cold bottom water of the CP is important for food security because it delineates the boundary between arctic and subarctic demersal fish species. A northward retreat of the CP will likely be associated with migration of subarctic species toward the Chukchi Sea. We use the fully-coupled Regional Arctic System Model (RASM) to examine variability of the extent and distribution of the CP and its relation to change in the sea ice cover in the Bering Sea during the period 1980-2018. RASM results confirm the direct correlation between the extent of sea ice and the CP and show a smaller CP as a consequence of realistically simulated recent declines of the sea ice cover in the Bering Sea. In fact, the area of the CP was found to be only 31% of the long-term mean in July of 2018. In addition, we also find that a low ice year is followed by a later diatom bloom, while a heavy ice year is followed by an early diatom bloom. Finally, the RASM probabilistic intra-annual forecast capability is reviewed, based on 31-member ensembles for 2019-2021, for its potential use for prediction of the winter sea ice cover and the subsequent summer CP area in the Bering Sea.