Three-dimensional Hydrodynamic Model Research Articles

A Data Assimilation Approach to the Modeling of 3D Hydrodynamic Flow Velocity in River Reaches

The measurement of river discharge is essential for sustainable water resource management. The velocity–area approach is the most common method for calculating river discharge. Although several velocity measurement methods exist, they often have varying degrees of technical issues attributed to their operational complexity, time effectiveness, accuracy, and environmental impact. To address these issues, we propose a three-dimensional (3D) hydrodynamic model coupled with data assimilation (DA) for velocity measurement with improved accuracy and efficiency. We then apply this model to the Lanxi River reach in Zhejiang Province, China. The experimental results confirm that the obtained assimilated velocities using our proposed algorithm are much closer to the observed velocities than the simulated velocities. Our results show that when using the proposed method, the RMSE is decreased by 78%, and the SKILL and DASS values are 0.96 and 0.92, respectively. These confirm that the DA scheme of the flow velocity measurement is effective and capable of significantly improving the accuracy of the velocity with lower computational complexity.

Impact of climate change on coastal water quality and its interaction with pollution prevention efforts

The impact of climate change on nearshore coastal water quality and its interaction with pollution prevention efforts (e.g., the development of green and gray water infrastructure) still lack systematic investigation. This study performed a holistic analysis of the impact of climate change on the salinity and concentrations of total nitrogen (TN), total phosphorus (TP) and chlorophyll a (Chl.a) in Shenzhen Bay between Shenzhen and Hong Kong, the two most developed megacities in South China, based on three-dimensional hydrodynamic and water quality modeling. The major study findings were as follows. First, Chl.a was the most sensitive parameter, and its bay-wide average concentration in 2100 was predicted to be approximately 13% and 46% higher than those in 2015 under mild and rapid climate change scenarios, respectively. Second, sea level rise was found to be a major driver of all four water quality parameters, while temperature and radiation mainly influenced Chl.a and precipitation mainly influenced nutrients. Third, water quality responses to climate change were highly heterogeneous over the bay. Even under a mild climate change scenario, the highest location-specific changes (2100 vs. 2015) in salinity and TN, TP and Chl.a concentrations were projected to be approximately 21%, 19%, 25%, and 65%, respectively. Fourth, changes in seasonal variation due to climate change may lead to an enhanced ecological risk of algal blooms. Finally, the effect of reducing TN and TP concentrations by proposed water infrastructure development was found to be significantly weakened (nearly 40% and 20% for TN and TP, respectively, under a mild climate change scenario), while the negative effect (i.e., increase in the Chl.a concentration) was notably accelerated. Regional cooperation is critical for protecting the water quality of the bay, particularly under climate change. The insights obtained in this study are applicable to other coastal water zones around the world with similar socioeconomic backgrounds and climatic conditions.

A Bayesian data assimilation framework for lake 3D hydrodynamic models with a physics-preserving particle filtering method using SPUX-MITgcm v1

Abstract. We present a Bayesian inference for a three-dimensional hydrodynamic model of Lake Geneva with stochastic weather forcing and high-frequency observational datasets. This is achieved by coupling a Bayesian inference package, SPUX, with a hydrodynamics package, MITgcm, into a single framework, SPUX-MITgcm. To mitigate uncertainty in the atmospheric forcing, we use a smoothed particle Markov chain Monte Carlo method, where the intermediate model state posteriors are resampled in accordance with their respective observational likelihoods. To improve the uncertainty quantification in the particle filter, we develop a bi-directional long short-term memory (BiLSTM) neural network to estimate lake skin temperature from a history of hydrodynamic bulk temperature predictions and atmospheric data. This study analyzes the benefit and costs of such a state-of-the-art computationally expensive calibration and assimilation method for lakes.

Hydrodynamical transport structure and lagrangian connectivity of circulations in the Pearl River Estuary

Using a three-dimensional (3D) hydrodynamic model, this study explored the seasonal hydrodynamic transport structure in the Pearl River Estuary and illustrated the intrinsic connectivity under multiscale motions from a Lagrangian perspective. Generally, the surface Lagrangian residual current (UL) is uniformly southwestward/southeastward in summer/winter, with a stronger intensity in the lower estuary. The bottom UL features in the southeastward direction in the upper estuary and northwest direction in the lower estuary. The fluvial–tide interaction line advances southeastward and northwestward in summer and winter, respectively. The UL captured the major transport processes and was in good agreement with the mean surface sediment transport patterns. In the transition region between Lantau Island and Neilingding Island, where it is largely affected by the interaction between the periodic tidal current and river discharge, the spatially averaged UL showed intensified intratidal variations and had a larger difference with the locally temporally averaged Eulerian residual current. The remarkable Lagrangian coherent structures that illustrated the transport paths and transport convergence regions were identified, which are generally consistent with the bottom sediment depocenters. Based on the Lagrangian connectivity analysis, it was revealed that a barrier between the western and eastern estuaries existed, which was weakened by the strong river discharge during summer. Two convergence regions near the Macau and Hong Kong waters were identified, where the sediment and pollutants easily settled. The study demonstrated the importance of the Lagrangian view in understanding the hydrodynamic process and transport structure in the estuary–shelf regions.

Study of an abnormally strong saltwater intrusion in the Humen Channel of the Pearl River estuary

Saltwater intrusion in estuaries has become a serious environmental problem, such as in the Pearl River estuary (PRE). In this study, we used a fully validated three-dimensional hydrodynamic model EFDC to numerically investigate the saltwater intrusion in the PRE during the dry season of 2007-2008. Based on the measured salinity, an abnormally strong saltwater intrusion occurred in the Humen Channel in February 2008. The saltwater intrusion occurred twice a month to varying extents, with each saltwater intrusion happening 1-3 days before spring tide, and the stronger saltwater intrusion always occurred at the beginning of the month. Our model results show that caused by a long-term northerly wind during the dry season, the increased steady shear term in the salt transport flux were responsible for the abnormally strong saltwater intrusion in the Humen Channel. The abnormally strong saltwater intrusion has features of long duration, far-reaching upstream distance and great hazard to freshwater resources. The wind effects were revealed to mainly influence the bottom salinity in the middle reach of the PRE, especially near the Humen outlet.

A study on the riprap movement based on marine hydrodynamic model and field observation

ABSTRACT The study of mechanisms and the accurate simulation of riprap movement caused by complex hydrodynamics are significant for harbor, channel and coastal engineering. Field measurement of current and riprap drift distance was conducted for a dike project in the port of Lianyungang, Jiangsu Province, China. Meanwhile, a well-validated three-dimensional hydrodynamic model was developed to study and analyze the riprap movement process and the influence of project position combined with the theoretical movement equation of riprap. At the moment of maximum flood, the riprap drift distance is greater than at the moment of maximum ebb. The riprap drift distance increase as the tidal inlet width decreases, which follows a second-order exponential distribution. The riprap mass reduces the riprap drift distance, and the magnitude of the reduction diminishes gradually as the riprap mass increases. Therefore, heavy riprap can reduce the horizontal drift distance in a construction.

Study on dynamic response of underwater towed system in ship propeller wakes using a new hydrodynamic model

The dynamic analysis of underwater towed systems is challenging considering complex flow disturbances such as ship propeller wakes. This paper proposed a new fully-coupled three-dimensional hydrodynamic model for the dynamic analysis of an underwater towed system under complex flow disturbances. The hydrodynamic characteristics of the towed vehicle and the flow field behind the towing ship and propeller were simulated using computational fluid dynamics (CFD). The fluid forces on the towing cable were determined by combining the Morison formula and the CFD method. A dynamic analysis of an underwater towed system in a towing ship propeller wake under typical uncontrolled towing and depth regulation operations was conducted. The simulation results indicated that the proposed method was reasonable. Moreover, the time-averaged position and posture of the underwater towed system and its hydrodynamic characteristics vary with the rotation rate of the ship propeller in uncontrolled towing operation under a fixed towing speed. Furthermore, the fluid forces on the towing system and the cable tension in the depth regulation operation changed more drastically than in the uncontrolled towing operation. The proposed method can be easily extended to simulate other marine cable systems.

A three-part coupled statistical and physical model to monitor water quality parameters governing disinfection byproduct risk at an urban drinking water intake

Extended drought in the twenty-first century has led to loss of volume for lakes and reservoirs across the globe. In the Colorado River Basin, USA, Lakes Powell and Mead have experienced a 68 and 71% decline in volume, respectively, since 2000. Lake Mead is important to the Las Vegas Valley as it accounts for 90–100% of the source water used to serve the 2.2 million residents and 43 million annual tourists. Lake Powell is also vital to maintaining water quality in Lake Mead as it is located upstream and provides 97% of the water entering Mead. As Lakes Powell and Mead are projected to continue decreasing in volume over the next 5 years, it is important to understand the effects of loss of lake volume on water quality in this highly-managed system. Here, the effects of lake drawdown on water quality parameters that affect disinfection byproduct (DBP) formation in the source water for the Las Vegas Valley are projected over the next 5 years using Federal flow projections, regression modeling to project influent temperature from Lake Powell into Lake Mead, and a three-dimensional hydrodynamic and water quality model for Lake Mead. Results from these modeling efforts include projections for changes in values of water temperature, bromide, and total organic carbon (TOC) at the modeled cell that contains the Las Vegas Valley's urban drinking water intake. Raw water bromide was found to have little change across modeled scenarios; however, raw water temperature is projected to increase because of falling lake surface elevations. Raw water TOC is projected to increase three-fold in the simulated scenario that includes the most loss of volume but remains close to historic values in the remaining simulated scenarios. With these raw water quality projections, water managers can better plan for alterations to the water treatment processes, including mitigation of DBP formation.

Three-dimensional hydrodynamic modelling of the Moroccan Atlantic coast: A case study of Agadir bay

Coastal areas are a noteworthy source of commercial and economic fortunes for surrounding municipalities throughout the Moroccan Atlantic coast. Thus, a deep knowledge of local hydrodynamics and environmental processes associated is integral to effective coastal management. 3D hydrodynamic model that includes a Lagrangian particle simulation can participate to this understanding of dynamics. The model was calibrated and validated against meteorological conditions, sea surface level, harmonic tidal constituents, water temperature and salinity using a combination of available in-situ measurements, satellite, and ARGO floats data. Subsequently, it was used to determine the pathway of passive tracers and estimate the local residence time (RT). Despite some discrepancies, the findings revealed a good match between simulations and observations, which underlines the feasibility of the model in predicting the main dynamic features of the Agadir bay. Overall, the hydrodynamics of the area is tidal dominated by semidiurnal tides (M2) and governed by westerly and northwesterly winds. Passive tracer simulations showed strong seasonal and spatial variability, conditioning the obtained RTs, with mean values much shorter during summer (3 to 9 days) than winter (5 to 15 days). The tracers look to be trapped inside a coastal cyclonic eddy that increases the RTs in the southern bay, making it an area with highest likelihood of accumulation of pollutants while favoring the northward transport and decrease RTs in the northern bay.

Effects of Environmental Factors on Suspended Sediment Plumes in the Continental Shelf Out of Danshuei River Estuary

The effects of environmental factors on suspended sediment plumes in the continental shelf out of the Danshuei River estuary were numerically investigated using an unstructured-grid three-dimensional hydrodynamic model (SCHISM) together with a suspended sediment (SS) module. The coupled model (SCHISM-SS) was calibrated and validated against the in situ measurement data in 2016. Consistent with the observation results, the model simulations satisfactorily reproduced the water levels, velocities, salinities, and suspended sediment concentrations. The model was then applied to explore the role of various environmental factors in the dynamics of suspended sediment plumes from the estuary to the adjacent coastal seas. These factors include tidal forcing, salinity, river discharge, and wind stress. Analysis and comparisons of different scenario results indicated that the suspended sediment plume was greatly affected by tides, e.g., a longer plume distance resulted from a larger flux under tidal motions. A higher sediment concentration in the plume in the offshore area was also found during the neap tide, relative to that observed during the spring tide. In addition, salinity affects the movement of density currents and the spread of the sediment plume, i.e., the plume distance is longer due to the residual circulation when a salinity difference is present. Further, an extreme river flow could occur during typhoon periods and would discharge a greater water volume into the coastal region, causing the suspended sediment plume to expand from the near shore. Finally, the directions of prevailing winds can slightly influence the sediment plumes.

Comparative Study on Water Temperature Stratified Flow under Different Vertical Coordinate Systems in Delft3D

Reservoirs often suffer from water blooms, which are likely related to the hydrodynamic and water temperature characteristics of the tributary bays. To obtain the detailed changing process of hydrodynamics and water temperature stratification, it is necessary to choose a suitable vertical coordinate system in order to achieve the required precision. Based on a physical model experiment of cold water flowing into the Generalized Reservoir Hydraulics (GRH) flume, both the σ-coordinate system model and the z-coordinate system model are built for comparison. For the z-coordinate system model, the influences of different grid resolutions and different bottom slopes on the simulation accuracy are also analyzed. The results show that the σ-coordinate system model can simulate cold-water underflow in a reservoir better than the z-coordinate system model, and the numerical errors of the z-coordinate system model can be reduced but not eliminated by increasing the horizontal grid resolution. When the bottom slope of the reservoir is less than 18‰, the z-coordinate system model can also be used to simulate cold-water underflow in a reservoir. The conclusions about vertical coordinate systems can be applied to the development of a three-dimensional hydrodynamic and water temperature model of reservoirs.

Parallel implementation of the SHYFEM (System of HydrodYnamic Finite Element Modules) model

Abstract. This paper presents the message passing interface (MPI)-based parallelization of the three-dimensional hydrodynamic model SHYFEM (System of HydrodYnamic Finite Element Modules). The original sequential version of the code was parallelized in order to reduce the execution time of high-resolution configurations using state-of-the-art high-performance computing (HPC) systems. A distributed memory approach was used, based on the MPI. Optimized numerical libraries were used to partition the unstructured grid (with a focus on load balancing) and to solve the sparse linear system of equations in parallel in the case of semi-to-fully implicit time stepping. The parallel implementation of the model was validated by comparing the outputs with those obtained from the sequential version. The performance assessment demonstrates a good level of scalability with a realistic configuration used as benchmark.

How has the eutrophication evolved in the tributary bay of the Three Gorges Reservoir area

Abstract The Three Gorges Reservoir on the Yangtze River is the largest water control project in the world. While exerting great benefits (i.e., flood control, hydropower generation, inland river navigation and scenic tourism), the eutrophication of the tributary bay of the Three Gorges Reservoir has become one of the main environmental problems. This paper is to study the causes of water environment evolution in the tributary bay and investigate the driving force of eutrophication succession after the Three Gorges Reservoir enters the regular operation. By considering the Meixi River on the left bank of the mainstream of the Three Gorges Reservoir area (a typical tributary), this paper developed a three-dimensional hydrodynamic, water quality and water eutrophication mathematical model for the Meixi tributary bay, calibrated with measured data about hydrological regime (water level, flow), hydrodynamic factors (velocity) and water quality (water temperature, Chl-a, TP, TN, etc.). The annual variation of Chl-a concentration in the tributary bay was simulated, and the response relationship between the variation of Chl-a concentration and water conditions of the mainstream and tributary bay (e.g., reservoir water level, reservoir bay velocity, exogenous nutrient input, water temperature stratification and other factors) was analyzed. Results show that the water storage operation of the Three Gorges Reservoir contributes to the low flow velocity maintenance (≤0.05 m/s) in the tributary bay, the backward flow of the mainstream and the sufficient nutrients carried by the tributary water; the water temperature stratification is more likely to occur in the slow detention area in the middle-upper part of the bay in spring and summer, which provides a potential driving force for algae blooms. With the continuous decline of pollution load input in the reservoir basin, the algae blooms in tributary bay was the result of the combined action of low water level operation, low flow velocity (≤0.02 m/s), a large number of non-point source loads input with rainfall and runoff (the proportion of wet year is >70%), and obvious water temperature stratification in shallow water area, and the suitable meteorological conditions are the main inducing factors. Therefore, since the ecological regulation cannot be applied to the multitudinous tributary bays, the non-point source pollution control in the tributary bay is the key to controlling factor.

Realistic 3D hydrodynamics simulations find significant turbulent entrainment in massive stars

ABSTRACT Our understanding of stellar structure and evolution coming from one-dimensional (1D) stellar models is limited by uncertainties related to multidimensional processes taking place in stellar interiors. 1D models, however, can now be tested and improved with the help of detailed three-dimensional (3D) hydrodynamics models, which can reproduce complex multidimensional processes over short time-scales, thanks to the recent advances in computing resources. Among these processes, turbulent entrainment leading to mixing across convective boundaries is one of the least understood and most impactful. Here, we present the results from a set of hydrodynamics simulations of the neon-burning shell in a massive star, and interpret them in the framework of the turbulent entrainment law from geophysics. Our simulations differ from previous studies in their unprecedented degree of realism in reproducing the stellar environment. Importantly, the strong entrainment found in the simulations highlights the major flaws of the current implementation of convective boundary mixing in 1D stellar models. This study therefore calls for major revisions of how convective boundaries are modelled in 1D, and in particular the implementation of entrainment in these models. This will have important implications for supernova theory, nucleosynthesis, neutron stars, and black holes physics.

Modelling the Dispersion of Seafloor Massive Sulphide Mining Plumes in the Mid Atlantic Ridge Around the Azores

It is increasingly recognised that deep-sea mining of seafloor massive sulphides (SMS) could become an important source of mineral resources. These operations will remove the targeted substrate and produce potentially toxic plumes from in situ seabed excavation and from the return water pumped back down to the seafloor. However, the spatial extent of the impact of deep-sea mining is still uncertain because few field experiments and models of plume dispersion have been conducted. In this study, we used three-dimensional hydrodynamic models of the Azores region together with a theoretical commercial mining operation of polymetallic SMS to simulate the potential dispersal of plumes originating from different phases of mining operations, and to assess the magnitude of potential impacts. Although the model simulations presented here were subject to many caveats, they did reveal some important patterns. The model projected marked differences among sites making generalisations about plume-dispersal patterns in mid-ocean ridges difficult. Nevertheless, the models predicted large horizontal and vertical plume-dispersals above the thresholds adopted. Persistent plumes (temporal frequency >50%, i.e., 6 months out of 12 months) were projected to disperse an average linear distance of 10 to 20 km, cover an area of 17 to 150 km2, and extend more than 800 m in the water column. In fact, the model projected that plumes may disperse beyond the licensed mining areas, reach the flanks and summits of nearby topographic features, and extend into the bathypelagic, mesopelagic, and epipelagic environments. Modelled plume-dispersal overlaps with the predicted distribution of cold-water corals and with existing fishing activities. These potential impacts would be of particular concern in regions such as the Azores, where local populations are highly dependent on the sea for their livelihoods. The findings of this study are an important initial step towards understanding the nature and magnitude of deep-sea mining impacts in space and time.

Impacts of atmospheric stilling and climate warming on cyanobacterial blooms: An individual-based modelling approach

Harmful algal blooms of the freshwater cyanobacteria genus Microcystis are a global problem and are expected to intensify with climate change. In studies of climate change impacts on Microcystis blooms, atmospheric stilling has not been considered. Stilling is expected to occur in some regions of the world with climate warming, and it will affect lake stratification regimes. We tested if stilling could affect water column Microcystis distributions using a novel individual-based model (IBM). Using the IBM coupled to a three-dimensional hydrodynamic model, we assessed responses of colonial Microcystis biomass to wind speed decrease and air temperature increase projected under a future climate. The IBM altered Microcystis colony size using relationships with turbulence from the literature, and included light, temperature, and nutrient effects on Microcystis growth using input data from a shallow urban lake. The model results show that dynamic variations in colony size are critical for accurate prediction of cyanobacterial bloom development and decay. Colony size (mean and variability) increased more than six-fold for a 20% decrease in wind speed compared with a 2 °C increase in air temperature. Our results suggest that atmospheric stilling needs to be included in projections of changes in the frequency, distribution and magnitude of blooms of buoyant, colony-forming cyanobacteria under climate change.

Possible Implications of Relatively High Levels of Initial 60Fe in Iron Meteorites for the Noncarbonaceous–Carbonaceous Meteorite Dichotomy and Solar Nebula Formation

Cook et al. found that iron meteorites have an initial abundance ratio of the short-lived isotope 60Fe to the stable isotope 56Fe of 60Fe/56Fe ∼ (6.4 ± 2.0) × 10−7. This appears to require the injection of live 60Fe from a Type II supernova (SN II) into the presolar molecular cloud core, as the observed ratio is over a factor of 10 times higher than would be expected to be found in the ambient interstellar medium (ISM) as a result of galactic chemical evolution. The supernova triggering and injection scenario offers a ready explanation for an elevated initial 60Fe level, and in addition provides a physical mechanism for explaining the noncarbonaceous–carbonaceous (NC–CC) dichotomy of meteorites. The NC–CC scenario hypothesizes the solar nebula first accreted material that was enriched in supernova-derived nuclides, and then later accreted material depleted in supernova-derived nuclides. While the NC–CC dichotomy refers to stable nuclides, not short-lived isotopes like 60Fe, the SN II triggering hypothesis provides an explanation for the otherwise unexplained change in nuclides being accreted by the solar nebula. Three-dimensional hydrodynamical models of SN II shock-triggered collapse show that after triggering collapse of the presolar cloud core, the shock front sweeps away the local ISM while accelerating the resulting protostar/disk to a speed of several kilometers per second, sufficient for the protostar/disk system to encounter within ∼1 Myr the more distant regions of a giant molecular cloud complex that might be expected to have a depleted inventory of supernova-derived nuclides.

CFD simulation and model predictive control of the pipeline transportation system in a trailing suction hopper dredger

Abstract The phenomenon of blocking pipe would appear for a trailing suction hopper dredger (TSHD) rake arm pipe in the construction process. Thus, based on the theory of particle flow mechanics, a transient three-dimensional two-phase hydrodynamic and sediment mixture model was established in this paper. Besides, different particle sizes of sediment concentration and velocity in the piping in the rake arm of the law were analyzed to solve the problem of blocking pipe and the prevention of dredging to provide theoretical support. Then, a model predictive controller was designed to regulate the mudflow in the pipeline by controlling the mud pump speed and compared with the proportional-integral (PI) controller. According to the results, the particle size of sediment affects concentration distribution in the pipeline under the same construction conditions for the TSHD. Besides, the larger the particle size of the sediment, the more significant the difference in the sediment concentration distribution in the pipeline. Similarly, the flow velocity is another influencing factor behind the change in concentration distribution in the pipeline, the increase in the flow velocity will improve the uniformity of concentration distribution in the pipeline, and the critical velocity will maintain the concentration distribution within a reasonable range. In terms of transportation control, the designed predictive model controller is capable of reducing overshoot and shorten the time required for adjustment. To sum up, the research result not only provides a valuable reference for the theoretical analysis and a controller design of the pipeline transportation system in the TSHD but also verifies the feasibility of the computational fluid dynamics model used in the study of pipeline transportation mechanisms.

Hydrodynamic Drivers of Nutrient and Phytoplankton Dynamics in a Subtropical Reservoir

Chlorophyll-a (chla) is an important parameter to assess water quality in lakes and reservoirs, since it is a proxy for phytoplankton biomass and primary production. The increasing availability of data with high spatial and temporal resolution allows assessing short-term dynamics and small-scale variations of chla within larger water bodies. In freshwater reservoirs, the nutrient concentrations and the physical conditions that control phytoplankton growth vary along their longitudinal extend. Here, we analyze how the flow paths of the inflowing river water into density-stratified reservoirs affect the vertical and longitudinal distribution of nutrients and chla. We combine spatially resolved and high-frequency measurements of chla from satellite remote sensing and in-situ sensors, with numerical simulations using a three-dimensional hydrodynamic model to assess the influence of density currents on chla dynamics along a subtropical drinking water reservoir in the south of Brazil. Chla did not have pronounced seasonal dynamics (4.9 ± 1.2 µg L−1, at the continuous measurement station); instead, spatial variability along the reservoir was more pronounced (4.4 ± 2.1 µg L−1, all monitored points within the euphotic zone). Most of the nutrients from the inflowing river were consumed in the upstream region, and phytoplankton in the lacustrine zone depended on internal loading. Temporal variability was observed only in the upstream region, and phytoplankton produced in that area was transported downstream by density currents, resulting in large concentrations of chla below the euphotic zone. The results of a hydrodynamic model that simulates the present state are in good agreement with the observations. Two simulated scenarios, where the density current patterns were altered, resulted only in slight variations in density currents, indicating that the influence of the main inflow was of minor relevance in chla concentrations in downstream regions of the reservoir. Our results highlight the importance of two-dimensional hydrodynamic processes in regulating phytoplankton dynamics in reservoirs.

Potential Impact of Late 1980s Regime Shift on the Collapse of Walleye Pollock Catch in the Western East/Japan Sea

Walleye pollock (Gadus chalcogramma) caught in the Korean fishing area dramatically decreased in the late 1980s. To investigate the potential impact of the late 1980s climate regime shift on the collapse of the pollock catch, we developed a three-dimensional hydrodynamic model with data assimilation and a particle tracking model. Data-assimilated reanalysis showed that sea surface temperature increased by approximately 2°C in the spawning area of pollock in the late 1980s. The suitable spawning area in the East Korean Bay decreased due to warming in the late 1980s. Spawned eggs of walleye pollock were tracked using a particle tracking model for 30 days in January and February during 1983–1992. The number of individuals transported to the nursery within the Korean fishing area from the spawning area was reduced by 74% in the late 1980s. The intensified East Korean Warm Current (EKWC) could be responsible for the decreased number of individuals transported to the southern area in the late 1980s. Warming in the Korean fishing area could also cause a decrease in pollock. These oceanic changes might be linked to climate regime shifts in the late 1980s. The warming regime with positive Arctic Oscillation and weakened monsoon intensified the northward flow of the EKWC and accelerated the warming of the spawning and fishing areas in the late 1980s.