Comparing surface currents near the mouth of three bays along the U.S. East Coast: Chesapeake Bay, Delaware Bay, and New York Bay - Tal Ezer; Teresa Updyke (Ocean Dynamics, 2025)
Monthly surface currents at 2 km resolution near the mouths of three U.S. east coast bays were obtained from high-frequency radars (Coastal Ocean Dynamics Application Radar, CODAR) during 2012–2024. The currents near these bays, the Chesapeake Bay (CB), the Delaware Bay (DB) and the New York Bay (NB) were analyzed to infer similarity and differences, as well as potential common forcing from regional and basin-scale factors. The contribution to flow variability from local and remote forcing is evaluated by comparing surface currents with (a) river discharges into each bay, (b) with local and regional winds, and (c) with the North Atlantic Oscillation (NAO). The results show that surface flow variability near the mouth of the bays is linked with all three driving factors. The three bays often show similar flow patterns not only of the seasonal cycle, but also during extreme weather events. For example, increased surface flow into the bays from the Atlantic Ocean is seen when hurricanes are observed offshore in the fall, and increased surface flow from the bays is seen during winter storms. During positive NAO phases, eastward flow from all three bays increased due to intensified westerly winds, while during negative NAO phases flow decreased with weakening winds in the region. River discharges into the bays increased during 2012–2019 but decreased during 2019–2024. This change in river discharge trend was especially large in the CB, resulting in a change in trends of the surface currents. Monthly currents of each bay are only weakly correlated with the monthly river flow ( R ~ 0.2–0.3; P < 0.05), while the seasonal cycles of rivers and currents have higher correlations ( R ~ 0.6–0.7). Local winds show high correlations with the monthly currents ( R ~ 0.75) with the current direction ~ 45° to the right of the wind, as expected from Ekman theory. However, contributions to current variability from regional and remote factors cannot be ignored. The results demonstrate the complex nature of the currents near the mouth of bays since multiple drivers, including estuarine, coastal and open ocean dynamics contribute to the observed variability.

Timing errors in global sea level observations - Haidong Pan; Dingqi Wang; Bingtian Li; Tengfei Xu; Zexun Wei (Ocean Dynamics, 2025)

Turbidity effects on the Aegean sea surface properties using numerical simulations - Vassiliki Metheniti; Vassilios Vervatis; Nikolaos Kampanis; Sarantis Sofianos (Ocean Dynamics, 2025)

Variability of dissolved organic matter sources in the eastern Arabian Sea: impacts of physical and biological processes - N. V. H. K Chari; G. V. M. Gupta; C. K. Sherin; Ch. V. Ramu; B. Bikram Reddy; B. S. K. Kumar (Ocean Dynamics, 2025)

Pathways of tropical cyclone induced subsurface warming in the Northwestern Pacific Ocean - Qinya Zhang; Fanghua Xu (Ocean Dynamics, 2025)

Predictive modelling of run-out distance and sedimentation rate of channel-basin turbidity currents with a new numerical approach - Bruno Alvarez Scapin; Guilherme Vargas Fuhrmeister; Edith Beatriz Camaño Schettini (Ocean Dynamics, 2025)

Development of a daily coastal ocean model for Mississippi Sound and Bight - Mustafa Kemal Cambazoglu; Brandy N. Armstrong; Jerry D. Wiggert (Ocean Dynamics, 2024)
The Mississippi Sound and Bight is a complex coastal system with shallow estuarine waters that are highly vulnerable to the effects of climate change and anthropogenic influences. In order to further our understanding of the system and provide natural resource managers and decision-makers with science-based guidance, a pre-operational coastal ocean forecast system has been developed using the Coupled Ocean Atmosphere Wave Sediment Transport Modeling System (COAWST). The COAWST application for Mississippi Bight (msbCOAWST) can be run in hindcast mode, pre-operational near real-time mode, or forecast mode and relies on other operational models including the National Water Model (NWM) for river forcing, the High Resolution Rapid Refresh model (HRRR) for atmospheric forcing, and the Navy Coastal Ocean Model (NCOM) for open ocean boundary forcing. msbCOAWST is being validated using data from a variety of in situ measurements that quantify coastal processes, including tides and water quality parameters (i.e. temperature and salinity). The highest model skill is obtained for temperature followed by water levels and salinity. msbCOAWST has been used to provide guidance for quantifying how freshwater influences derived from river diversion operations impact water quality in estuarine waters. While the model is initially developed to study water quality and circulation in pre-operational near real-time and forecast modes, it is currently being extended to include waves, sediment transport, and biogeochemistry and also linked with habitat suitability models and ecological models in hindcast mode so as to comprehensively reveal consequential environmental concerns due to the onset and persistence of hypoxia, seasonal and storm-induced waves with their associated impacts on the region’s fisheries and shellfisheries.

Shear-driven vertical mixing and turbulent exchange over the continental slope in the northwestern Sea of Japan - Dmitry Stepanov; Alexander Ostrovskii; Evgeny Ryzhov; Alexander Lazaryuk (Ocean Dynamics, 2024)

Enhanced eddy activity along the Subantarctic Front under intensified westerly winds - Takuro Matsuta; Humio Mitsudera; Yukio Masumoto; Hideharu Sasaki; Ryo Furue; Tomomichi Ogata (Ocean Dynamics, 2024)

Hybrid covariance super-resolution data assimilation - Sébastien Barthélémy; François Counillon; Julien Brajard; Laurent Bertino (Ocean Dynamics, 2024)
The super-resolution data assimilation (SRDA) enhances a low-resolution (LR) model with a Neural Network (NN) that has learned the differences between high and low-resolution models offline and performs data assimilation in high-resolution (HR). The method enhances the accuracy of the EnKF-LR system for a minor computational overhead. However, performance quickly saturates when the ensemble size is increased due to the error introduced by the NN. We therefore combine the SRDA with the mixed-resolution data assimilation method (MRDA) into a method called “Hybrid covariance super-resolution data assimilation” (Hybrid SRDA). The forecast step runs an ensemble at two resolutions (high and low). The assimilation is done in the HR space by performing super-resolution on the LR members with the NN. The assimilation uses the hybrid covariance that combines the emulated and dynamical HR members. The scheme is extensively tested with a quasi-geostrophic model in twin experiments, with the LR grid being twice coarser than the HR. The Hybrid SRDA outperforms the SRDA, the MRDA, and the EnKF-HR at a given computational cost. The benefit is the largest compared to the EnKF-HR for small ensembles. However, even with larger computational resources, using a mix of high and low-resolution members is worth it. Besides, the Hybrid SRDA, the EnKF-HR, and the SRDA, unlike the MRDA, prevent the smoothing of dynamical structures of the background error covariance matrix. The Hybrid SRDA method is also attractive because it is customizable to available resources.

Evolution and structure of a mesoscale anticyclonic eddy in the northwestern Japan Sea and its exchange with surrounding waters: in situ observations and Lagrangian analysis - Maxim V. Budyansky; Svetlana Yu. Ladychenko; Vyacheslav B. Lobanov; Sergey V. Prants; Aleksandr A. Udalov (Ocean Dynamics, 2024)

Contributions of upper layer processes on the mixed layer temperature in the Bay of Bengal using relative importance methods - Piyali Goswami; Hitesh Gupta; Rahul Deogharia; Sourav Sil; Saikat Pramanik (Ocean Dynamics, 2024)

Effects of a surface layer cross-flow and slope steepness on the rate of descent of dense water flows along a slope - Jarle Berntsen; Bogi Hansen; Svein Østerhus; Karin Margretha Húsgarð Larsen; Hjálmar Hátún (Ocean Dynamics, 2024)
The pathways and mixing in dense water overflows have been addressed in a range of numerical studies based on the DOME (Dynamics of Overflow Mixing and Entrainment) setup. These studies are motivated by overflows such as the flow of dense and cold water over the ridge between Iceland and Scotland. The main route of this water is through the Faroe-Shetland channel and further through the Faroe Bank Channel. After leaving the Faroe Bank Channel, the dense water continues along the slope along the Iceland-Faroe Ridge. Across this ridge there is also a strong flow of Atlantic water that may affect the pathway and mixing in the dense plume. In the DOME investigations, the slope steepness is assumed to be constant and there is no active background flow in the ambient water masses above the dense plume. With the situation along the Iceland-Faroe Ridge in mind, the setup from the DOME experiment is adjusted to study the effects of i) the slope profile, ii) flows crossing the slope on top of the along-slope flow of dense water, and iii) the topography near the overflow channel of dense water. It is found that the rate of descent is depending on slope steepness, and for a curved slope going from flat on top of a ridge to much steeper away from the ridge, dense water parcels near the ridge top or crest will sink slower than the faster flowing dense water further down along the slope. A cross-flow over the ridge, mimicking the flow of Atlantic water over the Iceland-Faroe Ridge, will force stronger mixing between the dense water and the ambient water above and dense water mixed up into the surface water can be allowed to flow out across the ridge. Furthermore, the dynamical situation along the slope will change and fluid parcels in the deeper part of the plume can experience a faster rate of descent. By removing a barrier in the topography downstream of the overflow channel, dense water can be steered towards the ridge and the starting point of the center of mass of the descending overflow water will be higher up on the slope.

A new high-resolution Coastal Ice-Ocean Prediction System for the East Coast of Canada - Jean-Philippe Paquin; François Roy; Gregory C. Smith; Sarah MacDermid; Ji Lei; Frédéric Dupont; Youyu Lu; Stephanne Taylor; Simon St-Onge-Drouin; Hauke Blanken; Michael Dunphy; Nancy Soontiens (Ocean Dynamics, 2024)
The Coastal Ice Ocean Prediction System for the East Coast of Canada (CIOPS-E) was developed and implemented operationally at Environment and Climate Change Canada (ECCC) to support a variety of critical marine applications. These include support for ice services, search and rescue, environmental emergency response and maritime safety. CIOPS-E uses a 1/36° horizontal grid (~ 2 km) to simulate sea ice and ocean conditions over the northwest Atlantic Ocean and the Gulf of St. Lawrence (GSL). Forcing at lateral open boundaries is taken from ECCC’s data assimilative Regional Ice-Ocean Prediction System (RIOPS). A spectral nudging method is applied offshore to keep mesoscale features consistent with RIOPS. Over the continental shelf and GSL, the CIOPS-E solution is free to evolve according to the model dynamics. Overall, CIOPS-E significantly improves the representation of tidal and sub-tidal water levels compared to ECCC’s lower resolution systems: RIOPS (~ 6 km) and the Regional Marine Prediction System – GSL (RMPS-GSL, 5 km). Improvements in the GSL are due to the higher resolution and a better representation of bathymetry, boundary forcing and dynamics in the upper St. Lawrence Estuary. Sea surface temperatures show persistent summertime cold bias, larger in CIOPS-E than in RIOPS, as the latter is constrained by observations. The seasonal cycle of sea ice extent and volume, unconstrained in CIOPS-E, compares well with observational estimates, RIOPS and RMPS-GSL. A greater number of fine-scale features are found in CIOPS-E with narrow leads and more intense ice convergence zones, compared to both RIOPS and RMPS-GSL.

Monthly variability of wind-induced upwelling and its impact on chlorophyll-a distribution in the Southern and Northern parts of the Indonesian Archipelago - Gandhi Napitupulu (Ocean Dynamics, 2024)

Improvement of drag coefficient parameterization of WAVEWATCH-III using remotely sensed products during tropical cyclones - Yuyi Hu; Weizeng Shao; Ying Xu; Qingping Zou; Xingwei Jiang (Ocean Dynamics, 2024)

Surface ocean conditions of the Arabian Sea using two different wind forcings in the regional ocean modelling system setup - Prabha Kushwaha; Vivek Kumar Pandey; Bijan Kumar Das (Ocean Dynamics, 2024)

Assessment of tidal current potential in the Amapá’s inner continental shelf (Eastern Amazonia - Brazil) - Robert Willian Queiroz Farias; Maamar El -Robrini; Osvaldo Ronald Saavedra (Ocean Dynamics, 2024)

Aggregation and transport of microplastics by a cold-core ring in the southern recirculation of the Kuroshio Extension: the role of mesoscale eddies on plastic debris distribution - Ryota Nakajima; Akira Nagano; Satoshi Osafune; Masashi Tsuchiya; Katsunori Fujikura (Ocean Dynamics, 2024)
Mesoscale eddies – ocean vortices with spatial scales of tens to hundreds of kilometers and time scales of months to years – are among the most energetic forms of flow in the ocean, and may act as significant transporters of floating microplastics. Yet, shipboard observation has thus far not clarified the abundance and transport of microplastics in mesoscale eddies. We conducted floating microplastic surveys in an intense cyclonic mesoscale eddy with a large sea surface height depression (approximately 0.8 m), a so-called cold-core ring, in the Kuroshio Extension recirculation gyre (KERG) southeast of Japan. The concentration of microplastics within the eddy (460 × 10 4 pieces/km 2 ) was one or two orders of magnitude higher than in the adjacent oceanic waters, likely due to the acquisition of microplastics from the microplastic-rich Kuroshio Extension (KE) when detaching, as well as the horizontal entrainment of particles by the eddy. Our examination by using an assimilation product showed that most particles captured by the eddy remained within for several months while the eddy moved clockwise in the KERG. These results suggest that mesoscale eddies are of importance in the transportation and redistribution of microplastics on the ocean surface.

Sea state contributions to thermosteric sea-level in high-resolution ocean-wave coupled simulations - Antonio Bonaduce; Nam Thanh Pham; Joanna Staneva; Sebastian Grayek; Roshin P. Raj; Øyvind Breivik (Ocean Dynamics, 2024)
This study examines the impact of wave-induced processes (WIPs) in modulating thermosteric sea-level changes, highlighting the need to include these processes in future sea-level rise assessments and climate projections. The impact of wave-induced processes on thermosteric sea-level changes is investigated using coupled ocean-wave simulations. These simulations include the effects of Stokes-Coriolis forcing, sea-state dependent surface stress and energy fluxes, and wave-induced mixing. The experiments use a high-resolution configuration of the Geesthacht COAstal Model SysTem (GCOAST), covering the Northeast Atlantic, the North Sea and the Baltic Sea. The GCOAST system uses the Nucleus for European Modelling of the Ocean (NEMO) ocean model to account for wave-ocean interactions and ocean circulation. It is fully coupled with the WAM spectral wind wave model. The aim is to accurately quantify the sea state contribution to thermosteric sea level variability and trends over a 26-year period (1992–2017). The ability of wave-ocean coupled simulations to reveal the contribution of sea state to sea level variability and surge is demonstrated. It is clear that wave-induced processes (WIPs) play a significant role in sea surface dynamics, ocean mixing (mixed layer thickness) and modulation of air-sea fluxes (e.g. heat flux) in both winter (10–20%) and summer (10%), which in turn affect thermosteric sea level variability. The North Atlantic (in summer) and the Norwegian Trench (in winter) show significant contributions (40%) to the thermosteric sea-level variability due to wave-induced processes. The influence of WIPs on thermosteric sea level trends in the North Atlantic is up to the order of 1 mm yr-1 in both winter and summer, in the open ocean and at the shelf break. Smaller contributions are observed over the shelf areas of the North Sea. This study underscores the crucial role of WIPs in modulating sea-level changes and highlights the importance of including these processes in future sea-level rise assessments and climate projections.

Impact of undular surges on a vertical wall - Feidong Zheng; Yaan Hu; Xueyi Li; Guiyang Liu (Ocean Dynamics, 2024)

On the application of Miyata-Choi-Camassa model to surface waves - Tianyu Zhang; Zhan Wang; Binbin Zhao; Masoud Hayatdavoodi; R. Cengiz Ertekin; Wenyang Duan (Ocean Dynamics, 2024)

Dynamics of the Polar Front in the southwestern area of Svalbard, Norway - Igor Shulman; Ewa Jarosz; Stephanie Cayula; E. Joseph Metzger (Ocean Dynamics, 2024)
We have investigated the dynamics of the Polar Front (PF) in the southwestern area of Svalbard, where the dynamics are defined by the interaction between the Sørkapp Current (transporting cold and fresh Arctic-type water) and the West Spitsbergen Current (carrying the warmer and more saline Atlantic Water from the Norwegian Sea). Our approach was based on the global circulation model predictions. In accord with the model, the cold and fresher Arctic water masses originated from the eastern side of Svalbard and were flowing along the southern-most point of Svalbard into the southwestern area of Svalbard. This cold and fresher water was spreading and pushing warmer and more saline Atlantic water offshore. The model currents indicated that cold and fresher water masses were mostly transported northward along the south-western coast of Svalbard. In accord with the model and observed density profiles, the PF is a density compensated front with the density gradient mostly in the top 50-75 m. Presence of strong density gradients in the upper 50-75 m of the PF leads to the development of the submesoscale processes as surface frontogenesis and nonlinear Ekman transport. We found strong presence of surface frontogenesis at the PF in the model. The second submesoscale process, the nonlinear Ekman transport, is due to the forcing interaction. During the considered time frame, the winds were blowing mostly from the north-east to south-west across the PF, and therefore, the along-front wind component was very small, resulting in weak non-linear Ekman transport at the PF front.

Multi-sensor approach for chlorophyll-a monitoring in the coastal waters of Japan: a case study of the Yura Estuary - Shweta Yadav; Yoh Yamashita; Yosuke Alexandre Yamashiki (Ocean Dynamics, 2024)

Seasonal variation of chlorophyll-a in South Java over the past quarter-century - Yusuf Jati Wijaya; Ulung Jantama Wisha; Lilik Maslukah; Seto Windarto; Anindya Wirasatriya; Muhammad Zainuri (Ocean Dynamics, 2024)

Dynamics of submesoscale processes and their influence on vertical heat transport in the southeastern tropical Indian Ocean - Yifei Zhou; Wei Duan; Xuhua Cheng (Ocean Dynamics, 2024)

Interannual sea level variability in the North and Baltic seas and net flux through the Danish straits - Nam Thanh Pham; Joanna Staneva; Antonio Bonaduce; Emil V. Stanev; Sebastian Grayek (Ocean Dynamics, 2024)
The paper presents the reconstruction of sea levels in the North Sea and Baltic Sea using Kalman filter approach. Based on the statistical characteristics of one year of daily maps of sea level from the Geesthacht COAstal model SysTem (GCOAST) and daily data at tide gauges along the coastline of two basins, the method can reconstruct effectively and accurately the multidecadal sea level anomalies. The high accuracy reconstruction data were then used to investigate the interannual variability in both basins and to estimate the difference between outflows and inflows (net flux) through the Danish Straits. The highest mean, standard deviation, and extreme values of sea level anomalies appear in winter and are well reproduced in different regions, such as the German Bight, the Southern North Sea, the Bothnian Bay, the Gulfs of Finland and Riga. The sea level variability is highly correlated with the mean sea level pressure and the zonal wind, particularly in the German Bight and in the winter months. The contributions of river runoff and net precipitation on the net flux are significant in the spring. The local wind has a greater influence on the net flux than the remote drivers.

Correction to: Relative dispersion and relative diffusivities in an ocean-wave coupled model of the North Sea - Luciana Villa Castrillón; Marcel Ricker; Joanna Staneva; Jens Meyerjürgens; Thomas H. Badewien; Emil V. Stanev (Ocean Dynamics, 2024)

The sensitivity of tidal asymmetry descriptors in the Ems estuary - Anna Wünsche; Marius Becker; Ralf Fritzsch; Jessica Kelln; Christian Winter (Ocean Dynamics, 2024)
Tidal asymmetry in estuaries and other tidally dominated coastal systems is commonly evaluated to assess system states or their development. Based on different methods, local states are classified as either flood or ebb dominant. An increasing number of descriptors for deriving tidal asymmetry in recent years calls for a comparison and discussion of their sensitivity on input data and its quality. We compared tidal asymmetry from water level and current velocity using various descriptors that deduce from harmonic, ratio, and skewness methods. Computed from one-year measurements at different stations along the Ems estuary, their comparability was enabled by a new approach of scaling. Our results on the variation of sampling intervals demonstrated a highly site-specific sensitivity of the descriptors that led up to changes in the asymmetry direction in tidal duration asymmetry and phase lag. The slack water asymmetry appeared most sensitive to the studied parameter settings. As expected, variability of tidal asymmetry reduced with an increasing number of analyzed tides. At the same time, uncertainty from the asymmetry during spring or neap phases compared to spring-neap periods remained in all analyzed descriptors. Hence, the characterization of the estuary in terms of flood- or ebb-dominance depends critically on the quality and extent of the input data. For all parameter settings, the impact of river discharge on tidal asymmetry was pronounced but varied depending on the location in the estuary. The actual characterization of the effect of asymmetry, e.g., on sediment transport, is not conducted in this study. We propose that this requires a more comprehensive dataset, such as depth and cross-sectional variability of currents and sediment concentrations.

Response of wind stress and surface wave to the gusts under swell and wind-wave conditions - Jing Ren; Sheng Chen; Xunqiang Yin; Yuhuan Xue; Yongqing Yu; Zhanli Wang; Fangli Qiao (Ocean Dynamics, 2024)

Evaluation of the sub-annual sea level anomalies in the continental shelf of the Southwestern Atlantic and their relation to wind variability - Marie-Christin Juhl; Marcello Passaro; Denise Dettmering; Martin Saraceno (Ocean Dynamics, 2024)
We have analyzed the relationship between wind variability and sea level anomalies (SLA) on the Southwestern Atlantic Continental Shelf, focusing on sub-annual temporal scales. For this, we tested the capability of gridded altimetry to represent wind-driven SLA and compared results using an oceanographic model and tide gauge data. The present study used coherence analysis to analyze frequencies for which SLA and wind stress are coherent. The altimetry-SLA were found to have less energy below the three-month period compared to the model SLA. The coherence of along-shore wind stress and altimetry SLA was only significant for > 50 days (d), while the model SLA showed significant agreement in all periods considered, 20 d to annual. We further showed that geostrophic velocities on the continental shelf agreed significantly with SLA for > 50 d. As a result of an Empirical Orthogonal Function (EOF) analysis, we found that the second mode is highly coherent with the along-shore wind stress and accounts for 18.1% and 10.7% of variability in the model and altimetry sea level anomalies, respectively.

Assessment of static ensembles on a global ocean assimilation system using EAKF - Li Liu; Xueen Chen (Ocean Dynamics, 2024)

Relative dispersion and relative diffusivities in an ocean-wave coupled model of the North Sea - Luciana Villa Castrillón; Marcel Ricker; Joanna Staneva; Jens Meyerjürgens; Thomas H. Badewien; Emil V. Stanev (Ocean Dynamics, 2024)
The study analyzes the impact of various wave-induced processes on relative dispersion and diffusivities in the North Sea using OpenDrift, a Lagrangian particle-drift model driven by a fully coupled NEMO-WAM model. The coupled model parameterizations include sea state-dependent momentum flux, energy flux, and wave-induced mixing. The study demonstrates that Eulerian currents, influenced by the interaction between the ocean and wave models, significantly enhance particle transport. Experiments conducted using drifter clusters obtained during an RV Heincke excursion further confirm the impact of wind-wave coupling. The analysis includes a comparison of results from experiments with and without wave coupling. The impact of diffusion in the Lagrangian model on relative dispersion is investigated, with the conclusion that diffusion is essential for achieving precise simulations. Furthermore, the incorporation of wind-wave-driven mixing parameters, including sea state-dependent momentum flux, energy flux, and wave-induced mixing, into the hydrodynamic model leads to elevated levels of relative dispersion and diffusivity.

Experimental and numerical investigation of shelf flow crossing over a strait - Joseph Kuehl; Vitalii A. Sheremet (Ocean Dynamics, 2024)
Motivated by the phenomenon of Scotian Shelf Crossover events, the problem of a shelf flow that is interrupted by a strait is considered. Laboratory experiments in a rotating tank with barotropic and baroclinic flow over flat and sloping shelves confirm that the flow is steered by the bathymetric contours and mainly circumnavigates the gulf. In order to jump across the strait, as suggested by earlier theories, the flow must have unrealistically high Rossby numbers. However, the near bottom friction relaxes the bathymetric constraint and causes the formation of a peculiar jet crossing the strait diagonally. For the dissipation values such that a half of the transport goes around the gulf and half crosses the strait diagonally, the diagonal crossover jet becomes most evident. Numerical solutions for realistic values of the frictional parameter reproduce the results of the laboratory experiments and consideration of the actual Gulf of Maine bathymetry reproduces patterns similar to those observed by drift trajectories and in the satellite derived sea surface temperature fields.

Effects of open boundary bias correction and data assimilation in a regional ocean circulation model for the East Sea - Jae-Sung Choi; Kyungman Kwon; Byoung-Ju Choi (Ocean Dynamics, 2024)

An ensemble-based data assimilation system for forecasting variability of the Northwestern Pacific ocean - Yasumasa Miyazawa; Max Yaremchuk; Sergey M. Varlamov; Toru Miyama; Yu-Lin K. Chang; Hakase Hayashida (Ocean Dynamics, 2024)
An adjoint-free four-dimensional variational (a4dVar) data assimilation (DA) is implemented in an operational ocean forecast system based on an eddy-resolving ocean general circulation model for the Northwestern Pacific. Validation of the system against independent observations demonstrates that fitting the model to time-dependent satellite altimetry during a 10-day DA window leads to substantial skill improvements in the succeeding 60-day hindcast. The a4dVar corrects representation of the Kuroshio path variation south of Japan by adjusting the dynamical balance between amplitude/wavelength of the meander and flow advection. A larger ensemble spread tends to reduce the skill in representing the observed sea surface height anomaly, suggesting that it is possible to use the ensemble information for quantifying the forecast error. The ensemble information is also utilized for modification of the background error covariance (BEC), which improves the accuracy of temperature and salinity distributions. The modified BEC yields the skill decline of the Kuroshio path variation during the 60-day hindcast period, and the ensemble sensitivity analysis shows that changes in the dynamical balance caused by the ensemble BEC result in such skill deterioration.

Phytoplankton community responses to the combined effects of internal waves and anticyclonic eddies shed from the Kuroshio intrusion - Yanping Zhong; Xiaolin Bai; Edward A. Laws; Wenfang Lu; Zhida Huang; Wupeng Xiao; Jixin Chen; Lingqi Ma; Xin Liu; Bangqin Huang (Ocean Dynamics, 2024)

A snapshot of turbulence in the Northeastern Magellan Strait - Iossif Lozovatsky; Cristian Escauriaza; Leandro Suarez; Harindra J. S. Fernando; Megan Williams; Ronald Scott Coppersmith; Nicolas Mayorga (Ocean Dynamics, 2024)
First-ever measurements of the turbulent kinetic energy (TKE) dissipation rate in the northeastern Strait of Magellan (Segunda Angostura region) taken in March 2019 are reported here. At the time of microstructure measurements, the magnitude of the reversing tidal current ranged between 0.8 and 1.2 ms −1 . The probability distribution of the TKE dissipation rate in the water interior above the bottom boundary layer was lognormal with a high median value $${ε }_{med}^{MS}=1.2× {10}^{-6}$$ ε med MS = 1.2 × 10 - 6 Wkg −1 . Strong vertical shear, $$\left(1-2\right)× {10}^{-2}$$ 1 - 2 × 10 - 2 s −1 , in the weakly stratified water interior ensued a sub-critical gradient Richardson number $$Ri<{10}^{-1}-{10}^{-2}$$ R i < 10 - 1 - 10 - 2 . In the bottom boundary layer (BBL), the vertical shear and the TKE dissipation rate both decreased exponentially with the distance from the seafloor $$ξ$$ ξ , leading to a turbulent regime with an eddy viscosity $${K}_{M}\sim {10}^{-3}$$ K M ∼ 10 - 3 m 2 /s, which varied with time and location, while being independent of the vertical coordinate in the upper part of BBL (for $$ξ >\sim 2$$ ξ > ∼ 2 meters above the bottom).

Special modes with narrow amplification diagrams in harbor oscillations: definition and parametric study - Zhenjun Zheng; Guohai Dong; Xiaozhou Ma (Ocean Dynamics, 2024)

Processes responsible for mixed layer variations near mesoscale eddies in the Bay of Bengal - Venkata Sai Gulakaram; Naresh Krishna Vissa; Prasad Kumar Bhaskaran (Ocean Dynamics, 2024)

Influence of the representation of landfast ice on the simulation of the Arctic sea ice and Arctic Ocean halocline - Jean Sterlin; Tim Orval; Jean-François Lemieux; Clément Rousset; Thierry Fichefet; François Massonnet; Jonathan Raulier (Ocean Dynamics, 2024)

Towards efficient coastal flood modeling: A comparative assessment of bathtub, extended hydrodynamic, and total water level approaches - Yi Hong; James Kessler; Daniel Titze; Qing Yang; Xinyi Shen; Eric J. Anderson (Ocean Dynamics, 2024)

Cold fronts control multiscale spatiotemporal hydroperiod patterns in a man-made subtropical coastal delta (Wax Lake Region, Louisiana USA) - Wei Huang; Chunyan Li; Victor H. Rivera-Monroy (Ocean Dynamics, 2024)

Investigation of the Benguela upwelling eddies using Lagrangian modeling methods - Tatyana V. Belonenko; Maksim V. Budyansky; Avelina F. Akhtyamova; Alexander A. Udalov (Ocean Dynamics, 2024)

Eutrophication hotspots, nitrogen fluxes and climate impacts in estuarine ecosystems: A model study of the Odra estuary system - Johannes Pein; Joanna Staneva (Ocean Dynamics, 2024)
The Odra estuary in the southern Baltic Sea comprises the Odra (Szczecin) Lagoon, the Pomeranian Bay and a number of other shallow water areas and channels. Known for its abundance of fish, eutrophication in the Odra Lagoon is a pressing issue for science and environmental management representing a global problem: What determines the seasonal variability of nitrogen and nitrogen turnover in shallow water areas, and how does seasonal variability change due to climatic changes such as warming and sea level rise? How do such changes affect nutrient exports to the regional ocean? This study employs a high-resolution unstructured model system to investigate physical-biogeochemical interactions, nitrogen turnover, and conditions leading to nitrogen export to the Baltic Sea within the Odra estuary. The research comprises hindcast and a climatic experiment with modified water level and temperature inputs. The model reproduces the thermohaline dynamics of brackish shallow water areas, phytoplankton blooms and the variability of inorganic nitrogen. The simulations identify the dynamic partitioning of the Odra Lagoon into the highly eutrophic, lake-like Small Lagoon and more frequently flushed, zooplankton-rich Great Lagoon. Although the two years of the hindcast simulation feature very different boundary conditions in terms of river forcing, comparable patterns of seasonal nitrogen export emerge. In a climate change experiment with increased sea levels and global temperatures, the system appears sensitive, but remains stable with regard to nutrient transport and is therefore predictable. The climate change experiment reveals enhanced primary producer biomass concentrations, suggesting heightened eutrophication. While in the shallow waters of Odra Lagoon oxygen concentration remains relatively stable, oxygen depletion intensifies as the lagoon outflows enter the Pomeranian Bay. This phenomenon is linked to increased denitrification within the stratified Odra plume. Deeper, meandering channels, such as Swina, demonstrate resilience to oxygen reduction, influenced by sea level rise and enhanced currents. Based on the temporal-spatial high-resolution coupled, validated simulations, it is possible to develop tailor-made management solutions without having to run expensive and complicated observation campaigns in the shallow waters with complex topography.

Pathways of surface oceanic water intrusion into the Amazon Continental Shelf - Pedro Paulo de Freitas; Mauro Cirano; Carlos Eduardo Peres Teixeira; Martinho Marta-Almeida; Francisco Flávio de Brito Borges; Camilo Andrés Guerrero-Martin; Vando José Costa Gomes (Ocean Dynamics, 2024)

On the links between sea level and temperature variations in the Chesapeake Bay and the Atlantic Meridional Overturning Circulation (AMOC) - Tal Ezer; Teresa Updyke (Ocean Dynamics, 2024)
Recent studies found that on long time scales there are often unexplained opposite trends in sea level variability between the upper and lower Chesapeake Bay (CB). Therefore, daily sea level and temperature records were analyzed in two locations, Norfolk in the southern CB and Baltimore in the northern CB; surface currents from Coastal Ocean Dynamics Application Radar (CODAR) near the mouth of CB were also analyzed to examine connections between the CB and the Atlantic Ocean. The observations in the bay were compared with daily Atlantic Meridional Overturning Circulation (AMOC) observations during 2005–2021. Empirical Mode Decomposition (EMD) analysis was used to show that variations of sea level and temperature in the upper and lower CB are positively correlated with each other for short time scales of months to few years, but anticorrelated on low frequency modes representing decadal variability and long-term nonlinear trends. The long-term CB modes seem to be linked with AMOC variability through variations in the Gulf Stream and the wind-driven Ekman transports over the North Atlantic Ocean. AMOC variability correlates more strongly with variability in the southern CB near the mouth of the bay, where surface currents indicate potential links with AMOC variability. For example, when AMOC and the Gulf Stream were especially weak during 2009–2010, sea level in the southern bay was abnormally high, temperatures were colder than normal and outflow through the mouth of CB was especially high. Sea level in the upper bay responded to this change only 1–2 years later, which partly explains phase differences within the bay. A persistent trend of 0.22 cm/s per year of increased outflow from the CB, may be a sign of a climate-related trend associated with combination of weakening AMOC and increased precipitation and river discharge into the CB.

Water exchange in the Dardanelles: variations on synoptic to interannual time scales - Şehriban Saçu; Olgay Şen; Tarkan Erdik; İzzet Öztürk; Emil V. Stanev (Ocean Dynamics, 2024)
The bidirectional mass exchange between the Marmara Sea and the Aegean Sea provides one part of the critical hydrodynamic links between the Black Sea and the Mediterranean Sea. In this study, we examined exchange in the Dardanelles based on a 3-D numerical model simulation covering an 11-year period under realistic atmospheric forcing. The model includes the Black Sea, the Marmara Sea, and a part of the Aegean Sea to include the remote effects of basin dynamics. The main features as one-, two-, and three-layered flow structures are successfully reproduced by the model in comparison to earlier observations. It is found that the strait is subject to submaximal exchange by only one control near the Nara Pass. According to long-term modeling results, most variability occurs on synoptic time scales, and wind stress has a dominant role in those variations. The seasonal and interannual variability of exchange flow is relatively low and displays a close relationship with freshwater input to the Black Sea.

Seasonal variation of the sea surface salinity in the western tropical North Atlantic on two contrasting years of precipitation in the Amazon Basin - Atila Matias; Clemente Tanajura; Janini Pereira; Felipe Costa (Ocean Dynamics, 2024)

Editorial – Ocean Dynamics in 2023: overview and thank you to reviewers - Tal Ezer; Antonio Bonaduce; Sandro Carniel; Chabchoub Amin; Ricardo de Camargo; Sheila N. Estrada-Allis; Oliver B. Fringer; Avijit Gangopadhyay; Guoping Gao; Richard J. Greatbatch; Pierre F. J. Lermusiaux; Zhiyu Liu; et al. (Ocean Dynamics, 2024)

Revisiting the leeway of shipping containers: a case study of the M/V Zim Kingston incident - Graig Sutherland; Kuo-Hsien Chang; Paul Pestieau (Ocean Dynamics, 2024)
On 22 October 2021, 109 shipping containers fell overboard from the M/V Zim Kingston in rough seas off the coast of Vancouver Island, British Columbia, Canada. While afloat, these shipping containers pose a significant risk to marine traffic in addition to being a source of marine pollution. Out of the 109 shipping containers, 4 were discovered on the beaches of northwest Vancouver Island 5 days later. Drift simulations were made using the standard leeway tables for shipping containers that vary with the immersion fraction of the shipping container. These leeway values over the expected range of immersion levels underestimated the travelled distance of the shipping containers relative to the observed grounding locations. An increase in the leeway of 1.5% of the wind speed improves the agreement between the simulations and observations, which is consistent with the addition of the Stokes drift to the leeway of the shipping container. It is argued that the leeway measured using the direct method, which was used to calculate the leeway of shipping containers, does not implicitly include the Stokes drift as previously suggested. This result suggests that the Stokes drift should be added to the leeway calculated with the direct method. While the error is small over timescales of 24 to 48 h, it accumulates in time and is appreciable for drift prediction greater than 48 h.

Observed seasonality of M2 and M4 tidal currents in the Gulf of Khambhat using high-frequency radars - Samiran Mandal (Ocean Dynamics, 2024)

Submesoscale variability on the edge of Kuroshio-shed eddy in the northern South China Sea observed by underwater gliders - Haiyuan Yang; Zhiyuan Gao; Ke Ma; Zhaohui Chen; Yanhui Wang; Zhiyou Jing; Xin Ma; Wendong Niu (Ocean Dynamics, 2024)
Based on a submesoscale-resolving glider observation from April 25 to May 4, 2018, characteristics and underlying dynamics of submesoscale variability at the edge of an anticyclonic eddy shed from Kuroshio in the Northern South China Sea are explored in this study. Three underwater gliders traveled across the frontal zone and implemented ~ 300 dives, covering a horizontal distance of ~ 160 km and a vertical depth of ~ 500 m in 9 days. The character of k −2 slope for spectral potential energy and the strong lateral buoyancy gradient indicate frontogenesis-induced submesoscale motions on the eddy edge. Further analysis focusing on the potential vorticity and balanced Richardson number reveals the development of symmetric instability (SI), which is associated with the strong lateral gradient of buoyancy at the edge of the anticyclonic eddy in the late spring.

Mapping the spatiotemporal variability in global storm surge water levels using satellite radar altimetry - Inger Bij de Vaate; Dirk Cornelis Slobbe; Martin Verlaan (Ocean Dynamics, 2024)
Multi-mission satellite altimetry data have been used to study the spatial and temporal variability in global storm surge water levels. This was done by means of a time-dependent extreme value analysis applied to the monthly maximum detided water levels. To account for the limited temporal resolution of the satellite data, the data were first stacked on a $$\varvec{5}^{\varvec{° }} × \varvec{5}^{\varvec{° }}$$ 5 ∘ × 5 ∘ grid. Moreover, additional scaling was applied to the extreme value analysis for which the scaling factors were determined by means of a resampling method using reanalysis data. In addition to the conventional analysis using data from tide gauges, this study provides an insight in the ocean-wide storm surge properties. Nonetheless, where possible, results were compared to similar information derived from tide gauge data. Except for secular changes, the satellite-derived results are comparable to the information derived from tide gauges (correlation $$> \varvec{0.5}$$ > 0.5 ), although the tide gauges show more local variability. Where limited correlation was observed for the secular change, it was suggested that the satellites may not be able to fully capture the temporal variability in the short-lived, tropical storms, as opposed to extra-tropical storms.

Simulated response of seawater elevation and tidal dynamics in Jakarta Bay to coastal reclamation - N. S. Ningsih; F. Hanifah; L. F. Yani; R. Rachmayani (Ocean Dynamics, 2024)

Assessment of satellite altimetry SWH measurements by in situ observations within 25 km from the coast - Isabel Bué; Gil Lemos; Álvaro Semedo; João Catalão (Ocean Dynamics, 2024)

Deep learning-based forecasting of sea surface temperature in the interim future: application over the Aegean, Ionian, and Cretan Seas (NE Mediterranean Sea) - Marios Krestenitis; Yannis Androulidakis; Yannis Krestenitis (Ocean Dynamics, 2024)

Weakly nonlinear modulation of interfacial gravity-capillary waves - Tanmoy Pal; Asoke Kumar Dhar (Ocean Dynamics, 2024)

Significant wave height estimation from shipborne marine radar data using convolutional and self-attention network - Fupeng Wang; Xiaoliang Chu; Baoxue Zhang (Ocean Dynamics, 2024)

Research on the methods for separating wind sea and swell from directional wave spectra in finite-depth waters - Zhenjun Zheng; Guohai Dong; Huawei Dong; Xiaozhou Ma; Mingfu Tang (Ocean Dynamics, 2024)

The 12th International Workshop on Modeling the Ocean (IWMO 2022) in Ann Arbor, Michigan, USA on June 28–July 1, 2022 - Jia Wang; Tal Ezer; Ricardo de Camargo; Yasumasa Miyazawa; Joanna Staneva; Fanghua Xu (Ocean Dynamics, 2024)

Seasonal and intraseasonal modulation of near-inertial wind power associated with fluctuations in unidirectional wind speed in the Bay of Bengal - Valiyaparambil Shaji Aswathy; Madathil Sivasankaran Girishkumar; Kaladharan Athulya (Ocean Dynamics, 2024)

Responses of the Pacific and Atlantic decadal variabilities under global warming by using CMIP6 models - Yuyang Shang; Peng Liu; Sheng Wu (Ocean Dynamics, 2024)
Decadal variability in the ocean is an important indicator of climate system shifts and has considerable influences on marine ecosystems. We investigate the responses of decadal variability over the global ocean regions using nine CMIP6 models (BCC-CSM2-MR, CESM2-WACCM, CMCC-ESM2, EC-Earth3-Veg-LR, FGOAL-f3-L, INM-CM5-0, MIROC6, MPI-ESM1-2-LR, and NorESM2-MM). Our results show that climate models can capture the Pacific Decadal Oscillation, Tropical Pacific Decadal Variability, South Pacific Decadal Oscillation, and Atlantic Multidecadal Variability under present-day conditions. The ocean decadal variabilities are becoming weaker and their periods are decreasing, especially under the strong global warming scenario. However, there is a discrepancy between the Tropical Pacific Decadal Variability and the other three modes of climate variability. This might be caused by the nearly unchanged atmospheric forcing in the equatorial region, which is decreasing in the higher latitude regions.

Toxicity impacts on bioeconomic models of phytoplankton and zooplankton interactions - Nossaiba Baba; Imane Agmour; Youssef El Foutayeni; Naceur Achtaich (Ocean Dynamics, 2024)

Correction to: Sensitivity of the Lorenz energy cycle of the global ocean - John Ssebandeke; Jin-Song von Storch; Nils Brüggemann (Ocean Dynamics, 2024)

An Amundsen Sea source of decadal temperature changes on the Antarctic continental shelf - Sybren S. Drijfhout; Christopher Y. S. Bull; Helene Hewitt; Paul R. Holland; Adrian Jenkins; Pierre Mathiot; Alberto Naveira Garabato (Ocean Dynamics, 2024)
Mass loss from the Antarctic Ice Sheet is dominated by basal melting–induced warm ocean water. Ice-sheet mass loss and thinning of buttressing ice shelves occur primarily in the Amundsen and Bellingshausen Seas. Here, we show that in a global ocean simulation using the 0.25° Nucleus for European Modeling of Ocean (NEMO) model driven by the JRA55 reanalysis from 1982 to 2017, the Amundsen sector of the Antarctic continental shelf acts as a gateway, regulating the on-shelf access of warm Circumpolar Deep Water (CDW) from the deep ocean and its westward transfer to other sectors up to ca. 90° E, particularly the Ross Sea. As a result, anomalies in Antarctic-shelf-averaged temperature mainly originate in the Amundsen sector. These changes are primarily governed by shifts in the Amundsen Sea Low associated with tropical climate variability, modulating the on-shelf transport of CDW via wind-driven perturbations to ocean currents. The ensuing temperature anomalies progress westward from the Amundsen Sea via three distinct routes: a slow, convoluted westward pathway on the shelf via the Antarctic Coastal Current; a faster westward pathway along the shelf break via the Antarctic Slope Current and then onto the shelf along topographic troughs; and a third, eastward route toward the Bellingshausen sector, whereby temperature anomalies are transported into a region of local wind-generated changes farther north. These results emphasize the importance of the Amundsen sector for climate variability over the Antarctic shelves.

A three-layer model of hydrodynamic processes in the Cyprus Eddy system - Viktoriia M. Egorova; Mikhail A. Sokolovskiy; George Zodiatis (Ocean Dynamics, 2024)

Sensitivity of the Lorenz energy cycle of the global ocean - John Ssebandeke; Jin-Song von Storch; Nils Brüggemann (Ocean Dynamics, 2024)
We re-examine the Lorenz energy cycle (LEC) for the global ocean by assessing its sensitivity to model and forcing differences. We do so by comparing LECs derived from two simulations based on different eddy-rich ocean models, ICON-O and MPI-OM, both driven by NCEP/NCAR reanalysis, and by comparing LECs derived from two simulations generated using ICON-O model but driven by two different reanalyses, NCEP/NCAR and ERA5. Regarding model difference, we find weaker eddy kinetic energy, $$k_e$$ k e , in the ICON-O simulation than in the MPI-OM simulation. We attribute this to the higher horizontal resolution of MPI-OM in the Southern Ocean. The weaker $$k_e$$ k e in ICON-O is not caused by the lack of eddy available potential energy, $$p_e$$ p e , but by the strong dissipation of $$p_e$$ p e and the resulting weak conversion from $$p_e$$ p e to $$k_e$$ k e . Regarding forcing difference, we find that considerably more mechanical energy is generated by the ERA5 forcing, which has a higher spatial-temporal resolution compared to the NCEP/NCAR forcing. In particular, the generation of $$k_e$$ k e , which also contains the resolved part of the internal wave spectrum, is enhanced by about 1 TW (40%). However, the dominance of the baroclinic and the barotropic pathways forces the enhanced generation of $$k_e$$ k e to be balanced by an enhanced dissipation in the surface layer. The gross features of LEC are insensitive to both model and forcing differences, picturing the ocean as an inefficient “windmill” that converts only a small portion of the inputted mechanical energy into the interior mean and transient circulations.

Link between the internal variability and the baroclinic instability in the Bohai and Yellow Sea - Lin Lin; Hans von Storch; Xueen Chen; Wensheng Jiang; Shengquan Tang (Ocean Dynamics, 2023)
A regional ocean ensemble simulation with slightly different initial conditions demonstrates that internal variability is formed (not only) in the Bohai and Yellow Sea. In this paper, we analyze the relationship between the internal variability and the baroclinic instability, (represented by the Eady predicted theoretical diffusivity $${K}_{t}$$ K t ; the larger the $${K}_{t}$$ K t , the stronger the baroclinic instability level). In the ensemble, with tidal forcing, the spatial correlation between the Eady predicted theoretical diffusivity $${K}_{t}$$ K t and the internal variability amounts to 0.80. Also, the time evolution trends of baroclinic instability and internal variability are similar. Based on this evidence, baroclinic instability may be a significant driver for internal variability. This hypothesis is validated using an additional ensemble of simulations, which is identical to the first ensemble, but this time, the tides are inactivated. This modification leads to an increase in internal variability, combined with the strengthening of baroclinic instability. In addition, the baroclinic instability level and internal variability variation co-vary consistently when comparing summer and winter seasons, both with and without tides. Our interpretation is that a stronger baroclinic instability causes more potential energy to be transformed into kinetic energy, allowing the unforced disturbances to grow.

Statistical properties of extreme waves in multidirectional wave fields over complex bathymetry - Lili Mei; Hongzhou Chen; Xu Yang; Fukun Gui (Ocean Dynamics, 2023)

Direct observations of general geothermal convection in deep Mediterranean waters - Hans van Haren (Ocean Dynamics, 2023)

Interannual sea-level variation around mainland Japan forced by subtropical North Pacific wind and its possible impact on the Tsugaru warm current - Akira Nagano; Hitoshi Kaneko; Masahide Wakita (Ocean Dynamics, 2023)

On the relative role of east and west pacific sea surface temperature (SST) gradients in the prediction skill of Central Pacific NINO3.4 SST - S. Lekshmi; Rajib Chattopadhyay; D. S. Pai; M. Rajeevan; Vinu Valsala; K. S. Hosalikar; M. Mohapatra (Ocean Dynamics, 2023)

The dynamic mechanism of rapid sediment deposition in the mangrove region of the Guangxi Beibu Gulf - Jingsong Gao; Ling Chen; Hanfang Lu; Xiaoni Meng; Xuefeng Cao; Dapeng Wang; Lingling Xie; KitYue Kwan; Baoqing Hu (Ocean Dynamics, 2023)

Evaluation of seagrass as a nature-based solution for coastal protection in the German Wadden Sea - Benjamin Jacob; Tobias Dolch; Andreas Wurpts; Joanna Staneva (Ocean Dynamics, 2023)
Global climate change increases the overall risks for coastal flooding and erosion. Meanwhile, nature-based solutions (NbS) are increasingly becoming a focus of coastal protection measures to improve the climate adaptability. In this study, the present and potential future role of seagrass in coastal risk reduction strategies were explored for the highly energetic Wadden Sea area of the German Bight. The methodology in this study combined seagrass coverage data ( Zostera marina and Zostera noltei ) obtained by field surveys and what-if scenario simulations using the SCHISM unstructured grid model framework, coupling hydrodynamics, waves, sediments, and a seagrass module. The results suggest that the introduction of seagrass meadows locally can reduce both current velocities and significant wave heights in the order of up to 30 $$%$$ % in the deeper areas and above 90 $$%$$ % in the shallow areas. Reduction in bottom shear stress of a similar relative magnitude significantly reduced sediment mobilisation on the order of 2 g/L in the 95th quantile of bottom layer sediment concentrations. Effectively altering hydromorphodynamic conditions favouring sediment accumulation, seagrass expansion could help tidal flats height growths to keep up with SLR, thus further maintaining the bathymetry-induced tidal dampening and lowering flooding and erosion risks as well the amount of energy at dike infrastructure. The accumulated effect of seagrass under calm weather conditions is considered more important than the increased attenuation in absolute values it provides during extreme conditions. The overall conclusion is that seagrass expansion could be a useful addition to engineered coastal protection measures.

Changes in extreme wave events in the southwestern South Atlantic Ocean - Carolina B. Gramcianinov; Joanna Staneva; Ricardo de Camargo; Pedro L. da Silva Dias (Ocean Dynamics, 2023)
The southwestern South Atlantic (SWSA) has faced several extreme events that caused coastal and ocean hazards associated with high waves. This study aimed to investigate the extreme wave climate trends in the SWSA using percentile- and storm-based approaches to determine potential coastal impacts. Changes in extreme wave event characteristics were evaluated through distribution maps and directional density distributions. Our results showed an overall increase in the 95 $$^{th}$$ th -percentile of the significant wave height (Hs), mostly in the northern and southern portions of the domain. There was a general increase in the area affected by the events and in their lifetimes in the austral summer. In contrast, winter events had higher maximum intensities, which were not homogeneous throughout the domain. Changes in the wave power direction affected most of the analysed locations, showing a clockwise shift of summer events and a large directional spread of events from the southern quadrant (SW–SE). These changes were related to the southwards shift of the subtropical branch of the storm track, reflecting increased cyclonic activity at 30 $$^° $$ ∘ S (summer) and 45 $$^° $$ ∘ S (winter). These storm track shifts allowed the development of large fetches on the southern edge of the domain, promoting the propagation of long waves.

A study of the simulated climatological January mean upwelling in the northwestern Gulf of Alaska - Nan Yuan; Humio Mitsudera; Hideharu Sasaki (Ocean Dynamics, 2023)
In this research, we studied the upwelling in the northwestern Gulf of Alaska using the climatological January mean and data from the output of the Ocean General Circulation Model for Earth Simulator (OFES2). Specifically, we analyzed the upwelling in the regions where the Alaska Coastal Current (ACC) flows out of the Shelikof Strait (especially the part to the west of Kodiak Island) and where the ACC and the Alaskan Stream (AS) are confluent. In both regions, strong geostrophic currents and downwelling-favorable wind predominate in winter. Furthermore, there are freshwater discharges along the Alaskan coast and an observed mean current vertical shear in the ACC. We revealed that when the internal water stress is larger than the wind stress inside the study regions, this could be decisive in terms of the local horizontal velocity divergence and further upwelling, even if the region is away from the coast and lacks upwelling-favorable wind conditions. Geostrophic stress is part of the internal water stress and is a product of the geostrophic current shear (due to the thermal wind relation) and the vertical viscosity coefficient. The analysis indicated that a front with a large geostrophic stress may act as a “virtual wall” and contribute to local upwelling within a depth of approximately 100 m in the study regions. This process could provide a heuristic for understanding the distribution of pollock in the areas during February and March, which corresponds to the simulated upwelling region.

Three-dimensional structure of summer circulation in the Bohai Sea and its intraseasonal variability - Wenfan Wu; Fangguo Zhai; Cong Liu; Yanzhen Gu; Peiliang Li (Ocean Dynamics, 2023)

Contribution of the wind, Loop Current Eddies, and topography to the circulation in the southern Gulf of Mexico - Erick R. Olvera-Prado; Rosario Romero-Centeno; Jorge Zavala-Hidalgo; Efraín Moreles; Angel Ruiz-Angulo (Ocean Dynamics, 2023)
The Bay of Campeche, located in the southern Gulf of Mexico (GoM), is characterized by a semi-permanent cyclonic circulation commonly referred to as the Campeche Gyre (CG). Several studies documenting its upper layer structure have suggested a possible relationship between its seasonal variability and the wind stress, and that non-seasonal variability arises mainly from the interaction of the gyre with Loop Current Eddies (LCEs) that arrive in the region. Nevertheless, a partition of the contributions of these forcings to the circulation of the CG in a statistically consistent manner is still needed. This study examines the wind- and eddy-driven circulation with long-term numerical simulations of the GoM using the HYbrid Coordinate Ocean Model. Our results show that, in the absence of LCEs, the wind can sustain a seasonal-modulated circulation in the CG, confined within the upper 600 m. When considering LCEs, high fluctuations on the flow at intraseasonal time scales are imposed. We found that the LCEs influence the western Bay of Campeche circulation through two main mechanisms: (a) by decelerating and inhibiting the CG through a positive vorticity flux out of the bay, leading to reversals in the flow if LCE southward penetration is large, or (b) by strengthening the CG when a big cyclone, accompanying the LCE, enters the region. It is proposed that the second mechanism is responsible for inducing a net weak cyclonic circulation in the Bay in the absence of wind. Furthermore, past studies have shown that the CG behaves as an equivalent-barotropic flow, with topography acting to confine the CG to the west of the bay. In our modeling results, the role of topography manifests similarly among the different numerical experiments, resulting in closed geostrophic contours to the west of the bay that confine an upper-layer, nearly-symmetric, equivalent-barotropic CG.

Dynamic interdependence of wind stress and sea state under action of a tropical cyclone moving from deep to shallow waters - Yue Xu; Xiping Yu (Ocean Dynamics, 2023)

In memoriam: Prof. Dr. Jörg-Olaf Wolff (1959–2023) - Tal Ezer (Ocean Dynamics, 2023)

Influence of tropical cyclone Jawad on the surface and sub-surface circulation in the Bay of Bengal: ocean–atmosphere feedback - Tapajyoti Chakraborty; Sandeep Pattnaik; Sudheer Joseph (Ocean Dynamics, 2023)

Evaluation of the applicability of the Ekman theory for wind-driven ocean currents: a comparison with the Mellor–Yamada turbulent model - Tal Ezer (Ocean Dynamics, 2023)

Correction to: Water masses in the Caribbean Sea and sub‑annual variability in the Guajira upwelling region - Rafael Ricardo Torres; Sadid Latandret; Jhon Salon; Claudia Dagua (Ocean Dynamics, 2023)

Assessment of the spatiotemporal variability of seawater temperature and salinity in the Yellow and Bohai seas from multiple high-resolution reanalysis datasets - Yu Yan; Yuqing Zhou; Yingjun Xu; Wei Gu (Ocean Dynamics, 2023)

Effects of vertical mixing on the Lake Michigan food web: an application of a linked end-to-end earth system model framework - H. Zhang; D. M. Mason; N. W. Boucher; E. S. Rutherford; D. J. Cannon; J. Kessler; A. Fujisaki-Manome; J. Wang; E. A. Fulton (Ocean Dynamics, 2023)
Physical processes may affect ecosystem structure and function through the accumulation, transport, and dispersal of organic and inorganic materials, nutrients, and organisms; they structure physical habitat and can influence predator–prey interactions and trophic production. In the Laurentian Great Lakes, horizontal currents generally dominate, but little is known about the effects of vertical mixing on lake food webs. We developed a linked earth system model and used it to explore how vertical mixing affects the productivity of Lake Michigan (LM), the world’s fifth-largest lake, whose food web and fisheries have been adversely affected by invasive Dreissena mussels. We hypothesized that higher vertical mixing would result in higher food web biomass by making phosphorus more available to the lower food web, and that filtration by invasive mussels would counter the effects of mixing and decrease food web biomass. Using linked climate, hydrodynamics, and ecosystem models, we projected the response of LM’s food web to scenarios of different levels of vertical mixing, with and without invasive mussels. Biomass of most functional food web groups increased with increases in vertical mixing, with the greatest increases in phytoplankton and zooplankton. Increased biomass was due to the replenishment of nutrients into the euphotic zone, which enhanced growth and biomass of lower trophic levels through bottom-up effects. However, filtration by invasive mussels reduced the positive effects of mixing for most species. Future applications of the linked earth system framework will explore the effects of climate warming and nutrient reduction on fisheries production to inform fisheries managers.

Altimetry-derived tide model for improved tide and water level forecasting along the European continental shelf - Michael G. Hart-Davis; Stendert Laan; Christian Schwatke; Björn Backeberg; Denise Dettmering; Firmijn Zijl; Martin Verlaan; Marcello Passaro; Florian Seitz (Ocean Dynamics, 2023)
With the continued rise in global mean sea level, operational predictions of tidal height and total water levels have become crucial for accurate estimations and understanding of sea level processes. The Dutch Continental Shelf Model in Delft3D Flexible Mesh (DCSM-FM) is developed at Deltares to operationally estimate the total water levels to help trigger early warning systems to mitigate against these extreme events. In this study, a regional version of the Empirical Ocean Tide model for the Northwest European Continental Sea (EOT-NECS) is developed with the aim to apply better tidal forcing along the boundary of the regional DCSM-FM. EOT-NECS is developed at DGFI-TUM by using 30 years of multi-mission along-track satellite altimetry to derive tidal constituents which are estimated both empirically and semi-empirically. Compared to the global model, EOT20, EOT-NECS showed a reduction in the root-square-sum error for the eight major tidal constituents of 0.68 cm compared to in situ tide gauges. When applying constituents from EOT-NECS at the boundaries of DCSM-FM, an overall improvement of 0.29 cm was seen in the root-mean-square error of tidal height estimations made by DCSM-FM, with some regions exceeding a 1 cm improvement. Furthermore, of the fourteen constituents tested, eleven showed a reduction of RMS when included at the boundary of DCSM-FM from EOT-NECS. The results demonstrate the importance of using the appropriate tide model(s) as boundary forcings, and in this study, the use of EOT-NECS has a positive impact on the total water level estimations made in the northwest European continental seas.

Swell and wind-wave height variability in the East China Sea - Yukiharu Hisaki (Ocean Dynamics, 2023)

Analysis of the dynamic mechanisms of upwelling in deep ocean water caused by typhoons - Famei Lei; Hao Dai; Shaoping Shang; Zhigang He; Shuai Yang (Ocean Dynamics, 2023)

Seasonal variability of eddy characteristics and energetics in the Kuroshio Extension - Chen Yang; Haiyuan Yang; Zhaohui Chen; Bolan Gan; Yongzheng Liu; Lixin Wu (Ocean Dynamics, 2023)

Relationship between coral bleaching and large-scale oscillations in the Lakshadweep archipelago - Ravikumar C. Nair; Muraleedharan KR; Abdul Azeez S; Dinesh Kumar PK (Ocean Dynamics, 2023)

Correction to: Inertial instability and phase error in Euler forward predictorcorrector time integration schemes: Improvement of modeling Great Lakes thermal structure and circulation using FVCOM - Jia Wang; Ayumi Fujisaki‑Manome; James Kessler; David Cannon; Philip Chu (Ocean Dynamics, 2023)

Inertial instability and phase error in Euler forward predictor-corrector time integration schemes: Improvement of modeling Great Lakes thermal structure and circulation using FVCOM - Jia Wang; Ayumi Fujisaki-Manome; James Kessler; David Cannon; Philip Chu (Ocean Dynamics, 2023)
This study investigates the inertial stability properties and phase error of numerical time integration schemes in several widely-used ocean and atmospheric models. These schemes include the most widely used centered differencing (i.e., leapfrog scheme or the 3-time step scheme at n-1, n, n+1 ) and 2-time step ( n, n+1 ) 1 st -order Euler forward schemes, as well as 2 nd -stage and 3 rd - and 4 th -stage Euler predictor-corrector (PC) schemes. Previous work has proved that the leapfrog scheme is neutrally stable with respect to the Coriolis force, with perfect inertial motion preservation, an amplification factor (AF) equal to unity, and a minor overestimation of the phase speed. The 1 st -order Euler forward scheme, on the other hand, is known to be unconditionally inertially unstable since its AF is always greater than unity. In this study, it is shown that 3 rd - and 4 th -order predictor-corrector schemes 1) are inertially stable with weak damping if the Coriolis terms are equally split to n +1 (new value) and n (old value); and 2) introduce an artificial computational mode. The inevitable phase error associated with the Coriolis parameter is analyzed in depth for all numerical schemes. Some schemes (leapfrog and 2 nd -stage PC schemes) overestimate the phase speed, while the others (1 st -order Euler forward, 3 rd - and 4 th -stage PC schemes) underestimate it. To preserve phase speed as best as possible in a numerical model, alternating a scheme that overestimates the phase speed with a scheme that underestimates the phase speed is recommended. Considering all properties investigated, the leapfrog scheme is still highly recommended for a time integration scheme. As an example, a comparison between a leapfrog scheme and a 1 st -order Euler forward scheme is presented to show that the leapfrog scheme reproduces much better vertical thermal stratification and circulation in the weakly-stratified Great Lakes.

The role of stratification and initial conditions on the propagation and decay of near-inertial waves on a $$β $$-plane - Siva Heramb Peddada; Vamsi Krishna Chalamalla (Ocean Dynamics, 2023)

Simulating flood events at the Twin Ports of Duluth-Superior using a linked hydrologic-hydrodynamic framework - Lindsay Fitzpatrick; Daniel Titze; Eric J. Anderson; Dmitry Beletsky; John G. W. Kelley (Ocean Dynamics, 2023)
Generally, ports in the North American Great Lakes are not supported with navigational guidance (water level, water temperature, currents, ice) by NOAA’s Great Lakes Operational Forecast System (GLOFS). To examine the benefit of extending model coverage to this critical infrastructure, a linked hydrologic-hydrodynamic framework was developed for the Twin Ports of Duluth-Superior in western Lake Superior, and tested over three case studies of flooding due to storm surge and/or river flooding. Streamflow from 22 National Water Model (NWM) simulated and 3 gauged inflows within the domain was injected into a hydrodynamic model built on the Finite Volume Community Ocean Model (FVCOM), with a wet-dry grid that covered the harbor and surrounding floodplain. Model results from flood simulations compared well against time-series of water level and streamflow at gauges within the harbor, with root mean square error (RMSE) and bias values small relative to the typical fluctuations. Inclusion of NWM-simulated tributaries improved the accuracy of modeled water levels in the harbor, and increased simulated current speeds in navigational channels by up to 0.5 ms −1 . Modeled inundation extent in the floodplain closely matched flood extent surveys conducted in response to a record flood event in 2012, demonstrating the capability of the modeling framework to provide flood guidance in the complex coastal setting.

Numerical study on the influence of internal tides on tropical-cyclone-induced sea surface temperature cooling in the South China Sea - Shukui Cheng; Anzhou Cao; Hailun He; Peiliang Li; Jinbao Song (Ocean Dynamics, 2023)

The changes in La Niña induced summertime interannual variability of sea level anomaly along the western boundary of the Bay of Bengal - Arnab Mukherjee; Supriyo Ghosh (Ocean Dynamics, 2023)

A dynamic 2DH flocculation model for coastal domains - Sebastian Escobar; Qilong Bi; Michael Fettweis; Samor Wongsoredjo; Jaak Monbaliu; Erik Toorman (Ocean Dynamics, 2023)

Evolution of narrow-band spectrum of two random Stokes wavetrains in deep water - Sourav Halder; Asoke Kumar Dhar (Ocean Dynamics, 2023)

Predicting significant wave height with artificial neural networks in the South Atlantic Ocean: a hybrid approach - Paula Marangoni Gazineu Marinho Pinto; Ricardo Martins Campos; Marcos Nicolas Gallo; Carlos Eduardo Parente Ribeiro (Ocean Dynamics, 2023)

On the rapid weakening of super-cyclone Amphan over the Bay of Bengal - Neethu Chacko (Ocean Dynamics, 2023)

Non-linear interactions between tides and storm surges during extreme weather events over the eastern Canadian shelf - Shengmu Yang; Jinyu Sheng; Kyoko Ohashi; Bo Yang; Shengli Chen; Jiuxing Xing (Ocean Dynamics, 2023)

Cold blobs in the subpolar North Atlantic: seasonality, spatial pattern, and driving mechanisms - Jian Shi; Jiaqi Wang; Zixuan Ren; Cong Tang; Fei Huang (Ocean Dynamics, 2023)

July 2020 heavy rainfall in Japan: effect of real-time river discharge on ocean circulation based on a coupled river-ocean model - Yu-Lin K. Chang; Sergey M. Varlamov; Xinyu Guo; Toru Miyama; Yasumasa Miyazawa (Ocean Dynamics, 2023)
In July 2020, a stationary atmospheric front over Japan caused persistent, nearly continuous rain for most of the month that resulted in new historical highest rainfall records in several areas and caused serious river floods, landslides, and debris-flow events. An existing hindcast and forecast ocean circulation model that includes climatological discharge information of major rivers failed to represent the extreme river discharge under heavy rainfall. New experiments were conducted using real-time river discharge information based on Today's Earth CaMa-Flood simulation that includes 368 rivers in Japan. The inclusion of real-time river discharge improved the salinity bias in the near-surface waters. The differences were significant compared to the observations in the heavy rain region (i.e., Ariake Bay and Tosa Bay), and insignificant at offshore stations. The ensemble experiments of real-time river discharge cases suggested the difference between the climatological and the real-time river discharge experiments was not random, but was robust. The freshening water changed the shelf circulation, and its far-reaching effect appeared hundreds of kilometers away from the shore. Passive particle tracking was conducted for examining the cross-shelf exchange. More particles released from Bungo Channel went offshore in near-surface water when the real-time river discharge was used compared to using the climatology discharge. Particles released in Tosa Bay, Seto Inland Sea, and Kii Channel showed the opposite tendency. The real-time river discharge not only changed the modeled coastal salinity distribution, but also the coastal and offshore currents. The role of the real-time river discharge on modeling normal flow periods or drought events, and its influence on a longer time scale model simulation remain to be explored.

Development and skill assessment of a real-time hydrologic-hydrodynamic-wave modeling system for Lake Champlain flood forecasting - Daniel Titze; Dmitry Beletsky; Jesse Feyen; William Saunders; Lacey Mason; James Kessler; Philip Chu; Deborah Lee (Ocean Dynamics, 2023)

Lake ice simulation using a 3D unstructured grid model - Yinglong Joseph Zhang; Chin Wu; Joshua Anderson; Sergey Danilov; Qiang Wang; Yuli Liu; Qian Wang (Ocean Dynamics, 2023)

Modeling changes in ice dynamics and subsurface thermal structure in Lake Michigan-Huron between 1979 and 2021 - David Cannon; Ayumi Fujisaki-Manome; Jia Wang; James Kessler; Philip Chu (Ocean Dynamics, 2023)
The world’s largest lakes, including the Laurentian Great Lakes, have experienced significant surface warming and loss of ice cover over the last several decades. Although changing surface conditions have received substantial research interest, changes below the surface remain largely unexplored, despite their importance for turbulent mixing, nutrient cycling, and primary production. In this study, we investigate changes in subsurface thermal structure and timing in Lake Michigan-Huron related to ongoing climate warming. This work utilizes atmospheric reanalysis data to drive the Great Lakes Finite Volume Community Ocean Model (GL-FVCOM), providing three-dimensional hydrodynamic and ice simulations between 1979 and 2021. Results are used to analyze trends in ice and temperature dynamics, revealing significant changes in annually averaged ice cover (− 2.1– − 5.2%/decade), ice thickness (− 0.68 – − 2.0 cm/decade), surface temperature (+ 0.47– + 0.51 $$^°{\rm C}$$ ∘ C /decade), and bottom temperature (+ 0.26– + 0.29 $$^°{\rm C}$$ ∘ C /decade) over the last 40 years, especially in ecologically important bays (e.g., Green Bay, Saginaw Bay). Significant warming was observed at all depth layers (0–270 m), with warming trends in the epilimnion and hypolimnion that agreed well with recent analysis of observational data in Lake Michigan. Shifting stratification dynamics led to dramatic changes in modelled overturning behavior, and earlier spring turnover dates (− 2.2– − 7.5 days/decade) and later fall turnover dates (+ 2.5– + 6.3 days/decade) led to a net lengthening of the stratified period. This study presents one of the most comprehensive analyses of changes in Great Lakes subsurface temperatures to date, providing important context for future climate modelling and coastal management efforts in the region.

Intraseasonal variability of subsurface ocean temperature anomalies in the Indian Ocean during the summer monsoon season - Gopinadh Konda; Venkata Sai Gulakaram; Naresh Krishna Vissa (Ocean Dynamics, 2023)

Combined effects of climatic factors on extreme sea level changes in the Northwest Pacific Ocean - Linlin Fan; Ling Du (Ocean Dynamics, 2023)

Internal tides in the central Mediterranean Sea: observational evidence and numerical studies - P. Oddo; P. M. Poulain; S. Falchetti; A. Storto; G. Zappa (Ocean Dynamics, 2023)
Internal tides are studied in the central Mediterranean Sea using observational data and numerical experiments. Both numerical results and observations indicate that the baroclinic variability in this area is dominated by the K1 diurnal tide. In agreement with previous studies, the diurnal internal tides have the characteristics of Kelvin-like bottom trapped waves. They are mainly generated by the interaction of the induced barotropic tidal flow with the steep bathymetric gradient connecting the Ionian Sea with the shallow Sicily Channel. The bathymetric gradient appears to be the major forcing shaping the propagation paths of the internal tides. The most energetic internal tides follow the steep bathymetric gradient, propagating southward and tending to dissipate rapidly. Other waves cross the continental shelf south of Malta and then split with one branch moving toward the southern coast of Sicily and the other moving toward the west. Internal tides propagate with a variable phase velocity of about 1 ms −1 and a wavelength of the order of 100 km. During their journey, the internal waves appear to be subject to local processes that can modify their characteristics. The induced vertical shear strongly dominates the vertical turbulence and generates vertical mixing that alters the properties of the water masses traversing the area. Barotropic and internal tides remove heat from the ocean surface, increasing atmospheric heating, and redistributing energy through increased lateral heat fluxes. Lateral heat fluxes are significantly greater in the presence of internal tides due to the simultaneous increase in volume fluxes and water temperatures.

LORA: a local ensemble transform Kalman filter-based ocean research analysis - Shun Ohishi; Takemasa Miyoshi; Misako Kachi (Ocean Dynamics, 2023)
We have produced an eddy-resolving local ensemble transform Kalman filter (LETKF)-based ocean research analysis (LORA) for the western North Pacific (WNP) and Maritime Continent (MC) regions (LORA-WNP and LORA-MC, respectively). This paper describes the system configuration and validation comparisons with Japan Coastal Ocean Predictability Experiment 2M (JCOPE2M) reanalysis and Archiving, Validation, and Interpretation of Satellite Oceanographic Data (AVISO) observational datasets. The results show that the surface horizontal velocity in the LORA-WNP is closer to independent drifter buoy observations in the mid-latitude region, especially along the Kuroshio Extension (KE), and is less close in the subtropical region than the JCOPE2M, although the AVISO is the closest over the whole domain. The sea surface temperatures (SSTs) in the LORA-WNP correspond better to assimilated satellite observations than the JCOPE2M over most of the domain except for coastal regions. The results using an independent buoy south of the KE indicate that better fit of temperature in the LORA-WNP may be limited to the upper 300 m depth, probably because of the prescribed vertical localization cutoff length of 370 m. In the MC region, the surface velocity in the LORA-MC is closer to the independent drifter buoys in the equatorial coastal region and is less close in the offshore region than the AVISO. The SSTs in the LORA-MC correspond better to the assimilated satellite observations in the offshore region than the nearshore region. Therefore, the LORA-WNP and LORA-MC have sufficient accuracy for geoscience research applications as well as for fisheries, marine transport, and environment consultants.

Water masses in the Caribbean Sea and sub-annual variability in the Guajira upwelling region - Rafael Ricardo Torres; Sadid Latandret; Jhon Salon; Claudia Dagua (Ocean Dynamics, 2023)
The study of water masses is important as they transport water properties affecting the biosphere and ocean dynamics. In this study, we revisit water masses in the Caribbean Sea using climatology and 11 months of observations at different depths from 3 moorings placed in the Guajira upwelling region, providing some new findings. The Caribbean Surface Water (CSW) seasonal variability is studied at the mixed layer depth. Salinity differences between CSW and the saltier North Atlantic Subtropical Underwater (SUW) determine static stability spatial and temporal variations, with implications for regional ocean dynamics. Besides, we assess the climatologic distribution of water masses below the salinity maximum using the optimum multiparameter analysis and the Thermodynamic Equation of Seawater 2010, defining their source water indices when entering the Caribbean Sea. The SUW, with its core at ~ 150 m depth, occupies 16% of the Caribbean Sea volume, complemented by 38% of Antarctic Intermediate Water, with its core at ~ 700 m depth and North Atlantic Deep Water, which as bottom water occupies 46% of the volume. Hydrographic observations do not differ from climatology, regardless of their large sub-annual variations decreasing with depth. Daily time series of dominant water fractions at different depths correlate at each mooring, indicating a common forcing. Besides, rotated wind stress, which is an indicator of the Guajira upwelling, correlates regularly with water mass fractions down to 700 m depth. However, during strong wind shifts, upwelling seems to affect them down to 1450 m depth.

On the potential of mapping sea level anomalies from satellite altimetry with Random Forest Regression - Marcello Passaro; Marie-Christin Juhl (Ocean Dynamics, 2023)
The sea level observations from satellite altimetry are characterised by a sparse spatial and temporal coverage. For this reason, along-track data are routinely interpolated into daily grids. These grids are strongly smoothed in time and space and are generated using an optimal interpolation routine requiring several pre-processing steps and covariance characterisation. In this study, we assess the potential of Random Forest Regression to estimate daily sea level anomalies. Along-track sea level data from 2004 are used to build a training dataset whose predictors are the neighbouring observations. The validation is based on the comparison against daily averages from tide gauges. The generated dataset is on average 10% more correlated to the tide gauge records than the commonly used product from Copernicus. While the latter is more optimised for the detection of spatial mesoscales, we show how the methodology of this study has the potential to improve the characterisation of sea level variability.

Energetics during eddy shedding in the Gulf of Mexico - Haiyuan Yang; Chen Yang; Yongzheng Liu; Zhaohui Chen (Ocean Dynamics, 2023)
Using the Estimating Circulation and Climate of the Ocean (ECCO) Phase II product, this study investigates the energetic characteristics during eddy shedding in the Gulf of Mexico. Based on the sea level anomaly data between 1992 and 2016, a total of 34 eddy shedding events are identified. Drawing on multiscale energy and vorticity analysis method, the eddy kinetic energy (EKE) budgets are diagnosed based on the ensemble of 34 eddy shedding events. During the stage of eddy shedding, barotropic instability (BT) dominates the energy budget. Meanwhile, energy transfers from upper layer to the deep layer by vertical pressure work (PW), which is the main source of abyssal EKE. Before eddy detachment, cyclonic eddy appears at the southeastern side of the Loop Current. Even though buoyancy forcing (BF) dominates the energy budget, BT makes considerable contribution to the generation of cyclonic eddy. Baroclinic instability (BC) shares the similar horizontal distribution with BF which accounts for 32% of the value of BC.

Forecasting marine debris spill accumulation patterns in the south-eastern Australia water: an intercomparison between global ocean forecast models - Fanglou Liao; Xiao Hua Wang; Erick Fredj (Ocean Dynamics, 2023)

A comparative study of sea surface wind datasets and their induced circulation characteristics in the North Pacific Ocean - Dingqi Wang; Guohong Fang; Tengfei Xu; Shumin Jiang; Fei Teng; Ting Qiu; Zexun Wei; Yonggang Wang (Ocean Dynamics, 2023)

Sea level acceleration and variability in the Chesapeake Bay: past trends, future projections, and spatial variations within the Bay - Tal Ezer (Ocean Dynamics, 2023)

Thank you to 2022 Ocean Dynamics reviewers - Tal Ezer; Sandro Carniel; Chabchoub Amin; Ricardo de Camargo; Sheila N. Estrada-Allis; Guoping Gao; Richard J. Greatbatch; Pierre F. J. Lermusiaux; Zhiyu Liu; Yasumasa Miyazawa; Alejandro Orfila Forster; Swapna Panickal; et al. (Ocean Dynamics, 2023)

Initial formation of channel–shoal patterns in double–inlet systems - Xiao Deng; Tom De Mulder; Henk Schuttelaars (Ocean Dynamics, 2023)

Multiple equilibrium states of the Gulf of Mexico Loop Current - Vitalii A. Sheremet; Arham Amin Khan; Joseph Kuehl (Ocean Dynamics, 2022)

Bioluminescence potential during polar night: impact of behavioral light sensitivity and water mass pathways - Igor Shulman; Jonathan H. Cohen; Mark A. Moline; Stephanie Anderson; E. Joseph Metzger; Bradley Penta (Ocean Dynamics, 2022)
During polar nights of 2012 and 2017, bioluminescence (BL) potential surveys demonstrated high emissions at depths around and below 100 m at offshore stations to the north of a Svalbard fjord (Rijpfjorden). We demonstrated that the highest bioluminescent emissions for offshore stations are located at depths below depths of modelled/ambient light intensities corresponding to the reported irradiance thresholds for the behavioral light sensitivity of krill and copepods, and suggest that behavioral light sensitivity is one of the reasons for high values of BL potential observed below 100 m at offshore stations. In order to understand sources of bioluminescent taxa responsible for the observed high values of BL potential in offshore waters, we have investigated the origin and pathways of water masses circulating to the north, offshore of the fjord Rijpfjorden by using a hydrodynamic model. For both 2012 and 2017, the model water masses mostly originate from the west, where the Atlantic water is flowing northward, then along the shelf and shelf slope of northern Svalbard, and to the offshore of the fjord. This indicates that the advection of zooplankton by North Atlantic Water is one possible source of bioluminescent organisms offshore of northern Svalbard. In 2012, water masses also originated from the inflow through Hinlopen trench and strait, while, in 2017, the offshore water was advected and upwelled into the fjord on time scales less than 10 days, and after that there was a recirculation back from the fjord to offshore on time scales larger than 10 days. This recirculation from the fjord might be another source of bioluminescent organisms in the offshore waters.

A study of the sea level and current effects on the sea state in Galway Bay, using the numerical model COAWST - Clément Calvino; Tomasz Dabrowski; Frédéric Dias (Ocean Dynamics, 2022)

Optimally growing initial error for predicting the sudden shift in the Antarctic Circumpolar Current transport and its application to targeted observation - Li Zhou; Kun Zhang; Qiang Wang; Mu Mu (Ocean Dynamics, 2022)

Sea level variability in the Gulf of Mexico since 1900 and its link to the Yucatan Channel and the Florida Strait flows - Tal Ezer (Ocean Dynamics, 2022)

The limits to growth: how large can subaqueous, flow-transverse bedforms ultimately become? - Burg Flemming (Ocean Dynamics, 2022)
Based on field and experimental evidence, the average initial spacing (seed wavelength) of flow-transverse bedforms (ripples and dunes) appears to lie between 80 and 130 grain diameters ( L = 80–130 D mm ). Starting with an average initial spacing of L = 100 D mm , subsequent bedform growth proceeds by amalgamation of two successive bedforms, which results in a doubling of the spacing in each step. Geometric principles dictate that the combined volume of two smaller bedforms lacks about 40% of the volume required for a fully developed amalgamated bedform. The missing volume is gained by excavation of the troughs, i.e., by lowering the base level. Where base level lowering is prevented by the presence of a coarse-grained armor layer or hard ground pavement, the larger amalgamated bedform remains sediment starved. In its simplest form, bedform growth proceeds by continuous doubling of the spacing in response to increases in flow velocity, the process being reversible in response to flow decelerations. Bedform growth terminates when the shear velocity ( u * ) at the crest reaches the mean settling velocity ( w s ) of the sediment. At this point, 40% of the bed material is in suspension, at which point the missing volume can no longer be compensated by trough excavation. In shallow water, maximum bedform size is dictated by the water depth, whereas in deep water, bedforms can potentially grow to their ultimate size. Evaluation of bedform data from deep water settings suggests that the largest two-dimensional, flow-transverse bedforms in terms of grain size (phi) can be approximated by the equations: ln L max = 13.72–4.03 D phi and ln H max = 9.95–3.47 D phi for grain sizes < ~ 0.2 mm (> ~ 2.32 phi), with L and H representing bedform spacing and height in meters and D the grain size in phi. For grain sizes > ~ 0.2 mm (< ~ 3.23 phi), the corresponding relationships are ln L max = 6.215–0.69 D phi and ln H max = 3.18–0.56 D phi , with notations as before, or in terms of grain diameters in mm: L max = 5 × 10 5 D mm .

An analytical solution to wave dissipation induced by interacting waves and currents with muddy deposits - Kamrooz Mahshid; Sarmad Ghader; S. Hadi Shamsnia; S. Abbas Haghshenas (Ocean Dynamics, 2022)

Turbulent dissipation rates across the Summer Monsoon Current - Anoop A. Nayak; Vinayachandran P. N.; Jenson V. George (Ocean Dynamics, 2022)

Mesoscale eddy variability in the Caribbean Sea - Margarita E. López-Álzate; Juan-Manuel Sayol; Ismael Hernández-Carrasco; Andrés F. Osorio; Evan Mason; Alejandro Orfila (Ocean Dynamics, 2022)
The spatial distribution, and the monthly and seasonal variability of mesoscale eddy observations derived from the AVISO eddy atlas are assessed in the Caribbean Sea during 1993–2019. The average lifetime for the whole set of eddies is 62 ± 37 days, mean amplitude of 7 ± 4 cm for cyclonic and 7 ± 4 cm for anticyclonic and mean radius of 100 ± 31 km for cyclonic and 108 ± 32 km for anticyclonic. Cyclonic eddies are on average more nonlinear than anticyclonic ones. The spatio-temporal variability in the number of eddy observations is evaluated against the Mean Eddy Kinetic Energy (MEKE) derived from geostrophic currents as well as from seasonal winds. Spatial distribution of eddy observations is correlated with MEKE while the migration of the intertropical convergence zone explains the advection of eddies towards the southern part of the basin.

Super-resolution data assimilation - Sébastien Barthélémy; Julien Brajard; Laurent Bertino; François Counillon (Ocean Dynamics, 2022)
Increasing model resolution can improve the performance of a data assimilation system because it reduces model error, the system can more optimally use high-resolution observations, and with an ensemble data assimilation method the forecast error covariances are improved. However, increasing the resolution scales with a cubical increase of the computational costs. A method that can more effectively improve performance is introduced here. The novel approach called “Super-resolution data assimilation” (SRDA) is inspired from super-resolution image processing techniques and brought to the data assimilation context. Starting from a low-resolution forecast, a neural network (NN) emulates the fields to high-resolution, assimilates high-resolution observations, and scales it back up to the original resolution for running the next model step. The SRDA is tested with a quasi-geostrophic model in an idealized twin experiment for configurations where the model resolution is twice and four times lower than the reference solution from which pseudo-observations are extracted. The assimilation is performed with an Ensemble Kalman Filter. We show that SRDA outperforms both the low-resolution data assimilation approach and a version of SRDA with cubic spline interpolation instead of NN. The NN’s ability to anticipate the systematic differences between low- and high-resolution model dynamics explains the enhanced performance, in particular by correcting the difference of propagation speed of eddies. With a 25-member ensemble at low resolution, the SRDA computational overhead is 55% and the errors reduce by 40%, making the performance very close to that of the high-resolution system (52% of error reduction) that increases the cost by 800%. The reliability of the ensemble system is not degraded by SRDA.

The future projection of cyclones in Bay of Bengal: a study using coupled ocean atmosphere model - P V Kiran; C Balaji (Ocean Dynamics, 2022)

Relative current effect on short wave growth - Pedro Veras Guimarães; Fabrice Ardhuin; Yves Perignon; Alvise Benetazzo; Marie-Noëlle Bouin; Valerie Garnier; Jean-Luc Redelsperger; Mickael Accensi; Jim Thomson (Ocean Dynamics, 2022)

JCOPE-FGO: an eddy-resolving quasi-global ocean reanalysis product - Shoichiro Kido; Masami Nonaka; Yasumasa Miyazawa (Ocean Dynamics, 2022)
In the present research, we provide a brief description and assessment of the oceanic fields analyzed in the newly developed eddy-resolving quasi-global ocean reanalysis product, named the Japan Coastal Ocean Predictability Experiments-Forecasting Global Ocean (JCOPE-FGO). This product covers the quasi-global ocean with a horizontal resolution of 0.1° × 0.1°. Validations of analyzed temperature and salinity fields by JCOPE-FGO against in situ observations revealed that our product can capture various aspects of observed hydrographic structures in the world ocean, including frontal structures near the surface and thermohaline properties of water masses, as well as their spatiotemporal variability. Furthermore, we have assessed dynamical fields analyzed in JCOPE-FGO using satellite altimeters and surface drifters, and found that our product can represent the mean state and variability of the upper ocean circulation in many regions. A notable feature of JCOPE-FGO is the inclusion of an updated global river runoff, and impacts of river forcing have been assessed by an additional reanalysis experiment without river forcing. We found that the removal of continental river discharge leads to dramatic changes in the near-surface salinity and related fields around river mouths of large rivers, but large changes are mostly confined to narrow regions near the coast. As an example of the substantial impact of river runoff, we discuss the dispersion of low-salinity water from the Mississippi river to the Gulf of Mexico: a comparison between the analyzed salinity fields from both reanalysis products with those from satellite observations demonstrated that the inclusion of river runoff is essential for an accurate representation of its seasonal variability. Several key issues that warrant further improvements are discussed for future development.

Tidal dissipation from free drift sea ice in the Barents Sea assessed using GNSS beacon observations - Amey Vasulkar; Martin Verlaan; Cornelis Slobbe; Lars Kaleschke (Ocean Dynamics, 2022)
One of the major challenges facing global hydrodynamic tidal models is the modelling of the interaction between sea ice and tides in high-latitude waters. Recent studies have shown strong seasonal correlation between sea ice and tides. Hence, it is important to accurately model the effect of sea ice in a tidal model. Presence of sea ice leads to a frictional dissipation of tides. Most models either completely ignore sea ice or partly include it by assuming a fixed sea ice cover (landfast ice). However, sea ice can also be drifting and the nature of dissipation between drifting sea ice and tides is partly unknown. We assess the dissipation of tides due to free drift sea ice. In the absence of wind, this is negligible in the deeper and open ocean. For the shallow water regions, however, this dissipation is unknown. Here, we evaluate this dissipation for the Spitzbergen Shelf region using a beacon dataset showing strong free drift subdaily sea ice oscillations and a physics based point ice model. Two analyses were done which compared the model and observed motion. The analyses showed that for winds speeds below 8m/s and with low subdaily signals, the subdaily free drift sea ice motion is strongly connected to the tides and that the frictional dissipation is low. In the context of global tide and storm surge models, the dissipation from free drift sea ice on tides should be evaluated based on the region (deep ocean or shallow water) and existing wind conditions. In the presence of strong winds the dissipation between free drift sea ice and air can be significant on a subdaily scale even if there are no subdaily signals in the wind itself.

Mathematical modelling of Visakhapatnam Port utilizing the porous and non-porous breakwaters with finite depth green function - Prashant Kumar; Prachi Priya; Rajni (Ocean Dynamics, 2022)

Numerical investigation on the effectiveness of pile row in local sand trapping and beach protection - Xiaojian Liu; Peng Hou; Zihao Duan; Chunhua Huang; Cheng Liu; Yong He; Huiqun Guo; Bin Wang; Shijun Wang; Qisong Wang; Xiaowei Zhu; Wancheng Yuan; et al. (Ocean Dynamics, 2022)

Investigating the robustness of the intraseasonal see-saw in the Indo-Pacific barotropic sea level across models - M. Afroosa; B. Rohith; Arya Paul; Fabien Durand; Romain Bourdallé-Badie; Sudheer Joseph; S. Prerna; S. S. C. Shenoi (Ocean Dynamics, 2022)

Wave power trends along the U.S. coastline: in situ measurements and model hindcast estimates - Candice Hall; Robert E. Jensen; David W. Wang (Ocean Dynamics, 2022)
Observational data are successfully assessed to investigate wave power (wave energy flux per unit of wave-crest) trends within four coastal regions around the US, a parameter that is deemed vital to those responsible for coastal protection and community resilience. This study tests for shifting observational inter-annual wave power trends using a newly developed, unique, United States Army Corps of Engineers Quality Controlled Consistent Measurement Archive, and offers a viable methodology to remove documented observational time series data discontinuations. This study is one of the first to show spatially and temporally comparative observational and model wave power results, providing new information on the accuracy of model wave power estimates, while showcasing in situ wave power trends at 29 sites around the U.S. coastline. Overall, the majority of the eastern Pacific Ocean and Hawaii wave power trends are downward, with mixed slope wave power trends apparent within the Atlantic Ocean and the Gulf of Mexico. Observational and model results are similar with respect to timing, but not magnitude, of wave power peaks in long-term inter-annual trends, with the moored buoy data presenting smaller wave power ranges for two (eastern Pacific Ocean and Hawaii) of the four regions. Additionally, the detection of a noticeable variability in the wave power trend direction within each region suggests that site-specific wave power trends should not be generalised to represent a large region. This work demonstrates that observational data are essential in local and regional wave climate studies to accurately estimate wave power for coastal planners and engineers.

An efficient method to improve travel time delays of transoceanic tsunamis based on depth-correction scheme - Peitao Wang; Lining Sun; Lianda Zhao (Ocean Dynamics, 2022)

Odyssey of Aleutian eddies - Maxim V. Budyansky; Sergey V. Prants; Michael Yu Uleysky (Ocean Dynamics, 2022)

Investigation of waves in Sanmen Bay during typhoons and their influence on moored vessels - Yang Zhou; Feng Wang; Junbiao Zhang; Xinglan Bai; Zizeng Wang (Ocean Dynamics, 2022)

Potential sea-level rise effects on the hydrodynamics and transport processes in Hudson–Raritan Estuary, NY–NJ - Sajjad Feizabadi; Yashar Rafati; Masoud Ghodsian; Ali Akbar Salehi Neyshabouri; Maryam Abdolahpour; Ahmad Rezaee Mazyak (Ocean Dynamics, 2022)

Propagation of barotropic Kelvin waves around Antarctica - David J. Webb; Ryan M. Holmes; Paul Spence; Matthew H. England (Ocean Dynamics, 2022)
Barotropic (i.e., depth-uniform) coastal oceanic Kelvin waves can provide rapid teleconnections from climate and weather events in one location to remote regions of the globe. Studies suggest that barotropic Kelvin waves observed around Antarctica may provide a mechanism for rapidly propagating circulation anomalies around the continent, with implications for continental shelf temperatures along the West Antarctic Peninsula and thus Antarctic ice mass loss rates. However, how the propagation of Kelvin waves around Antarctica is influenced by features such as coastal geometry and variations in bathymetry remains poorly understood. Here we study the propagation of barotropic Antarctic Kelvin waves using a range of idealized model simulations. Using a single-layer linear shallow water model with 1 ∘ horizontal resolution, we gradually add complexity of continental configuration, realistic bathymetry, variable planetary rotation, and forcing scenarios, to isolate sources and sinks of wave energy and the mechanisms responsible. We find that approximately 75 % of sub-inertial barotropic Kelvin wave energy is scattered away from Antarctica as other waves in one circumnavigation of the continent, due mostly to interactions with bathymetry. Super-inertial barotropic Kelvin waves lose nearly 95 % of their energy in one circumpolar loop, due to interactions with both coastal geometry and bathymetry. These results help to explain why only sustained signals of low-frequency resonant barotropic Kelvin waves have been observed around Antarctica, and contribute to our understanding of the role of rapid, oceanic teleconnections in climate.

Physical drivers of pelagic sargassum bloom interannual variability in the Central West Atlantic over 2010–2020 - Nikolaos Skliris; Robert Marsh; Kwasi Appeaning Addo; Hazel Oxenford (Ocean Dynamics, 2022)
Since 2011, unprecedented pelagic sargassum seaweed blooms have occurred across the tropical North Atlantic, with severe socioeconomic impacts for coastal populations. To investigate the role of physical drivers in post-2010 sargassum blooms in the Central West Atlantic (CWA), conditions are examined across the wider tropical North Atlantic, using ocean and atmospheric re-analyses and satellite-derived datasets. Of particular consequence for the growth and drift of sargassum are patterns and seasonality of winds and currents. Results suggest that in years of exceptionally large sargassum blooms (2015, 2018), the Intertropical Convergence Zone (ITCZ), an area of maximum wind convergence where sargassum naturally accumulates, shifted southward, towards nutrient-rich waters of the Amazon River plume and the equatorial upwelling zone further stimulating sargassum growth. These changes are associated with modes of natural variability in the tropical Atlantic, notably a negative phase of the Atlantic Meridional Mode (AMM) in 2015 and 2018, and a positive phase of the Atlantic Niño in 2018. Negative AMM in these 2 years is also associated with stronger trade winds and enhanced northwest Africa upwelling, probably resulting in stronger southwestward nutrient transport into the eastern part of CWA. Moreover, in contrast with most years, important secondary winter blooms took place in both 2015 and 2018 in the northern part of CWA, associated with excessive wind-driven equatorial upwelling and anomalously strong northwestward nutrient transport.

Sedimentological data-driven bottom friction parameter estimation in modelling Bristol Channel tidal dynamics - Simon C. Warder; Athanasios Angeloudis; Matthew D. Piggott (Ocean Dynamics, 2022)
Accurately representing the bottom friction effect is a significant challenge in numerical tidal models. Bottom friction effects are commonly defined via parameter estimation techniques. However, the bottom friction coefficient (BFC) can be related to the roughness of the sea bed. Therefore, sedimentological data can be beneficial in estimating BFCs. Taking the Bristol Channel and Severn Estuary as a case study, we perform a number of BFC parameter estimation experiments, utilising sedimentological data in a variety of ways. Model performance is explored through the results of each parameter estimation experiment, including applications to tidal range and tidal stream resource assessment. We find that theoretically derived sediment-based BFCs are in most cases detrimental to model performance. However, good performance is obtained by retaining the spatial information provided by the sedimentological data in the formulation of the parameter estimation experiment; the spatially varying BFC can be represented as a piecewise-constant field following the spatial distribution of the observed sediment types. By solving the resulting low-dimensional parameter estimation problem, we obtain good model performance as measured against tide gauge data. This approach appears well suited to modelling tidal range energy resource, which is of particular interest in the case study region. However, the applicability of this approach for tidal stream resource assessment is limited, since modelled tidal currents exhibit a strong localised response to the BFC; the use of piecewise-constant (and therefore discontinuous) BFCs is found to be detrimental to model performance for tidal currents.

Evaluation of mixing schemes in the HYbrid Coordinate Ocean Model (HYCOM) in the tropical Indian Ocean - Vijay Pottapinjara; Sudheer Joseph (Ocean Dynamics, 2022)

Changes in tidal asymmetry in the German Wadden Sea - Robert Hagen; Christian Winter; Frank Kösters (Ocean Dynamics, 2022)
The recent morphological development of the German Wadden Sea (North Sea, Europe) has been characterized by expanding intertidal flats and deepening, narrowing tidal channels at declining subtidal volume. This study analyzes the effect of these changes on tidal asymmetry, based on numerical modeling with high-resolution bathymetry data, and discusses possible adaptations of the import and export behavior in intertidal systems. As common descriptors of tidal asymmetry may show a high spatial variability in bathymetrically complex intertidal systems, we develop a novel subregion averaging approach for a more robust trend estimation. Our data reveal a statistically significant decrease in flood and flood current duration in the period from 1996 to 2016 resulting in declining flood dominance or enhanced ebb dominance in most tidal basins of the German Wadden Sea. Mean and peak current asymmetry also indicate significant decreases in mean flood current magnitude. We relate decreasing flood dominance mostly to local bathymetric volume changes rather than tidal amplitude. However, it appears likely that the sum of local effects facilitates the adaptation of regional tidal dynamics which affects especially the northern German Bight. This regional shift is explained by the deceleration of rising tides due to increased friction on laterally expanded intertidal flats and decreased subtidal channel volume. The decrease in flood or increase in ebb dominance, respectively, indicates that the recent trend of sediment accretion in Wadden Sea areas may cease soon.

Seasonal and spatial variations in spice generation in the South Indian Ocean salinity maxima - Madhu Kaundal; Nadimpalli Jithendra Raju; Dhrubajyoti Samanta; Mihir Kumar Dash (Ocean Dynamics, 2022)

High-resolution downscaling of CMEMS oceanographic reanalysis in the area of the Tuscany Archipelago (Italy) - Michele Bendoni; Maria Fattorini; Stefano Taddei; Carlo Brandini (Ocean Dynamics, 2022)
A native nested configuration of the ROMS model is implemented on the marine area between the Ligurian and Tyrrhenian basins, which includes the Tuscany Archipelago. Initial and boundary conditions are provided by the CMEMS Mediterranean Sea Physical Reanalysis product (1/16°), feeding the parent ROMS model (BLUE, 1/72°), in which a high-resolution grid is nested (PURPLE, 1/216°). Atmospheric forcing comes from a downscaled version of ERA5 reanalysis. Temperature and salinity profiles from gliders and floats, and HF-radar-derived surface currents, are compared to model outputs within the high-resolution area for the whole year 2017. Results show the downscaling procedure is able to reduce model errors for temperature profiles, whereas errors in salinity profiles remain comparable. However, the downscaled model cannot recover large errors inherited from the parent one. The mean bias largest values found in both temperature and salinity profiles may be explained by a model underestimation of the depth of stable stratification limit with respect to field data. Errors in surface currents are reduced for the downscaled dynamics and appear to be uncorrelated to the original CMEMS product, being surface dynamics less affected by initial condition than by atmospheric forcing. A simple scalar metric, to quantify the error in the surface current vector fields from observations and models, is proposed. The novel metric allows to better quantify the improvement gained by the downscaling procedure.

Spatial variability of currents associated with different cold fronts along the southern Texas coast - Angélica Romero-Arteaga; Amaia Ruiz de Alegría-Arzaburu (Ocean Dynamics, 2022)

Analysis of the annual mean energy cycle of the Black Sea circulation for the climatic, basin-scale and eddy regimes - Sergey G. Demyshev; Olga A. Dymova (Ocean Dynamics, 2022)

Stability analysis of finite amplitude interfacial waves in a two-layer fluid in the presence of depth uniform current - Tanmoy Pal; Asoke Kumar Dhar (Ocean Dynamics, 2022)

The impact of remote temperature anomalies on the strength and position of the Gulf Stream and on coastal sea level variability: a model sensitivity study - Tal Ezer; Sönke Dangendorf (Ocean Dynamics, 2022)

Time-dependent plume front positioning and its dynamics coupled with seasonal river efflux - G. Seena; K. R. Muraleedharan; C. Revichandran; S. Abdul Azeez; Sebin John; Ravikumar C. Nair (Ocean Dynamics, 2022)

Tidal simulation revisited - Wei Huang; Y. Joseph Zhang; Zhengui Wang; Fei Ye; Saeed Moghimi; Edward Myers; Haocheng Yu (Ocean Dynamics, 2022)

Smooth particle hydrodynamics modelling of liquid-sediment system and coastal wave breaker - Fei Chong Ng; Mohd Hafiz Zawawi; Aqil Azman; Aizat Abas; Norizham Abdul Razak; Nurhanani A. Aziz; Nazirul Mubin Zahari (Ocean Dynamics, 2022)

Evaluation of wave model performance in the South Atlantic Ocean: a study about physical parameterization and wind forcing calibration - Júlia Kaiser; Izabel C. M. Nogueira; Ricardo M. Campos; Carlos E. Parente; Renato P. Martins; Wellington C. Belo (Ocean Dynamics, 2022)

The simulation of sediment transport and erosion caused by free-surface flow based on two-phase SPH model with the improved Shields criterion - Xiaojing Ma; Bowen Zhang; Jie Chen; Xinchao Zhou; Wei Chen (Ocean Dynamics, 2022)

Evolution of sea-level trends along the Norwegian coast from 1960 to 2100 - Kristian Breili (Ocean Dynamics, 2022)
A first national analysis of the evolution of sea-level rates along the Norwegian coast for the period 1960–2100 has been accomplished by exploring tide-gauge records, relative sea-level projections, and detection techniques for acceleration. Firstly, sea-level rates for the two study periods 1960–2020 and 1991–2020 were estimated. Along the Norwegian coast, relative sea-level rates show significant spatial variation due to glacial isostatic adjustment. Moreover, the coastal average sea-level rate for the period 1991–2020 is significantly higher than for the period 1960–2020. Accelerations were then estimated for all combinations of start years and study periods longer than 30 years by including quadratic coefficients in regression models. It was found that the estimates strongly depend on the study period and do not provide confident estimates of climate change driven variation in the sea level along the Norwegian coast. Secondly, non-linear trends in relative sea level were reconstructed from Singular-Spectrum Analysis, which at several tide gauges revealed low rates in the 1970s, maximum rates around 1990, and declining rates thereafter. From the reconstructed trends, significant positive acceleration in the relative sea level was estimated for the period 1960–2020, while accelerations less than zero were detected for the period 1991–2020. However, the estimates for the recent period appear not robust due to the influence of decadal and multidecadal variation characterizing Norwegian tide-gauge records. Finally, by artificially extending the tide-gauge records by projections, the time when unprecedented high sea-level rates emerge was identified. With projections calculated for the intensive emission scenario RCP8.5, the climate signal of the relative sea level emerges at earliest in the late 2030s. The time of emergence is typically 5 to 10 years later if reanalysis of sea-level pressure and wind speed are used to reduce decadal variation in the tide-gauge records. This is because the meteorological regressors, as a side effect, introduce serial correlations that lead to rate estimates with enlarged standard errors. An important implication of the findings is that a possible absence of record high sea-level rates in the 2020s and 2030s does not falsify that relative sea level along the Norwegian coast is consistent with projections of RCP8.5.

Spectral wave characteristics in the coastal waters of the central west coast of India during tropical cyclone Kyarr - M. Anjali Nair; M. M. Amrutha; V. Sanil Kumar (Ocean Dynamics, 2022)

Spatiotemporal variability of the ocean since 1900: testing a new analysis approach using global sea level reconstruction - Tal Ezer; Sönke Dangendorf (Ocean Dynamics, 2022)

The role of the West Florida Shelf topography on the Loop Current system variability - Nektaria Ntaganou; Vassiliki Kourafalou; Matthieu Le Hénaff; Yannis Androulidakis (Ocean Dynamics, 2022)

Physical-Ecological Response of the California Current System to ENSO events in ROMS-NEMURO - Nathalí Cordero-Quirós; Arthur J. Miller; Yunchun Pan; Lawrence Balitaan; Enrique Curchitser; Raphael Dussin (Ocean Dynamics, 2022)

Modeling studies of the bioluminescence potential dynamics in a high Arctic fjord during polar night - Igor Shulman; Jonathan H. Cohen; Mark A. Moline; Stephanie Anderson; E. Joseph Metzger; Clark Rowley (Ocean Dynamics, 2022)
During polar nights in January 2012 and 2017, significantly higher bioluminescence (BL) potential emissions in the upper 50 m were observed in the fjord Rijpfjorden (Svalbard, Norway) in comparison to offshore stations (located on the shelf-break, shelf-slope areas and in the deeper water). The objective of this paper is to better understand why, during two polar nights (separated by 5 years), the values of BL potential in the northern Svalbard fjord are higher than at offshore stations, and what the role of advection is in observed elevated BL potential values in the top 50 m of the fjord. To address the above objective, we applied the same BL potential modeling approach and strategies during polar nights for both 2012 and 2017. For both years, advection of BL potential from offshore (including upwelling along the shelf, shelf-slope) produced an increase of BL potential in the fjord area, in spite of the introduction of mortality in bioluminescent organisms. Observations of BL potential indicated high emissions at depths below 100 m at offshore stations for both polar nights. Our modeling studies demonstrated that these high values of BL potential below 100 m are upwelled and advected to the top 50 m of the fjord. We demonstrated that upwelling and advection of these deep high BL potential values (and therefore, upwelling and advection of corresponding bioluminescent taxa) from offshore areas are dominant factors in observed BL potential dynamics in the top 50 m in the fjord.

The hydrodynamic theory of the Cyprus Eddy - Viktoriia M. Egorova; Valery N. Zyryanov; Mikhail A. Sokolovskiy (Ocean Dynamics, 2022)

Probabilistic assessment of rogue wave occurrence in directional wave fields - Cagil Kirezci; Alexander V. Babanin; Dmitry Chalikov (Ocean Dynamics, 2021)

Experiments on uni-directional and nonlinear wave group shoaling - Olivier Kimmoun; Hung-Chu Hsu; Norbert Hoffmann; Amin Chabchoub (Ocean Dynamics, 2021)

Vertical coupling and dynamical source for the intraseasonal variability in the deep Kuroshio Extension - Yang Yang; X. San Liang; Hideharu Sasaki (Ocean Dynamics, 2021)

Modulation of near-inertial motions on the Mississippi-Alabama Shelf - Maarten C. Buijsman; Jordan Earls; Helen Weierbach (Ocean Dynamics, 2021)

Redistribution of riverine and rainfall freshwater by the Bay of Bengal circulation - Akurathi Venkata Sai Chaitanya; Jérôme Vialard; Matthieu Lengaigne; Francesco d’Ovidio; Jean Riotte; Fabrice Papa; Rathinam Arthur James (Ocean Dynamics, 2021)

Dynamics of counter wind current along the south Sri Lanka coast during the Southwest Monsoon - C. H. Wickramage; Weiqiang Wang; K. Arulananthan; Ruchira Jayathilake (Ocean Dynamics, 2021)

Dynamics and transport from the boundary Northern Current toward the Toulon Bay: multi-platform observations and downscaling modelling approaches - Anne Molcard; Anthony Gramoullé; Camille Mazoyer; Natacha Bourg; Yann Ourmières (Ocean Dynamics, 2021)

Impact of climate variability of the Western Tropical Pacific on maximum salinity water in the South China Sea - Joachim W. Dippner; Sarah C. Weber; Ajit Subramaniam (Ocean Dynamics, 2021)
Salinity observations in the Vietnamese upwelling area in June 2016 indicated a significant increase in the salinity of the maximum salinity water (MSW). The source of MSW inflow into the South China Sea (SCS) is a mixture of the Western North Pacific Central Water and the North Pacific Equatorial Water. Although the East Asian winter monsoon is correlated with both the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), the mean salinity of MSW is only spuriously lag correlated to the PDO, but highly correlated to all tropical climate modes (except El Niño Modoki) with a time lag up to 7 months. Composite analyses indicate that the modulation of ENSO by a PDO in a positive phase results in optimal inflow conditions. A comparison of two post-El Niño years with different PDO polarity (negative in 2003 and positive in 2016) shows that the dominant driver is the variability in outgoing long-wave radiation (OLR) and in zonal wind in the tropics. In 2003, enhanced convective activity over the West Pacific warm pool resulted in a cyclonic circulation. In 2016, convective activity was weak and an anticyclonic circulation was intensified, which transported the saltier North Pacific Equatorial Water into the SCS. This observed increase in the salinity of MSW requires a modification of the previous definitions of characteristic water masses, which is presented here. The question of whether or not the increase in MSW salinity is a transient phenomenon cannot be answered. It might be possible that the increase in salinity is related to global warming.

Wave characteristics in a semi-enclosed offshore windfarm influenced by East Asian monsoon and extreme weather: a study of central Hangzhou Bay, China - Bin Yang; Yifan Yang; Zhongliang Yang; Xi Feng; Qing Ye; Liangliang Yu; Jian Ou (Ocean Dynamics, 2021)

A numerical study on the role of atmospheric forcing on mixed layer depth variability in the Bay of Bengal using a regional ocean model - Sumit Dandapat; Arun Chakraborty; Jayanarayanan Kuttippurath; Chirantan Bhagawati; Radharani Sen (Ocean Dynamics, 2021)

Effect of the wind acceleration magnitude during the first stages of the wind-wave generation process - Lucia Robles-Diaz; Francisco J. Ocampo-Torres; Hubert Branger; Hector Garcia-Nava; Pedro Osuna; Nicolas Rascle (Ocean Dynamics, 2021)

The 2nd international workshop on waves, storm surges and coastal hazards incorporating the 16th international workshop on wave hindcasting and forecasting - Val Swail; Jose-Henrique Alves; Jennifer Brown; Diana Greenslade; Robert Jensen (Ocean Dynamics, 2021)

Impact of Caribbean Anticyclones on Loop Current variability - Yannis Androulidakis; Vassiliki Kourafalou; Maria Josefina Olascoaga; Francisco Javier Beron-Vera; Matthieu Le Hénaff; Heesook Kang; Nektaria Ntaganou (Ocean Dynamics, 2021)

Rapid dissipation of a Loop Current eddy due to interaction with a severe Gulf of Mexico hurricane - Henry Potter; Chuan-Yuan Hsu; Steven F. DiMarco (Ocean Dynamics, 2021)

Spectral shapes and parameters from three different wave sensors - Anne Karin Magnusson; Robert Jensen; Val Swail (Ocean Dynamics, 2021)
The quality of wave measurements is of primary importance for the validation of wave forecasting models, satellite wave calibration and validation, wave physics, offshore operations and design and climate monitoring. Validation of global wave forecasts revealed significant regional differences, which were linked to the different wave buoy systems used by different countries. To fully understand the differences between the wave measurement systems, it is necessary to go beyond investigations of the integral wave parameters height, period and direction, into the frequency spectra and the four directional Fourier parameters that are used to estimate the directional distribution. We here analyse wave data measured from three different sensors (non-directional Datawell Waverider buoy, WaveRadar Rex, Optech laser) operating at the Ekofisk oil production platform located in the central North Sea over a period of several months, with significant wave height ranging from 1 to 10 m. In general, all three sensors provide similar measurements of the integral wave properties and frequency spectra, although there are some significant differences which could impact design and operations, forecast verification and climate monitoring. For example, the radar underestimates energy in frequency bands higher than 8 s by 3–5%, swell (12.5–16 s) by 5–13%, while the laser has 1–2% more energy than the Waverider in the most energetic bands. Lee effects of structures are also estimated. Lower energy at the frequency tail with the radar has an effect on wave periods (they are higher); wave steepness is seen to be reduced by 10% in the wind seas. Goda peakedness and the unidirectional Benjamin-Feir index are also examined for the three sensors.

Sound speed variation in the coastal waters off Cochin and signature of subsurface maxima - Abdul Azeez S; Revichandran C; Muraleedharan K. R; Sebin John; Seena G; Ravikumar C. Nair; Manju K. G (Ocean Dynamics, 2021)

Spectral peak wave period climatology and its relationship with natural climate variability over the Bay of Bengal - Jesbin George; V. Sanil Kumar (Ocean Dynamics, 2021)

Northern boundary current variability and mesoscale dynamics: a long-term HF RADAR monitoring in the North-Western Mediterranean Sea - Natacha Bourg; Anne Molcard (Ocean Dynamics, 2021)

Comprehensive wave climate analysis of the Uruguayan coast - Rodrigo Alonso; Sebastián Solari (Ocean Dynamics, 2021)

Mapping of tidal current and associated nonlinear currents in the Xiangshan Bay by coastal acoustic tomography - Minmo Chen; Ze-Nan Zhu; Chuanzheng Zhang; Xiao-Hua Zhu; Zhensheng Zhang; Min Wang; Hua Zheng; Xinyu Zhang; Juntian Chen; Zongcai He; Longhao Dai; Arata Kaneko (Ocean Dynamics, 2021)

A first estimation of tsunami hazard of the Pacific coast of Costa Rica from local and distant seismogenic sources - Silvia Chacon-Barrantes; Isabel Arozarena-Llopis (Ocean Dynamics, 2021)

Numerical simulation of waves in the Caspian Sea: calibration and verification of the observation-based source terms - Atefeh Alipour; Seyed Mostafa Siadatmousavi; Felix Jose (Ocean Dynamics, 2021)

Coastal Ocean Forecasting Science supported by GODAE OceanView Coastal Oceans and Shelf Seas Task Team (COSS-TT)—Part II - Mauro Cirano; Guillaume Charria; Pierre De Mey-Frémaux; Vassiliki H. Kourafalou; Emil Stanev (Ocean Dynamics, 2021)

Quantifying wave measurement differences in historical and present wave buoy systems - Robert Edward Jensen; Val Swail; Richard Harry Bouchard (Ocean Dynamics, 2021)
An intra-measurement evaluation was undertaken, deploying a NOMAD buoy equipped with three National Data Buoy Center and two Environment and Climate Change Canada-AXYS sensor/payload packages off Monterey, California; a Datawell Directional Waverider buoy was deployed within 19 km of the NOMAD site. The six independent wave measurement systems reported hourly estimates of the frequency spectra, and when applicable, the four Fourier directional components. The integral wave parameters showed general agreement among the five sensors compared to the neighboring Datawell Directional Waverider, with the Inclinometer and the Watchman performing similarly to the more sophisticated 3DMG, HIPPY, and Triaxys sensor packages. As the H m0 increased, all but the Inclinometer were biased low; however, even the Watchman reported reasonable wave measurements up to about 6–7 m, after which the H m0 becomes negatively biased up to about a meter, comparable to previous studies. The parabolic fit peak spectral wave period, T pp , results showed a large scatter, resulting from the complex nature of multiple swell wave systems compounded by local wind-sea development, exacerbated by a variable that can be considered as temporally unstable. The three directional sensors demonstrated that NOMAD buoys are capable of measuring directional wave properties along the western US coast, with biases of about 6 to 9 deg, and rms errors of approximately 30 deg. Frequency spectral evaluations found similarities in the shape, but a significant under estimation in the high frequency range. The results from slope analyses also revealed a positive bias in the rear face of the spectra, and a lack of invariance in frequency as suggested by theory.

Ocean and atmosphere changes in the Caribbean Sea during the twenty-first century using CMIP5 models - David Francisco Bustos Usta; Rafael Ricardo Torres Parra (Ocean Dynamics, 2021)

Correction to: Characteristics of topographic submesoscale eddies off the Crimea coast from high-resolution satellite optical measurements - Anna Aleskerova; Arseny Kubryakov; Sergey Stanichny; Alessia Medvedeva; Evgeniy Plotnikov; Artem Mizyuk; Liudmila Verzhevskaia (Ocean Dynamics, 2021)

“Grey swan” storm surges pose a greater coastal flood hazard than climate change - Kevin Horsburgh; Ivan D. Haigh; Jane Williams; Michela De Dominicis; Judith Wolf; Addina Inayatillah; David Byrne (Ocean Dynamics, 2021)
In this paper, we show that over the next few decades, the natural variability of mid-latitude storm systems is likely to be a more important driver of coastal extreme sea levels than either mean sea level rise or climatically induced changes to storminess. Due to their episodic nature, the variability of local sea level response, and our short observational record, understanding the natural variability of storm surges is at least as important as understanding projected long-term mean sea level changes due to global warming. Using the December 2013 North Atlantic Storm Xaver as a baseline, we used a meteorological forecast modification tool to create “grey swan” events, whilst maintaining key physical properties of the storm system. Here we define “grey swan” to mean an event which is expected on the grounds of natural variability but is not within the observational record. For each of these synthesised storm events, we simulated storm tides and waves in the North Sea using hydrodynamic models that are routinely used in operational forecasting systems. The grey swan storms produced storm surges that were consistently higher than those experienced during the December 2013 event at all analysed tide gauge locations along the UK east coast. The additional storm surge elevations obtained in our simulations are comparable to high-end projected mean sea level rises for the year 2100 for the European coastline. Our results indicate strongly that mid-latitude storms, capable of generating more extreme storm surges and waves than ever observed, are likely due to natural variability. We confirmed previous observations that more extreme storm surges in semi-enclosed basins can be caused by slowing down the speed of movement of the storm, and we provide a novel explanation in terms of slower storm propagation allowing the dynamical response to approach equilibrium. We did not find any significant changes to maximum wave heights at the coast, with changes largely confined to deeper water. Many other regions of the world experience storm surges driven by mid-latitude weather systems. Our approach could therefore be adopted more widely to identify physically plausible, low probability, potentially catastrophic coastal flood events and to assist with major incident planning.

Investigating mesoscale eddy characteristics in the Luzon Strait region using altimetry - Corinne B. Trott; E. Joseph Metzger; Zhitao Yu (Ocean Dynamics, 2021)

Characteristics of topographic submesoscale eddies off the Crimea coast from high-resolution satellite optical measurements - Anna Aleskerova; Arseny Kubryakov; Sergey Stanichny; Alessia Medvedeva; Evgeniy Plotnikov; Artem Mizyuk; Liudmila Verzhevskaia (Ocean Dynamics, 2021)

Improving Baltic Sea wave forecasts using modelled surface currents - Hedi Kanarik; Laura Tuomi; Jan-Victor Björkqvist; Tuomas Kärnä (Ocean Dynamics, 2021)
Currents in the Baltic Sea are generally weak, but during strong winds they can grow high enough to affect the surface wave propagation and evolution. To evaluate the significance of wave-current interactions in the Baltic Sea, we conducted a study using the wave model WAM, comparing a run without surface currents to one with current forcing from a NEMO hydrodynamical model simulation. The overall changes to the wave field caused by currents were quite small. Changes of over 10 cm in significant wave height (SWH) or 1 s in the peak period ( T p ) occurred only in some areas and typically less than 3% of the time. Current refraction changed the SWH annual mean by up to 2 cm, but changes up to 60 cm were seen in the maximum values. T p had occasionally large changes due to shifts in the peak energy in two-peaked swell and wind-sea spectra. Including currents typically led to a stronger changes in swell energy compared to the changes in wind sea energy. A comparison with a wave buoy in the Gulf of Finland showed that this change in the swell energy improved the accuracy of the simulation in this narrow gulf. Current-induced refraction was most prominent near the coastal areas, where current speed occasionally exceeded 0.3 m/s. In general, SWH decreased in the coastal areas with strong currents and slightly increased in adjacent open sea areas. The current effects were most frequent in the Gulf of Finland, the Western Gotland Basin and the Åland Sea.

Hydrodynamic aspects of tsunami wave motion: a review - Arghya Bandyopadhyay; Shibam Manna; Dipannita Maji (Ocean Dynamics, 2021)

Eddy formation in the bays of Kamchatka and fluxes to the open ocean - Alexandre L’Her; Markus Reinert; Sergey Prants; Xavier Carton; Mathieu Morvan (Ocean Dynamics, 2021)

Correction to: Initial time dependence of wind- and density-driven Lagrangian residual velocity in a tide-dominated bay - Guangliang Liu; Zhe Liu; Huiwang Gao; Shizuo Feng (Ocean Dynamics, 2021)

Correction to: Wind events in a subtropical coastal upwelling region as detected by admittance analysis - Heriberto J. Vazquez; Jose Gomez-Valdes (Ocean Dynamics, 2021)

Identification of wave systems in the multimodal sea state along the Indian shelf seas - M. M. Amrutha; V. Sanil Kumar (Ocean Dynamics, 2021)

Hindcasting of tropical cyclone winds and waves - Stefan Zieger; Diana J. M. Greenslade; Saima Aijaz; Jeffrey D. Kepert; Andrew Burton (Ocean Dynamics, 2021)