Wave breaking in the ocean affects the height of extreme waves, energy dissipation, and interaction between the atmosphere and upper ocean. Numerical modelling is a critical step in understanding the physics of wave breaking and offers insight that is hard to gain from field data or experiments. High-fidelity numerical modelling of three-dimensional breaking waves is extremely challenging. Conventional

Various strategies are proposed for enforcing stress-free boundary conditions on deformed domains using a weak-form-based discretization in a Cartesian frame of reference. Due to the irregularity of the computational domain and the particular type of boundary condition, a coupling between the Cartesian velocity components is introduced. As such, a different computational kernel is required for the

This study provides an interpretation of isopycnal eddy transport for mass and passive tracers in double-gyre eddy-resolving oceanic circulation. This paper focuses on a transport/diffusion tensor representation of the eddy tracer flux, and a companion paper will focus on advective eddy-induced tracer and mass transports. We use a spatial filter to separate the large and small scales, which leads to

The efficacy of an ocean observing, analysis, and forecasting system for the Mid-Atlantic Bight and the Gulf of Maine is explored using the concept of array modes. The analysis-forecast system is based on a triply nested configuration of the Regional Ocean Modeling System (ROMS) in conjunction with 4-dimensional variational (4D-Var) data assimilation. The array modes identify the degrees of freedom

Storm surge and coastal flooding predictions can require high resolution of critical flow pathways and barriers, typically with simulations using grids/meshes with millions of cells/elements to represent a coastal region. However, the cost of this resolution can slow forecasts during a storm. To add resolution when and where it is needed, previous studies have used adaptive mesh methods, which update

The implicit equal-weights variational particle smoother (IEWVPS) is a combination of the particle filter (PF) and weak-constraint 4-dimensional variational (4D-Var) method, that inherits the merits of both. The IEWVPS avoids the filter degeneracy of particle filters through an implicit equal-weights scheme and reduces the root mean square deviations (RMSDs) by introducing the 4D-Var method. This method

Waves in large lakes put coastal communities and vessels under threat, and accurate wave predictions are needed for early warnings. While physics-based numerical wave models such as WAVEWATCH III (WW3) are useful to provide spatial information to supplement in situ observations, they require intensive computational resources. An attractive alternative is machine learning (ML) methods, which can potentially

Wave bottom reflection induced by a changing bathymetry has a major impact on the near-shore environment, where harbors and other infrastructure are based. However, this reflection is only partially accounted for in large scale numerical wave prediction models. The present work implements the analytical bottom reflection source term derived in Yevnin and Toledo (2018) to WAVEWATCH III, a numerical

The deep eastern boundary current (DEBC) in the southeast Atlantic Ocean plays an important role in the global meridional overturning circulation, by carrying a comparable fraction of the North Atlantic Deep Water transport toward the Southern Ocean to that of the deep western boundary current. At the same time, the southeast Atlantic Ocean is constantly influenced by energetic Agulhas rings that are

This paper analyses a methodology to identify sub-series of waves parameters and wind speed able to explain the overall variability of the input dataset. To this end, the K-means clustering technique is applied to a 40-year long time series of hindcast data off the Genoa coastline (NW Italy). K-means aims to group the data in a reduced number of clusters, represented by as many modes of variability

Flash rips and surf eddies are transient horizontal structures of the order of 10 to 100 m, which can be generated in the surfzone in the absence of bathymetric irregularities. They are traditionally evaluated in a depth averaged setting which involves intrinsic horizontal shear instabilities and the direct generation of vorticity by short-crested waves. In this article, we revisit the processes of

In recent years, high-resolution global ocean circulation models have begun to include astronomical tidal forcing to concurrently simulate ocean circulation, barotropic and internal tides. The inclusion of tides is of great significance for understanding three-dimensional (3-D) ocean mixing and developing internal tide prediction. However, due to uncertainty in topography and damping terms, improper

Internal tides generated from multiple sites create complicated interference patterns, often making it difficult to identify the origin, direction of propagation, and dissipation of individual waves. To identify these constituent waves, we apply a directional Fourier filter (DFF) method to analyse multimodal, broad-wavenumber, internal wave fields found over varying topography. We apply the method

The D’Urville Sea, East Antarctica, is a major source of Dense Shelf Water (DSW), a precursor of Antarctic Bottom Water (AABW). AABW is a key water mass involved in the worldwide ocean circulation and long-term climate variability. The properties of AABW in global climate models suffer from several biases, making climate projections uncertain. These models are potentially omitting or misrepresenting

Remotely sensed optical data are fundamental to be integrated into biogeochemical models, since the key role of the optical properties on lower trophic dynamics. In this paper, it is shown how ocean optics satellite products are used to constrain the optical algorithm adopted in the operational biogeochemical model system MedBFM that produces analyses, forecasts and reanalyses for the Mediterranean

The influence of ocean surface currents on the global wind-wave field is revisited. State-of-the-art numerical spectral wave model simulations with and without surface currents taken from an eddy resolving global ocean reanalysis were compared. As a global average, simulations forced with currents display significantly better agreement with altimeter derived wave heights. The bias and root mean square

The Red Sea Project (RSP) is based on a coastal lagoon with over 90 pristine islands. The project intends to transform the Red Sea coast into a world-class tourist destination. To better understand the regional dynamics and water exchange scenarios in the lagoon, a high-resolution numerical model is implemented. The general and tidal circulation dynamics are then investigated with a particular focus

It is typical for low-resolution simulations of the ocean to miss not only small- but also large-scale patterns of the flow dynamics compared with their high-resolution analogues. It is usually attributed to the inability of coarse-grid models to properly reproduce the effects of the unresolved small-scale dynamics on the resolved large scales. In part, the reason for that is that coarse-grid models

Two- and three-dimensional models are proposed for ocean-wave attenuation due to scattering by ice floes in the marginal ice zone, in which the attenuation rate depends on the horizontal size of the individual floes. The scattering models are shown to reproduce the behaviour of wave attenuation over short wave periods. However, it is shown that scattering alone cannot explain the observed asymptotic

In order to estimate the spatially varying bottom friction coefficients (BFCs) in the Bohai, Yellow and East China Seas (BYECS), multi-mission satellite observations from TOPEX/Poseidon, Jason-1 and Jason-2 are assimilated into a two-dimensional tidal model with an adjoint method. This work aims to: (1) study the characteristics of spatially varying BFCs in BYECS; and (2) find out the possible sources

This paper examines factors contributing to the remarkable longevity of coherent vortices in the subtropical westward flows. Baroclinic vortices embedded in large-scale vertical shears generate Rossby waves which form an opposite sign eddy associated with inertial Taylor columns on the beta-plane. The combination of the vortex and lee Rossby wave can be viewed as a hetonic dipole that induces meridional

Oscillating turbulent bottom boundary layers (BBLs) occur in lakes and coastal oceans. At the mesoscale level, their kinematics are usually characterized by assuming either laminar or steady turbulent flow, and applying analytical solutions or semi-empirical correlations; e.g. log-law, Stokes’ second problem, inertial dissipation method (IDM), Batchelor fitting to temperature microstructure method

In this article, Part 1 of a two-part series, we run and evaluate the skill of a regional physical–biogeochemical stochastic ocean model based on NEMO. The domain covers the Bay of Biscay at 1/36° resolution, as a case study for open-ocean and coastal shelf dynamics. We generate model ensembles based on assumptions about errors in the atmospheric forcing, the ocean model parameterizations and in the

We describe a numerical treatment for a two-layer coupled model developed for the investigation of submarine landslides and resulting tsunami generation over irregular bathymetry. The landslide model is formulated in a Cartesian coordinate system oriented with the still water level in order to facilitate coupling between water and ground motions. Motions in the upper water layer are simulated using

Monitoring and predicting global ocean biogeochemistry and marine ecosystems is one of the biggest challenges for the coming decade. In operational systems, biogeochemical (BGC) models are forced – or coupled – with physical ocean models fields that are generally constrained by data assimilation of temperature, salinity and sea level anomalies. Yet, while physical data assimilation substantially improves

In this Part 2 article of a two-part series, observations based on satellite missions were used to evaluate the empirical consistency of model ensembles generated via stochastic modelling of ocean physics and biogeochemistry. A high-resolution Bay of Biscay configuration was used as a case study to explore the model error subspace in both the open and coastal ocean. In Part 1 of this work, three experiments

Two methods for setting tides in regional numerical models focussed on replication of internal waves are discussed in this paper. A traditional procedure prescribes the tidal forcing at the boundaries of the model domain. As it follows from our analysis, this method works well in some cases but does not allow to control identical generation conditions in all points of the model grid. Tidal ellipses

Numerical storm surge models are essential to forecasting coastal flood hazard and informing the design of coastal defences. However, such models rely on a variety of inputs, many of which carry uncertainty. An awareness and understanding of the sensitivity of model outputs with respect to those uncertain inputs is therefore essential when interpreting model results. Here, we use an unstructured-mesh

We address ocean modeling capability that has grown exponentially while ocean observation growth has not maintained pace, a situation leading to seemingly degraded forecast skill when model resolution is increased. Skill in predicting ocean instabilities such as mesoscale eddies requires satellite and in situ observations continually correcting numerical model conditions. Observations constrain positions

It has been known for some time that the ocean basins are populated by what is known as “zonal jets”, “deep zonal jets”, or “striations”. Since the oceanic flow is, at least weakly, chaotic, it is not known whether the positions of the jets are “deterministic”, that is, entirely determined by external parameters. A number of theories have been proposed to explain them, some of them predicting zonal

We describe a new 4-D variational assimilation system, called CYCLOCIM, to estimate the climatological seasonal cycle of the residual mean ocean circulation. CYCLOCIM assimilates monthly mean potential temperature and salinity data from the World Ocean Atlas, and CFC-11, CFC-12 and natural radiocarbon measurements for the deep ocean from the Global Data Analysis Project, Version 2. CYCLOCIM’s control

Basin-scale wind curl anomalies in the North Pacific associated with El Niño increase westward Kuroshio transport in the Luzon Strait, whereas those associated with La Niña reduce it. However, the Kuroshio current in the Luzon Strait is further affected by mesoscale eddies and local wind stress. Numerical experiments are conducted to demonstrate that the anomalous low-level circulation over the Philippine

With increased computing power, the horizontal grid-spacing of regional ocean models is decreasing to the point where they can directly simulate lee waves. Although oceanic lee waves can be inherently nonhydrostatic, such as in the abyssal ocean or in the Gulf Stream, regional ocean models are frequently run in hydrostatic mode to avoid the computational expense of solving the nonhydrostatic pressure

Abstract Understanding the trajectory of oil droplets in crossflow jets is important to estimate the pathways of hydrocarbons and to plan countermeasures. We report experimental results of an oil jet with release velocity around 1.5 m/s in a crossflow of 0.3 m/s. The hydrodynamics of the jets obtained with the Large Eddy Simulation (LES) were used to predict the migration of the oil droplets. Two Lagrangian

Abstract Coastal hazard is rarely driven by only one source, as exemplified by the compound flooding from Hurricane Harvey in Galveston Bay in 2017. A 3D creek-to-ocean model is developed to explicitly resolve, without grid nesting, the marine (combination of atmospheric forcing and tides), fluvial and pluvial extremes for this extreme event. We first thoroughly assess the model skills using all available

Abstract Resonant triad interaction is an important mechanism via which the energy of internal tides (ITs) is dissipated. In this study, based on a two-dimensional high-resolution non-hydrostatic model, resonant triad interaction over mid-ocean ridges and corresponding energetics are investigated. Impacts of topographic criticality (the ratio of topographic slope to internal wave slope) on resonant

Abstract Short waves are of key importance for nearshore dynamics, particularly under storms, where they contribute to extreme water levels and drive large morphological changes. Therefore, it is crucial to model accurately the propagation and dissipation of storm waves in the nearshore area. In this paper, field observations collected in contrasted environments and conditions are combined with predictions

Abstract In this work, sea ice concentrations in the regions of Baffin Bay, Hudson Bay, the Labrador Sea and the Gulf of St. Lawrence were estimated using a standalone regional configuration of Los Alamos Sea ice Model, CICE. A sensitivity analysis of the mixed layer depth criteria that affects the predicted sea ice formation/ablation has been carried out to tune the model. Sea ice concentration from

In-situ ocean wave observations are critical to improve model skill and validate remote sensing wave measurements. Historically, such observations are extremely sparse due to the large costs and complexity of traditional wave buoys and sensors. In this work, we present a recently deployed network of free-drifting satellite-connected surface weather buoys that provide long-dwell coverage of surface

Phytoplankton biomass, indicated by chlorophyll-a (Chl-a) concentration, is fundamentally important for aquatic ecosystems. However, accurately simulating Chl-a is always challenging even when using state-of-the-art numerical models. We propose a data-driven modeling framework that combines Empirical Orthogonal Function (EOF) analysis and machine-learning technique to tackle this problem, using Chesapeake

We describe a two-layer, coupled model for landslide motion over irregular bathymetry and resulting water column motion and tsunami generation. The three-dimensional non-hydrostatic wave model NHWAVE (Ma et al., 2012) is applied as the upper-layer model to simulate landslide-generated tsunami waves. Here, we focus on the derivation of governing equations for the lower-layer model, where the landslide

The formation and maintenance of low oxygen offshore of the Changjiang River Estuary have occurred with high frequency in certain regions, which are defined as bottom hypoxia hotspots. The two major hotspots are the southern shallow bank (Yangtze Bank) and the submarine canyon. For this study, a high resolution ecosystem model was used to simulate dissolved oxygen dynamics over the continental shelf

The Chilean Inland Sea (CIS) is an extensive estuary system with a complex topography and many fjords and channels. The degrees of stratification and mixing in the CIS are strongly affected by river discharges, high levels of rainfall, wind, and tidal forces. Field and satellite observations have suggested that stratification and mixing fluctuate on different timescales and spatial scales, but the

Abstract A σ -coordinate non-hydrostatic coastal ocean model is developed using the discontinuous Galerkin finite element method. With the selection of the low-order piecewise-constant P 0 DG and piecewise-linear P 1 DG discretisations in the vertical for the velocity and pressure fields, respectively, the proposed σ -coordinate model can naturally retain the wave dispersion characteristics of the

Abstract The Regional Ocean Modeling System (ROMS) 4-dimensional variational (4D-Var) data assimilation system was used to compute ocean state estimates of the Mid-Atlantic Bight (MAB). A three-level nested grid configuration was employed with horizontal resolution successively enhanced from 7 km down to 800 m at the innermost nest. This captures the dynamics on space- and time-scales ranging from

Abstract The properties of the expected analysis and forecast error covariance matrices are explored using a novel method based on the tangent linearization and adjoint of a 4-dimensional variational (4D-Var) data assimilation system. The method is applied to the mesoscale circulation that develops in the presence of a baroclinically unstable mid-latitude ocean temperature front using a series of paternal

Abstract This paper investigates the performance of three different wave model source term packages in narrow fetch geometries. The packages are used to model the sea state in a complex coastal system with narrow fjords on the west coast of Norway. The modelling system is based on the Simulating WAves Nearshore (SWAN) wave model that is forced with winds from a nested atmospheric model and wave spectra

Abstract Shallow water equations (SWEs) are discretised on a regional spherical multiple-cell (SMC) grid. The SMC grid uses unstructured techniques with rectangular cells and supports multi-resolutions like mesh refinement. The numerical schemes on the 2-D SMC grid are combinations of the conventional finite-difference ones and flux-form finite-volume formulations in 1-D loops. Semi-implicit schemes

Abstract Motivated by observations of fine scale vertical shear and its contribution to mixing in the tropical ocean, this study explores the impact of vertical resolution in an ocean model on sea surface temperature in the tropical Pacific Ocean. We conduct two model experiments that differ in the vertical discretization only, with the grid spacing in one being significantly smaller than the other

Abstract A nested configuration of the Regional Ocean Modeling System (ROMS) comprising three grids was used in conjunction with a 4-dimensional variational (4D-Var) data assimilation system to compute ocean state estimates of the Mid-Atlantic Bight (MAB). The three nested grids have a horizontal resolution ranging from ∼ 7 km to ∼ 0.8 km and capture circulation regimes that span the Gulf Stream western

Abstract The structure of circular baroclinic vortices in rotating stratified fluids is examined in order to rationalize the observed amplification of fluid rotation inside long-lived geophysical vortices during their evolution. New relations between basic vortex parameters at horizontal mid-depth are derived in order to compare vortices with the same potential vorticity extremum at the vortex center

Abstract In contrast with the severe thinning of ice shelves along the coast of West Antarctica, large ice shelves (specifically, the Filchner–Ronne and Amery Ice Shelves) with deep grounding lines gained mass during the period 1994–2012. This positive mass budget is potentially associated with the marine ice production, which originates from the supercooled Ice Shelf Water plume carrying suspended

Abstract This study investigates the contribution of short-wave breaking to storm surges through a high-resolution hindcast of the sea state and storm surge associated with the extra-tropical storm Klaus. This storm made landfall in January 2009 in the Southern Bay of Biscay and produced the largest storm surges observed in this region over the last 20 years, with 1.70 m in the Arcachon Lagoon and

Abstract While lateral boundary conditions are crucial for the physical modelling of ocean dynamics, their estimation may lack accuracy in coastal regions. Data-assimilation has long been used to improve accuracy, but most of the widely-used methods are difficult to implement. We tried a new and an easy-to-implement method to estimate boundary conditions. This method uses data assimilation with a stochastic

Abstract Predicting ocean transport has many practical applications ranging from search and rescue operations to predicting the spread of oil, debris, and biogeochemical tracers, yet trajectory prediction remains a challenge for existing ocean modeling techniques. General circulation models require high resolution observational data in order to be properly initialized, but these data do not exist for

Abstract The sea ice component of a regional high-resolution ocean model is improved, with particular attention to accurate representation of the salinity budget for the coupled system. The impact of this improvement is shown first using a one-dimensional test and then the realistic model simulation of the Eastern Bering Sea for the relatively high sea ice extent winter of 2009–10. Improvements to

Abstract This paper presents numerical simulations of a bichromatic wave group propagating and breaking over a fixed breaker bar. The simulations are performed using a newly stabilized Reynolds-averaged Navier–Stokes (RANS) two-equation turbulence closure, which solves the longstanding problem of over-production of turbulence beneath surface waves in the nearly potential flow region prior to breaking

Abstract Hot spots of sea level variability along the North American East Coast have been shown to shift in latitude repeatedly over the past 95 years and connections with a number of forcing phenomena, including the North Atlantic Oscillation (NAO) and Atlantic Meridional Overturning Circulation (AMOC), have been suggested. Using a barotropic 1/12° NEMO model of the North American East Coast (to represent