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 in the upper

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 are used

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 boundary

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 the ocean

While lateral boundary conditions are crucial for the physical modeling 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

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 frazil ice

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 the model

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. The fluid

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 1.10 m in

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. This

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

Wetting and drying processes in shallow water systems by surges, tides and seiches have important societal, physical and biological impacts. Operational 3D regional models are of sufficient resolution, O(1 km), that the processes of wetting and drying need to be included. Here we describe a flux limiter based approach that allows a numerical ocean model with a flux formulation of tracer advection to

From satellite altimetry, it is known the benefit of assimilating sea level anomalies (SLA) has been shown in the context of operational ocean forecast systems. However, how much data assimilation (DA) of altimetry data improves the representation of mesoscale eddies has still not been investigated in previous studies. Especially in the South China Sea (SCS), no estimation for that has been done in

We investigate the impact of wave-dependent stress on surge modelling, from case studies in the North Sea, using a global ocean model forced with a wave-atmosphere coupled model. We select the storms with the largest surges and a range of sea state development from young to mature seas. The modelled surges are compared to tide gauges and altimeter data. The ocean model is able to accurately predict

Coastal hazards often result from the combination of different simultaneous oceanographic processes that occur at multiple spatial and temporal scales. To predict coastal flooding and erosion, it is necessary to accurately represent hydrodynamic conditions. For this reason, here we present a stochastic, climate based wave emulator that provides the hydrodynamic conditions needed for these predictions

Thermodynamic ablation of ice in contact with the ocean is an essential element of ice sheet and ocean interactions but is challenging to model and quantify. Building on earlier observations of sea ice ablation, a variety of recent theoretical, experimental and observational studies have considered ice ablation in contrasting geometries, from vertical to near-horizontal ice faces, and reveal different

The isopycnal tracer diffusion scheme is commonly used in a coarse-resolution global ocean model to parameterize the diffusive effect of mesoscale eddy stirring. This scheme implemented in a depth-coordinate model often accompanies a fail-safe system to prevent numerical instability caused by large isopycnal diffusion around steeply sloped isopycnal surfaces. Its practical implementation artificially

The ensemble four-dimensional variational (En4DVar) data assimilation (DA) system introduced in Part I (Pasmans and Kurapov, 2019) is tested in the coastal waters offshore Oregon and Washington, U.S. West coast, during the spring and summer of 2011. The background error covariance B is derived from the forecast ensemble. Satellite sea-surface temperature (SST), sea-surface height (SSH), and daily-averaged

For the first time we introduce an error estimator for the numerical approximation of the equations describing the dynamics of sea ice. The idea of the estimator is to identify different error contributions coming from spatial and temporal discretization as well as from the splitting in time of the ice momentum equations from further parts of the coupled system. The novelty of the error estimator lies

We use an Observing System Simulation Experiment (OSSE) to quantify improvements in ocean state estimation due to the assimilation of simulated Surface Water Ocean Topography (SWOT) observations using a multi-scale 3DVAR approach. The sequential multi-scale assimilation first generates a large-scale analysis and then updates that analysis with smaller scale corrections. Since we use temperature and

In this paper, the hydrodynamics of the Southern Bight of the North Sea (SBNS) and in particular, the Belgian Coastal Zone (BCZ) is investigated on daily to seasonal time scales using a high resolution hydrodynamical model. The Regional Ocean Modeling System (ROMS) is implemented over the SBNS with 5 km resolution and downscaled at 1 km resolution over the BCZ in a two-way nesting configuration run

Whitehead’s ‘tank model’ (Whitehead, 2000) describes a localized deep convective site exchanging water with a two-layer neighbouring ocean basin at three vertical levels. We generalize the original model for the case of arbitrary temperatures and salinities of water layers under an assumption of a constant surface heat flux to the atmosphere in the convective area. The generalized model has unique

Interaction processes of attenuating surface waves and underlying currents are explicitly simulated with a nonhydrostatic free surface numerical model. The model, designed with special attention to the numerical conservation properties of energy and momentum, is capable of accurately capturing the effect of the virtual wave stress, a viscous momentum transfer from waves to current. Simple experiments

A parameterisation scheme for restratification of the mixed layer by submesoscale mixed layer eddies is implemented in the NEMO ocean model. Its impact on the mixed layer depth (MLD) is examined in 30-year integrations of “uncoupled” ocean–ice (GO5) and “coupled” atmosphere–ocean–ice–land (GC2) 1/4° global climate configurations used by the Met Office Hadley Centre. The impact of the scheme on the

A set of realistic coastal coupled ocean-wave numerical simulations is used to study the impact of surface gravity waves on a tidal temperature front and surface currents. The processes at play are elucidated through analyses of the budgets of the horizontal momentum, the temperature, and the turbulence closure equations. The numerical system consists of a 3D coastal hydrodynamic circulation model

Self-similarity power-laws of wind-wave growth describe idealized cases of fetch-limited and duration-limited conditions. In this paper, a generalized view on wave growth in these two cases is discussed. A parametric model describing uniformly fetch- and duration-limited development of wind waves is suggested. The key assumption of the model is the universality of the self-similar shape of wave spectra

Large tsunamis can be generated by submarine slides, but these events are rare on human timescales and challenging to observe. Experiments and numerical modelling offer methods to understand the mechanisms by which they generate waves and what the potential hazard might be. However, to fully capture the complex waveform generated by a submarine slide, the slide dynamics must also be accurately modelled

Motivated by recent observations of coherent dipolar cyclone–anticyclone structures in the ocean, the modons, and their signature in the surface temperature field, we demonstrate that the classical modon solutions of the barotropic quasi-geostrophic equations can be generalized to include buoyancy or temperature as an active tracer. The properties of such “thermal” modons, and especially their ability

Understanding the governing mechanisms of atmosphere–wave–ocean​ interactions is critical for unravelling the formation and evolution mechanisms of severe weather phenomena. This study aims at investigating the effects of atmosphere–wave–ocean​ feedbacks on a Mediterranean tropical-like cyclone (medicane), occurred on 27–30 September 2018 at the central-eastern Mediterranean Sea and characterized by

In contrast to two-dimensional oceanic internal waves which have been extensively investigated, there are relatively few theoretical studies on three-dimensional internal waves. The most remarkable theory describing three-dimensional internal waves is the Kadomtsev–Petviashvili (KP) equation. Nevertheless, two shortcomings – unidirectional propagation and anisotropy – limit its application in some

This study makes progress towards a data-driven parameterization for mesoscale oceanic eddies. To demonstrate the concept and reveal accompanying caveats, we aimed at replacing a computationally expensive, standard high-resolution ocean model with its inexpensive low-resolution analogue augmented by the parameterization. We considered eddy-resolving and non-eddy-resolving double-gyre ocean circulation

We present a numerical study of current effects on waves (CEW) at submesoscales (100’s of m–10’s of km) with a realistic model configuration in Southern California. CEW is analyzed by comparing solutions forced by winds with and without current forcing through relative differences. The modulation of wave field due to currents is larger for the wave-breaking variables (i.e., whitecap coverage, air-entrainment

Downscaling broadscale ocean model information to resolve the fine-scale swash-zone dynamics has a number of applications, such as improved resolution of coastal flood hazard drivers, modeling of sediment transport and seabed morphological evolution. A new method is presented, which enables wave-averaged models for the nearshore circulation to include short-wave induced swash zone dynamics that evolve

Based on an eddy-resolving Regional Ocean Modeling System (ROMS) and the conditional nonlinear optimal perturbation (CNOP) method, we set up a nonlinear optimization system to investigate the effects of the fastest-growing initial errors on the prediction of the Kuroshio Extension (KE) transition process from the stable to the unstable state. The results reveal that the larger values of the CNOP-type

The effects of horizontal resolution and wave drag damping on the semidiurnal M2 tidal energetics are studied for two realistically-forced global HYbrid Coordinate Ocean Model (HYCOM) simulations with 41 layers and horizontal resolutions of 8 km (1∕12.5∘; H12) and 4 km (1∕25∘; H25). In both simulations, the surface tidal error is minimized by tuning the strength of the linear wave drag, which is a

Studies have suggested that the ocean dynamics in the South China Sea (SCS) play a crucial role in local air–sea processes and the regional weather or climate system. We used a high-resolution regional coupled model to investigate the impact of the El Niño Southern Oscillation (ENSO) on the atmospheric and oceanic processes in the SCS during ENSO decaying winter–spring. The coupled model demonstrates

Autonomous underwater vehicles (AUVs) operate in the three-dimensional and time-dependent marine environment with strong and dynamic currents. Our goal is to predict the time history of the optimal three-dimensional headings of these vehicles such that they reach the given destination location in the least amount of time, starting from a known initial position. We employ the exact differential equations

A stochastic representation based on a physical transport principle is proposed to account for mesoscale eddy effects on the evolution of the large-scale flow. This framework arises from a decomposition of the Lagrangian velocity into a smooth (in time) component and a highly oscillating term. One important characteristic of this random model is that it conserves the energy of any transported scalar

In this study, we present model results derived from the Tsunami Current Benchmarking Workshop held by the NTHMP (National Tsunami Hazard Mitigation Program) at Portland, Oregon, US, in February 2015 for the two benchmark problems dealing with field data. In this workshop, the Tsunami-HySEA model was used to perform the five proposed numerical benchmarks. The other three benchmarks, which are based

To describe large amplitude internal solitary waves in a two-layer system, we consider the high-order unidirectional (HOU) model that extends the Korteweg–de Vries equation with high-order nonlinearity and leading-order nonlinear dispersion. While the original HOU model is valid only for weakly nonlinear waves, its coefficients depending on the depth and density ratios are adjusted such that the adjusted

A two-dimensional, vertical section of the Strait of Gibraltar is simulated numerically with the nonhydrostatic/non-Boussinesq three-dimensional CROCO model to investigate details of small-scale dynamics. The proposed configuration is simple, computationally efficient and incorporates the configuration of sills characteristic of this region. Despite the shortcomings of a 2D representation, this configuration

The unstructured mesh, discontinuous Galerkin finite element discretisation based coastal ocean model, Thetis, has been extended to include non-hydrostatic (buoyancy-driven and free surface) dynamics. Two alternative approaches to achieve this are described in this work. The first (a 3D based algorithm) makes use of prismatic element based meshes and uses a split-step pressure projection method for

Accurate representation of vertical turbulent fluxes is crucial for numerical ocean modeling, both in global and coastal applications. The state-of-the-art approach is to use two-equation turbulence closure models which introduces two dynamic equations to the system. Solving these equations numerically, however, is challenging due to the strict requirement of positivity of the turbulent quantities

This study is concerned with the characteristics of coherent vortices within the turbulent air flow undulated by gravity and capillary–gravity water waves. The flow fields from the direct numerical simulations are analyzed. A formal scheme is developed to detect and classify the vortical structures. The scheme uses local analysis of the velocity-gradient tensor to define the vortex swirling core, and

The water masses exiting the Labrador Sea, and in particular the dense water mass formed by convection (i.e. Labrador Sea Water, LSW), are important components of the Atlantic Meridional Overturning Circulation (AMOC). Several studies have questioned the connection of the LSW production to the AMOC variability. This is partly due to the limited understanding of how this locally formed water mass leaves

The 200 m-thick surface layer of the Arctic Ocean contains a lower salinity part in the Canadian Basin, receiving fresher water from the Pacific Ocean as well as rivers, and also a higher salinity part in the Eurasian Basin, receiving saltier water from the Greenland Sea. This surface layer receives atmospheric forcing, and also partially mixes with the subsurface layer. Thus, thermohaline circulation

Three-dimensional (3D) obstacles on the bottom are common sites for the generation of vortices, internal waves and turbulence by ocean currents. Turbulence-resolving simulations are conducted for stratified flow past a conical hill, a canonical example of 3D obstacles. Motivated by the use of slip boundary condition (BC) and drag-law (effectively partial slip) BC in the literature on geophysical wakes

The quality of metocean forecasts at longer forecast ranges has a significant impact on maritime safety and offshore operations. A nonlinear ensemble averaging technique is demonstrated using neural networks applied to one year (2017) of Global ocean Wave Ensemble forecast System (GWES) data provided by NCEP. Post-processing algorithms are developed based on multilayer perceptron neural networks (NN)

In this study, we expand previous large eddy simulation (LES) modeling investigations of Langmuir turbulence (LT) to real ocean conditions using field observations collected under the multi-platform field campaign “Coupled Air–Sea Processes and Electromagnetic (EM) ducting Research (CASPER-East)”. The measurement site has strong local variabilities of temperature and salinity and experienced large

We study the 2D turbulent mixing of a passive scalar in the ocean mixed layer. As an example, we examine a steady-state convective mixed layer in which the boundary conditions are chosen so that the system reaches a dynamical equilibrium. In this idealized case, we parameterize the horizontally and temporally averaged fluxes as a functional of the horizontally and temporally averaged property gradients

A coastal ocean model is presented, adapting the unstructured C-grid discretisation (Ringler et al., 2010) employed in the MPAS (Model for Prediction Across Scales) global ocean model for use in an existing structured coastal modelling framework. Specifically, the discretisation of momentum advection, horizontal viscosity, Coriolis and continuity due to Ringler et al. are used; remaining terms are

River plume source-front connectivity, or the relationship between processes at the source, plume body and front, is investigated with numerical simulations of the Merrimack River plume using the Regional Ocean modeling System (ROMS). Source water, i.e. water discharged from the estuary during an ebb pulse, overtakes the front as it propagates offshore, resulting in the strong convergence that exists

Dynamical climate models have been extensively used over the last decade to perform seasonal sea ice predictions in the context of ensemble forecasting. To date, the sensitivity to the initial conditions has received the most attention through the evaluation of the theoretical limit of Antarctic sea ice predictability imposed by the chaotic evolution of the climate system. The respective contributions

In this study, we investigated the short-term dynamics of upwelling off the west coast of Hainan Island (UWH) by combining Moderate Resolution Imaging Spectroradiometer (MODIS) infrared sea surface temperature (SST) images and Regional Ocean Modeling System (ROMS) simulations. MODIS observations showed that the UWH could exhibit rapid temporal variations, where the SST could increase or decrease by

Representing the net freshwater flux at river mouths is challenging for global and regional scale ocean modelling. Although rivers are well known to affect both the coastal and basin-wide circulation and dynamics, coarse resolution ocean models cannot resolve the estuarine dynamics and are usually forced at river outlets in a simplistic way, with climatological runoff and zero or constant salinity

The model of coastal waves based on the depth-averaging of the large eddy simulation equations (Kazakova and Richard, 2019) is extended to the case of regular and irregular wave trains. To take into account a stronger turbulence, the third moment of the horizontal velocity is modelled with a gradient-diffusion hypothesis. The effect of this new diffusive term is to smooth and regularize the solutions

In this paper, we explore the secondary flows in the Danish Straits using observations and numerical simulations performed with the unstructured-grid hydrodynamic model SCHISM covering the North Sea and Baltic Sea. The straits are resolved on scales of up to ∼100 m. Given that large-scale atmospheric variability dominates the transport in these straits, we focus on the processes with subtidal time

Baroclinic eddy restratification strongly influences the ocean’s general circulation and tracer budgets, and has been routinely parameterized via the Gent–McWilliams (GM) scheme in coarse-resolution ocean climate models. These parameterizations have been improved via refinements of the GM eddy transfer coefficient using eddy-resolving simulations and theoretical developments. However, previous efforts

Open-ocean deep convection (DC), forming a link between the upper and the deep ocean dynamics, is observed in a few localized sites of the World Ocean. In the present paper, we further develop an analytical model of isolated vertically homogenized water columns, up to a few kilometers deep, usually referred to as convective chimneys. We derive analytical solutions for evolution of a chimney during