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

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 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

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 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

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

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

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 jet obtained with the Large Eddy Simulation (LES) were used to predict the migration of the oil droplets. Two Lagrangian

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 AMSR2

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 triad interaction

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 observations

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

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 P0DG and piecewise-linear P1DG 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 widely-adopted

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 the Gulf

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 twin

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 from

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

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

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