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Major update of the physics of the third generation models will be presented. The new source terms for wind input, whitecapping dissipation, interaction of waves with adverse winds (negative input) and swell attenuation have been developed and implemented in WAVEWATCH-III, SWAN and WAM models. Physics and parameterisations for the new source functions are based on observations, which allowed us to reveal features and processes previously unknown and not accounted for. For extreme conditions, physics of the wind input and whitecapping dissipation terms exhibit additional features irrelevant or inactive at moderate weather.In particular, the wave growth term was shown to be a nonlinear function of wave steepness (spectral density). Additionally, the wave breaking was found to enhance the wind input. Relative reduction of the wind input at strong-wind/steep-wave conditions was observed, due to full flow separation found at such circumstances. At strong wind forcing, this causes saturation of the sea drag.Spectral distribution of the whitecapping dissipation is the most elusive function to measure. Breaking of waves, and hence such dissipation exhibits a clear threshold behaviour in terms of wave steepness (or saturation spectrum). Other novel observed features are cumulative effect away from the spectral peak (dissipation is not local in wavenumber space), directional bimodality. It was found that at moderate winds the dissipation is fully determined by the wave spectrum whereas at strong winds it is a function of the wind speed.In absence of breaking (swell or other circumstances when the spectral density is below the threshold), other energy sink has to be invoked. It is based on observations of wave-turbulence interactions, and dependence of such interactions on wave steepness.Interaction of the waves with adverse wind is a necessary additional term if the above-mentioned wind input function is employed, since this function only describes forcing of waves by the following wind. These dependences are calibrated by means of observations in tropical cyclones.In order to test the source functions independently, and control the flux balance in the model, additional observation-based constraints are implemented. At each time step, the total momentum input is verified to match an independently known wind stress.Qualitative and quantitative effects and properties of the observation-based source terms are parameterised, and the parameterisations are presented in forms suitable for spectral wave models. The new versions of the models have undergone extensive testing by means of academic tests, regional and global wave hindcast, modelling extreme conditions ranging from tropical cyclones to the marginal ice zone.

The hydrodynamical process of breaking water waves is still a source of many unsolved questions. An extensive research work has been carried out during the last decades in order to quantify and define the associated energy redistribution, which directly influences a wide range of climate processes, maritime applications, and oceanic phenomena.Naturally, waves become steeper toward the inception of breaking; however, there is still a lack of unanimity regarding the relationship between breaking probability statistics and wave steepness. Here we present a detailed analysis of different sea states from the Black Sea measurements and from a closed wind-wave flume experiments. Together with the wind-derived parameters, the water wave statistics were gathered using an innovative breaking wave detection algorithm. The algorithm was recently developed to allow accurate detection of breaking waves based on the phase-time approach and wavelet analysis to identify breaking-associated patterns in the instantaneous frequency variations of surface elevation fluctuations. The in-depth analysis of breaking and non-breaking wave statistics included wave-by-wave calculations resulting in steepness and celerities of the local wave, derived from the local wave frequency and wavenumber. Finally, the findings, after investigation and validation, presented a skewed Gaussian-like steepness histogram, revealing that both non-breaking and breaking waves can reach steep profiles, above the Stokes limit.

Funding Information: Sasan Tavakoli was supported by a Melbourne Research Scholarship. Alexander V. Babanin acknowledges support through the US ONR and ONRG (grant no. N62909-20-1-2080). Publisher Copyright: © 2023 Sasan Tavakoli. Theoretical models for the prediction of decay rate and dispersion process of gravity waves traveling into an integrated ice cover expanded over a long way are introduced. The term "wet beam"is chosen to refer to these models as they are developed by incorporating water-based damping and added mass forces. Presented wet beam models differ from each other according to the rheological behavior considered for the ice cover. Two-parameter viscoelastic solid models accommodating Kelvin-Voigt (KV) and Maxwell mechanisms along with a one-parameter elastic solid model are used to describe the rheological behavior of the ice layer. Quantitative comparison between the landfast ice field data and model predictions suggests that wet beam models, adopted with both KV and Maxwell mechanisms, predict the decay rate more accurately compared to a dry beam model. Furthermore, the wet beam models, adopted with both KV and Maxwell mechanisms, are found to construct decay rates of disintegrated ice fields, though they are built for a continuous ice field. Finally, it is found that wet beam models can accurately construct decay rate curves of freshwater ice, though they cannot predict the dispersion process of waves accurately. To overcome this limitation, three-parameter solid models, termed standard linear solid (SLS) mechanisms, are suggested to be used to re-formulate the dispersion relationship of wet beam models, which were seen to construct decay rates and dispersion curves of freshwater ice with an acceptable level of accuracy. Overall, the two-parameter wet beam dispersion relationships presented in this research are observed to predict decay rates and dispersion process of waves traveling into actual ice covers, though three-parameter wet beam models were seen to reconstruct the those of freshwater ice formed in a wave flume. The wet beam models presented in this research can be implemented in spectral models on a large geophysical scale.

A recent study investigated whether it is physically feasible to generate the tail of a JONSWAP wave spectrum in a basin, and what the influence of wave breaking is on the energy content of this high frequency tail. It has been observed in basin measurements at MARIN that in steep sea states a dip starts to develop in the high frequency tail of the spectrum. This dip occurs due to non-linear wave interactions and/or wave breaking and a resulting energy shift and dissipation. This effect cannot be compensated by adding more energy at the wave maker at these frequencies, as the energy will continue to shift/dissipate as more non-linear interaction and wave breaking occurs. The objective of this research was to investigate whether a similar energy dip would occur in real environments or whether the effect is related to the fact that in lab environments the waves are generated at one location of the basin and not through wind blowing over the sea surface continuously. In cooperation with the University of Melbourne and MetOcean Research, several examples have been found in full scale measurements as well as non-linear wave simulations where a similar energy dip appears to occur. In this paper the physics involved in the reduced energy of the high frequency tail of very steep wave spectra are discussed and basin wave measurements are compared to nonlinear simulations and full scale measurements.

In the presentation, wave-induced influences at the ocean side will be discussed. While the role of breaking waves in producing turbulence is well appreciated, the turbulence produced by wave orbital motion at the vertical scale of wavelength – is not. Such mixing, however, produces feedbacks to the ocean circulation at scales from weather to climate. In order to account for the wave-turbulence effects, large-scale air-sea interaction models need to be coupled with wave models. Theory and practical applications for the wave-induced turbulence are reviewed in the presentation. Analytical approaches for the wave turbulence include viscous and instability theories which appear to be linked. This was verified through direct numerical simulations with fully nonlinear wave model coupled with three-dimensional (LES) model for turbulence. Furthermore, dedicated laboratory experiments and field observations, both in situ and by means of remote sensing, confirmed and validated the conclusions of theory and academic simulations and tests. Finally implementations of the wave-turbulence modules in models for Tropical Cyclones, ocean circulation and sea ice will be demonstrated.

Material tracers at the ocean surface disperse under the influence of the quasi-random forces that act on the ocean surface. These forces may include ocean turbulence, wind, and surface waves. Currently, wind and ocean turbulence are assumed to be the important drivers of dispersion of the floating tracer particles. Despite some theoretical results and laboratory experiments, the experimental proof of the significant contribution of wave induced dispersion in overall transport of large-scale geophysical systems remains elusive. This is mainly due to a lack of practical observations.In this study we aim to estimate the contribution of wave-induced dispersion in comparison with conventional mechanisms of dispersion due to ocean turbulence. We do so through the analysis of in-situ observations of surface drifters deployed across the seas and oceans. The experimental dataset include data from the Global Drifter Program and newly obtained data through cluster deployment of Spotter wave buoys. The results suggest that waves during marine storm conditions may be a critical driver of surface tracer dispersion during the first ten days after the storm and at horizontal length scales up to the order of 10 km. Our results imply that accurate information of wave conditions is required for accurate prediction of tracer dispersion at short to intermediate time and length scales.

Variability in sea ice conditions, combined with strong couplings to the atmosphere and the ocean, lead to a broad range of complex sea ice dynamics. More in-situ measurements are needed to better identify the phenomena and mechanisms that govern sea ice growth, drift, and breakup. To this end, we have gathered a dataset of in-situ observations of sea ice drift and waves in ice. A total of 15 deployments were performed over a period of 5 years in both the Arctic and Antarctic, involving 72 instruments. These provide both GPS drift tracks, and measurements of waves in ice. The data can, in turn, be used for tuning sea ice drift models, investigating waves damping by sea ice, and helping calibrate other sea ice measurement techniques, such as satellite based observations.

Probabilistic modelling and statistical analysis of environmental conditions is important for the design and assessment of ships and other marine structures. It will give a necessary input to structural reliability assessments and risk analysis and provides a means to identify design conditions that structures are expected to withstand in their lifetime. In this paper, recent developments in statistical modelling of relevant metocean variables describing the environment at sea will be reviewed and presented. This includes a review of statistical modelling applied to such data, for example wave-parameters, but also some theoretical and methodological developments from other fields of applications will be reviewed. The paper is divided into different sub-sections addressing various aspects of statistical modelling of the ocean environment, such as long-term and short-term statistics, extreme value analysis, non-stationary analysis and covariate effects, multivariate analysis and joint distributions, spatial statistics and machine learning applications. This distinction into sub-topics may be somewhat arbitrary, and some papers address several of these topics, e.g. non-stationary, multivariate extreme value statistics for spatial data, but it is believed to be useful to still keep separate sections for the main aspects. It is believed that this overview of recent developments in statistical modelling of the ocean environment will be useful for anyone involved in design or risk assessment of marine structures, and that it may contribute to push the state of the art and industry practice.

We present the idea to experimentaly test the empirical models used in fluid mechanics. The models consider that the waves develop due the wind energy trasferred from the air to the urface of the water. However, all of those models were validated considering data at sea level, with effectively fixed air density. Here we propose to test the adjustment of the empirical coefficients studying the waves generated in Lake Titikaka, which is located at an altitute high enough (3800 m) to have a reduced atmospheric pressure. Lake Titikaka is located in the North side of the Altiplano (high plateu) in South America. It is shared between Bolivia and Peru, and it is, by far, the largest water body in the region, and at such altitudes in general. So it becomes a dominant geographical and climatic unit in the South American Altiplano, which has a desert–like climate, with monsoon-type rainy season (November to February) and a long dry season (March to October). During the dry season (local winter) the daily temperature cycle goes from maxima around 15 °C (past noon) to freezing minima near -5 °C (before dawn). This temperature span is larger than the seasonal difference, around 5 °C, between summer and winter. Due to its large water mass, the Lake hampers the temperature variations and avoids the freezing of both the lake itself and its shores. The daily temperature fluctuations cause also a daily wind-intensity cycle, with maxima just before the sunset. Lake Titikaka has an alongated shape with a long axis of 120 km in the NW-SE direction, and its short axis of 50 km in the NE-SW direction; with a large peninsula on the South shore (Copacabana). This size, plus deep waters (in excess of 250 m, pelagic condition) allows development of extnsive waves produced by the surface winds, coming predominantly from the North. The shores of Lake Titikaka have several geographical features, among others: delta rivers, sandy beaches and rock cliffs. The (“main”) study site is located in the large portion of the lake, near a mid-point between Santiago de Huata and the Isla de la Luna (Moon Island) as far possible from the shores.

The ambient sound near the ocean surface is controlled by many processes, while wave breaking becomes the dominant factor once it occurs. Laboratory experiment shows that a severer breaker will result in a higher sound level and a larger mean bubble size. This relationship indicates a potential to extract information about wave breaking from acoustic records. Based on both laboratory and field experiments, a passive acoustic method has been developed to determine the wave breaking dissipation rate across the spectrum which had been extremely difficult to obtain in the open sea. The laboratory experiments were carried out in a flume at the University of Adelaide. Waves of different amplitudes and periods were generated and triggered to break by an underwater obstacle. The wave profiles before and after breaking were measured by two capacitance probes to calculate their breaking severities. The acoustic noise emitted by bubbles was recorded by a hydrophone located right under the breaking zone and the mean bubble sizes were computed on the basis of the relationship between bubble radius and acoustic frequency. A non-dimensional empirical formula between breaking severity and mean bubble size was established then applied to acoustic measurements in Lake George, New South Wales, Australia. Acoustic pulse amplitude, power spectral density of acoustic spectrum and the ratio between acoustic pulse amplitude and period were analyzed to identify the acoustic pulses truly produced by bubbles. The mean bubble sizes of each breaker were deduced from the acoustic records and further converted into their breaking severities. Combined with the wave scale information extracted from wave surface records, the spectral dissipation rates in Lake George were finally obtained. The acoustic based results are compared with various kinds of whitecapping dissipation source terms of WAVEWATCH III® and their differences are discussed.

Ocean surface waves and wave breaking play a pivotal role in air-sea Carbon Dioxide (CO2) gas exchange by producing abundant turbulence and bubbles. Contemporary gas transfer models are generally implemented with wind speed, rather than wave parameters, to quantify CO2 transfer velocity (KCO2). In our work, the direct relationship of KCO2 and waves is explored through the combination of laboratory experiment, field observational data and estimation of global ocean uptake of CO2.In laboratory, the waves and CO2 transfer at water surface are forced for simultaneous measurements in a wind-wave flume. Three types of waves are exercised: mechanically generated monochromatic waves, pure wind waves with 10-meter wind speed ranging from 4.5 m/s to 15.5 m/s, and the coupling of monochromatic waves with superimposed wind force. The results show that KCO2 is well correlated with wave height and orbital velocity. In the connection of KCO2 with breakers, wave breaking probability (bT) should also be considered. The wind speed is competent too in describing KCO2 but may be inadequate for varied wave ages. A non-dimensional formula (hereafter the RHM model) is proposed in which gas transfer velocity is expressed as a main function of wave Reynolds number (RHM = UwHs/νw, where Uw is wave orbital velocity, Hs is significant wave height, νw is viscosity of water) while wind is accounted as an enhancement factor (1+Û, where Û is non-dimensional wind speed denoting the reverse of wave age). For wave breaking dominated gas exchange, second formula (hereafter the BT model) is developed by replacing components of RHM with breaker’s statistics and integrates an additional factor of bT. Utilizing campaign observations from open ocean, the RHM model can effectively reconcile the laboratory and field data sets. The BT model related with wave breaking, on the other hand, is adapted by including a complementary term of bubble-mediated gas transfer in which the bubble injection rate is parameterized with RHM. The updated BT model also performs well for the data. The conventional wind-based models show similar features as in laboratory experiments: the wind speed successfully captures the variation of gas transfer for respective observation yet is insufficient to neutralize the gaps among data sets.Our wave-based gas transfer models are applied for the estimation of net annual CO2 fluxes of global ocean in the period of year 1985-2017. The results are in high agreement with previous studies. The wind-based gas transfer models might underestimate the CO2 fluxes although the estimations still distribute within the range of uncertainty. Moreover, the models using wave parameters are found advantageous over the wind-based models in reducing the uncertainties of gas fluxes.

Spray produced in Tropical Cyclones affects the dynamic and heat fluxes between the atmosphere and ocean, and thus can influence the Cyclone intensity in a number of ways. Measurements of the Sea Spray Generation Function (SSGF) in situ, however, are extremely challenging and correspondingly rare, and uncertainties in quantifying SSGF reach 1000 times.In the presentation, measurements of the total volume of spray by means of a laser array in Tropical Cyclones Olwyn (2015) and Veronica (2019) in the Indian Ocean will be reported. They are used to develop a parameterisation of SSGF at wind speeds ranging from light to extreme. It is argued that the spray is produced by wind-over-the-waves, and therefore wave properties are also accounted for in the parameterisation.

Hydrodynamic processes at air-sea interface play a significant role on air-sea CO2 gas exchange, which further affects global carbon cycle and climate change. CO2 gas transfer velocity (KCO2) is generally parameterized with wind speed but ocean surface waves have direct impact on the gas exchange. Thus, the relationship between wave breaking and CO2 gas exchange was studied through laboratory experiments and by utilizing field campaign data. The results from laboratory show that wave breaking plays a significant role in CO2 gas exchange in all experiments while wind forcing can also influence KCO2. A non-dimensional empirical formula is established in which KCO2 is expressed as the product of wave breaking probability, transformed Reynolds number and an enhancement factor of wind speed. The parameterization is then improved by considering the bubble-mediated gas transfer based on both laboratory and ship campaign data sets. In the end, the formula is employed in the estimation of global CO2 uptake by ocean and the result is found consistent with reported values.

Water wave breaking represents one of the most arduous problems in fluid mechanics. Understanding the process of wave breaking and developing an ability to quantify the associated energy losses and redistribution are critical across a wide range of coastal oceanic applications, maritime navigation, and climate and hydrodynamic research. Naturally, waves become steeper toward the inception of breaking; however, there is still a lack of unanimity regarding the relationship between breaking probability statistics and wave steepness. Here, we present a detailed investigation of breaking vs non-breaking statistics estimated using a recently developed method for accurate detection of breaking waves, based on the phase-time approach to identify breaking-associated patterns in the instantaneous frequency variations of surface elevation fluctuations. The findings are based on data collected both in the open sea and in a laboratory wind wave flume. An in-depth examination of celerities and steepnesses of breaking and non-breaking waves is presented. The analysis, which involved wave-by-wave examination, produced skewed Gaussian-like steepness histograms, revealing that non-breaking waves and breaking waves can reach steeper profiles, above the Stokes limit. All extreme steepness values were investigated and are presented here.

The Marginal Ice Zone and Arctic Sea State programs examined the processes that govern evolution of the rapidly changing seasonal ice zone in the Beaufort Sea. Autonomous platforms operating from the ice and within the water column collected measurements across the atmosphere-ice-ocean system and provided the persistence to sample continuously through the springtime retreat and autumn advance of sea ice. Autonomous platforms also allowed operational modalities that reduced the field programs’ logistical requirements. Observations indicate that thermodynamics, especially the radiative balances of the ice-albedo feedback, govern the seasonal cycle of sea ice, with the role of surface waves confined to specific events. Continuous sampling from winter into autumn also reveals the imprint of winter ice conditions and fracturing on summertime floe size distribution. These programs demonstrate effective use of integrated systems of autonomous platforms for persistent, multiscale Arctic observing. Networks of autonomous systems are well suited to capturing the vast scales of variability inherent in the Arctic system.

In 1998 the Australian Government released ‘Australia’s Ocean Policy: Caring, Understanding, Using Wisely’ (Environment Australia 1998a). The policy, released in the International Year of Oceans, r...