ORCID Profile
0000-0003-3112-6856
Current Organisation
University of Melbourne
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Physical Oceanography | Ocean Engineering | Maritime Engineering | Glaciology | Turbulent Flows | Transport Engineering | Tropospheric and Stratospheric Physics | Atmospheric Sciences | Physical Geography and Environmental Geoscience | Oceanography | Maritime Engineering not elsewhere classified | Numerical Computation | Climate Change Processes | Earth Sciences not elsewhere classified | Theoretical and Applied Mechanics | Fluidisation and Fluid Mechanics | Interdisciplinary Engineering | Fluid Physics |
ANZSRC Socio-Economic Objective (SEO)
Climate Change Models | Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Atmospheric Processes and Dynamics | Antarctic and Sub-Antarctic Oceanography | Wind Energy | Oil and Gas Extraction | Natural Hazards in Marine Environments | Physical and Chemical Conditions of Water in Marine Environments | Natural Hazards in Coastal and Estuarine Environments | Global Effects of Climate Change and Variability (excl. Australia, New Zealand, Antarctica and the South Pacific) (excl. Social Impacts) | Expanding Knowledge in the Earth Sciences | Expanding Knowledge in the Physical Sciences | Coastal Sea Freight Transport | International Sea Freight Transport (excl. Live Animal Transport)
Related Links
Publications
Wave attenuation due to ice cover
Publisher: American Society of Mechanical Engineers
Date: 25-06-2017
Abstract: Waves penetrate deep into the ice covered seas, inducing breakup of the ice cover. Concomitantly, the ice cover attenuates the wave energy over distance, so that wave impacts die out eventually. Observations of wave attenuation and concurrent wave-induced breakup in the literature are serendipitous due to difficulties in making measurements in ice covered seas. Hence understanding of wave-ice interactions remain uncertain. Here we present measurements of wave propagation through ice covered waters in the new experimental wave-ice facility at the University of Melbourne. The facility comprises of a 14m long and 0.76m wide flume in a refrigerated chamber, where temperatures can be lowered down to −12 degrees Celsius to generate a continuous ice cover on the water surface. A wave maker, installed at one end, is used to generate regular waves, ranging from gently-sloping to storm-like conditions. Wave attenuation rates are determined from video-camera images of the displacements of markers embedded in the ice cover. The experiments investigated wave propagation through the continuous ice cover, breakup, and propagation through the broken ice cover. Spatial evolution of the breakup and geometrical properties of floes are monitored and correlated with incident wave properties. Wave attenuation over broken ice is investigated and compared against the continuous ice case.
Meridional and vertical variations of the water vapour isotopic composition in the marine boundary layer over the Atlantic and Southern Ocean
Publisher: Copernicus GmbH
Date: 15-05-2020
Abstract: Abstract. Stable water isotopologues (SWIs) are useful tracers of moist diabatic processes in the atmospheric water cycle. They provide a framework to analyse moist processes on a range of timescales from large-scale moisture transport to cloud formation, precipitation and small-scale turbulent mixing. Laser spectrometric measurements on research vessels produce high-resolution time series of the variability of the water vapour isotopic composition in the marine boundary layer. In this study, we present a 5-month continuous time series of such ship-based measurements of δ2H and δ18O from the Antarctic Circumnavigation Expedition (ACE) in the Atlantic and the Southern Ocean in the time period from November 2016 to April 2017. We analyse the drivers of meridional SWI variations in the marine boundary layer across erse climate zones in the Atlantic and Southern Ocean using Lagrangian moisture source diagnostics and relate vertical SWI differences to near-surface wind speed and ocean surface state. The median values of δ18O, δ2H and deuterium excess during ACE decrease continuously from low to high latitudes. These meridional SWI distributions reflect climatic conditions at the measurement and moisture source locations, such as air temperature, specific humidity and relative humidity with respect to sea surface temperature. The SWI variability at a given latitude is highest in the extratropics and polar regions with decreasing values equatorwards. This meridional distribution of SWI variability is explained by the variability in moisture source locations and its associated environmental conditions as well as transport processes. The westward-located moisture sources of water vapour in the extratropics are highly variable in extent and latitude due to the frequent passage of cyclones and thus widen the range of encountered SWI values in the marine boundary layer. Moisture loss during transport further contributes to the high SWI variability in the extratropics. In the subtropics and tropics, persistent anticyclones lead to well-confined narrow easterly moisture source regions, which is reflected in the weak SWI variability in these regions. Thus, the expected range of SWI signals at a given latitude strongly depends on the large-scale circulation. Furthermore, the ACE SWI time series recorded at 8.0 and 13.5 m above the ocean surface provide estimates of vertical SWI gradients in the lowermost marine boundary layer. On average, the vertical gradients with height found during ACE are -0.1‰m-1 for δ18O, -0.5‰m-1 for δ2H and 0.3 ‰ m−1 for deuterium excess. Careful calibration and post-processing of the SWI data and a detailed uncertainty analysis provide a solid basis for the presented gradients. Using sea spray concentrations and sea state conditions, we show that the vertical SWI gradients are particularly large during high wind speed conditions with increased contribution of sea spray evaporation or during low wind speed conditions due to weak vertical turbulent mixing. Although further SWI measurements at a higher vertical resolution are required to validate these findings, the simultaneous SWI measurements at several heights during ACE show the potential of SWIs as tracers for vertical mixing and sea spray evaporation in the lowermost marine boundary layer.
Letter: Hydroelastic interactions between water waves and floating freshwater ice
Publisher: AIP Publishing
Date: 09-2018
DOI: 10.1063/1.5050262
Abstract: Hydroelastic interactions between regular water waves and floating freshwater ice are investigated using laboratory experiments for a range of incident wave periods and steepnesses. It is shown that only incident waves with sufficiently long period and large steepness break up the ice cover and that the extent of breakup increases with increasing period and steepness. Furthermore, it is shown that an increasing proportion of the incident wave propagates through the ice-covered water as the period and steepness increase, indicating the existence of a positive feedback loop between the ice breakup and increased wave propagation.
Rogue waves in opposing currents: an experimental study on deterministic and stochastic wave trains
Publisher: Cambridge University Press (CUP)
Date: 16-03-2015
DOI: 10.1017/JFM.2015.132
Abstract: Interaction with an opposing current lifies wave modulation and accelerates nonlinear wave focusing in regular wavepackets. This results in large- litude waves, usually known as rogue waves, even if the wave conditions are less prone to extremes. Laboratory experiments in three independent facilities are presented here to assess the role of opposing currents in changing the statistical properties of unidirectional and directional mechanically generated random wavefields. The results demonstrate in a consistent and robust manner that opposing currents induce a sharp and rapid transition from weakly to strongly non-Gaussian properties. This is associated with a substantial increase in the probability of occurrence of rogue waves for unidirectional and directional sea states, for which the occurrence of extreme and rogue waves is normally the least expected.
15 priorities for wind-waves research: An Australian perspective
Publisher: American Meteorological Society
Date: 04-2020
Abstract: The Australian marine research, industry, and stakeholder community has recently undertaken an extensive collaborative process to identify the highest national priorities for wind-waves research. This was undertaken under the auspices of the Forum for Operational Oceanography Surface Waves Working Group. The main steps in the process were first, soliciting possible research questions from the community via an online survey second, reviewing the questions at a face-to-face workshop and third, online ranking of the research questions by in iduals. This process resulted in 15 identified priorities, covering research activities and the development of infrastructure. The top five priorities are 1) enhanced and updated nearshore and coastal bathymetry 2) improved understanding of extreme sea states 3) maintain and enhance the in situ buoy network 4) improved data access and sharing and 5) ensemble and probabilistic wave modeling and forecasting. In this paper, each of the 15 priorities is discussed in detail, providing insight into why each priority is important, and the current state of the art, both nationally and internationally, where relevant. While this process has been driven by Australian needs, it is likely that the results will be relevant to other marine-focused nations.
Spontaneous emergence of rogue waves in partially coherent waves: A quantitative experimental comparison between hydrodynamics and optics
Publisher: American Physical Society (APS)
Date: 16-01-2018
The velocity field underneath linear and nonlinear breaking rogue waves
Publisher: American Society of Mechanical Engineers
Date: 19-06-2016
Abstract: During the past decades, a large number of waves of extreme height and abnormal shape, also known as freak or rogue waves, have been recorded in the ocean. Velocities and related forces can be enormous and jeopardise the safety of marine structures. Here, we present an experimental study devoted to investigate the velocity field underneath a breaking rogue wave. The latter is replicated in the laboratory by means of dispersive focussing methods such as the New Wave Theory and nonlinear focussing techniques based on the Nonlinear Schrödinger equation. While the former is basically a liner method, the nonlinear focussing fully accounts for the dynamical evolution of the wave field. Experiments were carried out in the Extreme Air-Sea Interaction flume of the University of Melbourne using a Particle Image Velocimetry (PIV) system to measure the velocity field below the water surface. Measurements show that the mechanism of generation affects the shape of the breaking waves as well as the kinematic field and associated hydrodynamic forces. Particularly, the New Wave Theory leads to higher velocities and a more energetic breaker than the nonlinear focussing.
Statistical Properties of a Directional Wave Field: Direct Simulations of the Euler Equations and Second-Order Theory
Publisher: ASMEDC
Date: 2008
Abstract: It is well established that the modulational instability enhances the probability of occurrence for extreme events if waves are long crested. Recent studies, however, have shown that the coexistence of directional wave components can substantially reduce its effects. Here, direct numerical simulations of the Euler equations are used to investigate whether the modulational instability may produce significant deviations from second-order statistical properties of surface gravity waves when short crestness (i.e., directionality) is accounted for. The case of a broad-banded directional wave field (i.e. wind sea) is investigated. Results will show that the distribution proposed by Forristall [1] provides a good estimate of the simulated crest height also at low probability levels.
Second-Order Theory and Setup in Surface Gravity Waves: A Comparison with Experimental Data
Publisher: American Meteorological Society
Date: 11-2007
Abstract: The second-order, three-dimensional, finite-depth wave theory is here used to investigate the statistical properties of the surface elevation and wave crests of field data from Lake George, Australia. A direct comparison of experimental and numerical data shows that, as long as the nonlinearity is small, the second-order model describes the statistical properties of field data very accurately. By low-pass filtering the Lake George time series, there is evidence that some energetic wave groups are accompanied by a setup instead of a setdown. A numerical study of the coupling coefficient of the second-order model reveals that such an experimental result is consistent with the second-order theory, provided directional spreading is included in the wave spectrum. In particular, the coupling coefficient of the second-order difference contribution predicts a setup as a result of the interaction of two waves with the same frequency but with different directions. This result is also confirmed by numerical simulations. Bispectral analysis, furthermore, indicates that this setup is a statistically significant feature of the observed wave records.
The North Sea Andrea storm and numerical simulations
Publisher: Copernicus GmbH
Date: 05-06-2014
DOI: 10.5194/NHESS-14-1407-2014
Abstract: Abstract. A coupling of a spectral wave model with a nonlinear phase-resolving model is used to reconstruct the evolution of wave statistics during a storm crossing the North Sea on 8–9 November 2007. During this storm a rogue wave (named the Andrea wave) was recorded at the Ekofisk field. The wave has characteristics comparable to the well-known New Year wave measured by Statoil at the Draupner platform 1 January 1995. Hindcast data of the storm at the nearest grid point to the Ekofisk field are here applied as input to calculate the evolution of random realizations of the sea surface and its statistical properties. Numerical simulations are carried out using the Euler equations with a higher-order spectral method (HOSM). Results are compared with some characteristics of the Andrea wave record measured by the down-looking lasers at Ekofisk.
Modelling of the temporal and spatial evolutions of weakly nonlinear random directional waves with the modified nonlinear Schrödinger equations
Publisher: Elsevier BV
Date: 02-2016
Probability of Occurrence of Extreme Waves in Three Dimensional Mechanically Generated Random Wave Fields: A Comparison With Numerical Simulations
Publisher: ASMEDC
Date: 2011
Abstract: Experimental and numerical investigations reveal that nonlinear modulational instability can significantly affect the probability of occurrence of extreme waves, especially if waves are sufficiently steep and narrow banded both in the frequency and directional domain. However, it is not yet completely clear whether numerical simulations can provide an accurate quantitative estimate of experimental results. Here the potential Euler equations are used to assess the ability of numerical models to describe the evolution of statistical properties of mechanically generated directional, random wave fields and in particular the evolution of the kurtosis. Results show that simulations provide a good quantitative estimate of experimental observations within a broad range of wave directional width.
Wave crest and trough distributions in a broad-banded directional wave field
Publisher: Elsevier BV
Date: 12-2008
Long-Term and Seasonal Variability of Wind and Wave Extremes in the Arctic Ocean
Publisher: Frontiers Media SA
Date: 19-05-2022
DOI: 10.3389/FMARS.2022.802022
Abstract: Over recent decades, the Arctic Ocean has experienced dramatic variations due to climate change. By retreating at a rate of 13% per decade, sea ice has opened up significant areas of ocean, enabling wind to blow over larger fetches and potentially enhancing wave climate. Considering the intense seasonality and the rapid changes to the Arctic Ocean, a non-stationary approach is applied to time-varying statistical properties to investigate historical trends of extreme values. The analysis is based on a 28-year wave hindcast (from 1991 to 2018) that was simulated using the WAVEWATCH III wave model forced by ERA5 winds. Despite a marginal increase in wind speed (up to about 5%), results demonstrate substantial seasonal differences and robust positive trends in extreme wave height, especially in the Beaufort and East Siberian seas, with increasing rates in areal average of the 100-year return period up to 60%. The reported variations in extreme wave height are directly associated with a more effective wind forcing in emerging open waters that drives waves to build up more energy, thus confirming the positive feedback of sea ice decline on wave climate.
Investigation of unexpected sea-states
Publisher: ASMEDC
Date: 2004
Abstract: It is assumed that dangerous and unexpected sea-states may occur if the sea conditions are fairly rough. It is therefore of concern to meteo centers to include sea-state related parameters in marine weather forecast when they exceed a certain threshold. To select appropriate parameters that can point at dangerous wave events, the sea-state at the time and location of shipping accidents reported as being due to bad weather by the Lloyd’s Marine Information Service (LMIS) were extracted from the ECMWF ERA-40 archive. The analysis of these wave parameters reveals the occurrence of apparently rather low sea-states (e.g. Hm0 & 4 m). To test the findings against the related oceanographic features, wave climatology was computed. The present study aims at finding a possible correlation between wave climate and shipping incidents to identify warning criteria.
Towards the identification of warning criteria: Analysis of a ship accident database
Publisher: Elsevier BV
Date: 12-2005
Estimation of kinetic energy dissipation from breaking waves in the wave crest region
Publisher: American Meteorological Society
Date: 05-2017
Abstract: Wave-induced turbulence due to breaking in the absence of surface shear stresses is investigated experimentally. A high-fidelity particle image velocimetry (PIV) technique is used to measure the turbulence near the water surface, inside the wave crests. The spatial velocity vector fields of the breaking waves acquired from PIV provide accurate vertical velocity profiles near the air–water interface, as well as wavenumber velocity spectra beneath the breaking waves at different depths. These velocity spectra exhibit a Kolmogorov interval at high wavenumbers, indicating the presence of isotropic turbulence and permitting an estimation of energy dissipation rates. The depth dependence of dissipation rates of the breaking waves generated in the laboratory shows a scaling similar to that found in wind-forced breaking waves in the field. A phase dependence in the dissipation rates of turbulence kinetic energy is also observed, which should be considered to improve the accuracy of the estimated and modeled wave energy dissipation.
Drift of Pancake Ice Floes in the Winter Antarctic Marginal Ice Zone During Polar Cyclones
Publisher: American Geophysical Union (AGU)
Date: 03-2020
DOI: 10.1029/2019JC015418
Abstract: High temporal resolution in situ measurements of pancake ice drift are presented, from a pair of buoys deployed on floes in the Antarctic marginal ice zone during the winter sea ice expansion, over 9 days in which the region was impacted by four polar cyclones. Concomitant measurements of wave‐in‐ice activity from the buoys are used to infer that the ice remained unconsolidated, and pancake ice conditions were maintained over at least the first 7 days. Analysis of the data shows (i) the fastest reported ice drift speeds in the Southern Ocean (ii) high correlation of drift velocities with the surface wind velocities, indicating absence of internal ice stresses km from the ice edge where remotely sensed ice concentration is 100% and (iii) presence of a strong inertial signature with a 13 hr period. A Lagrangian free drift model is developed, including a term for geostrophic currents that reproduce the 13 hr period signature in the ice motion. The calibrated model provides accurate predictions of the ice drift for up to 2 days, and the calibrated parameters provide estimates of wind and ocean drag for pancake floes under storm conditions.
Overview of the Antarctic Circumnavigation Expedition: Study of Preindustrial-like Aerosols and Their Climate Effects (ACE-SPACE)
Publisher: American Meteorological Society
Date: 11-2019
Abstract: Uncertainty in radiative forcing caused by aerosol–cloud interactions is about twice as large as for CO 2 and remains the least well understood anthropogenic contribution to climate change. A major cause of uncertainty is the poorly quantified state of aerosols in the pristine preindustrial atmosphere, which defines the baseline against which anthropogenic effects are calculated. The Southern Ocean is one of the few remaining near-pristine aerosol environments on Earth, but there are very few measurements to help evaluate models. The Antarctic Circumnavigation Expedition: Study of Preindustrial-like Aerosols and their Climate Effects (ACE-SPACE) took place between December 2016 and March 2017 and covered the entire Southern Ocean region (Indian, Pacific, and Atlantic Oceans length of ship track ,000 km) including previously unexplored areas. In situ measurements covered aerosol characteristics [e.g., chemical composition, size distributions, and cloud condensation nuclei (CCN) number concentrations], trace gases, and meteorological variables. Remote sensing observations of cloud properties, the physical and microbial ocean state, and back trajectory analyses are used to interpret the in situ data. The contribution of sea spray to CCN in the westerly wind belt can be larger than 50%. The abundance of methanesulfonic acid indicates local and regional microbial influence on CCN abundance in Antarctic coastal waters and in the open ocean. We use the in situ data to evaluate simulated CCN concentrations from a global aerosol model. The extensive, available ACE-SPACE dataset ( ommunities/spi-ace?page=1& size=20 ) provides an unprecedented opportunity to evaluate models and to reduce the uncertainty in radiative forcing associated with the natural processes of aerosol emission, formation, transport, and processing occurring over the pristine Southern Ocean.
An experimental comparison of velocities underneath focussed breaking waves
Publisher: Elsevier BV
Date: 05-2018
Non-Gaussian properties of second-order wave orbital velocity
Publisher: Elsevier BV
Date: 04-2016
Atmospheric drivers of a winter-to-spring Lagrangian sea-ice drift in the Eastern Antarctic marginal ice zone
Publisher: Cambridge University Press (CUP)
Date: 15-03-2022
DOI: 10.1017/JOG.2022.14
Abstract: Sea-ice drift in the Antarctic marginal ice zone (MIZ) is discussed using data from a 4-month-long drift of a buoy deployed on a pancake ice floe during the winter sea-ice expansion. We demonstrate increased meandering and drift speeds, and changes in the dynamical regimes of the absolute dispersion during cyclone activity, together with high correlations between drift velocities and wind from atmospheric reanalyses. This indicates a dominant physical control of wind forcing on ice drift and the persistence of free-drift conditions. These conditions occurred despite the buoy remaining largely in % ice concentrations and at distances km from the estimated ice edge. The drift is additionally characterised by a strong inertial signature at 13.47 h, which appears initiated by passing cyclones. A wavelet analysis of the buoy's velocity confirms that the momentum transfer from winds at the multi-day frequencies is due to atmospheric forcing, while the initiation of inertial oscillations of sea ice has been identified as the secondary effect. Propagating storm-generated waves may initiate inertial oscillations by increasing the mobility of floes and enhance the drag of the inertial current. This analysis indicates that the Antarctic MIZ in the Indian Ocean sector remains much wider and mobile, during austral winter-to-spring, than defined by sea-ice concentration.
Maximum steepness of oceanic waves: Field and laboratory experiments
Publisher: American Geophysical Union (AGU)
Date: 03-2010
DOI: 10.1029/2009GL041771
Brief communication: Pancake ice floe size distribution during the winter expansion of the Antarctic marginal ice zone
Publisher: Copernicus GmbH
Date: 09-01-2019
Abstract: Abstract. The size distribution of pancake ice floes is calculated from images acquired during a voyage to the Antarctic marginal ice zone in the winter expansion season. Results show that 50 % of the sea ice area is made up of floes with diameters of 2.3–4 m. The floe size distribution shows two distinct slopes on either side of the 2.3–4 m range, neither of which conforms to a power law. Following a relevant recent study, it is conjectured that the growth of pancakes from frazil forms the distribution of small floes (D .3 m), and welding of pancakes forms the distribution of large floes (D m).
Statistics of Wave Orbital Velocity in Deep Water Random Directional Wave Fields
Publisher: American Society of Mechanical Engineers
Date: 07-2012
Abstract: A direct numerical simulation method is used to monitor the evolution of nonlinear random directional wave fields. The aim is to investigate the combined effect of high order nonlinearity and directional energy distribution on the statistics of wave orbital velocity. Results show that the development of modulational wave instability and the concurrent formation of large litude waves lead to a substantial departure of the statistics of the horizontal velocity from the Normal (or Gaussian) probability density function when the wave field is long crested. As short crestedness increases, departure from the Normal distribution gradually diminishes and eventually vanishes for sufficiently broad directional spreading.
A satellite altimetry data assimilation approach to optimise sea state estimates from vessel motion
Publisher: Elsevier BV
Date: 03-2023
Rogue waves in random sea states: An experimental perspective
Publisher: Springer International Publishing
Date: 2016
Sea State and Boundary Layer Stability Limit Sea Spray Aerosol Lifetime over the Southern Ocean
Publisher: Wiley
Date: 16-10-2020
A comparison of the measured North Sea Andrea rogue wave with numerical simulations
Publisher: Copernicus GmbH
Date: 25-09-2013
DOI: 10.5194/NHESSD-1-5033-2013
Abstract: Abstract. A coupling of a spectral wave model with a nonlinear phase resolving model is used to reconstruct the evolution of wave statistics during a storm crossing the North Sea on 8–9 November 2007. During this storm a rogue wave (named the Andrea wave) was recorded at the Ekofisk field. The wave has characteristics comparable to the well-known New Year wave measured by Statoil at the Draupner platform the 1 January 1995. Hindcast data of the storm are here applied as input to calculate random realizations of sea surface and evolution of its statistical properties associated with this specific wave event by solving the Euler equations with a Higher Order Spectral Method (HOSM). The numerical results are compared with the Andrea wave profile as well as characteristics of the Andrea wave record measured by the down-looking lasers at the Ekofisk field.
Three-dimensional imaging of waves and floes in the marginal ice zone during a cyclone
Publisher: Springer Science and Business Media LLC
Date: 06-08-2022
DOI: 10.1038/S41467-022-32036-2
Abstract: The marginal ice zone is the dynamic interface between the open ocean and consolidated inner pack ice. Surface gravity waves regulate marginal ice zone extent and properties, and, hence, atmosphere-ocean fluxes and ice advance/retreat. Over the past decade, seminal experimental c aigns have generated much needed measurements of wave evolution in the marginal ice zone, which, notwithstanding the prominent knowledge gaps that remain, are underpinning major advances in understanding the region’s role in the climate system. Here, we report three-dimensional imaging of waves from a moving vessel and simultaneous imaging of floe sizes, with the potential to enhance the marginal ice zone database substantially. The images give the direction–frequency wave spectrum, which we combine with concurrent measurements of wind speeds and reanalysis products to reveal the complex multi-component wind-plus-swell nature of a cyclone-driven wave field, and quantify evolution of large- litude waves in sea ice.
The effect of third-order nonlinearity on statistical properties of random directional waves in finite depth
Publisher: Copernicus GmbH
Date: 24-02-2009
Abstract: Abstract. It is well established that third-order nonlinearity produces a strong deviation from Gaussian statistics in water of infinite depth, provided the wave field is long crested, narrow banded and sufficiently steep. A reduction of third-order effects is however expected when the wave energy is distributed on a wide range of directions. In water of arbitrary depth, on the other hand, third-order effects tend to be suppressed by finite depth effects if waves are long crested. Numerical simulations of the truncated potential Euler equations are here used to address the combined effect of directionality and finite depth on the statistical properties of surface gravity waves only relative water depth kh greater than 0.8 are here considered. Results show that random directional wave fields in intermediate water depths, kh=O(1), weakly deviate from Gaussian statistics independently of the degree of directional spreading of the wave energy.
Fourier amplitude distribution and intermittency in mechanically generated surface gravity waves
Publisher: American Physical Society (APS)
Date: 15-07-2020
Development of a bimodal structure in ocean wave spectra
Publisher: American Geophysical Union (AGU)
Date: 03-03-2010
DOI: 10.1029/2009JC005495
Biogeochemistry and Physics of the Southern Ocean-Atmosphere System Explored With Data Science
Publisher: Copernicus GmbH
Date: 21-04-2021
DOI: 10.5194/ESD-2021-16
Abstract: Abstract. The Southern Ocean is a critical component of Earth’s climate system, but its remoteness makes it challenging to develop a holistic understanding of its processes from the small to the large scale. As a result, our knowledge of this vast region remains largely incomplete. The Antarctic Circumnavigation Expedition (ACE, austral summer 2016/2017) surveyed a large number of variables describing the dynamic state of the ocean and the atmosphere, the freshwater cycle, atmospheric chemistry, ocean biogeochemistry and microbiology. This circumpolar cruise included visits to twelve remote islands, the marginal ice zone, and the Antarctic coast. Here, we use 111 of the observed variables to study the latitudinal gradients, seasonality, shorter term variations, the geographic setting of environmental processes, and interactions between them over the duration of 90 days. To reduce the dimensionality and complexity of the dataset and make the relations between variables interpretable, we applied a sparse Principal Component Analysis (sPCA), which describes environmental processes through 14 latent variables. To derive a robust statistical perspective on these processes and to estimate the uncertainty in the sPCA decomposition, we have developed a bootstrap approach. We identified temporal patterns from diurnal to seasonal cycles, as well as geographical gradients and “hotspots” of interaction. Our results establish connections of oceanic, atmospheric, biological and terrestrial processes in an innovative way, while confirming many well known relations of the Southern Ocean system. More specifically, we identify: the important role of the oceanic circulations, frontal zones, and islands in shaping the nutrient availability that controls biological community composition and productivity that sea ice predominantly controls sea water salinity, d ens the wave field, and is associated with increased phytoplankton growth and net community productivity possibly due to iron fertilization and reduced light limitation and clear regional patterns of aerosol characteristics emerged, stressing the role of the sea state, atmospheric chemical processing, as well as source processes near “hotspots” for the availability of cloud condensation nuclei and hence cloud formation. A set of key variables and their combinations, such as the difference between the air and sea surface temperature, atmospheric pressure, sea surface height, geostrophic currents, upper ocean layer light intensity, surface wind speed and relative humidity, played an important role in the majority of latent variables, highlighting their importance for a large variety of processes and the necessity for Earth System Models to represent them adequately. In conclusion, our study highlights the use of sPCA to identify key ocean-atmosphere interactions across physical, chemical, and biological processes and their associated spatio-temporal scales. The sPCA processing code is available as open-access and we believe that our approach is widely applicable to other environmental field studies.
Laboratory Experiments on the Effects of a Variable Current Field on the Spectral Geometry of Water Waves
Publisher: American Meteorological Society
Date: 09-2016
Abstract: Laboratory experiments were performed to investigate the effects of a coflowing current field on the spectral shape of water waves. The results indicate that refraction is the main factor in modulating wave height and overall wave energy. Although the structure of the current field varies considerably, some current-induced patterns in the wave spectrum are observed. In high frequencies, the energy cascading generated by nonlinear interactions is suppressed, and the development of a spectral tail is disturbed, as a consequence of the detuning of the four-wave resonance conditions. Furthermore, the presence of currents slows the downshifting of the spectral peak. The suppression of the high-frequency energy under the influence of currents is more prominent as the spectral steepness increases. The energy suppression is also more accentuated and long-standing along the fetch when the directional spreading of waves is sufficiently broad. This result indicates that the current-induced detuning of resonant conditions is more effective when exact resonances are the primary mechanism of nonlinear interactions than when quasi resonances prevail (directionally narrow cases). Additionally, the directional analysis shows that the highly variable currents broaden the directional spreading of waves. The broadening is suggested to be related to random refraction and scattering of wave rays. The random disturbance of wavenumbers alters the nonlinear interaction conditions and weakens the energy exchanges among wave components, which is expressed in the suppression of the high-frequency energy.
Statistical Properties of Directional Ocean Waves: The Role of the Modulational Instability in the Formation of Extreme Events
Publisher: American Physical Society (APS)
Date: 20-03-2009
Water wave transmission and energy dissipation by a floating plate in the presence of overwash
Publisher: Cambridge University Press (CUP)
Date: 21-02-2020
DOI: 10.1017/JFM.2020.75
Observation of turbulence and intermittency in wave-induced oscillatory flows
Publisher: Elsevier BV
Date: 2019
Evolution of weakly nonlinear random directional waves: laboratory experiments and numerical simulations
Publisher: Cambridge University Press (CUP)
Date: 15-10-2010
DOI: 10.1017/S002211201000385X
Abstract: Nonlinear modulational instability of wavepackets is one of the mechanisms responsible for the formation of large- litude water waves. Here, mechanically generated waves in a three-dimensional basin and numerical simulations of nonlinear waves have been compared in order to assess the ability of numerical models to describe the evolution of weakly nonlinear waves and predict the probability of occurrence of extreme waves within a variety of random directional wave fields. Numerical simulations have been performed following two different approaches: numerical integration of a modified nonlinear Schrödinger equation and numerical integration of the potential Euler equations based on a higher-order spectral method. Whereas the first makes a narrow-banded approximation (both in frequency and direction), the latter is free from bandwidth constraints. Both models assume weakly nonlinear waves. On the whole, it has been found that the statistical properties of numerically simulated wave fields are in good quantitative agreement with laboratory observations. Moreover, this study shows that the modified nonlinear Schrödinger equation can also provide consistent results outside its narrow-banded domain of validity.
An idealised experimental model of ocean surface wave transmission by an ice floe
Publisher: Elsevier BV
Date: 12-2015
Occurrence of Extreme Waves in Finite Water Depth
Publisher: Springer International Publishing
Date: 02-09-2015
Wind Generated Rogue Waves in an Annular Wave Flume
Publisher: American Physical Society (APS)
Date: 07-04-2017
Statistical properties of mechanically generated surface gravity waves: a laboratory experiment in a three-dimensional wave basin
Publisher: Cambridge University Press (CUP)
Date: 25-05-2009
DOI: 10.1017/S002211200900603X
Abstract: A wave basin experiment has been performed in the MARINTEK laboratories, in one of the largest existing three-dimensional wave tanks in the world. The aim of the experiment is to investigate the effects of directional energy distribution on the statistical properties of surface gravity waves. Different degrees of directionality have been considered, starting from long-crested waves up to directional distributions with a spread of ±30° at the spectral peak. Particular attention is given to the tails of the distribution function of the surface elevation, wave heights and wave crests. Comparison with a simplified model based on second-order theory is reported. The results show that for long-crested, steep and narrow-banded waves, the second-order theory underestimates the probability of occurrence of large waves. As directional effects are included, the departure from second-order theory becomes less accentuated and the surface elevation is characterized by weak deviations from Gaussian statistics.
Non-Gaussian Properties of Shallow Water Waves in Crossing Seas
Publisher: Springer International Publishing
Date: 02-09-2015
Evaluation of the numerical wave model (WaveWatch III) for wave simulation in the Antarctic marginal ice zone
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-12247
Abstract: & & The Southern Ocean is the birthplace of the fiercest waves on the Earth, which play a fundamental role in global climate by regulating momentum, heat and gas exchanges between the atmosphere and ocean. At high latitudes, waves interact with Antarctic sea ice, another crucial player of the Earth's climate system, modulating its expansion in the winter and its retreat in summer and hence affecting the global albedo. Despite the impact of waves on climate, global wave models are considerably biased in the Southern Hemisphere, due to the scarcity of observations in these remote waters. This is exacerbated in the marginal ice zone, the region of ice-covered water between the compact ice or land and the open ocean, where surface waves, upper ocean and atmosphere interact with sea ice but the dominant physics are still largely unknown. To improve our understanding of physical processes in Southern Ocean and model capabilities, the Antarctic Circumnavigation Expedition (ACE) sailed these waters from December 2016 to March 2017 to acquire wave data (among other climate variables) both in the open ocean and Antarctic marginal ice zone. Observations were gathered using a radar-based wave and surface current monitoring system (WaMoS-II) built on board of the research icebreaker Akademik Tryoshnikov. Here, we discuss how these observations underpin the set up, calibration and validation of the WaveWatch III wave model over a domain covering the entire Southern Hemisphere, therefore spanning from tropical waters to the edge of sea ice (open waters only). The calibrated model will then be used to carry out a thorough assessment of different sea ice modules, to evaluate accuracy of predictions in the marginal ice zone. Test cases of waves-in-ice recorded during the Antarctic Circumnavigation Expeditions will be discussed in details.& &
Directional soliton and breather beams
Publisher: Proceedings of the National Academy of Sciences
Date: 26-04-2019
Abstract: Understanding the fundamental dynamics of directional and localized waves is of significant importance for modeling ocean waves as well as predicting extreme events. We report a theoretical framework, based on the universal (2D + 1) nonlinear Schrödinger equation, that allows the construction of slanted solitons and breathers on the water surface. Our corresponding wave flume observations emphasize and uniquely reveal that short-crested localizations can be described as a result of nonlinear wave dynamics, complementing the linear superposition and interference arguments as has been generally suggested for directional ocean waves.
Forced Migration, Oceanic Humanitarianism, and the Paradox of Danger and Saviour of a Vietnamese Refugee Boat Journey
Publisher: Cambridge University Press (CUP)
Date: 21-07-2022
DOI: 10.1017/S0018246X21000595
Abstract: The ocean is a central site of escape, danger, and rescue for refugees. It is also a place where oceanic humanitarianism is enacted. In histories of refugee migration, the combination of the ocean, weather, and climate in determining the fate of refugees has not been adequately examined. This article provides a critical analysis of a Vietnamese refugee boat journey in 1982, to demonstrate the paradoxical nature of the ocean as both a site of danger and saviour. Conventional historical methodologies alone cannot capture the complex role of the ocean and the weather in determining boat refugee journeys and rescues. Interdisciplinary research between historians and ocean engineers provides new evidence and understanding of how the ocean and weather influences the outcomes of refugees seeking asylum by boat. Numerical model predictions of sea state and ship motion – which enables the vessel's journey in past environmental conditions to be understood – integrated within historical analysis contributes to a fuller and more complex understanding of the nexus between environmental conditions and forced migration journeys. Ocean engineering produces a scientific narrative that historians can use, alongside oral histories and other sources, to theorize the ocean as an active agent.
Effects of an explosive polar cyclone crossing the Antarctic marginal ice zone
Publisher: American Geophysical Union (AGU)
Date: 12-06-2019
DOI: 10.1029/2019GL082457
Extreme Waves in Sea States Crossing an Oblique Current
Publisher: ASMEDC
Date: 2010
Abstract: Laboratory experiments have been carried out in the directional wave tank at Marintek (Norway) to study the nonlinear dynamics of surface gravity waves and the occurrence of extreme events, when the wave field traverses obliquely an ambient current. A condition of partial opposition has been considered. Tests on regular waves have shown that the current can trigger the formation of large litude waves. In random wave fields, however, this only results in a weak deviation from the statistical properties observed in absence of a current.
Experimental and numerical models of wave reflection and transmission by an ice floe
Publisher: American Society of Mechanical Engineers
Date: 25-06-2017
Abstract: The marginal ice zone (MIZ) is the outer part of the sea-ice covered ocean, where ice can be found in the form of large floating chucks better known as floes. Since it is the area where the most part of the interaction between ice cover and ocean waves takes place, it requires careful modelling. However existing mathematical models, based on the traditional thin-plate theory, underestimate waves attenuation for the most energetic waves, since the energy dissipation occurring during the process is not taken into account. New laboratory experimental and direct numerical models are presented here. In the experimental model a thin plastic plate is tested under the action of incident waves with varying litudes and periods. The same experimental set-up was reproduced using a numerical model, which was developed by coupling a High Order Spectral Numerical Wave Tank with the Navier-Stokes solver IHFOAM. Data from the experiments and numerical models confirm that non-linear effects lead to a decrease of wave transmission.
Predicting the occurrence of rogue waves in the presence of opposing currents with a high-order spectral method
Publisher: American Physical Society (APS)
Date: 17-06-2021
Recurrent solutions of the Alber equation initialized by Joint North Sea Wave Project spectra
Publisher: Cambridge University Press (CUP)
Date: 19-02-2013
DOI: 10.1017/JFM.2013.7
Abstract: Linear instability of two-dimensional wave fields and its concurrent evolution in time is here investigated by means of the Alber equation for narrow-banded random surface waves in deep water subject to inhomogeneous disturbances. The probability of freak waves in the context of these simulations is also discussed. The instability is first studied for the symmetric Lorentz spectrum, and continued for the realistic asymmetric Joint North Sea Wave Project (JONSWAP) spectrum of ocean waves with variable directional spreading and steepness. It is found that instability depends on the directional spreading and parameters $\\alpha $ and $\\gamma $ of the JONSWAP spectrum, where $\\alpha $ and $\\gamma $ are the energy scale and the peak enhancement factor, respectively. Both influence the mean steepness of waves with such a spectrum, although in different ways. Specifically, if the instability stops as a result of the directional spreading, increase of the steepness by increasing $\\alpha $ or $\\gamma $ can reactivate it. A criterion for the instability is suggested as a dimensionless ‘width parameter’, $\\Pi $ . For the unstable conditions, long-time evolution is simulated by integrating the Alber equation numerically. Recurrent evolution is obtained, which is a stochastic counterpart of the Fermi–Pasta–Ulam recurrence obtained for the cubic Schrödinger equation. This recurrence enables us to study the probability of freak waves, and the results are compared to the values given by the Rayleigh distribution. Moreover, it is found that stability–instability transition, the most unstable mode, recurrence duration and freak wave probability depend solely on the dimensionless ‘width parameter’, $\\Pi $ .
On the probability of occurrence of rogue waves
Publisher: Copernicus GmbH
Date: 23-03-2012
DOI: 10.5194/NHESS-12-751-2012
Abstract: Abstract. A number of extreme and rogue wave studies have been conducted theoretically, numerically, experimentally and based on field data in the last years, which have significantly advanced our knowledge of ocean waves. So far, however, consensus on the probability of occurrence of rogue waves has not been achieved. The present investigation is addressing this topic from the perspective of design needs. Probability of occurrence of extreme and rogue wave crests in deep water is here discussed based on higher order time simulations, experiments and hindcast data. Focus is given to occurrence of rogue waves in high sea states.
High-resolution thermal imaging in the Antarctic marginal ice zone: Skin temperature heterogeneity and effects on heat fluxes
Publisher: Authorea, Inc.
Date: 25-05-2023
DOI: 10.22541/ESSOAR.168500257.79644507/V1
Abstract: Insufficient in-situ observations from the Antarctic marginal ice zone limit our understanding and description of relevant mechanical and thermodynamic processes that regulate the seasonal sea ice cycle. Here we present high-resolution thermal images of the ocean surface and complementary measurements of atmospheric variables that were acquired underway during one austral winter and one austral spring expedition in the Atlantic and Indian sectors of the Southern Ocean. Skin temperature data and ice cover images were used to estimate the partitioning of the heterogeneous surface and calculate the heat fluxes to compare with ERA5 reanalyses. The winter marginal ice zone was composed of different but relatively regularly distributed sea ice types with sharp thermal gradients. The surface-weighted skin temperature compared well with the reanalyses due to a compensation of errors between the sea ice fraction and the ice floe temperature. These uncertainties determine the dominant source of inaccuracy for heat fluxes as computed from observed variables. In spring, the sea ice type distribution was more irregular, with alternation of sea ice cover and large open water fractions even 400 km from the ice edge. The skin temperature distribution was more homogeneous and did not produce substantial uncertainties in heat fluxes. The discrepancies relative to reanalysis data are however larger than in winter and are attributed to biases in the atmospheric variables, with the downward solar radiation being the most critical.
Surface gravity waves from direct numerical simulations of the Euler equations: A comparison with second-order theory
Publisher: Elsevier BV
Date: 03-2008
Experimental and theoretical models of wave-induced flexure of a sea ice floe
Publisher: AIP Publishing
Date: 04-2015
DOI: 10.1063/1.4916573
Abstract: An experimental model is used to validate a theoretical model of a sea ice floe’s flexural motion, induced by ocean waves. A thin plastic plate models the ice floe in the experiments. Rigid and compliant plastics and two different thicknesses are tested. Regular incident waves are used, with wavelengths less than, equal to, and greater than the floe length, and steepnesses ranging from gently sloping to storm-like. Results show the models agree well, despite the overwash phenomenon occurring in the experiments, which the theoretical model neglects.
On the variability of sea drag in finite water depth
Publisher: American Geophysical Union (AGU)
Date: 26-07-2012
DOI: 10.1029/2011JC007857
On the Use of a Domain Decomposition Strategy in Obtaining Response Statistics in Non-Gaussian Seas
Publisher: MDPI AG
Date: 07-01-2021
Abstract: During recent years, thorough experimental and numerical investigations have led to an improved understanding of dynamic phenomena affecting the fatigue life and survivability of offshore structures, e.g., ringing and springing and extreme wave impacts. However, most of these efforts have focused on modeling either selected extreme events or sequences of highly nonlinear waves impacting offshore structures, possibly overestimating the actual load to be experienced by the structure. Overall, not much has been done regarding short-term statistics. Although clear non-Gaussian statistics and therefore higher probabilities of extreme waves have been observed in random seas due to wave–wave interaction phenomena, which can impact short-term statistics for the structural load, they have not been studied extensively regarding the assessment of the dynamic behavior of offshore structures. Computational fluid dynamics (CFD) models have shown their viability for studying wave–structure interaction phenomena. Despite the continuously increasing computational resources, these models remain too computationally demanding for applications to the large spatial domains and long periods of time necessary for studying short-term statistics of non-Gaussian seas. Higher-order spectral (HOS) models, on the other hand, have been proven to be efficient and adequate in studying non-Gaussian seas. We therefore propose a one-way domain decomposition strategy, which takes full advantage of the recent advances in CFD and of the computational benefits of HOS. When applying this domain decomposition strategy, it appeared to be possible to deduce response statistics regarding the impact of nonlinear wave–wave interactions.
Uncertainties of wind sea and swell prediction from the Torsethaugen spectrum
Publisher: ASMEDC
Date: 2009
Abstract: In practical applications, it is usually assumed that the wave spectrum is of a single mode form, and well modelled by a JONSWAP or Pierson-Moskowitz spectrum. This assumption is of a reasonable accuracy for severe sea states. However, moderated and low sea states are often of a combined nature, consisting of both wind-sea and swell and should be characterized by a double peak spectrum. Bimodal seas can have a significant impact on the design and operability of fixed and floating offshore structures as well as LNG terminals. Although several separation procedures for the wave components exist the bimodal Torsethaugen spectrum is probably the only one well established in design work. This spectrum was developed primarily for one location at the Norwegian Continental Shelf (Statfjord Field) but in qualitative terms is expected to be of much broader validity. The present study discusses applicability of the Torsethaugen spectrum for locations outside the Norwegian Continental Shelf and uncertainties related to use of the spectrum.
Modulational instability and wave amplification in finite water depth
Publisher: Copernicus GmbH
Date: 27-03-2014
DOI: 10.5194/NHESS-14-705-2014
Abstract: Abstract. The modulational instability of a uniform wave train to side band perturbations is one of the most plausible mechanisms for the generation of rogue waves in deep water. In a condition of finite water depth, however, the interaction with the sea floor generates a wave-induced current that subtracts energy from the wave field and consequently attenuates the instability mechanism. As a result, a plane wave remains stable under the influence of collinear side bands for relative depths kh & leq 1.36 (where k is the wavenumber of the plane wave and h is the water depth), but it can still destabilise due to oblique perturbations. Using direct numerical simulations of the Euler equations, it is here demonstrated that oblique side bands are capable of triggering modulational instability and eventually leading to the formation of rogue waves also for kh & leq 1.36. Results, nonetheless, indicate that modulational instability cannot sustain a substantial wave growth for kh 0.8.
Ship resistance when operating in floating ice floes: A combined CFD&DEM approach
Publisher: Elsevier BV
Date: 11-2020
Brief communication: Pancake ice floe size distribution during the winter expansion of the Antarctic marginal ice zone
Publisher: Copernicus GmbH
Date: 08-2018
DOI: 10.5194/TC-2018-155
Abstract: Abstract. The size distribution of pancake ice floes is calculated from images acquired during a voyage to the Antarctic marginal ice zone in the winter expansion season. Results show that 50 % of the sea ice area is made up by floes with diameters 2.3–4 m. The floe size distribution shows two distinct slopes on either side of the 2.3–4 m range. It is conjectured that growth of pancakes from frazil forms the distribution of small floes (D 4 m).
Model Predictions of Wave Overwash Extent Into the Marginal Ice Zone
Publisher: American Geophysical Union (AGU)
Date: 30-09-2022
DOI: 10.1029/2022JC018707
Abstract: In the marginal ice zone (MIZ), where ocean waves and sea ice interact, waves can produce flows of water across ice floe surfaces in a process known as wave overwash. Overwash potentially influences wave propagation characteristics, floe thermodynamics, and floe surface biological and chemical processes. However, the extent of the MIZ affected by overwash and its dependence on prevailing wave and ice conditions is unknown. In this paper, we propose a model of overwash extent caused by irregular incoming waves into a MIZ consisting of a random floe field. We validate the overwash extent model against laboratory experiments. We use the model to study mild to extreme incoming waves to floe field characteristics of the spring–summer ice retreat and autumn–winter ice advance and with compact ice edges. Overwash is typically predicted to extend a few kilometers and is generally greater for the autumn–winter advance than the spring–summer retreat. The model predictions provide a basis for improved understanding of the impacts of ocean waves on the ice cover. We also apply the model to incoming waves and a floe field with a diffuse ice edge representative of conditions during a field experiment, predicting overwash extents up to 16 km. During the field experiment, the wave and ice floe properties were intermittently monitored by a camera system, demonstrating how the sparse field data available on overwash can be advanced.
Wind, waves, and surface currents in the Southern Ocean: Observations from the Antarctic Circumnavigation Expedition
Publisher: Copernicus GmbH
Date: 17-10-2020
Abstract: Abstract. The Southern Ocean has a profound impact on the Earth's climate system. Its strong winds, intense currents, and fierce waves are critical components of the air-sea interface and contribute to absorbing, storing, and releasing heat, moisture, gasses, and momentum. Owing to its remoteness and harsh environment, this region is significantly under s led, h ering the validation of prediction models and large scale observations from satellite sensors. Here, an unprecedented data set of simultaneous observations of winds, surface currents, and ocean waves is presented, to address the scarcity of in situ observations in the region – 0.26179/5ed0a30aaf764 (Alberello et al., 2020c), and 0.26179/5e9d038c396f2 (Derkani et al., 2020). Records were acquired underway during the Antarctic Circumnavigation Expedition (ACE), which went around the Southern Ocean from December 2016 to March 2017 (Austral summer). Observations were obtained with the wave and surface current monitoring system WaMoS-II, which scanned the ocean surface around the vessel using marine radars. Measurements were assessed for quality control and compared against available satellite observations. The data set is the most extensive and comprehensive collection of observations of surface process for the Southern Ocean and has the potential to support further theoretical and numerical research on lower atmosphere, air-sea interface and upper ocean processes.
Freak waves in crossing seas
Publisher: Springer Science and Business Media LLC
Date: 07-2010
Interactions between irregular wave fields and sea ice: A physical model for wave attenuation and ice breakup in an ice tank
Publisher: American Meteorological Society
Date: 07-2022
Abstract: Irregular, unidirectional surface water waves incident on model ice in an ice tank are used as a physical model of ocean surface wave interactions with sea ice. Results are given for an experiment consisting of three tests, starting with a continuous ice cover and in which the incident wave steepness increases between tests. The incident waves range from causing no breakup of the ice cover to breakup of the full length of ice cover. Temporal evolution of the ice edge, breaking front, and mean floe sizes are reported. Floe size distributions in the different tests are analyzed. The evolution of the wave spectrum with distance into the ice-covered water is analyzed in terms of changes of energy content, mean wave period, and spectral bandwidth relative to their incident counterparts, and pronounced differences are found between the tests. Further, an empirical attenuation coefficient is derived from the measurements and shown to have a power-law dependence on frequency comparable to that found in field measurements. Links between wave properties and ice breakup are discussed.
Modeling the spatial evolutions of nonlinear unidirectional surface gravity waves with fully nonlinear numerical method
Publisher: Elsevier BV
Date: 10-2016
Modelling attenuation of irregular wave fields by artificial ice floes in the laboratory
Publisher: The Royal Society
Date: 12-09-2022
Abstract: A summary is given on the utility of laboratory experiments for gaining understanding of wave attenuation in the marginal ice zone, as a complement to field observations, theory and numerical models. It is noted that most results to date are for regular incident waves, which, combined with the highly nonlinear wave–floe interaction phenomena observed and measured during experimental tests, implies that the attenuation of regular waves cannot necessarily be used to infer the attenuation of irregular waves. Two experiments are revisited in which irregular wave tests were conducted but not previously reported, one involving a single floe and the other a large number of floes, and the transmission coefficients for the irregular and regular wave tests are compared. The transmission spectra derived from the irregular wave tests agree with the regular wave data but are overpredicted by linear models due to nonlinear dissipative processes, regardless of floe configuration. This article is part of the theme issue ‘Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks’.
Modified and unmodified low-cost iron-containing solid wastes as adsorbents for efficient removal of As(III) and As(V) from mine water
Publisher: Elsevier BV
Date: 10-2016
Excitation of rogue waves in a variable medium: An experimental study on the interaction of water waves and currents
Publisher: American Physical Society (APS)
Date: 29-05-2013
Influence of location and instrumentation on wave group characteristics
Publisher: ASMEDC
Date: 2008
Abstract: Wave group characteristics from water of intermediate depths ranging from relatively deep to relatively shallow are discussed. The analysis is based on measurements of the surface elevation, which were collected with both floating and fixed sensors. Results indicate that, for similar spectral conditions, the general distributions of the run lengths are remarkably similar for the waves in the relatively deep and relatively shallow water depths. However, for less steep sea states, it has been observed that the group tendency is more pronounced for the deeper water location due to more relevant swell activities. The analysis of the fixed sensor data gives measured run lengths that are shorter than the ones obtained from wave buoys. For both locations, the empirical findings agree relatively well with probabilistic predictions using the approach given in [1] where a correlation parameter κ is estimated using spectral shape parameters.
Wave statistics in unimodal and bimodal seas from a second-order model
Publisher: Elsevier BV
Date: 04-2016
Sea ice floes dissipate the energy of steep ocean waves
Publisher: American Geophysical Union (AGU)
Date: 25-10-2015
DOI: 10.1002/2015GL065937
The effect of wave-induced turbulence on the ocean mixed layer during tropical cyclones: Field observations on the Australian North-West Shelf
Publisher: American Geophysical Union (AGU)
Date: 20-07-2012
DOI: 10.1029/2011JC007780
Attachment of Poly(l
-lactide) Nanoparticles to Plasma-Treated Non-Woven Polymer Fabrics Using Inkjet Printing
Publisher: Wiley
Date: 27-05-2015
Abstract: Active dressings that based on fabric materials are an area of interest for the treatment of wounds. Poly(l-lactide) nanoparticles containing the antimicrobial agent octenidine can be controllably lysed by toxins released by pathogenic bacteria thus releasing antimicrobial material in response to the presence of the bacterial toxins and so counteracting the infection. We developed an integrated engineering solution that allows for the stable immobilisation of nanoparticles on non-woven fabrics. The process involves coating nanoparticles on non-woven polymer surfaces by using an inkjet printing process. In order to improve the adhesion and retention of the nanoparticles on the fabric, surface pretreatment of the non-woven fabric using plasma jet treatment can be applied to increase its surface energy.
Wave Breaking in Directional Fields
Publisher: American Meteorological Society
Date: 2011
Abstract: Wave breaking is observed in a laboratory experiment with waves of realistic average steepness and directional spread. It is shown that a modulational-instability mechanism is active in such circumstances and can lead to the breaking. Experiments were conducted in the directional wave tank of the University of Tokyo, and the mechanically generated wave fields consisted of a primary wave with sidebands in the frequency domain, with continuous directional distribution in the angular domain. Initial steepness of the primary wave and sidebands, as well as the width of directional distributions varied in a broad range to determine the combination of steepness/directional-spread properties that separates modulational-instability breaking from the linear-focusing breaking.
Wave turbulence and intermittency in directional wave fields
Publisher: Elsevier BV
Date: 12-2018
Non-Gaussian Properties of Shallow Water Waves in Crossing Seas
Publisher: Springer Netherlands
Date: 2008
CSI – Cuttlefish Sepion Investigation: overview of cuttlebones found on Aotearoa New Zealand shores and analysis of predation and scavenging marks
Publisher: Informa UK Limited
Date: 17-11-2023
Estimating Sea Spray Volume with a Laser Altimeter
Publisher: American Meteorological Society
Date: 09-2011
Abstract: Down-looking laser altimeters are commonly used to measure the sea surface elevation. However, because the laser radiation is attenuated by spray droplets suspended along the transmission path, it is presumed that altimeters may also provide an indirect measure of the sea spray volume. Here, this conjecture is discussed by means of laboratory experiments, which have been conducted in a wind-wave flume. A large number of wind conditions were considered between equivalent 10-m wind speeds of 20 and 60 m s−1 in order to generate different spray volumes above the water surface. The facility was equipped with a laser and side-looking camera system to estimate the spray volume as well as a nearby down-looking laser altimeter. Results confirm that there is a robust degradation of the laser intensity for increasing wind speed and hence the amount of spray droplets above the water surface. A simple regression model to extract spray volume from the average intensity of the laser radiation is presented, demonstrating the promise of laser altimeters for making in situ spray observations. Additional observations will be required to calibrate the altimeters for applications in the open ocean marine environment.
Acid mine drainage (AMD) treatment: Neutralization and toxic elements removal with unmodified and modified limestone
Publisher: Elsevier BV
Date: 08-2015
Robust fast nonsingular terminal sliding mode control strategy for electronic throttle based on extreme learning machine
Publisher: IEEE
Date: 07-2019
High-resolution thermal imaging in the Antarctic Marginal Ice Zone: Skin temperature heterogeneity and effects on heat fluxes
Publisher: American Geophysical Union (AGU)
Date: 09-2023
DOI: 10.1029/2023EA003078
New Directional Wave Satellite Observations: Towards Improved Wave Forecasts and Climate Description in Southern Ocean
Publisher: American Geophysical Union (AGU)
Date: 03-2021
DOI: 10.1029/2020GL091187
Abstract: In spite of continuous improvements of ocean wave models in the last decades, large errors still remain in particular under strongly forced conditions, often encountered in the Southern Ocean, where strong westerly winds generate some of the fiercest waves on Earth in almost unlimited fetch conditions. The newly launched China‐France Oceanography SATellite (CFOSAT) provides directional spectra of ocean waves for both wind seas and swells. Compared to Synthetic Aperture Radar (SAR), it can resolve shorter wavelengths in all directions, which dominate in non‐fully developed wind waves. Here, the assimilation of these CFOSAT wavenumber components is proved to bring more accurate predictions of wave growth compared to the assimilation of significant wave height alone. A notable reduction of model bias is found in the Southern Ocean, especially in the Pacific Ocean sector. Results further exhibit a downward shift of the wave age, consistent with theoretical wave growth curves.
Occurrence of rogue sea states and consequences for marine structures
Publisher: Springer Science and Business Media LLC
Date: 22-08-2014
Modulational instability and rogue waves in finite water depth
Publisher: Copernicus GmbH
Date: 02-10-2013
DOI: 10.5194/NHESSD-1-5237-2013
Abstract: Abstract. The mechanism of side band perturbations to a uniform wave train is known to produce modulational instability and in deep water conditions it is accepted as a plausible cause for rogue wave formation. In a condition of finite water depth, however, the interaction with the sea floor generates a wave-induced current that subtracts energy from the wave field and consequently attenuates this instability mechanism. As a result, a plane wave remains stable under the influence of collinear side bands for relative water depths kh & leq 1.36 (where k represents the wavenumber of the plane wave and h the water depth), but it can still destabilise due to oblique perturbations. Using direct numerical simulations of the Euler equations, it is here demonstrated that oblique side bands are capable of triggering modulational instability and eventually leading to the formation of rogue waves also for kh & leq 1.36. Results, nonetheless, indicates that modulational instability cannot sustain a substantial wave growth for kh 0.8.
Extreme waves in random crossing seas: Laboratory experiments and numerical simulations
Publisher: American Geophysical Union (AGU)
Date: 03-2011
DOI: 10.1029/2011GL046827
Occurrence of extreme waves in three-dimensional mechanically generated wave fields propagating over an oblique current
Publisher: Copernicus GmbH
Date: 22-03-2011
DOI: 10.5194/NHESS-11-895-2011
Abstract: Abstract. Laboratory experiments were performed to study the dynamics of three- dimensional mechanically generated waves propagating over an oblique current in partial opposition. The flow velocity varied along the mean wave direction of propagation with an increasing trend between the wave-maker and the centre of the tank. Tests with regular wave packets traversing the area of positive current gradient showed that the concurrent increase of wave steepness triggered modulational instability on otherwise stable wave trains and hence induced the development of very large litude waves. In random directional wave fields, the presence of the oblique current resulted in a weak reinforcement of wave instability with a subsequent increase of the probability of occurrence of extreme events. This seems to partially compensate the suppression of strongly non-Gaussian properties due to directional energy distribution.
Triggering Rogue Waves in Opposing Currents
Publisher: American Physical Society (APS)
Date: 26-10-2011
Reflection and transmission of regular water waves by a thin, floating plate
Publisher: Elsevier BV
Date: 04-2017
A semi-empirical wave crest distribution of random directional wave fields
Publisher: American Society of Mechanical Engineers
Date: 07-2012
Abstract: Laboratory data of random directional wave fields have been used to investigate the combined effect of higher order nonlinearity and directional spreading on the wave crest distribution. Different sea states with a variety of combination of steepness and directional spreading have been considered, ranging from long to short crested wave fields. The analysis is also supported by numerical simulations. A 2-parameter Weibull distribution has been fitted to the experimental data and the related parameters have been parameterized as a function of a general version of the Benjamin-Feir Index for directional sea states recently presented by Mori et al. [1]. Long-term distributions of the one-dimensional and two-dimensional Benjamin-Feir Index have been studied based on the hindcast data from the North Atlantic and probabilistic models to describe them are proposed.
A Computational Fluid Dynamics Model for the Small-Scale Dynamics of Wave, Ice Floe and Interstitial Grease Ice Interaction
Publisher: MDPI AG
Date: 29-04-2021
Abstract: The marginal ice zone is a highly dynamical region where sea ice and ocean waves interact. Large-scale sea ice models only compute domain-averaged responses. As the majority of the marginal ice zone consists of mobile ice floes surrounded by grease ice, finer-scale modelling is needed to resolve variations of its mechanical properties, wave-induced pressure gradients and drag forces acting on the ice floes. A novel computational fluid dynamics approach is presented that considers the heterogeneous sea ice material composition and accounts for the wave-ice interaction dynamics. Results show, after comparing three realistic sea ice layouts with similar concentration and floe diameter, that the discrepancy between the domain-averaged temporal stress and strain rate evolutions increases for decreasing wave period. Furthermore, strain rate and viscosity are mostly affected by the variability of ice floe shape and diameter.
Wind, waves, and surface currents in the Southern Ocean: Observations from the Antarctic Circumnavigation Expedition
Publisher: Copernicus GmbH
Date: 22-03-2021
DOI: 10.5194/ESSD-13-1189-2021
Abstract: Abstract. The Southern Ocean has a profound impact on the Earth's climate system. Its strong winds, intense currents, and fierce waves are critical components of the air–sea interface and contribute to absorbing, storing, and releasing heat, moisture, gases, and momentum. Owing to its remoteness and harsh environment, this region is significantly unders led, h ering the validation of prediction models and large-scale observations from satellite sensors. Here, an unprecedented data set of simultaneous observations of winds, surface currents, and ocean waves is presented, to address the scarcity of in situ observations in the region – 0.26179/5ed0a30aaf764 (Alberello et al., 2020c) and 0.26179/5e9d038c396f2 (Derkani et al., 2020). Records were acquired underway during the Antarctic Circumnavigation Expedition (ACE), which went around the Southern Ocean from December 2016 to March 2017 (Austral summer). Observations were obtained with the wave and surface current monitoring system WaMoS-II, which scanned the ocean surface around the vessel using marine radars. Measurements were assessed for quality control and compared against available satellite observations. The data set is the most extensive and comprehensive collection of observations of surface processes for the Southern Ocean and is intended to underpin improvements of wave prediction models around Antarctica and research of air–sea interaction processes, including gas exchange and dynamics of sea spray aerosol particles. The data set has further potentials to support theoretical and numerical research on lower atmosphere, air–sea interface, and upper-ocean processes.
Modelling water wave overwash of a thin floating plate
Publisher: Cambridge University Press (CUP)
Date: 20-07-2015
DOI: 10.1017/JFM.2015.378
Abstract: A theoretical model of water wave overwash of a thin floating plate is proposed. The nonlinear shallow-water equations are used to model the overwash, and the linear potential-flow/thin-plate model to force it. Model predictions are compared with overwash depths measured during a series of laboratory wave basin experiments. The model is shown to be accurate for incident waves of low steepness or short length.
Experimental evidence of the modulation of a plane wave to oblique perturbations and generation of rogue waves in finite water depth
Publisher: AIP Publishing
Date: 09-2013
DOI: 10.1063/1.4821810
Abstract: We present a laboratory experiment in a large directional wave basin to discuss the instability of a plane wave to oblique side band perturbations in finite water depth. Experimental observations, with the support of numerical simulations, confirm that a carrier wave becomes modulationally unstable even for relative water depths k0h & 1.36 (with k the wavenumber of the plane wave and h the water depth), when it is perturbed by appropriate oblique disturbances. Results corroborate that the underlying mechanism is still a plausible explanation for the generation of rogue waves in finite water depth.
Third-order resonant wave interactions under the influence of background current fields
Publisher: Cambridge University Press (CUP)
Date: 29-10-2015
DOI: 10.1017/JFM.2015.578
Abstract: A series of experiments were conducted in a wave basin (50 m long, 10 m wide and 5 m deep) generating two waves propagating at an angle by a directional wavemaker. When the two waves were selected from a resonant triplet, an initially non-existing wave grew as the waves propagated down the tank. The linear growth rate of the resonating wave agreed well with third-order resonance theory based on Zakharov’s reduced gravity equation. Additional experiments with opposing and coflowing mean current with large temporal and spatial variations were conducted. As the flow rate increased, the linear growth was suppressed. As reproduced numerically with Zakharov’s equation, the resonant interaction saturated at time scales inversely proportional to the magnitude of the forced random resonance detuning. It is conjectured that the resonance is detuned by the variation and not by the mean of the current field due to wavelength-dependent Doppler shift and to the refraction of wave rays. Further analysis of the spectral evolution revealed that while discrete peaks appear at high frequencies as a result of dynamical cascading, a continuously saturated spectrum develops in the background as the current speed increases. Additional experiments were conducted studying the evolution of the random directional wave on a dynamical time scale under the influence of current. Due to random resonance detuning by the current, the spectral tail tended to be suppressed.
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