Alessandro Toffoli

University of Melbourne | MSD · Department of Infrastructure Engineering

The size and shape of sea ice floes play a crucial role in influencing ocean-atmosphere energy exchanges, sea ice concentrations, albedo, and wave propagation through ice-covered waters. Despite the availability of diverse image segmentation techniques for analyzing sea ice imagery, accurately detecting and measuring floes remains a considerable ch...

Sea spray emission is the largest mass flux of aerosols to the atmosphere with important impact on atmospheric radiative transfer. However, large uncertainties still exit in constraining this mass flux and its climate forcing, in particular in the Arctic, where sea ice and relatively low wind speed in summer constitute a significantly different reg...

Plain Language Summary The United Nations has identified 2021–2030 as the Decade of Ocean Science, with a goal to improve predictions of ocean and climate change. Improved understanding of the Southern Ocean is crucial to this effort, as it is the central hub of the global ocean. The Southern Ocean is the formation site for much of the dense water...

We report direct observations of surface waves from a stereo camera system along with concurrent measurements of wind speed during an expedition across the Southern Ocean in the austral winter aboard the South African icebreaker S.A. Agulhas II. Records include water surface elevation across a range of wave conditions spanning from early stages of...

A holistic review is given of the Southern Ocean dynamic system, in the context of the crucial role it plays in the global climate and the profound changes it is experiencing. The review focuses on connections between different components of the Southern Ocean dynamic system, drawing together contemporary perspectives from different research commun...

Two ensembles of buoys, deployed in the marginal ice zone (MIZ) of the north-eastern Weddell Sea region of the Southern Ocean, are analysed to characterise the dynamics driving sea ice drift and deformation during the winter-growth and the spring-retreat seasons of 2019. The results show that although the two buoy arrays were deployed within the sa...

We report unique direct observations of surface waves from a stereo camera system aboard the South African icebreaker S.A. Agulhas II during an expedition across the Southern Ocean in the austral winter. Records include water surface elevation across a range of wave conditions, spanning from early stages of wave growth to full development. We give...

The Coastal & Ocean Basin (COB) is a brand-new wave-current basin in Ostend (Belgium). The basin is 30m long and 30m wide, and it is equipped with modular wavemakers on two adjacent sides. This allows generation of multi-modal seas (including the so-called crossing-sea states). A system of multiple pumps will also be installed to allow generation o...

Insufficient in situ observations from the Antarctic marginal ice zone (MIZ) 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 acquir...

A holistic review is given of the Southern Ocean dynamic system, in the context of the crucial role it plays in the global climate and the profound changes it is experiencing. The review focuses on connections between different components of the Southern Ocean dynamic system, drawing together contemporary perspectives from different research commun...

Two ensembles of buoys, deployed in the north-eastern Weddell Sea region of the Southern Ocean, are analysed to characterise the dynamics driving sea ice drift and deformation during the winter-growth and the spring-retreat seasons of 2019. The results show that although the two buoy arrays were deployed within the same region of ice-covered ocean,...

The Southern Ocean stores and release more heat than any other latitude band on the planet, making it a major element of the global climate. In the Antarctic, air-sea heat exchange is mediated by the seasonal sea ice cycle, which forms an unsteady and composite interface. In-situ measurements are serendipitous in the region and models are poorly co...

Estimates of directional wave spectra and related parameters can be obtained from ship motion data through the wave-buoy analogy approach. The fundamental input is the response amplitude operator (RAO), which translates ship response into a wave energy spectrum. While ship motion is routinely measured on ocean going vessels, the RAO is not directly...

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 o...

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 observ...

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 campaigns have generated much needed measurements of wave evolution in...

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 model of the extent of overwash into fields of sea ice is developed. The extent model builds on previous work modelling overwash of a single floe by regular waves to include irregular waves and many random floes. The extent model is validated against laboratory experiments. The model is used to study the the extent of overwash into fields of panc...

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 rang...

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 corr...

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 rang...

Supplementary Information to Landwehr, S., Volpi, M., Haumann, F. A., Robinson, C. M., Thurnherr, I., Ferracci, V., Baccarini, A., Thomas, J., Gorodetskaya, I., Tatzelt, C., Henning, S., Modini, R. L., Forrer, H. J., Lin, Y., Cassar, N., Simó, R., Hassler, C., Moallemi, A., Fawcett, S. E., Harris, N., Airs, R., Derkani, M. H., Alberello, A., Toffol...

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 scale to the large scale. As a result, our knowledge of this vast region remains largely incomplete. The Antarctic Circumnavigation Expedition (ACE, austral summer 2016/201...

A physical model is discussed that mimics the interaction between ocean waves and a multitude of loose pancake ice floes, which form the outer edge of the Arctic and Antarctic marginal ice zones during winter sea ice formation. The pancakes were modeled by using ice cubes with different concentrations, while waves were generated mechanically. The i...

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 ref...

Sea state conditions can be estimated from the motion of a moving ship by converting its response to incident waves through the response amplitude operator. The method is applied herein to ship motion data from the icebreaker R/V Akademik Tryosh-nikov and recorded during the Antarctic Circumnavigation Expedition across the Southern Ocean during the...

We discuss the dynamics of undirectional random wave fields that propagate against an opposing current through laboratory experiments and direct numerical simulations of the Euler equations solved with a High-Order Spectral method. Both approaches demonstrate that the presence of a negative horizontal velocity gradient increases the probability of...

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...

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) sur...

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...

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 undersample...

Propagation of energetic surface gravity waves over a $>40$\,km transect of the winter Antarctic marginal ice zone comprised of pancake floes and interstitial frazil ice during an explosive polar cyclone are presented, obtained with a shipborne stereo-camera system. The waves are shown to attenuate at an exponential rate over distance, but, despite...

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 sequen...

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 samp...

Ocean waves penetrate hundreds of kilometres into the ice- covered ocean. Waves fracture the level ice into small floes, herd floes, introduce warm water and overwash the floes, accelerating ice melt and causing collisions, which concurrently erodes the floes and influences the large-scale deformation. Concomitantly, interactions between waves and...

Although wave-wave interaction phenomena in random seas have shown to lead to a departure from Gaussian statistics and therefore to a higher occurrence of extreme waves, they are usually not taken along in the assessment of the dynamic behaviour of offshore structures. Supported by a rapid increase of computational resources, the use of Computation...

Model ice testing is the state of the art validation and testing method for ships and structures interacting with ice. Its initial design objective was the prediction of resistance forces of ice breaking ships by using Froude and Cauchy similitude to account to the most significant force ratios. In the ice breaking process the forces due to downwar...

Whilst climate change is transforming the Arctic into a navigable ocean where small ice floes are floating on the sea surface, the effect of such ice conditions on ship performance has yet to be understood. The present work combines a set of numerical methods to simulate the ship-wave-ice interaction in such ice conditions. Particularly, Computatio...

We examine and discuss the spatial evolution of the statistical properties of mechanically generated surface gravity wave fields, initialized with unidirectional spectral energy distributions, uniformly distributed phases, and Rayleigh distributed amplitudes. We demonstrate that nonlinear interactions produce an energy cascade towards high frequenc...

Over recent decades, the Arctic Ocean has experienced dramatic changes due to climate change. Retreating sea ice has opened up large areas of ocean, resulting in an enhanced wave climate. Taking into account the intense seasonality and the rapid changes to the Arctic climate, a non-stationary approach is applied to time-varying statistical properti...

The Australian marine research, industry, and stakeholder community has recently undertaken an extensive collaborative process to identify the highest national priorities for windwaves 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, sol...

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 pro...

Water wave transmission and energy dissipation by a floating plate in the presence of overwash - Volume 889 - Filippo Nelli, Luke G. Bennetts, David M. Skene, Alessandro Toffoli

Plain Language Summary During the Antarctic winter, small pancake ice floes, which form rapidly in wavy conditions, dominate new ice growth and create a dynamic environment. However, there are only a handful of local observations of pancake ice drift, particularly during the intense polar cyclones that frequently reshape the ice cover. More observa...

We examine and discuss the spatial evolution of the statistical properties of mechanically generated wave fields, initialised with uniformly distributed phases and Rayleigh distributed amplitudes. We demonstrate that nonlinear interactions produce an energy cascade towards high frequency modes and triggers localised intermittent bursts. By analysin...

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 S...

A case study is here presented to investigate the response of local wave climate to the deepening of the navigational channel at the southern area of Port Phillip Bay.

Inhomogeneous media can change the nonlinear properties of waves propagating on them. In the ocean, this phenomenon can be observed when waves travel on a surface current. In the case of negative horizontal velocity gradients (i.e. an accelerating opposing current or a decelerating following current), waves shorten and heighten, enhancing wave stee...

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 time scales from large-scale moisture transport to cloud formation, precipitation, and small-scale turbulent mixing. Laser spectrometric measurements on research vessels p...

Whilst climate change is transforming the Arctic into a navigable ocean where small ice floes are floating on the sea surface, the effect of such ice conditions on ship performance has yet to be understood. The present work combines a set of numerical methods to simulate the ship-wave-ice interaction in such ice conditions. Particularly, Computatio...

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 anthr...

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 nine days in which the region was impacted by four polar cyclones. Concomitant measurements of wave-in-ice activity from the buoys is used to infer tha...

Plain Language Summary The extent of Antarctic sea ice is characterized by large regional variations that are in stark contrast with the alarming decreasing trends found in the Arctic. This is partly due to the presence of severe weather events, like extratropical cyclones travelling through the Southern Ocean and reaching the marginal ice zone (MI...

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, so...

Significance 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 wa...

With the increasing demand for Arctic Engineering purposes, Squire suggests current theories may have oversimplified the sea ice hydroelasticity, indicating the need to develop numerical models to obtain more realistic solutions. Numerical models have been reported capable of achieving a full coupling between waves and rigid floating ice. When an i...