Alison L. Kohout

• National Institute of Water and Atmospheric Research, Christchurch, New Zealand

The marginal ice zone (MIZ) is the dynamic interface between the open ocean and sea ice-covered ocean. It is characterized by interactions between surface gravity waves and granular ice covers consisting of relatively small, thin chunks of sea ice known as floes. This structure gives the MIZ markedly different properties to the thicker, quasi-conti...

Perspectives are discussed on future directions for the field of marginal ice zone (MIZ) dynamics, based on the extraordinary progress made over the past decade in its theory, modelling and observations. Research themes are proposed that would shift the field’s focus towards the broader implications of MIZ dynamics in the climate system. In particu...

The Antarctic marginal ice zone (MIZ) is a highly dynamic region where sea ice interacts with ocean surface waves generated in ice-free areas of the Southern Ocean. Improved large-scale (satellite-based) estimates of MIZ extent and variability are crucial for understanding atmosphere–ice–ocean interactions and biological processes and detection of...

Despite a recent resurgence of observational studies attempting to quantify the ice-induced attenuation of ocean waves in polar oceans, the physical processes governing this phenomenon are still poorly understood. Most analyses have attempted to relate the spatial rate of wave attenuation to wave frequency, but have not considered how this relation...

The Antarctic marginal ice zone (MIZ) is a highly dynamic region where sea ice interacts with ocean surface waves generated in ice-free areas of the Southern Ocean. Improved large-scale (satellite-based) estimates of MIZ width and variability are crucial for understanding atmosphere-ice-ocean interactions and biological processes, and detection of...

Despite a recent resurgence of observational studies attempting to quantify the ice-induced attenuation of ocean waves in polar oceans, the physical processes governing this wave attenuation phenomenon are still poorly understood. Most analyses have attempted to relate the spatial rate of wave attenuation to wave frequency, but have not considered...

The effects of instrument noise on estimating the spectral attenuation rates of ocean waves in sea ice are explored using synthetic observations in which the true attenuation rates are known explicitly. The spectral shape of the energy added by noise, relative to the spectral shape of the true wave energy, is the critical aspect of the investigatio...

A model-data inversion is applied to an extensive observational dataset collected in the Southern Ocean north of the Ross Sea during late autumn to early winter, producing estimates of the frequency-dependent rate of dissipation by sea ice. The modeling platform is WAVEWATCH III® which accounts for non-stationarity, advection, wave generation, and...

Quantifying the rate of wave attenuation in sea ice is key to understanding trends in the Antarctic marginal ice zone extent. However, a paucity of observations of waves in sea ice limits progress on this front. We deployed 14 waves-in-ice observation systems (WIIOS) on Antarctic sea ice during the Polynyas, Ice Production, and seasonal Evolution i...

A model-data inversion is applied to a very large observational dataset collected in the Southern Ocean north of the Ross Sea during late autumn to early winter, producing estimates of the frequency-dependent rate of dissipation by sea ice. The modeling platform is WAVEWATCH III (R) which accounts for non-stationarity, advection, wave generation, a...

Southern Ocean waves are the largest on Earth, but their interaction with sea ice is a particularly poorly understood feedback in the climate system. Limited observations of waves in the Antarctic marginal ice zone (MIZ) show that waves can travel hundreds of kilometers into the ice and that current representations of wave decay are inappropriate i...

A storm with significant wave heights exceeding 4 m occurred in the Beaufort Sea on 11-13 October 2015. The waves and ice were captured on 12 October by the Synthetic Aperture Radar (SAR) on board Sentinel-1A, with Interferometric Wide swath images covering 400 × 1,100 km at 10 m resolution. This data set allows the estimation of wave spectra acros...

Many processes that affect ocean surface gravity waves in sea ice give rise to attenuation rates that vary with both wave frequency and amplitude. Here we particularly test the possible effects of basal friction, scattering by ice floes, and dissipation in the ice layer due to dislocations, and ice break-up by the waves. The possible influence of t...

Many processes that affect ocean surface gravity waves in sea ice give rise to attenuation rates that vary with both wave frequency and amplitude. Here we particularly test the possible effects of basal friction, scattering by ice floes, and dissipation in the ice layer due to dislocations, and ice break‐up by the waves. The possible influence of t...

The long-term trend of extreme ocean waves in the emerging ice-free waters of the summer Arctic is studied using ERA-Interim wave reanalysis, with validation by two drifting wave buoys deployed in summer 2016. The 38-year-long reanalysis dataset reveals an increase in the expected largest significant wave height from 2.3 m to 3.1 m in the ice-free...

Many processes that affect ocean surface gravity waves in sea ice give rise to attenuation rates that vary with both wave frequency and amplitude. Here we particularly test the possible effects of basal friction, scattering by ice floes, and dissipation in the ice layer due to dislocations, and ice breakup by the waves. The possible influence of th...

Wave attenuation from two field experiments in the ice-covered Southern Ocean is examined. Instead of monotonically increasing with shorter waves, the measured apparent attenuation rate peaks at an intermediate wave period. This “rollover” phenomenon has been postulated as the result of wind input and nonlinear energy transfer between wave frequenc...

This paper presents a wave-in-ice model calibration study. Data used were collected in the thin ice of the advancing autumn marginal ice zone of the western Arctic Ocean in 2015, where pancake ice was found to be prevalent. Multiple buoys were deployed in seven wave experiments; data from four of these experiments are used in the present study. Wav...

“Sea State and Boundary Layer Physics in the Emerging Arctic Ocean” is an ongoing Departmental Research Initiative sponsored by the Office of Naval Research. The field component took place in the fall of 2015 within the Beaufort and Chukchi Seas and involved the deployment of a number of wave instruments including a downward looking Riegl laser ran...

To understand the behavior of the Seasonal Ice Zone (SIZ), which is composed of sea-ice floes of various sizes, knowledge of the floe size distribution (FSD) is important. In particular, FSD in the Marginal Ice Zone (MIZ), controlled by wave–ice interaction, plays an important role in determining the retreating rates of sea-ice extent on a global s...

Motivated by a dramatic reduction in Arctic sea ice cover, interest in the field of wave-ice interaction has accelerated over the past few years. Recent observations have identified that large waves (>3 m) have a linear attenuation rate, rather than the previously assumed exponential rate that is found for small waves. This suggests that waves pene...

Ocean waves can propagate hundreds of kilometers into sea ice, leaving behind a wake of broken ice floes. Three floe breakup events were observed during the second Sea Ice Physics and Ecosystem Experiment (SIPEX-2). We show that the three breakup events were likely influenced by ocean waves. We compare the observations to a wave induced floe breaku...

A series of wave instruments was deployed on first-year Antarctic sea ice during SIPEX (Sea Ice Physics and Ecosystem Experiment) II. Here we describe the hardware and software design of these instruments and give an overview of the returned dataset. Each instrument consisted of a highresolution accelerometer coupled with a tri-axis inertial measur...

In-situ measurements of ocean surface wave spectra evolution in the Antarctic marginal ice zone are described. Analysis of the measurements shows significant wave heights and peak periods do not vary appreciably in approximately the first 80 km of the ice-covered ocean. Beyond this region, significant wave heights attenuate and peak periods increas...

The propagation of large, storm-generated waves through sea ice has so far not been measured, limiting our understanding of how ocean waves break sea ice. Without improved knowledge of ice breakup, we are unable to understand recent changes, or predict future changes, in Arctic and Antarctic sea ice. Here we show that storm-generated ocean waves pr...

Intraseasonal relationships between Antarctic sea ice and atmospheric circulation have been investigated using a 29-yr record of pentad-mean Antarctic sea ice concentration and Southern Hemisphere 500-hPa height fields. Analyses were carried out for four sea ice seasons: minimum extent, growth, maximum extent, and decay. Interannual variability was...

Wave attenuation in a diffuse marginal ice zone (MIZ) is thought to be mainly a result of wave scattering. In a compact MIZ, additional physical factors are thought to be relevant. In this paper, we propose that viscous drag, form drag and energy lost to internal waves under the ice play a role in attenuating wave energy. We derive a relation for t...

The marginal ice zone (MIZ) is the boundary between the open ocean and ice‐covered seas, where sea ice is significantly affected by the onslaught of ocean waves. Waves are responsible for the breakup of ice floes and determine the extent of the MIZ and floe size distribution. When the ice cover is highly fragmented, its behavior is qualitatively di...

Waves can drastically transform the properties and behavior of the ice cover in a very short time. Consequently, they potentially represent a severe threat for personnel and make offshore operations challenging (for example during platform evacuation) if not anticipated. Waves-in-ice and floe sizes also have implications for the design of marine st...

Ocean waves are the main factor affecting ice properties in marginal ice zones yet their effects on sea ice are not included in numerical models. Waves contribute to break-up the ice cover in small floes, affecting how momentum is transferred from the atmosphere and the ocean. A fragmented ice cover can no longer be described as a plastic material...

We solve the problem of wave scattering by multiple floating elastic plates with arbitrary boundary conditions, such as spring connectors or hinges at the plate edges. We present two solution methods, the first method is based on a matched eigenfunction expansion and the second uses a Green function. The matched eigenfunction expansion method allow...

We present a model for wave attenuation in the marginal ice zone (MIZ) based on a two-dimensional (one horizontal and one vertical dimension) multiple floating elastic plate solution in the frequency domain, which is solved exactly using a matched eigenfunction expansion. The only physical parameters that enter the model are length, mass, and elast...

We investigate the problem of linear water wave propagation under a set of elastic plates of variable properties. The problem is two-dimensional, but we allow the waves to be incident from an angle. Since the properties of the elastic plates can be set arbitrarily, the solution method can also be applied to model regions of open water as well as el...

We present a model for wave propagation in the marginal ice zone (MIZ). The model is based on a two-dimensional linear water wave floating-elastic-plate solution in the frequency domain using a matched eigenfunction expansion. The model is fully coherent so the results are dependent on exact geometry, and we show firstly that this dependence can be...

This thesis considers the scattering of small amplitude water waves, obliquely incident on a set of floating elastic plates occupying the entire water surface. The problem is twodimensional and assumes invariance in the width of the plates. All non-linear physical effects are neglected. The plates are floating on a body of water of finite depth and...