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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 communities, with the objective of closing loops in our understanding of the complex network of feedbacks in the overall system. The review is targeted at researchers in Southern Ocean physical science with the ambition of broadening their knowledge beyond their specific field, and aims at facilitating better‐informed interdisciplinary collaborations. For the purposes of this review, the Southern Ocean dynamic system is divided into four main components: large‐scale circulation; cryosphere; turbulence; and gravity waves. Overviews are given of the key dynamical phenomena for each component, before describing the linkages between the components. The reviews are complemented by an overview of observed Southern Ocean trends and future climate projections. Priority research areas are identified to close remaining loops in our understanding of the Southern Ocean system.

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A large collaborative program has studied the coupled air‐ice‐ocean‐wave processes occurring in the Arctic during the autumn ice advance. The program included a field campaign in the western Arctic during the autumn of 2015, with in situ data collection and both aerial and satellite remote sensing. Many of the analyses have focused on using and improving forecast models. Summarizing and synthesizing the results from a series of separate papers, the overall view is of an Arctic shifting to a more seasonal system. The dramatic increase in open water extent and duration in the autumn means that large surface waves and significant surface heat fluxes are now common. When refreezing finally does occur, it is a highly variable process in space and time. Wind and wave events drive episodic advances and retreats of the ice edge, with associated variations in sea ice formation types (e.g., pancakes, nilas). This variability becomes imprinted on the winter ice cover, which in turn affects the melt season the following year.

This work presents active cloaking of rigid and elastic cylindrical shells. The acoustic performance using single and multiple control sources and error sensors is investigated for different control configurations. Scattering by a rigid cylinder due to an incident plane wave is initially studied. The scattered acoustic field is actively attenuated using monopole control sources and error sensors located circumferentially around the cylinder. The structural and acoustic responses of an elastic shell due to an incident plane wave are then examined. Active cloaking at the shell circumferential modes is achieved using monopole control sources located in the surrounding fluid. Active structural acoustic cloaking is also achieved using control forces applied directly to the shell.

Sonic crystals are scatterers arranged periodically in a homogeneous fluid medium, for which sound does not transmit through the crystal in certain frequency bands known as stop bands. Acoustic wave transmission through a two-dimensional sonic crystal composed of a finite array of scatterers is investigated. Two types of scatterers are considered: sound-hard cylinders and C-shaped locally resonant scatterers. An analytical method is devised to solve the corresponding multiple scattering problems. The method combines an integral equation technique for the single scatterer with an enhanced multipole method using domain decomposition into slabs. A numerical approach using commercial software is also considered for validation and is based on the finite element method. Simulations of sound transmission through an array of 5 by 51 scatterers show remarkably good agreement with the corresponding infinite system. For an array comprising locally resonant scatterers, an approximate band gap around the resonator natural frequency is observed in addition to the band gap due to the overall periodicity of the finite sonic crystal.