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Frontal eddies form on the shoreward edge of boundary currents, on average at weekly intervals and can last up to several weeks. This duration allows zooplankton production and completion of the larval stage of fish but may be too ephemeral for longer food chains with planktonic predators to establish. Therefore, frontal eddies may provide a suitable offshore nursery habitat, by entraining and retaining inner‐shelf water, preconditioned with coastal plankton and ichthyoplankton, into an upwelling favorable cyclonic eddy. Here, we briefly describe the behavior of frontal eddies formed by western boundary currents in the context of the fundamental ocean triad, which incorporates three processes for the successful reproduction of fish: nutrient enrichment, food concentration, and retention of larvae. We adapt this hypothesis for frontal eddies adjacent to the substantial fisheries production of continental shelves, creating conditions for enhanced recruitment potential of larval cohorts at a finer scale than previously considered. We review the evidence and investigations of frontal eddies in their capacity to entrain coastal water, sustain the plankton community through eddy uplift and retain distinctive coastal communities of larval fish offshore until larval development is complete. The process of frontal eddy formation is complex and such habitats are irregular yet ubiquitous, which present challenges and opportunities for their study. With the advance of ocean observing systems and integration of physical and biological sampling, frontal eddies provide a novel focus for understanding fisheries production and connectivity of coastal ecosystems. [ABSTRACT FROM AUTHOR]

Submesoscale lenses of water with anomalous hydrographic properties have previously been observed in the East Australian Current (EAC) system, embedded within the thermocline of mesoscale anticyclonic eddies. The waters within these lenses have high oxygen content and temperature–salinity properties that signify a surface origin. However, it is not known how these lenses form. This study presents field observations that provide insight into a possible generation mechanism via subduction at upper-ocean fronts. High-resolution hydrographic and velocity measurements of submesoscale activity were taken across a front between a mesoscale eddy dipole downstream of the EAC separation point. The front had O(1) Rossby number, strong vertical shear, and flow conducive to symmetric instability. Frontogenesis was measured in conjunction with subduction of an anticyclonic water parcel, indicative of intrathermocline eddy formation. Twenty-five years of satellite imagery reveals the existence of strong mesoscale strain coupled with strong temperature fronts in this region and indicates the conditions that led to frontal subduction observed here are a persistent feature. These processes impact the vertical export of tracers from the surface and dissipation of mesoscale kinetic energy, implicating their importance for understanding regional ocean circulation and biological productivity. [ABSTRACT FROM AUTHOR]

• We present challenge the traditional view of the EAC system and offer a new interpretation. • The EAC is a meandering stream that feeds a field of eddies. • We show that the Tasman Front and EAC Extension are rarely seen as distinct features.distinct, identifiable. • We summarise publishedworks on the EAC's path, separation, and eddy field. The traditional view of the East Australian Current (EAC), as depicted in many schematics, is of a continuous boundary current that flows along the shelf off eastern Australia, between approximately 18°S and about 32.5°S, where it separates from the coast and continues either towards New Zealand, along the Tasman Front; or towards Tasmania, as the EAC Extension. Additionally, it is widely recognised that eddies are prevalent in the EAC region – particularly south of the EAC separation. We revisit this long-standing paradigm and suggest that the EAC is perhaps better viewed as a continuous, meandering stream, flowing adjacent to the coast that "feeds" a field of mesoscale eddies. Observations show that EAC eddies are prevalent over a broad region of the western Tasman Sea, as far north as 25°S, typically with maximum intensity between 30 and 35°S. At any instant in time the EAC jet is usually evident as a poleward stream adjacent to the continental shelf edge. Other commonly accepted components of the EAC System, including the Tasman Front and EAC Extension, are rarely seen as distinct, identifiable features. Rather, these features are evident only in time-mean fields, when the eddy-variability is filtered out. It is also common for the EAC to be spatially discontinuous – due to the presence of eddies – often with multiple short streams that sometimes separate and re-attach to the coast. Recognition of the EAC as an eddy-dominated current system has seen many recent studies focus on various aspects of eddies in the EAC System, providing new insights into mesoscale ocean dynamics. Recent studies of individual eddies have shown that the circulation within eddies, including tilting and vertical motion, is more complex than previously understood. A summary of these studies, along with a review of the EAC System, particularly its path, separation, and eddy field is presented here. [ABSTRACT FROM AUTHOR]