Revisiting the circulation of the East Australian Current: Its path, separation, and eddy field

Oke, Peter R.; Roughan, Moninya; Cetina‐Heredia, Paulina; Pilo, Gabriela S.; Ridgway, K.; Rykova, Tatiana; Archer, Matthew; Coleman, Richard; Kerry, Colette; Rocha, Carlos; Schaeffer, Amandine; Vitarelli, Eduardo

doi:10.1016/j.pocean.2019.102139

Cited by 79 publications

(116 citation statements)

References 124 publications

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“…In the southwest Pacific Ocean, P. saltatrix undertake annual migrations along the East Australian Current (EAC; Brodie et al, 2018). The EAC is a western boundary current which flows poleward along eastern Australia until it separates from the coast (31–33°S) with much of the water volume turning eastward (Cetina‐Heredia et al, 2014; Oke et al, 2019). Downstream of the separation, the EAC is characterised by high eddy variability which creates a dynamic environment for larval dispersal.…”

Section: Introductionmentioning

confidence: 99%

Multiple spawning events promote increased larval dispersal of a predatory fish in a western boundary current

Schilling

Everett

Smith

et al. 2020

Fisheries Oceanography

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Transport of larvae by ocean currents is an important dispersal mechanism for many species. The timing and location of spawning can have a large influence on settlement location. Shifts in the known spawning habitat of fish, whether due to climate or the discovery of new spawning stock, can influence the distribution of juveniles and our understanding of connectivity. The globally distributed species; Pomatomus saltatrix, is one such example where a previously unrecognised summer spawning event and a more southern latitudinal extent was recently reported for the southwest Pacific population. Although restrictions are in place to protect the traditional spawning event, the importance of the newly recognised summer spawning event is uncertain. Here, we investigate larval dispersal of P. saltatrix using particle tracking simulations to identify the contributions of the different spawning events to settlement. By modelling dispersal of larvae released in northern and mid‐latitude regions over the Austral spring and summer, we show that the newly recognised mid‐latitude summer spawning event contributes over 50% of the larvae reaching southern latitudes. This is due to a reduced (1–2 days) pelagic larval duration (associated with temperature), resulting in reduced larval mortality, and the seasonal (summer) strengthening of the East Australian Current (EAC) transporting particles ~50 km further south. These findings demonstrate that in dynamic boundary current systems such as the EAC, the final settlement location of larvae that are transported by ocean currents can vary considerably depending on the timing and location of spawning and that multiple spawning events are important for maximum dispersal.

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Section: Introductionmentioning

confidence: 99%

Multiple spawning events promote increased larval dispersal of a predatory fish in a western boundary current

Schilling

Everett

Smith

et al. 2020

Fisheries Oceanography

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“…Eddies form in all parts of the EAC region, as far north as 25 • S (Qiu & Chen, 2004), with the greatest eddy kinetic energy (EKE) occurring between 32 • S and 35 • S (Bowen et al, 2005). A variety of mechanisms have Oke, Roughan, et al (2019). Black solid lines denote permanent currents and black dashed lines denote transient currents associated with "eddy trains."…”

Section: Introductionmentioning

confidence: 99%

Downstream Evolution of the East Australian Current System: Mean Flow, Seasonal, and Intra‐annual Variability

Kerry

Roughan

2020

JGR Oceans

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The East Australian Current (EAC) varies on both seasonal and mesoscale eddy related timescales, with important impacts for weather, primary productivity, and fisheries. While the EAC and its eddies have been the subject of many synoptic studies, a consistent three-dimensional picture of the current, its downstream evolution, and the associated seasonal and intra-annual variability is lacking. We use a 22-year model simulation to quantify the EAC's temporal and latitudinal variability, from where it flows as a mostly coherent jet (27 • S) to its separation from the coast (31-33 • S), its energetic eddy field in the Tasman Sea and its southern extension. We show that the current intensifies and deepens poleward toward the separation latitude; the mean poleward transport reaches a maximum of 26.8 Sv and the seasonal cycle amplitude peaks at 6.2 Sv. Over the separation region, the EAC core broadens and shallows, mean poleward transport is lower and the transport standard deviation peaks at 22.0 Sv. The meandering EAC jet is modulated at interannual timescales, while the eddy driven transport over the separation region has a strong annual modulation, related to the annual cycle in eddy kinetic energy. SSH variability at intra-annual frequencies is described primarily by an alongshore propagating mode and an onshore propagating mode, demonstrating that mesoscale SSH variability stems from a combination of intrinsic instabilities of the EAC jet and westward propagating Rossby waves. The results provide the first holistic analysis of the EAC system along its latitudinal range.

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“…The EAC is the western boundary current within the South Pacific subtropical gyre. At around 30-32 • S, it splits into an eastward extension known as the Tasman Front, and a southward extension, mainly consisting of a flow of eddies (Oke et al, 2019), referred to as the "Eddy Avenue" (Everett et al, 2012). In this region, eddies are deep and centered around 300-350 m depth with temperature FIGURE 1 | A schematic showing the boundaries of the region analyzed (red box).…”

Section: Introductionmentioning

confidence: 99%

Observational Insight Into the Subsurface Anomalies of Marine Heatwaves

Elzahaby

Schaeffer

2019

Front. Mar. Sci.

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Marine heatwaves (MHWs) are extreme ocean warming events that can have devastating impacts, from biological mortalities to irreversible redistributions within the ocean ecosystem. MHWs are an added concern because they are expected to increase in frequency and duration. To date, our understanding of these extreme ocean temperature events is mainly limited to the surface layers, despite some of the consequences they are known to have on the deep marine environment. In this paper, using data from sea surface temperature (SST) and in situ observations from Argo floats, we investigate the anomalous water characteristics during MHWs down to 2000 m in the western Tasman Sea which is located off the east coast of Australia. Focusing on their vertical extensions, characteristics and potential drivers, we break MHWs down into three categories (1) shallow [0-150 m], (2) intermediate [150-800 m], and (3) deep events [>800 m]. Only shallow events show a relationship between surface temperature anomalies and depth extent, in agreement with a likely surface origin in response to anomalous air-sea fluxes. By contrast, deep events have greater and deeper maximum temperature anomalies than their surface signal (mean of almost 3.4 • C at 165 m depth) and are more frequent than expected (>45%), dominating MHWs in winter. They predominantly occur within warm core eddies, which are deep mesoscale anticyclonic structures carrying warm water-mass from the East Australian Current (EAC). This study highlights the importance of MHWs down to 2000 m and the influence of oceanographic circulation on their characteristics. Consequently, we recommend a complementary analysis of sea level anomalies and SST be conducted to improve the prediction of MHW characteristics and impacts, both physical and biological.

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Revisiting the circulation of the East Australian Current: Its path, separation, and eddy field

Cited by 79 publications

References 124 publications

Multiple spawning events promote increased larval dispersal of a predatory fish in a western boundary current

Multiple spawning events promote increased larval dispersal of a predatory fish in a western boundary current

Downstream Evolution of the East Australian Current System: Mean Flow, Seasonal, and Intra‐annual Variability

Observational Insight Into the Subsurface Anomalies of Marine Heatwaves

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