Flows in the Tasman Front south of Norfolk Island

Sutton, Philip; Bowen, Melissa

doi:10.1002/2013jc009543

Cited by 21 publications

(22 citation statements)

References 23 publications

(53 reference statements)

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“…Shifting the chosen transect southward or northward upstream of the separation location does not change this distribution. There are no particles in this simulation that originate from a depth deeper than 700 m ending up north of New Zealand while following the Tasman Front, in agreement with the observed values by Sutton and Bowen []. This indicates that whether a particle follows the Tasman Front or the EAC extension (the “fate” of a particle) is to some extent already determined before the EAC bifurcates.…”

Section: Resultssupporting

confidence: 92%

“…While transporting heat and biota from the Coral Sea to the Tasman Sea, the EAC separates into an eastward current at approximately 34°S known as the Tasman Front and a southward branch forming the EAC extension [e.g., Godfrey et al ., 1980a; Ridgway and Dunn , ]. Volume transports of both pathways have been previously estimated at ∼9.7 Sv for the extension of the EAC [ Oliver and Holbrook , ] and between −4 and 18 Sv for the Tasman Front [ Sutton and Bowen , ], although the highly variable nature of the pathways' strength and location makes accurate estimates difficult. The EAC current system is highly variable and dynamic, with a ratio of eddy kinetic energy to mean kinetic energy of 500:1 compared to 10:1 in the global average [e.g., Mata et al ., ; Scharffenberg and Stammer , ; Everett et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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The separation of the East Australian Current: A Lagrangian approach to potential vorticity and upstream control

et al. 2016

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The East Australian Current (EAC) is the western boundary current flowing along the east coast of Australia separating from the coast at approximately 34°S. After the separation two main pathways can be distinguished, the eastward flowing Tasman Front and the extension of the EAC flowing southward. The area south of the separation latitude is eddy‐rich and the separation latitude of the EAC is variable. Little is known of the properties of the water masses that separate at the bifurcation of the EAC. This paper presents new insights from the Lagrangian perspective, where the water masses that veer east and those that continue south are tracked in an eddy‐permitting numerical model. The transport along the two pathways is computed, and a 1:3 ratio between transport in the EAC extension and transport in the Tasman Front is found. The results show that the “fate” of the particles is to first order already determined by the particle distribution within the EAC current upstream of the separation latitude, where 85% of the particles following the EAC extension originate from below 460 m and 90% of the particles following the Tasman Front originate from the top 460 m depth at 28°S. The separation and pathways are controlled by the structure of the isopycnals in this region. Analysis of anomalies in potential vorticity show that in the region where the two water masses overlap, the fate of the water depends on the presence of anticyclonic eddies that push isopycnals down and therefore enable particles to travel further south.

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

The separation of the East Australian Current: A Lagrangian approach to potential vorticity and upstream control

et al. 2016

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“…The bias across the Tasman Sea results in a more focused eastward flow and is typical of other modeling studies in the region (Oliver & Holbrook, ; Ypma et al, ). The Tasman Front's observed transport is highly variable and at times westward (Sutton & Bowen, ). Observed in different time periods, across different sections, mean transport estimates vary: 7.6–8.5 Sv (Stanton, ), 12–13 Sv (Stanton, ), 12.9 Sv (Ridgway & Dunn, ), and the first direct measurements by Sutton and Bowen () of 7.8 Sv.…”

Section: Model Evaluationmentioning

confidence: 99%

“…The Tasman Front's observed transport is highly variable and at times westward (Sutton & Bowen, ). Observed in different time periods, across different sections, mean transport estimates vary: 7.6–8.5 Sv (Stanton, ), 12–13 Sv (Stanton, ), 12.9 Sv (Ridgway & Dunn, ), and the first direct measurements by Sutton and Bowen () of 7.8 Sv. The CTRL experiment Tasman Sea mean outflow of 7.6 Sv (Figure , section GD) is within the range of observed transports.…”

Section: Model Evaluationmentioning

confidence: 99%

“…The EAC system (summarized in Figure e) consists of a relatively steady upstream current (22.1 ± 7.5 Sv at 27°S; Sloyan et al, ), which partially bifurcates at 30°S–34°S (Cetina‐Heredia et al, ). The branch that flows east forms the Tasman Front (Sutton & Bowen, ) and contributes to New Zealand's boundary currents, including the East Auckland Current and East Cape Current (Chiswell et al, ). In the process of separation, the EAC sheds an anticyclonic eddy (average radius 95 km; Everett et al, ) every ∼100 days (Mata et al, ).…”

Section: Introductionmentioning

confidence: 99%

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The Role of the New Zealand Plateau in the Tasman Sea Circulation and Separation of the East Australian Current

et al. 2018

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The East Australian Current (EAC) plays a major role in regional climate, circulation, and ecosystems, but predicting future changes is hampered by limited understanding of the factors controlling EAC separation. While there has been speculation that the presence of New Zealand may be important for the EAC separation, the prevailing view is that the time‐mean partial separation is set by the ocean's response to gradients in the wind stress curl. This study focuses on the role of New Zealand, and the associated adjacent bathymetry, in the partial separation of the EAC and ocean circulation in the Tasman Sea. Here utilizing an eddy‐permitting ocean model (NEMO), we find that the complete removal of the New Zealand plateau leads to a smaller fraction of EAC transport heading east and more heading south, with the mean separation latitude shifting >100 km southward. To examine the underlying dynamics, we remove New Zealand with two linear models: the Sverdrup/Godfrey Island Rule and NEMO in linear mode. We find that linear processes and deep bathymetry play a major role in the mean Tasman Front position, whereas nonlinear processes are crucial for the extent of the EAC retroflection. Contrary to past work, we find that meridional gradients in the basin‐wide wind stress curl are not the sole factor determining the latitude of EAC separation. We suggest that the Tasman Front location is set by either the maximum meridional gradient in the wind stress curl or the northern tip of New Zealand, whichever is furthest north.

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The Southwest Pacific Ocean circulation and climate experiment (SPICE)

Ganachaud

Cravatte

Melet

et al. 2014

J. Geophys. Res. Oceans

124

110

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The Southwest Pacific Ocean Circulation and Climate Experiment (SPICE) is an international research program under the auspices of CLIVAR. The key objectives are to understand the Southwest Pacific Ocean circulation and the South Pacific Convergence Zone (SPCZ) dynamics, as well as their influence on regional and basin-scale climate patterns. South Pacific thermocline waters are transported in the westward flowing South Equatorial Current (SEC) toward Australia and Papua-New Guinea. On its way, the SEC encounters the numerous islands and straits of the Southwest Pacific and forms boundary currents and jets that eventually redistribute water to the equator and high latitudes. The transit in the Coral, Solomon, and Tasman Seas is of great importance to the climate system because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate the El Niño-Southern Oscillation, while the southward transports influence the climate and biodiversity in the Tasman Sea. After 7 years of substantial in situ oceanic observational and modeling efforts, our understanding of the region has much improved. We have a refined description of the SPCZ behavior, boundary currents, pathways, and water mass transformation, including the previously undocumented Solomon Sea. The transports are large and vary substantially in a counter-intuitive way, with asymmetries and gating effects that depend on time scales. This paper provides a review of recent advancements and discusses our current knowledge gaps and important emerging research directions.

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Flows in the Tasman Front south of Norfolk Island

Cited by 21 publications

References 23 publications

The separation of the East Australian Current: A Lagrangian approach to potential vorticity and upstream control

The separation of the East Australian Current: A Lagrangian approach to potential vorticity and upstream control

The Role of the New Zealand Plateau in the Tasman Sea Circulation and Separation of the East Australian Current

The Southwest Pacific Ocean circulation and climate experiment (SPICE)

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