A search for the Tasman Front
Date
2019
Authors
Oke, Peter
Pilo, Gabriela S.
Ridgway, Ken R.
Kiss, Andrew
Rykova, Tatiana
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Elsevier
Abstract
The traditional view of the circulation in the Tasman Sea includes a coherent, quasi-zonal, eastward flow towards the northern tip of New Zealand that is widely referred to as the Tasman Front. This flow was first
suggested in the 1960s by oceanographers reasoning that the source of volume transport “feeding” the East
Auckland Current, around northern New Zealand and extending down the east coast, must be off eastern
Australia. The first reported in situ measurements of the Tasman Front included hand-drawn temperature sections that highlighted features that are not supported by observations. Here, we objectively map the original
data, showing that the published reports of strong, sub-surface, north-south temperature gradients were unjustified. In the absence of additional observations, we can’t be sure of the context of those original measurements - so we have objectively “searched” fields in a recent 25-year ocean reanalysis to identify scenarios that
are consistent with the observations. We suggest that the most likely interpretation of the original data, is that
they measured an eddy field - or a series of discontinuous streams across the central Tasman Sea. We also analyse
data from surface drifting buoys to show that water traversing the Tasman Sea may take several different paths.
We conclude that a continuous, zonal, eastward flow across the Tasman Sea is less common than widely-accepted conceptual models imply. Instead, we suggest that the eastward flow between Australia and northern
New Zealand is perhaps better described as an “eastern extension of the EAC” - since this doesn’t imply the
presence of a front, and doesn’t preclude a broad flow. For clarity, we also suggest that the southern branch of
the EAC, known as the EAC extension, should be referred to as the “southern extension of the EAC”.
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Journal of Marine Systems
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Journal article
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Open Access
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CC BY-NC-ND
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