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Seasonal and interannual variability of the Subtropical Front in the New Zealand region
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  • Erik Behrens,
  • Andrew McC. Hogg,
  • Matthew H. England,
  • Helen Bostock
Erik Behrens

Corresponding Author:[email protected]

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Andrew McC. Hogg
Australian National University
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Matthew H. England
University of New South Wales
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Helen Bostock
University of Queensland
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The meridional variability of the Subtropical Front (STF) and the drivers of variability on interannual time scales in the New Zealand region are analysed using a multi-decadal eddy-resolving ocean hindcast model, in comparison with Argo data. The STF marks the water mass boundary between subtropical waters and subantarctic waters, and is defined as the southern-most location of the 11 degree C isotherm and 34.8 isohaline between 100 m and 500 m. The STF shifts up to 650 km (6 degree) meridionally on seasonal timescales. In addition to seasonal variability, shifts of around 200 km (2 degree) occur on interannual time scales. These shifts are connected to local wind stress curl anomalies in the eastern Tasman Sea, which trigger Ekman convergence/divergence and result in meridional transport of heat and salt into/out of the Tasman Sea. The net transports across the northern boundary of the Tasman Sea show the largest sensitivity to these wind stress curl anomalies. During periods of positive wind stress curl anomalies and Ekman convergence, the heat and salt content increases shifting the position of the STF southward. The opposite tendency occurs during periods of negative wind stress curl anomalies. The migration of the STF does not appear to be directly linked to regional climate oscillations.
Feb 2021Published in Journal of Geophysical Research: Oceans volume 126 issue 2. 10.1029/2020JC016412