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Response of Southern Hemisphere western boundary current regions to future zonally symmetric and asymmetric atmospheric changes
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  • Rishav Goyal,
  • Matthew H. England,
  • Martin Jucker,
  • Alex SenGupta
Rishav Goyal
University of New South Wales

Corresponding Author:[email protected]

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Matthew H. England
University of New South Wales
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Martin Jucker
University of New South Wales
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Alex SenGupta
University of New South Wales, Sydney
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Abstract

Subtropical Western Boundary Currents (WBCs) are often associated with hotspots of global warming, with certain WBC extension regions warming 3-4 times faster than the global mean. In the Southern Hemisphere strong warming over the WBC extensions has been observed over the last few decades, with enhanced warming projected into the future. This amplified warming has primarily been linked to poleward intensification of the mid-latitude westerly winds in the Southern Hemisphere. Changes in these winds are often thought of as being zonally symmetric, however, recent studies show that they contain strong zonal asymmetries in certain ocean basins. The importance of these zonal asymmetries for the Southern Ocean has not yet been investigated. In this study, we use an ocean-sea-ice model forced by prescribed atmospheric fields to quantify the contribution of projected zonally asymmetric atmospheric changes in generating future ocean warming and circulation changes in the subtropical WBC regions of the Southern Hemisphere. We find that the projected zonally asymmetric component of atmospheric change can explain more than 30% (>2°C) of the SST warming found in the Tasman Sea and southern Australia region and a sizeable fraction of warming in the Agulhas Current region. These changes in SST in both the Indian and Pacific Ocean basins are found to be primarily driven by changes in the large-scale subtropical ocean gyres, which in turn can largely be explained by changes in the surface wind stress patterns.
Nov 2021Published in Journal of Geophysical Research: Oceans volume 126 issue 11. 10.1029/2021JC017858