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Meridional transport of physical and biogeochemical tracers by Southern Ocean eddies
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  • Ramkrushnbhai S Patel,
  • Andrew Allan Lenton,
  • Helen Elizabeth Phillips,
  • Peter G. Strutton,
  • Tyler Weaver Rohr,
  • Joan Llort,
  • Matthew A Chamberlain
Ramkrushnbhai S Patel
Institute for Marine and Antarctic Studies

Corresponding Author:[email protected]

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Andrew Allan Lenton
Commonwealth Scientific and Industrial Research Organisation (CSIRO) Oceans and Atmosphere
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Helen Elizabeth Phillips
University of Tasmania
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Peter G. Strutton
University of Tasmania
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Tyler Weaver Rohr
University of Tasmania
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Joan Llort
Barcelona Supercomputing Centre
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Matthew A Chamberlain
CSIRO Marine and Atmospheric Research
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Meridional eddy transport across the Antarctic Circumpolar Current is an essential component of the global meridional overturning circulation and the transport of climate relevant tracers. Challenges in comparing model and observational estimates of the transport arise from varying methodologies describing ‘eddy’ processes. We reconcile the approach used in shipboard surveys of eddies, complemented by satellite eddy tracking, with Reynolds decomposition applied to model outputs. This allows us to estimate the fraction of total meridional tracer transport attributed to coherent eddies in a global 0.1$^\circ$ ocean model. The model realistically simulates observed eddy kinetic energy and three-dimensional characteristics, particularly in representing an observed cyclonic eddy near 150 \degrees E, a hotspot for poleward heat flux. Annual meridional transports due to coherent eddies crossing the Subantarctic Front are estimated by vertically and radially integrating the tracer contents of all eddies. Notably, only cyclonic eddies moving equatorward across the Subantarctic Front contribute to the coherent eddy transport, with no anticyclonic eddies found to cross the front poleward in this region. Applying Reynolds decomposition, our study reveals predominantly poleward meridional transports due to all transient processes in a standing meander, particularly between the northern and southern branches of the Subantarctic Front. Coherent, long-lived eddies tracked from satellite data contribute less than 20\% to transient poleward heat transport, and equatorward nitrate transport in the model. Furthermore, we demonstrate that the integrated surface elevation of mesoscale eddies serves as a reliable proxy for inferring subsurface eddy content.
21 Dec 2023Submitted to ESS Open Archive
27 Dec 2023Published in ESS Open Archive