Standard Presentation 2024 Australian Marine Sciences Association Annual Meeting combined with NZMSS

Meridional transport of physical and biogeochemical tracers by Southern Ocean eddies  (#480)

Ramkrushnbhai Patel 1 2 , Helen Phillips 1 3 , Andrew Lenton 4 , Peter Strutton 1 2 , Tyler Rohr 1 3 , Matthew Chamberlain 4 , Joan Llort 5
  1. Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS), Hobart, Tasmania, Australia
  2. Australian Research Council Centre of Excellence for Climate Extremes, University of Tasmania, Hobart, Tasmania, Australia
  3. Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
  4. Commonwealth Scientific and Industrial Research Organisation (CSIRO), Environment, Hobart, Tasmania, Australia
  5. Barcelona Supercomputing center, Barcelona, Spain

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. Comparing models and observational estimates often presents challenges due to varying methodologies used to describe `eddy' processes. We reconcile the approach used in shipboard surveys of coherent eddies complemented with satellite eddy tracking, and Reynolds decomposition, to estimate the fraction of total meridional tracer transport due to coherent eddies in a global 0.1° ocean model. Annual meridional transports, in the model, due to coherent eddies crossing the Subantarctic Front are estimated using vertically and radially integrating the tracer contents of all eddies. Only cyclonic eddies moving equatorward across the Subantarctic Front contributed to the coherent eddy transport. No anticyclonic eddies were found to cross the Subantarctic Front poleward in this region. Using Reynolds decomposition, the meridional transports due to all transient processes were poleward almost everywhere in a standing meander and intense between the northern and southern branches of the Subantarctic Front. Coherent, long-lived eddies that can be tracked from satellite transported less than 10% of the transient poleward transport of heat, salt and equatorward transport of nitrate in the model.