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A theory of standing meanders of the Antarctic Circumpolar Current and their response to wind

Version 2 2024-07-15, 01:12
Version 1 2023-05-21, 14:16
journal contribution
posted on 2024-07-15, 01:12 authored by Xihan Zhang, Maxim NikurashinMaxim Nikurashin, Beatriz Pena-MolinoBeatriz Pena-Molino, SR Rintoul, Edward DoddridgeEdward Doddridge

Standing meanders of the Antarctic Circumpolar Current (ACC) and associated eddy hotspots play an important role for the meridional heat flux and downward momentum transfer in the Southern Ocean. Previous modelling studies show that the vorticity balance characterising standing meanders in the upper ocean is dominated by advection of relative vorticity and stretching. Through the adjustment of this vorticity balance, standing meanders have been suggested to provide a pathway for the transfer of the momentum input by the wind from the surface to the bottom, leading to stronger bottom flows and energy dissipation. However, the dynamics governing the meander formation and its adjustment to wind remain unclear. Here we develop a quasi-geostrophic theory and combine it with a regional model of the Macquarie Ridge region and an idealized channel model to explore the dynamics and vertical structure of standing meanders of the ACC. The results show that the entire vertical structure of the meander, including its dynamics in the upper ocean, is controlled by the bottom flow interacting with topography. Based on our results, we suggest a novel mechanism for the response of the ACC to wind in which ‘flexing’ of the meander, or change in its curvature, is a response to changes in the bottom (barotropic) flow. Stronger bottom flow in response to stronger wind interacts with topography and generates a larger amplitude Rossby wave propagating into the upper ocean. The ACC mean shear aloft amplifies the Rossby wave and leads to a larger amplitude meander in the upper ocean dominated by advection of relative vorticity and stretching.

Funding

Department of Industry, Innovation and Science

History

Publication title

Journal of Physical Oceanography

Volume

53

Issue

1

Pagination

235-251

ISSN

0022-3670

Department/School

IMAS Directorate, Oceans and Cryosphere, Australian Antarctic Program Partnership

Publisher

Amer Meteorological Soc

Publication status

  • Published

Place of publication

45 Beacon St, Boston, USA, Ma, 02108-3693

Rights statement

© 2022 American Meteorological Society.

Socio-economic Objectives

190501 Climate change models

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