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Abstract Standing meanders are a key component of the Antarctic Circumpolar Current (ACC) circulation system, and numerical studies have shown that these features may locally enhance subduction, upwelling, as well as lateral and vertical tracer transport. Yet, observational data from these regions remain sparse. Here, we present results based on measurements made by a group of autonomous platforms sampling an ACC standing meander formed due to the interaction of the Polar Front with the Southwest Indian Ridge. Two Seagliders were deployed alongside a Biogeochemical‐Argo float that was advected through the standing meander. In the high eddy kinetic energy region of the standing meander, the glider observations reveal enhanced submesoscale frontal gradients as well as heightened tracer variability at depth, as compared to the more quiescent region further downstream. Vertical gradients in spice and apparent oxygen utilization are reduced in the standing meander despite similarities in the large‐scale vertical stratification, suggesting greater ventilation of the surface ocean. These observations are consistent with numerical studies that highlight standing meanders as hotspots for ventilation and subduction due to enhanced mesoscale stirring and submesoscale vertical velocities. Our results emphasize the need to account for spatial heterogeneity in processes influencing air‐sea exchange, carbon export, and biogeochemical cycling in the Southern Ocean.
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This content will become publicly available on May 1, 2026
The Southeast Indian Ridge: A Hotspot for Cross-Frontal Exchange
Abstract Cross-frontal exchange facilitated by mesoscale eddies in the lee of major topographic features of the Southern Ocean is fundamental to the global overturning circulation. Despite the outsize importance for meridional heat flux, we lack an accurate estimation of fluxes across the Antarctic Circumpolar Current (ACC) due to the challenges of observing mesoscale eddy fluctuations on the temporal and spatial scales required. Here, 12 years of Argo data are used to observe patterns of cross-frontal exchange in the Southeast Indian Ridge system, a relatively underobserved region, known to be a hotspot of exchange. Spice variance along ACC streamlines is used as a proxy for cross-frontal exchange. Elevated exchange is observed downstream of the ridge system in nearly every streamline and is particularly prominent in the core of the ACC. Notably, exchange peaks progressively downstream at each poleward streamline suggesting a systematic north-to-south handoff across nearly the full breadth of the ACC. Employing a mixing length framework, lateral stirring is parameterized as an eddy diffusivity on the isopycnal of peak exchange. We find a highly localized pattern of diffusivity, peaking between the crest and trough of the first standing meander in the lee of the ridge system. Spatially, this diffusivity pattern correlates with an along-stream increase in eddy kinetic energy. Along-stream vertical wavenumber spectra of spice anomaly profiles indicate that the vertical scales of intrusions, which are initially large (approximately 800 m), rapidly evolve downstream to smaller wavenumbers (100–300 m) presumably in response to intense vertical shear and filamentation.
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- Award ID(s):
- 2023306
- PAR ID:
- 10644059
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Physical Oceanography
- Volume:
- 55
- Issue:
- 5
- ISSN:
- 0022-3670
- Page Range / eLocation ID:
- 631 to 644
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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