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Suppression of Internal Wave Breaking in the Antarctic Circumpolar Current near Topography

Suppression of Internal Wave Breaking in the Antarctic Circumpolar Current near Topography
Suppression of Internal Wave Breaking in the Antarctic Circumpolar Current near Topography
Simultaneous full-depth microstructure measurements of turbulence and finestructure measurements of velocity and density are analyzed to investigate the relationship between turbulence and the internal wave field in the Antarctic Circumpolar Current. These data reveal a systematic near-bottom overprediction of the turbulent kinetic energy dissipation rate by finescale parameterization methods in select locations. Sites of near-bottom overprediction are typically characterized by large near-bottom flow speeds and elevated topographic roughness. Further, lower-than-average shear-to-strain ratios indicative of a less near-inertial wave field, rotary spectra suggesting a predominance of upward internal wave energy propagation, and enhanced narrowband variance at vertical wavelengths on the order of 100 m are found at these locations. Finally, finescale overprediction is typically associated with elevated Froude numbers based on the near-bottom shear of the background flow, and a background flow with a systematic backing tendency. Agreement of microstructure- and finestructure-based estimates within the expected uncertainty of the parameterization away from these special sites, the reproducibility of the overprediction signal across various parameterization implementations, and an absence of indications of atypical instrument noise at sites of parameterization overprediction, all suggest that physics not encapsulated by the parameterization play a role in the fate of bottom-generated waves at these locations. Several plausible underpinning mechanisms based on the limited available evidence are discussed that offer guidance for future studies
Circulation/ Dynamics, Diapycnal mixing, Internal waves, Small scale processes, Turbulence, Observational techniques and algorithms, In situ oceanic observations, Profilers, oceanic
0022-3670
1466-1492
Waterman, Stephanie
e2809e53-b45c-4b0d-9aa4-6cccfe6fcf65
Polzin, Kyrt K,
54ea6a03-9335-4b9c-90c6-52204032e8fc
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Sheen, Katy L.
68e5eb70-6a29-48a4-a26a-227407f88df5
Forryan, Alexander
4e753ae9-7f12-495f-933a-2c5a1f554a0e
Waterman, Stephanie
e2809e53-b45c-4b0d-9aa4-6cccfe6fcf65
Polzin, Kyrt K,
54ea6a03-9335-4b9c-90c6-52204032e8fc
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Sheen, Katy L.
68e5eb70-6a29-48a4-a26a-227407f88df5
Forryan, Alexander
4e753ae9-7f12-495f-933a-2c5a1f554a0e

Waterman, Stephanie, Polzin, Kyrt K,, Naveira Garabato, Alberto C., Sheen, Katy L. and Forryan, Alexander (2014) Suppression of Internal Wave Breaking in the Antarctic Circumpolar Current near Topography. Journal of Physical Oceanography, 44 (5), 1466-1492. (doi:10.1175/JPO-D-12-0154.1).

Record type: Article

Abstract

Simultaneous full-depth microstructure measurements of turbulence and finestructure measurements of velocity and density are analyzed to investigate the relationship between turbulence and the internal wave field in the Antarctic Circumpolar Current. These data reveal a systematic near-bottom overprediction of the turbulent kinetic energy dissipation rate by finescale parameterization methods in select locations. Sites of near-bottom overprediction are typically characterized by large near-bottom flow speeds and elevated topographic roughness. Further, lower-than-average shear-to-strain ratios indicative of a less near-inertial wave field, rotary spectra suggesting a predominance of upward internal wave energy propagation, and enhanced narrowband variance at vertical wavelengths on the order of 100 m are found at these locations. Finally, finescale overprediction is typically associated with elevated Froude numbers based on the near-bottom shear of the background flow, and a background flow with a systematic backing tendency. Agreement of microstructure- and finestructure-based estimates within the expected uncertainty of the parameterization away from these special sites, the reproducibility of the overprediction signal across various parameterization implementations, and an absence of indications of atypical instrument noise at sites of parameterization overprediction, all suggest that physics not encapsulated by the parameterization play a role in the fate of bottom-generated waves at these locations. Several plausible underpinning mechanisms based on the limited available evidence are discussed that offer guidance for future studies

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Published date: May 2014
Keywords: Circulation/ Dynamics, Diapycnal mixing, Internal waves, Small scale processes, Turbulence, Observational techniques and algorithms, In situ oceanic observations, Profilers, oceanic
Organisations: Physical Oceanography

Identifiers

Local EPrints ID: 342462
URI: http://eprints.soton.ac.uk/id/eprint/342462
ISSN: 0022-3670
PURE UUID: acc071eb-9755-4ebf-abf3-14e3384ceace
ORCID for Alberto C. Naveira Garabato: ORCID iD orcid.org/0000-0001-6071-605X

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Date deposited: 30 Aug 2012 11:00
Last modified: 15 Mar 2024 03:24

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Contributors

Author: Stephanie Waterman
Author: Kyrt K, Polzin
Author: Katy L. Sheen
Author: Alexander Forryan

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