Mixing Variability in the Southern Ocean

Meyer, Amélie; Sloyan, Bernadette M.; Polzin, Kurt L.; Phillips, Helen E.; Bindoff, Nathaniel L.

doi:10.1175/jpo-d-14-0110.1

Cited by 42 publications

(77 citation statements)

References 105 publications

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“…The objective of SOFine was to investigate the relation between finescale processes and the momentum balance in the Antarctic Circumpolar Current (Naveira Garabato 2009; Waterman et al 2013;Damerell et al 2013;Waterman et al 2014;Phillips and Bindoff 2014;Meyer et al 2015;Forryan et al 2015). In this study, the analysis of the internal wave field is based primarily on data from eight EM-APEX Argo-equivalent floats.…”

Section: ) Surveymentioning

confidence: 99%

“…Fronts can be identified using hydrographic criteria such as velocity maxima location, water-mass distribution, and locations where certain hydrographic properties cross particular depths (Belkin and Gordon 1996). Using surface velocity maxima determined from satGEM (Meijers et al 2011), a weekly geostrophic velocity product, Meyer et al (2015) found a coherent and intense jet north of the Kerguelen Plateau over the sampling period of the EM-APEX floats (18 November 2008 to 30 January 2009). The jet was identified as the middle and northern branches of the Subantarctic Front, likely merged with the southern branch of the Subtropical Front.…”

Section: B Regional Oceanographymentioning

confidence: 99%

“…1, 2). Another feature identified by Meyer et al (2015) from the EM-APEX data and the satGEM product is a large meander-like structure pinching off the SAF/STF region, hereinafter referred to as the eddy. The eddy is located between 448 and 428S and 698 and 738E (Fig.…”

Section: B Regional Oceanographymentioning

confidence: 99%

“…The implications in terms of Doppler shift and wave-mean flow interactions are discussed in section 5. We include some results from a companion paper that explores the impact of the internal wave field on local mixing characteristics (Meyer et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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Internal Waves and Mixing near the Kerguelen Plateau

Meyer

Polzin

Sloyan

et al. 2015

Journal of Physical Oceanography

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In the stratified ocean, turbulent mixing is primarily attributed to the breaking of internal waves. As such, internal waves provide a link between large-scale forcing and small-scale mixing. The internal wave field north of the Kerguelen Plateau is characterized using 914 high-resolution hydrographic profiles from novel Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats. Altogether, 46 coherent features are identified in the EM-APEX velocity profiles and interpreted in terms of internal wave kinematics. The large number of internal waves analyzed provides a quantitative framework for characterizing spatial variations in the internal wave field and for resolving generation versus propagation dynamics. Internal waves observed near the Kerguelen Plateau have a mean vertical wavelength of 200 m, a mean horizontal wavelength of 15 km, a mean period of 16 h, and a mean horizontal group velocity of 3 cm s 21 . The internal wave characteristics are dependent on regional dynamics, suggesting that different generation mechanisms of internal waves dominate in different dynamical zones. The wave fields in the Subantarctic/Subtropical Front and the Polar Front Zone are influenced by the local small-scale topography and flow strength. The eddy-wave field is influenced by the large-scale flow structure, while the internal wave field in the Subantarctic Zone is controlled by atmospheric forcing. More importantly, the local generation of internal waves not only drives largescale dissipation in the frontal region but also downstream from the plateau. Some internal waves in the frontal region are advected away from the plateau, contributing to mixing and stratification budgets elsewhere.

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Section: ) Surveymentioning

confidence: 99%

Section: B Regional Oceanographymentioning

confidence: 99%

Section: B Regional Oceanographymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Internal Waves and Mixing near the Kerguelen Plateau

Meyer

Polzin

Sloyan

et al. 2015

Journal of Physical Oceanography

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“…Calibration and quality control of the velocity data are described in Phillips and Bindoff (2014). Quality control of the temperature and salinity dataset is described in Meyer et al (2015).…”

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confidence: 99%

Detecting and Characterizing Ekman Currents in the Southern Ocean

Roach

Phillips

Bindoff

et al. 2015

Journal of Physical Oceanography

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This study presents a unique array of velocity profiles from Electromagnetic Autonomous Profiling Explorer (EM-APEX) profiling floats in the Antarctic Circumpolar Current (ACC) north of Kerguelen. The authors use these profiles to examine the nature of Ekman spirals, formed by the action of the wind on the ocean's surface, in light of Ekman's classical linear theory and more recent enhancements. Vertical decay scales of the Ekman spirals were estimated independently from current amplitude and rotation. Assuming a vertically uniform geostrophic current, decay scales from the Ekman current heading were twice as large as those from the current speed decay, indicating a compressed spiral, consistent with prior observations and violating the classical theory. However, if geostrophic shear is accurately removed, the observed Ekman spiral is as predicted by classical theory and decay scales estimated from amplitude decay and rotation converge toward a common value. No statistically robust relationship is found between stratification and Ekman decay scales. The results indicate that compressed spirals observed in the Southern Ocean arise from aliasing of depth-varying geostrophic currents into the Ekman spiral, as opposed to surface trapping of Ekman currents associated with stratification, and extends the geographical area of similar results from Drake Passage (Polton et al. 2013). Accounting for this effect, the authors find that constant viscosity Ekman models offer a reasonable description of momentum mixing into the upper ocean in the ACC north of Kerguelen. These results demonstrate the effectiveness of a new method and provide additional evidence that the same processes are active for the entire Southern Ocean.

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Investigation into the impact of storms on sustaining summer primary productivity in the Sub‐Antarctic Ocean

Nicholson

Lévy

Llort

et al. 2016

Geophysical Research Letters

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In the Sub‐Antarctic Ocean elevated phytoplankton biomass persists through summer at a time when productivity is expected to be low due to iron limitation. Biological iron recycling has been shown to support summer biomass. In addition, we investigate an iron supply mechanism previously unaccounted for in iron budget studies. Using a 1‐D biogeochemical model, we show how storm‐driven mixing provides relief from phytoplankton iron limitation through the entrainment of iron beneath the productive layer. This effect is significant when a mixing transition layer of strong diffusivities (kz > 10−4 m2 s−1) is present beneath the surface‐mixing layer. Such subsurface mixing has been shown to arise from interactions between turbulent ocean dynamics and storm‐driven inertial motions. The addition of intraseasonal mixing yielded increases of up to 60% in summer primary production. These results stress the need to acquire observations of subsurface mixing and to develop the appropriate parameterizations of such phenomena for ocean‐biogeochemical models.

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Mixing Variability in the Southern Ocean

Cited by 42 publications

References 105 publications

Internal Waves and Mixing near the Kerguelen Plateau

Internal Waves and Mixing near the Kerguelen Plateau

Detecting and Characterizing Ekman Currents in the Southern Ocean

Investigation into the impact of storms on sustaining summer primary productivity in the Sub‐Antarctic Ocean

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