The Southern Ocean meridional overturning circulation as diagnosed from an eddy permitting state estimate

Mazloff, Matthew R.

doi:10.1575/1912/2608

Cited by 11 publications

(24 citation statements)

References 81 publications

(142 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This transport is somewhat larger than past estimates (137 6 7 Sv; review by Meredith et al 2011), but agrees with more recent ones (Firing et al 2011;154 6 38 Sv). The standard deviation is consistent with a recent eddying Southern Ocean state estimate (Mazloff 2008), but much smaller than reported from observations, possibly because models underestimate the current temporal variability or because observational estimates are biased high due to poor temporal sampling especially at depth. We show below that tracers injected in the model move eastward at the same rate as the tracer released in DIMES, further confirming that the model eastward transport is consistent with observations.…”

Section: The Drake Patch Modelsupporting

confidence: 85%

Direct Estimate of Lateral Eddy Diffusivity Upstream of Drake Passage

Tulloch

Ferrari²,

Jahn

et al. 2014

Journal of Physical Oceanography

View full text Add to dashboard Cite

The first direct estimate of the rate at which geostrophic turbulence mixes tracers across the Antarctic Circumpolar Current is presented. The estimate is computed from the spreading of a tracer released upstream of Drake Passage as part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). The meridional eddy diffusivity, a measure of the rate at which the area of the tracer spreads along an isopycnal across the Antarctic Circumpolar Current, is 710 6 260 m 2 s 21 at 1500-m depth. The estimate is based on an extrapolation of the tracer-based diffusivity using output from numerical tracers released in a one-twentieth of a degree model simulation of the circulation and turbulence in the Drake Passage region. The model is shown to reproduce the observed spreading rate of the DIMES tracer and suggests that the meridional eddy diffusivity is weak in the upper kilometer of the water column with values below 500 m 2 s 21 and peaks at the steering level, near 2 km, where the eddy phase speed is equal to the mean flow speed. These vertical variations are not captured by ocean models presently used for climate studies, but they significantly affect the ventilation of different water masses.

show abstract

Section: The Drake Patch Modelsupporting

confidence: 85%

Direct Estimate of Lateral Eddy Diffusivity Upstream of Drake Passage

Tulloch

Ferrari²,

Jahn

et al. 2014

Journal of Physical Oceanography

View full text Add to dashboard Cite

show abstract

“…In contrast to other data assimilation approaches, no spurious nudging terms are introduced in the dynamical equations, and therefore the state estimate represents a physically sound solution that satisfies the discretized equations of motion of the model. Mazloff (2008) describes in detail the assimilation procedure and the observations used. SOSE is a good resource for quantifying the dynamical balances in question because it has eddy kinetic energy on par with that observed, it is largely consistent with individual observations, and it is consistent with integrated fluxes inferred from previous static inverse models (Mazloff et al 2010).…”

Section: Introductionmentioning

confidence: 99%

The Force Balance of the Southern Ocean Meridional Overturning Circulation

Mazloff

Ferrari

Schneider

2013

Journal of Physical Oceanography

Self Cite

View full text Add to dashboard Cite

The Southern Ocean (SO) limb of the meridional overturning circulation (MOC) is characterized by three vertically stacked cells, each with a transport of about 10 Sv (Sv [ 10 6 m 3 s 21). The buoyancy transport in the SO is dominated by the upper and middle MOC cells, with the middle cell accounting for most of the buoyancy transport across the Antarctic Circumpolar Current. A Southern Ocean state estimate for the years 2005 and 2006 with 1 /68 resolution is used to determine the forces balancing this MOC. Diagnosing the zonal momentum budget in density space allows an exact determination of the adiabatic and diapycnal components balancing the thickness-weighted (residual) meridional transport. It is found that, to lowest order, the transport consists of an eddy component, a directly wind-driven component, and a component in balance with mean pressure gradients. Nonvanishing time-mean pressure gradients arise because isopycnal layers intersect topography or the surface in a circumpolar integral, leading to a largely geostrophic MOC even in the latitude band of Drake Passage. It is the geostrophic water mass transport in the surface layer where isopycnals outcrop that accomplishes the poleward buoyancy transport.

show abstract

“…Applying 4D‐Var to a regional, high‐resolution ocean circulation model with realistic physics is a good strategy to capture aspects of the real flow in energetic regions. There have been only a few studies in this direction [ Gebbie , 2004; Gebbie et al , 2006; Lea et al , 2006; Losch et al , 2008; Mazloff , 2008], however, mainly because of the technical challenge, and further experience is needed. Performing high‐resolution regional data assimilation in the SO using 4D‐Var is the subject of this paper.…”

Section: Introductionmentioning

confidence: 99%

Upper ocean state estimation in the Southern Ocean Gas Exchange Experiment region using the four-dimensional variational technique

Dwivedi¹,

Haine

Castillo³

2011

J. Geophys. Res.

View full text Add to dashboard Cite

A prototypical ocean circulation model, and associated 4‐D variational data assimilation system, is configured in support of the Southern Ocean Gas Exchange Experiment (Southern Ocean GasEx). The regional circulation model has 4 km horizontal resolution and 5 m vertical resolution in the upper ocean. In situ temperature and salinity observations and remotely sensed, gridded sea surface temperature and sea surface height observations are combined with the circulation model between 6 March and 4 April 2008. The benefits of customized data assimilation in support of a single oceanographic cruise are illustrated using Southern Ocean GasEx as a case study. The assimilated fields fit the observations within their respective uncertainties and fit 4–6 times better than the initial guess solution before assimilation. The fit of the assimilated fields is up to 100 times closer to observations than various global state estimate products using a cost function variance metric. The space‐time variability in mixed layer depth is consistent with the Southern Ocean GasEx observations and shows a deepening through March 2008. This variability is correlated with sea level height anomalies, sea surface temperature, and air temperature, during the assimilation window. The mixed layer depth estimate between 21 March and 4 April 2008 at the location of the Southern Ocean GasEx deliberate tracer release is 41–54 ± 6 m. The average zonal volume flux estimate is 16 ± 1.9 Sv (1 Sv is 106 m3 s−1) for latitudes 50.7°S–51.8°S, longitude 38.5°W. The zonal volume flux approximately halves during 6–16 March; temporal changes in volume flux are associated with geostrophic circulation but not with the Ekman circulation.

show abstract

The Southern Ocean meridional overturning circulation as diagnosed from an eddy permitting state estimate

Cited by 11 publications

References 81 publications

Direct Estimate of Lateral Eddy Diffusivity Upstream of Drake Passage

Direct Estimate of Lateral Eddy Diffusivity Upstream of Drake Passage

The Force Balance of the Southern Ocean Meridional Overturning Circulation

Upper ocean state estimation in the Southern Ocean Gas Exchange Experiment region using the four-dimensional variational technique

Contact Info

Product

Resources

About