scholarly journals Shallow water modeling of Antarctic Bottom Water crossing the equator

2004 ◽  
Vol 109 (C3) ◽  
Author(s):  
Paul F. Choboter ◽  
Gordon E. Swaters
Keyword(s):  
Shallow Water ◽  
Bottom Water ◽  
Antarctic Bottom Water ◽  
Water Modeling

scholarly journals Nonuniform Upwelling in a Shallow-Water Model of the Antarctic Bottom Water in the Brazil Basin*

2004 ◽  
Vol 34 (11) ◽  
pp. 2492-2513 ◽  
Author(s):  
Olivier Marchal ◽  
Jonas Nycander
Keyword(s):  
Shallow Water ◽  
Bottom Water ◽  
Water Model ◽  
Western Boundary ◽  
Linear Potential ◽  
Antarctic Bottom Water ◽  
Shallow Water Model ◽  
Boundary Current ◽  
Deep Basin ◽  
Brazil Basin

Abstract A numerical model based on the shallow-water equations is developed to represent the flow of Antarctic Bottom Water (AABW) in the Brazil Basin (southwest Atlantic Ocean). The aim is twofold. First, an attempt is made to identify in a model that includes both simplified dynamics and realistic bathymetry (at 1/6° resolution) the impacts of the elevated diapycnal mixing rates near the Mid-Atlantic Ridge (MAR) documented by dissipation data of the Deep Basin Experiment (DBE). To this end, different assumptions regarding the distribution of the velocity across the AABW layer interface (w) are considered. Second, the extent to which the shallow-water model can replicate observations relative to AABW circulation in the basin, in particular the trajectory and velocity of neutrally buoyant floats released in the AABW during the DBE, is examined. The model flows are characterized by small Rossby numbers, except in the northward-flowing western boundary current where kinetic energy is largely concentrated. To interpret the flows, model streamlines are compared with isopleths of linear potential vorticity f/h0 of the shallow-water theory (f is the planetary vorticity and h0 is the layer thickness in the absence of motion). The f/h0 contours are oriented northwest–southeast in the western part of the basin and southwest–northeast in the eastern part, reflecting the bowl-shaped topography of the Southern Hemisphere basin. With a spatially uniform (positive) w, the ubiquitous vortex stretching produces a flow to the southeast, consistent with the Stommel–Arons theory. This flow occurs in most of the basin interior, even in the east where f/h0 contours converge to the northeastern end of the basin. With strongly positive w near the ridge and zero or slightly negative w elsewhere, the flow follows more closely f/h0 contours in the western interior and intersects them near the ridge. The confinement of the diapycnal mass flux near the MAR drastically reduces the southward flow in the interior or even reverses its direction, leading to a circulation quite distinct from that of the Stommel– Arons theory. The model results compare favorably to some (but not all) hydrographic estimates of AABW circulation patterns and rates. On the other hand, the model streamlines and velocities show important differences with, respectively, the trajectory and the velocity of the floats launched in the AABW layer. The prescription of vanishing w in the interior does not systematically improve the fit of the model streamlines to the float trajectories, and the model velocities simulated with spatially uniform w or spatially variable w are on average smaller by one order of magnitude than the float velocities. A variety of mechanisms, which are not included in the numerical experiments, may explain the differences between the model results and the float data.

scholarly journals Ventilation of the abyss in the Atlantic sector of the Southern Ocean

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Camille Hayatte Akhoudas ◽  
Jean-Baptiste Sallée ◽  
F. Alexander Haumann ◽  
Michael P. Meredith ◽  
Alberto Naveira Garabato ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Bottom Water ◽  
Climate Models ◽  
Deep Ocean ◽  
Analytical Framework ◽  
Weddell Sea ◽  
Global Ocean ◽  
Shelf Water ◽  
Antarctic Bottom Water ◽  
Atlantic Sector

AbstractThe Atlantic sector of the Southern Ocean is the world’s main production site of Antarctic Bottom Water, a water-mass that is ventilated at the ocean surface before sinking and entraining older water-masses—ultimately replenishing the abyssal global ocean. In recent decades, numerous attempts at estimating the rates of ventilation and overturning of Antarctic Bottom Water in this region have led to a strikingly broad range of results, with water transport-based calculations (8.4–9.7 Sv) yielding larger rates than tracer-based estimates (3.7–4.9 Sv). Here, we reconcile these conflicting views by integrating transport- and tracer-based estimates within a common analytical framework, in which bottom water formation processes are explicitly quantified. We show that the layer of Antarctic Bottom Water denser than 28.36 kg m$$^{-3}$$ - 3 $$\gamma _{n}$$ γ n is exported northward at a rate of 8.4 ± 0.7 Sv, composed of 4.5 ± 0.3 Sv of well-ventilated Dense Shelf Water, and 3.9 ± 0.5 Sv of old Circumpolar Deep Water entrained into cascading plumes. The majority, but not all, of the Dense Shelf Water (3.4 ± 0.6 Sv) is generated on the continental shelves of the Weddell Sea. Only 55% of AABW exported from the region is well ventilated and thus draws down heat and carbon into the deep ocean. Our findings unify traditionally contrasting views of Antarctic Bottom Water production in the Atlantic sector, and define a baseline, process-discerning target for its realistic representation in climate models.

Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies

2020 ◽  
Vol 13 (12) ◽  
pp. 780-786 ◽  
Author(s):  
Alessandro Silvano ◽  
Annie Foppert ◽  
Stephen R. Rintoul ◽  
Paul R. Holland ◽  
Takeshi Tamura ◽  
...  
Keyword(s):  
Bottom Water ◽  
Ross Sea ◽  
Antarctic Bottom Water ◽  
Climate Anomalies ◽  
Water Formation ◽  
Bottom Water Formation

scholarly journals Trends in the deep Southern Ocean (1958-2010): Implications for Antarctic Bottom Water properties and volume export

2013 ◽  
Vol 118 (9) ◽  
pp. 4213-4227 ◽  
Author(s):  
Marina Azaneu ◽  
Rodrigo Kerr ◽  
Mauricio M. Mata ◽  
Carlos A. E. Garcia
Keyword(s):  
Southern Ocean ◽  
Bottom Water ◽  
Antarctic Bottom Water ◽  
Water Properties

scholarly journals Flow of Antarctic Bottom Water from the Vema Channel 

2020 ◽  
Author(s):  
Eugene G Morozov ◽  
Dmitry I. Frey ◽  
Roman Y. Tarakanov
Keyword(s):  
Continental Slope ◽  
Water Flow ◽  
North Atlantic ◽  
Bottom Water ◽  
The Other ◽  
Antarctic Bottom Water ◽  
The North ◽  
The North Atlantic ◽  
Current Flows ◽  
Western Wall

Abstract We analyze measurements of bottom currents and thermohaline properties of water north of the Vema Channel with the goal to find pathway continuations of Antarctic Bottom Water flow from the Vema Channel into the Brazil Basin. The analysis is based on CTD/LADCP casts north of the Vema Channel. The flow in the deep Vema Channel consists of two branches. The deepest current flows along the bottom in the center of the channel and the other branch flows above the western wall of the channel. We found two smaller channels of the northern continuation of the deeper bottom flow. These flows become weak and almost disappear at a latitude of 25°30’S. The upper current flows at a depth of 4100-4200 m along the continental slope. We traced this current up to 24°S over a distance exceeding 250 km. This branch transports bottom water that eventually fills the deep basins of the North Atlantic.

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