Mean Flow and Variabilities in the Deep Western Boundary Current

1984 ◽  
Vol 14 (9) ◽  
pp. 1488-1498 ◽  
Author(s):  
David Y. Lai
Keyword(s):  
Western Boundary Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Mean Flow ◽  
Deep Western Boundary Current

scholarly journals Diagnosing the Influence of Mesoscale Eddy Fluxes on the Deep Western Boundary Current in the 1/10° STORM/NCEP Simulation

2019 ◽  
Vol 49 (3) ◽  
pp. 751-764 ◽  
Author(s):  
Veit Lüschow ◽  
Jin-Song von Storch ◽  
Jochem Marotzke
Keyword(s):  
Potential Energy ◽  
Mesoscale Eddy ◽  
Western Boundary Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Mean Flow ◽  
Coriolis Parameter ◽  
Deep Western Boundary Current ◽  
Eddy Fluxes ◽  
The Mean

AbstractUsing a 0.1° ocean model, this paper establishes a consistent picture of the interaction of mesoscale eddy density fluxes with the geostrophic deep western boundary current (DWBC) in the Atlantic between 26°N and 20°S. Above the DWBC core (the level of maximum southward flow, ~2000-m depth), the eddies flatten isopycnals and hence decrease the potential energy of the mean flow, which agrees with their interpretation and parameterization in the Gent–McWilliams framework. Below the core, even though the eddy fluxes have a weaker magnitude, they systematically steepen isopycnals and thus feed potential energy to the mean flow, which contradicts common expectations. These two vertically separated eddy regimes are found through an analysis of the eddy density flux divergence in stream-following coordinates. In addition, pathways of potential energy in terms of the Lorenz energy cycle reveal this regime shift. The twofold eddy effect on density is balanced by an overturning in the plane normal to the DWBC. Its direction is clockwise (with upwelling close to the shore and downwelling further offshore) north of the equator. In agreement with the sign change in the Coriolis parameter, the overturning changes direction to anticlockwise south of the equator. Within the domain covered in this study, except in a narrow band around the equator, this scenario is robust along the DWBC.

scholarly journals Midlatitude–Equatorial Dynamics of a Grounded Deep Western Boundary Current. Part I: Midlatitude Flow and the Transition to the Equatorial Region

2015 ◽  
Vol 45 (10) ◽  
pp. 2457-2469 ◽  
Author(s):  
Gordon E. Swaters
Keyword(s):  
Bottom Topography ◽  
Zonal Flow ◽  
Ocean Basin ◽  
Equatorial Region ◽  
Western Boundary Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Qualitative Properties ◽  
Deep Western Boundary Current ◽  
The Tropics

AbstractA comprehensive theoretical study of the nonlinear hemispheric-scale midlatitude and cross-equatorial steady-state dynamics of a grounded deep western boundary current is given. The domain considered is an idealized differentially rotating, meridionally aligned basin with zonally varying parabolic bottom topography so that the model ocean shallows on both the western and eastern sides of the basin. Away from the equator, the flow is governed by nonlinear planetary geostrophic dynamics on sloping topography in which the potential vorticity equation can be explicitly solved. As the flow enters the equatorial region, it speeds up and becomes increasingly nonlinear and passes through two distinguished inertial layers referred to as the “intermediate” and “inner” inertial equatorial boundary layers, respectively. The flow in the intermediate equatorial region is shown to accelerate and turn eastward, forming a narrow equatorial jet. The qualitative properties of the solution presented are consistent with the known dynamical characteristics of the deep western boundary currents as they flow from the midlatitudes into the tropics. The predominately zonal flow across the ocean basin in the inner equatorial region (and its exit from the equatorial region) is determined in Part II of this study.

scholarly journals Characteristics and causes of Deep Western Boundary Current transport variability at 34.5° S during 2009–2014

2016 ◽  
Author(s):  
Christopher S. Meinen ◽  
Silvia L. Garzoli ◽  
Renellys C. Perez ◽  
Edmo Campos ◽  
Alberto R. Piola ◽  
...  
Keyword(s):  
Volume Transport ◽  
Horizontal Resolution ◽  
Western Boundary Current ◽  
Meridional Overturning Circulation ◽  
Time Variability ◽  
Western Boundary ◽  
Boundary Current ◽  
Meridional Heat Transport ◽  
Data Set ◽  
Deep Western Boundary Current

Abstract. The Deep Western Boundary Current (DWBC) at 34.5° S in the South Atlantic carries a significant fraction of the cold deep limb of the Meridional Overturning Circulation (MOC), and therefore its variability affects both the meridional heat transport and the regional and global climate. Nearly six years of observations from a line of pressure-equipped inverted echo sounders (PIES) have yielded an unprecedented data set for studying the characteristics of the time-varying DWBC volume transport at 34.5° S. Furthermore, the horizontal resolution of the observing array was greatly improved in December 2012 with the addition of two current-and-pressure-equipped inverted echo sounders (CPIES) at the midpoints of three of the existing sites. Regular hydrographic sections along the PIES/CPIES line confirm the presence of recently-ventilated North Atlantic Deep Water carried by the DWBC. The time-mean absolute geostrophic transport integrated within the DWBC layer, defined between 800–4800 dbar, and within longitude bounds of 51.5° W to 44.5° W is −15 Sv (1 Sv = 106 m3 s−1; negative indicates southward flow). The observed peak-to-peak range in volume transport using these integration limits is from −89 Sv to +50 Sv, and the temporal standard deviation is 23 Sv. Testing different vertical integration limits based on time-mean water-mass property levels yields small changes to these values, but no significant alteration to the character of the transport time series. The time-mean southward DWBC flow at this latitude is confined west of 49.5° W, with recirculations dominating the flow further offshore. As with other latitudes where the DWBC has been observed for multiple years, the time variability greatly exceeds the time-mean, suggesting the presence of strong coherent vortices and/or Rossby Wave-like signals propagating to the boundary from the interior.

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