Deep and intermediate water replacement in the Strait of Georgia

LeBlond, Paul H.; Ma, Helai; Doherty, Ford; Pond, S.

doi:10.1080/07055900.1991.9649406

Cited by 58 publications

(60 citation statements)

References 11 publications

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“…Because these geostrophically balanced flows on a sloping bottom are driven by the density contrast between the relatively dense plume and the surrounding water we refer to them as "mesoscale gravity currents" [see, e.g., Britter and Linden, 1980;Honji and Hosoyamada, 1989;LeBlond et al, 1991] in order to emphasize the underlying fluid dynamical configuration and to differentiate them from nonrotating gravity currents on a flat bottom. Examples include the Denmark Strait overflow [Smith, 1976] …”

Section: Introduction and Model Descriptionmentioning

confidence: 99%

Numerical simulations of the baroclinic dynamics of density‐driven coupled fronts and eddies on a sloping bottom

Swaters¹

1998

J. Geophys. Res.

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Abstract. Numerical simulations of the baroclinic dynamics of density-driven coupled fronts and eddies are described. The simulations are based on a two-layer intermediate length scale model which filters out barotropic instability and focuses on the subinertial baroclinic evolution of density-driven flows within the context of allowing finite-amplitude height variations in the lower layer. The baroclinic destabilization of a bottom-trapped coupled front on a sloping bottom is described. In the overlying fluid the instability takes the form of amplifying topographic Rossby waves. In the coupled front the perturbations to the downslope incropping are preferentially amplified compared to those on the upslope incropping. The perturbations to the downslope incropping develop into downslope propagating plumes which eventually evolve into relatively coherent along-slope propagating domes. We discuss the propagation characteristics of these domes. We also simulate the evolution of density-driven eddies or domes. The first eddy simulation we describe is for an initial eddy configuration which satisfies a zero topographic Rossby wave condition in the upper layer. We show that these traveling solutions remain remarkably coherent over a period of about 40 eddy circulation times or about 250 days for typical continental slope values. For a sufficiently large initial eddy height, upper layer fluid parcels can be transported in the along-slope direction by the baroclinic eddy. We also simulate the evolution of an initial eddy configuration which does not satisfy a zero topographic Rossby wave condition in the upper layer. A relatively intense cyclonic circulation develops in the overlying fluid over the traveling dome as does a topographic Rossby wave tail. However, even these solutions remain surprisingly coherent over many eddy circulation times.

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Section: Introduction and Model Descriptionmentioning

confidence: 99%

Numerical simulations of the baroclinic dynamics of density‐driven coupled fronts and eddies on a sloping bottom

Swaters¹

1998

J. Geophys. Res.

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“…It is well known that less saline lighter water flows seaward in the upper layer, while more saline heavier water flows landward in the lower layer (Hansen and Rattray 1966). This flow pattern is called "estuarine circulation" and often observed in estuaries and bays, as the water exchange between coastal basins and adjacent ocean has long been a topic of great interest to oceanographers (e.g., Geyer and Cannon 1982;LeBlond et al 1991;Allen and Simpson 1998). If the estuarine circulation is dominant, bottom water is readily renewed by oceanic water.…”

Section: Formation Mechanism Of Hypoxiamentioning

confidence: 99%

Hypoxia Controlled by Hydrodynamics

Kasai¹

2014

Aqua-BioSci. Monogr. (ABSM)

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In summer dissolved oxygen is often depleted in the lower and bottom layers in many coastal basins all over the world. This phenomena is called hypoxia. When the oxygen consumption exceeds oxygen supply, the water becomes hypoxic. The oxygen is consumed by decomposing organic matter by bacteria (biochemical processes), while the oxygen is supplied by physical processes such as convection, advection and diffusion. The primary cause of hypoxia is the consumption of oxygen in the water column, but physical processes mainly control its generation, distribution and configuration. In addition to the vertical supply of oxygen by mixing, horizontal transport by estuarine circulation plays the major role in the formation of hypoxia in regions of freshwater influence. As the hypoxic water contains a lot of nutrients, it plays an important role for primary production, producing middle layer chlorophyll maximum in summer and inducing bloom of phytoplankton in autumn.

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“…Away from the source region, Stommel-Arons theory cannot infer the flow direction of abyssal currents. However, many abyssal currents are characterized by the isopycnal field being grounded against sloping topography [e.g., the deep western boundary undercurrent in the North Atlantic Ocean (Richardson 1977), and the deep water replacement current in the Strait of Georgia (LeBlond et al 1991;Masson 2002)] and the flow being in geostrophic balance. As shown by Nof (1983), a fully grounded abyssal water mass lying over sloping topography flows, in the fully nonlinear but reduced gravity dynamical limit, nondispersively and steadily in the along-slope direction, irrespective of the specific height or vorticity field within the abyssal water mass.…”

Section: Introductionmentioning

confidence: 99%

The Meridional Flow of Source-Driven Abyssal Currents in a Stratified Basin with Topography. Part I: Model Development and Dynamical Properties

Swaters

2006

Journal of Physical Oceanography

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A numerical simulation is described for source-driven abyssal currents in a 3660 km ϫ 3660 km stratified Northern Hemisphere basin with zonally varying topography. The model is the two-layer quasigeostrophic equations, describing the overlying ocean, coupled to the finite-amplitude planetary geostrophic equations, describing the abyssal layer, on a midlatitude ␤ plane. The source region is a fixed 75 km ϫ 150 km area located in the northwestern sector of the basin with a steady downward volume transport of about 5.6 Sv (Sv ϵ 10 6 m 3 s Ϫ1) corresponding to an average downwelling velocity of about 0.05 cm s Ϫ1. The other parameter values are characteristic of the North Atlantic Ocean. It takes about 3.2 yr for the abyssal water mass to reach the southern boundary and about 25 yr for a statistical state to develop. Time-averaged and instantaneous fields at a late time are described. The time-averaged fields show an equatorward-flowing abyssal current with distinct up-and downslope groundings with decreasing height in the equatorward direction. The average equatorward abyssal transport is about 8 Sv, and the average abyssal current thickness is about 500 m and is about 400 km wide. The circulation in the upper layers is mostly cyclonic and is western intensified, with current speeds about 0.6 cm s Ϫ1. The upper layer cyclonic circulation intensifies in the source region with speeds about 4 cm s Ϫ1, and there is an anticyclonic circulation region immediately adjacent to the western boundary giving rise to a weak barotropic poleward current in the upper layers with a speed of about 0.6 cm s Ϫ1. The instantaneous fields are highly variable. Even though the source is steady, there is a pronounced spectral peak at the period of about 54 days. The frequency associated with the spectral peak is an increasing function of the downwelling volume flux. The periodicity is associated with the formation of transient cyclonic eddies in the overlying ocean in the source region and downslope propagating plumes and boluses in the abyssal water mass. The cyclonic eddies have a radii about 100-150 km and propagation speeds about 5-10 cm s Ϫ1. The eddies are formed initially because of stretching associated with the downwelling in the source region. Once detached from the source region, the cyclonic eddies are phase locked with the boluses or plumes that form on the downslope grounding of the abyssal current, which themselves form because of baroclinic instability. Eventually, the background vorticity gradients associated with ␤ and the sloping bottom arrest the downslope (eastward) motion, the abyssal boluses diminish in amplitude, the abyssal current flows preferentially equatorward, the upper layer eddies disperse and diminish in amplitude, and westward intensification develops.

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Deep and intermediate water replacement in the Strait of Georgia

Cited by 58 publications

References 11 publications

Numerical simulations of the baroclinic dynamics of density‐driven coupled fronts and eddies on a sloping bottom

Numerical simulations of the baroclinic dynamics of density‐driven coupled fronts and eddies on a sloping bottom

Hypoxia Controlled by Hydrodynamics

The Meridional Flow of Source-Driven Abyssal Currents in a Stratified Basin with Topography. Part I: Model Development and Dynamical Properties

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