A dynamical system for classifying buoyant coastal discharges

Garvine, Richard W.

doi:10.1016/0278-4343(94)00065-u

Cited by 241 publications

(183 citation statements)

References 21 publications

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“…For most large-scale buoyancy driven coastal currents, K is ~3 or 4 [Garvine, 1995]. Ri then depends on the ratio of the two slopes, a/s, and will be •-10 times this ratio.…”

Section: Discussionmentioning

confidence: 99%

Fresh water delivery to the continental shelf and subsequent mixing: An observational study

Sanders¹,

Garvine²

2001

J. Geophys. Res.

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Abstract. We address two questions related to buoyant coastal discharge: (1) What agents control the delivery of estuarine fresh water to the shelf?. (2) How is this fresh water mixed with shelf water? Our subject was the Delaware Coastal Current, the buoyancy driven current originating in the Delaware estuary. The delivery of freshwater to the shelf at subtidal frequencies is controlled by two forcing agents: upland freshwater discharge into the estuary and the component of the wind parallel to the estuarine axis. The mean current we observed in the source region showed a strong decline in speed and large counterclockwise veering with increased depth. These variations in the mean current are best explained by thermal wind shear. From the moored instrument records we found evidence that in the source region mixing events of several hours duration are common at tidal frequencies when the local Richardson number Ri drops to a minimum level below 1/4. Furthermore, there is a pronounced modulation of this minimum level for Ri controlled by the action of coastal Ekman circulation. Data from the satellitetracked drifters show the striking difference between the coastal current configuration during downwelling and upwelling events. During downwelling the flow is downshelf and weakly onshore with particle trajectories orthogonal to the mean horizontal salinity gradient. In contrast, during upwelling the flow is strongly offshore and somewhat upshelf with particle trajectories down the mean salinity gradient, implying rapid mixing of plume water with shelf water. Corresponding values for horizontal dispersion of plume water showed modest values for both the along-shelf and across-shelf directions under downwelling but a very large value for the across-shelf dispersion under upwelling. We conclude that wind stress, acting through the mediation of the strain field produced by coastal upwelling circulation, is the primary means for completing the mixing of fresh water within the plume with shelf water.

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“…For most large-scale buoyancy driven coastal currents, K is ~3 or 4 [Garvine, 1995]. Ri then depends on the ratio of the two slopes, a/s, and will be •-10 times this ratio.…”

Section: Discussionmentioning

confidence: 99%

Fresh water delivery to the continental shelf and subsequent mixing: An observational study

Sanders¹,

Garvine²

2001

J. Geophys. Res.

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“…Hydrographic data were collected with h Neil Brown Mark IV (1992 and 1993) or a Sea-Bird 911 Plus (1994 and1995) CTD system. The instruments were factory calibrated after each cruise, and an offset was applied to the CTD salinities based on comparisons with bottle salinities.…”

Section: Methodsmentioning

confidence: 99%

The Siberian Coastal Current: A wind‐ and buoyancy‐forced Arctic coastal current

Weingartner¹,

Danielson²,

Sasaki³

et al. 1999

J. Geophys. Res.

194

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Abstract. We describe circulation and mixing in the Siberian Coastal Current (SCC) using fall shipboard measurements collected between 1992 and 1995 in the western Chukchi Sea. The SCC, forced by winds, Siberian river outflows, and ice melt, flows eastward from the East Siberian Sea. It is bounded offshore by a broad (---60 km) front separating cold, dilute Siberian Coastal Water from warmer, saltier Bering Sea Water. The alongshore flow is incoherent, because the current contains energetic eddies and squirts probably generated by frontal (baroclinic) instabilities. These enhance horizontal mixing and weaken the cross-shore density gradient along the SCC path. Eventually, the SCC converges with the northward flow from Bering Strait, whereupon it deflects offshore and mixes with that inflow. Deflection occurs where the alongshore pressure gradient The foregoing description implies that the SCC is largely driven by the positive buoyancy influx provided by river discharge. However, winds also play an important role on these 29,697

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“…Yankovsky and Chapman (1997) derived two length scales based on outflow properties (velocity, depth and density anomaly) and used them to discriminate between bottom-advected, intermediate and surface-advected plumes, depending on the vertical and horizontal density gradients near the plume front; in spite of the absence of external forcing mechanisms in their theory, they correctly predicted the plume type for several numerical and real cases. Garvine (1987) classified plumes as supercritical or subcritical using the ratio of horizontal discharge velocity to internal wave phase speed and he later proposed (Garvine, 1995) a classification system based on bulk properties of the buoyant discharge. Referenced plume studies present numerical modelling of the case, in situ observations (Sherwin et al, 1997;Warrick & Stevens, 2011;Ogston et al, 2000), satellite observations (Di Giacomo et al, 2004;Nezlin and Di Giacomo, 2005;Molleri et al, 2010) or aerial photographs (Figueiredo da Silva et al, 2002;Burrage et al, 2008).…”

Section: Introductionmentioning

confidence: 99%