Effect of wind and local density on the subtidal circulation of the inner Scotian Shelf

Jiang, Sheng; Thompson, Keith R.; Cong, Liangzi; Smith, Peter C.; Lawrence, D.E.

doi:10.1016/s0278-4343(00)00075-3

Cited by 6 publications

(10 citation statements)

References 11 publications

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“…This is smaller than the value of 650 cm 2 s À1 used by Thompson and Sheng [1997] and reflects the weaker winds observed in February 1996compared to winter 1985-1986[Sheng et al, 2001.…”

Section: Vertical Eddy Viscosity and Bottom Frictionmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

“…They include coastal sea levels, bottom pressures, currents at fixed moorings, temperatures and salinities and the trajectories of drifters released in four trials each of about one week's duration. (Details of the field program are given by Sheng et al [2001] along with a description of the observations.) [5] We will show that the model has significant skill in predicting currents, in accord with an earlier analysis by Thompson and Sheng [1997] of data collected in the same region during the Canadian Atlantic Storm Program (CASP) in the winter of 1985 -1986.…”

Section: Introductionmentioning

confidence: 99%

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Prediction of surface currents and drifter trajectories on the inner Scotian Shelf

et al. 2003

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[1] The predictive skill of a simple model of surface flow on the Scotian Shelf is assessed using oceanographic data collected in February 1996. The model is forced by wind stress, water density, and sea level along the open boundaries of the model domain.The skill of the model with respect to subtidal variations of alongshore current and bottom pressure is quantified by the ratio g 2 = Var(O À P)/Var(O), where Var(O À P) and Var(O) are the variance of the prediction errors and observations, respectively. Skill is highest for bottom pressure (g 2 = 0.2) followed, in order, by cross-shelf gradients in bottom pressure (g 2 = 0.5), horizontally averaged currents (0.4 < g 2 < 0.7), and currents at individual current meters (0.6 < g 2 < 1.4). The skill of the model with respect to drifter position is quantified by the search radius, centered on the predicted drifter position, that ensures a 50% chance of locating the drifter. Skill varies significantly with time but is generally highest when the drifter motion is strongest. We conclude with a comparison of the performance of the model against predictions based on the release point of the drifters and the operational scheme presently used to guide marine search and rescue in this region.

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“…This is smaller than the value of 650 cm 2 s À1 used by Thompson and Sheng [1997] and reflects the weaker winds observed in February 1996compared to winter 1985-1986[Sheng et al, 2001.…”

Section: Vertical Eddy Viscosity and Bottom Frictionmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prediction of surface currents and drifter trajectories on the inner Scotian Shelf

et al. 2003

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“…Similarly, the present estimates for the inner SW Nova Scotia section compare favorably with measured values from the Cape Sable array (April 1979 to March 1980 [ Smith , 1983]). The larger magnitudes of the velocities and transports on the inner Halifax section compared to those estimated by Drinkwater et al [1979] point to the importance of the baroclinic pressure gradient field below 100 m (note the sloping near‐bottom isohalines in Figure 2 [see also Sheng et al , 2001].…”

Section: Annual Cyclementioning

confidence: 99%

“…Recent findings that the seasonal circulation in the Scotian Shelf region is primarily baroclinic [ Han et al , 1997; Hannah et al , 2001; Sheng et al , 2001], together with evidence of substantial decadal‐scale and interannual changes in hydrographic properties of advective origin [ Petrie and Drinkwater , 1993; Drinkwater et al , 1999; Smith et al , 2001], point to the potential for significant decadal‐scale and interannual circulation changes. However, a major difficulty in the identification of such changes is the absence of long time series of current measurements.…”

Section: Introductionmentioning

confidence: 99%

Hydrographic and transport variability on the Halifax section

et al. 2003

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[1] Archived data and geostrophic computations are used to examine variability in hydrographic properties and along-shelf transport on the Scotian Shelf, with focus on the Halifax section and a decadal-scale hydrographic anomaly during the late 1950s and early/ mid 1960s. The long-term annual cycle shows strong seasonal variations in baroclinic transport on the inner shelf and at the shelf edge, and an associated steric change in adjusted sea level (ASL) at Halifax. Regional wind-forcing and barotropic currents make smaller contributions to the annual cycle in ASL. In contrast, regional wind-forcing contributes about 40% of the ASL variability for periods of 6-30 days. Hydrographic sections indicate that the 1950s/1960s anomaly arose from episodic extensions of Labrador Slope Water along the shelf edge followed by on-shelf intrusions, primarily during the fall-spring periods of 1958-1959 and 1963-1964. It ended with excursions of Warm Slope Water into the region in [1967][1968]. An analysis of monthly temperature anomalies indicates that slope temperatures can account for 50% of the variance of deep shelf temperatures 3-6 months later. Correlations between the hydrographic and baroclinic transport variations indicate increased southwestward flow associated with lower temperatures and salinities, but no evidence was found for large local current events at the onset and termination times of the 1950s/1960s anomaly. Positive correlations between wind-adjusted ASL and steric anomalies point to the potential for sea level being helpful in monitoring baroclinic transport variability.

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Numerical study of circulation and temperature-salinity distributions in the Bras d’Or Lakes

et al. 2007

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The Bras d'Or Lakes (BdOL) are a large, complex and virtually land-locked estuary in central Cape Breton Island of Nova Scotia and one of Canada's charismatic ecosystems, sustaining ecological and cultural communities unique in many aspects. The BdOL comprise two major basins, many deep and shallow bays, several narrow channels and straits and a large, geologically complex watershed. Predictive knowledge of the water movement within the estuary is a key requirement for effective management and sustainable development of the BdOL ecosystem. A three-dimensional (3D) primitiveequation ocean circulation model is used to examine the estuary's response to tides, winds and buoyancy forcing associated with freshwater runoff in a series of numerical experiments validated with empirical data. The model results generate intense, jet-like tidal flows of about 1 m s −1 in the channels between the basins and connecting them to the ocean and relatively weak tidal currents in other regions, which agrees well with previous observations and numerical results. Wind forcing and buoyancy forcing associated with river runoff play important roles in generating the significant sub-tidal circulations in the estuary, including narrow channels, deep basins and shallow bays. The circulation model is also used to reconstruct the 3D circulation and temperature-salinity distributions in the summer months of 1974, when current and hydrographic measurements were made at several locations. The sub-tidal circulation in the estuary produced by the model is characterised by wind and barometric set-up and set-down in different sections of the system, and a classic two-layer estuarine circulation in which brackish, near-surface waters flow seaward from the estuary into the Atlantic Ocean, and deep salty waters flow landward through the major channel. The model results reproduce reasonably well the overall features of observed circulation and temperature-salinity fields made in the BdOL in 1974 but generally underestimate the observed currents and density stratification. The model discrepancies reflect the use of spatially mean wind forcing and spatially and monthly mean surface heat flux and the inability of the coarse model horizontal resolution (∼500 m) to resolve narrow channels and straits.

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Effect of wind and local density on the subtidal circulation of the inner Scotian Shelf

Cited by 6 publications

References 11 publications

Prediction of surface currents and drifter trajectories on the inner Scotian Shelf

Prediction of surface currents and drifter trajectories on the inner Scotian Shelf

Hydrographic and transport variability on the Halifax section

Numerical study of circulation and temperature-salinity distributions in the Bras d’Or Lakes

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