A Model and Observations of Time-Dependent Upwelling over the Mid-Shelf and Slope

Janowitz, G. S.; Pietrafesa, L. J.

doi:10.1175/1520-0485(1980)010<1574:amaoot>2.0.co;2

Cited by 51 publications

(17 citation statements)

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“…The loose correlation of regions of prolific reef growth with steepness of the continental slope (Maxwell, 1968;Maxwell and Swinchatt, 1970) is probably a reflection of upwelling amplitude and its observed (Orr, 1933) and theoretical correlation with shelf and slope topography (Csanady, 1973;Garrett, 1979;Janowitz and Pietrafesa, 1980). Mean nutrient levels and variabilities decrease poleward along the shelf break of our study site and so does the bathymetric gradient.…”

Section: Discussionmentioning

confidence: 74%

“…The period is 90 d. These nutrients are pumped inshore by a wind forced oscillatory bottom current and very rapidly progress to phytoplankton. The amplitude and period of the bottom current are approximately 10 cm S-' and 12 to 25 d. The physical model of wind driven intrusions by Janowitz and Pietrafesa (1980) predicts a return flow, for mass continuity, in the layers above the upwelling intrusion. Current meter data in Fig.…”

Section: Nutrient Concentrationsmentioning

confidence: 97%

“…However, regions of prolific reef growth are correlated with increasing steepness of the continental slope (Maxwell and Swinchatt, 1970). This suggests upwelling on theoretical grounds as Garrett (1979) and Janowitz and Pietrafesa (1980) have shown that the upwelling amplitude depends on the configuration of the shelf and slope. In the British Museum expedition of 1928/29, A. P. Orr (1933) observed elevated bottom water density in the Lagoon, created by deep-sea intrusions, and observed nutrient enrichment at the shelf break.…”

Section: Introductionmentioning

confidence: 98%

“…Blanton (1971) shows there is evidence for both mechanisms in observational data. Theoretical models do not clarify the situation since intrusions are equally well explained by models of meanders (Garrett, 1979) or of wind forcing (Janowitz and Pietrafesa, 1980). The relative roles of winds and boundary currents require elucidation.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Upwelling as a Source of Nutrients for the Great Barrier Reef Ecosystems: A Solution to Darwin's Question?

Andrews¹,

Gentien²

1982

Mar. Ecol. Prog. Ser.

182

110

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The Great Barrier Reef shelf ecosystem is examined for nutrient enrichment from within the seasonal thermocline of the adjacent Coral Sea using moored current and temperature recorders and chemical data from a year of hydrology cruises at 3 to 5 wk intervals. The East Australian Current is found to pulsate in strength over the continental slope with a period near 90 d and to pump cold, saline, nutrient rich water u p the slope to the shelf break. The nutrients are then pumped inshore in a bottom Ekman layer forced by periodic reversals in the longshore wind component. The period of this cycle is 12 to 25 d in summer (30 d year round average) and the bottom surges have a n alternating onshoreoffshore speed up to 10 cm S-'. Upwelling intrusions tend to b e confined near the bottom and phytoplankton development quickly takes place inshore of the shelf break. There are return surface flows which preserve the mass budget and carry silicate rich Lagoon water offshore while nitrogen rich shelf break water is carried onshore. Upwelling intrusions penetrate across the entire zone of reefs, but rarely into the Lagoon. Nutrition is del~vered out of the shelf thermocline to the living coral of reefs by localised upwelling induced by the reefs. Bottom chlorophyll concentrations average 0.4 mg m-3 a t the inner reefs and 0.8 mg m-3 near the shelf break while surface concentrations average 0.3 mg m-3; annual top and bottom variances are respectively 0.5 and 1.9 m g m-3 and there is no apparent seasonal cycle. The estimated onshore nitrogen flux in a 10 m thick bottom layer gives an annual nitrogen input of 20 yg at 1-' throughout the water column in a 50 km zone of reefs, a n enormous value for tropical waters.

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Section: Discussionmentioning

confidence: 74%

Section: Nutrient Concentrationsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Upwelling as a Source of Nutrients for the Great Barrier Reef Ecosystems: A Solution to Darwin's Question?

Andrews¹,

Gentien²

1982

Mar. Ecol. Prog. Ser.

182

110

View full text Add to dashboard Cite

show abstract

“…With a similar twolayer model, Csanady (1973) showed that the character of a wind-induced alongshore jet at the shelf break was controlled by the nature of the bottom slope and by stratification. Janowitz and Pietrafesa (1980) have also formulated a model for transient upwelling, which includes both bottom friction and weak stratification. Their results suggest that sufficiently sharp changes in the bottom slope at the shelf break produce a persistent upward bulge in the isopycnals, which implies a vertical shear in the alongshore current according to geostrophic dynamics.…”

Section: Internal Tide and Nonlinear Waves 348 338mentioning

confidence: 99%

Physical Processes at the Shelf Edge in the Northwest Atlantic

Smith¹,

Sandstrom²

1988

J. Northw. Atl. Fish. Sci.

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Abrupt depth changes at the edges of continental shelves leading to important physical processes in the ocean are described with reviews on the progress in understanding three such processes: (1) interaction of offshore currents and eddies with the continental margin; (2) wind-driven upwelling at the shelf break; (3) generation of internal tides and nonlinear waves by the M2 surface tide. Two possible modes of interaction between offshore currents and coastal waters are contrasted. The first is characterized by eddy exchange created by a current guided along the shelf edge (as on the Labrador and Newfoundland shelves or in the United States South Atlantic Bight) while the second involves remote forcing by low-frequency topographic Rossby waves radiated from offshore meanders and rings to the shelf edge. In addition, wind-driven upwelling from depths of 400 m or more results from moderate (10-15 m S-1) but persistent alongshore wind. Complex bathymetry of the shelf may cause anomalously high currents in a fully three-dimensional circulation. Large-amplitude internal waves driven by the M2 surface tide are a ubiquitous feature of the shelf edge circulation. The intense vertical mixing associated with these waves promotes high levels of biological productivity at the shelf edge by continuously supplying nutrients to the surface layers.

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Alongshore transport of a toxic phytoplankton bloom in a buoyancy current: Alexandrium tamarense in the Gulf of Maine

1992

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A Model and Observations of Time-Dependent Upwelling over the Mid-Shelf and Slope

Cited by 51 publications

References 0 publications

Upwelling as a Source of Nutrients for the Great Barrier Reef Ecosystems: A Solution to Darwin's Question?

Upwelling as a Source of Nutrients for the Great Barrier Reef Ecosystems: A Solution to Darwin's Question?

Physical Processes at the Shelf Edge in the Northwest Atlantic

Alongshore transport of a toxic phytoplankton bloom in a buoyancy current: Alexandrium tamarense in the Gulf of Maine

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