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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 971

Last Page: 971

Title: Shelf-Break Circulation, Fronts, and Physical Oceanography: East and West Coast Perspectives: ABSTRACT

Author(s): Leonard J. Pietrafesa

Article Type: Meeting abstract


Physical oceanographic processes present at the continental shelf-slope interfaces of both the east and west coasts of the United States are presented, compared, and contrasted. The Southeast Atlantic Bight shelf-break sector is principally dominated by the Gulf Stream and its associated cyclonic front. At the high-frequency end of the current spectrum, the semi-diurnal tide and inertial currents are dominant. Subinertial frequency motions are dominated by: Gulf Stream frontal meanders, warm core filaments, and cold core eddy ridges; wind forcing; thermohaline forces; and the effects of topography. The Mid-Atlantic Bight and Gulf of Maine outer shelf are shown to contain many of the dynamic elements of the southeastern shelf-slope, but the relative importances of various andom surface and offshore low-frequency driving forces change.

West coast shelf-break processes differ principally from their east coast counterparts due to the absence of a Western Boundary Current. Principal circulation elements include various forms of continental shelf waves, wind-driven currents, tides, the California Current System and thermohaline effects.

Both subtidal and supertidal frequency events are shown to be capable of initiating sediment motion and of suspending sediments, but lower frequency events are shown to be responsible for the bulk of sediment migration on the outer shelf and slope environs. Gulf Stream frontal phenomena and winter-time atmospheric storms figure prominently in providing physical mechanisms for sediment movement.

The interplay of bottom topography with the physics of the outer continental margin is presented. Bottom features such as shoals, bumps, ridges, and canyons are shown to be regions of sediment erosion, deposition, and draping. Furthermore these features are shown to be causally related to upwelling and downwelling phenomena and to the deflection and scattering of waves and currents.

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