Fair weather and storm sand transport on the Long Island, New York, inner shelf |
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| Authors: | J W LAVELLE D J P SWIFT P E GADD W L STUBBLEFIELD F N CASE† H R BRASHEAR† K W HAFF† |
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| Institution: | NOAA/Atlantic Oceanographic and Meteorological Laboratories, 15 Rickenbacker Causeway, Miami, Florida 33149, U.S.A.;Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, Tennessee 37830, U.S.A. |
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| Abstract: | Both spring-summer and fall-winter sand transport have been observed on the Long Island, New York, inner shelf at water depths of 20-22 m using a radio-isotope sand tracer system. The extent of dispersal of the tagged, fine sand was measured at 3 week intervals in two 70 day experiments. In the late spring and early summer, movement was primarily diffusive in nature, extending 100 m around the line of tracer injection, while late fall-winter patterns had strong advective features, including an ellipsoidal outline extending approximately 1500 m westward of the injection points after the passage of several storms with strong northeasterly winds. Near-bottom current observations made with Savonius rotor sensors identify the event responsible for the bulk of the transport over the 135 day observation period as a storm flow of 2 days duration. Tracer and current observations together suggest that westward winter storm flow along the Long Island shelf is the major mechanism of sand transport at these depths on a yearly time scale. A least-squares fit of several of the observed winter patterns with a plume model yields average sediment mass flux lower bounds of 3.2 × 10?3 gm/cm/sec and 1.7 × 10?1 gm/cm/sec for ‘typical’ and extreme winter storm activity. |
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