A long-term objective of nearshore oceanography is a
FIELD-TESTED COMMUNITY MODEL that
predicts the evolution of surface gravity waves propagating across the
continental shelf through the shoaling region and surf zone to the beach, and
the corresponding breaking-wave driven nearshore circulation, sediment
transport, and subsequent bathymetric change.
On many continental
shelves irregular bathymetry in water depths as great as 200 m causes large
gradients in the wave field outside the surfzone. The steep topography of
Scripps and La Jolla Submarine Canyons in Southern California
produces dramatic changes in wave energy over alongshore distances of only a
few 100 m, resulting in complex nearshore circulation and morphological change
(see the photographs below).
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Aerial photograph of complex nearshore circulation near Scripps and La Jolla Submarine Canyons on the Southern California coast. There is a strong offshore flowing jet to the south (left) of the 340-m long Scripps Institution pier, as well as smaller jets, eddies, and meanders (eg, outside the surfzone (white foam) north of the pier). Recent rains resulted in a strong color contrast between muddy nearshore water and the clearer blue waters farther offshore. |
Close up of the circulation near the pier. The approximately 1 km long jet of muddy water (south (left) of the pier) is 10's of m wide at the offshore end. Smaller jets and eddies can be seen at the seaward edge of the surfzone (delineated by the white foam from breaking waves). |
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An offshore directed jet originating close to Black's Beach,onshore of the northern head of Scripps Submarine Canyon, a few km north of the Scripps Institution of Oceanography pier. |
Close up of the offshore flow near Black's Beach. The offshore tip of the jet has curled into a tight eddy that is being swept south (to the right) by alongshore flows. |
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Complex pattern of swell at Black's Beach near the northern head of the Scripps Submarine Canyon. Complex pattern of swell at Black's Beach near the northern head of the Scripps Submarine Canyon. Offshore (blue water), the swell crests were long, straight, and approximately parallel to the coastline. The two wave crests near the lower left-hand corner of the photograph are propagating at a large oblique angle relative to the shoreline, while adjacent waves approach the beach nearly parallel to the shoreline. |
Close up of the complex pattern of swell at Black's Beach near the northern head of the Scripps Submarine Canyon. Curving wave crests can be seen in the muddy water between the surfzone (white foam) and blue offshore water. Waves refracted by the complex canyon bathymetry can propagate at large angles to shore normal, and drive complicated surfzone circulation. |