An Experimental Investigation of Wave Measurements Using a Dual-Beam Interferometer: Gulf Stream as a Surface Wave Guide
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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A dual-beam interferometric synthetic aperture radar measures remotely two radial components of the ocean surface current from a single flight pass. Combining two passes over the same area, all three orthogonal components of the surface velocity can be retrieved. An experiment is conducted near the Gulf Stream CS boundary. A sharp change of the surface velocity of about 1 ins over a 500 m lateral distance is measured. The wind and wave condition is dominated by a l4-s swell system and low wind velocity. The wave variance inside CS is about twice the wave variance outside the Cs in the present data set. The difference in the wave variance is considerably higher than that can be expected from wave-current interaction. An ocean current system with strong shears such as the CS is a wave guide and can trap waves with the right combinations of wavelengths and propagation directions. Numerical calculations suggest that the wave properties of the data set may satisfy the conditions of wave trapping by the CS. The standing wave pattern on the CS side of the sharp velocity front, indicative of the long swell bouncing off the current front, also offers support for the wave guide hypothesis. In this respect, the Gulf Stream can be considered the natures hydraulic breakwater that can attenuate about 50 of the incident wave energy generated by storms. Its role in protecting the U.S. coastlines iii the Atlantic Ocean cannot be overstated.
- Physical and Dynamic Oceanography