EFFECTS OF THE GULF STREAM ON NEARSHORE WAVE CLIMATE

R.J. Lai, S.L. Bales

Abstract


Large scale ocean currents, such as the Gulf Stream, Kuroshlo, Peru Current, Agulhaus Current, etc., strongly modify the surrounding wave characteristics. As the Gulf Stream moves along the Continental Shelf of the southeast coast of the United States, the local ocean environment is divided into three wave climatic regimes. They are the offshore, the Gulf Stream, and the nearshore regimes. The nearshore zone is bounded by the land to the west and the Gulf Stream to the east. The distance between land and the Gulf Stream varies from 10 to 60 miles. Most of the waves in this regime are generated offshore and cross the Gulf Stream. The correlation of local wind and waves in the nearshore regime is poor except in the presence of a persistent onshore storm. A semi-empirical approach has been developed to compute the nearshore wave climate. The hindcast/forecast directional waves from the Spectral Ocean Wave Model (SOWM) of the Navy Fleet Numerical Oceanography Center have been used as the source of the initial offshore wave conditions. After crossing the Gulf Stream, which is assumed to be a uniform current with a velocity of 2 m/s, the waves are either refracted to the nearshore regime or reflected to the offshore regime following ray theory. The onshore waves in the nearshore zone are confined to the sector from 30 to 150 degrees. The computed results are then compared with measured data with good agreement. In summary, the Gulf Stream acts as a barrier to damp long waves and to regroup short waves. The refraction of long waves can be predicted by using ray theory. Further field experiments are needed to quantify the variation of the Gulf Stream and to investigate the interaction with approaching long waves and local wind generated short waves.

Keywords


Gulf Stream; nearshore waves; wave climate

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