An Analysis of Subtidal Current Fluctuations in the Middle Atlantic Bight

Hsien Wang Ou Woods Hole Oceanographic Institution, Woods Hole, MA 02543

Search for other papers by Hsien Wang Ou in
Current site
Google Scholar
PubMed
Close
,
Robert C. Beardsley Woods Hole Oceanographic Institution, Woods Hole, MA 02543

Search for other papers by Robert C. Beardsley in
Current site
Google Scholar
PubMed
Close
,
Dennis Mayer Atlantic Oceanographic and Meteorology Laboratories., NOAA, Miami, FL 33149

Search for other papers by Dennis Mayer in
Current site
Google Scholar
PubMed
Close
,
William C. Boicourt Chesapeake Bay Institute, The Johns Hopkins University, Baltimore, MD 21218

Search for other papers by William C. Boicourt in
Current site
Google Scholar
PubMed
Close
, and
Bradford Butman U.S. Geological Survey, Woods Hole, MA 02543

Search for other papers by Bradford Butman in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Subtidal current fluctuations in the Middle Atlantic Bight are examined from current-meter data collected in 1975 and 1976. Spectral analysis provides evidence for both locally wind-forced response and free waves that propagate downshelf3 which are not correlated with the local wind. A simple empirical model has been constructed to fit two linearly independent plane waves to the observed current spectra. Application of the model to the current data obtained at a pair of stations in the New York Bight during the period of 26 October 1975 to 4 April 1976 indicates that the two waves propagate in opposite directions along the coast, and with the additional evidence from rotary-coefficient calculations, it is suggested that they correspond to the forced and free waves speculated upon earlier. The noise level is a free parameter in the model and is determined by adjusting the phase speed of the forced wave to the translation speed of the observed wind field. This gives a 526 km day−1 phase speed for the free wave, and the forced wave, free wave and noise compose ∼41, 39 and 20% of the total variance.

Abstract

Subtidal current fluctuations in the Middle Atlantic Bight are examined from current-meter data collected in 1975 and 1976. Spectral analysis provides evidence for both locally wind-forced response and free waves that propagate downshelf3 which are not correlated with the local wind. A simple empirical model has been constructed to fit two linearly independent plane waves to the observed current spectra. Application of the model to the current data obtained at a pair of stations in the New York Bight during the period of 26 October 1975 to 4 April 1976 indicates that the two waves propagate in opposite directions along the coast, and with the additional evidence from rotary-coefficient calculations, it is suggested that they correspond to the forced and free waves speculated upon earlier. The noise level is a free parameter in the model and is determined by adjusting the phase speed of the forced wave to the translation speed of the observed wind field. This gives a 526 km day−1 phase speed for the free wave, and the forced wave, free wave and noise compose ∼41, 39 and 20% of the total variance.

Save