FY 1977

Ocean tides and weather induced bottom pressure fluctuations in the Middle-Atlantic Bight

Beardsley, R.C., H. Mofjeld, M. Wimbush, C.N. Flagg, and J.A. Vermersch, Jr.

J. Geophys. Res., 82, 3175–3182, doi: 10.1029/JC082i021p03175 (1977)

Five bottom pressure gages were deployed in the Middle-Atlantic Bight during the late winter of 1974. Analysis of the resulting pressure series and neighboring coastal tide gage series shows that tides are the dominant pressure signal in this section of the continental shelf. Most of the remaining pressure fluctuations appear to be forced by meteorological transients. During March 21, 1974, a developing cyclone moving up the coast excited a coherent group of sea level oscillations with characteristic periods of 5-7 hours, which are interpreted here as coastal-trapped edge waves. Spectra of the nontidal pressure series are red, however; most of the nontidal variability is caused by lower-frequency (subtidal) components. The subsurface pressure (SSP) fluctuations do appear coherent over the spatial extent of the array in the most energetic subtidal frequency bands, and estimates made of the relative horizontal SSP gradients indicate that cross-shelf gradient variations are significantly larger than alongshore gradient variations. Some consequences of these large weather-induced gradient fluctuations on the shelf circulation are discussed.