Ocean tides and weather-induced bottom pressure fluctuations in the middle-Atlantic bight

Abstract

Five bottom pressure gages were deployed.in the Middle-Atlantic Bight during the late winter of 1974. Analysis of the resulting pressure ser. ies and neighboring i:oastal 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 significan y larger than alongshore gradient ..t• variations. Som e consequences of these large weatherqnduced grad•efit fluctuations on the shelf circulation are discussed.

The kinematics and dynamics of the New England continental shelf and shelf/slope front

“…The record for 13 is only 14 days long, while all the rest are approximately 32 days long. Alongshore length scales estimated from tide gauge records for this period can be as large as 1000 km (Beardsley et al, 1977) for periods of 2 to 7 days. It seems then that alongshore advection effects are negligible even though the alongshore flow is much stronger than the cross-shelf flow.…”

“…Another reason that the current does not always behave as one would expect relative to the wind stress is that the shelf currents also contain a significant amount of inertio-gravitational wave motion. Beardsley et al (1977) and Munk, Snodgrass, and Carrier (1956) have demonstrated the presence of edge waves of approximately 6 hour periods, initiated by wind events, in the presssure records of the Mid-Atlantic Bight. In this thesis we have demonstrated the existence of oscillations on the shelf/slope front about its mid-depth position with periods of 3 1/2 to 4 days.…”

“…A detailed description of the energy distribution of the SSP fluctuations is contained in Beardsley et al (1977). Figure 2.17 shows the low passed SSP record from mooring 2 and Figure 2.18 is the spectrum of this record.…”

“…Results from experiments combining hydrographic surveys with current meter deployments lasting a month or more for the Mid-Atlantic Bight region are given by: Boicourt (1973), Beardsley and Butman (1974), , Boicourt and Hacker (1975), Beardsley et al (1977), Scott and Csanady (1976. As a result it appears that the alongshore transport to the west and southwest inside the 100 m isobath is roughly constant from south of New England to the Chesapeake.…”

A survey of strong high-frequency sea level oscillations along the US East Coast between 2006 and 2011

“…A number of studies document this shelf as a place where long ocean waves are atmospherically generated (Yankovsky, 2008;Churchill et al, 1995). Both generation and propagation of edge waves along the US coastline have been documented several times during the last 60 yr (Munk et al, 1956;Greenspan, 1956;Beardsley et al, 1977). Tropical cyclones moving northward are usually the principal generating source of these coastal waves (Yankovsky, 2008(Yankovsky, , 2009).…”