Our field site was Beaufort Inlet in the Outer Banks of North Carolina. This aerial photo shows Bogue Banks (on the left), Shackleford Banks (on the right), and the surrounding estuarine complex. The inlet is about 1 km across. Depths range from about 15 meters in the navigation channel to less than 2 meters on the adjacent shoals.

The field program used a combination of moored and shipboard measurements. Moored instrument locations are denoted with magenta symbols. The moored CTD measured salinity, temperature and water level once per minute. In the center of the navigation channel we deployed a bottom mounted upward-looking ADCP. West of the channel we deployed a bottom mounted S4a electromagnetic current meter.

Seventeen cruises were made during the period from December 1997 and October 1998. Survey transects are shown in dark blue. CTD casts were made at the corners of the ADCP transects and are shown with blue open circles.

The cruises were conducted on the 8 meter R/V Parker. The vessel is fitted with DGPS, stainless steel davit, and a retractable boom for a shipboard ADCP.

During the ADCP surveys we made CTD casts (with a Seabird SBE-19) about once an hour to study changes in the density field during a tidal cycle.

Concurrent with the shipboard measurements, velocity profiles were collected with a bottom mounted ADCP. The figure below show a time series data from this instrument for about 6 days. The top panel is east-west velocity (cross-channel); the bottom panel is north-south velocity (along-channel). The vertical scale is depth and the horizontal scale is time. Colors indicate flow speed, with the warm hues being east and north, the cool hues are west and south. During this period, the velocity signal is strongly dominated by the semi-diurnal tide.

Spectra for ADCP mooring velocities. Top panel is the along-channel component and bottom panel is the cross-channel component. Color contour values are in units of LOG10 [(cm/s)2/cph]. Note the increase in power around 3.5-4.5 m.a.b. The channel sill is 5-6 m.a.b.

Tidal ellipse parameters for M2, M4, and K1