Kincaid's coastal physical oceanography group has a number
of field studies running within Narragansett Bay and its
tributaries. As part of a Navy-funded study to characterize
Coddington Cove (just north of the Newport Bridge, on the
east side of the Bay's East Passage), we have been studying
the dynamics of the cove. Circulation patterns are measured
using a ship-mounted, RD Instruments 1200 khz Broadband
Acoustic Doppler Current Profiler (or ADCP). The ADCP sends
an energy pulse into the water. Sound energy is reflected
off of particulate material in the water column and the ADCP
measures the doppler shift
on the returning energy pulse to determine velocity of
the reflecting particle (and the water carrying it) relative to the boat's motion. By listening
at different intervals (or gates) the ADCP measures velocities
from different water depths. This first figure shows a map of
Coddington Cove and the ADCP survey lines (called transects).
The transect across the mouth (#1) provides information on exchange
patterns and fluxes between the cove and Narragansett Bay. The
internal transects (#2-#6) provide information on the general circulation
patterns and energetics within the Cove (e.g., mapping the low energy
regions where pollutants are likely to collect). Field surveys
have been run during high and low amplitude tides and during periods
of high and low runoff. An interesting outcome of the surveys
is the definition of a net, anti-clockwise circulation pattern
within the cove. This pattern is shown in this contour map
of velocity across the mouth transect, (red=flow into the cove; blue=flow out of the cove). A strong outflow
core is seen at the north end of the transect.
Surprisingly, this general flow pattern exists over flooding and ebbing tidal
conditions and during slack water periods. The flow pattern can be
overcome by the onset of a strong wind event as is shown in this
sequence of contour plots at the mouth. As the wind increases, the
flow evoles into a vertically stratified, 2-layer pattern.
