Effective monitoring of environmental changes requires sustained and widespread observations. To meet this challenge, some researchers have taken advantage of “vessels of opportunity” that continually repeat a commercial route. Installing Acoustic Doppler Current Profilers (ADCPs) on commercial vessels provides a cost-effective way to take sustained current measurements with high-spatial resolution along a specific transect.
OVERVIEW
Effective monitoring of environmental changes requires sustained
and widespread observations. To meet this challenge, some researchers have taken advantage of “vessels of opportunity” that continually
repeat a commercial route. Such studies have examined algal blooms,
estimated fluxes (water, heat, sediments), and validated satellitesensed observations.
Installing Acoustic Doppler Current Profilers (ADCPs) on commercial
vessels provides a cost-effective way to take sustained current measurements with high-spatial resolution along a specific transect. One
caveat is that, at times, severe interference by bubbles and vessel
noise can corrupt the ADCP profiles. Additionally, commercial vessels
sometimes deviate from their regular route due to traffic or weather.
In 2014, researchers in Washington State installed ADCPs on two public
ferries that run continual (daytime) transects across the entrance to
Puget Sound. Strong flows command this chokepoint where estuarine
waters are exchanged with the ocean. This project aims to improve
understanding of the environmental influence of these flows,
ranging from circulation patterns and low-oxygen intrusions to tidal
energy resources.
The four-year data set analyzed by the researchers contains at least
twenty transects per day, even more in summer when two ferries are
in service. The ferries’ six-kilometer route across Admiralty Inlet spans
steep topography that channels the flow. The vessels run at 6 m/s,
cutting through currents that can exceed 3 m/s and have strong
spatial gradients.
Pinging at 2 Hz, the 300 kHz ADCPs are programmed for 2 m vertical resolution and
averaged over 15-s ensembles. Thus the recorded current profiles are separated by
90 m (nominal) along the transect. Data are uploaded each day to a public server.
