The invention of the ADCP revolutionized studies of coastal circulation worldwide.
Working from moving vessels, ADCP operators measure continuous transects of
full-depth current profiles, often around consecutive circuits throughout a tidal
cycle. If each circuit is treated as a snapshot, then it should be completed before
the current field changes significantly due to tidal variation.
Coastal waters receive discharge and runoff from land—both directly and through
estuaries and inlets. This input has come under scrutiny due to deteriorating
marine ecosystems, worsened by pollutants and excessive nutrient loading.
Quantifying how effluent and water properties are transported and spread will
help advance understanding of their impact on coastal waters.
To address these goals, small autonomous underwater vehicles (AUVs) can
replace boats in coastal surveys, observing both flow fields and water properties
continuously and concurrently—for instance, while tracking effluent plumes or
river discharge.
Vehicles fitted with Teledyne RDI DVLs carry an embedded ADCP, which can
measure coastal currents at many depths simultaneously—above and below the
vehicle if a dual head is installed—while the AUV flies at a constant depth.
The DVL’s pinpoint positioning improves not just the vehicle’s trajectory but the
quality of data and images gathered at high sampling rates. Transects of ADCP profiles collected during spatial surveys
enable end-users to be better informed in order to describe
local circulation patterns and to assess the mechanisms driving
ocean processes. As well, maps of ADCP-based velocity fields
permit detailed comparison with output from coastal circulation
models, allowing for validation, calibration, and even refinement
of the models.
