depth averaged currents by M2 phase
click for full res. animation

Regional ADCP Current Measurements

Shippagan Bay Survey 2003

John E. Hughes Clarke, Anya Duxfield and Beth-Anne Martin
Ocean Mapping Group
University of New Brunswick

Whilst the regional multibeam/sidescan/subbottom survey was being conducted, a pole-mounted 600kHz acoustic doppler current profiler (ADCP) was deployed to measure instantaneous current profiles beneath the vessel wherever she went. The aim was to make measurements of the currents field through the bay as a function of the M2 and K1 tides.  Nevertheless, it should be realised that during the ~ 40 day survey window, the tides ranged from neaps to springs, from dominantly diurnal to dominant semi-diurnal (see adjacent figure).

Nevertheless, this data acquisition could be carried out at no addition survey costs and allowed us to establish the typical direction and magnitude of currents in the Bay during the ebb and flood periods. Using this data we designed a series of 12.42 hour (M2 tide period) repetitve oceanographic sections. The exact survey sequenceand data density,  was dictated by  weather and seafloor data acquisition (80m line spacing).

In an attempt to randomise the observations as a function of phase of tide, we tried to survey every second line and return to do the intermediate lines ~ 7 days later (when the pahase of the tide would have shifted by ~ 1/2 M2 tidal period). This novel sampling approach ended up being redundant as the time disruptions  due to mechanical and weather delays ensured that the survey preceded in a pseudo-random manner anyway.

The animation above show depth average current vectors obtained, sorted by phase of the M2 tide. Should there be interst, we can put the source current data online in an appropriate manner.

back to Shippagan Survey Index

last modified Nov 14th by John  E. Hughes Clarke