Julia C Mullarney, Stephen M Henderson


We present high resolution (25 mm spatial, 8 Hz temporal) profiles of velocity measured over a shallow tidal flat using pulse-coherent Acoustic Doppler Profilers mounted on surface drifters. The use of Lagrangian measurements mitigated the problem of resolving velocity ambiguities, a problem which often limits the application of high-resolution pulse-coherent profilers. Turbulent dissipation rates were estimated from second-order structure functions of measured velocity. Drifters were advected towards, and subsequently trapped on, a convergent surface front which marked the edge of a freshwater plume. Measured dissipation rates increased as a drifter deployed within the plume approached the front. A drifter then propagated with and along the front as the fresh plume spread across the tidal flats. Near-surface turbulent dissipation measured at the front roughly matched a theoretical mean-shear-cubed relationship, whereas dissipation measured in the stratified plume behind the front was suppressed. After removal of estimates affected by surface waves, near-bed dissipation matched the velocity cubed relationship, although scatter was substantial. Dissipation rates appeared to be enhanced when the drifter propagated across small subtidal channels.


drifters; turbulent dissipation; Lagrangian measurements; shallow flows; structure functions; pulse coherent profilers; tidal flats


Austin, J. and S. Atkinson. 2004. The design and testing of small, low-cost GPS-tracked surface drifters, Estuaries 27, 1026-1029.

Grant, W.D. and O.S. Madsen. 1986. The continental shelf bottom boundary layer, Annual Reviews of Fluid Mechanics 18, 265-305.

Henderson, S.M. and J.C. Mullarney. 2012.Wave mixed, wind-generated near-surface shear observed over a tidal flat, Continental Shelf Research

Johnson, D., R. Stocker, R. Head, J. Imberger and C. Pattiaratchi. 2003. A compact low-cost GPS drifter for use in the oceanic nearshore zone, lakes and estuaries, Journal of Atmospheric and Oceanic Technology 20, 1880-1884.<1880:ACLGDF>2.0.CO;2

Lhermitte, R. and R. Serafin. 1984. Pulse-to-pulse coherent Doppler sonar signal processing techniques. Journal of Atmospheric and Oceanic Technology, 1, 293-308.<0293:PTPCDS>2.0.CO;2

Lohrmann, A., B. Hackett, and L.-P. Røed. 1990. High resolution measurements of turbulence, velocity and stress using a pulse-to-pulse coherent sonar, Journal of Atmospheric and Oceanic Technology, 7, 19-37.<0019:HRMOTV>2.0.CO;2

Lohrmann, A. and S. Nylund 2008, Pulse Coherent Doppler Systems - How far can we push it? Proceedings of Current Measurement Technology Conference.


MacMahan, J., J. Brown and E. Thornton. 2009. Low-cost handheld global positioning system for measuring surf-zone currents, Journal of Coastal Research 25, 744-754

Monin, A.S. and A.M. Yaglom. 1975. Statistical Fluid Mechanics: Mechanics of Turbulence, Volume 2, Dover, New York.

Mullarney, J.C. and S.M. Henderson. 2011. Hydraulically controlled front trapping on a tidal flat, Journal of Geophysical Research, 116,

Mullarney, J.C. and S.M. Henderson. A low-cost drifter designed for use with a mounted Acoustic Doppler Profiler in shallow environments, manuscript in preparation.

Schmidt, W.E., B.T. Woodward, K.S. Millikan, R.T. Guza, B. Raubenheimer and S. Elgar. 2003. A GPSTracked Surf Zone Drifter, Journal of Atmospheric and Oceanic Technology 20, 1069-1075.

Simpson, J.E. 1997. Gravity currents in the environment and the laboratory, 2nd edition, Cambridge University Press, Cambridge, UK.

Thomson, J. 2012. Wave breaking dissipation observed with SWIFT drifters, in press in Journal of Atmospheric and Oceanic Technology,

Wiles, P.J., T.P. Rippeth, J.H. Simpson and P.J. Hendricks. 2006. A novel technique for measuring the rate of turbulent dissipation in the marine environment, Geophysical Research Letters, 33, Zedel, L., A.E. Hay, R. Cabera and A. Lohrmann. 1996. Performance of a single beam pulse-to-pulse coherent Doppler profiler, IEEE Journal of Oceanic Engineering, 21, 290-297.

Full Text: PDF

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.