What is the Role of Tidal Mixing in Shallow Seas?

Description of Project

How does the mixing of scalars and momentum occur in the ocean is one of the most elusive questions in physical oceanography, with direct implications for dispersion of pollutants and biogeochemistry in general. Ocean mixing is traditionally associated with winds and tides, but the details of the mixing process are difficult to apprehend, often because small scales and non-linearities are involved.

Barotropic tides in shallow seas are characterized by relatively strong currents, whose patterns are highly influenced by the variable bathymetry and the bottom friction. Tidal currents can also interact with the stratification [1], mean flow, and sea ice [2]. This leads to a rich palette of processes through which barotropic tides contribute to the advection and mixing of scalars and momentum.

My studies combine in situ observations (currentmeter records, and pressure gauge records, which are often available) with 3-D ocean modeling, in order to examine the relative importance of these tidal interactions in ocean mixing.

Normal modes of Hudson Bay
Figure 1: The three normal modes that are closest to the main tidal constituent (M2, period of 12.42 hours). The 12.3 hours mode is strongly excited by the M2 tide and produces the World's second highest tide in Leaf Basin (Ungava Bay, Québec). See Arbic, St-Laurent, Sutherland and Garrett (2007).


  1. Simpson, J.H., J. Brown, J. Matthews, and G. Allen, 1990. Tidal Straining, Density Currents, and Stirring in the Control of Estuarine Stratification. Estuaries, vol.13, no 2, p.125-132.
  2. St-Laurent, P., F.J. Saucier, and J.-F. Dumais, 2008. On the modification of tides in a seasonally ice-covered sea. J. Geophys. Res., 113, C11014, doi:10.1029/2007JC004614, preprint.
  3. B.K. Arbic, P. St-Laurent, G. Sutherland, and C. Garrett, 2007. On the resonance and influence of the tides in Ungava Bay and Hudson Strait. Geophys. Res. Lett., 34, L17606, doi:10.1029/2007GL030845.
  4. Newton, A. 2007. Tidal Timing. Nat. Geosci. doi:10.1038/ngeo.2007.13.