Gravity Currents and Internal Bores in Lake Champlain

Saylor, J. H., Miller, G., Hunkins, K., Manley, T. O., & Manley, P. (1999) Gravity Currents and Internal Bores in Lake Champlain. In T. O. Manley & P. L. Manley (Eds.), Lake Champlain in Transition: From Research Toward Restoration (pp. 135-155). Washington, D. C.: American Geophysical Union. doi: 10.1029/WS001p0135

The shape of lake basins, with a large variety of configurations, plays a strong role in determining the current and circulation patterns within them. Elongated and narrow basins such as Lake Champlain can exhibit extremely large thermocline displacements and oscillations in response to wind forcing during seasons of density stratification. Time series of currents and temperature variations in Lake Champlain were recorded during the season of thermal stratification for three consecutive years. The measurements were made using arrays of Acoustic Doppler Current Profilers and thermistor chains moored along the lake’s thalweg. The long axis of the lake is oriented approximately north-south and is nearly 120 km long. The lake is about 6.3 km wide and has a mean depth of about 30 m. The depth decreases monotonically toward its north end from a maximum depth of 120 m at a location in the south. During seasons of weak thermal stratification in early summer and fall, strong winds from the south were observed to transport much of the less dense surface layer toward the north end of the basin and cause upwelling in the south. The resulting density distribution is similar to that observed in a lock exchange flow. A gravity current flows northward along the lake floor after the wind stress relaxes. The propagation of the current was monitored as it progressed through instrument moorings placed in the lake’s shoaling north end. Evolution of the gravity currents into bore-like waves traveling on weak near bottom stratification occurred at the northernmost measurement location.