CHARACTERISTICS OF TURBULENT CROSS AND ALONGSHORE MOMENTUM EXCHANGES DURING A THERMAL BAR EPISODE IN LAKE-ONTARIO

Time series flow data obtained during the thermal bar episode of 17 Ap ril to 24 May 1990 in Lake Ontario are analyzed to provide a kinematic description of the coastal flow and cross-margin exchange characteris tics. A thermal bar is a shore-parallel front which separates descendi ng waters at or near the fresh water temperature of maximum density (4 degrees C) during Spring and Fall seasons. Thermal bars are important because of their influence mixing, cross-shore exchanges, and the var iability of biotic factors in coastal zones. The analysis shows that c ross-frontal exchange coefficients, K-y, are nearly constant and consi stently smaller than along-frontal counterparts, K-x, Moreover, these exchange coefficients are several orders of magnitude smaller than typ ical coastal and oceanic values in the absence of the bar. The turbule nt kinetic energy represents less than 6% of the total kinetic energy in the flow. These results suggest that small-scale horizontal fluctua tions and cross-frontal turbulent momentum exchanges are severely inhi bited in the spring during the thermal bar.