Thermal bar is an important phenomenon in large, temperate lakes like Lake\ud
Ontario. Spring thermal bar formation reduces horizontal mixing, which in turn, inhibits the\ud
exchange of nutrients. Evolution of the spring thermal bar through Lake Ontario is\ud
simulated using the 3D hydrodynamic model Environmental Fluid Dynamics Code (EFDC).\ud
The model is forced with the hourly meteorological data from weather stations around the\ud
lake, flow data for Niagara and St. Lawrence rivers, and lake bathymetry. The simulation is\ud
performed from April to July, 2011; on a 2-km grid. The numerical model has been\ud
calibrated by specifying: appropriate initial temperature and solar radiation attenuation\ud
coefficients. The existing evaporation algorithm in EFDC is updated to modified mass\ud
transfer approach to ensure correct simulation of evaporation rate and latent heatflux.\ud
Reasonable values for mixing coefficients are specified based on sensitivity analyses. The\ud
model simulates overall surface temperature profiles well (RMSEs between 1-2°C). The\ud
vertical temperature profiles during the lake mixed phase are captured well (RMSEs <\ud
0.5°C), indicating that the model sufficiently replicates the thermal bar evolution process. An\ud
update of vertical mixing coefficients is under investigation to improve the summer thermal\ud
stratification pattern. Keywords: Hydrodynamics, Thermal BAR, Lake Ontario, GIS