Record ice cover on Lake Superior in 2014: Observations and implications

English Abstract:

Record-breaking cold in the Laurentian Great Lakes region during the winter of 2013-2014 resulted in abnormally long and intense ice cover on Lake Superior. The ice climate on Superior fell well outside the recent range of observed variability. Mooring observations from three locations in the western, central and eastern portions of the lake provide insight into the behavior of the lake during heavy ice cover. Surface heat fluxes were dramatically dampened during the season, and the character of the circulation in the upper water column changed dramatically. Observations of ice drift velocities were made using an ADCP, showing that ice drift direction was consistent with local winds, and ice drift speeds were a consistently about 3% of wind speeds across a wide range of wind speeds. This close coupling suggests that the force balance on the ice is a simple balance between wind and water drag. Ice keels of 6m thickness occurred on a regular basis throughout the season, and ice keels of up to 12m depth were observed. The impact of the high ice cover was felt through the remainder of the year, with the onset of stratification delayed in the lake until early to mid-August, resulting in a short, cool summer season.