Recent Variations in Great Lakes Ice Cover and Relationships to Antecedent Atmospheric Conditions

Skillful 30-day forecasts of winter ice conditions on the Great Lakes could be valuable to a wide variety of regional socio-economic activities, particularly merchant shipping which is largely restricted by the presence of ice. Recent analyses suggest interannual variations in ice conditions are strongly related to coincident atmospheric conditions, including low-frequency annular modes, yet little is known about the relationship between ice conditions and antecedent atmospheric conditions. Utilizing monthly accumulations of freezing degree days (FDD) as a proxy for ice conditions, interannual variations in atmospheric conditions are compared with accumulated FDDs from 1950 through 1999. Results suggest variations in antecedent Pacific-North American (PNA), Southern Oscillation Index (SOI), and North Atlantic Oscillation (NAO) indices, in combination with preceding FDD accumulations, show promise for increasing the skill of 30-day forecasts of Great Lakes ice conditions.