An ice‐cover climatology for lake erie and lake superior for the winter seasons 1897–1898 to 1982–1983

Abstract

AbstractObservations of mid‐lake Great Lakes ice cover are sparse prior to the decade of the 1960s. In an effort to provide an historical perspective of mid‐lake ice cover back to the turn of the century, daily average ice cover for Lakes Erie and Superior over 86 winters (1897–1898 to 1982–1983) was reconstructed using empirical‐statistical ice‐cover models developed in an earlier study. Long term average maximal monthly ice cover occurs in February and is 68 per cent for Lake Erie and 40 per cent for Lake Superior. Mid‐lake ice formation occurs about 1 month earlier on both lakes during severe winters. Average maximal monthly ice cover during severe and during mild winters is 95 per cent and 14 per cent for Lake Erie, 87 per cent and 17 per cent for Lake Superior. Severe winters are associated with lower 700‐mbar heights over the eastern USA compared with mild ice‐cover winters. Analysis of total winter ice cover indicates three ice cover regimes: (i) a high ice‐cover regime from the late 1890s to early 1920s; (ii) a low ice‐cover regime from the early 1920s to late 1950s; and (iii) a high ice‐cover regime from the late 1950s to the early 1980s. Ice‐cover climatologies developed during the 1960s and 1970s are not representative of ice covers in the low ice‐cover regime of the 1920s to late 1950s. Spectral analysis of the reconstructed total winter ice cover suggests interannual variations in ice cycles that correspond with the 2–3‐year interannual variation in atmospheric variables known as the quasi‐biennial oscillation.