National Water Research Institute, Canada Centre for Inland Waters
867 Lakeshore Rd., Burlington, Ontario, Canada, L7R 4A6

*Corresponding author: william.schertzer@ec.gc.ca

Summary

   Principal features of the thermal structure of Lake Erie are described along with an assessment of trends, variability and potential changes. We discuss the historical perspective of observations, long-term temperature and heat storage characteristics resulting from radiative and turbulent heat exchanges, and primary characteristics of the annual thermal cycle including the thermal bar, thermocline dynamics and time of over-turn. The long-term data record clearly demonstrates that there are years with a lack of data representativeness both spatially and temporally. Such problems make it difficult to rely on the observational record alone for analysis of temperature related priority issues. Limitations in spatial and temporal databases necessitate the development and application of a hierarchy of thermal models for simulating / forecasting lake temperature fields. Surface temperature observations do not show a statistically significant trend, however, some years, especially in the 1990s, do have large departures (e.g. 5-7 C^o) from the long-term mean temperatures. More research is required to establish the degree of correspondence between these large departures and such factors as ENSO events or anthropogenic changes. Preliminary research combining thermal models with climate warming scenarios (e.g. climate analogs; 2 x CO₂ GCM scenarios; climate transposition scenarios) have indicated that the thermal structure of Lake Erie can be significantly changed. Such changes include, for example, reduction in ice cover, longer stratification season and a possible change from dimictic to monomictic conditions, which have implications for other ecosystem components, water quality and many priority issues related to this lake. Based on the climatological record of surface temperatures, the near-term period (i.e. 3-5 years) in Lake Erie may experience variable temperatures with extremes greater than 2C^o from the long-term mean similar to the 1990s. Longer-term projections, based on climate change modelling, indicate that with increasing atmospheric concentrations of “green-house gases” significant changes to the lake thermal components are possible. Uncertainties and limitations of data and modelling are assessed with recommendations for future research.