CROSS-LAKE VARIATION OF PHYSICAL LIMNOLOGICAL AND CLIMATOLOGICAL PROCESSES OF GREAT SLAVE LAKE

Abstract

Cross-lake observations of meteorology, solar and longwave radiation, surface waves, and thermal structure were conducted in the main-lake section of Great Slave Lake as contribution to the Mackenzie Basin Global Energy and Water Cycle Experiment (GEWEX-MAGS-I) in the summer of 1998 and the winter of 1998/1999. Analysis of the principal meteorological variables showed significant nearshore and midlake differences especially after the period of ice break-up in June to mid-July. In one case, high winds generated wind stresses up to 0.45 N m^-2 and significant wave heights up to 4 m. Thermal structure varied between nearshore and midlake regions. High winds significantly disrupted developing thermal stratification in early spring by deepening the midlake upper mixed layer from 5 to 20 m depth. Evaporation was highly episodic, varied up to eight times between nearshore and offshore stations. During spring, much of the energy receipt was used to heat the lake. During summer, the total surface heat flux was significantly affected by the episodic evaporative flux. Heat content analyses showed that rapid lake heating occurred from June to early August (approximately 3.395 × 10¹⁷ J d^-1) followed by gradual heat loss from mid-August through to the end of December (approximately 1.730 × 10¹⁷ J d^-1). The annual range of heat content was 2.543 × 10¹⁹ J. [Key words: over-lake meteorology, surface waves, evaporation, heat budget, thermal responses, heat content, northern lakes.]