Interannual Variability of the Thermal Components and Bulk Heat Exchange of Great Slave Lake

Abstract

Intensive year-round observations (1998–2003) revealed that Great Slave Lake is highly responsive to variations in both short-term meteorological and longer-term climatic conditions. The lake is dimictic and exhibits spatial and temporal variability in air temperature and wind speed that impacts water surface temperature and lake heat flux. Storm events with high winds were responsible for short-term highly dynamical responses of the lake, with deep vertical mixing of temperature affecting thermal stratification characteristics. Significant interannual variability was observed. The longest ice-free period over a 16-year period occurred in 1998 (213 days) compared to a cooler year in 2002 (174 days). Maximum surface temperature was in 1998 (21.2 °C) compared to 2002 (14°C). Simulation of surface temperature using a 3-D hydrodynamic model demonstrated marked nearshore and offshore temperature differences. Variation of the 8 ° C isotherm effectively demonstrated interannual variability in the lake heating. Annual heat content ranged from 2.61 × 10¹⁹ J in 1998 to 2.13 × 10¹⁹ J in 2002. Five-year mean heat content maximum was 2.24 × 10¹⁹ J. The bulk heat exchange, ranging between 267 W m^-2 and-338 W m^-2, compared well with conventional heat flux calculations at Inner Whaleback Island located in the central basin of the lake.