Influence of cold season climate variability on lakes and wetlands in the Great Lakes region

The role of cold season climate variability on lakes and wetlands in the Great Lakes region of the United States was examined over a period of 91 years (1917-2007) using the variable infiltration capacity (VIC) land surface hydrologic model. Statistically significant trends in observed cold season precipitation and air temperature indicated that both have significantly increased during the last 91 years. Results also showed that despite the significant increase in the cold season (December-May) precipitation, snowfall is significantly decreased during the period 1917-2007, suggesting the change in the distribution of the cold season precipitation. Both total runoff and evapotranspiration during the spring (March-May) season are increased; however, the trend associated with evapotranspiration was significant. These changes in cold season precipitation and temperature resulted in an increasing trend in domain-averaged fractional inundation extent during the spring season. The inundation extent of lakes and wetlands during the spring season showed sensitivity to periods of extreme climate. Driest years and those with the lowest snowfall resulted in the lowest inundation extents, while years with highest snowfalls resulted in the greatest inundation extents. Five year composites of extreme dry; wet; cold; warm; low snow; high snow; low snow, high temperature; and high snow, low temperature showed the mean domain average fractional inundation extent in spring to be 0.17, 0.22, 0.23, 0.20, 0.17, 0.24, 0.21, and 0.22, respectively. The fractional inundation extent in spring was significantly correlated with snowfall, the amount of snowmelt in the cold season, and the total runoff (surface runoff + base flow) in spring. Spring inundation extent was negatively correlated with the cold season air temperature, suggesting that higher air temperature could lead to lower inundation.