Factors influencing peak summer surface water temperature in Canada’s large lakes

Abstract

Seasonal water temperature data from 388 large Canadian lakes (area ≥ 100 km2) were used to develop improved empirical tools for forecasting the impacts of climate change on the magnitude (TP) and time of occurrence (JP) of annual peak surface water temperatures. Analyses of remotely sensed open-water temperatures with sinusoidal models produced estimates of TP and JP predominately better than other models. Those estimates were analyzed for lake and climate patterns. Linear mixed effects regression produced a significant model of TP with fixed positive effects for mean July and annual air temperatures and lake perimeter, but negative effects with mean July and annual percent cloud cover, mean annual precipitation, range of monthly mean global clear sky radiation, area, and elevation. Subsets of the estimates with mean, maximum, or Secchi depth values produced similarly significant models with negative depth coefficients. JP was relatively invariant but small, significant lake and climate effects were detected. The best models identified in our analyses will be useful tools for forecasting how climate change will alter aspects of the limnetic seasonal water temperature cycle that strongly influences the species composition and productivity of their fisheries.

Predicting open-water thermal regimes of temperate North American lakes

“…The range of J M was predicted well in this and previous studies; however, increasing prediction accuracy has been difficult (Minns and Shuter 2013;Minns et al 2018). J M consistently occurs around the same time each year (mean = 199.94, SD = 12.58, range = 74.67, Table S8, Fig.…”

“…Most of the lakes used in our study comprise a much smaller elevation range and are generally at much lower elevations than the lakes in these studies. The J M ETM from Minns et al (2018) lacked an elevation term and covered a similar elevational range to our study. Further, the standardized effect size for ln(elevation) was one of the smallest out of all predictors when it was included in the model.…”

“…Air temperature and lake morphometry were important for accurately predicting T MAX , which we expected as summer air temperature greatly affects peak lake surface temperature (Piccolroaz et al 2013;Magee et al 2016;Minns et al 2018). T MAX and ln(area) had a negative relationship, as larger lakes require more energy to heat up and the greater degree of epilimnetic mixing in larger lakes further increases the volume of water that needs to be heated up (Gorham 1964;Kettle et al 2004 Pilla et al (2018) showed that epilimnion temperatures in two Pennsylvanian lakes increased significantly during three decades of stable air temperatures alongside increases in precipitation and pH, which decreased water transparency.…”

The Distribution and Prediction of Summer Near-Surface Water Temperatures in Lakes of the Coterminous United States and Southern Canada

“…We found that the mean air temperatures at a lake of from seven to 10 days prior to and including the sampling day gave the best correlations between water and air temperatures ( Table 2). Many other investigators have also found relationships between air and water temperatures for annual [18], monthly [41] and daily [15,19,42] periods and peak summer temperatures [43]. Others have used longer time periods in their averages when working with one or a smaller group of lakes.…”

“…Hondzo and Stefan [45] used lake models based on climatic factors to predict the effects of climate change on the thermal properties of lakes in the north central United States. Robertson and Ragotzkie [46] used both mechanistic and empirical models to estimate changes in the thermal structure of moderate to large sized lakes in the United States and Canada while Minns et al [43] developed empirical models to forecast the impact of climate changes on the magnitude and time of occurrence of annual peak surface water temperatures of large lakes in Canada. This is important because others have indicated that lake surface summer water temperatures are warming worldwide over the past 25 years, with over 90% of observed lakes exhibiting warming trends since 1985 [5,6].…”