Lakes Topozero, Segozero, Rugozero, Vigozero, Syamozero, Vodlozero, Tulmozero and Onego are located in the northern, central and southern parts of Karelia and have significantly different morphometric characteristics (Fig.
This relationship is best seen for the large deep lakes: Onego (r = -0.57), Segozero (r = -0.46) and Topozero (r = -0.43) (Fig.
Lake Segozero is an exception: it freezes in December, nearly a month later than other lakes.
Only for lakes Segozero and Onego it is better to use average values of air temperature from November to December in the regression analysis for the date of their freezing.
This effect is more evident in large deep lakes, such as Lake Segozero (Fig.
The differences between the observed and calculated timing of ice events are greatest for the large and deep Lake Segozero. Dispersion and extreme values estimated for all lakes were slightly less than the measured values.
However, a significant linear trend (p < 0.05) was obtained only for the formation of ice in deep Lake Segozero that freezes 30-40 later than the other lakes.
Over the past 10 years, the duration of ice cover decreased by 11-16 days, for lakes Onego and Segozero by more than 20 days compared to the average for the entire 60-year period.