Lake Ice and Climate Change
The paper River and Lake Ice reviews freeze up and break up dates for lakes and rivers over the past 100 years. They found the average trend is we are loosing a about 12 days of ice season/century. If anything, that rate is likely to increase. This probably also means we are having more mid-winter thaws. That may or may not mean more snow free ice (depending on the effect on snowfall). EIther way it probably means more days of dodgy ice than we had in the past. As can be seen in the 2013 and 2014 season fatality reports, more warm weather correlates with more swimming.
The Environmental Protection Agency has posted a similar paper for a range of US lakes. The conclusions are similar.