At Cleveland Water, every day we are thankful to have a massive supply of fresh water at our doorstep. But during the polar vortex, we were thankful for a different reason.
Lake Erie and the other Great Lakes took some of the polar punch out of the arctic air mass that swept over the region. This was due to a property of water called heat capacity.
Heat capacity is the amount of heat energy that has to be applied or taken away for an object to change 1 degree of temperature. Everything that has mass – water, wood, metal, food, even humans – has a unique heat capacity.
Water has a very high heat capacity compared to other objects. This means it is much harder to change the temperature of water than it is to change the temperature of something like soil. In fact, water has to lose about three times as much heat as wet soil does to lower the temperature of water 1°C (1.8 °F).
When it comes to bodies of surface water, heat is lost through evaporation, which looks like steam rising off the lake. The steam rises and forms clouds. On January 30, Cleveland had sunny skies while massive clouds rolled offshore. As the nearshore waters lost heat and froze over, the clouds moved farther and farther offshore. On January 31, the clouds were gone.
In just a few days, Lake Erie went from around 40% ice cover to 95% ice cover, according to NOAA GLERL data. So for Lake Erie's surface ice to increase by more than 50 percentage points, the lake had to lose enough Joules of heat to power more than 2.6 billion 60-watt lightbulbs for 24 hours.
But if the 57-mile wide by 210-mile long body of water was not to Cleveland’s north, more heat would have been sucked from the land into the air – and temperatures in the Cleveland area would have been about 5.4 °F colder than the extreme lows we experienced.
So today, we thank the heat capacity of water for moderating Cleveland’s climate. Lake Erie keeps Cleveland’s summers cooler, our winters warmer, and in all seasons allows us to keep a virtually unlimited supply of clean and safe drinking water flowing to our customers.