Why Won't Lake Ontario Freeze Over?

The brutal winter the eastern half of North America experienced this year took a heavy toll on the continent's Great Lakes. Since late December when the first "Polar Vortex" descended and wreaked havoc, ice cover on the Great Lakes skyrocketed and topped out in the 80% range in February. It has, for the most part, stayed there ever since.

News broke this past Monday that the latest cold spell pushed the Great Lakes dangerously close to the record for most ice cover ever observed on the five collective bodies of water, reaching 90% on March 3, nearing the all-time observed ice cover of 94% set in 1994.

There is one glaring exception: Lake Ontario.

Why Won't Lake Ontario Freeze Over?

[Image via GLERL/NOAA]

Lake Ontario, nestled between southern Ontario and upstate New York, has a reputation for never really freezing over during the winter. During the 2011-2012 season, only 3% of the lake's surface froze. The most ice cover on Lake Ontario in the last 6 years happened this year, when roughly 45% of the lake froze over on multiple occasions.

What gives?

A reporter for the Toronto Star asked a climatologist with Environment Canada (Canada's version of the National Weather Service) why Lake Ontario has so little ice during even the harshest of winters. The expert listed three reasons as to why the lake sees less freezing than its four counterparts:

  • Lake Ontario is deep, so it retains more heat than the other four lakes.
  • The Niagara River feeds water into Lake Ontario from Lake Erie, providing agitation which keeps the water's surface from freezing.
  • Its geographic location protects it from the brutal temperatures that Lake Superior and northern Lake Michigan experience most of the winter.

Why Won't Lake Ontario Freeze Over?

[Image via CIMSS/University of Wisconsin]

The fact that Lake Ontario so rarely develops ice cover, as well as its nearly east-west orientation, gives the eastern shore of the lake one of the worst lake effect snow seasons on Earth.

The warm waters can heat air near the surface of the lake through conduction and allow the air to rise into the extremely cold atmosphere above, creating enough instability to create intense bands of lake effect snow (like the one pictured above). Ice on the surface of the water literally caps the fuel source for lake effect snow, preventing the air from warming up and rising and cutting off lake effect snow until the ice melts.

Since Lake Ontario rarely freezes over, areas east of Lake Ontario in upstate New York average over 100 inches of snow per year, with seasonal totals exceeding 200 inches during the worst seasons.

The recent cold spell seems to have done the trick to get a significant portion of Lake Ontario to freeze over, but the number fluctuates daily and with spring somewhere around the corner, the ice won't last long.

[Image of Toronto/Lake Ontario via Getty]