Persistent frigid temperatures this winter across the Mid-West and Northeast have caused many rivers and lakes to freeze.  These include the Great Lakes – the largest group of fresh water lakes on the planet.

According to NOAA’s Great Lakes Environmental Research Laboratory, 91.8% of the Great Lakes are currently covered with ice.  That is the second highest percentage on record.  The largest was 94.7% in 1979. On average, peak ice coverage each winter is roughly 51%.

This extensive ice cover has its pluses and minuses.  On one hand, it has reduced the amount of lake effect snow – the heavy precipitation produced when cold air blows across the expansive and relatively warm lake water.  When the lakes are frozen, moisture cannot be evaporated and this process shuts down.  On the other hand, it has slowed shipping traffic, which has economic impacts.  Also, given their massive size, the frozen lakes will likely keep regional temperatures cooler than average this spring.

While this year’s ice cover on the Great Lakes is near record-breaking, researchers say the ice extent varies annually and that there has been an overall decline since the early 1970’s.

Ice covers more than 90% of the Great Lakes.                                                                                      Image Credit: NOAA/Great Lakes Environmental Research Laboratory.