Watch four decades of Great Lakes ice cover flash before your eyes

A Michigan-based laboratory has turned decades of careful research on Great Lakes ice coverage, into an animation that flashes before your eyes in a matter of seconds. 

The animated map shows peak ice coverage on the Great Lakes from the early 1970s, to present day. On years with record high ice coverage, the lakes appear almost completely white, and on milder years with very little ice coverage, the image turns to a dark blue. 

The graph bars that appear at the bottom show the percentage of ice cover, averaged across the Great Lakes, for each year.

One of the main takeaways for viewers, is just how unpredictable ice on the lakes can be, said Drew Gronewold, a hydrologist at the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory, which created the animation. 

"Change can occur very rapidly on the Great Lakes, and often in ways that are not anticipated," he said. 

For example in 2014, ice cover came close to 100 per cent, an "extremely rare" occurrence. 

'The million dollar question'

On average, there has been less ice cover on the lakes since the late 1990s, said Gronewald, but how closely that trend is tied to climate change is still "the million dollar question." 

"Some of the changes in ice cover are certainly linked to changes in regional air temperature," he said, but some changes are due to other factors including regional climate patterns such as El Nino, which are hard to predict but can have dramatic effect. 

"That makes it very hard to point out, and look at a long-term trend, or a pattern of ice cover from year to year and diagnose it entirely according to global climate change," said Gronewold. 

"Ice cover is highly variable from year to year, and that the factors that can drive ice cover can be very hard to predict."