You might never have seen pancake ice, but you can probably imagine it: a large area of cold water — maybe in the ocean or a big lake — covered in big lilypad formations of ice. Some people even say they look like deep dish pizzas. Whatever you want to liken them to, they're floating discs of ice that are circular and often raised on the edges — but how did they get that way?
Pancake ice can form in a couple ways, depending on the conditions. It can happen when a thin layer of ice and slush forms over the water and freezes solid, but is broken up by waves or other movement in the water. This ice may crack into big geometric-shaped pieces, but over time the movement of the water smashes these floating polygons together, rounding and raising the edges until they look like circular dim sum platters.
Extremely turbulent waters can also form pancake ice when it's very cold: Although the water is too choppy to form a sheet of ice, little granules of ice find their way to one another and freeze together, forming rotating disks of pancake ice that bob around on the surface.
Although this ice formation isn't all that common — it's generally found in the ocean, but when it forms in the Great Lakes, for instance, it generally makes for a good general interest local news story. But scientists are noticing pancake ice is becoming more prevalent in the Arctic, and some think it could be linked to climate change — and that this particular formation of ice could be accelerating the global temperature rise.
Warmer global temperatures have decreased the occurrence of the large ice sheets that used to be so common in the Arctic. This has exposed more of the water to high winds, which creates more agitation and waves that lead to pancake ice. When pancake ice forms instead of a huge, continuous ice sheet, the sun can get to the water between the coins of ice rather than being reflected by a great, white shield. This warms the ocean more quickly, creating more pancake ice and fewer large ice formations.