An ice-free summer is "a matter of when, not if," Walt Meier, senior research scientist at the U.S. National Snow and Ice Data Center, tells The Guardian. He says that 2007 to 2020 resulted in the 14 lowest ice years in recorded history. For perspective, ice sheets were twice as thick in the 1980s than they are now, he says. Satellite records show a 13 percent decrease in sea ice per decade since the 1980s.

Shrinking ice sheets leave less snow-covered surface area to reflect sunlight away from the Earth's surface. Smaller ice sheets mean larger swaths of open ocean, which absorb heat, warming the temperature of the sea. This feedback loop could lead to an ice-free summer by 2035, reports Gizmodo.

"We are currently in uncharted waters with record low Arctic sea ice this late in the year," Geoff York, senior director of conservation at Polar Bears International, tells Gizmodo in an email. "This is yet another red flag from our rapidly warming planet—trying to warn us of changes yet to come."