Many scientists think the Arctic Ocean will be ice-free during the summer months within the next few decades, likely before 2050. One sign of this is that one-year-old ice, which melts easily, made up 79 percent of the Arctic sea ice in 2017, the report found. Older, thicker, multiyear ice comprised just 21 percent of the 2017 sea ice cover, compared to more than twice that in 1985.
Osborne cited data from 45 different indicators of sea ice extent dating back 1,500 years, such as tree rings and other so-called “proxy data,” showing that the recent plunge in sea ice extent is “unprecedented in the last 1500 years and likely longer.”
The Arctic is warming at twice the rate of the rest of the globe, largely because of a process known as Arctic amplification. Through this process, warming air and sea temperatures melt sea ice, which exposes darker ocean waters to incoming sunlight. Since the ocean waters are less reflective than the ice, they absorb more heat, thereby warming the sea and air, and then, well, melting more ice.