Climatologists from Colorado University (CU) Boulder and the University of Gothenburg have used computer models to investigate when the Arctic might experience its first ice-free day. In this context, 'ice-free' means a sea ice area of 1 million square kilometers (386,000 square miles) or less.

“The first ice-free day in the Arctic won’t change things dramatically,” said Jahn. “But it will show that we’ve fundamentally altered one of the defining characteristics of the natural environment in the Arctic Ocean, which is that it is covered by sea ice and snow year-round, through greenhouse gas emissions.”