The Earth's climate is a profoundly complex system, ever in flux.

The ice caps have periodically melted and reformed numerous times over geologic history. They shall melt again!

At the very least, we know the ice caps are going to be toast in a few hundred million years, once the sun ages and swells and heats up enough.

But we're more interested in short term consequences. Per this analysis from Rolling Stone:

We've known for some time that our warming climate will eventually mean the transformation of the ice-locked Arctic into an open expanse of blue water. The question has long been not if, but when.

Researchers publishing in Physical Sciences in 2013 ("Reducing spread in climate model projections of a September ice-free Arctic") projected an "ice free" arctic by the 2050s.

In 2016, the Guardian reported this story. Key idea:

Scientist Peter Wadhams believes the summer ice cover at the north pole is about to disappear, triggering even more rapid global warming.

In March 2018, Vox reported:

In 1985, 45 percent of the ice in the Arctic was more than a year old. In 2017, that figure was down to 21 percent.

At some point, we will see a year in which the Arctic will be essentially ice-free. What year will that be?

Resolution occurs when the arctic ice coverage (at a threshold 15% ice density) falls below 1 million $km^2$ , as reported in numbers from the NSIDC. Should NSIDC numbers be unavailable, or arguably substantially changed in methodology from those circa 2018, an alternative source provided by a national government other than the US, and consistent within errors with NSIDC's number as of 2018, may be used as a substitute.