The Arctic sea ice cap is an expanse of frozen seawater floating on top of the Arctic Ocean and neighboring seas.

Every year, it expands and thickens during the fall and winter and grows smaller and thinner during the spring and summer.

But in the past decades, increasing temperatures have caused marked decreases in the Arctic sea ice extents in all seasons, with particularly rapid reductions in the minimum end-of-summer ice extent.

The shrinking of the Arctic sea ice cover can ultimately affect local ecosystems, global weather patterns, and the circulation of the oceans.

According to NASA, the Arctic continues seeing a trend of shrinking maximum extents. The 2018 maximum extent reached 5.59 million square miles, only about 23,000 square miles larger than the lowest maximum on record, in 2017.