From the time Europeans discovered the North American continent to the mid-twentieth century, sailors searched for a northwest passage that would connect the Atlantic Ocean (and Europe) to the Pacific Ocean (and Asia). No such passage exists through the continent, but during the summer, a northwest route through the Arctic opens up.
A spectacular view of sea ice was captured during an Operation IceBridge flight in 2014; the mission surveyed ice at both poles again in 2015, this time simultaneously.