Polar Star

NASA

Cracking Antarctic Sea Ice

‘Tis the season for long and ruler-straight cracks in McMurdo Sound’s sea ice. Though natural breaks in sea ice are called leads, the better term for the human-made fracture seen in these satellite images is a ship channel. In the austral summer, usually in January, an icebreaker rams a path through the fast ice—a type of sea ice that is anchored to the shore—that often covers…