English: On November 14, 2017, John Sonntag (mission scientist for Operation IceBridge) took this photograph of ice in the Weddell Sea. The geometric shapes are due to a phenomenon known as “finger rafting,” which occurs when two floes of thin ice collide. As a result of a collision, blocks of ice slide above and below each other in a pattern that resembles a zipper or interlocking fingers. Brine expelled from the ice forms a solution that acts as a lubricant.

For finger rafting to occur, it’s critical that the ice be thin—calculations suggest no more than 20 centimeters (8 inches). Any thicker and the ice loses its flexibility. Without flexibility, thicker ice floes that collide can result in a big pile up known as “ridging.”

“Normally you see finger rafting in bits and pieces, a few blocks here and there,” said Nathan Kurtz, IceBridge project scientist. “But this is so extensive. I’ve never seen so much rafting occurring across such a wide area.” That is not necessarily significant; it is simply a good example of the phenomenon.

The photograph above was shot on November 14, 2017, from the window of a NASA P-3 research airplane during a flight for Operation IceBridge.