English: This photograph, acquired on November 29 during a flight to Victoria Land, shows an iceberg floating in McMurdo Sound. The part of the iceberg below water appears bluest primarily due to blue light from the water in the Sound.

The undersides of some icebergs can be eroded away, exposing older, denser, and incredibly blue ice. Erosion can change an iceberg’s shape and cause it to flip, bringing the sculpted blue ice above the water’s surface. The unique step-like shape of this berg—compared to the tabular and more stable berg in the top-right of the image—suggests that it likely rotated sometime after calving.

This iceberg shows just a hint of blue color on its surface where snow has been removed. Snow and ice that appears white will contain large numbers of air pockets, bubbles, and other reflective particles that tend to reflect all wavelengths of visible light equally.

Photos courtesy of Chris Larsen, NASA's Operation IceBridge mission. Story by Kathryn Hansen.