The bluest ice


The undersides of icebergs can contain old, dense, deep blue ice.


An iceberg floating in Antarctica’s McMurdo Sound.
An iceberg floating in Antarctica’s McMurdo Sound.
NASA / Chris Larsen

Acquired on November 29 2017 during a flight to Victoria Land, this image shows an iceberg floating in Antarctica’s 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—quite different from the more common and more stable tabular berg in the top right of the image—suggests that it likely rotated sometime after calving.

The photo was taken as part of Operation IceBridge — an airborne mission to map polar ice which has for several years conducted ice-monitoring flights, giving researchers greater access to the interior of the icy continent and turning up ample science data, as well as spectacular images.

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