Glassy blue iceberg goes belly up

Roughly 90 percent of an iceberg’s volume hides beneath the waves. But every so often an iceberg’s underbelly makes an appearance above the waterline.

Filmmaker Alex Cornell photographed this recently overturned iceberg jutting about 9 meters skyward in Cierva Cove, Antarctica, in December. It’s a rare sight, says oceanographer Louise Biddle of the University of East Anglia in Norwich, England. Over time accumulating snow and debris whiten exposed ice, so Biddle suspects this iceberg had flipped at most a few days earlier. An iceberg can flip shortly after snapping off its parent glacier, she says, or when uneven melting causes the berg to shift its balance like a sailboat with a broken mast.

The newly exposed ice probably originated deep within the glacier, where high pressures squeeze out tiny air bubbles that scatter white light. Bubble-free ice absorbs red and yellow light while reflecting blue light, giving the upturned iceberg its spectacular color.

Despite their beauty, icebergs can be dangerous when they roll over. Biddle says research vessels and tourist ships steer clear of large bergs, fearing huge splashes and capsize-inducing waves in the event of a flip.