How to

11 May 2017

Rare ‘Dragon-Skin’ Ice Sighted in Antarctica

We’ve spoken in the past about some of the world’s weirdest and most wonderful ice formations, ranging from elegant ribbons to fields of frost blossoms. However, perhaps none are as rare and enchanting as the phenomenon known as dragon-skin ice.

Img: Guy Williams/PIPER Collaboration
The rarely-seen form of sea ice, named for its unusual aesthetic, is formed when sea water is frozen in the air as a result of hurricane-strength katabatic winds lifting the existing ice from the surface and creating a region known as a polynya, defined as a stretch of open water surrounded by sea ice. This exposes more water to the freezing temperatures above and in turn results in the formation of more ice.

The phenomenon hasn’t been seen in Antarctica since 2007; until now, that is.

Dragon-skin ice was recently observed in Antarctica once more by Dr Guy Williams during a trip on board the Nathaniel B Palmer icebreaker, as part of the PIPERS (Polynyas, Ice Production and its Seasonal Evolution in the Ross Sea) expedition. The PIPERS expedition is an effort by 27 scientists from 8 countries to study the winter behaviour of coastal polynyas.

“Dragon-skin ice is very rare, bizarre, evidence of a darker chaos in the cryospheric realm, not seen in Antarctica since 2007,” Dr Williams said.

“Imagine your standard ice cube tray, filled once.  After a week, you get one tray of ice cubes. But if you empty and re-fill the tray each night, you get so much more.

“That is what the katabatic winds are doing in the polynya, removing the ice, exposing the water and making more ice form.”

Img: Guy Williams/PIPER Collaboration
Dragon-skin ice makes for more than just a pretty landscape however; Dr Williams asserts that such enhanced ice growth has a vitally important effect on local and global oceanography, as well as the flow of global ocean currents. This is due to the way in which sea water freezes, forcing out salt and creating a dense, heavily-salinated abyssal layer beneath the ice which kick-starts the southern limb of the global overturning circulation, the natural mechanism responsible for moving water currents throughout all the Earth’s oceans.

“We are currently at ground zero of a hurricane-strength (65+ knots) katabatic wind event in the Terra Nova Bay polynya, in the Ross Sea, West Antarctica,” said Dr Williams. “It’s quite incredible to experience such an epic demonstration of polar ocean-atmospheric interaction.

“After a couple of weeks of work in the advancing sea ice pack to the north, we have found ourselves once again strapping everything down as the winds and waves buffet our progress.

“We will spend the next two weeks taking advantage of quiet periods when the katabatic winds drop off to observe the increase in salinity of the shelf waters below polynyas as brine-rejected during sea-ice formation rains down to depths below 1000m in the Drygalski Trough.”

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.