The frozen regions of our planet might all seem alike, but there are actually many different types of ice. Often times, extreme conditions can create structures of spectacular beauty.
Such is dragon-skin ice, which forms after sea-water is frozen in mid-air thanks to hurricane-strength winds. The rare phenomenon was documented by Dr Guy Williams, who’s traveling across the Ross Sea onboard the Nathaniel B Palmer icebreaker as part of the PIPERS (Polynyas, Ice Production and its Seasonal Evolution in the Ross Sea) expedition.
The descending winds, known as katabatic, from the interior of the southernmost continent move at over 300 kilometers (190 miles) per hour and are strong enough to lift the ice from the surface of the sea water, creating a region known as a polynya – an open-water stretch surrounded by ice.
“Imagine your standard ice cube tray, filled once. After a week, you get one tray of ice cubes. But if you empty and refill the tray each night, you get so much more,” Dr Williams explained in a statement. “That is what the katabatic winds are doing in the polynya, removing the ice, exposing the water and making more ice form.”
The dragon-skin ice. Guy Williams/PIPER collaboration
But this is not just unusual ice. Researchers are there to understand how the growth of sea ice plays a role in local and global currents, and crucial to this are the strong winds. The polynya they create allow more water to be exposed to the freezing temperatures.
The cold, salty, and dense water beneath the ice sinks to form an abyssal layer, which is believed to kickstart the overturning circulation – the series of both deep and surface currents that move water in all the oceans.
"We are currently at ground zero of a hurricane-strength (65+ knots, 70 mph) katabatic wind event in the Terra Nova Bay polynya in the Ross Sea, West Antarctica. It’s quite incredible to experience such an epic demonstration of polar ocean-atmospheric interaction," continued Dr. Williams. "Dragon-skin ice is very rare, bizarre, evidence of a darker chaos in the cryospheric realm, not seen in Antarctica since 2007."
The katabatic winds are expected to drop off in the next few weeks. When the atmospheric situation is calmer, the scientists will measure the salinity of the ocean and the movement of briny water falling below 1,000 meters (0.6 miles).
The international expedition has 27 scientists from eight countries and 14 institutions. It’s traveling around Antarctica until June with the goal to understand the role of polynyas during the polar winter.
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