Every winter, beaches in northern Japan experience a unique phenomenon when chunks of crystal clear ice wash up on their shores. Known as "jewel" or "jewelry ice" and "Tokachi River ice," the ice forms when salt-free water from the Tokachi River on Hokkaido, the second-largest and northernmost of Japan's main islands, meets sub-zero temperatures, salty seawater and ocean tides.
The mouth of the Tokachi River is the only place on the planet known to produce ice like this, ocean physicist Peter Wadhams recently told the New York Times, though he pointed out that other clear ice exists in glaciers and fjords in Chile and Alaska. One factor in ice's opacity is the amount of air bubbles trapped in the frozen water, and this jewel-like ice — which can glow purple or orange when sunlight hits it at different times of day — has very few. Such a crystal-clear ice is product of water free of other contaminants and a slow freezing process.
The ice forms in the Sea of Okhotsk, a body of water between Hokkaido and the Kamchatcka Peninsula in Russia. Japan's northern coastal city of Monbetsu even has an entire museum dedicated to the phenomenon, complete with a room whose temperature is a steady minus 4 degrees Fahrenheit (minus 20 degrees Celsius), where visitors can touch real sea ice.
Winter doesn't always have to be a time to stay indoors, and the region celebrates its frosty identity. Local cities throw an annual ice festival featuring giant ice sculptures, and tourists can even take cruises in icebreaker ships outfitted with massive drills to check out the drift ice — and any cute seals that might happen by.
Photogenic jewelry ice has quickly become a social-media star, popping up all over Instagram and Twitter:
Take a peek at this rare natural phenomenon in action in this Japanese-language video from Kyodo News: