Every year, after the mouth of the Tokachi River freezes over and breaks off into the sea, the frigid ocean returns polished chunks of ice to the shore that look like gigantic diamonds.
Known as Tokachi river ice, jewel ice and jewellery ice, this beautiful phenomenon only happens on Hokkaido, Japan’s northernmost main island.
“I had never heard of this type of ice and have never seen any sea ice like it,” Peter Wadhams, an ocean physicist at the University of Cambridge, told The New York Times. According to Wadhams, the ice is transparent because there is no salt in it. While you can only find this kind of river ice in this spot in Japan, it’s similar to glacier ice you’d see in Alaska.
After a photographer shared his shots of what he dubbed “jewelry ice” back in 2015, locals have flocked to the Tokachi River every January and February to capture this rare spectacle and share their photos on social media.
Here are some of their best Tokachi river ice photos: