By TATSURO SAKATA/ Staff Writer
March 12, 2023 at 07:10 JST
“Juhyo” ice monsters seen around the 1,736-meter-high Mount Jizosan in the Zao mountain range in Yamagata in February (Asahi Shimbun file photo)
“Juhyo” ice monsters once inhabited a wide area of the Japanese archipelago but are steadily disappearing due to climate change.
The phenomenon, rarely observed outside the country, is a winter symbol of the Zao mountain range straddling the borders of Yamagata and Miyagi prefectures.
But Fumitaka Yanagisawa, a professor emeritus at Yamagata University’s Research Institute for Ice Monsters and Volcanoes of Zao, warns that ice monsters will all but vanish from Japan by the end of the century unless climate change slows.
Juhyo were previously found in a wide area stretching from Hokkaido in the north to Ishikawa Prefecture in the south, but their geographical distribution has been shrinking, both from the northern and southern ends, according to Yanagisawa.
The winter spectacles appear on mountains in the northeastern Tohoku region when evergreen conifer trees are covered with snow and ice, creating shapes resembling giant beasts.
“Due to global warming, juhyo now form in areas with higher altitudes than in the past,” Yanagisawa said. “But there are no longer any mountains or conifer trees in Hokkaido at altitudes that meet the required weather conditions.”
According to Yanagisawa, juhyo require multiple specific weather conditions to form: low temperatures between minus 10 and 15 degrees, snow accumulation of two to three meters and strong northwest or west winds with a speed of 36 to 54 kph, among others.
The altitudes where juhyo can form are lower the farther north the location because conifer trees will get completely buried if it snows too much.
The average temperature in Hokkaido has risen by about 1.6 degrees over the 100 years through 2020, according to the Sapporo District Meteorological Observatory.
“Juhyo can be seen in the Tohoku region where there are still mountains and conifer trees that meet the conditions,” Yanagisawa said. “But if global warming continues at its current pace, it will be difficult to see juhyo in the country by the end of the century.”
The areas in the Tohoku region where juhyo can be found include the Hakkoda mountain range in Aomori Prefecture; Mount Hachimantai in Iwate Prefecture; Mount Moriyoshizan in Akita Prefecture and Mount Azumayama, which straddles the borders of Fukushima and Yamagata prefectures.
Yanagisawa has been researching historical photos and documents to identify areas where juhyo were previously spotted.
He has confirmed that people had observed the phenomenon in broad areas beyond the Tohoku region until around 1960. Juhyo had been found from Hokkaido to Ishikawa Prefecture, about 50 to 60 kilometers inland from the Sea of Japan.
The farthest north was Mount Piyashiriyama, part of the Kitami mountain range in Hokkaido.
Kyuya Fukada (1903-1971), a writer known for his book “One Hundred Mountains of Japan” who was knowledgeable about the phenomenon, documented what he saw on the mountain in December 1941.
“I was once surprised to see juhyo as far as I could see in a big field on the east side of the top of the mountain,” he wrote.
Photos also show juhyo on Mount Muineyama and Mount Nagaoyama in the Jozankei hot spring resort in Sapporo.
Yanagisawa found a photo showing juhyo taken on Mount Kaminodake, aka Kitanomatadake, in Toyama Prefecture in 1923.
It is one of the oldest known photos of juhyo, second only to the one shot on the Zao mountain range by a member of Keio University’s mountaineering club two years prior in 1921.
Yanagisawa confirmed with photos that juhyo had formed in the Shiga and Sugadaira highlands in Nagano Prefecture. He also found a comment by a botanist in 1936 that there were juhyo on Mount Makihatayama in Niigata Prefecture.
The farthest south was Mount Hakusan in Ishikawa Prefecture, which he confirmed with a photo taken in January 2018.
According to the Japan Meteorological Agency, the average temperature in Japan has risen by 1.3 degrees in the past century.
The average temperature is expected to rise by 4.5 degrees by the end of the 21st century from the end of the 20th century unless effective countermeasures are taken.
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