What is the reason why natural ice springs in Hubei freeze in summer?

As long as any river, lake and sea is located to the north of a certain latitude in the cold temperate zone, it will freeze in winter and turn into clear water in summer, which is the law of nature and common sense of people. However, there is a strange phenomenon in the world that does the opposite-the spring water freezes in the sky, and the hotter it is outside, the thicker the spring water freezes. According to Shantou Special Zone Evening News, there is a natural ice spring at an altitude of 1,7 meters in Baiyi Village Scenic Resort under Yuping Peak in Wufeng County, Hubei Province. The ice spring is completely exposed on the ground. Every summer, the water in the ice cave begins to freeze. The hotter the weather, the thicker the ice layer, and the lowest temperature of the "ice cave" can reach -2℃. However, this "ice cave" is only about 2 meters higher than the mouth of the cave, but it is still green.

The water in the ice cave is bright all the year round, and the raw pickles used by villagers nearby are neither smelly nor putrid. The average life expectancy of villagers in Baiping and Huping villages who drink this spring and its adjacent water sources is 71 years, including 69 people aged 6-8, 2 people over 9 and 2 people over 1. There are 21 people who are still alive over 9 years old.