昨年は暖冬で全面凍結しなかった屈斜路湖。今年は冬らしい寒い日が続き2年ぶりに氷で覆われました。この辺りでは「オホーツクの流氷が接岸すると寒気がやってきて湖が凍る」と言われていますが、確かに流氷が接岸した2月初旬に全面結氷したようです。
例年ですと厚く凍った氷が膨張し圧力に耐えられなくなり割れて盛り上がる現象が見られるはず。時々氷の上を歩いて探しに行きますが、先日の雨と気温の上昇で今年はまだ大きなものはできていないようです。
そういった氷の風景も美しいのですが今興味があるのが凍った湖の音。氷が押し合い割れたり割けたりする音のほかに、湖の底から聞こえるような不思議な音があります。ミシミシでもバキバキでもないピヨーンピヨーンといった宇宙的な音。結構大きな音が鳴る時もあり、極寒のなか湖畔に座って聞いています。なぜあんな音がするのか不思議です。きっと比較的離れた場所で発生した氷の割れる音が固体伝搬音として氷の中を伝わっていく間に周波数分布が変化したものではないかと思ってます。
厚く凍った湖面は十分に歩けますが、湖岸では所々温泉が湧いており氷が溶けて薄くなっているところがあるので慣れない人は注意してくださいね。
Lake Kussharo did not freeze last year due to the warm winter. This year, cold winter days continued and ice covered the lake for the first time in two years. It is said that "When the drift ice of Okhotsk reaches the shore, cold air comes and the lake freezes." around here, it is true that the entire area of the lake froze in early February when the drift ice reached the shore.
Every year, you will see a phenomenon where thick frozen ice expands and becomes unable to withstand the pressure, then cracks and rises. I sometimes walk on the ice to look for it, but it seems that the phenomenon has not been made this year because of the rain and the temperature rise the other day.
The view of ice on the lake is beautiful, but what I'm interested in now is the sound of frozen lakes. Besides the sound of ice crashing and breaking, there is a strange sound that you can hear from the bottom of the lake. Like a cosmic sound that is neither creaky nor buzzing. There are times when it makes quite a big sound, so I sit by the lakeside in the extreme cold and listen to it. I wonder why it makes that sound. I think that the frequency distribution of the sound changed while the sound of ice breaking generated at a relatively distant place was transmitted through the ice as solid propagation sound.
You can walk on the thick frozen surface of the lake, but please be careful if you are not used to it because there are some hot springs and the ice has melted and become thin on the shore of the lake.