Ancient Japanese and Finnish ice records yield insights into climate change

National Geographic : Ice observations made in Japan and Finland over the past several centuries are helping modern climate scientists better track climate change. Since at least 1443, Shinto priests have been recording the formation of a distinctive ice ridge on Lake Suwa in the Kino Mountains of central Japan. In Finland, a merchant named Olof Ahlbom started recording the spring ice breakup on the Torne River in 1693, and those observations have been continued by others ever since. By studying the seasonal patterns of ice formation in two such geographically distinct areas over hundreds of years, John Magnuson of the University of Wisconsin–Madison and colleagues have been able to gather important climate data, particularly from before the start of the Industrial Revolution. They note that Suwa has been freezing over progressively later each year and that Torne has been thawing progressively earlier. Also, both areas have been experiencing an increase in the number of extreme warm years. If atmospheric carbon dioxide concentrations and air temperatures continue to rise, the researchers say, Lake Suwa and many other lakes and rivers around the world will fail to freeze over at all.