A deep temperate lake, Lake Kuttara, Hokkaido, Japan (148 m deep at maximum) was\ncompletely ice-covered every winter in the 20th century. However, ice-free conditions of the lake\nover winter occurred three times in the 21st century, which is probably due to global warming.\nIn order to understand how thermal regime of the lake responds to climate change, a change in\nlake mean water temperature from the heat storage change was calculated by integrating observed\nwater temperature over water depths and by numerical calculation of heat budget components based\non hydrometeorological data. As a result, a temporal variation of lake mean water temperature\nfrom the heat budget calculation was very reasonable to that from the observed water temperature\n(determination coefficient R2 = 0.969). The lowest lake mean temperature for non-freeze was then\nevaluated at âË?â??1.87 ââ??¦C, referring to the zero level at 6.80 ââ??¦C. The 1978ââ?¬â??2017 data at a meteorological\nstation near Kuttara indicated that there are significant (less than 5% level) long-term trends for air\ntemperature (+0.024 ââ??¦C/year) and wind speed (âË?â??0.010 m/s/year). In order to evaluate the effects of\nclimate change on freeze-up patterns, a sensitivity analysis was carried out for the calculated lake\nmean water temperature. It is noted that, after two decades, the lake could be ice-free once per every\ntwo years.
Loading....