Relationships between ice breakup dates of lakes and local air temperature on the Eurasian continent

Ice breakup dates on lakes are related to the local air temperature, and are useful for understanding the local climate. However, little study has been done on lakes on the Eurasian continent. Therefore, an ice breakup date estimation method, using water temperature trend and threshold surface temperature and aided by satellite remote sensing, was developed in our previous study in order to obtain the ice breakup dates for these lakes. The spatial distribution of ice breakup dates was also determined from the ice breakup dates on 18 Eurasian lakes from 2001 to 2003. The current paper reports the time series of the ice breakup dates, and establishes the relationships between ice breakup date and local air temperature. First, we estimated the ice breakup dates for Lake Khanka, which lies in the east of the Eurasian continent, over a period between 1984 and 2003, using advanced very high resolution radiometer (AVHRR) data. The results show that the ice breakup dates vary across a span of 10 to 20 days over a cycle of 5 to 10 years. According to the annual analysis, the ice breakup period does not become any earlier during the 20 years of the estimates. The observed data for Lake Baikal show a similar picture, although low correlation coefficients suggest that there is no strong relationship between the ice breakup dates for these lakes. Second, for each year, the ice breakup dates on Lake Khanka were plotted against the air temperature at Vladivostok, located about 160 km south of Lake Khanka. This analysis helps us to understand that a day change in ice breakup date represents a 0.3 degrees C change in the mean air temperature in the month prior to the ice breakup date. A similar relationship was also derived between the ice breakup dates over 3 years on 17 Eurasian lakes and the air temperature derived from an observatory near to each lake.