Changes in ice-season characteristics of a European Arctic lake from 1964 to 2008
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The long-term ice record (from 1964 to 2008) of an Arctic lake in northern Europe (Lake Kilpisjärvi) reveals the response of lake ice to climate change at local and regional scales. Average freeze-up and ice breakup occurred on 9 November and 19 June, respectively. The freeze-up has been significantly delayed at a rate of 2.3 d per decade from 1964 onward (P < 0.05). No significant change has taken place in ice breakup. Annual average ice thickness has become smaller since the mid-1980s (P < 0.05). Air temperature during the early ice season significantly affected the ice thickness. The freeze-up date exhibits the highest correlation with the 2-month average daily minimum air temperature centered at the end of October, while the ice breakup date exhibits the highest correlation with the 2-month average daily maximal air temperature centered in mid May. A 1°C increase in the surface air temperature corresponds to a freeze-up later by 3.4 days and an ice breakup earlier by 3.6 days. Snow cover is a critical factor in lake-ice climatology. For cumulative November to March precipitation of less than 0.13 m, the insulating effect of the snow dominated, while higher rates of precipitation favored thicker ice due to the formation of snow ice. Variations in ice records of Lake Kilpisjärvi can serve as an indicator of climate variations across the northern Europe. The North Atlantic Oscillation (NAO) does not significantly affect the ice season there, although both the local air temperatures and winter precipitation contain a strong NAO signal.
KeywordsSnow Depth North Atlantic Oscillation Breakup Date North Atlantic Oscillation Signal
This work was supported by the Academy of Finland (grant nos. 116905 and 140939) and the National Natural Science Foundation of China (grant nos. 40930848 and 41106160). RL was supported by a CIMO scholarship from the Ministry of Education in Finland. PH was supported by the Australian Government’s Cooperative Research Centre Program. Ice records of Lake Kilpisjärvi were provided by the Finnish Environment Center. Atmospheric data from the Kilpisjärvi Biological Station and Enontekiö Kilpisjärvi Kyläkeskus were provided by the Finnish Meteorological Institute. Two anonymous reviewers are thanked for their comments, which considerably improved this work. Dr. S. Lake is thanked for grammatical check on our manuscript.
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