Diverging site-specific trends in the water temperature of a large boreal lake in winter and summer due to mixed effects of local features and climate change

作者：Voutilainen Ari^*; Huttula Timo; Juntunen Janne; Rahkola Sorsa Minna; Rasmus Kai; Viljanen Markku

来源：Boreal Environment Research, 2014, 19(2): 104-114.

We present diverging long-term trends in the water temperature of a large boreal lake, Lake Pyhaselka (263 km(2)), located in eastern Finland. The dataset was constructed from a half century of monitoring (1962-2010). The direction of the temperature trend depended on the water layer and the season, in that the yearly average temperature in the top layer (1-10 m) as recorded in summer (June-August) increased by 2.5 degrees C over the monitoring period, whereas that recorded when the lake was covered by ice (January-April) decreased from 0.6 to 0.2 degrees C. The water temperature in the bottommost layers showed no trends. We suggest that the water temperature under the ice is decreasing in this case as a consequence of mixed effects of lake-specific physical features and climate change, which cause variations in the heat content of the inflowing water of the Pielisjoki. The epilimnetic water temperature in summer appeared in turn to follow general trends in air temperatures. Our results stress the need for taking local and site-specific phenomena into account when drawing conclusions about the effects of climate change on lakes.

• 出版日期2014-4-25