Spring temperature variability in northern Fennoscandia AD 1693-2011

A reconstruction of spring (April-May) temperature for northern Fennoscandia developed from the Tornionjoki (Tornio river) long cryophenological record of ice break-up dates, back to AD 1693, is presented. The record is strongly climatically sensitive and explains 67% of the variance in the instrumental data over the last 150 years. The record exhibits a stepped decrease in the duration of the river's ice cover by 14 days, equivalent to an increase in April-May mean temperature of approximately 2.5 degrees C over the last three centuries. The relationship between the date of ice break-up, and accumulated daily mean temperatures (>0 degrees C) is investigated. Uncertainty in the observation of ice break-up is also considered in addition to the potential of this time series for regional climate model validation. Copyright (C) 2011 John Wiley & Sons, Ltd.