A tree-ring field reconstruction of Fennoscandian summer hydroclimate variability for the last millennium
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Hydroclimatological extremes, such asdroughts and floods, are expected to increase in frequencyand intensity with global climate change. An improvedknowledge of its natural variability and the underlyingphysical mechanisms for changes in the hydrological cyclewill help understand the response of extreme hydroclimaticevents to climate warming. This study presents the firstgridded hydroclimatic reconstruction (0.5 0.5 gridresolution), as expressed by the warm season StandardizedPrecipitation Evapotranspiration Index (SPEI), for most ofFennoscandia. A point-by-point regression approach isused to develop the reconstruction from a network ofmoisture sensitive tree-ring chronologies spanning over thepast millennium. The reconstruction gives a uniqueopportunity to examine the frequency, severity, persistence,and spatial characteristics of Fennoscandian hydroclimaticvariability in the context of the last 1,000 years.The full SPEI reconstruction highlights the seventeenthcentury as a period of frequent severe and widespreadhydroclimatic anomalies. Although some severe extremeshave occurred locally throughout the domain over the fifteenthand sixteenth centuries, the period is surprisinglyfree from any spatially extensive anomalies. The twentiethcentury is not anomalous in terms of the number of severeand spatially extensive hydro climatic extremes in thecontext of the last millennium. Principle component analysisreveals that there are two dominant modes of spatialmoisture variability across Fennoscandia. The same patternsare evident in the observational record and in thereconstructed dataset over the instrumental era and twopaleoperiods. The 500 mb pressure patterns associatedwith the two modes suggests the importance of the summerNorth Atlantic Oscillation.
|Research areas and keywords||
Subject classification (UKÄ) – MANDATORY
|Publication status||Published - 2015|