Blue Intensity in Pinus sylvestris: application, validation and climatic sensitivity of a new palaeoclimate proxy for tree ring research

Minimum blue intensity measurements of resin-extracted Pinus sylvestris samples, are shown to provide a robust and reliable surrogate for maximum latewood density. Blue intensity data from fifteen trees, are reported relative to a standard blue-scale in a manner similar to grey-scale calibration in X-ray densitometry. The resulting time series are highly correlated with X-ray densitometry data generated from the same samples and preserve a high level of signal strength. The sensitivity to summer climate variables is similar to that identified in the relative density record, demonstrating that minimum blue intensity can also be used for the study of climate change.