Climate sensitivity and parameter coherency in annually resolved δ13C and δ18O from Pinus uncinata tree-ring data in the Spanish Pyrenees

We explore the 20th century climate sensitivity of annually resolved carbon and oxygen isotope ratios in five Pinus uncinata individuals from the upper treeline in similar to 2400 m asl of the Spanish Pyrenees. Time series of delta C-13 and delta O-18 are calibrated against temperature, precipitation, and drought indices over the period 1901-2009. Negative correlations of delta C-13 with summer precipitation and drought indices, as well as positive correlations with summer temperatures, confirm previous evidence from similar habitats in the Pyrenees. In contrast to this summer climate signal in the carbon isotopes, the delta O-18 record reveals mainly negative correlations with spring precipitation and drought. We explore the coherence between delta C-13 and delta O-18 time series derived from individual trees and assess the influence of widely applied delta C-13 correction procedures on the climate signal strength. Spatial correlation patterns and decomposition of the time series into high-and low-frequency components are used to develop a calibration setup for carbon and oxygen isotope ratios, which will improve long-term climate reconstructions in a region, where classical tree-ring width and density data are limited. (C) 2014 Elsevier B.V. All rights reserved.