Annually resolved δ²H tree-ring chronology of the lignin methoxyl groups from Germany reflects averaged Western European surface air temperature changes

Abstract. Stable hydrogen isotopes ratios of lignin methoxyl groups (expressed as δ²H_LM) of wood have been shown to reflect the climate-sensitive δ²H values of precipitation (expressed as δ²H_precip) modulated by a large uniform negative isotope fractionation. However, a detailed calibration study among temporal variabilities of δ²H_LM in tree-ring series, site-specific δ²H_precip and climate parameters has not been performed yet. Here, we present annually resolved δ²H_LM values from nine tree-ring series (derived from four Fagus sylvatica L. trees) collected near stations of the Global Isotope Network of Isotopes in Precipitation (GNIP) and the Deutsche Wetterdienst (DWD) meteorological observatory at Hohenpeißenberg (southern Germany; ~ 48° N, 11° E). The measured nine δ²H_LM tree-ring series (common period of overlap 1916-2015) show a strong coherency as indicated by highly significant (p < 0.001) inter-series correlations (mean value Rbar = 0.52) and no indication of any known (stable isotope-specific) juvenile trend affecting the first decades of growth. When compared to local instrumental data, the combined δ²H_LM chronology shows highest correlations with annually averaged data of δ²H_precip as well as temperature particularly when using the year defined from previous September to current August (r = 0.73 and 0.56, respectively, p < 0.001). However, the Hohenpeißenberg δ²H_LM chronology shows enhanced correlations with land and sea surface air temperature for multiple (broadly combined) areas across Western Europe (r > 0.6, p < 0.1). We subsequently established a linear regression model between averaged Western European surface air temperatures (range: 30° W–20° E, 35–60° N) and the δ²H_LM chronology (r = 0.71, p < 0.001). When comparing instrumental and reconstructed large-scale temperature anomalies from the year 1916 to 2015, an average absolute deviation in annual reconstructions of as low as 0.3 °C was found (n = 100). Therefore, δ²H_LM values of mid-latitudinal tree-ring archives are considered suitable for large-scale mean annual temperature reconstructions and are therefore able to improve the paleoclimatic potential of Late Holocene tree-ring archives.