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Temperature reconstructions for the last 140 years at Hohenpeißenberg using stable isotopes of wood lignin methoxyl groups

Subject Area Mineralogy, Petrology and Geochemistry
Term from 2009 to 2018
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 148522579
 
Final Report Year 2018

Final Report Abstract

The goal of this project was to reconstruct mean annual temperatures at Hohenpeißenberg (Germany) for the last 140 years using a high resolution stable hydrogen isotope chronology of lignin methoxyl groups (δ2HLM) in European beech trees. For this, we collected nine increment cores of four Fagus sylvatica trees collected at Hohenpeißenberg (Germany). All cores covered the most recently collected century (1906-2015) and were subsequently used to measure the δ²HLM values at annual resolution. The measured δ²HLM values showed highly significant inter-series correlations (r ranging between 0.37 and 0.73, p < 0.001) among the nine cores over the 1906-2015 period giving confidence to produce a mean δ²HLM chronology. When compared to stable hydrogen isotope values of precipitation (δ²Hprecip) the mean δ²HLM chronology showed the highest correlation with the annually averaged value (r = 0.66, p < 0.001) indicating that the tree source water at the Hohenpeißenberg study site reflects predominantly an annual integral. When compared to instrumental climate data the mean δ²HLM chronology showed further significant correlations with the local mean annual temperature (r = 0.57, p < 0.001) whereby a stronger influence is suggested for large-scale and remote temperature anomalies. Spatial correlations between the mean δ²HLM chronology and land as well as sea surface air temperature trends showed highest correlations for a combined area covering broadly continental and marine Western Europe (r ranging between 0.5 and > 0.6, p < 0.001). We established a linear regression model between the mean δ²HLM chronology and the averaged Western European surface air temperature (WESAT) anomaly yielding a highly significant correlation with r = 0.67 (p < 0.001). When the estimated linear regression model is used to reconstruct WESAT anomalies over the 1916-2015 period the results show a mean absolute deviation of as low as 0.16 °C with respect to instrumental records. Thus, our project provided a valuable calibration study between δ²HLM values in tree-ring series and climate parameters. Based on our results we suggest that the δ²HLM proxy may play an important role in highly resolved climate reconstructions contemplating commonly used dendrochronological climate parameters (TRW and MXD). Furthermore, the δ²HLM proxy showed not only an applicability for recent tree-ring chronologies covering the Late Holocene but also for deep-time Cenozoic mummified wood specimen as could recently be shown in Anhäuser et al. (2018).

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