France 670 Year Tree-Ring d18O Data and SPEI Drought Reconstruction Labuhn, I.; Daux, V.; Girardclos, O.; Stievenard, M.; Pierre, M.; Masson-Delmotte, V. Labuhn, I. Daux, V. Girardclos, O. Stievenard, M. Pierre, M. Masson-Delmotte, V. Other Hydroclimate Reconstruction Precipitation Reconstruction drought earth science/paleoclimate/climate reconstructions|tree ring (age,null,null,year Common Era,null,climate reconstructions|tree ring,null,null,N,null) earth science/paleoclimate/climate reconstructions|tree ring (standardized precipitation evapotranspiration index,delta 18O,null,dimensionless,Jun-Aug,climate reconstructions|tree ring,null,null,N,cellulose delta 18O) earth science/paleoclimate/tree ring (delta 18O,latewood cellulose,null,per mil VSMOW,null,tree ring,anomalized,isotope ratio mass spectrometry,N,anomalized from total record mean) earth science/paleoclimate/tree ring (delta 18O,cellulose,null,per mil VSMOW,null,tree ring,anomalized,null,N,null) earth science/paleoclimate/climate reconstructions|tree ring (standardized precipitation evapotranspiration index,null,95% confidence interval upper bound,dimensionless,Jun-Aug,climate reconstructions|tree ring,null,null,N,null) earth science/paleoclimate/tree ring (age,null,null,year Common Era,null,tree ring,null,null,N,null) earth science/paleoclimate/reconstructions (Fontainebleau>LATITUDE 48.45>LONGITUDE 2.68) (Angoulême>LATITUDE 45.7333>LONGITUDE .3) The reconstruction of droughts is essential for the understanding of past drought dynamics and can help evaluate future drought scenarios in a changing climate. This article presents a reconstruction of summer droughts in France based on annually resolved, absolutely dated chronologies of oxygen isotope ratios (δ18O) in tree ring cellulose from Quercus spp. Samples were taken from living trees and timber wood from historic buildings at two sites: Fontainebleau (48°23′ N, 2°40′ E; 1326–2000 CE) and Angoulême (45°44′ N, 0°18′ E; 1360–2004 CE). Cellulose δ18O from these sites proved to be a good proxy of summer climate, as the trees were sensitive to temperature and moisture availability. However, offsets in average δ18O values between tree cohorts necessitated a correction before joining them to the final chronologies. Using the corrected δ18O chronologies, we developed models based on linear regression to reconstruct drought, expressed by the standardized precipitation evapotranspiration index (SPEI). The significant correlations between the SPEI and cellulose δ18O (r ≈ −0.70), as well as the verification of the models by independent data support the validity of these reconstructions. At both sites, recent decades are characterized by increasing drought. Fontainebleau displays dominantly wetter conditions during earlier centuries, whereas the current drought intensity is not unprecedented in the Angoulême record. While the δ18O chronologies at the two studied sites are highly correlated during the 19th and 20th centuries, there is a significant decrease in the correlation coefficient between 1600 and 1800 CE, which indicates either a weaker climate sensitivity of the tree ring proxies during this period, or a more heterogeneous climate in the north and the south of France. Future studies of tree ring isotope networks might reveal if the seasonality and spatial patterns of past droughts can explain this decoupling. A regional drought reconstruction based on a combination of the two sites shows good agreement with historical records of grape harvest dates in France, which provide another proxy of summer climate. STUDY NOTES: Tree ring cellulose delta18O time series from Fontainebleau (FON) and Angouleme (ANG) and their average (mean), expressed as anomalies. The analytical error is 0.2 permil. Drought reconstructions for June-July-August based on these delta18O time series. Drought is expressed by the SPEI (Standardized Precipitation Evapotranspiration Index). IITRDB19 NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Labuhn, I. Investigator : Daux, V. Investigator : Girardclos, O. Investigator : Stievenard, M. Investigator : Pierre, M. Investigator : Masson-Delmotte, V. 2016-05-03 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/20002 https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/fontainebleau2016.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/ang-font2016.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/angouleme2016.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/fontainebleau2016.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/ang-font2016.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/angouleme2016.txt English https://www.ncdc.noaa.gov/paleo/study/20002 https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/fontainebleau2016.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/ang-font2016.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/france/angouleme2016.txt Inga Labuhn, Valérie Daux, Olivier Girardclos, Michel Stievenard, Monique Pierre, and Valérie Masson-Delmotte2016French summer droughts since 1326 CE: a reconstruction based on tree ring cellulose δ18OClimate of the Past121101-111710.5194/cp-12-1101-2016http://www.clim-past.net/12/1101/2016/ START YEAR: 1326 AD * END YEAR: 2004 AD .3 45.7333 2.68 48.45