Special thanks

1. A465 EGU2011-3321 Climaticinterpretation of tree ring stable isotopes in the southeastTibetan Plateau : links withregionalcloudcover Chunming Shi1,2, Valérie Daux1, Valérie Masson-Delmotte1, Camille Risi3, Jing Gao4, Xiaochun Wang2 and Qi-Bin Zhang2 Contact : valerie.masson@lsce.ipsl.fr 1 IPSL/LSCE, CEA-CNRS-UVSQ, Gif-sur-Yvette, France 2 Institute of Botany, CAS, Beijing, China 3 U. Colorado, Boulder, USA 4 Tibetan Plateau Research Institute, CAS, Beijing, China Context : warming trend since the 1960s and importance of precipitationvariabilitylinkedwithmonsoon influence on SE Tibetan Plateau Goal: characterise the inter-annual to centennialvariability in the TP water cycle usingtree ring cellulose d18O Study site : Gangcun Natural Forest, nearBomi Climate: strongseasonality in precipitation (winterwesterlyevents and summermonsoon) and temperatureallowing the production of relativelywidetree rings • Conclusions and Perspectives • clear potential of tree ring stable isotopes in SE Tibet • multi-archive comparisons (e.g. ice cores) • new tree ring isotope records • site monitoring for an improved process based understanding • comparison with multi-centennial climate simulations including stable isotopes (e.g. impact of volcanic activity, regime shifts) • Tentative Cloud Cover reconstruction • (226 year long): • - recent increase is not unprecedented • lower variability in the 20thC than earlier • regime shift / abrupt decrease in the late 19thC • dry decade in the 1810s, possibly linked with the 1809 and Tambora volcanic eruptions (major famine in nearby Yunan) Species: Linzhi spruce (Picealikiangensis var. linzhiensis), the dominant sub-alpine evergreen conifer in southeast Tibet Sampling: 4 young trees (average age : 100 years, 4 cores per tree) and 27 old trees (average age : 215 years, 1 core per tree) Links withregionalcloudcover: R²=0.50 (after removal of one outlier) Mechanisms can involve monsoon dynamics (linking cloudiness and depletion), photosynthesis intermittency, tree water stress Precipitationisotopic composition : one year of event-based data at Bomi is available. Depleted values are obtained in summer-autumn. Modelling: models (LMDZiso and ECHAM4iso) capture some of the features of SE Tibet precipitation isotopic composition, esp. at high res. (50 km) Related publications Gao J., Masson-Delmotte V., Yao T., Tian L., Risi C. and Hoffmann G. (2010) Precipitation water stable isotopes in the south Tibetan Plateau: observations and modeling. J. Clim. doi: 10.1175/2010JCLI3736.1. Shi C., Masson-Delmotte V., Risi C., Eglin T., Stievenard M., Pierre M., Wang X., Gao J., Bréon F.-M., Zhang Q.-B. and Daux V. (2011) Sampling strategy and climatic implications of tree-ring stable isotopes in Southeast Tibetan Plateau. Earth Planet. Sc. Lett.301, 307-316. Shi C., Daux V., Zhang Q.B., Risi C., Hou S., Stievenard M., Pierre M., Li Z., Masson-Delmotte V., Reconstruction of southeast Tibetan Plateau summer cloud cover over the past two centuries using tree ring d18O. Submitted. Cellulose oxygen 18 simulation: ORCHIDEE-iso also depicts a strong link with relative humidity Climate simulation: Bomi summer precipitation isotopic composition is anti-correlated with regional cloud cover in LMDZiso Dispersion analysis: limited intra- and inter-tree variability, 4 trees allow to capture a population signal. No age effect. Calibration study: strong correlation with summer precipitation, relative humidity, regional cloud cover Special thanks This study would not have been possible without the financial support from GIS Environnement-Société and from the French Embassy in China, and without the technical support of Monique Pierre and Michel Stievenard