Influence of the Indian Ocean Dipole on tree-ring δ18O of monsoonal Southeast Tibet
We present a newly developed, annually resolved tree-ring cellulose δ18O chronology for the southeastern Tibetan Plateau (TP) from Sikkim larch (Larix griffithii), spanning between 1684 and 2012. Comparisons with local and regional climate data reveal strong positive correlations with monthly sunshine hours, temperature and daily temperature amplitude as well as strong negative correlations with relative humidity, vapor pressure, rain days per month and cloud cover of August. Relationships with local and regional tree-ring δ18O chronologies are stable and highly significant. Over the 20th century, we find no long-term climatic trends. This is consistent with other tree-ring δ18O chronologies of other tree species south of the Himalayas, but contrasts with results from isotope studies north of the Himalayas. This suggests stable macroclimatic flow patterns throughout the last centuries for the southern tree stands. In terms of large-scale climate dynamics, we find evidence of a significant 30-year wave influencing our tree-ring oxygen chronology, most probably induced by the Indian Ocean Dipole and influencing tree-ring oxygen isotope chronologies along the southeastern Himalaya and the southeastern rim of the TP. This pattern is spatially and temporarily consistent among the chronologies and has apparently strengthened during the last century. During periods of strong positive dipole mode activity, the dipole mode index shows positive correlations with the δ18O of tree-rings on the southeastern TP.
KeywordsTibetan Plateau Indian Ocean Dipole Diurnal Temperature Range Indian Ocean Dipole Event Empirical Orthogonal Function
The authors are indebted to the German Research Foundation (DFG BR 1895/21-1) for funding. We thank Dr. Fan Zexin for contributing climate data, and Dr. Masaki Sano and Dr. Qi-Bin Zhang for providing their δ18O series.
- Cook E, Kairiūkštis L (2010, 1989) Methods of dendrochronology: Applications in the environmental sciences. Kluwer Academic Publishers, Dordrecht, NetherlandsGoogle Scholar
- Holmes RL (1983) Computer -assisted quality control in tree -ring dating and measurement. Tree-Ring Bull 43:69–78Google Scholar
- Kahmen A, Sachse D, Arndt SK, Tu KP, Farrington H, Vitousek PM, Dawsona TE (2011) Cellulose δ18O is an index of leaf-to-air vapor pressure difference (VPD) in tropical plants. PNAS 108(5):1981--1986Google Scholar
- Parthasarathy B., Munot A.A., Kothawale D.R. (1995) Monthly and seasonal rainfall series for all-India homogeneous regions and meteorological subdivisions: 1871–1994. Research Report, RR-065. Indian Institute of Tropical Meteorology, PuneGoogle Scholar
- Qiu Y, Cai W, Guo X, Ng B (2014) The asymmetric influence of the positive and negative IOD events on China's rainfall. Sci Rep 4:4943Google Scholar
- R Core team (2012) R: A language and environment for statistical computing. R Foundation for Statistical Computing, WienGoogle Scholar
- Rahim K (2014) Applications of multitaper Spectral analysis to Nonstationary data. Queen's University, ThesisGoogle Scholar
- Rinn F (2003) TSAP-Win Professional: time series analysis and Presentation for dendrochronology and related Applications. RINNTECH, HeidelbergGoogle Scholar
- Roden JS (2005) Carbon and oxygen isotope ratios of tree ring cellulose along a precipitation transect in Oregon, United States. J Geophys Res 110(G2)Google Scholar
- Roesch A, Schmidbauer H (2014) WaveletComp: computational wavelet analysis: R package version 1.0 http://CRAN.R-project.org/package=WaveletComp. Accessed 17 Feb 2016
- Saji NH, Goswami BN, Vinayachandran PN, Yamagata T (1999) A dipole mode in the tropical Indian Ocean. Nature 401(6751):360–363Google Scholar