What can be learnt from oxygen isotopes composition of teak tree rings from India?

1. What can be learnt from oxygen isotopes composition of teak tree rings from India? Rainfall reconstruction up to AD 1743. Shreyas R. Managave Department of Earth Sciences Pondicherry University, India Collaborators Prof. R. Ramesh, Physical Research Laboratory, Ahmedabad, India Dr. H. P. Borgaonkar, Indian Institute of Tropical Meteorology, Pune, India Dr. A. Bhattacharyya, Birbal Sahani Institute of Palaeobotany, Lucknow, India

2. Teak (Tectona grandis)

3. Jagadalpur Hanamkonda Perambikulum Sample Locations (1532 mm; 82 days, NE/SW=0.11) (940 mm, 53 days, NE/SW=0.17) (2163 mm, 102 days, NE/SW=0.27) • Chhattisgarh I • Chhattisgarh II • Kerala

4. Objectives • To understand what governs isotopic composition of teak growing in different meteorological settings in India • To check whether trees growing in the southern part of India show isotopic signature of SW and NE monsoons • Reconstruction of high resolution past monsoon rainfall

5. Rationale behind the data interpretation

6. Precipitation 1 d18Orain Amount of rainfall Amount effect and passage of water in plant

7. 18 16 16 16 16 Relatively 16O enriched 16 Relatively18O enriched Importance of relative humidity H2O CO2 6CO2 + 6H2O + sunlight = C6H12O6 + 6O2

8. Results from intra-ring studies Results from inter-ring studies

9. Pith side Bark side 1 2 3 4 5 6 7 8 time Results from intra-ring studies 1 ~ Early growing season (May) 2-6 ~ Main growing season (June-Sept) 7-8 ~ Late growing season (Oct-Dec) Tree from central India & southern India

10. Intra-ring d18O analysis of teak sample from central India Coarse resolution studies High resolution studies June to Sept Oct-Dec June to Sept Oct-Dec Sample location: Jagdalpur Bark side Pith side 4mm Managave et al., GRL 2010 time

11. Managave et al., GRL 2010

12. Relative humidity controls intra-annual d18O variations Managave et al., GRL 2010

13. Break monsoons and intra-ring d18O variations 3 to 17 days (average 5.8 days) (Ramamurthy, 1969) Goswami and Mohan, 2001; Gadgil and Joseph 2003

14. Break monsoons and relative humidity Break monsoon over central India Rainfall Relative humidity (Krishnamurthy and Biswas, 2006)

15. Year with active monsoon (1st Aug to 31st Sept 1971 A.D.) Year with break-monsoon (19th July to 3rd Aug 1972 A.D.) Break monsoons and relative humidity Managave et al., GRL 2010

16. Intra-annual carbon and oxygen isotopic composition of teak Location: Jagadalpur, Chattisgarh Positive correlation indicates control of relative humidity

17. June to Sept Oct-Dec June to Sept Oct-Dec Location: Perambikulum, south India Intra-annual d18O variations Location: Jagadalpur, central India Managave et al., Clim dyn 2011

18. Winter (NE) monsoon rain is depleted in 18O Location: Kozhikode GNIP data

19. Modeled climatological d18O profiles for Palakkad area Climatological intra-ring d18O profiles Monthly weather data Palakkad (Rainfall, RH) (1950-1980); & Kozhikode (d18O) (1996-2001) • Trees from southern India samples both the SW (Jun-Sept) and NE (Oct-Dec) monsoons • d18O of whole ring is likely affected by (NE/SW) ratio Managave et al., Clim dyn 2011

20. Significance of plants having signature of both the monsoons Spatial distribution of (d18Osummer – d18Owinter) rainfall Araguas-Araguas et al., 1998

21. Summary of intra-ring studies • Teak from central India: • Relative humidity decides intra-ring d18O variations • Time resolution: pre-, main- and post-monsoon • Possibility of detecting major break-monsoons • Teak from southern India: • Winter monsoon signature is preserved • Possibility of reconstructed both the monsoons using intra-ring studies • Care should be taken while interpreting annual d18O variations

22. Results from inter-ring studies • Tree from Jagadalpur, central India • Tree from Perambikulum, southern India

23. d18O Sub-divisional rainfall (r = 0.5, P<0.005) Location: Jagadalpur, central India Positive correlation between rainfall & d18O Managave et al., Dendrochronologia, 2011

24. Why positive correlation between cell. d18O and rainfall? Soil moisture Leaf area index Soil moisture Leaf area index Yoshifuji et al., 2003 data

25. Relative humidity conditions during monsoon and post-monsoon season Lower d18O Higher d18O Higher the length of growing season, more positive d18O values

26. 5-yr running mean Comparison between two trees from Jagadalpur r=0.5 P<0.005 r=0.7 P<0.005 Location: Jagadalpur, Chattisgarh Managave et al., Dndrochronologia, 2011

27. Location: Perambikulum Kerala r = −0.5, p<0.005 Negative correlation between rainfall & d18O Managave et al., Dndrochronologia, 2011

28. Temporally varying strength of correlation Managave et al., Dndrochronologia, 2011

29. Comparison with regional rainfall record Extended local and regional rainfall record by 128 and 70 years, respectively Higher rainfall during the later part of the Little Ice Age Managave et al., Dndrochronologia, 2011

30. Thank you

31. Other evidences of higher rainfall Borgaonkar et al., 2007 Bhattacharyya et al., 2007

33. Observed and modeled Intra-ring d18O variations Jagdalpur sample Observed Ring = 1971 Modeled Daily weather, 1971,Jagadalpur • Models can be used to interpret intra-ring d18O variations • Resolution of main- and post-monsoon season can be achieved • Possibility of achieving ~20 days of time resolution Under review: Current Science

34. Location: Thane, western India % rainfall departure anomaly d18O No amount effect By and large positive correlation between rainfall & d18O (r = 0.4, P<0.005) Under review: Dendrochronologia