What can be learnt from oxygen isotopes composition of teak tree rings from India? Rainfall reconstruction up to AD 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

Teak (Tectona grandis)

 Chhattisgarh I  Chhattisgarh II  Kerala 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)

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

Rationale behind the data interpretation

Amount effect and passage of water in plant  18 O rain Amount of rainfall 1Precipitation

H2OH2O CO 2 Importance of relative humidity Relatively 16 O enriched Relatively 18 O enriched 6CO 2 + 6H 2 O + sunlight = C 6 H 12 O 6 + 6O 2

Results from intra-ring studies Results from inter-ring studies

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

Intra-ring  18 O analysis of teak sample from central India Coarse resolution studies High resolution studies June to Sept Oct-Dec Pith side Bark side 4mm time Sample location: Jagdalpur Managave et al., GRL 2010

Relative humidity controls intra-annual  18 O variations Managave et al., GRL 2010

Break monsoons and intra-ring  18 O variations 3 to 17 days (average 5.8 days) (Ramamurthy, 1969) Goswami and Mohan, 2001; Gadgil and Joseph 2003

Break monsoons and relative humidity RainfallRelative humidity (Krishnamurthy and Biswas, 2006) Break monsoon over central India

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

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

Intra-annual  18 O variations Location: Perambikulum, south India June to SeptOct-Dec Location: Jagadalpur, central India June to SeptOct-Dec Managave et al., Clim dyn 2011

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

Modeled climatological  18 O profiles for Palakkad area  Trees from southern India samples both the SW (Jun-Sept) and NE (Oct-Dec) monsoons   18 O of whole ring is likely affected by (NE/SW) ratio Monthly weather data Palakkad (Rainfall, RH) ( ); & Kozhikode (  18 O) ( ) Climatological intra-ring  18 O profiles Managave et al., Clim dyn 2011

Significance of plants having signature of both the monsoons Spatial distribution of (  18 O summer –  18 O winter ) rainfall Araguas-Araguas et al., 1998

Summary of intra-ring studies  Teak from central India:  Relative humidity decides intra-ring  18 O 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  18 O variations

Results from inter-ring studies a)Tree from Jagadalpur, central India b)Tree from Perambikulum, southern India

Location: Jagadalpur, central India Sub-divisional rainfall  18 O (r = 0.5, P<0.005) Positive correlation between rainfall &  18 O Managave et al., Dendrochronologia, 2011

Why positive correlation between cell.  18 O and rainfall? Leaf area index Leaf area index Soil moisture Yoshifuji et al., 2003 data

Higher the length of growing season, more positive  18 O values Relative humidity conditions during monsoon and post-monsoon season Lower  18 O Higher  18 O

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

Location: Perambikulum Kerala Negative correlation between rainfall &  18 O r = −0.5, p<0.005 Managave et al., Dndrochronologia, 2011

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

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

Thank you

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

Observed and modeled Intra-ring  18 O variations  Models can be used to interpret intra-ring  18 O variations  Resolution of main- and post-monsoon season can be achieved  Possibility of achieving ~20 days of time resolution Jagdalpur sample Observed Ring = 1971 Modeled Daily weather, 1971,Jagadalpur Under review: Current Science

No amount effect By and large positive correlation between rainfall &  18 O (r = 0.4, P<0.005) % rainfall departure anomaly  18 O Location: Thane, western India Under review: Dendrochronologia