Amount dependency of monsoon rainfall δ18O on multiple time scales: observations from south western India
Paleoclimatic interpretation of stable isotope based proxies from India is complex due to lack of local amount effect (negative relation between rainfall and its heavy isotopic content observed over tropics) in most places. Recent studies revealed that regional or upstream rainfall/ convective activity plays a major role on daily rainfall δ18O variability. Here we extensively analyze the isotopic variability of Indian Summer Monsoon (ISM) rainfall of south western peninsular India. ISM rainfall δ18O of south western coast of India show significant correlation with the upstream convective activity and the associated rainfall over eastern Arabian Sea on daily, monthly and yearly time scales. A comparative dry–wet–dry (wet–dry–wet) rainfall pattern is observed over north eastern India, peninsular India and the equatorial Indian Ocean during the occurrence of low (high) values of rainfall δ18O at south western coast of India on all time scales. Thus the ISM rainfall δ18O of south western India captures not only the local or upstream convective activities, but reflects the rainfall pattern of a large domain including the Indian subcontinent and Indian Ocean. 18O variations of climatic proxies from south western coast of India can be thus better interpreted in terms of these results.
We thank M Smruthy, PV Ravisankar and TG Shylaja for help in collecting the samples. GPCP Precipitation data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their web site at http://www.esrl.noaa.gov/psd/. ISRO-GBP is acknowledged for funding.
- Adler, R. F., Huffman, G. J., Chang, A., Ferraro, R., Xie, P.-P., Janowiak, J., Nelkin, E. (2003). The version-2 global precipitation climatology project (GPCP) monthly precipitation analysis (1979–present). J Hydrometeorol. https://doi.org/10.1175/1525-7541(2003)004%3C1147:TVGPCP%3E2.0.CO;2 Google Scholar
- Dansgaard W (1964) Stable isotopes in precipitation. Tellus 16(4):436–468. https://doi.org/10.1111/j.2153-3490.1964.tb00181.x CrossRefGoogle Scholar
- Kaspari S, Mayewski P, Kang S, Sneed S, Hou S, Hooke R, … Ren J (2007) Reduction in northward incursions of the South Asian monsoon since ~ 1400 AD inferred from a Mt. Everest ice core. Geophys Res Lett 34(16). https://doi.org/10.1029/2007GL030440
- Liebmann B, Smith CA (1996) Description of a complete (interpolated) outgoing longwave radiation dataset. Bull Am Meteor Soc 77:1275–1277Google Scholar
- Managave SR, Sheshshayee MS, Borgaonkar HP, Ramesh R (2010) Intra-annual oxygen isotope variations in central Indian teak cellulose: possibility of improved resolution for past monsoon reconstruction. Curr Sci 98(7):20–25Google Scholar
- Ramesh R, Tiwari M, Chakraborty S, Managave S, Yadava MG, Sinha DK (2010) Retrieval of south asian monsoon variation during the holocene form natural climate archives. Curr Sci 99(12):1770–1786Google Scholar
- Soman MK, Krishna KK, Singh N (1988) Decreasing trend in the rainfall of Kerala. Curr Sci 57:7–12Google Scholar
- Yadava MG, Ramesh R, Pandarinath K (2007) A positive “amount effect” in the Sahayadri (Western Ghats) rainfall. Curr Sci 93:560–564Google Scholar