High Resolution Southwest Monsoon Reconstruction for the Past ~2,800 Years: Wind Versus Precipitation
The wind-induced, upwelling-related productivity records from the western Arabian Sea have been used to reconstruct past variations in the Southwest (SW) monsoon wind strength. In contrast, the eastern Arabian Sea stores precipitation signal as it receives abundant freshwater, either as overhead precipitation or as surface runoff from the adjacent Western Ghats during the SW monsoon. A sediment core, SK 145-9 (12.6°N, 74.3°E; water depth 400 m, analyzed AMS dated length 50 cm-spanning past ~2,800 years) from the eastern Arabian Sea, was analyzed with high-resolution (sub-centennial) for δ18O and δ13C variations in three different species of planktic foraminifera (Globigerinoides ruber, Globigerinoides sacculifer and Globorotalia menardii) that documents past precipitation changes. Periods of aridity were observed at ~2,000, 1,500, 1,100, 850 and 500 cal yr BP (calibrated ages) in the eastern Arabian Sea, which were matched with data from western Arabian Sea depicting wind intensity. The wind strength exhibits good correlation with the precipitation intensity; reduced precipitation is accompanied by weakened winds, thus providing the paleoclimatic evidence for the control exhibited by SW monsoon precipitation over the wind strength via latent heat release.
KeywordsBefore Present Wind Strength Planktic Foraminifera Accelerator Mass Spectrometer Globigerinoides Ruber
MT thanks ISRO-GBP for funding and Sri Rasik Ravindra, Director-NCAOR for support; this is NCAOR Contribution no. 015/2011.
- Bé AWH (1977) An ecological, zoogeographic and taxonomic review of recent planktonic foraminifera. In: Ramsey ATS (ed) Oceanic micropaleontology. Academic, London, p 100Google Scholar
- Bhattathiri PMA, Pant A, Sawant S, Gauns M, Matondakar SGP, Mohanraju R (1996) Phytoplankton production and chlorophyll distribution in the eastern and central Arabian Sea in 1994–1995. Curr Sci 71(11):857–862Google Scholar
- Govil P, Naidu PD (2010) Evaporation-precipitation changes in the eastern Arabian Sea for the last 68 ka: implications on monsoon variability. Paleoceanography 25. doi: 10.1029/2008PA001687
- Shetye SR (1984) Seasonal variability of the temperature field off the southwest coast of India. Proc Indian Acad Sci 93(4):399–411Google Scholar
- Southon J, Kashgarian M, Fontugne M, Metivier B, Wyss Yim W-S (2002) Marine reservoir corrections for the Indian Ocean and Southeast Asia. Radiocarbon 44:167–180Google Scholar
- Stuiver M, Reimer PJ, Bard E, Beck JW, Burr GS, Hughen KA, Kromer B, McCormac G, van der Plicht J, Spurk M (1998) INTCAL98 radiocarbon age calibration, 24,000–0 cal BP. Radiocarbon 40:1041–1083Google Scholar