Indian summer monsoon variability during the holocene as recorded in sediments of the Arabian Sea: Timing and implications |
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| Authors: | Meloth Thamban Hodaka Kawahata Venigalla Purnachandra Rao |
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| Institution: | (1) National Centre for Antarctic and Ocean Research, Headland Sada, Goa, 403 804, India;(2) Geological Survey of Japan, AIST, Tsukuba, Ibaraki 305-8567, Japan;(3) National Institute of Oceanography, Dona Paula, Goa, 403 004, India;(4) Present address: Ocean Research Institute, University of Tokyo, Nakano-ku, Tokyo 164-8639, Japan |
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| Abstract: | Indian monsoon precipitation fluctuated significantly during the Holocene and a reliable reconstruction of the timing of the
events and their implications is of great benefit to our understanding of the effect and response of low latitude climate
systems to the forcing factors. We have carried out high-resolution terrigenous proxy studies on a laminated sediment core
from the Oxygen Minimum Zone of the eastern Arabian Sea margin to reconstruct the summer monsoon-controlled precipitation
changes during the Holocene. The temporal variation in the terrigenous proxy indicators of this core, in combination with
other high-quality cores from the Arabian Sea, suggests several abrupt events in monsoon precipitation throughout the Holocene.
The early Holocene monsoon intensification occurred in two abrupt steps at 9500 and 9100 years BP and weakened gradually thereafter,
starting at 8500 years BP. A weakening in precipitation recorded at ∼7000 years BP, synchronous with similar conditions in
India. One of the most significant weak monsoon periods recorded in our studies lies between 6000 and 5500 years BP. Spectral
analysis of the precipitation records reveals statistically significant periodicities at 2200, 1350, 950, 750, 470, 320, 220,
156, 126, 113, 104 and 92 years. Most of these millennial-to-centennial cycles exist in various monsoon records as well as
the tree ring Δ14C data and/or other solar proxy records. We suggest that throughout the Holocene, externally, small changes in solar activity
controlled the Indian monsoon to a large extent, whereas internally, non-solar causes could have influenced the amplitude
of decadal-to-centennial oscillations. |
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| Keywords: | Holocene Indian monsoon Arabian Sea climate variability solar forcing |
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