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Monsoon‐induced sea surface temperature changes recorded in Indian corals
Author(s) -
Chakraborty S.,
Ramesh R.
Publication year - 1993
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.1993.tb00303.x
Subject(s) - porites , oceanography , coral , sea surface temperature , geology , monsoon
The South Asian Summer Monsoon induces vertical mixing in the surface Arabian Sea, leading to a reduction in the Sea Surface Temperature (SST) of the order of 3–4°C. This reduction in temperature is recorded by modern corals (Porites) that grow in the Lakshadweep Islands (coralline islands located at about 350 km off the south‐west coast of India) in their stable oxygen isotope ratios (denoted by δ 18 O). As large coral colonies of this genus are available, our results show that palaeomonsoon records for a few centuries back in time, a crucial input for climatic models aimed at predicting the Asian Monsoon, can be obtained from these corals. We also show that two corals separated by ˜ 60 km show similar (518O variations as does a giant clam (Tridacna maximus) that grew near one end of the coral colonies. As this clam is known to precipitate CaCO3 in isotopic equilibrium with the ambient sea‐water, it is possible to estimate the isotopic offset of coralline δ 18 O from that of the CaCO3 precipitated in isotopic equilibrium. This ‘disequilibrium effect’ appears to be constant around 4.5±0.2%0. Our calculations show that SST (t, °C) is related to the coral δ 18 O (δ c ) and the sea‐water δ 18 O (δ w ) by the equation t = 3.0–4.68 (δ c ‐ δ w ), which is in good agreement with such relationships for corals from the Pacific and Atlantic.