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Past 100 Ky surface salinity-gradient response in the eastern Arabian Sea to the summer monsoon variation recorded by delta super(18)O of G. sacculifer
| Content Provider | CSIR - National Institute of Oceanography (NIO) |
|---|---|
| Author | Chodankar, A. R. Banakar, V. K. Oba, T. |
| Abstract | Northward flowing coastal currents along the western margin of India during winter-spring advect low-salinity Bay of Bengal water in to the Eastern Arabian Sea producing a distinct low-salinity tongue, the strength of which is largely governed by the freshwater flux to the bay during summer monsoons. Utilizing the sedimentary records of delta sup(18) O sub(G. sacculifer), the past salinity-gradient within that low-salinity tongue is reconstructed, which serves as a proxy for the variation in freshwater flux to the Bay of Bengal and hence summer monsoon intensity. The north-south contrast in the sea level corrected (residual)-delta sup(18) O sub(G. sacculifer) can be interpreted as a measure of surface salinity-contrast between those two locations because the modern sea surface temperature and its past variation in the study region is nearly uniform. The core-top residual- delta sup(18) O sub(G. sacculifer) contrast of 0.45 ppt between the two cores is assumed to reflect the modern surface salinity difference of 1 psu and serves as a calibration for past variations. The residual delta sup(18) O sub(G. sacculifer) contrast varies between approx. 0.2 ppt at approx. 75 ky B.P. (i.e., late-Marine Isotope Stage 5) and approx. 0.7 ppt at approx. 20 ky B.P. (i.e., Last Glacial Maximum), suggesting that the overall salinity difference between the northern- and southern-end of the low-salinity tongue has varied between approx. 0.6 and approx. 1.6 psu. Considerably reduced difference during the former period than the modern suggests substantially intensified and northward-extended low-salinity tongue due to intense summer monsoons than today. On the other hand, larger difference (approx. 1.6 psu) during the latter period indicates that the low-salinity tongue was significantly weakened or withdrawn due to weaker summer monsoons. Thus, the salinity-gradient in the eastern Arabian Sea low-salinity tongue can be used to understand the past variations in the Indian summer monsoons |
| Starting Page | 135 |
| Ending Page | 142 |
| Page Count | 8 |
| File Format | |
| Journal | Global and planetary change |
| Volume Number | 47 |
| Language | English |
| Publisher | Elsevier |
| Access Restriction | Authorized |
| Subject Keyword | Palaeo studies Coastal currents Salinity gradients Oxygen isotopes Surface circulation Sea level changes Surface temperature Summer Monsoons forminifera Plankton |
| Content Type | Text |
| Resource Type | Article |
