Late PLiocene dIAtom productivity in the western Bay of Bengal: Response to Indian MOnsoon evolution and teleconnections
Final Report Abstract
The late Pliocene (4.0-2.3Ma) saw a long-term weakening of Indian Summer Monsoon precipitation/runoff and simultaneous Bay of Bengal productivity increase, suggesting that the conditions ~3-2.7 Ma were some of the most favourable for sustained BoB productivity. The relationship between runoff and productivity at Site U1445 suggests that weakened rainfall and runoff in the Bay of Bengal diminished the stratification and increased nutrient availability in the photic zone, leading to enhanced productivity. U1445 productivity switches from stronger obliquity pre-2.8 Ma to stronger precession post-2.8 Ma. This is concurrent with a similar low latitude to high latitude Southern Hemisphere sea surface temperature gradient frequency switch, suggesting that BoB productivity is influenced by SH processes as well as local monsoon wind and runoff in the late Pliocene and early Pleistocene (2.4-3.32 Ma). A comparison with global records shows a shift in siliceous productivity ~2.5-3 Ma, where higher latitude productivity decreases while that in the lower latitudes increases, likely due to enhanced nutrient leakage from high to low latitudes during the Northern Hemisphere Glaciation. The U1445 productivity record, however, does not display the same sudden productivity surge as Atlantic and Pacific low latitude records, but increase gradually from ~3.6 Ma, as a result of ISM wind strengthening, and weak runoff.
