Coupling of thermocline depth and strength of the Indian, summer monsoon during deglaciation

We investigated the variations in thermocline depth using the difference in δ 18 Oc values between the two species of planktonic foraminifera, surface dwelling Globigerinoides ruber (s.s.) and thermocline dwelling Neogloboqudrina dutertrei , covering a time span of 9–23 kyr from the sediment core SK218/1 from the western Bay of Bengal (BoB). Here we show that during the strong phase of the Indian summer monsoon (12–9 kyr), a strong stratification leads to a shallow mixed layer and thermocline depth in the BoB as evident from higher Δ δ 18 O between the mixed layer and thermocline dwelling planktonic foraminifera species. Thus, a strong coupling between the Indian summer monsoon and thermocline depth in the BoB prevailed at a millennial time scale.