SST time-series for Eastern Arabian Sea recostructed from paired measurement of δ¹⁸O and Mg/Ca of planktonic foraminifera

The deglacial transition from the last glacial maximum at ∼20 kiloyears before present (ka) to the Holocene (11.7 ka to Present) was interrupted by millennial-scale cold reversals, viz., Antarctic Cold Reversal (∼14.5–12.8 ka) and Greenland Younger Dryas (∼12.8–11.8 ka) which had different timings and extent of cooling in each hemisphere. The cause of this synchronously initiated, but different hemispheric cooling during these cold reversals (Antarctic Cold Reversal ∼3∘C and Younger Dryas ∼10∘C) is elusive because CO2, the fundamental forcing for deglaciation, and Atlantic meridional overturning circulation, the driver of antiphased bipolar climate response, both fail to explain this asymmetry. We use centennial-resolution records of the local surface water 18O of the Eastern Arabian Sea, which constitutes a proxy for the precipitation associated with the Indian Summer Monsoon, and other tropical precipitation records to deduce the role of tropical forcing in the polar cold reversals. We hypothesize a mechanism for tropical forcing, via the Indian Summer Monsoons, of the polar cold reversals by migration of the Inter-Tropical Convergence Zone and the associated cross-equatorial heat transport