Timing, cause and consequences of mid-Holocene climate transition in the Arabian Sea

We reconstruct centennial scale quantitative changes in surface seawater temperature (SST), evaporation precipitation (from Mg/Ca and delta O-18 of surface dwelling planlctic foraminifera), productivity (from relative abundance of Globigerina bulloides), carbon burial (from %CaCO3 and organic carbon [%C-org]) and dissolved oxygen at sediment water interface, covering the entire Holocene, from a core collected from the eastern Arabian Sea. From the multi-proxy record, we define the timing, consequences and possible causes of the mid -Holocene climate transition (MHCT). A distinct shift in evaporation-precipitation (E-P) is observed at 6.4 ka, accompanied by a net cooling of SST. The shift in SST and E-P is synchronous with a change in surface productivity. A concurrent decrease is also noted in both the planlctic foraminiferal abundance and coarse sediment fraction. A shift in carbon burial, as inferred from both the %CaCO3 and %C-org, coincides with a change in surface productivity. A simultaneous decrease in dissolved oxygen at the sediment water interface, suggests that changes affected both the surface and subsurface water. A similar concomitant change is also observed in other cores from the Arabian Sea as well as terrestrial records, suggesting a widespread regional MHCT. The MHCT coincides with decreasing low-latitude summer insolation, perturbations in total solar intensity and an increase in atmospheric CO2. (C) 2016 University of Washington. Published by Elsevier Inc. All rights reserved.