Assessing Mid-pleistocene to Holocene Sea-Ice Extent and Carbonate Compensation Depth Fluctuations in the Japan Sea: A Multiproxy Approach

Abstract

The extent and magnitude of sea-ice varied extensively since middle Pleistocene in northern Japan Sea affecting the climate, ecologic conditions and carbonate compensation depth (CCD) of the region. Sediment core samples of IODP site U1423 from north-eastern Japan Sea, have been quantitatively analyzed for angular and faceted surface Ice Rafted Debris (IRD), foraminifera and detrital fragments to reconstruct permanent sea-ice history, paleo-ecological conditions and CCD fluctuations in the Japan Sea. The enhanced cooling in the beginning of middle Pleistocene caused southward movement of sea-ice melting zone suggested by higher abundance of angular and faceted surface IRD between 880 to 450 ka. The site was above the CCD and melting of ice significantly cooled the surface water resulting in abundance of the low salinity and extremely low temperature tolerant species, Neogloboquadrina pachyderma (sinistral). The next phase of extreme cooling in the Japan Sea started after 450 ka, that shoaled the CCD; caused complete absence or decrease in calcareous planktic foraminifera species till 150 ka. The abundance of detrital material during this period suggests the presence of seasonal sea-ice linked with East Asian Winter Monsoon (EAWM) wind strength and Tsushima Warm Current (TWC) inflow into the Japan Sea. A significant decrease in the permanent and seasonal ice sheet and deepening of CCD was observed during last 150 ka. The IRD and foraminifera respond to 100 kyr variability, attributed to ice sheet dynamics and global ice volume changes.