Ice-rafted debris (IRD)-based sea-ice expansion events during the past 100 kyrs in the Okhotsk Sea

Ice-rafted debris (IRD) from sediment traps, surficial sediments, and sediment cores were investigated in order to reconstruct the extent history of sea-ice cover during the last 100 kyrs in the Okhotsk Sea. The seasonal IRD buried into the sediments, during and just after sea-ice melting in spring, consists of silt- and sand- size terrigenous particles. The spatial distribution of IRD within surficial sediments clearly corresponds to the extent of sea-ice coverage. Sea-ice expanded to a maximum extent during the glacial periods, although sea-ice cover was not perennial. The Okhotsk Sea Sea-ice Expansion (OSIE) events, which are recognized by millennial-scale-abrupt peaks of IRD content, have occurred 13 times during the past 100 kyrs. These events were amplified during the glacial periods. A significant modification of the polar atmospheric circulation in the northern hemisphere is a key process in explaining these OSIE events.