Paleoceanographic records in the Chukchi Basin, western Arctic Ocean during the late Quaternary

P736; The late Quaternary paleoceanographic changes in the western Arctic Ocean are revealed by quantitative studies of foraminifcral abundance,ice-rafted detritus (IRD) and its mineralogical and petrological compositions,planktonic Neogloboquadrina pachyderma (sin.) (Nps)-δ18O and -δ13C,biogenic and non-biogenic components in Core M03 token from the Chukchi Basin during the Second Chinese National Arctic Expedition cruise.Seven IRD events appeared at MIS 7,5,3 and 1.These IRD were carried in massive icebergs,which were exported to the Beaufort Sea through the M'Clure Strait Ice Stream,Canadian Arctic Archipelago,and then transported into the Chukchi Basin by the Beaufort Gyre.Low IRD deposition occurred during the glacial times when more extended ice cover and weakened Beaufort Gyre,while the open water condition and the intensified Beaufort Gyre during interglacial periods favored the IRD deposition.Therefore,the IRD events not only indicate the provenance of coarser detritus and ice export events,but also reflect the evolutionary histories of the Beaufort Gyre and North American ice sheet.Seven light Nps-δ18O and -δ13C excursions could respond to enhanced rates of sea ice formation resulting in the production and sinking of isotopically light brines,but was irrelevant to the warm Atlantic water and freshwater inputs.Whereas,the heavy Nps-δ18O and -δ13C values separately reflect the lessened Arctic freshwater and Pacific water,and well-ventilated surface water from the continental shelf and halocline water.Variations of CaCO3 content and planktonic foraminiferal abundance during the interglacial and glacial periods can demonstrate the incremental or diminishing input of the Atlantic water,while the total organic carbon (TOC) and opal contents increased and decreased during the glacial and interglacial periods,respectively,which could be related to the TOC degradation,opal dissolution and redox conditions of interface between the bottom water and sediments.