Sea Ice Formation Rates Recorded in Planktonic Foraminiferal Oxygen and Carbon Isotopes in the Western Arctic Ocean during the Late Quaternary

An integrated study was carried out on stable isotopes of planktonic foraminifera Neogloboquadrina pachyderma(sin.)(Nps),planktonic foraminiferal abundance and ice-rafted detritus(IRD) in the western Arctic Ocean to investigate sea ice formation during the late Quaternary.Our results show that light excursions in Nps δ18O and δ13C happened seven times,likely indicating the production and sinking of isotopically light brines caused by enhanced rate of the sea ice formation.Because concomitant decrease occurred in planktonic foraminiferal abundance and IRD,these light Nps δ18O and δ13C values unlikely reflect inputs of freshwater and warm Atlantic waters.They more likely suggest reduction of Atlantic waters into the Arctic Ocean and substantial decrease of Chukchi Sea shelf waters.On the contrary,heavy δ18O values would indicate reduction of freshwater and Pacific waters into the Arctic Ocean and heavy δ13C values be caused by well ventilated surface and halocline waters transported from the shelf into the Arctic Ocean.