North Atlantic sea surface conditions during the Younger Dryas cold event

A map has been drawn of the oxygen isotopic composition (δ18O) of planktonic foraminifera which deposited their shells in isotopic equilibrium with ambient surface waters during the Younger Dryas cold event. These δ18O values were derived from the δ18O values of Neogloboquadrina pachyderma (left coiling) and Globigerina bulloides, which lived in their respective optimum temperature ranges. This map reflects the main trends of the sea surface temperature field during the Younger Dryas, but does not exhibit any δ18O anomaly associated with continental ice-sheet melting. This result rules out all the theories relating the Younger Dryas cooling to injection of continental ice-sheet meltwater with very low δ18O value into the North Atlantic Ocean. This reconstruction suggests that drifting of Arctic sea ice transported by the East Greenland Current may be a possible cause for the strong cooling which occurred in the middle of the last deglaciation.