Ocean circulation in the Norwegian sea during the last deglaciation: Isotopic evidence

Abstract

Three cores from different depths in the southeastern Norwegian Sea have been investigated for benthic and planktonic foraminiferal stable isotope records. The cores confirm that the last deglaciation occurred in two distinct steps. The first step, Termination Ia, may have occurred at about 13,000 yr B.P., while the second step took place shortly after 10,000 yr B.P. The benthic oxygen isotopes reveal strong influence of deglacial intermediate waters possibly flowing in from the North Atlantic, with a maximum influence at about 12,000 yr B.P. Both carbon and oxygen isotopic records show that bottom water formation in the Norwegian Sea was reinitiated after 12,000 yr B.P. During the first part of the deglaciation, the deep-water circulation pattern may have been opposite to that of the present. The oxygen content in the Norwegian Sea deep water was low during the last glacial maximum, and remained low during the first part of the deglaciation due to low vertical circulation rates. The large variations in deep water circulation in the Norwegian Sea during the last deglaciation may have had important consequences for the interchange of CO 2 between ocean and atmosphere.