Downcore analyses of variations in planktonic and benthic foraminiferal distribution, sedimentology and stable isotopes in cores from the deep ocean basin and the continental slope of the southeastern Norwegian Sea show that the last glacial to postglacial transition occurred in two distinct steps. Prior to
13,000 BP the area was characterized by a year-round iceberg and pack-ice environment, low surface productivity and homogenous, low productivity deep water conditions. After ca. 13,000 BP the ocean became seasonally ice free with high productivity and low-scale vertical circulation. The surface remained
cold until after 10,000 BP, in contrast to the warm North Atlantic during the period 13,000-11,000 BP. In this period benthic foraminifera indicate presence of stratified deep-waters dissimilar to the present. Two possible patterns of deep water exchange are presented. During the Younger Dryas chronozone the
Norwegian Sea remained open. Constant, strong bottom currents were introduced on the upper continental slope, and large scale bottom water formation and overflows to the North Atlantic possibly started during the Y. Dryas. The final warming of the Norwegian Sea started around 10,000 BP as a rapid introduction of warm, temperate surface water in the eastern part, while the warming of central and western parts occurred in the early Holocene.