Paleoclimatology and paleo-oceanography of the Norwegian and Greenland Seas: The last 450,000 years

Abstract

Planktonic foraminiferal assemblages in Norwegian Sea sediments show that during the past 450,000 years a glacial regime, characterized by permanent sea-ice cover and the absence of the Norwegian Current, prevailed in the Norwegian Sea. These extremely cold conditions were interrupted by short, quasi-periodic (period of about 100,000 years) incursions of water warm enough to reduce sea-ice cover on a seasonal basis. Only the two most recent incursions were of sufficient intensity to bring relatively warm Norwegian Current waters into the region and thus justify here the name “interglacial”: the last interglacial (about 120,000 B.P.) and the Holocene. The absence of the Norwegian Current from the Norwegian Sea for all but about 20,000 of the last 450,000 years has had two important effects. First, a major source of heat for the Scandinavian land mass was not present except during the Holocene and the last interglacial. Thus, Scandinavia probably enjoyed a climate much like, or more severe than, that of Spitsbergen for most of the last 450,000 years. Large ice sheets were probably the rule rather than the exception. Second, the source of saline water for the formation of North Atlantic Deep Water was not present. This fact, together with the prevailing ice cover, prevented formation of a deep-water mass, except during the Holocene and the last interglacial. Deep water in the North Atlantic for all the remainder of the last 450,000 years must have formed elsewhere and by another mechanism. The prevailing ice-covered condition of the Norwegian Sea rules out the possibility of an open surface-water connection between the Arctic and North Atlantic oceans for all of the last 450,000 years. This is further evidence that the Ewing-Donn theory of an ice-free Arctic Ocean is incorrect. Of all the Pleistocene interglacial events recognized in temperate and low latitudes, only the last interglacial (Eemian) and the Holocene were intense enough to transport warm water into the Norwegian Sea and melt large amounts of sea ice. Future theories to explain climatic change must account for these anomalously warm interglacials as well as the extremely cold average conditions of the Norwegian Sea.