Late Quaternary Climatic Changes in the Norwegian and Greenland Seas.

摘要

Analyses of total carbonate and coarse fraction content in 29 deep-sea cores and faunal analyses of plank-tonic foraminifera in 7 cores provide climatic data for the past 150,000 years. These data show that temperatures have been much colder than at present for most of the past 150,000 years in the Norwegian and Greenland Seas. Only during the Eemian interglacial did temperatures moderate to about present levels. Quantitative paleo-temperature estimates, derived by applying the Imbrie and Kipp technique to seven cores, show that except for the Eemian and Recent interglacials, temperatures less than 0C in winter and 5C in summer prevailed throughout the region. This temperature regime is identical to that of the northwestern Greenland Sea today, where sea-ice is present during the winters. For about 100,000 of the past 127,000 years, therefore, ice has probably covered most or all of the Norwegian and Greenland Seas, at least during the winters. The Norwegian Current, a branch of the Gulf Stream, is responsible for the relatively warm climate of Scandinavia at the same latitude where Greenland supports an ice cap. In addition, the Norwegian Current controls the present distributions of planktonic and benthonic foraminifera and the present extent of sea-ice cover. Based on faunal and sedimentary changes in the deep-sea cores, most of the past 150,000 years (at least) was characterized by a surface water circulation pattern in which the Norwegian Current was either much weaker or absent, thus allowing sea-ice formation throughout the region. The only exception to this observation occurs during the Eemian interglacial when conditions were comparable to those of the present.