THE EEM STABLE-ISOTOPE RECORD ALONG THE GRIP ICE CORE AND ITS INTERPRETATION

A 3029-m-long deep ice core extending nearly to bedrock has been drill ed at the very top of the Greenland ice sheet (Summit) by the Greenlan d Ice-core Project (GRIP), an international European joint effort orga nized by the European Science Foundation. The ice core reaches back to 250,000 yr B.P. according to dating based partly on stratigraphic met hods and partly on ice-flow modeling. A continuous and detailed stable isotope (delta(18)O) profile along the entire core depicts dramatic t emperature changes in Greenland through the last two glacial cycles, i ncluding abrupt climatic shifts during the Eem/Sangamon Interglaciatio n, which is elsewhere recorded as a warm and stable period. The strati graphic continuity of the Eemian layers has therefore been scrutinized . New ice core studies, comprising cloudy band observations, deconvolu tion, and frequency analyses, lead to the conclusion that the climate instability suggested during the Eem Interglaciation in Greenland is l ikely to be real, though no conclusive evidence is available. Whereas latitudinal displacements of the North Atlantic Ocean current are cons idered the immediate cause of the glacial climate instability, longitu dinal displacements may be the immediate cause of the Eemian instabili ty. If so, the Eemian climate changes will be much subdued outside the Arctic region and will probably only be recognizable in sedimentary s equences of high sensitivity and temporal resolution. (C) 1995 Univers ity of Washington.