A paleoclimatic evaluation of marine oxygen isotope stage 11 in the high-northern Atlantic (Nordic seas)

A sediment core from the high latitude of the Northern Atlantic (Nordic sea s) was intensively studied by means of biogeochemical, sedimentological, an d micropaleontological methods. The proxy records of interglacial marine ox ygen isotope stage (MIS) 11 are directly compared with records from the Hol ocene (MIS 1), revealing that many features of MIS Il are rather atypical f or an interglaciation at these latitudes. Full-interglacial conditions without deposition of ice-rafted debris existe d in MIS 11 for about 10 kyr (similar to 398-408 ka). This time is marked b y the lightest d18O values in benthic foraminifera, indicating a small glob al ice volume, and by the appearance of subpolar planktic foraminifera, ind icating a northward advection of Atlantic surface water. A comparison with MIS 1, using the same proxies, implies that surface temperatures were lower and global ice volume was larger during MIS Il. A comparative study of the ratio between planktic and benthic foraminifera also reveals strong differ ences among the two intervals. These data imply that the coupling between s urface and bottom bioproductivity, i.e., the vertical transportation of the amount of fresh organic matter, was different in MIS Il. This is corrobora ted by a benthic fauna in MIS Il, which contains no epifaunally-living spec ies. Despite comparable values in carbonate content (%), reflectance analys es of the total sediment (greylevel) show much higher values for MIS Ii tha n for MIS 1. These high values are attributed to increased corrosion of for aminiferal tests, directly affecting the sediment greylevel. The reason for this enhanced carbonate corrosion in MIS ii remains speculative, but may b e linked to the global carbon cycle. (C) 2000 Elsevier Science B.V. All rig hts reserved.