Records of bulk carbonate content, ice-rafted detritus (IRD), planktonic foraminifers, and coccolithophores of Ocean Drilling Program Site 982 from the Rockall Plateau and Site 985 from the Norwegian Sea are compared to determine the variability of the south-north gradients in surface water since ~3.1 Ma.The onset of the major Northern Hemisphere glaciation appears time-transgressively between the sites, as indicated by both a noticeable increase in IRD and marked decrease in carbonate. Thus, each site is recording a somewhat different manifestation of the larger processes that occurred in the interval 2.8 to ~1.1 Ma. Although the interval since ~2.5 Ma was a climatically unstable time interval in the North Atlantic, sedimentation is largely composed of calcareous biogenics at Site 982. Minimum carbonate contents, however, result primarily from dilution by IRD during glacials. In contrast, at Site 985 glacial conditions, probably with discontinuous sea-ice cover, dominated throughout until 1.1 Ma as shown by the nearly carbonate-free sediments. Thus, during most of this time interval the North Atlantic surface water did not enter the Norwegian Sea. Nevertheless, increased carbonate contents and relatively abundant coccoliths indicate increasingly northward penetrations of comparatively warm Atlantic water into the Norwegian Sea during short phases at ~1.9 and 1.4 Ma.The gradient between the North Atlantic and the Norwegian Sea became less distinct after ~1.1 Ma and even less pronounced after 0.65 Ma. Short but warm interglacials with relatively high biogenic carbonate accumulation occurred in the Norwegian Sea, alternating with longer glacial-dominated intervals with high inputs of IRD. However, glacial-interglacial contrast was subdued in the Norwegian Sea as opposed to the North Atlantic. Thus, a pronounced increase in the meridional circulation of the northern North Atlantic is inferred for the Brunhes Chron.

Supplement to: Baumann, Karl-Heinz; Huber, Robert (1999): Sea-surface gradients between the North Atlantic and the Norwegian Sea during the last 3.1 m.y.: comparison of Sites 982 and 985. In: Raymo, M.E.; Jansen, E.; Blum, P.; Herbert, T.D. (eds.), Proceedings of the Ocean Drilling Program, 162 Scientific Results, Proceedings of the Ocean Drilling Program, 162, Ocean Drilling Program, Proceedings of the Ocean Drilling Program Scientific Results, 162, 179-190