Deep ocean circulation has been considered relatively stable during interglacial periods, yet little is known about its behavior on submillennial time scales. Using a subcentennially resolved epibenthic foraminiferal d13C record we show that North Atlantic Deep Water (NADW) influence was strong at the onset of the last interglacial period and then interrupted by several prominent, centennial-scale reductions. These NADW transients occurred during periods of increased ice rafting and southward expansions of polar water influence, suggesting that a buoyancy threshold for convective instability was triggered by freshwater and circum-Arctic cryosphere changes. The deep Atlantic chemical changes were similar in magnitude to those associated with glaciations, implying that the canonical view of a relatively stable interglacial circulation may not hold for conditions warmer/fresher than at present.

Supplement to: Galaasen, Eirik Vinje; Ninnemann, Ulysses S; Irvalı, Nil; Kleiven, Helga F; Rosenthal, Yair; Kissel, Catherine; Hodell, David A (2014): Rapid Reductions in North Atlantic Deep Water During the Peak of the Last Interglacial Period. Science, 343(6175), 1129-1132