Surface and deep water changes in the subpolar North Atlantic during Termination II and the last interglaciation

To reconstruct the history of water mass exchange between the NE Atlantic and the Nordic seas, sediment cores from similar to 2 km water depth were studied across Termination II (TII) and through the last interglaciation (MIS5e). During early TII the sudden appearance of the low-latitude planktonic foraminifera Beella megastoma is noted in both regions along with a steep decrease in benthic foraminiferal delta(18)O. Since other proxies indicate that surface waters were cold and stratified because of meltwater, conditions which prevented near-surface thermohaline circulation and vertical convection in the Nordic seas, water mass exchange between the two areas occurred at the subsurface. During later TII, surface conditions changed, and this subsurface circulation style was eventually replaced by vertical convection. In the Nordic seas, B. megastoma vanished from the record together with ice-rafted debris (IRD) at the end of TII, while subpolar foraminiferal abundance rose. Peak interglacial conditions with intensive vertical convection now fully developed, generating a bottom water temperature gradient of similar to 4 degrees C between the two areas. However, surface water temperatures deteriorated in the Nordic seas already notably before IRD recurred, and delta(18)O increased at the end of MIS5e.