Buried iceberg scours reveal reduced North Atlantic Current during the stage 12 deglacial.

Reconstructing past ocean-climate environments and heat transport requires proxies from which these conditions can be quantified. This is particularly important for the evaluation of numerical palaeoclimate models. Here we present new evidence for a reduced North Atlantic Current (NAC) at the termination of the third last glacial, for which palaeocurrent information was previously unavailable. This is based on an exquisitely preserved set of buried iceberg scours seen in three-dimensional seismic reflection images from the mid-Norwegian slope. The scours were formed ∼430 ka during the transition from glacial to interglacial conditions. The spiral geometry of the scours suggests that they were carved by grounded icebergs influenced by tidal and geostrophic ocean currents. Using the ratio between the estimated tidal and geostrophic current velocities and comparing them with velocities from the Last Glacial Maximum and the present, we show that the stage 12 NAC velocities may have been ∼50% slower than the present.